GE GAS TURBINE 9FA CHANGEOVER GAS FUEL

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foxnet115

we have GE 9FA gas turbines,
and the customer asks us to make the CHANGEOVER GAS TO FUEL at base load my questions are:

1/what prevents us to do the changeover at base load?

2/what should we give them as an arguments for not getting tested every week as recommended by GE?

Thanks.
 
I'm confused by this question; greatly.

In general, there is nothing that prevents transferring fuels while operating at Base Load. It's just not a great idea, especially on such a large machine as a 9FA. Remember that when operating at Base Load (approximately 250 MW) that the exhaust overtemperature trip is only 40 deg F above the current exhaust temperature. So, if there is any appreciable "bobble" in fuel flows it's very possible to trip the unit on exhaust overtemperature. And losing approximately 250 MW at one time in most parts of the world is kind of a big deal.

As for the second question, GE's recommendations are minimums and if people want their dual-fuel turbines to transfer fuels as smoothly as possible then they should follow the recommendations as closely as possible.
 
I also operate a dual fueled 9FA.

We transfer once every 8 weeks but do so at min gen (160MW) with the prefill time extended out to around 5 minutes. To date we have not had a fuel coking problem however we did have a recent fuel gas supply failure at base load and the unit tripped on exhaust spread. Looked like one or 2 cans failed to ignite. I have known our unit to successfully do an emergency transfer at base load maybe 2 times giving it a 50:50 success rate.

We also have to reduce load to about 30MW to transfer back onto gas. This is to get the gas temperature back up to operating temperature.

Doesn't really answer your question but this is my experience.
 
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