tip 0416-21 guideline specification for procurement of an

TIP 0416-21 ISSUED – 2009

©2009 TAPPI

The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume no liability or responsibility in connection with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published.

TIP Category: Data and Calculations

TAPPI

Guideline specification for procurement of an economizer for a recovery boiler Scope The economizer installed on a Kraft recovery boiler is the component responsible for the greatest number of tube leaks that result in lost production for the pulp and paper industry. This technical information paper provides the engineer with a guideline specification and supporting information for economizer procurement. The TIP is based on reports from a comprehensive study initiated by the AF&PA Recovery Boiler Committee (1). The study was presented at a TAPPI Conference in 2006 (2). The guideline specification addresses design, materials of construction, manufacturing and shipping recommendations for vertical tube economizers. It is formatted as a procurement specification that can be used as a basis for discussion with suppliers and obtaining quotations. The guidelines are not intended to be applied for a horizontal tube economizer, although there is some information that has merit when applied to a horizontal tube design. Definitions

A definition of the terminology as used in the TIP is necessary for understanding the general description of the economizer on a modern day recovery boiler as well as the guideline specification. Bank: a specified number of vertical tubes connected between headers and having inside the tubes an upward flow of water and over which there is a downward flow of flue gas. The following definitions for hot bank and cold bank apply where there are two or more banks. Hot bank: the bank where the flue gas exiting the generating (boiler) bank enters. . Cold bank: the final group of water cooled vertical tubes from which the flue gas temperature is at its lowest leaving the boiler envelope. Incoming feedwater enters at the bottom header and exits at the top header of the bank. Crossflow: the tubes are oriented perpendicular (at a right angle) to the gas flow. Longflow: the tubes are oriented parallel to the gas flow. Countercurrent flow: gas and water flow in opposite directions, such as, upward flow of water and downward flow of gas in a bank. Spray attemperator: a device in which water is directly contacted and mixed with superheated steam to control the steam temperature. Finned tube: as used throughout this TIP, is a design to extend the tube heat transfer surface by welding steel strip on opposite sides of the tube for its full length. Mini-header (bottle header) economizer design: a design in which straight, vertical tubes are arranged with fins in one plane and attached at the bottom to an inlet header and at the top to an outlet header to form a sheet, or platen.

TIP 0416-21 Guideline specification for procurement of an economizer for a recovery boiler/ 2

Header OD >/=63.5 mm (2.5 in.), </= 101.6 mm (4 in.); see Fig. 1. Large header economizer design: an economizer made up of shop assembled modules with finned or bare tubes that are bent to enter a large pipe header radially in rows along the header length. Header OD >/= DIN 150 (6 in.), </= DIN 450 (18 in.). Module size proscribed by shipping clearances.

Fig. 1. Mini-header sheets pre-assembled for shipment in groups of five with upper headers vertical. Safety precautions There are no safety precautions required as this TIP is a recommendation for specification of equipment Description of economizer The typical economizer is made up of one or more banks of vertical, longitudinal finned tubes with each bank having an upward flow of water inside the tubes and a downward flow of flue gas outside of the tubes. The large majority of economizers are arranged in two banks. Fig. 2 illustrates a typical, large header economizer profile of modules arranged in two banks; it is used herein as a model for tracing the flow path of flue gas and water. The flue gas exiting the generating bank enters the ‘hot’ bank of the economizer at the top in crossflow (normal to the tube), then turns in the bank to flow downward (longflow) to again turn and exit in crossflow. The gas then flows upward in a cavity formed by the rear baffle wall of the ‘hot’ bank and the front baffle wall of the ‘cold’ bank to enter at the upper end of the ‘cold’ bank, which has the same flow arrangement as the ‘hot’ bank. Each bank is enclosed by four walls, with an opening in the upper part of the front wall as an inlet to the bank and an opening at the lower end of the rear wall as an outlet. There is a sealed casing ‘roof’ at the top, and an ash hopper under the bank. The flue gas leaves the recovery boiler at the outlet from the ‘cold’ bank and passes through flue gas ducting to an electrostatic precipitator for dust collection.

3 / Guideline specification for procurement of an economizer for a recovery boiler TIP 0416-21

The feedwater flows countercurrent to the gas flow. Water enters the lower headers of the ‘cold’ bank and discharges to the steam drum from the upper headers of the ‘hot’ bank. The typical recovery boiler includes a separate heat exchanger in which feedwater is used to cool and condense a portion of the steam generated to be used as attemperator spray water to control final steam temperature. This heat exchanger (also called sweetwater condenser) is generally cooled to condense steam using the feedwater flowing from the lower temperature economizer bank to the higher, that is, from the ‘cold’ bank outlet to the ‘hot’ bank inlet.

Fig. 2. Economizer arrangement with two banks. The hot bank is on the left; cold bank on right The four vertical walls forming the bank enclosure are of both casing and watercooled construction. The sidewalls are casing and this casing is a continuation of the total economizer enclosure. The front and rear walls of the flow cavity, described in the first paragraph of this section, are generally watercooled by a portion of the incoming feedwater. The front wall of the ‘hot’ bank is watercooled, whereas the rear wall of the ‘cold’ bank enclosure is casing which supports externally enclosure insulation and lagging. The dimensions of a bank enclosure are circumscribed by 1) a width that is normally the boiler width, 2) a depth that can be cleaned by sootblowers located in a central cavity and that provides a gas velocity at or near the manufacturers design limit, and 3) a length that provides the heat transfer surface required to cool the gases to the desired final temperature. The length of a bank, inlet to outlet, is generally constrained by the maximum length of tubes available from the steel mill. This length is around 18 to 20 meters (60 to 65 feet). The usual design solution is two banks using the tubes up to the maximum length. Longer requires that two tubes be butt welded together and this large number of butt welds is not acceptable to some operating companies. A two bank economizer generally provides a compact arrangement of building and equipment that is economical and permits installation of ash and liquor systems consistent with good engineering practice. There are some installations with three banks and very few with a single bank exceeding 20 meters.


The guidelines provide for two configurations of the economizer bank for which the only significant difference is the size and arrangement of headers. Other characteristics are mostly the same. For both, the heating surface of the tubes in contact with the flue gas is extended by welding two longitudinal fins on opposite sides of a tube. Any reference herein to ‘fins’ should be understood to refer to ‘longitudinal fins’. The first configuration is the large header design where tubes are attached to large pipe headers to form a module. Fig. 3 pictures a large module prepared for shipment The header length is limited by shipping clearances of the assembled module. Several modules are arranged side-by-side with headers oriented from sidewall-to-sidewall (at a right angle to the gas flow). The tubes are bent to enter the header radially; the number is limited by header diameter. An economizer ‘bank’ might consist of two modules deep, thus, a two bank economizer would have four modules deep; this is the arrangement shown in Figure 2. The large header economizer was common into the early 1980’s.

Fig. 3: Large header module The second configuration is the mini-header design, in which straight tubes are arrayed vertically in sheets, or platens, with the fins extending to the front and to the rear. Fig. 4 illustrates a typical mini-header economizer profile of sheets arranged in two banks. The flow path of gas and feedwater is the same as described for the large header configuration. The diagonal lines indicate the ends of baffles and the allocation of surface for heat transfer calculations-inlet crossflow surface, longflow surface from inlet to outlet and crossflow at the outlet. The tubes in each sheet are arranged in one plane and attached at the bottom to an inlet header, and at the top to an outlet header as shown in Fig. 1. These individual, small diameter headers are oriented parallel to the flow of gas; the length of header is set by the number and spacing of tubes in a sheet. The sheets are suspended side-by-side across the width of the boiler. The lower headers are connected to a large feedwater pipe through an arrangement of interconnecting pipes/ piping manifold, which arrangement varies considerably among the suppliers.


Fig. 4: Economizer arrangement with mini-header banks The recommended economizer selection for future installations is the mini-header design, irrespective of a new boiler or a replacement economizer on an existing boiler. The large header design may be preferred by some for duplication of an existing economizer where the optimum approach is duplication. The mini-header design of economizer should only be considered for installation with vertical, straight tubes attached to horizontal oriented headers. Arrangements where the tubes are bent at the lower end of the economizer and the header attached to the tubes in any position other than horizontal should not be considered. A full explanation of the basis for this and other recommendations can be found in the report prepared for the AF&PA Recovery Boiler Committee (1). Tube to header weld joint Operating experience with economizers on recovery boilers has shown the welded connection of the tube to the header can be subjected to high stress warranting special attention in design and construction. There are two basic designs for welding the tubes to the header. The first is to machine on the header surface a seat, or socket, for the end of the tube that is then welded to the header. The other is to drill through the thickness of the header wall a hole that is slightly larger than the tube OD, insert the tube and weld the tube to the outside surface of the header. These are equally suitable for small and large headers. Table 1 describes these two designs.


Table 1: Attachment of tubes to header

Header machined with tube seat

Header machined with through hole

Connection Groove machined for ‘J-weld’, or equivalent, in accordance with ASME Section I, Fig. PW-16.1,

sketch (z).

Recommend restricted to lower header unless

supplier demonstrates a procedure to control that

tubes do not protrude past the inside surface of the

upper header. Weld NDT 100% PT or MT of welds 100% PT or MT of welds

Post-weld Heat Treatment

100% stress relief 100% stress relief

The tube-to-header welds are recommended for 100% post-weld heat treatment in the fabrication shop. Stress relief of the tube to header weld joints will provide the best fatigue resistance at a proven point of stress concentration. The design where tube ends are inserted into holes drilled through the header wall provides for accommodating small differences in tube length without building into the header connection points of high stress. The tube expansion is unrestrained when welded. Tubes seated at both ends in a socket on the header face will be slightly variable in length such that some will be tightly seated in the bottom of the seat (metal to metal contact). There is always a small difference in the tube length. During welding, the tube end has no possibility of expanding and the final connection has high stresses. Suppliers have available design and assembly solutions to prevent this. One method is to use a spacer that will dissolve during operation. Another is to taper the end of the stud to a point that fits into the socket. A full penetration weld will fuse the electrode metal and the tube wall. A supplier proposing to use the ‘through hole’ tube attachment to the upper header should demonstrate the quality assurance method that will prevent the tube protruding beyond the header wall to form a pocket. There are instances where an arrangement that does not permit full draining of the economizer may over time be subject to failure in the section that pockets water. The ‘J-weld’ groove machined into the tube wall, often referred to as a socket weld groove, is the preferred weld for attaching the tubes to the header. Fig. 5 shows the code requirements for this weld joint. Experience has demonstrated the weld can be durable and strong. Special attention is recommended for both supplier and purchaser to review the weld on the ‘saddle side’ of the tube to assure the required weld throat thickness for the J-weld is maintained. Should a proposed arrangement of tube and header diameter get to close in diameter, the saddle side becomes steep and it is impossible to maintain weld thickness.

Fig. 5: J-Weld, ASME Code, Section 1, Figure PW-16.1, sketch (z)


Guideline specification The guideline specification is recommended to be used for purchase of a replacement economizer, or for an economizer that is part of a total boiler package. An important section of a specification establishes the parameters of performance for which the economizer is to be designed and the performance information the supplier should include in a proposal. Table 2 establishes a list of these. The ‘customary’ North American units of measurement are indicated as well as the SI metric units to be applied. Extreme caution needs to be applied in dealing with SI metric pressure units expressed in Megapascals (MPa). Pascals are always absolute pressure and a boiler design pressure is so classified. This is a striking contrast to North America where a boiler pressure rating is always expressed in pounds per square inch gage (psig) and recorded as such. Pressure in bars is also used internationally for pressure (1 bar = 100,000 Pascals or 0.1 MPa), but is largely replaced by Pascals. Table 2: Parameters for economizer performance.

PERFORMANCE PARAMETERS CUST. UNITS

SI UNITS

INSTRUCTIONS

FLOW Steam lb/h t/h Feedwater lb/h t/h Continuous Blowdown from Drum lb/h t/h Flue Gas Exit Economizer lb/h t/h Attemperator Spray Water lb/h t//h Flue Gas Velocity at Economizer Inlet-Maximum

ft/s m/s

PRESSURE-MAWP CODE DESIGN Steam Drum psig MPa Economizer psig MPa PRESSURE (OPERATING) Adjust component reference for selected arrangement Steam Drum psig MPa Superheater Outlet psig MPa Feedwater Economizer Inlet psig MPa Feedwater at Condenser Inlet psig MPa Feedwater at Economizer Outlet psig MPa Feedwater at Attemperator Nozzle psig MPa Pressure Drop Across Economizer psi MPa Includes ΔP of condenser Draft Loss (Flue Gas ΔP Economizer) in. H2O kPa TEMPERATURE Steam at Superheater Outlet °F °C Feedwater at Economizer Inlet °F °C Feedwater at Economizer Outlet °F °C ΔT with drum water always =/> 28C° (50F°) Attemperator Water °F °C Flue Gas Entering Econo Hot Bank °F °C Temperature leaving generating bank (boiler bank) Flue Gas Leaving Econo Hot Bank °F °C Flue Gas Entering Econo Cold Bank °F °C Flue Gas Leaving Economizer °F °C ATTEMPERATOR Yes or No? Source of Spray Water? Feedwater from Deaerator or condensing steam from

boiler drum MISCELLANEOUS Heat input to feedwater from spray water condenser

Btu/h kJ/h

Velocity limit for water supply to inlet header

ft/s m/s

Maximum vertical expansion of Economizer when hot

ft-in. mm Significant when designing piping interface between boiler and fixed piping systems in building

Method to distribute feedwater uniformly through economizer tubes?

Supplier to describe


Heat transfer to the economizer feedwater must account for the heat added by a closed loop condenser attemperator system. The heat transferred to the feedwater is equal to the heat removed from the saturated steam taken off the boiler steam drum to condense the amount of steam equal to the required amount of spray water. If analysis of variable operating conditions determines the possibility for feedwater to carry steam into the drum to contain steam, install a separating device, such as cyclone separators, in the drum at feedwater inlet(s). If uncertain, it is recommended that the feedwater cyclone(s), or hydroclones, be installed Specification for detailed design of economizer Detail guidelines for specific design requirements are provided in columns headed Instruction/ Specification (Table 3). Further explanation is provided as Comments. These guidelines are based on industry experience from an AF&PA study (1). NDT and stress relief The recommended factory Non-destructive Testing (NDT) and stress relief to be performed in the execution of a supply contract for an economizer is set-forth in Table 4. It is recommended that the purchaser and the supplier agree on the NDT program and include the detail in the contract document. The program of Non-destructive Testing (NDT ) and stress relief outlined in Table 4 is recommended for maximum product integrity and quality assurance during manufacturing. If undefined, the supplier could build the economizer in accordance with the ASME Code, Section I, which requires very little NDT. NDT and stress relief are required to assure the maximum potential for economizer trouble free operation. The NDT program is not the place for the purchaser to economize. Considerations for success The success of this guideline specification to improve the integrity of an economizer purchase requires that the Purchaser be diligent throughout the program from first consideration to buy a new economizer, regardless of it being a replacement or a part of a new boiler. Some suggestions for procurement are:

• Question the suppliers about the details of their design and manufacturing that avoid problems that are known.

• Study and define the dynamic conditions and upsets that are expected to occur during the operation of your economizer. How does the supplier’s offer address positively each of these?

• Review and understand the details of the economizer you are buying and consider these in the decision making process.

• Consider that you are not buying a commodity! Treating the purchase as a commodity motivates the supplier to be innovative and implement design changes to reduce cost, and sometimes results in “cheapening” the product. The Purchaser benefits from a lower price, but may be a net loser if the changes bring problems.

• Establish requirements for drawing review and approval. Confirm that the drawings show the details that were sold by the Supplier. Establish with the supplier a program for inspection of the manufacturing by setting up “hold points” in the manufacturing schedule. At these hold points, the Supplier must request the Purchaser come to the facility to inspect and approve proceeding. The inspector should be a person with knowledge of the specification, contract, drawings, and ASME Section 1 Code. Verify that the economizer is built in accordance with the documents.

• Precautions need to be taken with respect to shipping economizer modules to the mill site. It is particularly important to avoid cyclic motions (such as swaying of railroad flat cars) that can cause fatigue cracks to develop. Side-to-side ties are particularly vulnerable. Humping of rail cars that comes with stopping and starting needs consideration in securing the module on the flat bed.


Table 3: Categorized listing of the information the purchaser should request from a supplier with a quotation.

DESCRIPTION CUST. UNITS

SI UNITS

INSTRUCTION/ SPECIFICATION

COMMENT

TYPE-CHECK ONE Mini- or Bottle Header Design Recommended design Large Header Design ARRANGEMENT Banks of Economizer Surface, front to rear

Banks of heat transfer surface will be top-supported and expand freely of a casing enclosure. Ash hopper weight to be supported independent of the tube bank.

Hopper support by enclosure

Depth of Each Bank ft – in. mm Depth of Enclosure ft – in. mm Tube Bank, between tube cntrlines ft – in. mm

Economizer Enclosure Width ft – in. mm

Type of Gas Baffles

Hot Bank Inlet At generating bank outlet

Hot Bank Outlet With 2 banks, forms front wall of gas flow cavity between banks

Cold Bank Inlet Also is rear wall of gas flow cavity

Cold Bank Outlet Wall is casing enclosure of boiler

Tube Spacing, side to side (for width)

in. mm Alternate bottom headers of platens to be offset in elevation at least 300 mm (12 in.) for ash to fall freely into hopper

Tube Spacing, depth of bank in. mm

Sootblower Cavity Width in. mm

Clearance for Access (fins tip to tip) in. mm Access required to inspect, and repair if necessary, tubes adjacent to sootblowers and tube ties

Sootblower locations Description

Tubes

OD in. mm Outside diameter in range of 38 to 50.8 mm (1.5 to 2 in.)

Thickness in. mm Minimum =/> 4.2 mm (0.165 in.), or 20% above AS ME Code


Table 3 (continued): Categorized listing of the information the purchaser should request from a supplier with a quotation.


SI UNITS


COMMENT

Material Preferred is SA-210 Gr. A1

Bare or Finned?

Length ft – in. mm No butt welds unless material availability requires

Tube lengths are available to 18.3 – 19.8 m (60 – 65 ft)

Butt welds, yes or no?

If Yes, describe reason and NDT

NDT Tubes required to be 100% UT of surface

Purchaser should understand steel mill’s criteria for acceptance when a flaw is detected

Fins

Orientation 2 longitudinal on opposite sides of tube

Height in. mm 38 to 63.5 mm (1.5 to 2.5 in.)

The Specification envisions steel strip for fins. Alternative is to weld flat studs for extended surface

Thickness in. mm

Material

Angle of Fin Taper at Ends degrees

degrees Fins to be tapered <30° from the end with a small “land” at the extremity for weld “wrap around”

No taper is required for flat studs

Method of Attachment of Fins

Provide detail drawing of welding at the fin termination

Recommend continuous machine weld both sides with wrap-around weld at fin ends.

Manual weld shall start and stop on the machine weld.

The combined cross-section area of the welds to be greater than area of fin contacting tube wall

Fin termination stress analysis Supplier to provide finite element analysis stress report

Number of Tubes, each bank

Number of Sheets, each bank

Heating Surface for each bank ft2 mm2 Adjust reporting for actual arrangement.

Total – Hot Bank ft2 mm2

Total – Cold Bank ft2 mm2

Surface Effective for Heat Transfer ft2 mm2

Total – Hot Bank ft2 mm2

Total – Cold Bank ft2 mm2

Total Surface (∑ of all Surfaces) ft2 mm2 °




SI UNITS


COMMENT

Header for Sheets

Header Orientation Horizontal headers recommended without exception

Sloped lower headers associated with high stresses and failures

Upper Header

Material

Diameter in. mm

Thickness in. mm

Length in. mm

Lower Header

Material

Diameter in. m m

Thickness in. mm

Length in. mm

Number of Tubes per Header

Feedwater Connections/Header

Location of Connections Review feed tubes for individual mini-headers to assure flexibility and minimize

stress concentrations at feed

tube to mini-header weld

Two options are inlet feed tube connected at bottom of header approx mid-point or entering the end of a header

Size of connections in. mm

Velocity Limit for Design ft/s m/s Supplier design to distribute water evenly to the tubes and avoid incoming water jetting into a tube

With Feedwater Control Valve fully open

Handholes per Header Inspection pipe nipple with cap preferable to seat machined in header wall with seal weld

For large headers. Seal weld of handholes in header wall is a potential source of leaks

Location of Handholes

RT Plugs per Header If required, locate in header wall where accessible. Do not place in header end plate

For large headers. Plugs are a potential source of leak

Plug Location

Detail of Tube attachment to Header ASME Section 1, Fig. PW-16.1, Sketch (z), or equivalent

Recommended attachment to header is a machined seat for J-weld socket, or equivalent . Forged headers with extruded nozzles to which tubes are butt-welded are not recommended.




SI UNITS


COMMENT

Include Drawing- 2 views at 90° Demonstrate tube header joint to have sufficient weld throat at sides of the tube (saddle side)

Where tubes extend beyond the header inside wall, Supplier to describe QA program of arrangement so a water pocket is not formed in the header.

Alternative Attachment For one only of 2 headers, tube extends through the header wall & externally welded to header

Where tubes extend beyond the header inside wall, Supplier to describe QA program of arrangement so a water pocket is not formed in the header.

Enclosure and Baffles-Describe

Baffle closest to generating bank

Baffle or enclosure wall bank outlet Alternative arrgts-bolted plates, finned tubes sealed by welding together fin tips, & membrane tube panel

Enclosure Sidewalls

Front to Rear Tube Alignment

Ties fastening together fins on adjacent tubes in a sheet

A durable tie, such as, small piece of plate equally bridging spacing between fins and welded full periphery to each fin. Stitch welds between fins not recommended

Maintain alignment & control vibration. Shop installed. Most inaccessible for repair

Location

Dimension between levels ft – in. mm

Number of Levels Number of levels increases as tube diameter decreases

Describe tie bridging sootblower cavity

Describe connection to baffle

Side to Side Tube Alignment

Description of maintaining spacing of sheets

Describe spacers/ties. Preferred is sootblower elevations for cleaning.

Location Indicate location/elevations

Dimension between levels ft – in. mm

Number of levels

Description at lower header elevation

Vibration Restraint Supplier to describe vibration experience and how the design restrains vibration




SI UNITS


COMMENT

SHIPPING AND HANDLING

Number of Sheets/Module

Shipping Weight of Module Supplier to confer with Purchaser’s Erector for Maximum weight

Number of Modules

Shipping Dimensions of Module

Preservation for Shipping

Paint

Method for Closure of Openings

Special Handling, if required

Is shipping frame required? If YES, who supplies?

Design Drawings

Finished Frame

Internal bracing and cribbing of Sheet or Module

Special attention required for railroad shipment

Cribbing and bracing sufficient to prevent the spacer bars and tube welds from fatigue cracking on rail cars

Freeze Protection A propylene glycol solution should be used for shop hydrostatic testing in winter to prevent freezing during transport

Transport

Type of Carrier Truck, railroad car, ship, etc

Handling at Erection Site

Requirements for Lifting Supplier to describe requirements at site for shifting module from horizontal to a vertical orientation, and lifting into position

Multiple pick-up points on long sheets as required. Smaller tubes are more flexible than larger tubes and require more diligence in lifting

Availability of specification An Excel spreadsheet combining Tables 2 and 3 in a format to be used as a specification is available upon request to [email protected]. The spreadsheet has an additional column named “Supplier Design Data.” The expanded sheet can be used in an appropriate manner by an engineer to prepare the technical description for a specification into which the engineer can enter the project requirements as “Supplier Design Data,” and require the supplier to complete the “Supplier Design Data.” Requirements for the economizer are spelled out in the spread sheet section “Instruction/Specification”. The spread sheet further includes space for explanatory “Comments” by Purchaser or Supplier. The list of “performance parameters” is information that when entered will provide a complete description of the economizer.


Table 4: Recommended nondestructive testing

Mini- or Bottle Header Design Large Header Design Purchase of seamless tubes Full body (100%) UT Full body (100%) UT

Butt weld in long tubes 100% RT1 100% RT 1 Butt weld to forged header

nozzles 100% RT 2 Not Applicable

Butt weld in connecting piping internal to Section I

battery limits

100% RT 100% RT1

Fin-to-tube weld 3 Visual inspection Visual inspection Tube-to-header weld 100% PT or MT 100% PT or MT Fin-to-fin ties in the

backspace/stitch weld Visual and 10% MT 4 Visual and 10% MT 4

Fin-to-fin tie in the backspace/plate welded to

both fins

Visual and 10% MT 4 Visual and 10% MT 4

Weld of hanger lugs to headers

10% MT 10% MT

Post-weld stress relief of tube to header welds

100% 100%

Hydrostatic testing Not required 5 100% of modules 1 Supplier to define acceptance criteria and procedures for repair of unacceptable welds. The acceptance criteria and repair procedure should be stated in the contract. Information on RT of butt-welds in provided in TAPPI TIP 0402-33. TIP 0402-33 (3). Real Time Radiography of tubes joined using automatic orbital welding is an acceptable method. Tubes that do not meet acceptance criteria are to be repaired immediately. Shear-wave ultrasonic testing is an acceptable alternative. More information on UT of butt welds is provided in TAPPI TIP 0402-31 (4). 2 Headers with forged nozzles are not recommended for use. 3 The Supplier shall reach agreement with the Purchaser on the weld appearance that is not acceptable and requires re-work. 4 In those instances where ‘10%’ is listed, the Supplier shall describe the remedial action in the event there are defects for increased NDT. 5 This test is considered to have no value added when the other tests are carried out. Keywords Recovery boilers, economizers, specifications Literature cited 1. Grace, T.M. and Clement, J.L., “Investigation of the Causes of Recovery boiler Economizer Failures and Identification of Means for Preventing Their Occurrence”, AF&PA Recovery Boiler Committee, March 14, 2006 2. Grace, T.M. and Clement, J.L., “Investigation of the Causes of Recovery boiler Economizer Failures”, Proceedings of the TAPPI Engineering, Pulping and Environmental Conference, Atlanta, GA (2006) 3. TAPPI TIP 0402-33, Guidelines for Obtaining High Quality Radiographic Testing (RT) of Butt Welds in Boiler Tubes 4. TAPPI TIP 0402-31, Guidelines for Evaluating the Quality of Boiler Tube Butt Welds with Ultrasonic Testing Additional information Effective date of issue: April 15, 2009 Working Group:

John L. Clement, Chairman, Clement Consulting Inc. John D. Andrews, MeadWestvaco Dean I. Clay, International Paper Len T. Erickson, Boise Paper Solutions Thomas M. Grace, T. M. Grace Company g

tip 0416-21 guideline specification for procurement of an

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