Bleeders prove isolation: shut the block valves, open the bleeder, and if it goes dead, the line is clear to work. They also vent air when filling a line, drain low points, and depressurize instrument tubing through a manifold. On a gauge or transmitter manifold, the bleeder is the small needle valve that vents the instrument side before it is removed.
Crack the bleeder between the blocks, if it keeps spitting, one of those valves is passing and we don't open the flange.
A short spit that dies away is just the trapped volume between the blocks; a stream that never lets up means a block valve is passing.
Also heard as
- bleed valve
- vent valve
- drain valve
- bleed
Related terms
Double block and bleed
Isolation using two closed seats in series with a vent or drain between them to prove the isolation holds.
Needle valve
A small valve with a long tapered stem tip that meters tiny flows with fine adjustment.
Passing
Leaking through the seat while closed, so fluid still gets past a valve that is supposed to be shut.
Bull plug
A solid or tapped round-nosed male plug used to close the end of a swage, fitting or valve outlet.