During start up of the GE Gas turbine (Diesel engine driven), the Diesel engine fail to accelerate. The 20 DA1 and 20DA2 to not getting actuated. It was noticed that the 14HR (Shaft speed is going more that 15 RPM) is deactivating the diesel warm-up timer done. We checked the torque converter and the hydraulic pressure. The Hydraulic pressure was 4 psi. Can anyone advice why the shaft is moving before the diesel engine warm up timer done?

 

> Can anyone advice why the shaft is moving before
> the diesel engine warm up timer done?

Was the shaft <b>actually</b> moving while the starting diesel engine was warming up?

What kind of clutch (jaw or SSS) is used between the torque converter and the Access. Gear Box/turbine shaft?

What kind of control system is in use on the turbine?

 

>> Can anyone advice why the shaft is moving before
>> the diesel engine warm up timer done?

> Was the shaft <b>actually</b> moving while the starting diesel engine was warming up?
Yes

> What kind of clutch (jaw or SSS) is used between the torque converter and the Access. Gear Box/turbine shaft?
Jaw clutch

> What kind of control system is in use on the turbine?

Sorry for the delay in reply.
It is noticed that the shaft start moving at 689 RPM of Diesel engine. As per the logic the 2 Minute warm up timer starts at 450 RPM and it takes two minute to complete. Before the timer bit done the due the shaft movement the 14HR get deactivate. To activate the acceleration solenoid L20DA2X the 14 HR and two minute warm up timer should done. Here before the timer done bit the 14 HR gets deactivate due the shift movement.

It is jaw clutch, the control system used is Sentinal control system

 

Ismayil,

The single most important question (I forgot) to ask when a problem like this starts on a piece of equipment that had been running without problems is:

When did this problem start, and what changed between the time the equipment was working correctly and now?

Let's say this problem started after a maintenance outage, and during this outage the torque converter was refurbished, and the diesel starting motor was overhauled. Now, the torque converter transmits more torque than previously (it was old and tired and needed refurbishment), and the diesel starting motor's warm-up speed was not adjusted correctly (it's higher than it should be).

The combination of these two conditions could result in more torque being transmitted to the turbine shaft than before.

Typically, when a turbine START is initiated the hydraulic ratchet is energized to close the jaw clutch (even if it's already closed) before the the starting means is started (this to prevent the starting means side of the jaw clutch from turning as the jaw clutch is closed--which would damage the jaw clutch teeth over time). Then after the starting diesel warm-up time is complete the hydraulic ratchet is again actuated because the starting means, by itself, is not capable of breaking the turbine-generator shaft away from zero speed without an assist from the hydraulic ratchet. When the diesel engine warm-up is complete and the diesel is accelerated, the hydraulic ratchet is energized continuously to help break the shaft away from zero speed and as soon as 14HR drops out the hydraulic ratchet is de-energized.

So, if the turbine control system is energizing the ratchet during the diesel starting motor warm-up time this could be a contributing factor to the issue you are describing.

Or, let's say, the diesel starting means warm-up speed has been drifting up over time to a value much higher than it should be. Most of the GE-design heavy duty gas turbines with diesel starting motors I have had the pleasure to work on warmed-up at about 500 RPM; some were a little higher at 600 RPM or so, some a little lower at 400-450 RPM or so. What is the design warm-up speed for your turbine (from the Device Summary and/or the Control Specification)? What was the diesel starting motor warm-up speed before this problem started?

It would be great if you would provide the answers to the questions above, as well as the resolution to your problem. Let's recap the questions here:

1) When did this problem start, and what changed between when the problem started and now?

2) What should the diesel engine warm-up speed be for the diesel starting motor at your site? What was it before the problem started, and what was it six weeks ago, six months ago, one year ago? (In other words, has the diesel engine warm-up speed changed, recently, or over time?)

3) Is the hydraulic ratchet being actuated during the diesel engine warm-up? If so, why?

A lot of people read these threads (now and over time, using the 'Search' feature of control.com) and it would be very helpful if we understood how this problem started, and what was done to resolve it. Feedback is the thing that separates control.com from many other World Wide Web forums; people respond to let others know if the information was useful--or not, as the case may be--and MANY other people who read these threads get to know what works and what doesn't, and how problems are troubleshot and resolved.

Looking forward to hearing back from you about the conditions of the problem (when it started; what changed before the problem started) and how the problem is resolved!

 

No maintenance works were carried out on the torque converter and Diesel engine. The turbine was shutdown for some actives in the excitation system.

 

Ismayil,

You notably did not respond to the questions about why the diesel starting motor warm-up speed was more than 450 RPM, and what the diesel starting engine warm-up speed has been in the past (has it been trending upwards over time), <b>AND</b> whether the hydraulic ratchet was inadvertently energized while the diesel starting motor was warming-up.

 

CSA,

Sorry for the delay in replaying. The warm-up timer starts at 450 RPM. Ideal speed of the diesel engine is 750 RPM.

Hydraulic Ratchet is actuated once the START command is initiated and the ratchet becomes more frequent.

Physically it is observed that Ratcheting Pump keeps on working in each ratcheting stroke (Fast Ratcheting) till Turbine Shaft starts to rotate then it stops (14 Hr). It has been also observed this time that during 115 Seconds) the Ratcheting took place 7 times before Turbine Shaft rotates.

snapshot data shown as below <pre>
Date Time Diesel engine speed Shaft speed Timer accumulated
1/23/2014 16:32:43;318 944 0 250
1/23/2014 16:32:44;078 710 0 1000
1/23/2014 16:32:45;058 760 0 1751
1/23/2014 16:34:32;118 683 6 109000
1/23/2014 16:34:34;958 683 15 111752
1/23/2014 16:34:35;178 681 15 112001
1/23/2014 16:34:35;748 682 17 112501
1/23/2014 16:34:57;748 681 81 120000</pre>

Ismayil

 

Ismayil,

In my personal opinion <b>based on the information provided</b> the diesel starting engine warm-up speed is higher than it should be <b>and</b> the hydraulic ratchet should not be actuated until the end of the diesel warm-up time (which is when the diesel starting engine should be accelerating and the hydraulic ratchet should be providing the assist to help the diesel starting engine to break the shaft away from zero speed).

I do not (at this time) have access to any GE Speedtronic elementaries to check if the hydraulic ratchet is continuously energized during a diesel starting engine warm-up period. But even if GE Speedtronic controls do energize the ratchet continuously during the diesel starting engine warm-up time I do know the turbine-generator shaft did not break away from zero speed until the diesel was accelerated after the warm-up time was complete.

 

CSA,

We noticed and as per the PLC logic the ratchet will continue during the war up period. It stops the shaft speed is greater than 15 rpm. Here we are puzzled with the diesel engine speed is almost constant and the ratchet is stopped from where the shaft getting energy to rotate up to 81 rpm.

Regards
Ismayil