• AES Customer focus

API Plan 55


Unpressurised external barrier fluid circulation from a central source.



  1. Ensures higher flow rate, better heat dissipation and positive circulation of buffer fluid.
  2. Buffer fluid maintained less than seal chamber pressure and less than 2.8 bar.
  3. Increases cooler efficiency due to higher flow rate to the heat exchanger
  4. Process fluid does not leak directly to atmosphere.


  1. For media where product dilution is not allowed but leakage to atmosphere diluted form may be allowed.
  2. Preferred for clean, non-polymerizing with high vapour pressure.
  3. May also be used for non-flashing products.
  4. For media with high temperature and/or high heat generation between faces.


  1. Carefully consider reliability of buffer fluid source.
  2. Should not be used for dirty or polymerizing products.
  3. Ensure product is compatible with buffer media.