from the Automation List department...
Bleed valve function
Engineering and workplace issues. topic
Posted by Anonymous on 11 January, 2007 - 12:54 am
What is the significance of Bleed Valve operation from start up to full loading a Gas Turbine?

Posted by markvguy on 12 January, 2007 - 12:38 am
"Bleed valve" is another one of those poor American English terms for a valve which is meant to siphon off a portion of the flow from another system.

A GE-design heavy-duty gas turbine employs compressor bleed valves to protect the axial compressor during start-up and shutdown against stalling and surging conditions. These valves are typically only open during acceleration to rated speed and deceleration from rated speed. Newer heavy-duty gas turbine with complex combustion system arrangements designed to limit emission of harmful gases also employ the compressor bleed valves during very light loading to limit the amount of air entering the combustor.

Compressor bleed valves discharge into the gas turbine exhaust duct. Compressor bleed valves are generally closed during normal operation (with the previous exception) since "dumping" axial compressor discharge into the exhaust reduces efficiency (but it's MANDATORY during start-up and acceleration to protect the compressor!). Compressor bleed valves are generally either fully open or fully closed; they are not modulated.

GE-design heavy-duty gas turbines also employ inlet bleed heat valves to recirculate a portion of the axial compressor discharge back to the inlet of the axial compressor for a variety of functions. One application uses them to heat the inlet air to prevent icing on the compressor inlet (appropriately called anti-icing protection); another application uses inlet bleed heat to protect the axial compressor when the IGVs (axial compressor Inlet Guide Vanes) are closed below the "normal" operating conditions ("normal" being before complicated combustion systems designed to limit exhaust emissions were invented).

Inlet bleed heat control valves are modulated to control the amount of air recirculated back to the axial compressor inlet. Recirculating axial compressor discharge back to the inlet is also inefficient, but is generally limited to approximately 5% of rated air flow through the compressor--and necessary to protect the compressor at low IGV angles. Inlet bleed heat valves are generally closed before the unit reaches rated load (except for anti-icing protection) and should be closed during rated power output (Base Load) operation (except for anti-icing protection).

If you require more information, your question isn't exactly clear--are you asking about compressor bleed valves or inlet bleed heat valves or?.?.? Or just bleed valves in general?


Posted by neepco_agt on 13 January, 2007 - 5:12 pm
I was asking about compressor bleed valve. In our case, its a 21 MW mark v controlled GE gas turbine.

Posted by J.Das on 17 August, 2007 - 11:02 am
Compressor bleed valve is a preventive measure of compressor soaking and compressor surging. For further details, please search for compressor soaking on

Posted by John Blackburn on 1 November, 2010 - 2:52 pm
With respect to aircraft gas turbines, during take-off & landing up to an altitude where bird ingestion is possible - are the bleed valves open or closed?


Your use of this site is subject to the terms and conditions set forth under Legal Notices and the Privacy Policy. Please read those terms and conditions carefully. Subject to the rights expressly reserved to others under Legal Notices, the content of this site and the compilation thereof is © 1999-2014 Nerds in Control, LLC. All rights reserved.

Users of this site are benefiting from open source technologies, including PHP, MySQL and Apache. Be happy.

"The student in question is performing minimally for his peer group and
is an emerging underachiever."
Advertise here
Servo, steppers, analog, digital & web HMI - Fully Integrated!
Time to incorporate data handling, web HMI and motion in one system!
Servo, stepping motor control, analog & web HMI in one system!
164-page eBook free download - EtherCAT Applications Guide
View free setup and multi-vendor EtherCAT demo videos online
our advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive