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In gas turbine what is the function of bleed valves?

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Question added by Khalid Rwaili , Head of instrument disciplines , Al Furat Petroleum Company(AFPC), Damascus
Date Posted: 2014/08/16
mohamed eliwa
by mohamed eliwa , instrument and control engineer , egyptian maintenance company 'emc'

A bleed valve for bleeding air from a compressor at start-up of a gas turbine engine is self-actuated. The bleed valve moves between open and closed positions based on the pressure within a compressor. 

the bleed valve is driven to an open position at low pressure conditions and to a closed position once the pressure within the compressor chamber becomes higher and closer to operating pressures.

Swe can say it's normal open valve and tend to close when turbine start up .

Damian Okonkwo
by Damian Okonkwo , System set up/ Installations

Bleed Valves (also known as Air Blow off Valves in some other plants) functions to relief the Compressor of excess pressure during start up in order to prevent compressor Surge.

Ahmed Soliman Saeed
by Ahmed Soliman Saeed , Information Technology Instructor (IT Instructor) , Light your Brain

bleed Valves are connected to Compressor as it used to transmitt air from compressors to cool Nozzles and Rotors of turbine

Farhan Baig
by Farhan Baig , LEAD INSTRUMENT ENGINEER , FARABI PETROCHEMICALS

The bleed air valve has special purpose, as the name suggests, it takes a bleed air line from a compressor (hot compressed air) which then can be cooled and utilized as instrument air for a gas turbine. in other words the air processing units APU can be bypassed. There is a special unit named bleed air cooler to cool the bleed air from the compressor.

Hasan Zainy
by Hasan Zainy , Control / Instrumentation Filed Service Engineer , GE

nice answer mohamed eliwa. In other words to prevent surge for the axial compressor. as some time they named antisurg

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