API Plans 21 & 23

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API Plan 21

Recirculation from pump discharge through a flow control orifice and cooler into the seal chamber.

Required Media Characteristic-

  • Hot, non-polymerizing clean fluids typically less than 176 °C

  • Fluids with low vapor pressure margin in seal chamber

  • Fluids with poor lubrication

  • Not suitable for fluids with high solid content

Feature -

  • Cool flush is provided to the seal.

  • This plan  is self venting 

  • It reduce coking and improve lubricity

  • Potential plugging on process side if fluid viscosity rises quickly


API Plan 23
Recirculation from a circulation device in the seal chamber through a cooler and back into the seal chamber.

Required Media Characteristic-

  • Clean , non-polymerizing, High temperature fluid, Hot hydrocarbons, Hot water services above 80 °C (176 °F) etc.

  • Fluid close to vaporization point.

  • Applications where increasing seal chamber pressure to improve vapor pressure margin is not possible.

Feature -

  • Product in seal chamber is isolated from rest of pump by throttling bush.

  • Pumping Ring is used for fluid circulation, It is more efficient than Plan 22

  • It increase product temperature margin.




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