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API Plan 11

Recirculation from pump discharge through a flow control orifice to the seal chamber.

API Plan 11


This is the default seal plan for all Arrangement 1 and 2 seals.

Application Notes

  • Default seal flush plan for all Arrangement 1 and 2 seals.
  • Fluid flows from the seal chamber back into the process stream.
  • Important to determine the required flush flow rate (especially for high-head applications) and select proper orifice and throat bushing dimensions to assure adequate flow.
  • Can be used without a flow control orifice for some low differential head or high viscosity applications.
  • Provides cooling for the seal.
  • Vents air or vapors from the seal chamber in horizontal pumps.
  • Applicable for all general duties with sufficient pressure differential.
  • Polymerizing fluids can cause clogging of the orifice and piping.
  • Should not be used with fluids which are at risk of freezing, thickening, or solidifying in external piping.


  • Will provide adequate cooling for seals
  • Effective air or vapor venting in horizontal pumps
  • Useful as a general duties plan


  • Using polymerizing fluids with this seal plan will lead to clogging of the orifice and pumps
  • Not suitable for use with fluids that might freeze or thicken within external piping

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