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Swagelok Quebec Group

Your Authorized Swagelok Sales and Service Center

API Plan 53A

API Plan 53A Barrier Liquid Seal Pot Pressurized by Nitrogen

API Plan 53A utilizes a reservoir and circulates a pressurized barrier fluid between the inboard and outboard seals. The typical source of pressurization is plant nitrogen. The reservoir should be set at least 20 psi (1.3 bar) above maximum seal chamber pressure. This is to ensure that leakage across the inner seal face is barrier fluid which then lubricates the seal faces and passes into the process. For this reason, barrier fluid must be compatible with process fluid and some level of process dilution be acceptable. In order to provide positive circulation through the support system and into the seal, a pumping ring is employed. A reservoir level indicator or level transmitter shows both inboard and outboard seal leakage.

plan 53A 


  • Provides additional heat removal from inner seal when required
  • Is used with a dual seal arrangement when process leakage to atmosphere cannot occur

See page 31 of the Mechanical Seal Support Systems Applications Guide for additional details.


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