API Plan 53B

Pressurized barrier fluid circulation in outboard seal of dual seal configuration. Circulation is maintained by using pumping ring in running condition and with thermosyphon effect in stand still condition. The pressure is maintained in the seal circuit by a bladder accumulator.   

1. Keeps barrier fluid and pressurized gas (inert gas) separate by using a bladder.  
2. Heat is removed from the circulation system by an air-cooled or water-cooled heat exchanger.  
3. Being a stand-alone system does not rely upon a central pressure source. Hence much more reliable than a Plan 53A.
4. no case media leakage to atmosphere.
5. Clean fluid film formation between the inboard seal faces gives better seal life.  

1. Applications where no leakage to atmosphere can be tolerated e.g. hazardous, toxic, inflammable media.  
2. For dirty, abrasive or polymerizing products where media is unsuitable as a lubricant for inboard seal faces.

1. There will always be some leakage of barrier fluid into the product.
2. Check compatibility of barrier fluid with product.  
3. Low volume of barrier fluid in system, hence heat dissipation is totally dependent on cooler efficiency.
4. Always recharge bladder to 0.9 times the working pressure.
5. Vent the system properly before start up.
6. Product quality can deteriorate due to barrier fluid contamination.
7. Can not be used where seal chamber pressure varies. Use Plan 53C for such applications.