dual seal piping - calgary pump...

Piping Plans for Dual Mechanical Seals

Purpose of Piping Plans

�Create a more favorable environmentfor the mechanical seal

• Flushing to remove heat

• Lowering fluid temperature

• Altering the seal chamber pressure

• Cleaning the process fluids

• Control atmospheric side of seal

Purpose of Piping Plans

�Provide a means of detecting andcontrolling seal leakage

• Capture and/or prevent leakage

• Detect leakage

• Route leakage to appropriate collection

or disposal system

• Provide fluid other than process fluid for

the seal environment

Requirements of Mechanical Seals

�Liquid seals

• Stable fluids

• Good lubricating properties

• Fluids do not flash or vaporize in seal

chamber

• Free from contamination and solids

• Moderate viscosities

Requirements of Mechanical Seals

�Gas seals

• Gas or vapor suitable for sealing

• Constant supply of external buffer/barrier

gas

• Process fluids free from contamination

from both liquids and solids

• Process fluids which are not adversely

affected by gas leakage

Methods of Achieving Goals

�Piping or routing of process fluids

�Introduction of external fluids

�Auxiliary equipment

• Seal coolers

• Cyclone separators

• Reservoirs

�Instrumentation

Plan 52What• Unpressurized buffer

fluid circulationthrough reservoir.

• Fluid is circulated bya pumping ring in thedual seal assembly.

Plan 52Why• Outboard seal acts

as a safety backupto the primary seal.

• Zero to very lowprocess emissions.

• No processcontamination isallowed.

Plan 52Where• Used with dual

unpressurized seals(“tandem”).

• High vapor pressurefluids, lighthydrocarbons.

• Hazardous or toxicfluids.

• Heat transfer fluids.

API 682 Type A Arrangement 2

2CW-CW

Plan 52Preventative

Maintenance

• Piping loop mustself-vent to vaporrecovery/flaresystem nearatmosphericpressure.

• Process vaporpressure is generallygreater thanreservoir pressure.

• Buffer fluid must becompatible withprocess leakage.

Plan 52Preventative

Maintenance

(continued)• Primary seal leakage

is indicated byincreased ventpressure.

• Reservoir level gageindicates outboardseal leakage.

Plan 53AWhat• Pressurized barrier

fluid circulationthrough reservoir.


Plan 53AWhy• Isolate process

fluids.

• Zero processemissions.

Plan 53AWhere• Used with dual

pressurized seals(“double”).




• Dirty, abrasive orpolymerizing fluids.

• Mixers or agitators.

• Vacuum service.

API 682 Type C Arrangement 33CW-FB

Plan 53APreventative

Maintenance

• Piping loop mustself-vent to reservoirlocated at highestelevation.

• Pressurize reservoirat all times,maximum gascharge 150 - 200 psi(10 - 14 bar)

• Barrier fluid must becompatible withprocess.

• Reservoir level gageindicates both IB andOB seal leakage.

Plan 53BWhat• Pressurized barrier

fluid circulation witha bladderaccumulator.


Plan 53BWhy• Isolate process fluid.


• Higher pressure thanPlan 53A.

Plan 53BWhere• Used with dual





• Dirty, abrasive orpolymerizing fluids.

API 682 Type C Arrangement 3

3CW - BB

Plan 53BPreventative

Maintenance

• Piping loop must befully vented beforestarting.

• Accumulator must bepressurized at alltimes, usually by gascharge.


• Regularly monitorbarrier pressure –manually add barrierfluid when pressuredecays.

Plan 53CWhat• Pressurized barrier

fluid circulation witha pistonaccumulator.


Plan 53CWhy• Isolate process fluid.


• Higher pressure thanPlan 53A.

• Dynamic tracking ofsystem pressure.

Plan 53CWhere• Used with dual





API 682 Type A Arrangement 33CW - BB

Plan 53CPreventative

Maintenance


• Reference line musttolerate processcontaminationwithout plugging.


• Reservoir level gageindicates bothinboard andoutboard sealleakage.

Plan 54What• Pressurized barrier

fluid circulation by anexternal system.

Plan 54Why• Isolate process fluid.


• Seal cannot inducecirculation.






• Dirty, abrasive, orpolymerizing fluids.

• Mixers or agitators.

API 682 Type C Arrangement 3

3CW - BB

Plan 54Preventative

Maintenance


• Circulating systemmust be pressurizedand energized at alltimes.


• Circulation systemlevel gage indicatesboth inboard andoutboard seal leakage.

Plan 72What• Unpressurized buffer

gas control system.

• Containment sealsupport typically withnitrogen buffer gas.

Plan 72Why• Zero to very low

process emissions.

• Safety backup toprimary seal.


unpressurizedcontainment seals(“tandem”).



• Clean, non-polymerizing, non-oxidizing fluids.

• Used in combinationwith Plan 75 and/orPlan 76.

API 682 Type A with Containment

2CW - CS

Plan 72Preventative

Maintenance

• Clean, reliable, lowpressure gas must besupplied to seal at alltimes.

• Bottled gas supply isnot recommendedexcept as part of anemergency backupsystem.

• Primary seal leakage isindicated by pressurein the vent line.

Plan 72Preventative

Maintenance

(continued)

• Vent or drain areusually connected tolow pressure vaporrecovery/flare system.

Plan 74What• Pressurized barrier gas

control system.

• Gas seal supporttypically with nitrogenbarrier gas.

Plan 74Why• Isolate process fluid.



pressurized gas seals(“double”).



• Services that do nottolerate barrier fluids.

• Clean, non-polymerizing fluids.

• Moderate temperaturefluids.

Plan 74Preventative

Maintenance

• Clean, reliable,pressurized gas mustbe supplied to seal atall times.

• Barrier pressure istypically at least 25 psi(1.75 bar) above sealchamber pressure.

• Flow meter indicatesboth inboard andoutboard seal leakage.

Plan 74Preventative

Maintenance

(continued)

• Bottled gas supply isnot recommendedexcept as part of anemergency backupsystem.

Plan 75What• Drain from containment

seal cavity to liquidcollector and vaporrecovery.

Plan 75Why• Leakage collection for

zero to very lowprocess emissions.

• Safety indicator forprimary seal.

Plan 75Where• May be used alone or

with Plan 72 oncontainment seals.

• Fluids that condense atambient temperature.

• High pressure fluids,light hydrocarbons.




2CW - CS

Plan 75Preventative

Maintenance

• Collection reservoirmust be located belowseal drain anddownward-slopedpiping.

• Continuously ventcollection reservoir tolow pressure vaporrecovery/flare system.

• Drain collectionreservoir to liquidrecovery system asneeded.

Plan 75Preventative

Maintenance

(continued)

• Primary seal leakage isindicated by increasedvent pressure.

• Monitor regularly forliquid level, valvesettings, and low ventpressure.

Plan 76What• Vent from containment

seal cavity to vaporrecovery.

Plan 76Why• Leakage collection for

zero to very lowprocess emissions.

• Safety indicator forprimary seal.

Plan 76Where• May be used alone or

with Plan 72 oncontainment seals.

• Fluids that do notcondense at ambienttemperature.





2CW - CS

Plan 76Preventative

Maintenance

• Continuously vent tolow pressure vaporrecovery/flare system.

• Vent piping shouldinclude a condensatedrain.

• Primary seal leakage isdetected by increasedvent pressure.

• Monitor regularly forvalve settings, blockedlines, and low ventpressure.

Good Piping Practices

�Minimize line losses

�Large diameter tubing

�Upward sloping lines

�Long radius bends

high point vent

Vertical

Equipment

Horizontal

Equipment

18 - 24 in.

(0.45 - 0.6 m)

3 ft. (0.9 m) max

low point drain

Plan 23 Example

Good Piping Practices

�Minimize line losses

�Large diameter tubing

�Upward sloping lines

�Long radius bends

Vertical

Equipment

Horizontal

Equipment

18 - 24 in.

(0.45 - 0.6 m)

4 ft. (1.2 m) max

low point drain

Plan 53A Example

Review

�Intended to create a more favorableenvironment for the seal

�Collect and detect seal leakage and providesafety backup

�Documented in several API, ASME, and ISOstandards

�May require auxiliary equipment or externalsources of fluids

�Necessary to improve seal reliability/Safety

Questions?

dual seal piping - calgary pump...

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