API Plan 41

API Plan 41

Recirculation from the pump discharge through a cyclone separator delivering the clean fluid to a cooler and then to the seal chamber. The solids are delivered to the pump suction line.

A  Cyclone separator
B  Cooler
C  Temperature indicator
D  Contaminated liquid IN
E  Clean liquid OUT
F  Separated liquid OUT

Seal chamber details

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

Example seal: EagleBurgmann H75VA4-S single pusher mechanical seal.

P&ID according to API


TI  Temperature indicator



  • Plan 41 is a variant of Plan 31 (Plan 31 + cooler).
  • A cyclone separator removes solids and prevents all but a few minor particles from reaching the seal chamber.
  • The media properties retained as solids are routed back to the pump suction.
  • The cooler cools down the media and improves the pressure margin to the vapor pressure.


  • Horizontal pumps conveying hot media with heavy solids.
  • Horizontal pumps conveying hot water with sand or slag inclusions.

Remarks, checkpoints

  • Specific gravity of the solids should be at least twice that of the pumped media. In other cases Plan 32 is recommended.
  • The installation of the pump throat bushing must be ensured.
  • Not applicable for extremely contaminated media. Plan 32 is recommended in such cases.
  • Cooler performance is high and may lead to water side fouling.
  • Can lead to reduced reliability due to abrasive wear inside the cyclone.
  • Routine inspection of the cyclone for abrasive wear is recommended.

Pump media characteristics

  • Suspended solids
  • Poor lubrication
  • High temperature
  • Close to vaporization point

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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