API682 Overview

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PuMPs & systeMs www.pmp-zon.com May 2007 31

understanding o the requirements o the second edition.

DimensionSince the second edition, the standard has been written as anISO standard and all dimensional data have been presented inSI units. U.S. customary units are also given in parentheses as asecondary reerence. The user will speciy whether data, draw-ings, hardware (including asteners), and equipment suppliedto this standard will use SI units or U.S. customary units.

Seal CategoriesSeal categories were introduced in the second edition and aresubspecications within the standard. Beore dening a cat-egory, it would be helpul to understand why they were cre-ated. The rst edition specied a seal designed or demand-ing services. This included eatures such as a distributed fusharrangement and foating throttle bushing on all single seals.These eatures made these seals larger and more costly thanrequired or many general duty applications.

For these applications, some users have specied sealsthat had only some o the eatures required on a standard seal.

Customers reerred to these seals as being designed in thespirit o 682 or with the intent o 682. It was clear that allthe eatures required by the rst edition were not required orevery application. As the standard was expanding the scope toinclude more chemical pumps, it was seen as inevitable that thispractice would continue.

It was also critical to recognize that chemical duty pumpsand their seals were intended to be applied in a smaller operat-ing window than the traditional rst edition seals. Most chem-ical duty pumps are designed to operate at lower pressures and

temperatures than the API 610 pumps, so it was consistent tocreate a seal category that refected the pumps capabilities. A seal category is a subspecication that denes the

intended pump, operating window, materials, design eatures,and documentation requirements or the seal. There are threecategories, dened as Category 1, 2, and 3. A Category 1 sealis a seal intended or chemical duty pumps. A Category 2 sealis intended or API 610 (ISO 13709) pumps in renery ser-vices requiring ewer eatures than a 682 rst edition seal. TheCategory 3 seal is intended or API 610 pumps and is basicallythe same seal dened in the rst edition. Table 1 outlines someo the eatures and requirements or each category.

Feature Category 1 Category 2 Category 3Seal chamber size ANSI ASME B73.1 and

B73.2, ISO 3069 Frame

C

API-610, ISO 13709 API-610, ISO 13709

Temperature range -40F to 500F -40F to 750F -40F to 750F

Pressure range, absolute 315 PSI 615 PSI 615 PSI

Face materials Premium blister resistantcarbon versus selfsintered silicon carbide

Premium blister resistantcarbon versus reactionbonded silicon carbide

Premium blisterresistant carbon versusreaction bonded siliconcarbide

Distributed flushrequired for single sealswith rotating flexibleelements

When specified bypurchaser or required inlow vapor pressuremargin applications

When specified bypurchaser or required inlow vapor pressuremargin applications

Required

Throttle bushingrequirements for single

seals

Fixed carbon bushingrequired. Purchaser may

specify floating carbonbushing

Fixed non-sparkingmetal bushing required.

Purchaser may specifyfloating carbon bushing

Floating carbon bushingrequired

Scope of vendorqualification test

Tested as Category 1seal unless faces areinterchangeable withpreviously tested seals

Tested as Category 2seal unless faces areinterchangeable withpreviously tested seals

Testing required ascomplete cartridgeassembly

Proposal datarequirements

Minimal Minimal Rigorous

Contract data

requirements

Minimal Minimal Rigorous

Table 1. Comparison o eatures o categories.


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32 May 2007 www.pmp-zon.com PuMPs & systeMs

Seal Solutions

Seal TypesThe seal type denes the basic designo a seal as well as the materials o con-struction. These are largely unchangedrom the rst edition. Seal types are

dened as Type A, B, or C. The TypeA seal is a pusher seal with a rotatingfexible element, silicon carbide versuscarbon aces, alloy C-276 springs, fuo-roelastomer O-rings, and 316 SS metalcomponents (see Figure 1).

A Type B seal is a bellows seal witha rotating fexible element, silicon car-bide versus carbon aces, alloy C-276diaphragms, fuoroelastomer O-rings,and 316 SS metal components (seeFigure 2).

A Type C seal is a bellows seal witha stationary fexible element, siliconcarbide versus carbon aces, alloy 718diaphragms, fexible graphite second-ary seals, and 316 SS metal components(see Figure 3).

In the rst edition, all seals wereassumed to be contacting wet seals.Although there have been many livelydiscussions about whether standardliquid mechanical seals are contactingor not, or the purpose o this standardthey are designated as contacting wet

(or CW) seals. The second edition introduces two other sealdesigns: the containment seal and the non-contacting seal.

A containment seal is a backup seal in a dual unpressur-ized seal arrangement. It is designed to operate at less than 10-psi or the lie o the inner seal. When the inner seal ails, thecontainment seal is designed to run under ull seal chamberconditions or a minimum o eight hours and prevent or mini-mize process fuid leakage to atmosphere. The containmentseal is designated as CS.

A non-contacting seal is a seal that is designed to inten-tionally create a hydrodynamic lit and operate with a specicace separation. This design is used primarily on dual pressur-

ized gas seals. It may also be used on liquid or mixed phaseapplications. This seal design is designated as NC.

Seal Arrangements and ConfgurationsA seal arrangement denes the number o seals in the cartridgeand the pressure in the cavity between dual seals. In the rstedition, seal arrangements were relatively straightorward. AnArrangement 1 seal was a single seal. An Arrangement 2 sealwas a dual seal in a series (ace-to-back) orientation. The buerfuid cavity between the two seals was maintained at a pressurelower than seal chamber pressure. An Arrangement 3 seal was

a dual seal in a series (ace-to-back) orientation with a barrier

fuid pressure greater than the seal chamber pressure.In the latter editions, the same denitions o arrangement

apply, although there are more options available due to theinclusion o containment seals and non-contacting seals. Thismade it necessary to introduce the concept o the seal con-guration. The conguration is a subset o the arrangementand it denes the unction o the seal (contacting wet, non-contacting, or containment seal). It may also dene the type obushing (on a single seal) or the orientation on Arrangement3 seals.

An example o a conguration is 1CW-FL. This would beinterpreted as an Arrangement 1 seal where the inner seal is a

contacting wet (or CW) seal with a foating (FL) bushing. A2CW-CW seal is interpreted as an Arrangement 2 seal wherethe inner and outer seals are both contacting wet (CW) seals.

Arrangement 3 seals have the most options. These sealscan be provided as dual pressurized liquid seal in a variety oorientations. These are contacting wet seals (CW) in a ace-to-back (FB), back-to back (BB), or ace-to-ace (FF) orien-tation. A 3CW-FB is an Arrangement 3 contacting wet sealin a ace-to-back orientation. Arrangement 3 seals can also beprovided as dual non-contacting gas seals (gas barrier fuid) ina variety o orientations. A 3NC-BB is an Arrangement 3 non-contacting seal in a back-to-back orientation. The relationship

Figure 1. Standard and alternative Type A seal.

Figure 2. Standard and alternative Type B seal.

Figure 3. Standard and alternative Type C seal.


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between seal arrangementsand congurations is shown inFigure 4.

On Arrangement 3 seals,the order o the congura-tions shown in Figure 4 des-ignates the order o preerenceas dened by the standard.The deault conguration ora dual pressurized, contacting wet seal is in a ace-to-backorientation (3CW-FB). This was the deault Arrangement3 rom the rst edition. For adual pressurized, non-contact-ing seal, the deault congura-tion is a back-to-back orienta-tion (3NC-BB).

DesignRequirements GeneralThe standard states that itdoes not cover the designo the component parts omechanical seals This reers to therequirements that are typically coveredin standards such as dimensions, allow-able stress levels, and deormations. The

standard does, however, contain a greatnumber o requirements covering every-thing rom O ring sealing suraces todrive collars. The majority o the designrequirements are unchanged rom therst edition. Some o the changes arenoted below.

One o the signicant changes isthe separation o pump and seal stan-dards. Both the API 610 second editionand API 682 ninth edition Task Forcesmade eorts to remove redundanciesbetween the two standards. In API 610ninth edition, most seal requirements,the seal code, and seal piping planshave been eliminated with a reerencemade to API 682. In API 682 secondand latter editions, all shat and sealchamber tabulations have been elimi-nated. All reerences to seal chambersand pump requirements are made backto the original pump specication. Thisis also consistent with the inclusion oASME B73 and ISO 3069 Frame C seal

Figure 4. Seal Confgurations

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Seal Solutions

chambers. The only pump requirements remaining in the stan-dard pertain to the interace between the pump and the seal.

In the rst edition, process connection sizes, orientations,and markings were specied or the three arrangements. In thesecond and latter editions, the greater number o congura-tions along with the dierent seal categories has resulted inan extensive chart detailing the required connections. One othe key objectives is to eliminate the potential or connectingprocess piping to atmospheric connections. In the rst edi-tion, this was accomplished by making all process connections3/4 NPT and all atmospheric connections 3/8 NPT. In thesecond edition, most process connections are 1/2 NPT, atmo-spheric connections are 3/8 NPT, and liquid barrier/buerfuid connections are 1/2 or 3/4 NPT (depending upon theshat diameter).

There are also a greater number o possible connectionsin the second and latter editions. This has resulted in dier-ent connection symbols. Table 2 shows these dierences. All

other connections such as fush (F), cooling (C), drain (D),and quench (Q) remain the same.

In addition to the sizes and symbols or connection, thestandard also species the angular orientation o the connec-tions when viewed rom the end view o the seal. All connec-tions that are sel-venting (such as the fush, buer/buer fuidoutlets, and fush outlets) are located at the top o the seal (or0-deg). All connections that unction as a drain (such as thedrain and containment seal drain) are located at the bottom othe cavity (or 180-deg). These locations are dened as the loca-tion where the connection intersects the cavity. This does notrequire the actual connection port to be at this location on the

outer diameter (OD) o the seal gland. This is especially trueor tangential ports where the piping will connect to the glandat some angle o vertical.

The rst edition specied clearances between the innerdiameter (ID) o the seal sleeve and the OD o the shat to bebetween 0.001-in and 0.003-in including tolerances on bothparts. This was independent o the shat diameter. Dependingupon the tolerances o both parts, this could lead to clearancesunder 0.001-in. On larger diameter seals, this created installa-tion and removal problems in the eld. In the second edition,the allowable clearance (along with the tolerances on the sleeveand shat) are dened as F7/h6 according to ISO 286-2. This

has resulted in clearances up to 0.0037-in on the larger sealsizes.The rst edition specied that the deault material or all

seal aces was premium grade, blister-resistant carbon versusreaction bonded silicon carbide. For seals requiring two hardaces, the deault ace materials were reaction bonded siliconcarbide versus nickel bound tungsten carbide. In the secondand latter editions, there is a dierence in the material require-ments or dierent seal categories.

Since a Category 1 seal will typically be used in a chemicalpump, the deault ace materials are premium grade, blister-

resistant carbon versus sel-sintered silicon carbide. Categories2 and 3 are the same as the rst edition (premium grade, blis-ter-resistant carbon versus reaction bonded silicon carbide).For seals requiring two hard aces, the deault material or both

aces is silicon carbide.

AccessoriesSeal CoolersA seal cooler is used to reduce the temperature o the fuid inthe seal chamber. This is oten done to increase vapor pres-sure or improve fuid properties or the seal. The rst editionoutlined some o the construction details or seal coolers. Ingeneral, all seal coolers had to be designed with process fuidon the tube side and cooling water on the shell side. Both thetube and shell sides had to be completely drainable. Piping orthe tube was required to be -in tube with a minimum 0.095-in wall thickness.

The second edition maintains these requirements, butadded an additional smaller size cooler or smaller shats. Forshat sizes o 2.500-in or less, a cooler with -in tubing anda minimum wall thickness o 0.065-in is specied. For shatslarger than 2.500-in, a seal cooler with -in tubing and aminimum 0.095-in wall thickness should be used. O course,the primary consideration in selecting a seal cooler must beadequate heat removal. This may result in a larger seal coolerbeing applied to a seal with a shat diameter under 2.500-in.

Barrier/Buffer Fluid Reservoirs

Reservoirs are used on Plan 52 and Plan 53A piping plans toprovide buer and barrier fuids to the seals. The rst editionhad detailed requirements or the dimensions, materials, andinstrumentation or these reservoirs. One o these require-ments was that the volume o the barrier fuid in the system atthe normal liquid level was 5-gal. The second and latter edi-tions maintain most o the same requirements or reservoirsbut have added a smaller size reservoir or smaller shat sizes.For shats with a diameter o 2.500-in and smaller, the stan-dard reservoir shall have a capacity o 3-gal at normal liquidlevels. For shats larger than 2.500-in, the capacity should be a

Symbol Description

FI Flush In (Plan 23 only)

FO Flush Out (Plan 23 only)

LBI Liquid Barrier/Buffer Fluid InLBO Liquid Barrier/Buffer Fluid Out

GBI Gas Barrier/Buffer Fluid In

GBO Gas Barrier/Buffer Fluid Out

CSV Containment Seal Vent

CSD Containment Seal Drain

Table 2. New Connection Symbols


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minimum o 5-gal as detailed in the rst edition.

Condensate Collection ReservoirThe condensate collection reservoir is a vessel used to collect leakage rom a Plan75 system. This reservoir not only collects the leakage, it also provides a place orliquid and gas phase leakage to separate and be piped to the appropriate recov-ery system. The reservoir will also be instrumented to monitor inner seal leakagethrough both the liquid level and pressure in the reservoir. The standard providesdetails o the construction or this vessel.

Barrier/Buffer Gas Supply PanelsGas supply panels are used on Plan 72 and Plan 74 systems to provide a lteredregulated inert gas to the mechanical seals. The supply panels must have, at a mini-mum, a pressure regulator, coalescing lter, fow meter, low pressure switch, pres-sure gauge, check valve, and isolation valve. A typical arrangement or these com-ponents is shown in Figure 5. The purchaser and seal OEM shall mutually agreeon the instrumentation and general arrangements or the panel.

Figure 5. A typical barrier gas supply panel.

Figure 6. Containment Seal Test Sequence

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Seal Solutions

Seal Qualifcation TestsThe rst edition introduced the con-cept o the standardized seal quali-cation test. Since one o the goalso the standard was to provide seals

with a high probability o achievingthree years o uninterrupted service,it was natural to try to obtain someobjective evidence that this could beaccomplished. Seal testing was doneon a number o representative fuidsunder common operating conditions.In addition to steady-state operation,there were a number o starts andstops along with pressure and tem-perature variations to evaluate theseals on real world conditions.

The second edition continuedwith this philosophy and introducedqualication testing or containmentseals and dual gas seals. Containmentseals are designed or long runs underrelatively low duty conditions. Theirunction during this stage o opera-tion is to isolate the containmentseal cavity rom atmosphere. Per thestandard, the pressure in the sealcavity should be less than 10-psi.The containment seals real workbegins when the primary seal ails. In

this condition, the containment sealmay be operating on high pressurevapors or process fuids. The quali-cation testing is designed to simulatenormal operation as well as ailure othe inner seal (see Figure 6). Leakagesand pressure drops are monitored andrecorded at key points during thetesting.

Dual gas seals are designed torun with barrier gas maintained at apressure higher than the seal chamber

pressure. In actual service, there maybe interruptions in the gas supplythat could aect seal perormance.Qualication testing or these sealsincludes steady-state testing underthe same conditions outlined orliquid seals (see Figure 7). This includes starts and stops alongwith variations in the pressure and temperature o the processfuid.

Ater completing this testing, the seal is exposed to upsetsin the barrier gas supply. The rst phase simulates a complete

loss o barrier gas pressure under static conditions or one hour.The seal is then repressurized and tested at 3600-rpm. Duringtesting, the barrier pressure is isolated rom the supply pres-sure and allowed to decay while the seal continues operation.The pressure is reestablished and allowed to reach equilib-rium. The tester is then stopped, the seal isolated, and pressure

Figure 7. Dual Gas Seal Test Sequence

Figure 8. Standard Seal Flush Plan 14

Figure 9. Standard Seal Flush Plan 53A


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decay measured or 10 minutes.Leakages and pressure drops arealso monitored and recorded atkey points during operations.

All testing o liquid sealsperormed under the rst edi-tion are valid or the secondedition, with one caveat. Therst edition did not dene anacceptance criterion or the sealsduring testing. Basically, it wasup to the seal OEM to determinei the seal was suitable or theservice. While it is still the sealOEMs responsibility to ensurean acceptable seal, there is nowan acceptance criterion. Duringtesting, the seals must main-

tain a leakage rate o less than1000-ppm (as measured by EPAMethod 21) or 5.6-gr/hr. This leakage criterion does not applyto testing o dual gas seals or containment seals under ailureconditions. In addition, the measured wear on the seal acesmust be less than 1 percent o the available wear.

Hydrostatic TestHydrostatic testing is required or allthe pressure boundary o the seal andsupport system. This includes the sealgland, all piping, reservoirs, and other

auxiliary equipment exposed to pro-cess fuids. In the second and lattereditions, there is an exemption or sealglands machined rom a single piece owrought material or bar stock. Cast sealglands still require testing.

AnnexesAPI 682 and ISO 21049 are somewhatunique in their scope. While many stan-dards contain technical specications,these standards include a number o

annexes containing reerences, calcula-tion techniques, and tutorial inorma-tion. About hal the pages in these stan-dards are dedicated to the annexes.

Recommended Seal

Selection ProcedureThe seal selection procedure was intro-duced in the rst edition to give guid-ance to the user in selecting a seal or aspecic application. These applications,

as well as the procedures, are broken down into three processfuids: nonhydrocarbon, nonfashing hydrocarbon, and fash-ing hydrocarbon.

The procedure goes through a number o steps includ-ing selection o the seal type, arrangement, and piping plan.The selection procedure has been revised or the second

Figure 10. Standard Seal Flush Plan 53B

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Seal Solutions

edition to include the new sealdesigns and categories. It also has agreater ocus on the selection o theseal arrangement. The third editionand ISO 21049 have urther revisedthe fowcharts to improve seal andpiping plan selections.

Standard Flush Plansand Auxiliary HardwareThe annexes contain all the standardpiping plans or mechanical seals. While most o these piping plans were also in the rst edition, therehave been several changes to refectdierent technologies and address therequirements o the new seal designs.

Plan 14Plan 14 is a combination o a Plan11 and a Plan 13 (see Figure 8). Thisis most commonly used on verticalpumps where there is a need to pro-vide a fush to the seal chamber whilecontinually venting back to suction.This plan was included in API 610eighth edition and has now beenmoved in API 682 second edition.

Plan 53A Plan 53 is a dual pressurized liquidseal support system. In the rst edi-tion, this was dened as a reservoirthat is pressurized by an inert gas. While this is the most commonmethod o providing a Plan 53, otheroptions also exist. It was dicult tospeciy these options, though, sincethere were no recognized designationsor them or any standardized detailson piping and instrumentation. Thesecond edition has addressed this by

dening three variations o the Plan53: Plan 53A, 53B, and 53C. Thesevariations are considered as techni-cally equivalent. I the user speciesa Plan 53, any o these variations maybe provided.

Plan 53AThis is the Plan 53 as dened by the rst edition (see Figure 9).Barrier fuid is maintained in a reservoir and circulated by themechanical seal. The barrier fuid is pressurized by an external

source such as a regulated supply o nitrogen. The reservoirserves to remove heat rom the barrier fuid as well as providemakeup fuid or normal seal losses. Excessive seal leakage isdetected by a change in fuid level in the reservoir.

The primary disadvantage o this plan is that there is aninterace between the pressurization gas and the barrier fuid. At

Figure 11. Standard Seal Flush Plan 53C




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higher pressures, this can lead to signi-cant gas absorption into the barrier fuidresulting in poor seal perormance.

Plan 53BThis plan replaces the reservoir with abladder accumulator (see Figure 10).The accumulator provides both pressur-ization o the barrier fuid and makeupfuid to compensate or normal seallosses. The bladder separates the pres-surization gas rom the barrier fuid,preventing absorption o the gas at highpressures.

Since the bladder is pre-charged with the pressurization gas, the plancan be operated without a permanentconnection to an external gas supply.

The barrier fuid is circulated by theseal through a loop that includes aseal cooler and other instrumentation.Excessive leakage is detected by a dropin the pressure in the seal loop. Thisplan is normally more expensive than aPlan 53A.

Plan 53C Another variation o this plan uses apiston accumulator (see Figure 11).Pressure rom a reerence source (nor-

mally the seal chamber) is piped tothe bottom o the piston accumulator.Due to the dierences in the areas onthe piston, a higher pressure is gener-ated at the top o the accumulator. Thisis piped into a seal loop. Like the Plan53B, the barrier fuid is circulated by themechanical seal through a seal cooler.With no pressurization gas, there is nochance o gas absorption into the bar-rier fuid.

Since the piston accumulator pres-

surizes the barrier fuid based on thereerence pressure, the barrier pressureautomatically tracks actual operatingconditions including system upsets.One o the disadvantages o this systemis that the accumulator is exposed toprocess fuid. This is a concern in cor-rosive or abrasive applications. In addi-tion, this plan is generally more expen-sive than either the Plan 53A or 53B.

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Seal Solutions

Plan 65Plan 65 was introduced in API 682third edition and ISO 21049. Thisplan is designed to detect seal ail-ures by directing atmospheric leak-age to a small collection vessel (seeFigure 12). Normal seal leakage isallowed to fow through the vessel with minimal restriction. A sealailure resulting in a high leakagerate will fow into the collectionvessel resulting in a higher liquidlevel and a high level alarm. Thisplan should be used with a closeclearance throttle bushing to aidin directing leakage into the collec-tion vessel.

Plan 71The 70 series o piping plansaddresses piping requirements odual gas seals and containmentseals. Plan 71 is designated or sealswhere the containment seal cavityis run dead-ended (see Figure 13).It will also be used when no othercontainment seal piping has beenspecied and the connections areplugged or purchasers use.

Plan 72Plan 72 is an external buer gassupplied to the containment sealcavity through a control panel (seeFigure 14). This plan is providedwhen it is benecial to sweep thecontainment seal cavity with aninert gas. Buer gas is maintainedat a pressure lower than seal cham-ber pressure and less than 10-psi.This plan is almost always used inconjunction with a Plan 75 or 76 to

sweep the buer gas and seal leak-age into a closed collection system.Requirements or the control panelare detailed in the standard.

Plan 74Plan 74 is an external barrier gassupplied to a dual pressurizedgas seal (Figure 15). Barrier gas isprovided at a pressure higher than seal chamber pressure topositively prevent process fuids rom leaking to atmosphere.

Normally an inert gas such as plant nitrogen is used as thebarrier gas. Requirements or the control panel are detailed inthe standard.





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PumPs & systems www.pp-zon.co may 2007 41

Plan 75

A Plan 75 is used to collectleakage into the containmentseal cavity when the processfuid does not completelyvaporize (see Figure 16). Thisleakage may be liquid phase ora mixture o liquid and vaporphases. The accumulation oliquid leakage in a contain-ment seal cavity may adverselyaect seal perormance, soall leakage should be drainedrom the low point drain atthe bottom o the contain-ment seal cavity. The leakage ispiped to a collection reservoirthat is connected to liquid and

vapor recovery systems.Inner seal perormance is monitored by pressurization o

the reservoir and by monitoring the liquid level in the collec-tion reservoir. The inner seal can also be tested by blocking inthe reservoir and noting the time/pressure buildup relationshipin the reservoir. Requirements or the reservoir are detailed in

the standard. This plan may be used by itsel or in conjunctionwith a Plan 72.

Plan 76

A Plan 76 is used to collect leakage into the containment sealcavity when the process fuid completely vaporizes (see Figure


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42 May 2007 www pmp zon com PuMPs & systeMs

Seal Solutions

17). Since containment seals are normally used to prevent orminimize process leakage to atmosphere, the containment sealcavity is piped into a vapor recovery or fare system.

High leakage rates past the inner seal will result in a pres-sure increase between the seal and the orice in the piping.This will be detected by the pressure indicator and high pres-sure switch indicating ailure o the inner seal. Specication orthe piping and instrumentation are detailed in the standard.This plan may be used by itsel or in conjunction with a Plan72.

Annex F Mechanical Seal DatasheetsThe rst edition introduced a very comprehensive set o sealdatasheets. This consisted o ve pages o seal data plus twoadditional pages o pump data. While they were thorough,users seldom, i ever, completely lled these out.

The second edition revised these datasheets so that all thenecessary inormation is contained on two pages. Since thedata requirements and design options are dierent or dier-ent seal categories, there are two sets o datasheets. One set odatasheets covers Category 1 and 2 seals and one set coversCategory 3 seals. These datasheets are provided in both SI andU.S. customary units. These datasheets were urther rened inAPI 682 third edition and ISO 21049.

Annex J Mechanical Seal CodeHistorically, many seal users have relied on the old API 610coding or general designations o mechanical seals. The codeBSTFN (and its many variations) can still be seen on seal andpump datasheets today. While this code was useul, it does notconvey inormation that is required on seal selections in API682 and ISO 21049.

Beore developing the new code, the Task Force investi-gated who was using seal codes. It was determined that the pri-mary users were engineering contractors working on projects.During the project stage, operating conditions or the pumpare dened, but very little is known about the equipment thatwill be used or the application.

At the project stage, the Task Force identied our keypieces o inormation that will be required or the seal OEM toselect a seal: the seal category, the arrangement, the seal type,and the piping plan. The rst position o the code denes the

category and is designated as C1, C2, or C3. The second posi-tion denes the arrangement and is designated as A1, A2, orA3. The third position denes the seal type and is designatedas A, B, or C. The last position denes the piping plan(s) andis designated by the two digit piping plan number. I morethan one plan is required (such as on dual seals), the additionalplans are added to the end o the code.

An example o a new seal code is C1A1A11. This is inter-preted as Category 1 (C1), Arrangement 1 (A1), Type A (A)seal with a Plan 11. An example o a dual seal with multiplepiping plans is C3A2A1176. This is interpreted as a Category

3, Arrangement 2, Type A seal with a Plan 11 on the inner sealand a Plan 76 on the outer seal.

One o the comments made about the new code is that itdoes not include inormation about seal ace and gasket mate-rials. The Task Force considered this and concluded that allseal types have a deault set o materials dened in the stan-dard. I the user desires to speciy alternative materials, thesewill need to be dened outside the seal code.

ConclusionsThis tutorial provides a quick glimpse o API 682 and ISO21049. The user is encouraged to review a copy o the revisedstandard to determine the extent o the changes and its eecton their organization. Overall, API 682 third edition and ISO21049 will allow the benets o API 682 to be applied to agreater number o applications and be used more easily in aglobal market.

AcknowledgementsThe author would like to thank the American PetroleumInstitute or its cooperation and permission to reproduce g-ures or this tutorial. Special thanks go to Andrea Johnson orher behind the scenes work at API during the creation othis standard.

P&S

Bibliography

1. API Standard 682, First Edition, 1994, Shat Sealing Systems or

Centriugal and Rotary Pumps, American Petroleum Institute,

Washington, D.C.

2. API Standard 682, Second Edition, 2001, Pumps Shat Sealing

Systems or Centriugal and Rotary Pumps, American Petroleum

Institute, Washington, D.C.

3. Huebner, M. B., Thorp, J. M., Buck, G. S., and Fernandez, C. L.,

2002, Advances in Mechanical Sealing An Introduction to API

682 Second Edition, Proceedings o the Nineteenth International PumpUsers Symposium, Turbomachinery Laboratory, Texas A&M University,College Station, Texas, pp. 59-65.

Michael B. Huebner is a sta engineer at FlowserveCorporation, Flow Solutions Division, 906 W. 13th Street,Deer Park, TX 77536, 281-479-7325,www.fowserve.com.

Documents

API682 Overview