API Plan 65B

API Plan 65B

Atmospheric leakage collection and detection system for condensing leakage. Failure of the seal will be detected by a cumulative leakage into the system.

A  From mechanical seal
B  To liquid collection system
C  Valve (locked open)
D  Valve (normally closed)

Seal chamber details

3  To liquid collection system
4  Flush (F)
5  Quench (Q)
6  Drain (D)
7  Seal chamber

Example seal: EagleBurgmann LL9UC single pusher mechanical seal.

P&ID according to API


1  Valve (locked open)
2  Drain valve
3  To liquid collection system
5  Quench (Q)
6  Drain (D)

LIT  Level transmitter with local indicator


  • Uses the Plan 61 drain connection.
  • Collects the leakage from a single seal in a leakage collection reservoir.
  • Is equipped with a level transmitter with a high level alarm.
  • This plan is used with a floating or segmented bushing or a similar containment device.
  • Identical to Plan 65A except that it uses a normally closed valve in place of the orifice of Plan 65A.


  • For single seals with expected condensing leakage.
  • Generally for horizontal pumps.


Remarks, checkpoints

  • It must be ensured that the valve downstream of the reservoir is always kept closed during operation of the pump.
  • Drain connection on the gland must be at the bottom-most position (6 o’clock).
  • The valve below the gland (1) should always be kept open during pump operation.



Pump media characteristics

  • Condensing, medium temperature fluids

Location, function

  • Atmospheric side
  • Leakage collection, detection and alarm



2CW-CW*, 3CW-FB*, 3CW-BB*, 3CW-FF*

* Remark: The configurations listed for each individual piping plan are to be understood as recommendations including possible utilizations which may also be applied.


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