We are having problems with our Solar Turbine. Its a 1040 HP Turbine and we just recently replaced the Accessory Drive. Everything seems to work like its suppose to, but when we get to the part where its suppose to fire off, it just stays running and eventually drops out. We checked the PCD and its only getting to 1 lb. We don't know where to check to see why we're not getting enough fuel.

Needing some knowledge on this subject. Thank you in advance.

 

Hello

kindly check air intake filter D.P and clean filters.

chemical wash for axial compressor and check to be made for pressure transmitter supply.
if GC speed pick up then only CDP will increase.

regards
saradhi

 

After a maintenance outage, or an outage where mechanical work was performed on a gas turbine it's extremely common for manual isolation valves to be found in the wrong position(s). Usually this happens when some well-meaning operator or technician closes the isolation valves to prevent dirt or insects from entering lines, or from water or other liquids from leaking out or leaking into lines/areas where it's not wanted. And, these same well-meaning individuals either forget to log that they closed the isolation valves, or they're not on shift during the re-start, or they just plain forget to put the valves back in their normal running positions.

Also, technicians performing calibrations of transmitters and gages and switches and such can also turn valves and forget to return to their normal position when finished with their work.

Other reasons can be that many mechanical types (fitters; millwrights; laborers) think that valve handles are fun to turn and forget to return them to the position they were found in.

If the axial compressor was spinning there was some compressor discharge pressure. If you have trends from past start-ups you should be able to determine how much pressure should be present at certain speeds. If there are manual bleed valves or manual blow-off valves which should be closed during starting but are open that could be a cause. But, if the axial compressor was spinning it's a pretty safe bet there was some pressure, and flow.

One thing to note about axial compressors is that they don't produce very much pressure until they get near rated speed. If you have a plot of axial compressor discharge pressure during a start to rated speed, it will normally be pretty low until the speed reaches 60-80% of rated and then it starts to climb pretty fast. That's just a normal characteristic of axial compressors that's very different from reciprocating compressors. So, I would be pretty surprised to seem something on the order of 20- or 50- or 100 psig or greater during starting of a gas turbine with an axial compressor. In fact, most gas turbines I have worked on had pressure gages which made it very difficult to read axial compressor discharge pressure at purging/firing speed (it's very difficult to read 3 or 4 psig on a 0-300 psig gage).

I don't have much experience with Solar gas turbines and controls, but I do have a lot of experience with GE-design heavy duty gas turbines--and they're just gas turbines like the Solar gas turbines are just gas turbines. They draw air into the axial compressor, they compress it, they burn fuel in the combustor, and they exhaust hot gases like all gas turbines. I would be surprised if there was a minimum compressor discharge pressure requirement, but if there were AND the axial compressor was spinning at the proper speed for purging/firing then it's a pretty safe bet that the transmitters sensing the axial compressor discharge pressure weren't working correctly or the isolation valve(s) in the sensing line(s) were in the wrong position(s).

To start a gas turbine, all that's required is fuel, spark and air (presuming all the pre-start check permissives are satisfied and the starting means is working correctly). If the unit did not attempt to energize the ignitors (spark plugs) and did not attempt to put fuel into the machine it's also a safe bet that one or more start-check permissives were not met--and that there was one or more Process Alarms to indicate the problem. Including a low axial compressor discharge pressure, if that is a start permissive.

So, the first thing to do is to verify that all manual isolation and/or bleed valves are in their proper positions for all the systems on the turbine. This is <b>ALWAYS</b> the last thing to be done after any maintenance outage, or any time the turbine has been out of service for some time--to check and place all manual valves in the proper running position prior to initiating a START. A former colleague of mine was very, Very, VERY fond of saying, "The three most important things to check before starting a gas turbine are: Valve position; valve position; and valve position. It's that important.

If the accessory gear connects the starting means to the turbine/axial compressor shaft, then it could be that there's something wrong with the coupling and the turbine/axial compressor shaft isn't actually spinning when you were trying to start the turbine (hopefully, that's not the case--hopefully someone observed shaft speed on the control system operator interface, and one would think someone from the Mechanical Department would also have been watching the shaft and listening for rubs and odd noises on the first start attempt).

Another possibility is that the transmitters sending axial compressor discharge pressure feedback to the turbine control system aren't working properly (were calibrated incorrectly; were disconnected--electrically or mechanically--and not reconnected; do not have power; or the input cards of the control system are not working correctly or have failed).

So, there's several things to check.

Please write back to let us know what you find!