API Plan 01

API Plan 01

Integral (internal) recirculation from the pump discharge to the seal chamber.

A  Internal circulation

Seal chamber details

1  Inlet
2  Flush (F), plugged (for possible future circulating fluid or for venting on vertical pumps)
3  Quench (Q)
4  Drain (D)
5  Seal chamber

Example seal: EagleBurgmann APItex-S single pusher mechanical seal.

P&ID according to API


  • Plan 01 does not need any external piping.
  • Acts as an internal flushing line for the mechanical seal.
  • Prevents highly viscous fluids from freezing/polymerizing at lower temperatures because the flushing line is not exposed to the atmosphere like in Plan 11.


  • Generally used for horizontal pumps.
  • Highly viscous fluids which tend to thicken, solidify or polymerize.
  • More applicable to ANSI pumps.

Remarks, checkpoints

  • The flow of the flush fluid must be sufficient to remove the heat from the mechanical seal chamber.
  • Unlike in Plan 11, the flush is seldom directed over the seal faces.
  • Not recommended for dirty products as they will tend to clog the flushing line.
  • Not applicable for vertical pumps.

Pump media characteristics

  • Highly viscous media with a tendency to congeal or polymerize when cooled.

Location, function

  • Process side
  • Flushing and cooling



1CW-FL*, 2CW-CS*, 3CW-BB*, 3CW-FF*, 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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