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API Plan 65B

Atmospheric leakage collection and detection system for condensing leakage. Seal failure is detected by cumulative leakage into the leakage collection system.

API Plan 65B


This is an atmospheric loss collection and detection system like Plan 65A. However, seal failure is detected by a cumulative leakage into the collection unit.

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Application Notes

  • Normally used with Arrangement 1 seals in services where seal leakage is expected to be mostly liquid.
  • Identical to Plan 65A except that the orifice is exchanged for a normally closed valve.
  • Leakage is directed from the drain connection in the seal gland into a reservoir resulting in an increase in level of process fluid in the reservoir.
  • Valve below the gland must always remain open during pump operation to allow leakage to flow to the reservoir.
  • Valve below the reservoir should normally be closed during operation but can be periodically opened to drain collected leakage from the reservoir.
  • Reservoir must be mounted below the seal gland to allow leakage to readily flow to the reservoir.
  • A liquid level increase will be monitored by the level transmitter and will activate an alarm.
  • Provides an indication of excessive seal leakage and seal failure without manual inspection.
  • Normal leakage may trigger the alarm over extended periods of time; system requires scheduled draining of reservoir.


  • Easy detection of seal failure by measuring leakage levels
  • Low cost


  • Low leakage rates might not trigger alarms despite seal damage
  • Normal levels of leakage will trigger alarms given time due to their cumulative effect

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