Plan 74 in Sealban

API Plan 74 Barrier Gas

API Plan 74 supplies a pressurized barrier gas from an external source between the inboard and outboard seals. For reliable operation, dual pressurized 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. A pressure regulator on the panel regulates the nitrogen to at least 25 psi (1.7 bar) above the seal chamber. Used in applications where process leakage cannot be tolerated, the system is designed to allow a small amount of nitrogen to leak into the process fluid. Any leakage past the outboard seal will be pure nitrogen. An optional flow transmitter located on the gas supply panel monitors excessive leakage in the event of a seal failure.