I am a DCS programmer recently introduced to the Gas Turbine based Power Generation Industry. As a newbie I have very less knowledge on the precautions and procedures involved in a GT first fire. Have gone through much of the plant operation program and philosophy, but still seem to be lacking knowledge of First fire procedures.

Please do guide me in general.

 

George,

First fire of a gas turbine generally means that you have already <b>proven</b> that the fuel stop valve(s) will be closed by the turbine control system when a trip condition has been detected. By every means possible (some turbine controls have two independent means of electrically closing the fuel stop valves, as well as hydraulic means). So, you first need to be extremely confident that the fuel stop valves will close when a trip condition is detected by the turbine control system.

Now, a lot (too many) people--especially Customers--believe that means every single trip condition has to be simulated and proven, and that's just not true. You need to be assured that each trip condition will actuate/de-actuate the necessary relays to close the fuel stop valve(s), and then prove the fuel stop valves will close when commanded to, and then you are in a good place to be able to actually admit fuel into the turbine with the confidence that, if necessary, the fuel stop valve(s) will close to protect the turbine.

The next thing you need to be assured of is that the fire detection and extinguishing agent discharge system(s) are working and have been tested and can detect a fire and discharge extinguishing agent if necessary. There might be a lube oil leak which results in a fire, or, if it's liquid fuel being used to run the turbine a liquid fuel leak that results in a fire. So, the fire protection system(s) need to be tested and in working condition--and enabled. (I've been to sites that disable the fire protection system(s) during first fire because "...there are enough people around to discharge extinguishing agent if a fire occurs..." Tell that to the insurance company and see if they will pay.

You want to be sure that the unit will go on "cooldown" (the method that ensures the rotor will not develop a sag or bow when hot after a stop or trip).

You should also check to make sure the starting means can "crank" the turbine shaft (spin the shaft without fuel being admitted).

Of course, you will have checked the flame detection system (flame in the combustors), and the ignition system (the spark plugs).

And the very, absolutely most important thing you need to do is: <b>Make sure all the manual handvalves in all the respective systems are in the proper positions.</b> This means all of the filter canister fill and drain valves; the hydraulic accumulator block and bleed valves; the pressure sensing isolation valves are all open (axial compressor discharge pressure; fuel pressure; lube oil pressure; hydraulic oil pressure(s); etc.). EVERY manual handvalve must be checked prior to a start, or, I can pretty much guarantee there will be nuisance alarms and even trips.

The mechanical team thinks this job is the controls team's job, and the controls team believe it's the mechanical team's job--but if you're the guy who's the lead commissioning person on the control, and since most every one of those valves has some effect on the control system (pressure sensing; differential pressure sensing; etc.) it's <b>YOUR</b> job. You can walk all of the system down together with the mechanical lead, but it has to be done. It's really embarassing to find the turbine has tripped once or thrice or more because one or more valves was not in the proper position. And, if there's a pressure switch or a differential pressure or pressure transmitter that is isolated by a manual handvalve and that device is connected to the control system--it's the control system person's job to make sure the valves are in the right position.

After that, you want to be able to monitor fuel flow-rates and flame and exhaust temperatures, and bearing metal temperatures, etc. So you need to configure the trend recorders/displays to be able to do so.

And, you want to make sure the fuel supply piping to the fuel stop valves is purged of air and full of fuel (this is especially important for liquid fuel).

Then, it's all about "pushing the (start) button". You should be confident that the control system will do it's thing to control fuel, that the stop valves will operate properly, and that all of the parameters which need to be sensed are "valved in."

If the turbine control system has a means for limiting fuel after flame is detected (one OEM calls it FIRE Mode), that's a good mode to select when starting. This will put sufficient fuel in to, hopefully, establish flame, and the hold the fuel constant afterwards as the machine warms up.

Some OEMs have very detailed procedures so you should be sure you have and/or are following their procedures. It seems you're working for one of the bigger OEMs, and if it's one of the ones you checked when posting this question they do have some pretty detailed procedures for monitoring temperatures and vibrations and such.

These are the general guidelines. Remember: It takes fuel, air and a "spark" to ignite the flame. If you don't get flame on the first try but you can see from your trend data that there was stable fuel flow for most of the firing period then maybe the fuel flow wasn't sufficient, or the spark wasn't sufficient, or in the case of liquid fuel maybe there wasn't sufficient atomizing air. Or, maybe there was just air in the fuel lines between the stop/control valves which needed to be purged out and a start attempt or two is required to do that.

This is about as much as I'm comfortable sharing in this forum. If you need to know what to do next, you should probably get someone there with you who's done it before and help guide you. There are too many intangibles, and without a LOT more information about the turbine, the fuel(s), the site, etc., it's just too hard to give any more information. Just be confident that the fuel stop valves will close when commanded to, that the fire protection system is operational, AND, again, <b>MOST IMPORTANTLY</b> that the manual hand valves in all the systems are in the right positions--and you've got a safe and good foundation for the rest of the start-up.

Hope this helps--and good luck!

 

Thanks CSA,

Its was a great favor.

Have some idea now on where to start. Might be disturbing you guys a lot (sorry). Am curious to learn and clear my doubts on these systems. you never can be too cautious about these systems..rite..

Thanks again. keep adding on to the topic..might help another newbie someday.

 

Yes CSA,

I am involved with some of the major OEMs. But currently confining myself to minor projects so that I may be prepared for the major ones. I do have technical consultants and engineers from the OEM side for support. I needed to have a little knowledge on what to ask or what to expect when I get Involved with the technical details. So preparation.Your post will give me that edge.

Thanks a lot again. Many more topics that I look forward to get advice from you.

 

CSA Sir,

What are the stages of testing a Gas Turbine, before it is ready?

George Sir,

Does your DCS programming involve controls of the Gas Turbine directly or is it through a control system by the Gas Turbine Manufacturers?

Thanks in advance

 

PLC Programmer,

There's loop-checking; there's usually some kind of crank checks (spinning the turbine-generator shaft with the starting means without admitting fuel or energizing the ignitors); there's cooldown (turning gear; ratchet) testing; there's LVDT or position indicator calibration (usually requiring hydraulic pressure); there's fire protection system/extinguishing agent discharge; there's first fire; some manufacturers require prolonged operation at part speed for "run-in"; there's full speed-no load operation (for synchronization checks and generator AVR tests) and heat soaking and vibration testing; some sites/manufacturers require short-circuit tests of the generator at rated speed (full speed-no load); there's initial synchronization (manual and auto); there's loaded operation checks; there may be tuning for emissions reduction. And there may be some kind of reliability test required by the purchaser before the turbine-generator is ready for dispatched operation.

Those are the <i>basic</i> checks. Again, some manufacturers and commissioning personnel may have others. If there are multiple fuels, then there will be starts and operation on each fuel, and possibly some tuning required for fuel transfers (always a LOT of fun). Some sites also require load rejection testing, sometimes called "load throw-off" testing (an antiquated practice not really necessary for gas turbines, but very important for steam turbines), and some sites even want to perform "load throw-on" tests (though when asked how this would be performed--or why it should be performed, there's generally no logical answer).

I usually test the exhaust overtemperature protection by simulating exhaust temperature inputs, and sometimes the exhaust temperature control function (by simulating CPD), and sometimes, if the Customer demands it, the flame detection (though that can be difficult with some of the newer designs and recent safety restrictions).

Some Customers will demand other tests. Some will even require the turbine be tripped from running by simulating every possible trip condition--which is difficult, not to mention time-consuming (and was never planned for in the schedule), as well as stressful on the turbine hot gas path components.

And, there are the Performance Tests, which most Customers will also demand (as well as the banks/finance companies).

But, those are the <i>basic</i> tests which should be performed and documented before the unit can be scheduled for power production.