How long should wait before we make gas turbine start once again?

Dear sir,

First, if the gas turbine was running but it stopped, after how much time can we run it again?

Second, or if we run it and the start fails to continue (ignition happens but the turbine fails to reach idle speed), for how long should wait before we make it start once again?

Note: The operator often likes to make it start as soon as possible.

Please, if you have reference for your answer, it will be better.

Thank you and I’m waiting for your reply.
 
Hi

It will depend on many parameters /conditions that you have to monitor according to OEM opeartion & maintenance ..procedures..



Can you tell us OEM/frame of this unit

I got some elements on Frame 9E from GE energy..


For this unit after an emergency/normal shutdown ...unit it can varying ..

Example :

Emergency shutdown
Within 20 minutes maximum following turbine shutdown, the GT may be started without cooldown rotation..you can use normal startup procedure..


If this unit is a fGE Frame9e so we can exchnge here some datas..



Cheers
James
 
Hi

It will depend on many parameters /conditions that you have to monitor according to OEM opeartion & maintenance ..procedures..



Can you tell us OEM/frame of this unit

I got some elements on Frame 9E from GE energy..


For this unit after an emergency/normal shutdown ...unit it can varying ..

Example :

Emergency shutdown
Within 20 minutes maximum following turbine shutdown, the GT may be started without cooldown rotation..you can use normal startup procedure..


If this unit is a fGE Frame9e so we can exchnge here some datas..



Cheers
James
Dear sir,

The type of the unit (Gas Turbine) is ROLLS-ROYCE AVON MK 1533 and the Driven Pump is AVON EAS1

Best regards.
 
KunalKumar,

This topic has been covered before on Control.com. There is a ‘Search’ box at the top of every Control.com webpage. As many people call the same “feature” by something a little different, searching may not always immediately turn up relevant results. But, don’t give up. The information is there; you just may have to work a little harder to get it.

The answer to your question is not easy or straight-forward—without more information. What kind of starting means does the GE-design Frame 5 heavy duty gas turbine have?

Specifically, are you asking how soon it can be started after it is shutdown (a normal, fired STOP), or after a trip (emergency shutdown from load)?

Or are you asking how long can the unit sit between STARTs without being ON COOLDOWN (hydraulic ratchet, or turning/barring gear)?

If you are having problems, what kinds of problems are you experiencing?

Give us more, better information, and we can give more concise, better responses.

We look forward to hearing from you with the answers to above questions!
 
Cummins make diesel engine KT1150 is being used as starting means and we have the GE-design Frame 5 heavy duty gas turbine have.But i want to understand the cool-down cycle and pre start ratcheting time based on duration of shutdown of turbine.we use hydraulic ratcheting for cool-down/warmup.
 
Pre-start ratcheting time. Is a function of how long the unit has been at zero speed. If the unit was shut down normally and was on Cooldown (ratchet) at least until the highest wheelspace temperature was less than approximately 100 deg C before being taken off Cooldown, and the time at zero speed is less than approximately seven days (a week or so), one can probably safely start the unit without ratcheting as long as the lube oil temperature is at least approximately 25-30 deg C. The vibration during starting may be a little higher than normal, but if the unit must be started without any ratcheting it most likely could be.

It’s a common misconception that most GE-design heavy duty gas turbines must be on ratchet or turning gear for several hours before any start regardless of how the machine was shutdown or how long since it was last operated. Of course, that is a good practice, but it’s not always necessary for every GE-design heavy duty gas turbine. It’s a good recommendation , but it’s not absolutely required. (Some F-class machines should and even must be on turning gear prior to starting, but not Frame 5’s—they are well-built, robust machines that are regularly abused and live long and productive lives.

However, if a Frame 5 were unable to be kept on Cooldown (ratchet) after being shut down or tripped for the necessary period (which is really and truly a function of internal metal temperatures and not simply a matter of a set period of time) then the unit should NOT be put on Cooldown (ratchet) until the internal machine temperatures have sufficiently cooled such that the rotor (specifically the axial compressor rotor) has begun to return to nearly straight. Lube oil flow should be maintained at all times if Cooldown (ratchet) operation cannot be maintained while internal machine temperatures are high (wheelspace temperatures higher than approximately 100 deg C) so bearing metal doesn’t soften and get damaged from the heat of the internal machine temperatures).

Once internal machine temperatures have sufficiently cooled and/or Cooldown (ratchet) operation is possible, then and only then should the unit be put on Cooldown (ratchet) for several hours to help the rotor return to a nearly straight condition. After several hours of Cooldown (ratchet) operation then the unit can be CRANKed for 20 minutes or so, and the FIREd for 20-30 minutes or w. This also helps the rotor return to straight condition. If the starting means can handle the continued operation the unit could be put directly into AUTO mode and accelerated to rated speed. Again the vibration may be higher than normal but it probably won’t be high enough to trip the machine. At this point, the rotor is nearly straight again (heat from loaded operation will continue to help it return to fully straight).

So, you should see that there are multiple conditions that must be considered when deciding to re-start a machine. It’s not one answer fits all conditions. A thorough understanding of the machine and how it’s been shut down and for how long is the real way to achieve optimum reliability and availability. Sure, it would be GREAT if prior to EVERY START regardless of how long and how the machine was shut down it could be put on ratchet for two-, three- or four hours, but sometimes it just has to be STARTed and that’s when knowledge and experience can prevent damage or lost generation revenue.

Again, GE-design Frame 5’s are workhorses—but they are also high-speed rotating machines. They can—and do—take a lot of abuse, abuse they shouldn’t have to endure. But there is no one-size-fits-all answer to your query.

Full stop. Period.

Hope this helps. Need more information or clarification—state your question or need more clearly. This is a technical forum. GE-design heavy duty gas turbines are marvels of engineering, simple but not simplistic.
 
Ratcheting for warmup?

Ratcheting prior to a start only serves to raise lube oil temperature—not machine temperature. Ratcheting (Cooldown) prior to STARTing is used to help remove any bowing or sagging of the axial compressor rotor which may have occurred since the unit was last on Cooldown (ratchet). The axial compressor rotor is VERY HEAVY and will—if not turned for a week or more—actually begin to sag (bend) just due to its weight and the distance between the rotor bearings.

Using Cooldown (ratchet) prior to STARTING simply serves to help reduce any sagging which may have occurred since the unit was last on Cooldown (ratchet).

Nothing more. Nothing less.

Warmup? Of the lube oil, maybe. But not of the turbine or axial compressor rotor.
 
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