Intermediate Blow Off valve on Axial Flow Compressor
Intermediate Blow Off valve on Axial Flow Compressor
(OP)
We have recently experienced severe damage on an axial air compressor. The damage was caused due to multiple interstage surges. The direct cause of this was intermitent opening of the intermediate blow off valve. The valve is situated after the first intercooler, before the air is fed into the second compression stage. Can anybody shed some light on the purpose for such a valve at this location. Our investigations have shown that almost everytime this valve opens, there will be localised surges on the second compressoin stage.
Please help.
Please help.





RE: Intermediate Blow Off valve on Axial Flow Compressor
Has this been happening since the compressor was new ? since a recent overhaul ? what is driving the compressor, a gas turbine ? Is the valve opening with subsequent surge occurring during run-up or at normal operating speed ?
RE: Intermediate Blow Off valve on Axial Flow Compressor
RE: Intermediate Blow Off valve on Axial Flow Compressor
This valve actually vents the air from the first compression stage to atmosphere! During normal operation, this suffocates the second compression stage and hence causes surges on the second stage.
This modification was done a few years ago but nobody here seems to understand the reason for this particular valve. We have 2 other blow off valves on the compressor dischargs (after the third compression stage)that perform the normal function of anti surge valves.
Can you provide information/insight about the need for the intermediate blow off valve?
RE: Intermediate Blow Off valve on Axial Flow Compressor
Having a valve there is okay, but it has to have quite sophisticated controls and interlocks. How complex? Depends on the machine.
Purpose? Only the manufacturer has the engineering files. Possibly an attempt to avoid surge during a start up case.
It should have been locked closed.
Was the valve included in the HAZOP?
RE: Intermediate Blow Off valve on Axial Flow Compressor
RE: Intermediate Blow Off valve on Axial Flow Compressor