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API Plan 01

Internal recirculation from pump discharge to the seal chamber.

API Plan 01


The API Plan 01 is suited to applications where process fluids could easily thicken or freeze within the piping. Plan 01 permits fluid circulation from the discharge area to the seal chamber.

Application Notes

  • Used with fluids which are at risk of freezing, thickening, or solidifying in external piping.
  • Same concept as Plan 11, without the external piping.
  • Raises the seal chamber pressure.
  • Vents the seal chamber during flooding of horizontal pumps.
  • The seal chamber is not self-venting in vertical applications.
  • May only be used with clean fluids.
  • The flush is not usually directed right at the faces but may come in over the seal head.


  • Works like Plan 11 without the need for external piping
  • Improves seal pressure and vents seal chamber when horizontal pumps are flooded


  • Lacks self-venting capability in vertical pumps
  • Clean fluids are required for operation
  • Flush may bypass seal face

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