background statement for semi draft...

Background Statement for SEMI Draft Document 5110Revisions to SEMI S3-0306, Safety Guidelines for Process Liquid Heating Systems and Delayed Revisions to SEMI S2-0310, Environmental, Health, and Safety Guideline for Semiconductor Manufacturing EquipmentNOTICE: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this document.

NOTICE: Recipients of this document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, “patented technology” is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided.

BackgroundThis ballot addresses concerns identified during the reapproval ballot process for SEMI S3. The first two Line Items propose changes to SEMI S3. The third Line Item proposes changes to SEMI S2 to align it with the current SEMI S3.

Each part of each Line Item is surrounded by a box. Material proposed to be deleted is struck through. Material proposed to be added is underlined.

Line Item 1: Miscellaneous small clarifications and corrections to SEMI S3:Part A: Paragraph 3.7: Expand the abbreviation “AIT” and clarify intended temperature.Part B: Paragraph 4.4: Insert a space between “EN” and “1127”.Part C: Paragraph 5.1.7: Place “HTF” in italics.

Line Item 2: SEMI S3, Table 3: Removal of ambiguity in parsing of the formula for maximum set point for “flammable” liquids. The choice of possible meaning was based on the recollection of a member of the task force that prepared the current S3.

Line Item 3: Line Item changes, as Delayed Revisions effective July 2012, to SEMI S2 related to Process Liquid Heating. These changes are intended to align SEMI S2 with the current SEMI S3. (The current SEMI S2 is aligned with the versions of S3 prior to 0306.):Part A: Change Paragraph 2.2 to reflect change in name of Section 15. Part B: Change the name of Section 15Part C: Remove second sentence, including list of features, from 15.1, as it does not agree with current SEMI S3

Please send a courtesy copy of any negatives or comments to: Eric Sklar <[email protected]>

Review and Adjudication InformationTask Force Review Committee Adjudication

Group: S3 Revision TF NA EHS CommDate: 2011/07/11 2011/07/14Time & Timezone: 0800-1000 PDT 0800-1700 PDTLocation: San Francisco Marriott Marquis HotelCity, State/Country: San Francisco, California, USLeader(s): Eric Sklar (Safety Guru, LLC) Chris Evanston, Sean Larsen, Eric Sklar,

James BeasleyStandards Staff: Ian McLeod (SEMI NA), 408.943.6996, [email protected]

This meeting’s details are subject to change, and additional review sessions may be scheduled if necessary. Contact the task force leaders or Standards staff for confirmation.Telephone and web information will be distributed to interested parties as the meeting date approaches. If you will not be able to attend these meetings in person but would like to participate by telephone/web, please contact Standards staff.

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Safety Checklist for SEMI Draft Document #5110Title: Revisions to SEMI S3-0306, Safety Guidelines for Process Liquid Heating Systems and Delayed Revisions to SEMI S2-0310, Environmental, Health, and Safety Guideline for Semiconductor Manufacturing EquipmentDeveloping/Revising BodyName/Type: S3 Revision TFTechnical Committee: EHSRegion: NALeadershipPosition Last First AffiliationLeader Sklar Eric Safety Guru, LLCDocuments, Conflicts, and ConsiderationSafety related codes, standards, and practices used in developing the safety guideline, and the manner in which each item was considered by the technical committee# and Title Manner of ConsiderationSEMI S3-0306 Reviewed for errors and ambiguitiesSEMI S2-0710 Reviewed for consistency with SEMI S3-0306Known inconsistencies between the safety guideline and any other safety related codes, standards, and practices cited in the safety guideline# and Title Inconsistency with This Safety GuidelineSEMI S3-0306 No known inconsistencies result from the proposed changes to SEMI S3. SEMI S2-0710 The proposed changes to SEMI S2 address inconsistencies identified during review.Other conflicts with known codes, standards, and practices or with commonly accepted safety and health principles to the extent practical# and Title Nature of Conflict with This Safety GuidelineNoneParticipants and ContributorsLast First AffiliationWong Carl AKTCrane Lauren Applied MaterialsPlanting Bert ASMLFrankfurth Mark CymerLarsen Sean CymerGiles Andrew ESTEC SolutionsKelly Paul ESTEC SolutionsSinor Russell IBMMcDaid Raymond Lam Research, AGBarsky Joseph Lewis Bass InternationalPyle Jonathan NovellusMacklin Ron R. Macklin & Assoc.Sklar Eric Safety Guru, LLCSawyer Debbie SemitoolKrov Alan TELGwinn Matthew Tokyo ElectronIbuka Shigehito Tokyo ElectronSexton David TUVBogner Mark TUV SudThe content requirements of this checklist are documented in Section 14.2 of the Regulations Governing SEMI Standards Committees.

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SEMI Draft Document 5110Revisions to SEMI S3-0306, Safety Guidelines for Process Liquid Heating Systems and Delayed Revisions to SEMI S2-0310, Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment

SEMI S3-0306SAFETY GUIDELINE FOR PROCESS LIQUID HEATING SYSTEMSNOTICE: This document, as balloted, is intended to replace S3-91 in its entirety.

NOTICE: Paragraphs entitled NOTE are not an official part of this document and are not intended to modify or supercede it.

NOTICE: Conformance to provisions containing the word “should” is necessary to declare conformance to this document. Conformance to those provisions containing “may, “suggested”, “preferred”, or “recommended”, or to NOTES or Related Information is not necessary to declare conformance.

1 Purpose1.1 The purpose of this Safety Guideline is to provide minimum general safety considerations for the design and documentation of heating systems used for changing or maintaining the temperatures of process liquids used in semiconductor and flat panel display manufacturing.1.2 This Safety Guideline provides several means (See Table 1.) of achieving a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) for process liquid heating systems (PLHS). The choice of which means is used is not, however, a criterion for determining conformance with this document.1.2.1 For several common PLHS configurations, this Safety Guideline provides a prescriptive list of safety features to be incorporated in the PLHS. Design and performance criteria for those safety features are also provided. A PLHS that conforms to both the prescriptive list of safety features and the design and performance criteria for those safety features is presumed to achieve a risk level of no greater than Low (as defined by SEMI S10 and SEMI S14) and, thereby, conforms to this Safety Guideline.1.2.2 Conformance with this Safety Guideline may also be achieved by designing a PLHS and incorporating safety features that are selected, designed, and perform such that the risk of the equipment is no greater than Low, as assessed using SEMI S10 and SEMI S14 and considering the hazards discussed within this document. 1: The second way of demonstrating conformance with this Safety Guideline is intended to provide a way to demonstrate conformance by PLHS configurations that are not among those for which prescriptive lists of safety features are provided and by PLHS configurations for which prescriptive lists are provided but for which alternative means of achieving a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) are used. Table 1 Means of conformance to this Safety Guideline.

Selection Of Safety Features By Use Of Tables Selection Of Alternative Sets Of Safety Features To Achieve Risk No Greater Than Low

Design And Function Of Safety Features By Use Of Descriptions in This Document

See §§ 8.2 , 9.1 , through 9.16 , and APPENDIX 2

Risk level of no greater than Low (as defined by SEMI S10 and S14) is presumed to be achieved and PLHS is found to conform

See §§ 8.3 , 9.1 , and 9.3 through 9.16

Risk is to be assessed and whether the PLHS conforms to this Safety Guideline is to be determined as described in ¶ 1.2.2

Design And Function Of Safety Features, Other Than As Described in This Document, To Achieve Risk No Greater Than Low

See §§ 8.2 , 9.2 and APPENDIX 2

Risk is to be assessed and whether the PLHS conforms to this Safety Guideline is to be determined as described in ¶ 1.2.2 .

See §§ 8.3 and 9.2 .

Risk is to be assessed and whether the PLHS conforms to this Safety Guideline is to be determined as described in ¶ 1.2.2 .

This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted standard. Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other reproduction and/or distribution without the prior written consent of SEMI is prohibited.

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Semiconductor Equipment and Materials International3081 Zanker RoadSan Jose, CA 95134-2127Phone:408.943.6900 Fax: 408.943.7943

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2: Cross references within this document are presented as paragraph, figure, or table numbers, usually within parentheses. When this document is viewed with Adobe® Acrobat® or Acrobat Reader, clicking on the number should cause the view of the document to move to that paragraph, figure, or table.

2 Scope2.1 The scope of this document is limited to heating systems designed to change or maintain the temperature of process liquids.3: Equipment, such as ovens and heated substrate supports (e.g., hotplates) intended to change or maintain the temperature of substrates are not “PLHS”, even if heat is transferred to a process liquid.2.1.1 Deionized (DI) Water Heaters Deionized (DI) water heaters are included within the scope of this document when the heated DI water is used as a “process liquid” as defined in § 5 .2.1.2 Heat Transfer Fluids (HTFs) Where fluids are used to transfer heat between heating systems and process liquids, they are included within the scope of this document. For the purpose of this document, HTFs are limited to liquids.2.2 Although the scope of SEMI S3 is PLHS, this guideline may be used to evaluate subsystems to determine if integrating them into a PLHS will cause the PLHS not to conform to this guideline.

NOTICE: This safety guideline does not purport to address all of the safety issues associated with its use. It is the responsibility of the users of this safety guideline to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use.

3 Limitations3.1 This document does not address all safety concerns related to the design of PLHS. See other SEMI Safety Guidelines for other safety provisions (e.g., SEMI S2 for electrical design and SEMI S14 for guidance in fire risk assessment and mitigation).4: The presence of some liquids (e.g., flammable liquids) may require, under the scope of other guidelines or standards such as NFPA 497 or ATEX 94/9/EC, additional safety measures (e.g., purging) for components and systems that are not part of the PLHS.3.2 This document is not intended to replace or supersede any provisions of local codes, national or international standards, or other regulatory requirements.3.3 Existing PLHS should continue to meet the provisions of SEMI S2 and SEMII S3 that were in effect at the time of their design. Process liquid heating systems with redesigns that significantly affect the EHS aspects of the equipment should conform to the latest version of SEMI S3. This guideline is not intended to be applied retroactively.3.4 In many cases, references to standards have been incorporated into this guideline. These references do not imply applicability of the entire standards, but only of the sections or topics referenced. 3.5 Heating systems for liquid materials for dry etch and deposition processes are outside the scope of this document.3.6 Systems for the heating of process liquids by means of exothermic chemical reactions are outside the scope of this document.

Line Item 1, Part A: Paragraph 3.7: Expand the abbreviation “AIT” and clarify intended temperature.3.7 Systems intended to be used to heat liquids to above (a autoignition temperature (AIT) of - 50ºC) less than their autoignition temperatures (AITs) (or within a smaller margin of their AITs, (as described in the Exception to (¶ 9.4.2.1 )) are outside the scope of this document. However, systems that are not intended to be used in that manner, but which have sufficient heater power to heat liquids to such temperatures, are within the scope of this document.3.8 If the process fluid is a gas or plasma when it is in contact with the substrate, the heating systems that control the temperature of fluid delivery systems or process chambers are also not within the scope of this document.

4 Referenced Standards and Documents4.1 SEMI Standards


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lSEMI S2 Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment

SEMI S6 — Safety Guideline for Ventilation

SEMI S14 Safety Guidelines for Fire Risk Assessment and Mitigation for Semiconductor Manufacturing Equipment

SEMI S22 — Safety Guideline for the Electrical Design of Semiconductor Manufacturing Equipment

4.2 NFPA Documents1

NFPA 30 Flammable and Combustible Liquids Code

NFPA 69 Standard on Explosion Prevention Systems

NFPA 496 — Standard for Purged and Pressurized Enclosures for Electrical Equipment

NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

4.3 European Community Directive2

94/9/EC Equipment Explosive Atmosphere (ATEX)4.4 CEN/CENELEC Standard3

Line Item 1, Part B: Paragraph 4.4: Insert a space between “EN” and “1127”.EN 1127-1 — Explosive atmospheres - Explosion prevention and protection Part 1: Basic concepts and methodology

4.5 Underwriters Laboratories Standard4

UL 943 — Standard for Ground-Fault Circuit-Interrupters

NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.

5 Terminology5.1 Abbreviations and Acronyms 5.1.1 AIT — autoignition temperature5.1.2 ATL — accredited testing laboratory5.1.3 FDT — flammable degradation temperature 5.1.4 FR flammable range5.1.5 GFCI — ground fault circuit interrupter5.1.6 HDT — hazardous degradation temperature

Line Item 1, Part C: Paragraph 5.1.7: Place “HTF” in italics.5.1.7 HTF HTF — heat transfer fluid 5.1.8 LFL lower flammable limit (See also the definition for flammable range.)5.1.9 PLHS — process liquid heating system5.1.10 SME — semiconductor manufacturing equipment 5.1.11 UFL upper flammable limit. (See also the definition for flammable range.)5.2 Definitions

1 National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02269, Website: www.nfpa.org2 http://europa.eu.int/smartapi/3 European Committee for Standardization (CEN)/European Committee for Electrotechnical Standardization (CENELEC)Central Secretariat: re de Stassart 35, B-1050 Brussels, Belgium4 Underwriters Laboratories, 333 Pfingsten Rd, Northbrook, IL 60062, www.ul.com


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l5.2.1 accredited testing laboratory (ATL) an independent organization dedicated to the testing of components, devices, or systems; competent to perform evaluations based on established safety standards; and recognized by a governmental or regulatory body. [SEMI S2, S14, S22]5.2.2 autoignition temperature (AIT) — the temperature at which a solid in contact with air, or a liquid or gas (including a vapor) mixed with air, ignites without contacting a surface of higher temperature or there being an explicit source of ignition, such as a spark or flame. 5.2.3 boiling point — the temperature at which the vapor pressure of a liquid equals 101.32 kPa (1 atmosphere, 14.7 psia)5.2.4 closed vessel an enclosed container, typically used for the heating, mixing, or application of process liquids, containing vapors and used in an application where unintended pressurization is possible. Some sealed processing chambers and DI water heaters are examples of closed vessels.5.2.5 combustible liquid a liquid that will burn and has a flash point at or above 37.8°C (100°F). 5: For the purpose of this guideline (SEMI S3), a combustible liquid, when used by a system capable (under normal or single-fault conditions) of heating it above its flash point – 10°C, is treated as a flammable liquid. See § 8.1 .5.2.6 external heater — a heater applied to the outside of a vessel that heats the contents of the vessel through the vessel wall. (See A1-8.1Figure A1-3 and A1-10.1Figure A1-3 for examples of PLHS using external heaters.)5.2.7 fail-safe — designed so that a failure does not result in an increased risk. [SEMI S2]6: For example, a fail-safe temperature limiting device would indicate an out-of-control temperature if it were to fail. This would cause the safety interlocks to remove power from the heaters. That might well interrupt a process, but would be preferable to the device indicating that the temperature is within the control limits, regardless of the actual temperature, in case of a failure.5.2.8 flammable degradation temperature (FDT) — the temperature at which a liquid degrades producing a flammable byproduct. 5.2.9 flammable liquid a liquid having a flash point below 37.8°C (100°F). [SEMI S2, SEMI S14]

5.2.10 flammable range (FR) — the range of concentrations of the dispersed chemical species in air through which a flame will propagate if a source of ignition is supplied. This range is bounded by the lower flammable limit (LFL) and the upper flammable limit (UFL). 7:The following pairs of terms are commonly used interchangeably: “lower explosive limit (LEL)” and “lower flammable limit (LFL)”; “upper explosive limit (UEL)” and “upper flammable limit (UFL)”; and “explosive range” and “flammable range”.

Some literature uses “LEL”, “UEL”, or "explosive range" to designate concentrations to which a more specific criterion (e.g., a certain pressure rise or flame front speed) than the ability to propagate flame pertain. This document uses the “flammable range” terminology to avoid the ambiguity that accompanies the “explosive range” terminology.

5.2.11 flash point the minimum temperature at which a liquid gives off sufficient vapor to form an ignitable mixture with air near the surface of the liquid or within the test vessel used. [SEMI S2] 8: Flash point is determined by one of several standardized test methods at standard atmospheric temperature. The temperature at which the LFL will be reached does, however, depend on the pressure.5.2.12 fluid — liquid or gas [SEMI F78, SEMI F81]5.2.13 gas the fluid form of a substance in which it can expand indefinitely and completely fill its container; form that is neither liquid or solid. [SEMI S4, SEMI F78, SEMI F81]5.2.14 ground fault circuit interrupter (GFCI) — a device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds a value in the range of 4 mA to 6 mA. 9: Several standards, including UL 943, Standard for Ground-Fault Circuit-Interrupters, provide additional information on these devices. 5.2.15 hazardous degradation temperature (HDT) — the temperature at which a liquid degrades producing a hazardous (e.g., flammable, toxic, corrosive, or oxidizing) byproduct. For liquids that have flammable degradation byproducts, the HDT is no greater than the FDT. The HDT, however, is less than the FDT, if the liquid degrades to produce a byproduct with a hazardous characteristic other than flammability at a temperature below the FDT.5.2.16 headspace — the volume above the liquid in a vessel.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l5.2.17 heat transfer fluid (HTF) a liquid used in a heat transfer system to convey heat from a heating source to the process liquid.5.2.18 heated area the portion of the heater surface intended for heat transfer. (See Figure A1-3, A1-7.1FigureA1-3, A1-9.1Figure A1-3, and A1-12.1Figure A1-3 for examples of heated areas.)5.2.19 heater an electrical device used to transfer heat energy to a liquid chemical. The heater consists of the heating element as well as any permanently attached wiring or other components.5.2.20 heating element the electrically conductive component in a heater where electrical energy is converted into heat energy. (See A1-7.1Figure A1-3, A1-8.1Figure A1-3, and A1-12.1Figure A1-3 for examples of heating elements.)5.2.21 inerting — a technique by which a mixture of a flammable gas or vapor in air within its flammable range is rendered nonignitable by the addition of an inert gas. 10: Inerting may be effective by the reduction of the fuel concentration or by reduction of the oxidizer concentration.5.2.22 interlock — a mechanical, electrical or other type of device or system, the purpose of which is to prevent or interrupt the operation of specified machine elements under specified conditions. [SEMI S2]5.2.23 liquid — the fluid form of a substance in which its molecules moving freely with respect to each other so as to flow readily, unlike a solid, but because of cohesive forces not expanding infinitely like a gas.5.2.24 lower flammable limit (LFL) the minimum concentration of a flammable substance in air through which a flame will propagate. (See also the definition for flammable range.)5.2.25 maximum service temperature (for plastic materials) — the highest temperature at which a plastic material has sufficient strength to perform the function for which it was intended. (Documentation and methods to determine the maximum service temperature are given in ¶ 7.3.2 . The maximum service temperature of a plastic material depends on its use and loading in a structure.) 5.2.26 noncombustible liquid — a liquid that does not have a flash point. I.e., there is no temperature to which it can be heated at which it produces flammable vapor in a concentration in air through which a flame will propagate. (The absence of a flash point on an MSDS (e.g., blank space or “N/A”) does not mean that the liquid does not have a flash point.) 5.2.27 open vessel a container, typically used for the heating, mixing, or application of process liquids, in which pressurization is not possible, because there is open communication between the vapor space and some region of near-atmospheric pressure. Open top immersion baths and ventilated storage containers are examples of open vessels.5.2.28 process liquid — a substance that participates, while in the liquid state, in a chemical or physical reaction on the surface of a substrate as part of the manufacturing of semiconductor or flat panel devices.5.2.29 process liquid heating system (PLHS) a heating system comprised of the heater, its power and control systems, the vessel in which the liquid chemical is heated, and, if applicable, the heat transfer liquid and its associated piping. 5.2.30 process vessel — a vessel in which substrates are processed by contact with a process liquid.5.2.31 purging — the process of displacing gases (including vapors) from an enclosure to reduce the concentration of any flammable gases (including vapors) to no more than 25% of their LFL. 5.2.32 radiant heat shield — a component, opaque to the radiant energy, intended to keep the radiant heater from heating liquid overtemperature sensors or other components by radiant heating. For example, one could place a radiant energy shield between a radiant heater and a liquid overtemperature sensor so that the liquid overtemperature sensor could be activated by heat conducted by the liquid, but not by heat radiated through the liquid. 5.2.33 radiant heater sheath — a component, comprised of a material transparent to radiant heat, that contains a heating element and may contain other components. A radiant heater sheath separates the heating element and its other contents from the liquid in which it is immersed. (These sheaths are typically made of quartz and called "quartz sheaths".) 5.2.34 remote heater — a vessel, separate from the process vessel, intended for heating liquid. 11: In heat exchange systems, the system depicted in A1-4.1Figure A1-3 of Appendix 1 is considered a remote heater, while that depicted in Figure A1-3 is not.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l5.2.35 semiconductor manufacturing equipment (SME) — equipment used to manufacture, measure, assemble, or test semiconductor products. It includes the equipment that processes substrates (e.g., silicon wafers, reticles), its component parts, and its auxiliary, support or peripheral equipment (e.g., chemical controllers, chemical delivery systems, vacuum pumps). SME also includes other items (e.g., structures, piping, ductwork, effluent treatment systems, valve manifold boxes, filtration, and heaters) specific to and provided with the aforementioned equipment, but does not include such an item if the item is part of a facility and can support more than one piece of SME.5.2.36 upper flammable limit (UFL) the maximum concentration of a flammable substance in air through which a flame will propagate. (See also the definition for flammable range.)5.2.37 vapor — the gas phase of a substance that is usually considered to be a liquid.5.2.38 vessel a "closed vessel" or an "open vessel", as defined above.5.3 Symbols5.3.1 § — a character used to identify a particular section or subsection of the document. The identified portion includes the numbered paragraph or header identified by the number following the symbol and all subordinate headers and paragraphs, as well as the Exceptions and lists (bulleted or numbered) embedded therein. For example § 9.2 refers to paragraph 9.2, 9.21, 9.2.2, 9.2.3, and 9.2.4. When duplicated, as §§, it refers to more that one section or subsection.5.3.2 ¶ — a character used to identify a particular paragraph of the document. The identified portion includes the numbered paragraph identified by the number following the symbol and the Exceptions and lists (bulleted or numbered) embedded therein. It does not, however, include the subordinate headers and paragraphs. For example ¶ 9.2 refers to paragraph 9.2 only. It does not, however, include paragraph 9.2.1, 9.2.2, 9.2.3, and 9.2.4. When duplicated, as ¶¶, it refers to more that one paragraph.

6 Liquid Heating Method Classifications6.1 This section provides classifications that later sections will use when providing considerations for specific types of PLHS.6.2 Location of PLHS6.2.1 Process liquid heating systems may either be incorporated in a process vessel or be located remotely.12: See Figure A1-3, A1-5.1Figure A1-3, A1-6.1Figure A1-3, A1-8.1Figure A1-3 and A1-11.1Figure A1-3 in Appendix 1 for examples of PLHS incorporated into process vessels and A1-4.1Figure A1-3, A1-9.1Figure A1-3, A1-10.1Figure A1-3 and A1-13.1Figure A1-3 in Appendix 1 for examples of remote PLHS.6.3 Source of Heat Energy6.3.1 Heat energy is typically obtained from another liquid or an electric current.6.3.2 Heated Liquid Heat Exchange System — This is a PLHS that uses a heater that may be located remotely from the heated vessel. The heater heats an HTF that in turn heats the process liquid by means of a heat exchanger (i.e., a device that allows heat energy to be transferred between the HTF and the process liquid, but prevents direct contact between them). There are three common configurations of such systems:6.3.2.1 A remote heat exchange system may employ a dual-loop system and counterflow-type heat exchanger. 6.3.2.2 An external heater may be used in conjunction with a pump and a double-walled vessel where the heated transfer fluid is pumped from the external heater to the space between the inner and outer walls of the process vessel and heat exchange to the process liquid takes place through the vessel inner wall. 6.3.2.3 A third version uses a double- walled process vessel with a heater and the HTF in the space between the inner and outer walls of the vessel. 13: Figure A1-3, A1-4.1Figure A1-3, and A1-5.1Figure A1-3 in Appendix 1 depict typical PLHS using heat exchangers. Table A2-1a , Table A2-1b, Table A2-1c, Table A2-2a, Table A2-2b, and Table A2-2c, in APPENDIX 2 contain design considerations for heated liquid heat exchangers.6.3.3 Electrical Resistive Element Heaters Heaters of this type use the energy generated by the resistance to the passage of electrical current through a conductor to heat a liquid. 6.3.3.1 Configuration of Electrical Resistive Element Heaters6.3.3.1.1 The relationship of the heating element to the process liquid varies with system design.6.3.3.1.2 Thermally conductive heaters — Thermally conductive heaters transfer energy by contact with the liquid being heated. They may either be immersion heaters, which are immersed directly in the liquid to be heated, or


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lexternal heaters, which are normally bonded to the outside of a vessel. External heaters transfer energy by means of conduction from the heating element through the vessel wall to the liquid being heated. Common external heaters are manufactured from a thin metal material that results in a low-profile configuration.14: See Figure A1-3, A1-4.1Figure A1-3, A1-5.1Figure A1-3, A1-6.1Figure A1-3, and A1-9.1Figure A1-3 in Appendix 1 for examples of PLHS using immersion heaters (and A1-7.1Figure A1-3 for a detail of an immersion heater), and A1-8.1Figure A1-3 and A1-10.1Figure A1-3 in Appendix 1 for examples of PLHS using external heaters. Table A2-3a, Table A2-3b, and Table A2-3c in Appendix 2 contains design considerations for thermally conductive heaters; see also § 8 .6.3.3.1.3 Radiant heaters — Radiant heaters (e.g., infrared heaters) use a glowing element that is separated from the liquid by nonconductive materials, usually air and quartz glass. Direct contact of liquid with the heater is not required for the transfer of heat energy. In some cases, infrared heaters may be located in wells within process vessels.15: A1-12.1Figure A1-3 in Appendix 1 depicts a detailed view of a typical radiant heater. A1-11.1Figure A1-3 and A1-13.1Figure A1-3 depict the use of radiant heaters in PLHS. Table A2-4a, Table A2-4b, and Table A2-4c in APPENDIX 2 contains design considerations for radiant heaters; see also § 8 .6.4 Dependence on Flow of the Heated Process Liquid 6.4.1 Systems vary in their dependence on flow of the heated process liquid to keep system elements and surroundings within intended temperature ranges. Surroundings include the process liquid chemical as well as the vessel and its supports.6.4.1.1 Flow-Independent Systems — The heat transfer properties of these systems is such that free convection of the process liquid is sufficient for safe operation of the system. No means of flow or agitation is required to prevent overheating of the system or its surroundings. 6.4.1.1.1 Some systems (e.g., filtered recirculation baths) may use flow for other purposes but not for preventing overheating; these are considered flow-independent systems for the purpose of this guideline. 6.4.1.2 Flow-Dependent Systems — the heat transfer properties of these systems requires forced convection (e.g., flow or agitation of the liquid being heated) to prevent overheating of the system or its surroundings.

7 General Safety Considerations7.1 Selection and Integration of Electrical Components, Devices and Assemblies used in PLHS 7.1.1 Within a PLHS, each electrical component or subsystem that has been certified by an accredited testing laboratory should be evaluated to determine whether its use is within the limits of its certification. If the use is within the limits of certification, no further evaluation of the component or subsystem is necessary. If the use is outside of the limits of the certification, the component or subsystem should be evaluated as if it were not certified.7.1.2 Within a PLHS, each electrical component or subsystem operating in a safety circuit or within a hazardous voltage circuit that has not been certified by an accredited testing laboratory should be evaluated to applicable standard(s) or guideline(s), such as the appropriate portions of SEMI S2. 7.2 In no case should a PLHS achieve, under normal conditions, reasonably foreseeable single-point failures of the SME, and reasonably foreseeable misuse, temperatures or energy transfer rates that endanger the mechanical integrity of the PLHS or adjacent construction materials. This protection may be provided either through the use of PLHS that cannot attain damaging temperatures, or through the use of safety systems. 16: A "reasonably foreseeable single point failure" includes all of the consequences, including failure of other components or subsystems, that result from an initial failure. It does not, however, include cases where two or more independent failures occur.7.3 Construction Materials All portions of the PLHS that are heated or could come in contact with the chemicals should be constructed from appropriate materials. The maximum temperature and chemical exposure of each portion, during normal operation, maintenance, and under reasonably foreseeable, worst case single fault conditions should be considered. Chemical exposure includes exposure to the liquid (e.g. immersion, flow or spray) and to its vapors or aerosols.)7.3.1 Testing to determine the properties of materials at reasonably foreesable worst case temperature and exposure conditions may be performed in a suitable environmental test chamber, i.e., the properties need not be determined by testing in a PLHS. 17: Materials selection considerations include many factors, including compatibility of the material with the process liquid under operating conditions, that are outside the scope of this document.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l18: It is recommended that designers of vessels obtain the physical strength characteristics at the maximum temperature under single point failure conditions and safety factors from the supplier of the material. It is also recommended that the vessel design be based on that information, the anticipated load, and an appropriate safety factor for the final design.7.3.2 Maximum Service Temperature for Plastic Materials 7.3.2.1 Where temperature/strength limits for plastic components are available, the maximum service temperature is the temperature at which the plastic component's strength is equal to the maximum expected loading of the component. 7.3.2.2 Where these limits are not available, the equipment manufacturer should determine the maximum service temperature of components by engineering calculations or system testing at the maximum expected load.7.3.3 Electrical Wiring7.3.3.1 Insulation should be chemically resistant to the liquids to which it is expected to be exposed and their vapors. 7.3.3.2 Wiring materials (e.g., single conductors and multiple conductor cable) should be certified by an ATL as being capable of withstanding the temperatures expected. Where chemical compatibility or temperature concerns preclude the use of ATL certified wiring, the wiring should be used in accordance with the manufacturer's recommendations and be tested according to the dielectric strength test for conductors described in SEMI S22. This dielectric withstand testing should be conducted at the highest expected temperature under single-point failures.19: In the 1103 edition of SEMI S22, this test was described in ¶ 16.2.7.

8 Selection of Safety Features20: Several examples of the selection of safety features are provided in RI 2.8.1 Classification of HTF and process liquids8.1.1 The flowchart in Figure 1 should be used to classify each HTF (if one is to be used in the PLHS) and each process liquid as flammable, combustible, or noncombustible.8.1.2 If liquids are heated as a mixture, then the properties of the mixture should be used to determine the classification of the liquid. 8.1.2.1 If the properties of the mixture are not known, they should be obtained by testing. 8.1.2.2 As an alternative to testing, the lowest flash point of the flash points of the constituents of the mixture may be used as the flash point of the mixture for the purposes of classification and establishing interlock set points. The lowest of the constituents' autoignition temperatures and decompositions temperatures may be used in the same manner.8.1.3 If the liquids are heated as separate components, then mixed, the properties for each component of the mixture should be used in determining the classification of that component.8.1.4 If this Safety Guideline is being used to select safety features to be incorporated in a PLHS (rather than to assess whether appropriate safety features are included in a PLHS which has already been designed or constructed), the designer should determine whether adhering to the temperature limits relative to the HTF's or process liquid's flash point, flammable degradation temperature and autoignition temperature is consistent with the intended use of the equipment. If adhering to those limits is consistent with the intended use, then the safety features should be selected so as to adhere to those limits (E.g., a liquid overtemperature interlock set at no more than the liquid's flash point minus 10°C should be provided for a system intended to heat a combustible liquid to no more than its flash point minus 10°C.). If adhering to those limits is not consistent with the intended use, then the safety features should be selected to address the risks of the intended use. (E.g., if the PLHS is intended to be used to heat a combustible liquid to or above its flash point minus 10°C, then the safety features should be selected using the criteria for a flammable liquid.)


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Note 1: “FP-10” means 10°C less than the liquid’s flash point. If the liquid is noncombustible, then the heater is not capable of heating the liquid to FP-10. If the liquid is combustible and the heater is capable of boiling the liquid, then the heater is capable of heating the liquid to FP-10.Note 2: “FDT-10” means 10°C less than the temperature at which the liquid yields flammable degradation products. If degradation of the liquid does not produce flammable products, then the heated area is not capable of exceeding FDT-10. If FDT is unknown, but the thermal degradation of the liquid is known to have flammable byproducts, assume heated area can achieve FDT-10.Note 3: The phrases "Is heater capable" and "Is heated area capable" refer to the power of the heater, operated continuously at the available voltage and current, considered in the context of the liquid's properties and the configuration of the PLHS.Note 4: “Liquid” refers to the process liquid or HTF, depending on for which you are trying to determine if it is to be considered “combustible” or “flammable”.

Figure 1Means of Determining Whether a Liquid is to be Treated as Flammable, Combustible, or Noncombustible

8.2 Selection of Safety Features using the Tables in Appendix 2

EXCEPTION: Instead of conformance to the provisions of § 8.2 , alternative means of achieving a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) may be used in accordance with the criteria of § 8.3 .

8.2.1 The heating method and the classification (flammable, combustible, or noncombustible) of the liquid should be used with Table 2 to select the appropriate table(s) in APPENDIX 2.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable 2 Selection of Safety Features

Heated Liquid Heating Method Liquid Safety Feature Table

Heat Transfer Fluid Any Flammable HTF Table A2-1a

Combustible HTF Table A2-1b

Noncombustible HTF Table A2-1c

Process Liquid Heat Transfer System Flammable process liquid Table A2-2a

Combustible process liquid Table A2-2b

Noncombustible process liquid Table A2-2c

Thermally- Conductive Heaters – Immersion Heaters or External Heaters

Flammable process liquid Table A2-3a



Radiant Heaters Flammable process liquid Table A2-4a



8.2.2 The tables in Appendix 2 list process liquid properties and heating system characteristics that may pertain to a PLHS and the corresponding safety features. The appropriate table(s) in APPENDIX 2 should be used to select the safety features for each PLHS.8.2.3 The PLHS should incorporate the safety features identified by the tables in APPENDIX 2. 8.2.4 If a PLHS uses an HTF, the safety features identified by Table A2-1a, b, or c should be incorporated in the portion of the PLHS that heats the HTF and the safety features identified by Table A2-2a, b, or c should be incorporated in the portion of the PLHS that heats the process liquid.8.3 Selection of Safety Features Based on Risk8.3.1 ¶ 8.3 should be used if the PLHS is not described by one or more of the Tables in Appendix 2 or if the equipment supplier chooses to use alternative means of achieving a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14).8.3.2 The risks of the PLHS should be assessed in accordance with SEMI S10 and SEMI S14. The hazards and risks considered should include those described in SEMI S2 and this Safety Guideline.8.3.3 Safety features (e.g., interlocks) and practices should be included in the system to ensure that the residual risk is no greater than Low (as defined by SEMI S10 and SEMI S14).8.3.4 If the safety features are selected based on risk, rather than on the Tables in Appendix 2, then the statement of conformance to SEMI S3 should include the information that the risk method, rather than the Tables, was used.

9 Design and Performance of Safety Features9.1 Safety features should be designed and should perform as described in §§ 9.3 through 9.16 .

EXCEPTION: Alternative designs of safety features may be used, in accordance with the criteria of § 9.2 and its subparagraphs.

9.1.1 Not every PLHS needs all of the safety features described in the following sections. The safety features for each PLHS should be selected in accordance with § 8 . The design and performance of the safety features should be as described in the following sections. 9.2 If the safety features are not as described in §§ 9.3 through 9.16 , the safety features should conform to ¶¶ 9.2.1 through 9.2.4 .9.2.1 The risks of reliance on each safety feature that does not conform to §§ 9.3 through 9.16 . should be assessed in accordance with SEMI S10 and SEMI S14. The hazards and risks considered should include those described in SEMI S2 and this Safety Guideline.9.2.2 The design and performance of safety features (e.g., interlocks) should ensure that the residual risk is no greater than Low (as defined by SEMI S10 and SEMI S14).


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l9.2.3 If the safety features are found to be acceptable based on risk, rather than on §§ 9.3 through 9.16 , then the statement of conformance to SEMI S3 should include the information that the risk method, rather than §§ 9.3 through 9.16 , was used. 9.2.4 The use of risk assessment, rather than conformance to §§ 9.3 through 9.16 to find the design and performance of a safety feature selected in accordance with APPENDIX 2 to result in a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) does not, itself, impose a criterion that the risk of the entire PLHS be assessed. I.e., a PLHS may be found to conform to SEMI S3 if the safety features are selected in accordance with APPENDIX 2 but one or more of the safety features are found acceptable on the basis of resulting in a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14), rather than on the basis of conformance with §§ 9.3 through 9.16 .9.3 Characteristics Common to All Safety Interlocks9.3.1 Safety interlock systems should comply with the safety interlock systems provisions of SEMI S2.9.3.2 A reset should be incorporated into safety interlock systems so that when the safety interlock system interrupts the PLHS, an informed and deliberate human intervention is necessary to re-energize the PLHS.21: An interlock is defined in § 5 as “a mechanical, electrical or other type of device or system, the purpose of which is to prevent or interrupt the operation of specified machine elements under specified conditions.” Although the same devices and circuitry may be used for the “prevent” and “interrupt” functions, the inclusion of a requirement for informed and deliberate resetting pertains only to the “interrupt” function. For example: A low level sensor in a vessel may be the input to an interlock for heater power. That interlock serves both functions:1. it prevents (as a backup to the control program) the application of heater power during the vessel’s programmed empty and

refill cycle and2. it interrupts the heater power if the liquid level in the vessel reaches the low level while heater power is being applied.

The intent of the preceding paragraph is that the system requires an informed and deliberate human intervention to re-energize the heater in the second case, but not the first. This is because the first case (the low level with heater off) is a “normal” condition, while the second case (the low level with the heater on) is an “abnormal” condition.

9.3.3 Safety interlock system sensors and their associated circuitry and wiring should be separate from those used for process control. “Separate from” means that the interlock has no components (e.g., sensors, control circuits, or actuators) in common with the process control.

EXCEPTION: There may be common elements if the safety interlock system is fail-safe.

22: This differs from S2-0703 in that the criterion in this Safety Guideline is “fail-safe”, not “fault tolerant”. “Fault tolerant” is defined as “designed so that a reasonably-foreseeable single point failure does not result in an unsafe condition.”. As “unsafe condition” is not defined, some have argued that an interlock that merely ceases to function meets this critierion, as long as the interlock itself does not, by failing, introduce some hazard. For example, if two thermocouples are used to measure a temperature of an object and one of the thermocouples becomes separated from the object and now measures a lower temperature, one might argue that the system is “fault tolerant”, because the detachment of the thermocouple does not raise the temperature of the object. However, a fail-safe system would be, for example, one in which the thermocouple temperatures were compared and, if they were substantially differenent, a fail-safe (defined as “designed so that a failure does not result in increased risk”) system would remove power from the heaters if it detected a significant discrepancy between the thermocouple temperatures.9.3.4 Single-point failure — Safety interlocks should be used to back up process controls in the event of their failure, not be used as de facto process controllers. For one example, low-liquid level safety interlocks (§ 9.6 ) and liquid flow safety interlocks (§ 9.7 ) should not be used as the primary means of de-energizing heaters when process vessels are drained. Instead the drain sequence should de-energize heaters as part of the drain sequence. (RELATED INFORMATION 1 contains a discussion of example design practices.) The low-liquid level safety interlock (§ 9.6 ) should be used as protection only if this sequence fails to occur. For another example, process temperature controllers should not be set to temperatures higher than the setpoint temperature for the liquid overtemperature safety interlock. If the process temperature controller were set to a temperature higher than that of the overtemperature interlock, the overtemperature interlock would become the de facto controller and the system would be unprotected should the interlock fail. 23: For a process controller in which the process temperature is set in software, the limit on the temperature to which the process controller may be set may also be set in software, provided that a higher level of software access is necessary to set the limit than is necessary to set the process temperature.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l9.4 Liquid Overtemperature Safety Interlock The liquid overtemperature safety interlock should prevent process liquids from reaching a point where the properties of the liquid change to create a potentially dangerous situation (e.g., reach boiling, autoignition or flammable degradation temperatures). 9.4.1 Liquid overtemperature protection may be provided either by a separate safety interlock or by using a process temperature controller approved by an accredited testing laboratory for use as both a process temperature controller and for overtemperature protection. If such an approved device is used for both process control and the safety interlock, it should be fail-safe.24: Not all devices approved by accredited testing laboratories are fail safe.9.4.2 A liquid overtemperature setpoint should be determined based on both the chemicals being heated and the properties of the materials of construction in contact with the liquid. In general, the liquid overtemperature setpoint may be set as high as is consistent with safety considerations. 9.4.2.1 For liquids, the maximum overtemperature setpoint should be selected by using Table 3.

Line Item 2: Removal of ambiguity in parsing of formula for maximum set pointTable 3 Selection of Maximum Overtemperature Interlock Setpoint

Liquid Treated As Maximum Overtemperature Setpoint

Noncombustible Boiling PointFlammable Lesser of Boiling Point or (Autoignition Temperature - 50ºC) or Boiling PointCombustible Flash point - 10ºC

The liquid overtemperature setpoint for combustible liquids may be set higher than the liquid’s flash point minus 10 ºC, however, the liquid should then be considered a flammable.

EXCEPTION: Small margins (i.e., temperatures within 50ºC of the autoignition temperature or within 10ºC of the flash point) may be used if the interlock performance is found, through testing or analysis, to preclude reaching the autoignition or flash point. If a smaller margin is used, the rationale for its acceptance should be documented in the SEMI S3 conformance assessment report.

25: The limitations in this table preclude the use of PLHS that heat liquids in closed vessels at pressures above atmospheric pressure and to temperatures above the liquid's boiling point, but without boiling the liquid. Such PLHS may, however, be found to be in conformance with this document based on the assessment of the risk of the pressure and temperature control features. 9.4.2.2 A risk assessment should be conducted to determine that all components are at or below their maximum service temperature for the liquid overtemperature setpoint chosen. The risk assessment should include all liquid containment, piping, and support structures associated with the PLHS. 9.4.3 The liquid overtemperature sensor should be located so that it will accurately reflect the highest temperature of the liquid. 26: See Appendix 1 for examples of placement of liquid overtemperature safety interlock sensors for various PLHS. 9.5 Heater Overtemperature Safety Interlock A sensor should be located and set at a temperature that prevents degradation of the structural integrity of the heater or its surrounding materials. 9.5.1 If there is a low liquid level safety interlock, the heater overtemperature safety interlock should prevent degradation at any liquid level above the level at which the low liquid level safety interlock removes power from the heater. 9.5.2 If there is no low liquid level safety interlock, the heater overtemperature safety interlock should prevent degradation at any liquid level, including the absence of liquid.9.5.3 Overtemperature conditions may occur at different locations, and multiple sensors may be required to monitor those locations.27: See Appendix 1 for places where heater overtemperature safety interlock sensors may be located for various PLHS.9.5.4 A single safety interlock may be used as both the Heater Overtemperature and Heated Area Overtemperature Safety Interlocks, as long as the setpoint is no more than the lower of the setpoint temperatures determined to be appropriate for the individual interlocks.9.6 Low-Liquid-Level Safety Interlock This interlock should protect from failure due to loss of the heat absorption capacity of the liquid.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l9.6.1 The low-liquid level safety interlock should be located such that it allows a sufficient volume of process liquid to remain present to absorb residual heat energy to assure that a hazardous temperature is not reached by either the process liquid or the PLHS when the process liquid is at the setpoint temperature of the liquid overtemperature safety interlock.28: See Appendix 1 for places where low-liquid level safety interlock sensors may be located for various PLHS.9.6.2 The selection of a suitable sensor should take into account the physical properties of the liquids being heated, the environmental conditions to which the sensor will be subjected, and the failure mode(s) of the sensor.9.6.3 Where a liquid overtemperature safety interlock is used, the sensor for the low-liquid level safety interlock should be located so that the sensor for the liquid overtemperature safety interlock is immersed in liquid below the level where the low-liquid level safety interlock allows energization of the PLHS. 9.7 Liquid Flow Safety Interlock — In a flow dependent system, a sensor to monitor for liquid flow should be provided that allows the PLHS to be energized only when a safe rate of flow is present. 29: Flow switches are not the only means of monitoring adequacy of flow.30: Providing a common source of power for both the liquid pump and the PLHS may not be sufficient to assure liquid flow, because pump failure might not be detected by such a design. 31: See Appendix 1 for places where liquid flow safety interlock sensors may be located for various PLHS.9.7.1 The configuration of the vessel containing the flow dependent heater should be such that a hazardous temperature is not reached by either the process liquid or the liquid chemical heating system when the process liquid flow is interrupted and the heater is at the setpoint temperature of the liquid overtemperature safety interlock. This criterion may be met by ensuring a sufficient volume of process liquid remains present upon interruption of flow to absorb residual heat energy to assure that hazardous temperatures are not reached.9.8 Overpressure Protection 9.8.1 A means, such as adequate venting capability, should be sufficient to prevent rupturing of the vessel due to excessive pressure or vapor generation.32: An equation that can be used to estimate needed vent capacity is given in Related Information 1.9.9 Inerting — Inerting of the vapor space of a vessel is effective as a risk control measure when the vessel is substantially sealed and there is no introduction of air or other oxidizer that can cause the vapor concentrations to pass through the flammable range. Inerting is also effective as a risk control measure for the space between the heating filament and the sheath in radiant heaters.9.9.1 Where an inert atmosphere is used, it should be confirmed, by measurement of the oxygen concentration in a representative sample of the design, that the inerting system is effective in reducing oxygen to a level where combustion will not be supported unless air or oxygen is introduced. 33: Extreme caution should be taken following inerting of a vessel as opening the enclosure may cause the mixture to pass through the flammable range if fresh air is admitted.9.9.2 Inerting Safety Interlock9.9.2.1 When inerting is used, an appropriate safety interlock should be provided to monitor the inert gas flow and prevent the heater from operating unless there is adequate performance of the inerting system.9.9.2.2 Energization of the PLHS should be prevented until a sufficient volume of inerting gas has been introduced to reduce the oxidizer concentration to an acceptable level.34: Information on the minimum concentration of oxygen to support combustion of various fuels can be found in published literature and standards, such as NFPA 53, Recommended Practice on Materials, Equipment, and Systems Used in Oxygen-Enriched Atmospheres. 9.9.2.2.1 It is acceptable to ensure that a sufficient delay is provided between detection of inert gas flow and energization of the heater to assure that the oxidizer concentration has been reduced to an acceptable level. Direct measurement of oxidizer concentration is not required.35: This time delay may be determined from measurement of oxygen concentration in a representative sample of the design, or by engineering calculations. 9.9.2.3 If flow is required to maintain an inert atmosphere, energy to the heaters should be interrupted if an insufficient flow is detected.36: A flow monitor on the inert gas inlet is not sufficient to ensure adequate performance of the inerting system. Outlet flow, or inlet flow combined with pressure monitoring within the inerted vessel, is the preferred means of detecting adequate flow.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l9.9.3 Nitrogen or other inert gases, when used as carriers for flammable vapors (e.g., in alcohol vapor driers), may be considered in determining whether of the PLHS conforms to § 9.9 .9.9.4 Purging with an inert gas, designed and tested in accordance with an appropriate standard (e.g., NFPA 496 or EN1127-1) may be presumed to conform to the criteria of § 9.9 , as it reduces the fuel concentration. 37: Inerting the radiant heaters can be such a suitable means of preventing ignition at the heater element surface, because the exclusion of oxidizers from the heater elements prevents the elements being in contact with a mixture of flammable vapor and an oxidizer. However, purging the radiant heaters with air does not provide this protection, as a mixture of flammable vapor and air is, in some range of concentrations, ignitable. A description of purging is provided below. 9.10 Purging — Purging of the vapor space of a vessel may be effective as a risk control measure. 38: Both the loss of the process liquids into the exhausted air and the need to treat the air containing them properly should be considered when considering this method. 9.10.1 Where purging is used, it should be confirmed, by measurement of the flammable vapor concentration in a representative sample of the design, that the purging system is effective in reducing the concentration of the flammable vapor to no more than 25% of the LFL within the vessel when the liquid is at the maximum single-fault temperature.9.10.2 Purging Safety Interlock — When purging is used, an appropriate safety interlock should be provided to ensure that a sufficient flow is present to remove flammable vapors to below 25% of LFL. Energy to the heaters should be interrupted if an insufficient flow is detected. 9.10.3 Purging designed and tested in accordance with an appropriate standard (e.g., NFPA 496 or EN1127-1) may be presumed to conform to the criteria of § 9.10 . 39: Purging is a means of protection applicable to headspaces over liquids. It is not, however, applicable to protecting a heater that could be flooded if a barrier failed. Inerting is applicable both to heaters and headspaces.40: A flow monitor on the purge inlet port(s) is not sufficient to assure adequate performance of the purge system. Monitoring of outlet port flow is the preferred means of detecting if adequate flow is present. If no defined outlet is available, then inlet flow and pressure monitoring within the purged vessel or enclosure is acceptable. 9.11 High Temperature Metal Construction9.11.1 Vessels used to contain flammable liquids should be constructed of metals that have sufficient strength at 1100°C (2012°F) to contain the liquids, unless such materials are not suitable due to process compatibility concerns. The reasonably foreseeable weight and pressure of the liquid should not result in stresses greater than the room temperature ultimate tensile strength divided by 3.5.41: The factor of 3.5 was obtained from the ASME Boiler and Pressure Vessel Code.42: Various codes, regulations and standards specify either the types of metal (e.g., ferrous metal) or the melting points of metals used to contain flammable liquids. Conformance with the criterion in this document does not necessarily comprise compliance with the relevant codes, regulations and standards applicable to the location in which the PLHS is to be used.

EXCEPTION: Alternate materials, such as plastics, may be used only if it can be confirmed, by means of a risk assessment, that the method of containment and the materials used provide a level of Risk no greater than Low (as defined by SEMI S10 and SEMI S14) in the following situations:

During normal process temperature ranges controlled by the process temperature control. During abnormal temperature conditions up to the value limited by the overtemperature safety interlock. During a fire involving the chemicals contained within the vessel or liquid chemical heating system (e.g., within

a process vessel). During a fire elsewhere within the equipment (e.g., within the wet bench subsurface area).

43: The intent is that the Exception criteria and discussion of plastic materials in § 7 encourage the designer to consider issues such as the suitability of the plastics for normal and abnormal process temperatures and the associated mechanical, thermal and chemical stresses that would be experienced.44: It may be possible to address the fire risk and process compatibility concerns by using: a vessel of a suitable (to manage the fire risk) metal lined with a process-compatible plastic, a process-compatible plastic vessel inside a suitable metal vessel, or a process-compatible plastic vessel with secondary containment constructed of a suitable metal

9.12 Protection of Personnel from Electrical Shock — Personnel should be protected from electric shock by at least one of the following means:


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l9.12.1 Ground Fault Circuit Interrupter (GFCI) certified by an ATL as complying with an appropriate standard for the protection of personnel9.12.2 Inclusion of a grounded conductive barrier between the heating element and the HTF or process liquid9.13 Shielding from Radiant Heating9.13.1 A shield, opaque to the radiant energy, should be provided to protect those components and surrounding materials the temperatures of which can be raised by radiant heating to above their maximum service temperatures. 9.13.2 A shield, opaque to the radiant energy, should be provided to protect overtemperature sensors (other than those intended to sense the temperature of the radiant heating element) from radiant heating.9.14 Heated Area Overtemperature Safety Interlock A sensor should be located and set at a temperature that prevents the heated area's reaching the FDT-10 if the heated area is submerged in the liquid. 9.14.1 Overtemperature conditions may occur at different locations, and multiple sensors may be required to monitor those locations.9.14.2 A single safety interlock may be used as both the Heater Overtemperature and Heated Area Overtemperature Safety Interlocks, as long as the setpoint is no more than the lower of the setpoint temperatures determined to be appropriate for the individual interlocks.9.15 Certification for Use in Hazardous Locations — Electrical PLHS components and equipment for use in locations that have been classified as hazardous (i.e., from an “explosive” or flammable standpoint) should be specifically certified or otherwise evaluated to the applicable standards for that use. 45: UL 823, UL 1604 and the IEC 60079 series are among the documents that provide methods for making this evaluation.46: NFPA 497 and EN 1127-1 are among the documents that provide methods for determining hazardous locations.9.16 Heat Exchanger Overtemperature Safety Interlock A sensor should be located and set at a temperature that prevents degradation of the structural integrity of the heat exchanger, the vessel containing the process liquid, or their surrounding materials at any process liquid level, including the absence of process liquid. 47: See Appendix 1 for places where heater overtemperature safety interlock sensors may be located for various PLHS.9.16.1 Overtemperature conditions may occur at different locations, and multiple sensors may be required to monitor those locations.9.16.2 This interlock should perform its intended function at the maximum temperature to which the HTF may be heated, considering the power of the heater and any interlocks incorporated in the heated liquid heat exchange system.

10 Documentation10.1 Documentation supplied with the system should describe the tests that should be performed periodically on the process temperature controllers and safety interlocks of PLHS. These tests should not be destructive in nature. Tested devices should include temperature controls and their sensors, liquid overtemperature interlocks, heater overtemperature interlocks, level controls, low-liquid level safety interlocks, liquid flow safety interlocks, flow and pressure sensors for purging or inerting gasses and flammable vapor detectors.

EXCEPTION: Process temperature controllers, or parts of process temperature controllers, that either do not provide safety functions or are automatically monitored are excluded from the above periodic testing provision.

10.2 Documentation should include the test procedures to be used and the intervals for testing. 48: See SEMI S2 and SEMI S13 for other information that should be included in documentation.

11 Related Documents11.1 ASME Document5

Boiler and Pressure Vessel Code

5 American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990, USA. Telephone: 800.843.2763 (U.S./Canada), 95.800.843.2763 (Mexico), 973.882.1167 (outside North America), www.asme.org


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l11.2 ASTM Documents6

ASTM C1147 — Practice for Determining the Short Term Tensile Weld Strength of Chemical-Resistant Thermoplastics

ASTM D150 — Dielectric Constant, Dissipation Factor

ASTM D621 — Deformation under Load

ASTM D638 — Tensile Strength and Ultimate Elongation

ASTM D648 — Heat Deflection Temperature/Heat Deflection Temperature Under Load

ASTM D790 — Flex Modulus

ASTM D792 — Specific Gravity

ASTM D1238 — Melt Flow Rate

ASTM D2240 — Hardness

ASTM D2990 — Creep Resistance

ASTM D4591 — Melting Point

11.3 DVS Guideline7

DVS 2205-1 — Design Calculations for Containers and Apparatus Made of Thermoplastics — Characteristic Values

11.4 International Electrotechnical Commission Documents8

IEC 60079-0 — Electrical Apparatus for Explosive Gas Atmospheres

11.5 NFPA9 Documents

NFPA 1 — Uniform Fire Code

NFPA 53 — Recommended Practice on Materials, Equipment, and Systems Used in Oxygen-Enriched Atmospheres

NFPA 70 — National Electrical Code

NFPA 77 — Recommended Practice on Static Electricity

NFPA 318 — Standard for the Protection of Semiconductor Fabrication Facilities

11.6 UL Documents10

UL 746B — Maximum Continuous In-Use Temperature

UL 843 — Standard for Electric Heaters for Use in Hazardous Locations

6 American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428-2959, USA. Telephone: 610.832.9585, Fax: 610.832.9555, www.astm.org7 DVS-Verlag GmbH, Aachener Str. 172, D-40223 Duesseldorf, Phone: +49-211 1591-161, Fax: +49-211 1591-150, http://www.dvs-verlag.de8 International Electrotechnical Commission, 3, rue de Varembé, Case Postale 131, CH-1211 Geneva 20, Switzerland. Telephone: 41.22.919.02.11; Fax: 41.22.919.03.00, www.iec.ch9 National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02269, www.nfpa.org10 Underwriters Laboratory, 333 Pfingsten Rd, Northbrook, IL 60062, www.ul.com


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lAPPENDIX 1REPRESENTATIVE LAYOUTS FOR VARIOUS PROCESS LIQUID HEATING SYSTEMSNOTICE: The material in this Appendix is an official part of SEMI S3 and was approved by full letter ballot procedures on November 29, 2005.

A1-1 PurposeA1-1.1 This Appendix is provided to aid in the identification of components and terms described in this Safety Guideline. Drawings of various PLHS typically used in semiconductor or flat panel display manufacturing are provided here. A1-1.2 It is not the purpose of this Appendix to limit PLHS to those depicted here. A1-1.3 It is not the purpose of this Appendix to indicate which safety features and practices are to be used for which types of systems.

A1-2 UseA1-2.1 The user should select the figure that most closely approximates the system under consideration. Components used in the actual system under consideration should be compared to those in the drawings to determine the application of terms used in the guideline to actual components in the system under consideration. 49: So that the numbering of Figures and Tables aligns with the numbering of the text, Figures and Tables in this Appendix are numbered starting with A1-3. Figure and Table numbers A1-1 and A1-2 are purposely omitted from this document.


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A1-3 Typical Heated Liquid Heat Exchanger, where a Double-Wall Process Vessel is Being Used as the Heat Exchanger between the Process liquid and the HTFA1-3.1 Figure A1-3 is a drawing of a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-3.

(process chemical)

Heat Transfer Fluid (HTF)

Liquid level (process chemical)

Sensor for low-liquid level safety interlock (HTF)Sensor for liquid overtemperature safety interlock (HTF)

Low-liquid levelsafety interlock(process chem.)

ProcessVessel

Heated area

Heater / CirculatorUnit

(HTF)

Sensor for liquidflow safetyinterlock

Sensor for heater overtemperature

safety interlock

Heater

(process chem.)

Liquid overtemperature

safety interlock

Area(for HTF)

Heated

Figure A1-3 Typical Heated Liquid Heat Exchanger, where a Double-Wall Process Vessel is Being Used as the Heat

Exchanger between the Process liquid and the HTF

A1-3.2 The process vessel is of double-wall construction. A separate jacket is provided around the vessel, slightly below the process liquid level. The HTF is heated in a Heater/Circulator unit that contains the heater, process temperature controls, and a circulating pump that pumps the HTF to the process vessel. Because the HTF loop is closed, the pump also provides a pressurized return to the Heater/Circulator. Separate components (heater, process temperature controller and pump) could be used in place of this Heater/Circulator unit.A1-3.3 Table A1-3 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-3 Interlocks & Safety Features, Typical Heated Liquid Heat Exchanger, where a Double-Wall Process Vessel is Being Used as the Heat Exchanger between the Process liquid and the HTF

Name of Component Performance Criteria Preferred Location Shown here as

Sensor for Low-liquid level safety interlock (§ 9.6 ). (process liquid)

Prevent exposure of heated area & liquid overtemperature safety interlock (if used)

In the process vessel, above the liquid overtemperature safety interlock (if used)

Probe in process vessel, near the process liquid surface

Sensor for liquid overtemperature safety interlock (§ 9.4 ) (process liquid)

Prevent overheating of the process liquid or exceeding the maximum service temperature of the material used in the heated area

In the process vessel

If used to protect the material of the heated area, it should be located near the top of the heated area.

Probe in process vessel, extending below the probe for the low-liquid level safety interlock sensor, near the top of the heated area

Sensor for Low-liquid level safety interlock (§ 9.6 ) (HTF)


Heater/Circulator, located above heated area and liquid overtemperature safety interlock (if used)

Probe in Heater/Circulator unit, near the surface of the heated area, and above the liquid overtemperature safety interlock

Sensor for liquid overtemperature safety interlock (§ 9.4 ) (HTF)

Prevent overheating of the HTF or exceeding the maximum service temperature of the material used in the heated area

Heater/Circulator, located above heated area and below the low-liquid level safety interlock

Probe in Heater/Circulator unit, near the surface of the heated area, and below the low-liquid level safety interlock

Sensor for heater overtemperature safety interlock (§ 9.5 )

Prevent overheating of the heater or materials in thermally-conductive contact with the heater

In contact with the heated area of the heater

(See Figure A1-3 for more detail.)

Sensor on heated area of immersion heater located in the Heater/Circulator unit

Sensor for liquid flow safety interlock (§ 9.7 ) (HTF)

Prevent overheating if heater requires forced convection

Return line to Heater/Recirculator –placed in this location to guard against loss of flow from upstream leaks

Sensor in return line from process vessel


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A1-4 Typical Heated Liquid Heat Exchanger, where a Stand-Alone Counterflow Heat Exchanger is Being Used as a Heat Exchanger between the Process liquid and the HTFA1-4.1 Figure A1-3 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-3.

Heat Transfer Fluid(HTF)

Sensor for liquid overtemperature

Sensor for low-liquidlevel safety interlock

Pump

Sensor for liquid

(process chem.)

flow safetyinterlock

safety interlock (HTF)

HeatExchanger

ProcessVessel

Process Chemical

flow safety

Heater / Circulator(HTF)Unit

interlock(HTF)

Sensor for heater overtemperature

Sensor for liquid temparaturesafety interlock

(process chem.)Heated area

Sensor for liquid

safety interlock

Heated Area(HTF)

Figure A1-3 Typical Heated Liquid Heat Exchanger, where a Stand-Alone Counterflow Heat Exchanger is Being Used as

a Heat Exchanger between the Process liquid and the HTF

A1-4.2 The process vessel in this drawing is of single-wall construction. The process liquid (¶ 5.2.28 ) flows over a four-sided weir, where it is collected and pumped through a remote heat exchanger and back into the process vessel. The volume of the weir also serves as a reservoir for a reserve volume of the process liquid to accommodate for evaporation and process drag-out.

A1-4.3 The heat exchanger shown is a shell and tube type of dual loop heat exchanger (¶ 6.3.2.1 ). The process liquid (¶ 5.2.28 ) flows into a chamber on the end, where it is distributed through several small tubes that pass through a bath of HTF, which is pumped from the Heater/Circulator Unit. A1-4.4 This unit combines the heater, process temperature controller and circulating pump for the HTF. The HTF is heated in a vessel that contains an electrical resistive element heater (¶ 6.3.3 ). An immersion heater (¶ 6.3.3.1.2 ) is depicted; however other heaters may be used. This integrated component could be replaced by individual components (heater, process temperature controller, pump, etc.).


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lA1-4.5 The heater shown is a typical immersion heater (¶ 6.3.3.1.2 ). It consists of two power leads and a grounded metallic sheath. The upright sections of the heater are intended to conduct electrical current only. No heat is intended to be generated or transferred in these areas. The heated area (¶ 5.2.18 ) is confined to the sections of the heater that lie in the horizontal plane.A1-4.6 Table A1-4 provides more details on the interlocks and safety features of such a system.

Table A1-1 Interlocks & Safety Features, Typical Heated Liquid Heat Exchanger, where a Stand-Alone Counterflow Heat Exchanger is Being Used as a Heat Exchanger between the Process liquid and the HTF


Sensor for liquid overtemperature safety interlock (§ 9.4 ) (process liquid)#1


In the remote heat exchanger at the discharge side for the process liquid

Probe in the remote heat exchanger discharge side for the process liquid

Sensor for liquid flow safety interlock (§ 9.7 ) (process liquid)

Prevent overheating of the HTF, from the loss of heat transfer through the heated area for the process liquid

Return line to the process vessel to guard against loss of flow from upstream leaks

Sensor in return line from remote heat exchanger


Prevent exposure of heated area & liquid overtemperature safety interlock. (if used)


Probe in Heater/Circulator unit, near the surface of the heated area, and above the liquid overtemperature safety interlock




Probe in Heater/Circulator unit, near the surface of the heated area, and below the low-liquid level safety interlock




(See A1-4.1Figure A1-3 for more detail.)

Sensor on heated area of immersion heater located in the Heater / Circulator unit

Sensor for liquid flow safety interlock (§ 9.7 ) (HTF)

Prevent overheating if heater requires forced convection

Return line to Heater/Recirculator –placed in this location to guard against loss of flow from upstream leaks

Sensor in return line from process vessel

#1 A low-liquid level safety interlock is not needed for this system. The weir provides a location for the storage of a reserve volume of the process liquid to accommodate loss through evaporation and drag-out. While a level detector here could detect chemical loss and subsequent loss of flow, a liquid flow safety interlock provides superior protection in its ability to detect loss of flow (e.g., from a pump malfunction).


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A1-5 Typical Heated Liquid Heat Exchanger, where an Integral Heater is being Used to Heat the HTF, and Heat is Exchanged between the HTF and the Heated Process liquids through the Vessel WallsA1-5.1 Figure A1-5 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify the Figure A1-5.

Liquid level (process chemical)(process chemical)

Sensor for low-liquid level safety interlock (process chemical)

Sensor for liquid overtemperature safety interlock (HTF)

Sensor for low-liquid level safety interlock (HTF)

Sensor for heater overtemperature safety interlock

Heat Transfer Fluid (HTF)

ProcessVessel

Heated area

Sensor for liquid overtemperature safety interlock (process chemical)

Figure A1-3 Typical Heated Liquid Heat Exchanger, where an Integral Heater is being Used to Heat the HTF, and Heat is

Exchanged between the HTF and the Heated Process liquids through the Vessel Walls

A1-5.2 The process vessel is of double-wall construction. A separate jacket is provided around the vessel, slightly below the process liquid level. The HTF is heated by an immersion heater placed in the outer jacket below the process vessel, and heats the HTF by conduction and free convection. Heat is transferred from the HTF to the process liquid through the inner vessel walls.A1-5.3 Table A1-5 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-2 Interlocks & Safety Features, Typical Heated Liquid Heat Exchanger, where an Integral Heater is being used to Heat the HTF, and Heat is exchanged between the HTF and the Heated Process liquids through the Vessel Walls


Sensor for Low-liquid level safety interlock (§ 9.6 ) (process liquid)


In the process vessel, above the liquid overtemperature safety interlock (if used)

Probe in process vessel, near the process liquid surface

Sensor for liquid overtemperature safety interlock (§ 9.4 ) (process liquid)


In the process vessel

If used to protect the material of the heated area, it should be located near the top of the heated area.

Probe in process vessel, extending below the probe for the low-liquid level safety interlock sensor, near the top of the heated area.


Prevent exposure of heated area and liquid overtemperature safety interlock (if used)


Probe in outer chamber of process vessel, near the surface of the heated area, and above the liquid overtemperature safety interlock




Probe in outer chamber of process vessel, near the surface of the heated area, and below the low-liquid level safety interlock




(See A1-5.1Figure A1-3 for more detail.)

Sensor on heated area of immersion heater located in the outer shell of the process vessel


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A1-6 Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater – Immersion Heater (¶ 6.3.3.1.2 )A1-6.1 Figure A1-6 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-6.

Rod-type immersion heater

Sensor for liquid overtemperaturesafety interlock

Heated LiquidSensor for low-liquid levelsafety interlock

Figure A1-3 Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Thermally

Conductive Heater – Immersion Heater (¶ 6.3.3.1.2 )

A1-6.2 The process vessel in this drawing is a simple tank. Immersion heaters are used to heat the process liquid. Three heaters are shown in this configuration, installed through the vessel wall and cantilevered above the vessel floor.

A1-6.3 The heaters shown are typical cartridge-type immersion heaters (¶ 6.3.3.1.2 ). A detailed drawing of this heater is shown in Figure A1-7. The heating element (¶ 5.2.20 ) is contained in a grounded metallic sheath. The heater is inserted into the process vessel by means of a liquid-tight fitting that is located in the unheated area of the heater. A1-6.4 Table A1-6 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-3 Interlocks & Safety Features, Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater – Immersion Heater (¶ 6.3.3.1.2 )


Sensor for Low-liquid level safety interlock (§ 9.6 )


Process vessel, located above heated area and liquid overtemperature safety interlock (if used)

Probe in process vessel, low in the vessel, above the liquid overtemperature safety interlock

Sensor for liquid overtemperature safety interlock (§ 9.4 )


In the process vessel, above the plane of the immersion heaters, but below the sensor for the low-liquid level safety interlock

Probe in the process vessel, just above the upper plane of the immersion heaters


Prevent overheating of the heater or materials in thermally conductive contact with the heater

See A1-7.1Figure A1-3.

See A1-7.1Figure A1-3. See A1-7.1Figure A1-3.


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A1-7 Immersion HeaterA1-7.1 Figure A1-7 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-7.

Rod Heater enlarged above

Sensor for low-liquid levelsafety interlock Sensor for liquid overtemperature

safety interlockHeater

Sensor for heater overtemperatureGrounded conductive sheath

Heating Element

safety interlock

Heated Area

Figure A1-3 Immersion Heater Detail

A1-7.2 Figure A1-7 shows the detail of a rod type immersion heater. The heater consists of a heated area (¶ 5.2.18 ) intended to transfer heat to the process liquid, and an unheated section, where it is inserted in the vessel containing the process liquid and sealed by means of a tapered thread at the end of the unheated section. A grounded, conductive sheath is provided to prevent electrical energization of the process liquid. A1-7.3 Table A1-7 provides more details on the interlocks and safety features of such an immersion heater.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-4 Interlocks & Safety Features, Immersion Heater Detail








In the process vessel, above the plane of the immersion heaters, but below the sensor for the low-liquid level safety interlock



Prevent overheating of the heater or materials in thermally conductive contact with the heater

Within the heated area of the heater

Probe attached to the inner surface of the heater sheath


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A1-8 Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater – External (Blanket) Heater (¶ 6.3.3.1.2 )A1-8.1 Figure A1-8 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-8.

Sensor for heater overtemperature safety interlock

Process Vessel

Vessel WallHeated Liquid

Sensor for low-liquid level safety interlock

Sensor for liquid overtemperature safety interlock

Heating ElementHeater &

Figure A1-3 Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 )– Thermally

Conductive Heater – External (Blanket) Heater (¶ 6.3.3.1.2 )

A1-8.2 The process vessel in this drawing is a simple tank. An external (blanket) heater (¶ 6.3.3.1.2 ) is bonded to the vessel walls.A1-8.3 The heater shown is an external heater bonded to the outside of the process vessel’s walls, the entire surface of the heater is used to generate heat; thus the heater and heating element are the same (with the exception of the wire leads) in this configuration. The process liquid level in the vessel is even with the top edge of the heater. A1-8.4 Table A1-8 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-5 Interlocks & Safety Features, Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater – External (Blanket) Heater (¶ 6.3.3.1.2 )



Prevent exposure of heated area and liquid overtemperature safety interlock (if used)

In the process vessel, above the heated area

Probe in the process vessel, located just above the top edge of the blanket heater


Prevent overheating of the process liquid or exceeding the maximum service temperature of the materials used in the heated area

In the process vessel, close to the heated area

Probe in the process vessel, close to the heated area

In this application, the height of the sensor (as long as it is below the low-liquid level sensor) is not critical



Within the heater or between the heater and outer surface of the process vessel

Probe between the heater and the outer surface of process vessel


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A1-9 Typical Remote Heater (¶ 5.2.34 ) using an Electrical Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater - Immersion Heaters (¶ 6.3.3.1.2 )A1-9.1 Figure A1-9 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-9.

Area enlarged above

safety interlockSensor for liquid flow

Inlet

Heater

Sensor for liquid overtemperaturesafety interlock

Heated Liquid

Heated Area

Outlet

Figure A1-3 Typical Remote Heater (¶ 5.2.34 ) using an Electrical Resistive Element Heater (¶ 6.3.3 ) – Thermally

Conductive Heater - Immersion Heaters (¶ 6.3.3.1.2 )

A1-9.2 The vessel depicted in Figure A1-9 is meant to contain a liquid flowing through it for the purposes of heating the liquid. The liquid enters from the bottom left of the vessel and exits from the top right. The inlet and outlet are unrestricted and sized to prevent pressurization in the event of boiling. The vessel incorporates a heater that is installed in the right side of the vessel and is described below. A1-9.3 The heater assembly is a bundle of rod heaters (See A1-7.1Figure A1-3 for details of individual heaters.) that is inserted as a unit into the right side of the vessel. A1-9.4 Table A1-9 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-6 Interlocks & Safety Features, Typical Remote Heater (¶ 5.2.34 ) using an Electrical Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater - Immersion Heaters (¶ 6.3.3.1.2 )




In the remote heater near the discharge port

Probe in the remote heater above the heater bundle near the discharge port

Sensor for liquid flow safety interlock (§ 9.7 )

Prevent overheating of the process liquid or the remote heater from the loss of heat transfer due to the lack of forced convection


Sensor on outlet line from remote heater



Within the heated area of the heater

Not shown



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A1-10 Typical Remote Heater (¶ 5.2.34 ) using an Electrical Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater - External Heater (¶ 6.3.3.1.2 )A1-10.1 Figure A1-10 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-10.

Area enlarged aboveSensor for liquid flow

safety interlock

(Heated Area & Heating Element)

Inlet

Heater

Sensor for liquidovertemperature safety interlock

Sensor for heater overtemperature safety interlockHeated Liquid

Outlet

Figure A1-3 Typical Remote Heater (¶ 5.2.34 ) using an Electrical Resistive Element Heater (¶ 6.3.3 ) – Thermally

Conductive Heater - External Heater (¶ 6.3.3.1.2 )

A1-10.2 The vessel depicted in Figure A1-10 is meant to contain a liquid flowing through it for the purposes of heating the liquid. The liquid enters from the bottom left of the vessel and exits from the top right. The inlet and outlet are unrestricted and sized to prevent pressurization in the event of boiling. The vessel is constructed from a thermally-conductive material, and an external blanket-type heater is bonded to its exterior. A1-10.3 The heater is an external blanket type bonded to the outer surface of the vessel. A1-10.4 Table A1-10 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-7 Interlocks & Safety Features, Typical Remote Heater (¶ 5.2.34 ) using an Electrical Resistive Element Heater (¶ 6.3.3 ) – Thermally Conductive Heater - External Heater (¶ 6.3.3.1.2 )




In the remote heater near the discharge port

Probe in the remote heater near the discharge port







Within the heater or between the heater and outer surface of the remote heater

Probe between the heater and the outer surface of the remote heater


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A1-11 Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Radiant Heater (¶ 6.3.3.1.3 )A1-11.1 Figure A1-11 shows of a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-11.

Sensor for inerting interlock

Sensor for liquid overtemperatureRadiant energy shield

safety interlock

Radiant Heater

InletInerting

Sensor for low-liquid levelsafety interlock

Heated Liquid

Figure A1-3 Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – – Radiant Heater

(¶ 6.3.3.1.3 )

A1-11.2 The process vessel in Figure A1-11 is a simple tank. Radiant heaters (¶ 6.3.3.1.3 ) are used to heat the process liquid. Three heaters are shown in this configuration, installed through the vessel wall and cantilevered above the vessel floor.

A1-11.3 The heaters shown are typical cartridge-type radiant heaters (¶ 6.3.3.1.3 ). A detailed drawing of this heater is shown in Figure A1-12. The spiral heating element (¶ 5.2.20 ) is contained in a quartz radiant heater sheath. The heater is inserted into the process vessel by means of a compression fitting that is located in the unheated area of the heater. An inlet and outlet port for inert gas flow is provided if the heater is to be used for combustible or flammable process liquids. A1-11.4 Table A1-11 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-8 Interlocks & Safety Features, Typical Heated Process Vessel using an Electrically Resistive Element Heater (¶ 6.3.3 ) – Radiant Heater (¶ 6.3.3.1.3 )








In the process vessel, above the plane of the radiant heaters, but below the sensor for the low-liquid level safety interlock

If the sensor is in the line of sight of the heaters it may require shielding to prevent radiant heating of the sensor and resulting false high readings.

Probe in the process vessel, just above the upper plane of the immersion heaters

Note the semi-cylindrical shield placed around the probe to prevent radiant heating of the probe.

Sensor for inerting flow safety interlock (§ 9.9.2 )

Measure inert gas flow through heater free spaces

Outlet from inerted space

If multiple heaters are used (as shown), the inert gas supply system should be piped in series among the heaters for each vessel. As shown, one sensor after the last heater is then sufficient to monitor flow for the supply to multiple heaters. A break in the system will result in a measurable drop in flow at the point shown.

Exit from inert gas outlet manifold


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A1-12 Typical Radiant HeaterA1-12.1 Figure A1-12 shows a representative radiant heater. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-12.

Compression Fitting

safety interlockSensor for liquid overtemperature

Radiant heater enlarged above

Sensor for low-liquid levelsafety interlock Heated Area

Heater

Quartz Sheath

Heating Element

Inerting Tube

Figure A1-3 Typical Radiant Heater

A1-12.2 Figure A1-12 shows the detail of a rod type radiant heater. The heater consists of a thin conductive wire, used as a heating element (¶ 5.2.20 ) in a quartz radiant heater sheath and a compression fitting to make a leak-tight seal when installed in a vessel. When energized, the heating element glows and transfers heat to the process liquid by radiant energy. This design leads to a significant free space in the heater. When used with flammable or combustible liquids, the combination of an oxygenated atmosphere and a glowing heating element could lead to ignition of the process liquid. Also shown in Figure A1-12 is an inerting tube. An inert gas is fed through the inerting tube then returns along the free space of the heater to an outlet port at the end of the heater where it enters the vessel. A1-12.3 Table A1-12 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-9 Interlocks & Safety Features, Typical Radiant Heater




Used in conjunction with this heater

Located within the vessel in which this heater is located, above the area where the heaters are located





Used in conjunction with this heater

Located in the process vessel, above the plane of the radiant heaters, but below the sensor for the low-liquid level safety interlock

If the sensor is in the line of sight of the heaters it may require shielding to prevent radiant heating of the sensor and resulting false high readings.


Probe in the process vessel, just above the upper plane of the radiant heaters

A semi-cylindrical shield is placed between the probe and the radiant heaters to prevent radiant heating of the probe.

Sensor inerting safety interlock (§ 9.9.2 )


Outlet from inerted space



A sensor on the exit from inert gas outlet manifold


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A1-13 Typical Remote Heater (¶ 5.2.34 ) using Electrical Resistive Element Heaters (¶ 6.3.3 ) - Radiant Heaters (¶ 6.3.3.1.3 )A1-13.1 Figure A1-13 shows a representative system. Unless noted below, construction techniques, features, component locations, etc. are not required elements for equipment acceptance. The following description is provided only to clarify Figure A1-13.

Figure A1-3 Typical Remote Heater (¶ 5.2.34 )using Electrical Resistive Element Heaters (¶ 6.3.3 ) - Radiant Heaters

(¶ 6.3.3.1.3 )

A1-13.2 In Figure A1-13, the vessel is meant to contain a liquid flowing through it for the purposes of heating the liquid. The liquid enters from the bottom left of the vessel and exits from the top right. The inlet and outlet are unrestricted and sized to prevent pressurization in the event of boiling. The vessel incorporates a heater that is installed in the right side of the vessel and is described below. A1-13.3 The heater assembly is a bundle of radiant rod heaters (see Fig. A1-12 for details of the individual heaters) that is inserted as a unit into the right side of the vessel. A1-13.4 Table A1-13 provides more details on the interlocks and safety features of such a system.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A1-10 Interlocks & Safety Features, Typical Remote Heater (¶ 5.2.34 ) using Electrical Resistive Element Heaters (¶ 6.3.3 ) - Radiant Heaters (¶ 6.3.3.1.3 )




In the remote heater, above the radiant heaters

If the sensor is in the line of sight of the heaters, it may require shielding to prevent radiant heating of the sensor and resulting false high readings.

Probe in the remote heater above the heater bundle near the discharge port. Note the semi-cylindrical shield placed around the probe to prevent radiant heating of the probe.





Sensor inerting safety interlock (§ 9.9 )


Outlet from inerted space.


A sensor on the exit from inert gas outlet manifold.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lAPPENDIX 2SAFETY PRACTICES AND INTERLOCKS FOR VARIOUS EQUIPMENT CONFIGURATIONS AND USESNOTICE: The material in this Appendix is an official part of SEMI S3 and was approved by full letter ballot procedures on November 29, 2005.

A2-1.1 Instructions for Use of Tables — Using the table(s) selected in accordance with § 8.2 , consider whether each of the characteristics in the left column pertains to the PLHS you are considering. For each characteristic in the left column that does pertain to the PLHS you are considering, the PLHS should incorporate the safety features described in the right column of that row. 50: The parenthetical references are to the locations in this document at which the safety features are described.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-1a Heated Liquid Heat Exchange Systems Using Flammable HTF

Heat Transfer Fluid and Heating System Characteristics Safety Features

Any High temperature metal construction (§ 9.11 )

Neither inerting nor purging of the headspace of the vessel containing the HTF

Certification for use in hazardous locations (¶ 9.15 )

Inerting#1 (§ 9.9 ) of the headspace of the vessel containing the HTF

Inerting Safety Interlock (§ 9.9.2 )

Purging (§ 9.10 ) of the headspace of the vessel containing the HTF

Purging Safety Interlock (¶ 9.10.2 )

Personnel can come into electrical contact with the HTF, either by direct contact or contact through a ungrounded conductive path to the HTF; and the heating system can, in a reasonably foreseeable single-point failure, cause the HTF to be at a hazardous potential (voltage).

Protection of personnel from the risk of electrical shock (§ 9.12 )

Flow dependent system. (¶ 6.4.1.2 ) Liquid Flow Safety Interlock (§ 9.7 )

Closed vessel & Heating system capable of exceeding the boiling point of the HTF.

Overpressure Protection (§ 9.8 )ORLiquid Overtemperature Safety Interlock (§ 9.4 ) with a setpoint at or below the boiling point - 10°C

Heater has sufficient power#2to exceed the HDT of the HTF, or the HTF's autoignition temperature minus 50°C, even when the heated area is fully covered by HTF. However, the HTF is not intentionally boiled.

Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )

Heater has sufficient power#2 to exceed the HDT of the HTF, or the HTF's autoignition temperature minus 50°C, even when the heated area is fully covered by HTF. The heating system is flow independent and HTF is intentionally boiled.

Low Liquid Level Safety Interlock (§ 9.6 )

Heater has sufficient power#2 to exceed the HDT of the HTF, or the HTF's autoignition temperature minus 50°C, if the heated area is not fully covered by HTF.

Heated Area Overtemperature Safety Interlock (§ 9.5 )Low Liquid Level Safety Interlock (§ 9.6 )

Failure of radiant heater sheath or any other single component would cause HTF or its vapor to contact heating element

Inerting of interstitial space between heating filament and radiant heater sheath, with heater power interlocked to inert gas flow.#3 (§ 9.9 )

Heater has sufficient power#2, if the heated area is submerged, to damage itself or, through conduction of heat through solid components, to cause a component or material of construction to exceed its maximum service temperature.

Heater Overtemperature Safety Interlock (§ 9.5 )

Heater has sufficient power#2, if the heated area is not submerged, to damage itself or, through conduction of heat through solid components, to cause a component or material of construction to exceed its maximum service temperature.

Heater Overtemperature Safety Interlock (§ 9.5 )orLow Liquid Level Safety Interlock (§ 9.6 )

Radiant heater used to heat the HTF Shielding from radiant heating (§ 9.13 )#1: Inerting may not be effective with HTFs containing oxygen, which may be liberated on decomposition.#2: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).#3: If radiant heaters are used for heating flammable or combustible liquid chemicals, suitable means of preventing them from becoming an ignition source should be provided because the surface temperature of the radiant heating element is usually above the autoignition temperature for these chemicals.

51: Liquid heat exchange systems are shown in Figure A1-3, Figure A1-3, and Figure A1-3 in Appendix 1.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-1b Heated Liquid Heat Exchange Systems Using Combustible HTF

Heat Transfer Fluid and Heating System Characteristics Safety Features

Any Liquid Overtemperature Safety Interlock (§ 9.4 )


Protection of personnel from the risk of electrical shock (§ 9.12)




Heater has sufficient power#1 to exceed the HDT of the HTF, yielding non-flammable degradation products, even when the heated area is fully covered by the HTF.


Heater has sufficient power#1 to exceed the HDT of the HTF, yielding non-flammable degradation products, if the heated area is not fully covered by the HTF.


Failure of radiant heater sheath or any other single component would cause HTF or its vapor to contact heating element


Radiant heater use to heat the HTF Shielding from radiant heating (§ 9.13 )





Heater has sufficient power#1 to heat the HTF to FP-10 Liquid Overtemperature Safety Interlock (§ 9.4 )

Heater has sufficient power#1 to reach FDT-10 at the heated area when submerged.

Heated Area Overtemperature Interlock (§ 9.14 )

Heater has sufficient power#1 to reach FDT-10 at the heated area when it is not submerged.

Low Liquid Level Safety Interlock (§ 9.6 )or Heated Area Overtemperature Interlock (§ 9.14 )

#1: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).#2: If radiant heaters are used for heating flammable or combustible liquid chemicals, suitable means of preventing them from becoming an ignition source should be provided because the surface temperature of the radiant heating element is usually above the autoignition temperature for these chemicals.



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-1c Heated Liquid Heat Exchange Systems Using Noncombustible HTF

Heat Transfer Fluid Properties and Heating System Characteristics

Safety Features






Heater has sufficient power#1 to exceed the HDT of the HTF, yielding non-flammable degradation products, even when the heated area is fully covered by the HTF.


Heater has sufficient power#1 to exceed the HDT of the HTF, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid. However, the HTF is not intentionally boiled.


Heater has sufficient power#1 to exceed the HDT of the HTF, yielding non-flammable degradation products, if the heated area is not fully covered by the HTF. The heating system is flow independent and the HTF is intentionally boiled.










Radiant heater used to heat the HTF Shielding from radiant heating (§ 9.13 )#1: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-2a Flammable Process Liquid Heated by Heated Liquid Heat Exchange Systems

Process Liquid Properties and Heating System Characteristics Safety Features


Neither inerting nor purging of the headspace of the vessel containing the process liquid

Certification for use in hazardous locations (§ 9.15 )

Inerting#1 (§ 9.9 ) of the headspace of the vessel containing the process liquid


Purging (§ 9.10 ) of the headspace of the vessel containing the process liquid


Personnel can come into electrical contact with the heated process liquid, either by direct contact or contact through a ungrounded conductive path to the liquid; and the heating system can, in a reasonably foreseeable single-point failure, cause the heated process liquid to be at a hazardous potential (voltage).



Closed vessel & Heating system capable of exceeding the boiling point of the process liquid.


Heat exchange system has sufficient power#2, if the heated area is submerged, to damage itself or, through conduction of heat through solid components, to cause a component or material of construction to exceed its maximum service temperature.

Heat Exchanger Overtemperature Safety Interlock (§ 9.16 )

Heat exchange system has sufficient power#2, if the heated area is not submerged, to damage itself or, through conduction of heat through solid components, to cause a component or material of construction to exceed its maximum service temperature.

Heat Exchanger Overtemperature Safety Interlock (§ 9.16 )orLow Liquid Level Safety Interlock (§ 9.6 )

HTF can exceed#3 the HDT#4 or autoignition temperature minus 50C of the process liquid, even when the heated area is fully covered by process liquid. However, the process liquid is not intentionally boiled.


HTF can exceed#3 the HDT#4 or autoignition temperature minus 50C of the process liquid, even when the heated area is fully covered by process liquid. The heating system is flow independent and process liquid is intentionally boiled.


HTF can exceed#3 the HDT#4 or autoignition temperature minus 50C of the process liquid, if the heated area is not fully covered by process liquid.


#1: Inerting may not be effective with process liquids containing oxygen, which may be liberated on decomposition.#2: The phrase "heat exchange system has sufficient power" refers to the power of the heater used to heat the HTF, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater or HTF temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heated area is submerged, the liquid's properties are also to be considered. For situations in which the heated area is not submerged, the heated area should be considered to be in air (or purging or inerting gas, if appropriate).#3: The phrase "HTF can exceed" refers to the temperature the HTF can achieve based on the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater or HTF temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heated area is submerged, the liquid's properties are also to be considered. For situations in which the heated area is not submerged, the heated area should be considered to be in air (or purging or inerting gas, if appropriate).#4 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.

54: Systems in which the process liquid is heated by a liquid heat exchanger are shown in Figure A1-3, Figure A1-3, and FigureA1-3 in Appendix 1.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-2b Combustible Process Liquid Heated by Heated Liquid Heat Exchange Systems


Any Liquid Overtemperature Safety Interlock (§ 9.4 )




Closed vessel & heating system capable of exceeding the boiling point of the process liquid.


HTF can exceed#1 the HDT#2 of the process liquid, yielding non-flammable degradation products, even when the heated area is fully covered by the process liquid.

Liquid Overtemperature Safety Interlock (§ 9.4 )






Heat exchange system has sufficient power#3 to heat the process liquid to FP-10

Liquid Overtemperature Safety Interlock (§ 9.4 )

Heat exchange system has sufficient power#3 to reach FDT-10 at the heated area when it is submerged.


Heat exchange system has sufficient power#3 to reach FDT-10 at the heated area when it is not submerged


#1: The phrase "HTF can exceed" refers to the temperature the HTF can achieve based on the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater or HTF temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heated area is submerged, the liquid's properties are also to be considered. For situations in which the heated area is not submerged, the heated area should be considered to be in air (or purging or inerting gas, if appropriate).#2 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.#3: The phrase "heat exchange system has sufficient power" refers to the power of the heater used to heat the HTF, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater or HTF temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heated area is submerged, the liquid's properties are also to be considered. For situations in which the heated area is not submerged, the heated area should be considered to be in air (or purging or inerting gas, if appropriate).



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-2c Noncombustible Process Liquid Heated by Heated Liquid Heat Exchange Systems







HTF can exceed#1 the HDT#2 of the process liquid, yielding non-flammable degradation products, even when the heated area is fully covered by process liquid. However, the process liquid is not intentionally boiled.


HTF can exceed#1 the HDT#2 of the process liquid, yielding non-flammable degradation products, even when the heated area is fully covered by process liquid. The heating system is flow independent and the process liquid is intentionally boiled.


HTF can exceed#1 the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by process liquid.






Heat exchange system has sufficient power#3 to reach FDT-10 at the heated area when it is submerged.


Heat exchange system has sufficient power#3 to reach FDT-10 at the heated area when it is not submerged


#1: The phrase "HTF can exceed" refers to the temperature the HTF can achieve based on the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater or HTF temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heated area is submerged, the liquid's properties are also to be considered. For situations in which the heated area is not submerged, the heated area should be considered to be in air (or purging or inerting gas, if appropriate).#2 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.#3: The phrase "heat exchange system has sufficient power" refers to the power of the heater used to heat the HTF, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater or HTF temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heated area is submerged, the liquid's properties are also to be considered. For situations in which the heated area is not submerged, the heated area should be considered to be in air (or purging or inerting gas, if appropriate).



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-3a Flammable Process Liquid Heated by Thermally Conductive Heaters








Purging Safety Interlock (§ 9.10.2 )






Heater has sufficient power#2 to exceed the HDT#3 or autoignition temperature minus 50C of the process liquid, even when the heated area is fully covered by the process liquid. However, the process liquid is not intentionally boiled.

Heated Area Overtemperature Safety Interlock (§ 9.5 )Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )

Heater has sufficient power#2 to exceed the HDT#3 or autoignition temperature minus 50C of the process liquid, even when the heated area is fully covered by the process liquid. The heating system is flow independent and the process liquid is intentionally boiled.


Heater has sufficient power#2 to exceed the HDT#3 or (autoignition temperature - 50C) of the process liquid, if the heated area is not fully covered by the process liquid.






#1: Inerting may not be effective with process liquids containing oxygen, which may be liberated on decomposition.#2: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).#3 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.

57: Systems incorporating immersion heaters are shown in Figure A1-3, Figure A1-3, and Figure A1-3 in Appendix 1.58: Systems incorporating external heaters are shown in Figure A1-3 and Figure A1-3 in Appendix 1.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-3b Combustible Process Liquid Heated by Thermally Conductive Heaters





Closed vessel and Heating system capable of exceeding the boiling point of the process liquid.


Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, even when the heated area is fully covered by the process liquid.

Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )Heated Area Overtemperature Safety Interlock

(§ 9.5 )

Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid.

Heated Area Overtemperature Safety Interlock

(§ 9.5 )Low Liquid Level Safety Interlock (§ 9.6 )





Heater has sufficient power#1 to heat the process liquid to FP-10 Liquid Overtemperature Safety Interlock (§ 9.4 )





#1: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).#2 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.59: Systems incorporating immersion heaters are shown in Figure A1-3, Figure A1-3, and Figure A1-3 in Appendix 1.60: Systems incorporating external heaters are shown in Figure A1-3 and Figure A1-3 in Appendix 1.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-3c Noncombustible Process Liquid Heated by Thermally Conductive Heaters








Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )Heated Area Overtemperature Safety Interlock (§ 9.5 )

Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid. However, the process liquid is not intentionally boiled.


Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid. The heating system is flow independent and the process liquid is intentionally boiled.

Low Liquid Level Safety Interlock (§ 9.6 )Heated Area Overtemperature Safety Interlock (§ 9.5 )









#1: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).#2 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.

61: Systems incorporating immersion heaters are shown in Figure A1-3, Figure A1-3, and Figure A1-3 in Appendix 1.62: Systems incorporating external heaters are shown in Figure A1-3 and Figure A1-3 in Appendix 1.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-4a Flammable Process Liquid Heated by Radiant Heaters



Failure of radiant heater sheath or any other single component would cause process liquid or its vapor to contact heating element




Inerting#2 of the headspace of the vessel containing the process liquid (§ 9.9 )


Purging of the headspace of the vessel containing the process liquid (§ 9.10 )








Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )Shield surroundings from radiant heatingHeated Area Overtemperature Safety Interlock (§ 9.5)


Low Liquid Level Safety Interlock (§ 9.6 )Shield surroundings from radiant heatingHeated Area Overtemperature Safety Interlock (§ 9.5)

Heater has sufficient power#3 to exceed the HDT#4 or autoignition temperature minus 50C of the process liquid, if the heated area is not fully covered by the process liquid.

Low Liquid Level Safety Interlock (§ 9.6 )Shielding from radiant heating (§ 9.13 )Heated Area Overtemperature Safety Interlock (§ 9.5)





#1: If radiant heaters are used for heating flammable or combustible liquid chemicals, suitable means of preventing them from becoming an ignition source should be provided because the surface temperature of the heating element is usually above the autoignition temperature for these chemicals. #2: Inerting may not be effective with process fluids containing oxygen, which may be liberated on decomposition.#3: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l#4 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.

63: Systems incorporating radiant heaters are shown in Figure A1-3, Figure A1-3 , and Figure A1-3 in Appendix 1.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-4b Combustible Process Liquid Heated by Radiant Heaters


Failure of radiant heater sheath or any other single component would cause process liquid or its vapor to contact heating element







Heating element may cause a maximum service temperature of a component or surrounding material to be exceeded through the absorption of radiant energy.

Shielding from radiant heating (§ 9.13 )










#1: If radiant heaters are used for heating flammable or combustible liquid chemicals, suitable means of preventing them from becoming an ignition source should be provided because the surface temperature of the radiant heating element is usually above the autoignition temperature for these chemicals. #2: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lTable A2-4c Noncombustible Process Liquid Heated by Radiant Heaters







Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, even when the heating area is fully covered by the process liquid. However, the process liquid is not intentionally boiled.


Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, even when the heating area is fully covered by the process liquid. The heating system is flow independent and the process liquid is intentionally boiled.


Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid. However, the process liquid is not intentionally boiled.


Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid. The heating system is flow independent and the process liquid is intentionally boiled.


Heating element may cause a maximum service temperature of a component or surrounding material to be exceeded through the absorption of radiant energy.

Shielding from radiant heating (§ 9.13 )









#1: The phrase "heater has sufficient power" refers to the power of the heater, operated continuously at the available voltage and current, without regard for the controls (including safety interlocks) intended to limit the heater temperature. The materials of construction and the configuration of the PLHS are to be considered. For situations in which the heater is submerged, the liquid's properties are also to be considered. For situations in which the heater is not submerged, the heater should be considered to be in air (or purging or inerting gas, if appropriate).#2 If it is necessary to exceed the HDT of the process liquid to perform the intended process function of the SME, then means, other than the Liquid Overtemperature Safety Interlock, may be used to achieve a level of Risk no greater than Low (as defined by SEMI S10 and S14). See § 8.3 for discussion of the selection of safety features other than by use of these tables. This Safety Guideline discusses mitigation of hazardous decomposition risks by temperature control. Other means of mitigation are outside the scope of this Safety Guideline, but may be found in others, such as SEMI S2 and SEMI S6.



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lRELATED INFORMATION 1 MISCELLANEOUS INFORMATIONNOTICE: This Related Information is not an official part of SEMI S3 and was derived from the work of task force members. This Related Information was approved for publication by letter ballot on November 29, 2005.

R1-1 Practices for the Design of Control Systems for Process Liquid Heating SystemsR1-1.1 Conditions that are necessary to ensure safe operation of PLHS should be monitored.R1-1.1.1 Energy should be supplied to liquid heating systems only when these conditions are within safe limits of operation.R1-1.2 Control schemes should be designed so that power to heating systems is removed under one of the following conditions: upon activation of certain sequences (e.g., draining the vessel); or when systems (e.g., circulation pump) that are used in conjunction with heating systems are deactivated.

R1-1.3 Drain and Heating System Controls — If actuation of a vessel’s drain sequence would result in a heating element overtemperature condition, then actuation of the vessel drain sequence should remove power from heating systems serving that vessel. Reapplication of power should be permitted following attainment of the “process” or “full” liquid level in the vessel. R1-1.4 Circulation Pump and Heating System Controls — Where liquid circulation is required for the safe operation of a liquid heating system, power to the heating system should be interlocked through the control circuit of that circulation pump.

R1-2 Impact on Related SystemsR1-2.1 The impact of a PLHS on related systems should be considered. Single-fault failures that could result in an unsafe condition as a consequence of operation of the PLHS should be considered and mitigated. For example, if a 10% 2-propanol (IPA) mixture with water is being mixed upstream of a liquid chemical system designed for noncombustible liquids; a dangerous condition could result if the flow of water failed. In this case the risk of feeding pure IPA to a heating system designed for a noncombustible liquid should be mitigated. In this case, the heating system could be designed to handle a flammable material or the valve controlling the flow of IPA could be interlocked to a flow switch monitoring the flow of water.

R1-3 Vapor Generation Calculation FormulaR1-3.1 The rate of vapor generation for systems intended to operate at ambient or near-ambient pressure may be estimated from the formula below:

(R1-1)

Where:Rate of Vaporization (M3/sec)Q = Total Heater Power (Watts)Tb = Boiling Temperature of Liquid (oC)P = Maximum Intended Vessel Pressure (kPa)Hv = Heat of Vaporization of Liquid (Kcal/mole)

R1-3.2 The vapors formed should be vented to an appropriate location consistent with their properties.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lRELATED INFORMATION 2 Examples of the Selection of Safety FeaturesNOTICE: This Related Information is not an official part of SEMI S3 and was derived from the work of task force members. This Related Information was approved for publication by letter ballot on November 29, 2005

R2-1 Example 1R2-1.1.1 A 20-liter PVDF pre-heat vessel (closed vessel) with grounded metal sheath immersion heaters used to heat a commercially available mixture of N-Methyl Pyrrolidone, Propylene Glycol and Tetramethylammonium hydroxide. The PLHS meets the definition in § 5 of a flow independent heater. A liquid overtemperature interlock that meets the S2 criteria for safety interlocks is used with a setpoint of 80ºC (176°F). The heater has sufficient power to heat the liquid at its surface, when the heater is submerged, to 200°C (392 °F). The heater contains both a heater overtemperature interlock and a heated area overtemperature interlock that meet the S2 criteria for safety interlocks, both with setpoints of 150ºC (302°F). The heater control circuit has a sensor that measures the sheath temperature and limits it, by software, to 150ºC (302°F). The PVDF from which the vessel is made has a maximum service temperature of 129ºC (264°F). R2-1.2 The relevant characteristics of the mixture and its componentsR2-1.2.1 According to the MSDS for this mixture:

Component CAS Number Flash Point Autoignition Temp. Decomposition Temp. Boiling Point

N-Methyl Pyrrolidone 872-50-4 93°C (199 °F) 270°C (518°F)

Propylene Glycol

Tetramethylammonium hydroxide

Mixture >165 °C (>329°F)

R2-1.2.2 The MSDS states that the mixture has the hazardous decomposition products: oxides of carbon and ammonia (a flammable gas), but does not specify the temperature at which such decomposition occurs. For the purpose of this example, the flammable decomposition temperature is assumed to be 195°C (392 °F). R2-1.2.3 Information available from other MSDS:

Component CAS Number Flash Point Autoignition Temp. Decomposition Temp.

Boiling Point

N-Methyl Pyrrolidone 872-50-4 93°C (199 °F) 346 °C (655°F) 202°C (396°F)

Propylene Glycol 57-55-6 99°C (210 °F) 371°C (700°F) 188.2°C (370°F)

Tetramethylammonium hydroxide#1

75-59-2 Not flammable Not flammable

#1: An MSDS for pure tetramethylammonium hydroxide is not readily available. The data are from an MSDS for a 25% aqueous solution of the material.

R2-1.2.4 The characteristics to be used in applying this Safety Guideline:

Component CAS Number Flash Point Autoignition Temp. Decomposition Temp.

Boiling Point

N-Methyl Pyrrolidone

872-50-4 93°C (199 °F) 270°C (518°F)(Lower of two values found in MSDS

195°C (392 °F)(From assumption)

188.2°C (370°F)


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lR2-1.3 Applying Figure 1 (Path is shown in shaded boxes and heavier line weight.):

Start

Is heatercapable of heating

liquid to> FP-10?

No

Treat ascombustible liquid

Yes

Are theretwo, separate

means, at least oneof which meets the S2 criteria forsafety interlocks, of limiting the

liquid temperature to< FP-10?

Yes

No Treat asflammable liquid

Is heatedarea capable of

exceeding FDT-10, if theheated area is fully covered

by the liquid?

No

Yes

Are theretwo, separate means,

at least one of which meets the S2criteria for safety interlocks, of limiting the

heated area temperature under suchconditions, to< FDT-10?

No

Yes

Does theliquid meet the definitionof “flammable liquid” in

Section 5?

Yes

No

Does theliquid meet the definition of“noncombustble liquid” in

Section 5?

No

Treat asnoncombustible liquidYes

R2-1.3.1 According to Figure 1, this is to be treated as a combustible liquid.R2-1.4 Referring to Table 2 (Relevant cells are shaded and in bold type.):

Heated Liquid Heating Method Liquid Properties Safety Feature Table















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R2-1.4.1 According to Table 1, Table A2-3b is to be used to select the safety features. On the copy below, the characteristics that pertain to this example have been shaded. R2-1.5 Referring to Table A2-3b (Relevant cells are shaded and in bold type.):





Closed vessel and Heating system capable of exceeding the boiling point of the process liquid.



Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )Heated Area Overtemperature Safety Interlock (§ 9.5)

Heater has sufficient power#1 to exceed the HDT#2 of the process liquid, yielding non-flammable degradation products, if the heated area is not fully covered by the process liquid.

Heated Area Overtemperature Safety Interlock

(§ 9.5 )Low Liquid Level Safety Interlock (§ 9.6 )










R2-1.5.1 Therefore, the safety features to be provided include (based on those listed as part of the example description and those identified by following the process described in § 8 ): grounded metal sheaths on the immersion heaters liquid overtemperature interlock that meets the S2 criteria for safety interlocks is used with a setpoint of 80ºC

(176°F) low liquid level safety interlock. heater overtemperature safety interlock. heated area overtemperature interlock that meets the S2 criteria for safety interlocks is used with a setpoint of

150ºC (302°F). overpressure protection or liquid overtemperature safety interlock with a setpoint at or below the boiling point -

10°C. As the liquid overtemperature safety interlock that is specified because of other considerations meets the latter of these choices, no means of overpressure protection is imposed as a criterion.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lR2-2 Example 2R2-2.1 A 20-liter PVDF pre-heat vessel (closed vessel) with immersion heaters used to heat the same commercially available mixture of N-Methyl Pyrrolidone, Propylene Glycol and Tetramethylammonium hydroxide as in Example 1. The PLHS meets the definition in § 5 of a flow independent heater. The liquid is not intentionally boiled. The heater is capable of heating the liquid to 150ºC (302°F). The heater has sufficient power to heat the liquid at its surface, when the heater is submerged, to 200°C (392 °F). The heater contains both a heater overtemperature interlock and a heated area overtemperature interlock that meet the S2 criteria for safety interlocks, both with setpoints of 150ºC (302°F). The heater control circuit has a sensor that measures the sheath temperature and limits it, by software, to 150ºC (302°F). No interlocks meeting the S2 criteria for safety interlocks have yet been included in the design. The intended operating range of the liquid temperature is unknown, but it is known that the liquid is not intended to be boiled. The PVDF from which the vessel is made has a maximum service temperature of 129ºC (264°F)R2-2.2 The relevant characteristics of the mixture and its components are as described aboveR2-2.3 Applying Figure 1 (Path is shown in shaded boxes and heavier line weight.)

Start


liquid to> FP-10?

No


Yes




Yes




by the liquid?

No

Yes




No

Yes


Section 5?

Yes

No


Section 5?

No


R2-2.3.1 According to Figure 1, this is to be treated as a flammable liquid.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lR2-2.4 Referring to Table 2 (Relevant cells are shaded and in bold type.):

Heated Liquid Heating Method Liquid Properties Safety Feature Table














R2-2.4.1 According to Table 1, Table A2-3a is to be used to select the safety features. On the copy below, the characteristics that pertain to this example have been shaded. R2-2.5 Referring to Table A2-3a (Relevant cells are shaded and in bold type.):















Heated Area Overtemperature Safety Interlock (§ 9.5 )Liquid Overtemperature Safety Interlock (§ 9.4 )Low Liquid Level Safety Interlock (§ 9.6 )



Heater has sufficient power#2 to exceed the HDT#3 or (autoignition temperature - 50C) of the process liquid, if the heated area is not fully covered by the process liquid.



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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lProcess Liquid Properties and Heating System Characteristics Safety Features





R2-2.5.1 Therefore, the safety features to be provided include (i.e., those identified by following the process described in § 8): High temperature metal construction (§ 9.11 ) (As PVDF is not a "high temperature metal", this vessel is

acceptable only if the criteria of the EXCEPTION to 9.11.1 are met, such as by placing the PVDF vessel inside a high temperature metal vessel or by providing secondary containment made of a high temperature metal.)

Certification for use in hazardous locations. (§ 9.15 ) Protection of personnel from the risk of electrical shock (§ 9.12 ) Overpressure Protection (§ 9.8 ) or liquid overtemperature safety interlock with a setpoint at or below the

boiling point - 10°C. As the liquid overtemperature safety interlock that is specified because of other considerations meets the latter of these choices, no means of overpressure protection is imposed as a criterion.

Heated Area Overtemperature Safety Interlock Heater overtemperature interlock Liquid Overtemperature Safety Interlock (§ 9.4 ) Low Liquid Level Safety Interlock (§ 9.6 )

R2-3 Example 3R2-3.1 A 20-liter PVDF pre-heat vessel (closed vessel) with immersion heaters used to heat the same commercially available mixture of N-Methyl Pyrrolidone, Propylene Glycol and Tetramethylammonium hydroxide as in Example 1. The PLHS meets the definition in §5 of a flow independent heater. The liquid is not intentionally boiled. The heater is capable of heating the liquid at its surface, when submerged, to 150ºC (302°F). The heater contains both a heater overtemperature interlock and a heated area overtemperature interlock that meet the S2 criteria for safety interlocks, both with setpoints of 150ºC (302°F). The heater control circuit has a sensor that measures the sheath temperature and limits it, by software, to 150ºC (302°F). No interlocks meeting the S2 criteria for safety interlocks have yet been included in the design. The intended operating range of the liquid temperature is 30ºC (86°F) to 80ºC (176°F). The heater is capable of maintaining the process liquid at 80ºC (176°F) with the heated area at or below 150ºC (302°F). The PVDF from which the vessel is made has a maximum service temperature of 129ºC (264°F)R2-3.2 The relevant characteristics of the mixture and its components are as described above.R2-3.3 Applying ¶ 8.1.4 , include a Liquid Overtemperature Safety Interlock with a maximum set point of 85ºC (185°F) and a Heated area Overtemperature Interlock with a maximum set point of 150ºC (302°F).R2-3.4 Applying Figure 1 (Path is shown in shaded boxes and heavier line weight.)


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lStart


liquid to> FP-10?

No


Yes




Yes




by the liquid?

No

Yes




No

Yes


Section 5?

Yes

No


Section 5?

No


R2-3.5 This remainder of this example is the same as Example 1.

R2-4 DiscussionR2-4.1 Although the equipment is similar in the three examples, there are substantial differences in the safety features that are criteria for conformance to this Safety Guideline.R2-4.2 In Example 1, the range of temperatures is restricted, so the process liquid is considered combustible and two burdensome safety features, high temperature metal construction and certification of the heating system components and equipment for use in a hazardous environment, are not included.R2-4.3 In Example 2, the temperature range is not as restricted, so those safety features are criteria for conformance to this Safety Guideline. Accepting this greater burden, however, allows the use of the equipment for a broader range of temperatures with the foreseen process liquid. It also allows a broader range of process liquids.R2-4.4 In Example 3, the use of a lower power heater results in a situation similar to the first example. The disadvantage is that a lower power heater will result in longer heating times and lower maximum temperatures, but less burdensome safety features than the in Example 2.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lNOTICE: SEMI makes no warranties or representations as to the suitability of the safety guideline(s) set forth herein for any particular application. The determination of the suitability of the safety guideline(s) is solely the responsibility of the user. Users are cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other relevant literature respecting any materials or equipment mentioned herein. These safety guidelines are subject to change without notice.

By publication of this safety guideline, Semiconductor Equipment and Materials International (SEMI) takes no position respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this safety guideline. Users of this safety guideline are expressly advised that determination of any such patent rights or copyrights, and the risk of infringement of such rights are entirely their own responsibility.


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SEMI S2-0310bENVIRONMENTAL, HEALTH, AND SAFETY GUIDELINE FOR SEMICONDUCTOR MANUFACTURING EQUIPMENT

This Safety Guideline was technically approved by the global Environmental Health & Safety Committee. This edition was approved for publication by the global Audits & Reviews Subcommittee on December 21, 2010. Initially available at www.semi.org in February 2011. Originally published in 1991; previously published July 2010.

NOTICE: Paragraphs entitled “NOTE” are not an official part of this safety guideline and are not intended to modify or supersede the official safety guideline. These have been supplied by the committee to enhance the usage of the safety guideline.

NOTICE: This document contains material that has been balloted and approved by the SEMI Environmental Health & Safety Committee, but is not immediately effective. This material and the date on which it becomes effective are included in Delayed Revisions Sections 1, 2, 3, 4 and 5. The provisions of this information are not an authoritative part of the document until their effective dates. The main body of SEMI S2-0310 remains the authoritative version. Some or all of the provisions of revisions not yet in effect may optionally be applied prior to the effective date, providing they do not conflict with portions of the authoritative version other than those that are to be revised or replaced as part of the deferred change, and are labeled accordingly. Material that is to be replaced by revisions that are not yet in effect is preceded by a NOTICE indicating its status.

1 Purpose1.1 This safety guideline is intended as a set of performance-based environmental, health, and safety (EHS) considerations for semiconductor manufacturing equipment.

2 Scope2.1 Applicability — This guideline applies to equipment used to manufacture, measure, assemble, and test semiconductor products.

2.2 Contents — This document contains the following sections:

1. Purpose

2. Scope

3. Limitations

4. Referenced Standards and Documents

5. Terminology

6. Safety Philosophy

7. General Provisions

8. Evaluation Process

9. Documents Provided to User

10. Hazard Warning Labels

11. Safety Interlock Systems

12. Emergency Shutdown

13. Electrical Design

14. Fire Protection


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Line Item 3, Part A

Delayed Revisions 1, Part A (Effective July 1, 2012)NOTICE: This Delayed Revisions Section contains material that has been balloted and approved by the SEMI Environmental Health and Safety Committee, but is not immediately effective. The provisions of this material are not an authoritative part of the document until their effective date. The main body of SEMI S2-0310 remains the authoritative version. Some or all of the provisions of revisions not yet in effect may be applied prior to the effective date, providing they do not conflict with portions of the authoritative version other than those that are to be revised or replaced as part of the deferred revision, and are labeled accordingly.NOTICE: Unless otherwise indicated material to be added is underlined, and all material to be deleted is struck through

D1-1 Change Paragraph 2.2 to reflect change in name of Section 15. (OPTIONAL Before Effective Date)

15. Heated Chemical Baths Process Liquid Heating

16. Ergonomics and Human Factors

17. Hazardous Energy Isolation

18. Mechanical Design

19. Seismic Protection

20. Automated Material Handlers

21. Environmental Considerations

22. Exhaust Ventilation

23. Chemicals

24. Ionizing Radiation

25. Non-Ionizing Radiation and Fields

26. Lasers

27. Sound Pressure Level

28. Related Documents

Appendix 1 — Enclosure Openings

Appendix 2 — Design Guidelines for Equipment Using Liquid Chemicals

Appendix 3 — Ionizing Radiation Test Validation

Appendix 4 — Non-Ionizing Radiation (Other than Laser) and Fields Test Validation

Appendix 5 — Fire Protection: Flowchart for Selecting Materials of Construction

Appendix 6 — Laser Data Sheet – SEMI S2

2.3 Precedence of Sectional Requirements — In the case of conflict between provisions in different sections of this guideline, the section or subsection specifically addressing the technical issue takes precedence over the more general section or subsection.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lNOTICE: This safety guideline does not purport to address all of the safety issues associated with its use. It is the responsibility of the users of this safety guideline to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use.

3 Limitations{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

4 Referenced Standards and Documents\{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

5 Terminology{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

6 Safety Philosophy{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

7 General Provisions{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

8 Evaluation Process{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

9 Documents Provided to User{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

10 Hazard Warning Labels{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

11 Safety Interlock Systems{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

12 Emergency Shutdown{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

13 Electrical Design{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

14 Fire Protection{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}


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Line Item 3, Part B

Delayed Revisions 1, Part B (Effective July 1, 2012)NOTICE: This Delayed Revisions Section contains material that has been balloted and approved by the SEMI Environmental Health and Safety Committee, but is not immediately effective. The provisions of this material are not an authoritative part of the document until their effective date. The main body of SEMI S2-0310 remains the authoritative version. Some or all of the provisions of revisions not yet in effect may be applied prior to the effective date, providing they do not conflict with portions of the authoritative version other than those that are to be revised or replaced as part of the deferred revision, and are labeled accordingly.NOTICE: Unless otherwise indicated material to be added is underlined, and all material to be deleted is struck through

D1-2 Change the name of Section 15

15 Heated Chemical Baths Process Liquid Heating

Line Item 3, Part C

Delayed Revisions 1, Part C (Effective July 1, 2012)NOTICE: This Delayed Revisions Section contains material that has been balloted and approved by the SEMI Environmental Health and Safety Committee, but is not immediately effective. The provisions of this material are not an authoritative part of the document until their effective date. The main body of SEMI S2-0310 remains the authoritative version. Some or all of the provisions of revisions not yet in effect may be applied prior to the effective date, providing they do not conflict with portions of the authoritative version other than those that are to be revised or replaced as part of the deferred revision, and are labeled accordingly.NOTICE: Unless otherwise indicated material to be added is underlined, and all material to be deleted is struck through

D1-3 Remove second sentence, including list of features, from 15.1, as it does not agree with current SEMI S315.1 Refer to SEMI S3 for the minimum safety design considerations for heated chemical baths process liquid heating. Each heated chemical bath should have the following:

grounded or GFCI-protected heater;power interrupt;manual reset;automatic temperature controller;liquid level sensor;fail-safe over-temperature protection;proper construction materials;exhaust failure interlock; andovercurrent protection.

1: See § 14 for fire protection risk assessment considerations for baths using combustible or flammable chemicals.


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn l16 Ergonomics and Human Factors{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

17 Hazardous Energy Isolation{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

18 Mechanical Design{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

19 Seismic Protection{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

20 Automated Material Handlers{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

21 Environmental Considerations{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

22 Exhaust Ventilation{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

23 Chemicals{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

24 Ionizing Radiation{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

25 Non-Ionizing Radiation and Fields{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

26 Lasers{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

27 Sound Pressure Level{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

28 Related Documents{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lAPPENDIX 1ENCLOSURE OPENINGS{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

APPENDIX 2DESIGN GUIDELINES FOR EQUIPMENT USING LIQUID CHEMICALS — Design and Test Method Supplement Intended for Internal and Third Party Evaluation Use{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

APPENDIX 3IONIZING RADIATION TEST VALIDATION — Design and Test Method Supplement Intended for Internal and Third Party Evaluation Use{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

APPENDIX 4NON-IONIZING RADIATION (OTHER THAN LASER) AND FIELDS TEST VALIDATION — Design and Test Method Supplement Intended for Internal and Third Party Evaluation Use, But Not for Field Survey of Installed Equipment{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

APPENDIX 5 FIRE PROTECTION: FLOWCHART FOR SELECTING MATERIALS OF CONSTRUCTION{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

APPENDIX 6LASER DATA SHEET — SEMI S2{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}


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Informational (Blue) Ballot1000AInformational (Blue) Ballotjn lRELATED INFORMATION INDEXCONTENTSRelated Information 1 — Equipment/Product Safety ProgramRelated Information 2 — Additional Standards That May Be HelpfulRelated Information 3 — EMO Reach ConsiderationsRelated Information 4 — Seismic ProtectionRelated Information 5 — Continuous Hazardous Gas DetectionRelated Information 6 — Documentation of Ionizing Radiation (§ 24 and Appendix 3) Including Rationale for ChangesRelated Information 7 — Documentation of Non-ionizing Radiation (§ 25 and Appendix 4) Including Rationale for ChangesRelated Information 8 — Laser Equipment Safety FeaturesRelated Information 9 — Laser Certification Requirements by Region of UseRelated Information 10 — Other Requirements by Region of UseRelated Information 11 — Light Tower Color and Audible Alert CodesRelated Information 12 — Surface Temperature DocumentationRelated Information 13 — Recommendations for Designing and Selecting Fail-to-Safe Equipment Control Systems (FECS) With Solid State Interlocks and EMORelated Information 14 — Additional Considerations for Fire Suppression SystemsRelated Information 15 — Remote OperationRelated Information 16 — Design Principles and Test Methods for Evaluating Equipment Exhaust Ventilation — Design and Test Method Supplement Intended for Internal and Third Party Evaluation Use

{No modification is proposed to the Related Information of SEMI S2. Therefore, its content has been omitted from this ballot.}

DELAYED REVISIONS 1(Effective July 2012)INTERLOCK CIRCUIT DESIGN AND SHUNT TRIP DEVICES{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

DELAYED REVISIONS 2(Effective July 2012)EMO BUTTON ACCESS{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

DELAYED REVISIONS 3(Effective July 2012)ADJUSTABLE SETPOINTS ON INTERLOCKS{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

DELAYED REVISIONS 4 (Effective July 2012)AC ENCLOSURE OPENINGS{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}

DELAYED REVISIONS 5 (Effective July 2012)ATL DEFINITION CLARIFICATION{No modification is proposed to this Section of SEMI S2. Therefore, its content has been omitted from this ballot.}


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