API Plan 55

• Provides lubrication and cooling to the outboard safety backup seal.
• The pumped fluid does not become contaminated.
• The pumped media does not leak directly to the atmosphere.
• Uses an external pump or pressure system to ensure buffer liquid circulation.
• Provides buffer liquid circulation and cooling even though the process pump is in stand-by mode.

• For flashing services – for example light hydrocarbons, high vapor pressure fluids.
• Can also be used for non-flashing service.
• For services where product dilution is not acceptable.
• Where a single system is to be utilized for multiple seals.

• Not to be used for contaminated and polymerizing media.
• Sense the seal inlet and outlet line temperatures. Difference in the temperatures is an indication of proper flow.
• Provide proper instruments like a flowmeter which will indicate outboard seal leakage when the flow increases. Also provide suitable pressure reduction as well as non-return valves in the flushing pipeline.
• The buffer liquid shall be maintained at a pressure less than seal chamber pressure and less than 2.8 bar (40 PSI).
• Ensure the compatibility of buffer liquid with the pump media.
• These systems may need additional engineering depending on application.

• High temperature
• High vapor pressure, flashing media
• Clean, non-polymerizing
• Hazardous / environmentally harmful if leaked directly to the atmosphere.

• Between seals
• Buffer system (p_sealchamber > p_betweenseals)
• Flushing and cooling

2CW-CW