External buffer liquid reservoir supplying clean fluid to the outboard seal faces.
This plan is used in Arrangement 2 seals and requires the use of an unpressurized external pump seal pot and forced circulation via a pumping ring.
- Used with Arrangement 2 seals.
- Buffer system pressure is typically maintained close to atmospheric pressure.
- Used in applications where product contamination from a barrier fluid is unacceptable.
- Circulation of buffer liquid to and from the reservoir is dependent on thermal siphoning and/or an internal circulating device (pumping ring) inside the seal.
- Used with clean, non-polymerizing, pure products that have a vapor pressure higher than the buffer system pressure.
- Provides redundancy in the event of a seal failure.
- Leakage of higher vapor pressure liquids into the buffer system will flash in the seal reservoir and the vapor can escape into the collection system.
- Near zero process emissions.
- Cooling system is typically built into the reservoir.
- Buffer liquid must be compatible with the process liquid.
- Best piping practices must be followed to avoid vapor entrapment and stalled flow in the tubing.
- No process fluid contamination
- Near-zero process emissions
- Integral cooling system
- Buffer fluid is easily contaminated over time
- Requires strict adherence to best piping practices
- Seal pot maintenance high with process fluids that solidify