api 682 overview

Overview of API 682and ISO 21049Michael HuebnerFlowserve Seal Division

Review of API 682 First EditionCreated by industry leaders in rotating equipmentDesigned to capture field experienceDefaults to proven solutionsApplies to the most common applications

Mission Statementfrom API 682 First EditionThis standard is designed to default to the equipment types most commonly supplied that have a high probability of meeting the objective of a least three years of uninterrupted service while complying with emissions regulations.

Second EditionSuccess of First EditionApplications outside of refineriesApplication to non-API 610Advancement in sealing technologyCreation of an International standard

Third EditionReview by ISO member countriesFew technical changesSome editorial changes including minor reorganizationOne new piping planReleased as ISO 21049 and API 682 3rd Edition

Scope of StandardComparison of First and Second Editions

Seal TypesOver the years, seal companies have released numerous designs and variationsNo standardization in seal designs, materials, or dimensionsChallenge for API 682 Task Force was to create standard seal types defining seal design, materials, installation envelope, and operating windows

Type A SealRotating flexible element, multiple springs, O-ring secondariesSilicon Carbide versus premium grade blister resistant CarbonFluoroelastomer O-rings (FKM)Alloy C276 springs (316 for single spring option)Type 316 SS sleeve, gland, and other metal partsThrottle bushing in gland

Type B SealRotating bellows, O-ring secondariesSilicon Carbide versus premium grade blister resistant CarbonFluoroelastomer O-rings (FKM)Alloy C-276 bellowsType 316 SS sleeve, gland, and other metal partsThrottle bushing in gland

Type C SealStationary bellows, flexible graphite secondariesSilicon Carbide versus premium grade blister resistant CarbonAlloy 718 bellowsType 316 SS sleeve, gland, and other metal partsPremium carbon floating bushing in glandBronze anti-coke device

Rotating vs StationaryThe default Type A and Type B seals have a rotating flexible elementA stationary flexible element is an alternateThe default Type C seal has a stationary flexible element A rotating flexible element is an alternateIf surface speed at the faces exceeds 4500 ft/min (23 m/s), a stationary flexible element must be used

Seal ArrangementsThe seal arrangement defines the number or seals, their orientation, and details about the seals operationDesignationsContacting wet (CW)Containment seals (CS)Non-contacting dry-runningContacting dry-runningNon-contacting (NC)Wet running sealsDry-running dual seals

Contacting Wet Seal - CWTypical mechanical sealMechanical seal designed to run on liquid fluid filmDoes not intentionally create hydrodynamic forcesRequires vapor suppression to keep fluid in a liquid phaseDesigned to run for a minimum of 25,000 hours

Containment Seal - CSDesigned as a dry running backup sealOuter seal in a dual non-pressurized arrangementMay be either a non-contacting or contacting designOperates on buffer gas or vaporized process fluidRun for 25,000 hours at 10 PSI and at least 8 hours under process conditions

Non-Contacting Seal - NCMay be used as a primary seal or as a dual pressurized sealSeal is designed to create hydrodynamic forces to separate the faces under all operating conditionsDesigned to run for a minimum of 25,000 hours

Arrangement 11CW-FX or 1CW-FL configurationSingle mechanical sealMay have a fixed or floating throttle bushingMay have single point or distributed flush

Arrangement 2Liquid Buffer Fluid2CW-CW configurationDual non-pressurized seal with a liquid buffer fluidSame as the First Edition Arrangement 2 seal

Arrangement 2Vapor or No Buffer Fluid2CW-CS configurationContacting wet seal with a dry running containment sealContainment seal may be either contacting or non-contacting

Arrangement 2Vapor or No Buffer Fluid2NC-CS configurationInner seal is designed to be non-contacting and operate with liquid, vapor, or mixed phase processOuter seal a containment seal

Arrangement 3Liquid Barrier Fluid3CW-FB configurationContacting wet seals oriented in a series (or face-to-back) orientationDefault Arrangement 3 liquid sealSame as the First Edition Arrangement 3 seal

Arrangement 3Liquid Barrier FluidAlternate designs for Arrangement 3 liquid seals3CW-BB or 3CW-FF configurationsMay be required for specific application or pump designs

Arrangement 3Gas Barrier Fluid3NC-BB configurationDefault Arrangement 3 gas sealNon-contacting gas seals in a back-to-back orientation

Arrangement 3Gas Barrier FluidAlternate designs for Arrangement 3 gas seals3NC-FF or 3NC-FB configurationsMay be required for specific application or pump designs

CategoriesDifferent applications may require different levels of seal sophisticationCurrent practice of specifying modified API-682 sealsSize restrictions based on pump constructionCost impact of seals

CategoriesThree categoriesCategory 1 General duty services in chemical pumpsCategory 2 Heavy duty services; similar to API-610 7th edition sealsCategory 3 Heavy duty services; similar to API 682 First Edition seals

Comparison of Categories

Review of Key ConceptsThe Standard has categorized three types of seals: Type A, B, and CThere are three basic arrangements: Arrangement 1, 2, and 3.To address differing needs for features and documentation, there are three categories of seals: Category 1, 2, and 3.

DimensionsPurchaser shall specify if the order is to be provided in SI or US Customary unitsThis includes data, drawings, hardware, fasteners, and other equipment

Design RequirementsDesign requirements are divided into three areasGeneral these requirements pertain to all API-682 sealsCategory Specific this section defines requirements that are specific to each seal categoryArrangement and Configuration Specific these sections define requirements specific for each seal configuration

Design Requirements - GeneralAPI 682 First Edition states that the standard does not cover the design of the component parts of mechanical seals This statement is followed by 16 pages of specifications that directly affect the design of seal componentsThe Second Edition follows this same path and contains even more specifications on seal designThese requirements attempt to capture design features that have proven to be successful in the field

Design Requirements - GeneralAll seals will be cartridge sealsType A and B seals can be designed with stationary flexible elementsType C seals can be designed with a rotating flexible elementAll seals with seal face surface speeds greater than 4,500 ft/min (or 23 m/s) will have stationary flexible elements

Design Requirements - GeneralSeal must handle normal and transient axial motionsMinimum surface finish for O-ringsO-ring grooves sized for FFKMFor vacuum services, components that could be dislodged must be positively retainedMinimum clearance between rotating and stationary components 3mm (with some exceptions)Glands designed for MAWP of pumpGlands provided with holes (not slots)Shoulder at least 3mm behind face in gland

Design Requirements - GeneralSeal designed for seal chamber perpendicularity of 0.0005 in./in. of boreVapor pressure margins must be maintained at 30% pressure margin or 20C (36F) temperature marginSeal chamber pressure must be at least .35 bar (5 PSI)Floating throat bushings may be requiredGland and seal chamber connections must be permanently marked

ConnectionsNote 3A 3/8 NPT connection may be used if NPT not possible due to space constraints.Note 4A NPT required for shaft diameters 63.5 mm (2.5 inch) or smaller, NPT for larger sizesNote 5A NPT connection may be used if 3/8 NPT is not possible due to space constraints

ConfigurationSymbolConnectionLocationTypeSizeCat ISizeCat II and IIIRequired1CW-FX1CW-FLFFIFODQHCFlushFlush In (Plan 23 only)Flush Out (Plan 23 only)DrainQuenchHeatingCooling0180018090--ProcessProcessProcessAtmoAtmoUtilityUtility (Note 3) (Note 3) (Note 3 & 6)3/8 (Note 5)3/8 (Note 5) (Note 3) (Note 3)3/83/8RequiredWSWSRequiredRequiredWSWS2CW-CWFLBILBODQFlush (Inner Seal)Liquid Buffer Fluid InLiquid Buffer Fluid OutDrain (Outer Seal)Quench (Outer Seal)0180018090ProcessProcessProcessAtmoAtmo (Note 3) (Note 4) (Note 4)3/8 (Note 5)3/8 (Note 5)3/83/8RequiredRequiredRequiredWSWS


ConfigurationSymbolConnectionLocationTypeSizeCat ISizeCat II and IIIRequired2CW-CSFFIFOGBICSVCSDDQFlush (Inner Seal)Flush In (Plan 23 only)Flush Out (Plan 23 only)Gas Buffer Fluid InContainment Seal VentContainment Seal DrainDrain (Ourer Seal)Quench (Outer Seal)0180090018018090ProcessProcessProcessProcessProcessProcessAtmoAtmo (Note 3) (Note 3 & 6)3/8 (Note 5)3/8 (Note 5)3/83/8RequiredWSWSWSRequiredRequiredWSWS2NC-CSGBICSVCSDDQGas Buffer Fluid InContainment Seal VentContainment Seal DrainDrain (Outer Seal)Quench (Outer Seal)90018018090ProcessProcessProcessAtmoAtmo3/8 (Note 5)3/8 (Note 5)3/83/8WSRequiredRequiredWSWS


ConfigurationSymbolConnectionLocationTypeSizeCat ISizeCat II and IIIRequired3CW-FB3CW-FF3CW-BBFLBILBODQFlush (Seal Chamber)Liquid Barrier Fluid InLiquid Barrier Fluid OutDrain (Outer Seal)Quench (Outer Seal)0180018090ProcessBarrierBarrierAtmoAtmo (Note 4) (Note 4)3/8 (Note 5)3/8 (Note 5) (Note 4) (Note 4)3/83/8WSRequiredRequiredWSWS3NC-FF3NC-BB3NC-FBFGBIGBODQFlush (Seal Chamber)Gas Buffer Fluid InGas Buffer Fluid OutDrain (Outer Seal)Quench (Outer Seal)0018018090ProcessBarrierBarrierAtmoAtmo 3/8 (Note 5)3/8 (Note 5) 3/83/8WSRequiredRequiredWSWS

Design Requirements - GeneralThreaded connections shall be pluggedConnections and tubing shall be suitable for max hydrostatic test pressureDrill throughs minimum 5mm (3/16) diameterFixed and floating bushing clearances defined

Floating carbon throttle bushingdiametrical clearances

Sleeve DiametermmSleeve DiameterinchMax diametrical clearancemmMax diametrical clearanceinch0 to 500 to 2.000,180.00751 to 802.01 to 3.000,2250.00981 to 1203.01 to 4.740,280.011

Design Requirements - GeneralSleeves furnished by the seal OEMSleeve to shaft clearances defined by ISO 286-2 F7/h6Sleeves must have a shoulder to positively locate sealSleeve gasket O-ring shall be located at the impeller endSleeves thickness to be minimum of 2,5 mm (0.100 in)Sleeve in areas of set screws defined

Shaft DiametermmSleeve DiameterinchMinimumSleeve Radial ThicknessmmMinimumSleeve Radial ThicknessInch< 57< 2.252,50.10057 to 802.25 to 3.253,80.150> 80> 3.255,10.200

Design Requirements - GeneralSleeve OD and ID concentric within 25m (0.001 in)Sleeve piloted on both ends, relieved in the middleDrive collar set screws not allowed in piloted areaDrive collar set screws sufficiently hard to embed shaftUse of nine or more set screws only with approvalOther drive devices (e.g. shrink disk or split ring drive collars) are allowed with approvalSingle spring allowed on Type A seals if specifiedFlexible elements shall not rely on lapped joints for sealing

Design Requirements - General

Seal FacesCategory 1- Self Sintered SiC vs premium grade, blister-resistant carbon graphiteCategories 2 and 3 Reaction Bonded SiC vs premium grade, blister-resistant carbon graphiteHard Faces SiC vs SiCSeal SleevesAISI Type Type 316, EN 10088 Grade 1.4571SpringsMulti-spring seals Alloy C-276, Alloy C-4Single spring seals AISI Type 316Secondary SealingComponentsUnless otherwise specified FKM (fluoroelastomer)If required FFKM (Perfluorelastomers) or flexible graphiteMetal BellowsType B seal Alloy C-276Type C seal Alloy 718Gland PlatesAISI Type Type 316, EN 10088 Grade 1.4571MiscellaneousAISI Type Type 316

Other Design RequirementsCategory SpecificCategory 1Category 2Category 3Arrangement SpecificArrangement 1Arrangement 2Arrangement 3

Seal Chamber InterfacesAlmost all pump references have been removed from API-682 Second EditionInterface requirements have remained since they greatly affect the performance of a mechanical seal

Seal Chamber InterfacesSeal chamber face runout must be less than 0,5 m/mm (0.0005 in/in) of seal chamber bore

Seal Chamber InterfacesPilot diameter (either OD or ID) must be concentric to shaft with a TIR of not more than 0,125mm (0.005 in.)

AccessoriesAccessories are components other than the seal that are required to create an acceptable sealing environment. This includes:Auxiliary piping systemsCyclone separatorsOrificesSeal coolersReservoirsPumping ringsCondensate collection reservoirsGas supply panels

Auxiliary Piping SystemsThe standard defines many requirements of piping systems for seal flushes (Group I), quench systems (Group II), and cooling water systems (Group III)Tables define specific grades and classes for tubing, valves, fittings, fabricated joints, gaskets, and boltingDiffering requirements for each Group

Cyclone SeparatorsCyclone separators should be the flow limiting deviceSolids should have a density at least twice that of the fluidOn between bearing pumps, each seal shall have its own separatorDefault material is austenitic stainless steel

Flow Control OrificesOrifice tubing connectors and plate orifices are the default selectionOrifice nipples may be provided if specifiedMinimum diameter is 3 mm (0.125 in)Multiple orifices shall be separated by a minimum of 6 inches

Seal flush on tube side of coolerBoth process and cooling water sides must be able to be completely vented and drainedDrain valve must be provided on water side

Seal Flush Coolers

Seal Flush CoolersTwo sizes of coolers:For shaft sizes over 60mm (2.5 inch) 0.750 inch diameter tube with 0.095 inch wall thicknessFor smaller shaft sizes 0.500 inch diameter tube with 0.065 inch wall thickness

Reservoirs have specific requirements for features, connections, dimensions, volumes, and materialsFor shaft diameters over 60 mm (2.50 in), volume of liquid shall be a mimumum of 20 l (5 gallons)For smaller shaft diameters, volume of liquid shall be a minimum of 12 l (3 gallons)Buffer/Barrier Reservoirs

Buffer/Barrier Reservoirs3 gallon reservoirs are constructed of 6 inch schedule 40 pipe.5 gallon reservoirs are constructed of 8 inch schedule 40 pipeCooling coils to be 0.500 inch tube with minimum 0.065 inch wall thicknessBoth fixed and removable head designs are available

Condensate Collection ReservoirUsed to collect leakage on Plan 758 inch schedule 40 pipe, 12 l (3 gal)Carbon steel or same as pump metallurgyLevel gauge, drain and vent connectionsLevel switch and test connections optional

Barrier/Buffer Supply PanelSeal OEM and purchaser to agree on requirementsInclude at minimum an isolation valve, coalescing filter, pressure regulator, flow meter, low pressure switch, pressure gauge, and check valve.High flow switch is optional

InstrumentationStandard covers basic requirements for the following components:Temperature indicating gaugesThermowellsPressure gaugesSwitchesPressure switchesLevel switches

Flow switchesLevel indicatorsFlow indicatorsRelief valvesRegulators

Inspection, Testing, and Preparation for ShipmentGeneral inspection by vendorInspection of seal componentsQualification testingHydrostatic testing of glandsAir testingPump manufacturer seal test

Qualification TestingEasy for a standard to create a goal of 25,000 hours of service but difficult to prove itConcern from users that seals should be tested under real world conditionsTesting is designed to provide the user with a level of confidence that the seals will perform as required by the standard

Qualification TestingTesting will qualify a seal model so testing only needs to be done once for a specific sealNot intended as testing for actual job sealsTwo sizes need to be tested: a small size with a balance diameter between 50mm to 75mm (2.0 to 3.0 inches) and a large size with a balance diameter between 100mm to 127mm (4.0 to 5.0 inches)

Qualification TestingTesting requirements are different between the seal categoriesCategory 3 seals must be tested in the same configuration as is being offeredCategory 1 and 2 seals may be tested in the same configuration as is offered or it may be designed with seal faces that have been qualified in other testingAllowance for seal face materials to be qualified as a mating pair to cut down on the number of tests required

Qualification TestingEnd users identified typical refinery applications based on process fluids, temperatures and pressuresSelected five test fluids that are representative of these applications and that were acceptable for lab testingDeveloped a set of steady state and cyclic conditions that would simulate actual field conditions

Test Fluids

Test Cycle for Liquid Seals

Water Test Parameters

Test Qualification Form

Containment Seal TestingIn the Second Edition, testing requirements were defined for containment sealsTesting would demonstrate performance under steady state conditions as well as simulated failure of the inner sealRecorded data include leakage rate past containment seal

Test Cycle for Containment Seals

Dual Gas Seal TestingDual gas seal testing is designed to evaluate the seals on the process fluid with an inert barrier gasTesting involves steady state testing as well as the cyclic testing precedures defined for liquid sealsAlso involves simulated disruptions of the barrier gas supply

Test Cycle for Dual Gas Seals

Gas Seal and Containment SealTest Qualification Form

Minimum Performance RequirementsFirst Edition had no acceptance criteria for qualification testsSecond Edition has criteriaAt the end of the testing, the wear on the seal faces shall be less than 1% of the available wearSingle seals and containment seals must have less than 1000 PPM measurable emissions during propane tests or an average leakage rate less than 5.6 gr/hr during other tests

Hydrostatic Testing of GlandsFirst Edition required hydrostatic pressure testing of all pressure casing components which included the seal glandTest pressure 1.5X MAWP of the pump casing but not less than 1,4 bar (20 PSI)Second Edition exempts testing of seal glands manufactured from a single piece of wrought material

Air Testing of AssembliesEvery seal assembly shall be air tested by the seal OEMDual seals tests must have ability to test each sealing section independentlySeals tested at 1.8 bar (26 PSI) with a gas volume of a maximum of 28 l (1ft3)Maximum pressure drop of 0,14 bar (2 PSI) over a five minute periodSeals tagged after successful completion

Overview of AnnexesAnnexes comprise almost exactly half of the pages in API 682 Second EditionContain support material for the standardConsists of both normative and informative sectionsNormative annexes are enforceable parts of the standardInformative annexes are for information only

Annexes (2nd Edition)Annex A Recommended seal selection procedureAnnex B Heat generation and heat soak calculationsAnnex C Materials and material descriptionsAnnex D Standard flush plans and auxiliary hardwareAnnex E Inspector checklistAnnex F Mechanical seal data sheetsAnnex G Mechanical seal data requirement formAnnex H Seal and pump vendor interface paragraphsAnnex I Mechanical seal test qualification formAnnex J Mechanical seal code

Seal Selection ProcedureProcedure was developed to capture selection methods that have proven successful in the fieldSystematic method of selecting a seal type, arrangement, and piping plans for a number of common applicationsDoes not cover every serviceWhere alternate solutions are given, they are considered as technical equals

Fluid TypesBasic refinery fluids have been divided into three application groups:Non-hydrocarbon these fluids include water, sour water, caustic, amines, crystallizing fluids, and some acidsNon-flashing hydrocarbons this covers hydrocarbons with a vapor pressure less than 1 bar (14.5 PSIA)Flashing hydrocarbons This group covers hydrocarbons with a vapor pressure greater than 1 bar (14.5 PSI)

Selection FlowchartEach application group has its own path although all application groups share some common selection proceduresSelection charts for seal type and piping plans are unique for each fluid type

Identify ServiceIdentify application (fluid, temperature, pressure, speed, contaminants, etc.)Classify fluid as non-hydrocarbon, non-flashing hydrocarbon, or flashing hydrocarbonDetermine if application is outside the range of the selection criteriaOver 260C (500F) or 21 bar (300 PSI) for Category 1 sealsOver 400C (750F) or 41 bar (600 PSI) Category 2 and 3 sealsSurface speeds above 23 m/s (4500 ft/min)Vapor pressures over 34 bar (493 PSIA)High concentration of solidsShafts larger than 110mm (4.3 inches) or smaller than 20mm (0.75 inches)

Select Seal CategorySelection based on features for each categoryIntended pump designPressure and temperatureRequired featuresRequired documentationPurchaser will specify category to seal supplier

Select Seal TypeEach application group has its own sheetSelection based on matrixOutput is seal type and required special featuresFeatures required cover abrasives, caustics, amines, ammonia, and H2S

WaterWaterWaterPumpingTemp, F< 180180Pressure,Category 1

Select Seal ArrangementFlowchart directs user through a series of Yes/No questionsOutput is required seal arrangementQuestions include the following topicsRegulationsConsequences of leakage on environment, personal safety, regulationsExperience and operating practicesSelection may be made by the user or seal OEM

Select Seal Flush PlanEach application group has its own sheetUser begin the flow chart at the starting point for the selected seal arrangementOutput is the required piping plan(s)

Select Buffer/Barrier FluidStandard gives basic guidelines for selection of buffer and barrier fluidsTopics include:Chemical and material compatibilityGas absorption on pressurized sealsRecommended viscosity rangesEnvironmental and safety considerations

TutorialsAlong with the selection procedure, Annex A also includes extensive tutorialsBackground of selection procedureGuidelines for specific applicationsInsights into the seal arrangement selection questionsTutorials on piping plans

Piping PlansThe complete listing of piping plans is covered in Annex DContinuation of piping plans from the First EditionNew piping plans introduced:Moved over from API 610Variations of dual pressurized liquid plansPlans for containment and dual gas seals

Plan 14

Plan 53A

Plan 53B

Plan 53C

Plan 65

Plan 71

Plan 72

Plan 74

Plan 75

Plan 76

Data SheetsFirst Edition has a five-page seal data sheet along with a two-page pump data sheetThe Second Edition only requires the user to fill out a two-page data sheetCategories 1 and 2 are grouped together and have a two-page data sheetCategory 3 has a separate two-page data sheetData sheets are available in both SI and US Customary units

Data SheetsHard copies may be reproduced from the standardExcel spreadsheet copies are also available

Seal CodeInformativeDifferent from 1st EditionDifferent from API 610Four segment codeFirst segment seal category (C1, C2, C3)Second segment arrangement (A1, A2, A3)Third segment seal type (A, B, C)Fourth segment piping plan (e.g. 11)

Seal CodeC1A1B11Category 1 sealArrangement 1 (single seal)Type B seal (bellows)Plan 11C3A3A53BCategory 3 sealArrangement 3 (dual pressurized seal)Type A seal (pusher)Plan 53B (liquid barrier fluid pressurized by a bladder accumulator)

Questions?

API-682 First Edition was really a landmark document in the field of mechanical sealing. The standard was not a simple technical document but rather a complete overview of mechanical sealing in the refinery environment.

One of the most import aspects of this standard was that it was created by industry leaders in rotating equipment from the major refineries. These individuals recognized that many of the experienced engineers and maintenance personnel were retiring without documenting their knowledge. This standard was designed to capture some of this field experience.

Rather than show every possible solution to an application, the Task Force decided to default a single proven solution. This solution would be the most commonly used approach used in industry. In addition to the default solution, alternates would be presented when they were technically acceptable. An alternate is technically equivalent to the default solution.

The Task Force also realized that it would be impossible to cover every application on every piece of equipment used in a refinery. They focused the standard on addressing the most common applications, in common fluids, in common equipment. The standard does not address hazardous fluid such as HF acid or cover special equipment such as turbines or compressors. Still the standard covers the vast majority of application found in the refinery.The mission statement captures the intention of the standard. Breaking this down, we can see some of the major points:

This standard is designed to default (that is come up with a single solution) to the equipment types most commonly supplied (not every sealing solution but only the most common ones that have proven to be successful in the field)that have a high probability (not a guarantee but a high probability)of meeting the objective of three years of uninterrupted service (the seal must be designed so it is capable of at least three years of service without adjustments, alterations, or refurbishment)while complying with emissions regulations.

This was the goal of the First Edition.Since the First Edition was officially published in 1994, it has become the highest selling API standard on mechanical equipment. It has been sold in over 25 countries and is universally recognized as THE standard for mechanical seals in the refinery industry.

Due to the success of the First Edition, API recognized the need for a Second Edition. One of the driving forces was the knowledge that the standard was being used in industries outside of refineries. Companies were using API pumps in chemical and petrochemical facilities. In addition, refineries were also ANSI/ASME pumps for many general or low-duty services. In either case, it was difficult or impossible to apply the First Edition to these applications.

Sealing technology has made great advancements since the release of the First Edition. Dual dry running seals and containment seals were now used commonly in refineries and chemical plants. New piping plans were developed to support these new seal types. There was confusion on how to designate these new seals, arrangements, and piping plans.

While the First Edition had become a sort of international standard, it was written very much like an American standard. Many of the dimensions defaulted to US customary units. Most of the outside references were to US standards organizations like ASME or ANSI. This made the standard difficult to apply in many countries.

All of these factors influenced the direction of the Second Edition. The goal was to continue with the objectives of the First Edition while expanding into new industries and capture new seal technology. This was done with the clear intention of having the standard issued as an ISO international standard.As stated earlier, the 682 Task Force did not intend this standard to cover every piece of rotating equipment in a refinery. It was intended to cover perhaps 90% of the sealed rotating equipment. The First and Second Editions have the following scopes.

The First Edition used the term Seal Size throughout the standard. This lead to some confusion since different seal OEMs use different criteria for determining their commercial designation for a seal size. The Second Edition uses the shaft diameter which is unambiguous. With this cleared up, the First Edition was limited to seal sizes from 30mm to 120mm (1.50 to 4.50). The Second Edition is applicable to shaft sizes from 20mm to 110mm (0.75 to 4.30).

The First Edition had a temperature range from -40C to 260C (-40F up to 500F). The Second Edition greatly expanded this to -40C to 400C (-40F to 750F).

The First Edition was used in pressures from 0 to 34.5 bar (0 to 515 PSIA) while the Second Edition is used from 0 to 42 bar (0 to 615 PSIA).

The applicable process fluids are unchanged from the First to the Second Edition.

The First Edition was written specifically to be used in API 610 8th edition pumps. API 610 was later adopted by ISO and designated as ISO 13709. The Second Edition still applies to the API 610/ISO 13709 pumps. It has also been expanded to include ANSI B73.1 and B73.2 seal chambers and ISO 3069 Frame C seal chambers. On the ANSI/ASME pumps notice that this applies only to the seal chambers (often called big bore boxes). This standard does not apply to seals designed to fit into the small stuffing boxes designed for packing.Over the years, seal companies have released literally hundreds of seal designs and variations. Surprisingly, there has been very little effort to standardize seal designs, materials, dimensions, or even their interfaces into a pump. There are some German standards that define interface between component seals and pumps as well as some ANSI, API, and ISO efforts to define a standard seal chamber. Still, the design of seal chambers and mechanical seals has largely been in the domain of the OEMs.

One of the challenges for the API 682 Task Force was to create standard seal types that would define the basic seal design, materials of construction, minimum installation envelope, and operating windows.

A Seal Types is a basic description of the seal. Historically people used terms like spring pusher, bellows, multi-spring, single spring, rotating, and stationary to describe a seal. They would also add other design features such as high balance, multi-port, or distributed flush to further define it. Then to define the materials, they would need to specify the materials for all of the major components. This was an inefficient means of referencing a specific seal.

The concept of Seal Type captures all of these details.There are three seal types designated as Type A, B, and C.

The Type A seal has a rotating flexible element, multiple springs, and O-ring secondary seals. The figure on the left shows the default configuration where the springs are rotating with the shaft. The figure on the right shows an alternate arrangement where the springs are stationary with the seal gland. This stationary design may be required in higher speed applications.

In these and the following figures, the rotating elements are shown in blue and the stationary elements are shown in yellows and browns. This will help you quickly see which components are rotating and which are stationary.

The default face materials for the Type A seal are Silicon Carbide versus premium grade blister resistant carbon. The standard O-ring materials is a fluoroelastomer (or FKM) such as Viton. The default spring material is Alloy C-276. There is an option where a 316SS single coil spring can be used. The other metal parts such as the sleeve, gland, and spring holder are 316SS. A throttle bushing in the gland is required for all single seals.

Note that the seal type does not designate the number of seals. This will be defined under the seal arrangement. There are also additional design details which will be defined under the seal category.The type B seal is similar to the Type A seal except the basic seal is now a metal bellows seal. The metal bellows acts as both the spring element and the dynamic gasket.

The default configuration is shown on the left with the bellows mounted onto the sleeve and rotating with the shaft. The figure on the right shows an alternate arrangement where the bellows are stationary with the seal gland. This stationary design may be required in higher speed applications.

The default face materials for the Type B seal are Silicon Carbide versus premium grade blister resistant carbon. The standard O-ring materials is a fluoroelastomer (or FKM) such as Viton. The default bellows material is Alloy C-276. The applies only to the diaphragms of the bellows and not the adapter or face flange materials. All other metal parts including the sleeve and gland are 316SS. A throttle bushing in the gland is required for all single seals.

The Type C seal is designed for high temperature applications. Like the Type B seal, it is a bellows seal.

The default configuration is shown on the left. This is a stationary bellows with the bellows assembly attached to the gland. The rotating configuration, shown on the right, is an option and is generally used in dual seal arrangements.

The default face materials for the Type C seal are Silicon Carbide versus premium grade blister resistant carbon. The standard secondary gasket materials is a flexible graphite. The default bellows material is Alloy 718. The applies only to the diaphragms of the bellows and not the adapter or face flange materials. The face flange is generally a low expansion alloy to maintain the shrink fit to the seal face at elevated temperatures. All other metal parts including the sleeve and gland are 316SS. A throttle bushing in the gland is required for all single seals. A bronze anti-coke device is also required. This directs the seal quench (which is generally steam) towards the seal faces to exclude air and minimize coking.

The default Type A and Type B seals have a rotating flexible element but can be provided with a stationary flexible element as an alternate. The default Type C seal has a stationary flexible element but can be provided with a rotating flexible element as an alternate. So, each of the seal Types can be provided with either rotating or stationary flexible elements. When should you choose one over the other?

If the surface speed at the seal faces exceeds 4500 ft/min (or 23 m/s), API 682 states that a stationary flexible element must be used.

In applications requiring a distributed flush, a rotating flexible element should be considered first.

The user should generally stay with the default selection unless there is a technical reason to change to the alternate.Now that we have defined the basic seal types, we must look at the options of how these are package for a specific application. The seal arrangement defines the number of seals, their orientation, and details about their operation.

The First Edition was limited to only liquid mechanical seal. These are referred to as contacting wet seals. The Second Edition has introduced two new options: containment seals (either non-contacting or contacting dry-running) and non-contacting seals (as wet running primaries or dual dry-running). We need to examine these options before we can discuss seal arrangements.The Contacting Wet seal is a typical liquid mechanical seal. This seal is designed to run on a liquid fluid film. This liquid provides lubrication and hydrostatic support of the fluid faces. The faces are generally flat and do not have any face features so this design does not intentionally create hydrodynamic forces to separate the faces. In a good running seal, the faces are operating with a fluid film on the order one-half a micron.

Because this design requires liquid across the faces, the application requires that there is a vapor suppression (or a vapor pressure margin) to keep the fluid in a liquid phase.

This seal is designed to run under full operating conditions for a minimum of 25,000 hours.

This abbreviation CW is used to designate this seal design.A Containment Seal is designed as a dry running backup seal. It is always the outer seal in a dual non-pressurized seal arrangement. This seal can be either a non-contacting (lift-off) design or a contacting design.

The Containment Seal will operate under relatively low-duty conditions for the life of the seal. It will normally be exposed to only buffer gas or vaporized process fluid. Normal emissions past the primary seal are prevented from reaching atmosphere by the Containment Seal. When the inner seal fails, the Containment Seal can operate under full seal chamber conditions until the pump can be shutdown for seal replacement.

The Containment Seal is designed to run for the life of the primary seal (or at least 25,000 hours) under a maximum pressure of 10 PSI. Since the containment seal chamber is normally connected to the flare or a vapor recovery system, this is realistic. When the inner seal fails, the Containment Seal must operate under seal chamber conditions for a minimum of eight hours. This will allow for an orderly shutdown of the equipment. It was not the intention of the standard that this seal can be run indefinitely with a failed inner seal.

This abbreviation CS is used to designate this seal design.

The last seal design is a Non-Contacting seal. This seal can be used as a dual pressurized gas seal or as a inner seal (of a dual non-pressurized seal arrangement) running on process fluids.

The most common use for this design is in dual gas seals. Here the seals operate on a barrier gas provided from an outside source through a control panel.

The use of a Non-Contacting seal as a primary seal can be traced back to applications where the fluid on the primary seal may be impossible to keep in a liquid state.

A Non-Contacting seal is designed to create hydrodynamic forces to separate the faces under all operating conditions. This hydrodynamic lift is created by the use of shallow waves, grooves, or slots. Since these faces are separated by a greater distance than liquid seals, there is normally a higher leakage rate. These seals are also designed to run for a minimum of 25,000 hours.

This abbreviation NC is used to designate Non-Contacting seals.This chart shows the available Arrangements and Configurations under API 682 Second Edition. The First Edition allowed only three options. The Second Edition has grown to eleven options due to the expansion of the scope and addition of new seal types.

The first column is for Arrangement 1 seals or single seals.

The second column is for Arrangement 2 seals. These are two seals in series with a containment seal chamber pressure less than seal chamber pressure. These are also called a dual unpressurized seals. There are three configurations available for this arrangement depending upon the state of the barrier fluid and the design of the primary seal.

The third column is for Arrangement 3 seals. These seals are operated with a barrier maintained at a pressure above the seal chamber pressure. These are also called dual pressurized seals. Under Arrangement 3, the column on the left is for seals operating with a liquid barrier fluid while the column on the right is for seals operating with a gas barrier fluid. The configurations shown in each column describe the orientation of the two seals.

It is important to understand these Arrangements and Configurations and their relationships to each other. Please take a moment to review this chart. We will cover each configuration in more detail on the following slides.The Arrangement 1 seal is a single contacting wet seal. There is only one seal per cartridge.

The design features on the illustration is only meant to show the basic seal and orientation. Some of the features shown may or may not be required depending upon other parts of the standard. For example, the bushing may be either a fixed or floating bushing and the flush may be either a single point or distributed (multiport) injection.

This would be a good point to look at the configuration nomenclature. For Arrangement 1, there are two configurations. These are designated as 1CW-FX and 1CW-FL. The first digit, 1, defines this as an Arrangement 1 seal (or single seal). The next two digits, CW, define this as a Contacting Wet seal. The final two digits indicate whether the seal has a fixed (FX) or floating (FL) bushing.

This is the most common seal arrangement.There are several variations of the Arrangement 2 seal but all of them have one thing in common the buffer fluid (liquid or gas) is maintained at a pressure lower than the seal chamber pressure.

The first configuration we will look at is the 2CW-CW configuration. This seal is an Arrangement 2 (the first digit) with the inner seal as a Contacting Wet seal (the next two digits) and the outer seal as a Contacting Wet seal (the last two digits). Basically, this is a dual non-pressurized seal with a liquid buffer fluid.

This is the same seal that was designated as the Arrangement 2 seal from the First Edition.

The 2CW-CS configuration is an Arrangement 2 seal with a Contacting Wet inner seal and a dry-running Containment Seal (CS) for the outer seal. This is the traditional liquid inner seal with a dry running backup seal. The Containment Seal may be either a contacting or non-contacting design.

Notice in the subtitle the designation of Vapor or No Buffer Fluid. A buffer fluid is defined as an externally supplied fluid.. In some cases the buffer fluid cavity will be swept with a buffer gas such as Nitrogen. This would be the Vapor Buffer Fluid condition. In other cases, it will run on vaporized process fluids. Since the vaporized process is not externally supplied, it is considered as running on No Buffer Fluid by the standard. Just some trivia for you.The 2NC-CS configuration is an Arrangement 2 with a Non-Contacting inner seal and a Containment Seal for the outer seal. The inner seal is designed to be non-contacting and can operate on either a liquid, vapor, or mixed phase process. The outer seal is a Containment Seal.

This configuration requires a little more background. In most cases, the inner seal of an Arrangement 2 seal is a Contacting Wet seal running on the liquid process fluid in the seal chamber. Because the seal is designed to run on a liquid, the standard requires that the pressure in the seal chamber is greater than the vapor process fluid. To insure that it stays a liquid, the vapor pressure margin should be on the order of 50 PSI.

In most cases this can be achieved with the proper piping plan. In some cases though, the vapor pressure margin may be impossible to maintain. This is especially true in service with very light hydrocarbons. For these applications a Non-Contacting inner seal can be designed to operates on the vapor phase process fluids. When there is mixed phase or full liquid phase in the seal chamber, the inner seal will also operate but with higher leakage rates.

All leakage past the inner seal is prevented from going to atmosphere by the Containment Seal. The Containment Seal chamber is vented to a vapor recover system. This configuration has seen only limited applications in the field.

Arrangement 3 seals are dual pressurized seals with the barrier fluid maintained at a pressure higher than the seal chamber pressure. There are two major subdivision under this arrangement those with a liquid barrier and those with a gas barrier.

The 3CW-FB configuration is an Arrangement 3 seal with Contacting Wet seals (that is a liquid barrier fluid) in a series or face-to-back (FB) orientation. This is also called a dual pressurized liquid seal. The face-to-back configuration is the default configuration for the standard. This means that it is the preferred orientation of the seals. This is also the Arrangement 3 configuration described in the First Edition.

The reason the face-to-back orientation has been selected as the default has to do with the failure mode of the seal. If the outer seal fails and there is a loss of barrier fluid and pressure, the inner seal will be OD pressurized and the inner seal will function as a single seal.Other orientations are available in Arrangement 3 liquid seals. The 3CW-BB (back-to-back) or 3CW-FF (face-to-face) orientations are also acceptable. This may be required for specific applications or pump designs.The other major subcategory under Arrangement 3 is the gas barrier fluid seals. These are also called dual gas seals. These have seen widespread use throughout the refinery and chemical industries since the introduction of the First Edition.

The 3NC-BB seal is the default Arrangement 3 gas seal. This is an Arrangement 3 Non-Contacting seal in a back-to-back orientation. This has been the most widely used orientation for these seals.

Other orientations are also recognized by the standard. These alternates include the 3NC-FF (face-to-face) and 3NC-FB (face-to-back) orientation. As with the liquid seals, there may be applications where these alternate designs are more suitable.One of the biggest complaints of the First Edition was that it specified a seal that was designed with all of the features required for severe duty in a hazardous service. While this addressed many of the needs of a refinery, it proved to be overkill for low duty application. The end users and Task Force recognized that different applications may require different levels of seal sophistication.

Until the release of the Second Edition, this was handled by users specifying modified API-682 seals. This lead to such requests as design it like a 682 seal except without the or design it in the spirit of 682. This defeated some of the benefits of having a standard.

With the inclusion of more pump types (with smaller seal chambers) many of the required features may not physically fit in the smaller installation envelope.

And last but not least, the users recognized that the new seals were often more expensive than non-682 seals. If the extra features improved seal performance, this could be justified. If the extra features were not required, it became more difficult to use the new seal.

All of these factors lead the Task Force to consider creating sub-specifications within the 682. These would describe seals for different levels of severity, operating windows, design features, and documentation. These have been designated as seal Categories.The Second Edition defines three seal Categories:

Category 1 seals are designed for general duty services. They are to be installed into the smaller chemical duty pumps in lower pressure and temperature applications.

Category 2 seals are similar to the seals defined in API-610 7th edition. These are heavy duty refinery seals used in API 610 pumps. They do not however require all of the features of the API-682 First Edition seals.

Category 3 seals are for heavy duty services requiring all of the features necessary for severe applications. This is essentially the same seal that was defined in the First Edition.Here is a chart showing a comparison of some of the features of the three seal Categories. This is taken from Annex A of the Second Edition. You need to study this in detail but well go over it briefly now.

Category 1 seals are designed for the ANSI/ASME B73.1 and B73.2 big bore seal chambers as well as the ISO 3069 Frame C seal chambers. The Category 2 and 3 seals are for API-610 pumps.

The temperature range for the Category 1 seal goes up to 260C (500F) while Categories 2 and 3 go up to 400C (750F). Category 1 seal have applications up to 22 bar (315 PSIA) while Categories 2 and 3 are up to 42 bar (615 PSIA).

The default face materials for Category 1 seals are direct sintered SiC vs Carbon. This is because these seals will likely be exposed to more corrosive environments in chemical pumps. The default material for Categories 2 and 3 is reaction bonded SiC vs Carbon.

Distributed flush is required for Category 3 seals. The default for Categories 1 and 2 is a single point injection unless the users specifies a distributed flush or there in inadequate vapor pressure margin in the application. The criteria to determine this is in the standard.

All seals require the gland to make metal-to-metal contact with the seal chamber face. In a Category 1 seal, it is only necessary to have contact inside the stud circle. Categories 2 and 3 require contact both inside and outside the stud circle.While there are some specific shaft sizes used in the ANSI/ASME and ISO pumps, there is some variation in what is actually supplied by OEMs. For this reason, there are no defined seal shaft sleeve increments for Category 1 seals. Category 2 and 3 seals are designed for the 10mm shaft size increments used in API-610. In practice, the seal OEMs will supply seals in whatever size the customer orders.

Category 1 single seals require a fixed Carbon throttle bushing in the gland. A floating bushing is optional. The Category 2 seal requires a fixed non-sparking metal bushing with a floating Carbon bushing as an option. A Category 3 seal requires a floating Carbon bushing.

Pumping ring HQ curves are required for Category 3 seals.

We will be discussing seal qualification testing in a later module. For now, note that Category 3 seals require testing as complete assembly. Category 1 and 2 seals can be designed from components that have been previous qualified in different tests.

The remainder of the differences apply to the level of documentation required for each seal. Categories 1 and 2 require minimal documentation to help reduce the cost to both the user and the OEM. Category 3 require extensive documentation from both the user and the seal OEM.

While the concept of Categories introduces a level of complexity to the standard, ultimately they will allow the most appropriate seal to be applied for a service without introducing unnecessary features, costs, or documentation.API 682 Second Edition represents a major revision over the First Edition. This was driven by many factors including end-user requests and a desire to capture the latest sealing technologies. The Task force was made up of one third refineries, one third chemical plants, and one third OEMs. This produced a standard that is hopefully addresses the needs of all parties successfully.

The standard maintains the use of three seal Types as introduced in the First Edition.

There also remain three seal Arrangements although the allowable configurations under them has increased to address the increase in scope of the standard.

And lastly, the concept of seal Categories has been included to address the needs for differing levels of features and documentation.

api 682 overview

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