API Plan 75

API Plan 75

A containment seal chamber leakage collection system for condensing or mixed phase leakage on arrangement 2 unpressurized seals with containment seals.

A  From mechanical seal
B  To vapor collection system
C  Drain

Seal chamber details

4  Flush (F)
5  Containment seal vent (CSV), plugged
6  Containment seal drain (CSD)
7  Gas buffer inlet (GBI), plugged unless used with a Plan 72
8  Seal chamber

Example seal: EagleBurgmann H75A4-C dual pusher mechanical seal.

P&ID according to API


1  To vapor collection system
2  To liquid collection system
3  Test connection (if specified)
5  Containment seal vent (CSV), plugged
6  Containment seal drain (CSD)
7  Gas buffer inlet (GBI), plugged unless used with a Plan 72

LI  Level indicator
LIT  Level transmitter with local indicator
PIT  Pressure transmitter with local indicator

* If specified


  • This plan can be used with buffer gas (Plan 72) or without buffer gas (Plan 71).
  • Avoids direct leakage of pumped media to the atmosphere.
  • Liquid leakage is collected in the leakage collector and vapors pass to the collection system.
  • Excessive leakage and the use of an orifice in the outlet line of the collector together leads to a pressure build-up in the collector and triggers a pressure alarm at 0.7 bar (10 PSI) with the help of a pressure transmitter.


  • For condensing media.
  • For configurations utilizing an outboard containment seal – contacting or non-contacting type.
  • Generally used in combination with a Plan 72 nitrogen purge.

Remarks, checkpoints

  • Set the pressure transmitter alarm to a pressure of 0.7 bar (10 PSI) so as to trigger an alarm when the pressure in the leakage collector increases. This indicates inboard seal leakage.
  • Ensure that the vent line is always open and an orifice is present to generate back pressure.
  • Always mount the leakage collection system below the pump centerline.
  • Use sloping lines from the CSD port to the leakage collector.
  • Use the level gauge to ascertain if the leakage collector needs to be drained.

Pump media characteristics

  • Hazardous / environmentally harmful (generally in combination with additional API plan).
  • Clean non-polymerizing fluids
  • Fluids condensing at ambient temperatures.

Location, function

  • Between seals
  • Leakage alarm and collection




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