API PLAN 32
In Piping Plan 32, flush is injected into the seal
chamber from an external source.
Piping Plan 32 is used in services containing solids
or contaminants, in which a suitable cleaner or
cooler external flush will improve the seal
environment. It is also used to reduce flashing or
air intrusion (in vacuum services) across the seal
faces by providing a flush that has a lower vapor
pressure or that will raise the seal chamber
pressure to an acceptable level.
This plan is almost always used in conjunction with
a close-clearance throat bushing. The bushing can
function as a throttling device to maintain an
elevated pressure in the stuffing box or as a
barrier to isolate the pumped product from the seal
Plan 32 Reduces air intrusions across seal faces by
providing a positive flush.