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Swagelok Quebec Group

Your Authorized Swagelok Sales and Service Center

API Plan 52 Buffer Liquid Seal Pot

API Plan 52 utilizes a reservoir and circulates an unpressurized buffer fluid between the inboard and outboard seals. To provide positive circulation through the support system and into the seal, a pumping ring is employed. Frictional losses in the buffer fluid inlet and outlet lines should be minimized by selecting the proper tube size, using large radius and/or 45 degree bends, and reducing the length of tubing runs. Plan 52 is commonly used with light hydrocarbons or fluids with a high vapor pressure. The buffer fluid must be compatible with process fluid as inboard seal leakage will eventually mix with the buffer fluid.

Plan 52 


  • Provides additional heat removal from the inner seal when required
  • Acts as a secondary seal to prevent process fluid leakage to atmosphere

See page 27 of the Mechanical Seal Support Systems Applications Guide for additional details.


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