Blowdown valves are usually installed downstream from the
air/oil separator and performs a couple of critical
functions. At start up the valve closes to allow the
separator pressure to build up, and during unloading
and shutdown the valve opens to bleed the pressure into the
atmosphere. The blowdown valve may also be used as a bypass valve
to bleed air through the compressor during start up.
In a compressor
environment, significant pressure and mechanical/thermal
stresses are placed on the blowdown valve. All of
these factors wear down valve components, and as a result the
o-rings and seats naturally become worn over time. At this
point it is advised to either repair or actually replace the
blowdown valve to avoid costly leaks.