how can sliding FSR logic operate on GTCs or GTGs when we change the composition of feed gas in case of lean or rich gas? normally it should works during the start-up and operation as well, but isn't like this for our case. this logic work only during the start-up, and as we saw when the gas composition had change (with lean gas) the behavour of gas turbine become slower. and it kept stable at 85% of HP shaft speed (and the SP is 100%).

the question is the FSR logic should probably gives more opening to the gas valve?

waiting for comments and help
thanks

 

blur,

GE is trying many new logic and control sequences to try to accommodate various fuels and operating conditions. It's very likely that the control logic and algorithm in use at your site is specific to the application. This is not common for most GE-design heavy duty gas turbines, though GE is developing new schemes to try to sell more turbines for more varied conditions and fuels.

Having said the above, Sliding FSR (or P2) cannot be expected to account for all gas compositions. It's probably documented in the Control Specification what the limits of the control algorithm and setpoints are as far as the upper and lower gas compositions. It's not reasonable to expect the control to be able to operate on any and all gas compositions.

I have also been to sites which operate on varying fuel compositions in which there are entrained solids and liquids which must be removed prior to admission to the turbine, and the knock-out drum (one term for a cyclonic separator) and filters were found to be seriously plugged and restricting fuel flow. At one site the filters had ruptured and the contaminants had solidified in the fuel nozzle orifices. There was a high dp alarm prior to the rupture, but when the filters ruptured the dp went low again and the operators--and their supervisors--just thought the high dp had been an erroneous indication. They didn't look at the local gauge, and there was no dp transmitter sending a pressure signal to the HMI.

What does the packager say about the problem?

What were the Stop-Ratio Valve and Gas Control Valve positions during the start-up that failed to achieve rated speed? What were they compared to previous start-ups on similar fuel? (It's presumed the site has some kind of gas chromatograph to provide gas composition to the Speedtronic panel, and that you have some data-gathering capability--even if it's just DDRs (Dynamic Data Recorders) or Live Trend data--to compare information.

What was the gas fuel supply pressure upstream of the SRV?

Again, this control and algorithm cannot be expected to allow operation on any and all fuel composition. To do so, the fuel nozzles would have to have variable orifices, and that's not possible. So, before we can tell you what might be wrong you need to tell us:

1) What are the stated limits of operation of the Speedtronic (with respect to gas composition),

and,

2) What was the gas composition during the failed start attempt,

and,

3) How does gas fuel supply pressure and gas valve position (SRV and GCV) compare to previous start attempts on similar fuel?

Do you know if the gas chromatograph is working properly? They don't have a great track record; most of the ones I've seen are usually inexpensive models which aren't very reliable. Quality comes at a cost, and so does lack of quality.

You have not provided sufficient information for us to be of any further assistance. It is recommended you get someone from the packager to site to review the data and make appropriate recommendations based on information available on site.

Please write back to let us know how you fare in resolving the issue.