Change Over From Supplementary Firing to Fresh Air Firing (Vice Versa)

The best people to talk to are those that supplied the equipment. How about a telephone call in the first instance to their technical help-line, perhaps?

dear sir,

your oppinion is correct.

That is what i have done already,but the problem is that they not have any experience in change over from FAF to SF. they told me that without stopping the process it is not possible,and reduction/interruption in steam production is restriction for me.

that is the reason i have raise this question in global spec..

So, why try to change something that works, if the change is not possible? The reason for this thread is abstruse.

I agree with Mr. Slack; the turbine manufacturer indicates uninterrupted FAF/SF changeover is not possible, so that is it.

Has the incorrect turbine been selected?

Do you have a inlet/bypass damper before the burner, if so you can start the GT and modulate the damper open while modulating the fresh air supply damper/speed controller to closed. If no damper then you can override the GT overpressure trip during changeover, you may have to do this your self as some GT suppliers don't like you messing with their control system. Depends how often you changeover, should be seldom as GT should be on line continuous for best efficiency.

Are you certain the FAF to SF and SF to FAF transfer point is occurring at the correct RPM and/or load point?

(If you have damper control.)Are you certain the rate-of-change (speed of opening/closing) ratio between the FAF and SF damper operation is corrrect?

If the damper function (open/closing) is not correctly matched, it will cause the amount/pressure of air present at the inlet to exceed or fail to meet the GT combustion air pressure design and will cause tripping.

This protects the GT from being overcooled causing warping of the turbine components and resulting in vane/bucket damage and/or causing the fuel-to-air ratio to go lean resulting in a "flameout" and unexpected sudden trip which can cause significant GT bearing and vane/bucket damage.