API Plan 32

API Plan 32

Injection of clean fluid into the seal chamber from an external source.

A  From external source
B  To seal

Seal chamber details

1  From external source
2  Flush (F)
3  Quench (Q)
4  Drain (D)
5  Seal chamber

Example seal: EagleBurgmann MBS682 single metal bellows mechanical seal.

P&ID according to API


1  From external source

FI  Flow indicator **
PI  Pressure indicator
TI  Temperature indicator **

** Optional


  • If maintained properly, the best flush plan for single seals or inboard seals in dual seal arrangements (provided media dilution is acceptable).
  • Used in conjunction with a close clearance throat bush to maintain an elevated pressure in the seal chamber and to isolate it from pumped media.


  • Fluids with solids and contaminants where pumped fluid can accept an external flush.
  • To reduce flashing or air intrusion (as in vacuum services).
  • Can be used on horizontal as well as vertical pumps.

Remarks, checkpoints

  • The external flush media should be compatible with the pumped media.
  • Flush media should not vaporize on entering the seal chamber and should be always on – even during start-up and shut-down.
  • Pressure of the external flush should always be at least 2 bar (29 PSI) above seal chamber pressure.
  • Consider economic impact of product dilution, if any.

Pump media characteristics

  • Suspended solids
  • Poor lubrication
  • High temperature
  • Hazardous / environmentally harmful (only in combination with additional API plan).

Location, function

  • Process side
  • Flushing and cooling



3NC-FB*, 3NC-BB*, 3NC-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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