API Plan 72/76 Buffer Gas and Noncondensing Leakage Collection
This panel is a combination of API Plan 72 and Plan 76. The Plan 72 side supplies a buffer gas from an external source between the inboard and outboard faces of a dual seal. For reliable operation, gas seals require a constant supply of clean, dry gas, typically nitrogen. The seal support panel contains a coalescing filter to remove any moisture and particulate present in the supply of plant nitrogen. The clean, dry nitrogen dilutes process leakage from the inboard seal and sweeps it to a collection system. The Plan 76 side collects the primary seal leakage. A pressure regulator on the panel regulates the nitrogen prior to entering the seal chamber. Nitrogen pressure should not be more than 10 psi (0.68 bar) and is typically regulated to the alarm point on the leakage collection system, or at least 5 psi (0.34 bar) above the regular pressure of the flare line.
- Supplies the gas seal with a clean, dry buffer gas, typically nitrogen
- Serves as a containment seal in the event of primary seal failure
- Monitors inner seal leakage that does not condense at ambient temperatures
See page 67 of the Mechanical Seal Support Systems Applications Guide for additional details.