Is Your Gas Turbine Underfiring?
I can count three recent experiences where we get a phone call that goes something like this:
“We just did an outage and now we make less power than before, what’s going on?”
A couple of things can cause this to happen. Most gas turbines are controlled to a constant firing temperature, but the firing temperature isn’t measured. In reality, a combination of compressor and exhaust measurements are used to estimate the firing temperature. That estimate is typically what is shown on your control screen or saved to the historian. The other important thing is that estimate is only good for a certain machine with hardware of an existing quality. If refurbished hardware isn’t up to standards, instrumentation was re-calibrated or replaced, or even in some cases if improved hardware is installed the assumptions for that estimate aren’t 100% valid any more.
Thus, while your control screen may say that your firing temperature is the same as before the outage, that might not be the case.
Analysis tools and techniques can be used to identify areas to investigate to determine if the problem is control or hardware related. Then a course of action can be suggested to restore performance to expected or required levels.
