Plan 52 - Dual seals, unpressurised - External reservoir unpressurised liquid buffer
Description: Plan 52 uses an external reservoir to provide buffer fluid for the outer seal of an unpressurized dual seal arrangement.
Advantages: In comparison to single seals, dual unpressurized seals can provide reduced net leakage rates as well as redundancy in the event of a primary seal failure.
General: Cooling coils in the reservoir are available for removing heat from the buffer fluid. Plan 52 is often used where process fluid contamination can not be tolerated.