I am very new to GE Frame 9E gas turbine with Mark V TMR control system. In mark V operating station, the over speed test page is provided. The provisions are, we I am very new to GE Frame 9E gas turbine with Mark V TMR control system.

In mark V operating station, the over speed test page is provided. The provisions are, we can do electrical over speed test and also mechanical over speed test (with different push buttons). The machine having a mechanical over speed trip bolt also.

The values for TNKHOS =110 % and TNKHOST= 113.5%

Does it mean, if the machine is in normal operation and because of any abnormality if the speed rose to up to 110 % the unit will trip?

And if the electrical over speed test button selected ON, in which speed machine will trip? At 110 % or at 113.5 %?

Does the electrical over speed test button over riding 110% trip set point to 113.5? If it is 113.5%, how we can test the 110% trip physically?

Does the mechanical over speed test button selection making the machine trip from the mechanical over speed bolt?

Kindly advice.

 

The electronic over-speed setting is 110%. That means the turbine will trip if the speed gets to 110%.

When testing the mechanical bolt, the 110% electronic trip is inhibited, but you will trip the turbine when the speed reaches the setting for the bolt. I think the setting for the mechanical bolt is 112%, and the 113.5% TNKHOST setting is for an electronic trip if the bolt does not trip while you are testing.

I don't remember if you trip at 110% when testing the electronic trip - it may just alarm. Read the control specification provided by GE.

 

When you are testing an over-speed trip (electrical or mechanical), the "maximum search speed" is set to 113.5%. This is to allow the turbine speed to be increased above the trip set points (see below). Although I've never tried it, I believe that if, during an over-speed test, the turbine speed were allowed to reach 113.5% the unit would be tripped. But, again, that's conjecture. The description of the Control Constant is 'Maximum Search Speed', so it might be that the Speedtronic will not allow the turbine speed to exceed 113.5% if none of the over-speed trips actuated to trip the turbine. But, the descriptions of a lot of Speedtronic signal names (and Control Constants) are pretty poor.

The mechanical over-speed bolt is usually to be set to 112.5% +/-50 RPM, which should be less than 113.5% of rated speed. But, because the mechanical over-speed is a mechanical device and is a spring, it's subject to lots of external factors, including temperature, which can cause it to not actuate when it should, or before it should, or after it should.

There are actually two electrical over-speeds in the Mark V, even if there is a mechanical over-speed bolt. It has been customary to set both electrical over-speed set points to 110%, but that was not a hard and fast rule.

One of the electrical over-speeds, the "Primary" electrical overspeed, is detected in <Q> sequencing, which is usually executed at the rate of 8 times/second (8 Hz).

The second electrical over-speed, the "Emergency" electrical overspeed, is detected in <P>, and if I remember correctly the code in <P> runs at 128 Hz. So, usually the first electrical over-speed to be detected is the emergency electrical over-speed.

When the mechanical over-speed test is selected, the electrical over-speed trips are supposed to be increased to 113.5% to allow the mechanical over-speed bolt to operate at approximately 112.5% +/- 50 RPM.

I think that answers all the questions. Hope this helps.

 

Hi,
there is a procedure for the E.O.S and M.O.S you have to set some constants in te MK V for the test.

I can send you the procedure if I know your email address.

 

Thanks for the reply. Now things are almost clear.

My email id is santhoshpc78 [at] @gmail.com

Please send me the EOS and MOS test procedure.
Thanks in advance.

 

I want to caution anyone about this procedure!!!

The CSP should be automatically changing the Control Constants for these tests. However, there were some early Mark V's that were shipped with CSPs which didn't do the switching properly, so a workaround was necessary if the sequencing wasn't properly modified (and sometimes it wasn't).

But, <b>this procedure should NOT be necessary for MOST GE-design heavy duty gas turbines with Mark Vs!!!!</b>

 

Thanks CSA.
Thanks to BB for sending the procedure.

 

appreciate if BB could send me those procedures as well. my email is sdmarley [at] gmail [dot] com
Thanks

 

Actually for turbine safety two over speed trips are provided, Electrical and Mechanical over speed. Value of electrical over speed is always lower than Mechanical Over speed. The over speed value is decided at the time of design of turbine. So if for a turbine Electrical over speed is 114% than Mechanical over speed will be higher than 114% might be 115% as in our turbine. If due to some reason electrical governor fails to trip the turbine at 114% then mechanical over speed will come in action at 115% and turbine will trip.

if anyone still have any questions then ask me at deepak_yadav0002 [at] yahoo.co.in