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Blackout When Gas Turbine Changes From Gas to Oil

08/27/2009 4:21 AM

I have 5 Solar gas turbines which normally running in gas

When gas pressure low/loss, they are changed to oil

Due to change over at same time, oil supply pressure drops very quick and can not meet the turbine required presuure, it results in black out

If I install additional accumulator on the main fuel oil discharge supply , can I solve this problem? or anyone knows other way please help!

Thanks to all

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#1

Re: Black out when gas turbine change from gas to oil

08/27/2009 4:24 AM

It sounds as though the oil supply pipework is either blocked or undersized.

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#2

Re: Black out when gas turbine change from gas to oil

08/27/2009 5:02 AM

Have you reviewed specs. per your particular turbine's manual,or contacted the manufacturer re: related technical bulletins,known fixes, or proper configurations for setups similar to yours?

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#3

Re: Black out when gas turbine change from gas to oil

08/27/2009 5:19 AM

When was the last time the fuel filter was changed?

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#4
In reply to #3

Re: Black out when gas turbine change from gas to oil

08/27/2009 9:40 PM

We are in ofsshore FPSO, From 2003-2008 we have total 11 black out, no succeffull change over even one time

We reviewed spec/sizing it is OK.

Now, go further to solution:

1/Add accumulator

2/Running pump in paralell : normal one in operation

3/Add day tank

We prefer a accumulator but quite not sure it make sense.

Is there any place that using accumulator in this situation? Please help

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#5
In reply to #4

Re: Black out when gas turbine change from gas to oil

08/27/2009 10:38 PM

change the setpoint for changeover on ONE MACHINE to a higher number, so the next time your pressure is falling- the machine may be able to get over to liquid fuel and hold up some power before the others crash out. your issue may only need some minor engineering from the description you have given.

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#10
In reply to #4

Re: Black out when gas turbine change from gas to oil

08/28/2009 6:09 PM

Have you considered having an accumulator for the GAS fuel? If you have one turbine switch fuel at a time (as already suggested), having, say, an hour's worth of gas will permit keeping the rest running even if the line pressure has dropped to zero. Even if it takes several minutes for each unit to make the switchover, you should still have a reserve when all are now running on oil. When gas is available, refill / repressurize the accumulator prior to going back to gas; simple one-way pressure-controlled valves should make this automatic. Changeover will continue to be controlled based upon the gas available in the LINE, not your reserve.

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#6

Re: Blackout When Gas Turbine Changes From Gas to Oil

08/27/2009 11:55 PM

We had a similar issue on a RR m/c. The supplier provided an accumulator to prevent tripping the machines on startup. Besides, a return line recycled back to tank will help to ensure adequate supply pressure.

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#7

Re: Blackout When Gas Turbine Changes From Gas to Oil

08/28/2009 2:34 AM

Accumulator is a sensible alternative, will need to do a little fluid study to evaluate pressure decay/recovery time of real system and then based on turbine oil volume needed during transient size accumulator or multiple units as needed. comment on line size, flow capacity, pump capacity any restrictions all need thorough review. Even with accumulator I would be concerned on adequate pressure of turbine to follow through cycling/ramping conditions without pressure drop then also. concern is if pressure is not maintained you will get carbon fouling, combustion temps out of range, and premature can failures. Really need to get to bottom of issue, suspect overall oil supply or pumping is not adequate. One more concern. If a heavy oil, is it heat traced and is it working properly? Also even if filters are not appearing fouled, be sure to verify housing size and filter flow capacity for actual oil viscosity at the static oil line pressure is adequate. Be sure to allow for at least 20 to 40% additional capacity from filter fouling during use. Also verify filter is not exceeding rated DP during the pressure loss. Might be good hint if it is.

Best of luck getting to the bottom of the problem.

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#8

Re: Blackout When Gas Turbine Changes From Gas to Oil

08/28/2009 8:52 AM

I would have originally suggested an adjacent day tank by the turbines. After reading the wisdom of previous posters, a well sized accumulator does seem to be a better option. The other suggestion to vary to low pressure setpoint to prevent simultaneous turbine change-over is also an excellent suggestion. The extra cost of running one or two units on oil for brief periods has to be less than the cost of recovering from the 10-11 blackouts that you have gone through.

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#9

Re: Blackout When Gas Turbine Changes From Gas to Oil

08/28/2009 10:48 AM

Have your fuel changeover control software looked at by an expert, especially the setpoints. I had a similar problem occur in a power station belonging to an Oilfield in the Sinai desert in the eighties and the results were 'catastrophic' to say the least, with field shutdown, and explosions happening in the combustion chambers of all 5 G.E. turbines due to a software 'glitch' shutting down one type of fuel and changing over to the oil. However during the change over the system delivered both fuels simultaneously as the original problem was just a pressure/flow fluctuation the explosions were loud and 'expensive'........ A post incident review pointed to badly designed control software...... The software engineering house rejigged/rewrote it and as far as I am aware, the problem has not re-occurred at that location.

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