1971 G.E. Frame 5 with Mark V controls Over-Speed Procedure needs reviewed.

M

Thread Starter

Mark Pirkle

Hello Everyone

I have been asked by one of our trainers for some help writing an Over-Speed procedure for the G.E. Frame 5 turbines at one of the company’s sites. The units are 1970’s vintage originally installed as duel-fuel machines with SpeedTronics controls. The units were operated until the mid 1980’s till they had become so dilapidated due to a general lack of being maintained and repaired that they wouldn’t operate any longer.

In 1999 the units were returned to service after going through major over-hauls on the turbines additionally the field on one of the machines was refurbished. There are four units at the site. The units were converted to Gas only and the controls were up-dated to Mark V controls during the return to service.

I have been the repairman/operator at the site during the summertime since the units were returned to service. The only time the over-speed test has been done is just after the return to service in 1999. I have to go off of some old memories while writing the procedure.

I would like to find someone here to review what I have written. I can post the text of the procedure here. There are some X-Cell screen shots that have to be inserted into the procedure, I would post them as well but I do not know how. If anyone would like to review the entire procedure for me I ([email protected]) will email the entire procedure to them.

The procedure consists of one page that is an over-view of the over-speed protection and one page of step by step instructions and one page of additional warnings and instruction. It is not a real long-winded procedure.

Thanks
Mark Allen
 
This is kind of interesting. A Speedtronic Mark V has two (2) electrical overspeeds (usually set at the same value, 110% of rated), and a GE-design heavy duty gas turbine of the vintage you are describing usually has a mechanical overspeed bolt, which has a setting of approximately 112.5% of rated speed (+/-50 RPM).

Are you trying to test one of the electrical overspeeds (the Primary- or the Emergency Electrical Overspeed), or both of them, or the mechanical overspeed bolt, or all three?

Testing the overspeed bolt is pretty difficult as it requires changing I/O Configuration settings and "Berg" jumpers on the TCEA cards (all three of them).

Some Mark V operator interfaces (we don't know if the machine at your site has <I> operator interfaces or GE Mark V HMIs (running MS-Windows and CIMPLICITY)) usually has a display for Overspeed Testing. It usually has buttons for the various overspeeds, but, again, testing the mechanical overspeed bolt requires changing jumper settings and I/O configuration settings, and then changing them back when the test is complete.

If you can post the procedure to an web host/sharing website (like tinypic.com or a similar site), you will probably get some feedback. You can't post anything other than text-based information to control.com.
 
M
CSA thanks for replying. I was hoping you would offer your expertise. I have been reading your reply for a long time now.

The company isn’t wanting to do the over-speed test (There is a problem with the age of the generator field retaining rings and insurance issues). They just want to know how to do the test. I am very near retirement age and they want to capture some of what is in my head.

I will post what I have written for the test.

Thanks
Mark Allen
 
M
Brief Overview:

Two over-speed protection systems are used, a mechanical and an electronic.

On the electronic type, the speed of the turbine shaft is sensed by four magnetic pickups of which two are fed into the detector which in turn outputs a trip signal below 10% speed and above 110% speed (5612rpm). The Electronic over-speed protection electrically trips the Hydraulic Control Oil Pilot valve. An electronic latching circuit prevents start up after an over-speed trip and at the same time alarms and identifies the channel sensing the over-speed.

The 10% trip signal is by-passed during start up, but is still used to show that the system is operational and functional. If the 10% trip signal was not by-passed during start-up the unit would be prevented from starting

The device symbol for the electronic over-speed is 12HT and the mechanical is 12T. These devices are in the master 4 relay circuit and once tripped de-energizes the 4 relay circuit tripping the turbine.

The two remaining magnetic pickups are used to monitor the unit speed and generate a normal high speed stop signal. The Normal High Speed Stop is accomplished by de-energizing the coil in valve 20 FG in the Control Oil Circuit at 107% (5459 rpm).

The 107% speed (5459 rpm) value is raised to 113.5% speed (5788rpm) during an Electrical or Mechanical Over-Speed Test.

The Mechanical Over-Speed protection consists of an Over-Speed bolt and the Pilot valve for the Hydraulic Control Oil circuit, both of these are located in the Accessory- Gear housing. The over-speed bolt is the mechanical type that trips the turbine at 112% speed (5712 rpm) by mechanically tripping the Hydraulic Control Oil Pilot valve there by dumping the hydraulic system.

The Pilot valve has provisions for manually tripping the Pilot valve should the Over-Speed Bolt fail to operate and a means of resetting the Pilot valve after a Mechanical Over-Speed Trip.

The Pilot Valve can ONLY be reset after a Mechanical Over-Speed Trip by manually operating the reset control located on the Accessory- Gear housing.

(Insert picture file Picture1.png)

The Over-Speed protective scheme provides 3 levels of protection:
Normal High Speed Stop
Electrical Over-Speed Trip
Mechanical Over-Speed Trip
 
M
CAUTION: THIS TEST SHOULD ONLY BE CONDUCTED UNDER THE CLOSE SUPERVISION OF EXPERIENCED COMBUSTION TURBINE PERSONAL!!!
THIS TEST IF CONDUCTED IMPROPERLY CAN RESULT IN CATASTROPHIC EQUIPMENT FAILURE AND GRAVE OR FATAL INJURIES TO PERSONAL!!!

(This procedure is written for the Mabelvale site)

Over-Speed Test Procedure: Unit Status Off-Line and at Rated Speed 5100 rpm for 30 minutes prior to testing.
Over-Speed test should be repeated a minimum of 3 time to assure consistency in the test results.

Select the desired unit from the Overview screen (This is for multi-unit installations).
(Insert screen shot 1)

Select the Control screen.
(Insert screen shot 2)

Select Unit Sync screen.
(Insert screen shot 3)

Select "Sync Off".
Click "OK" on the dialogue box that pops up.
Select "Previous Display".

Select "Auxiliaries" screen. (This is not to be confused with the Aux screen.)
(Insert screen shot 4)
Select "ON" on the Cool Down option.
Click "OK" on the dialogue box that pops up.

Select the "Start-up" screen.
(Insert screen shot 2)

Select "Auto" from the "Mode Select" menu.
Click "OK" on the dialogue box that pops up.

Select "Start" from the "Master Control".
Click "OK" on the dialogue box that pops up.

Once the unit has completed a normal start-up and attains synchronous speed the unit should be operated for at least 30 minutes prior to the testing to assure the unit is at normal operating temperature.
Normal synchronous speed for the Mabelvale units is 5110 rpm.
Normal On-Line speed for the Mabelvale units is 5100 rpm.
 
M
Select "Tests" screen.
(Insert sheet screen shot 6)

Select either the "Start Mechanical Over-speed Trip Test" or the "Start Electrical Over-Speed Test" to start the test.
Click "OK" on the dialogue box that pops up.
Click on the "Raise" or "Lower" button on the "Speed/Control" menu to slowly adjust the unit speed as needed to attain normal "Trip" speed.

The normal Trip speed for the "Mechanical Over-Speed Trip Test" is 5712 rpm 112% speed.
The normal Trip speed for the "Electrical Over-Speed Trip Test" is 5612 rpm 110% speed.

The turbine speed of 5790 rpm should NOT be exceeded while in the "Mechanical Over-Speed" mode or in the "Electrical Over-Speed" mode.

If a successful Electrical Over-Speed trip test is attained a "Master Reset" must be done before the unit can be re-started.

If a successful Mechanical Over-Speed trip test is attained a "Master Reset" must be done and the Hydraulic Control Oil Pilot valve must be manually reset before the unit can be re-started.

If the maximum allowed speed is attained and the unit Over-Speed protection has not tripped the turbine the test should be aborted and proper repairs made.

The Over-Speed test may be aborted at any time conditions warrant during the "Mechanical Over-Speed Trip Test" by clicking on the "Abort Mechanical Over-Speed Trip Test" button and clicking "OK" on the dialogue box that pops up.

The Over-Speed test may be aborted at any time conditions warrant during the Over-Speed Trip Test by clicking on the "Abort Electrical/Mechanical Over-Speed Trip Test" button and clicking "OK" on the dialogue box that pops up.

Careful observation of the unit Vibration level and Exhaust temperature should be maintained at ALL times during the test.
 
M
Thanks for the idea CSA. Tomorrow I will try to post it on tinypic.

If I do get it posted can I just provide the web address here for folks to follow to view the screen shots and such?

Thanks for any help you are willing to offer, I am new at this.

Thanks
Mark Allen
 
M
I tried to up-load the screen shots to photo-bucket but the screen shots are in an Ex-cell book and I don’t know how to get them to load.
It looks like there will be a GE engineer at the plant site sometime in October. I will get him to review the procedure then.

I thank you for your help.

Thanks
Mark Allen
 
Top