API Plan 76

API Plan 76

A containment seal chamber drain for non-condensing leakage on arrangement 2 unpressurized seals with containment seals. Used if the pumped fluid does not condense at ambient temperatures.

A  From mechanical seal
B  To vapor collection system
C  Drain

Seal chamber details

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

Example seal: EagleBurgmann LL9DTUE dual pusher mechanical seal.

P&ID according to API


1  To vapor collection system
2  Tube
3  Pipe
5  Containment seal vent (CSV)
6  Containment seal drain (CSD), closed
7  Gas buffer inlet (GBI), plugged unless used with Plan 72

PIT  Pressure transmitter with local indicator



  • Avoids direct leakage of pumped media to the atmosphere and ensures almost no leakage from the outboard seal.
  • The vapors are directed to the vapor collection system.
  • This plan can be used with buffer gas (Plan 72) or without buffer gas (Plan 71).


  • For non-condensing media – typically high vapor pressure flashing light hydrocarbons.
  • For configurations utilizing an outboard containment seal – contacting or non-contacting type

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 vapor collection system increases. This indicates inboard seal leakage.
  • Ensure that the vent line is always open and an orifice is present to generate back pressure.
  • Ensure a low point condensate drain.
  • Check that the support to the harness piping is sufficient.
  • Use a minimum 1/2 " (13 mm) tubing for the CSV line and ensure that the pipeline rises continuously upwards.
  • Do not use for condensing media.

Pump media characteristics

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

Location, function

  • Between seals
  • Leakage alarm and collection




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