J
Hello All,
We are having an issue on one of our machines that is intermittent, and I am having difficulty narrowing down the root cause, I'm hoping you can help.
Background:
2000-2001 vintage GE 7EA combustion turbines
Mark V controls with HMI
Dual fuel machines
Simple Cycle
Midwestern US
Due to oil quality we have experienced servo failures on our gas valves, typically during cold months. We have been diligently working over the course of a few years to correct this issue and have found the most success using a varnish removal unit that is equipped with a chiller that cools the oil before filtering. With this filtering and regular testing we feel that we are correcting the oil quality issues. But, due to past failures, management requires us to test operate our gas control valves daily.
Issue:
Recently when manually testing a valves movement using the auto calibrate feature, one core will drop out and register "Speed increased more than 5%" for that cores status at the bottom of the window. This condition will happen intermittently, always on the same core, the valve can be placed back into "idle" and then back to "manual" the problem may re-appear, or it may not. The valve will move normally without the issue. But when it is in the core dropped state, the valve will move but will be off by about 15%.
The issue will appear on any of the unit's gas valves, it is not just isolated to one. When in the dropped state, there are no additional diagnostic alarms that appear, the only alarms that are in are the normal ones associated with manually moving gas valves.
Typical servo readings at 50% with no issue:<pre>
<R> <S> <T>
Required 50 50 50
Actual 49.91 49.83 49.9
Servo Current -4.66 -4.68 -4.05</pre>
Same valve with the core dropped<pre>
<R> <S> <T>
Required 50 -25 50
Actual 32.52 32.37 32.5
Servo Current -35.4 56.83 -34.77</pre>
Troubleshooting efforts so far:
As I mentioned, this problem is intermittent so trouble shooting is slow going.
Checked shield connections at Mark V - No change
Rebooted <S> core - No change
Re-seated ribbon cables in <S> core (applied nyogel)- No change
Replaced TCQA board in <S> core - No change
My servo connections in <S> core terminate on my QTBA terminal board, travel to the TCQC board, and then on to the TCQA. If I unplug just the JGG cable running from QTBA to TCQC, then the valves will move just fine and <S> core will not have any information but will not drop out.
My question to the group is, has anyone experienced this before? If so, what did you find? If anyone has any insight that might point me in the right direction it would be much appreciated.
Hopefully I have provided enough information, but if not I'll get whatever info the group deems necessary as long as it is within my capabilities to get.
Thanks in advance.
We are having an issue on one of our machines that is intermittent, and I am having difficulty narrowing down the root cause, I'm hoping you can help.
Background:
2000-2001 vintage GE 7EA combustion turbines
Mark V controls with HMI
Dual fuel machines
Simple Cycle
Midwestern US
Due to oil quality we have experienced servo failures on our gas valves, typically during cold months. We have been diligently working over the course of a few years to correct this issue and have found the most success using a varnish removal unit that is equipped with a chiller that cools the oil before filtering. With this filtering and regular testing we feel that we are correcting the oil quality issues. But, due to past failures, management requires us to test operate our gas control valves daily.
Issue:
Recently when manually testing a valves movement using the auto calibrate feature, one core will drop out and register "Speed increased more than 5%" for that cores status at the bottom of the window. This condition will happen intermittently, always on the same core, the valve can be placed back into "idle" and then back to "manual" the problem may re-appear, or it may not. The valve will move normally without the issue. But when it is in the core dropped state, the valve will move but will be off by about 15%.
The issue will appear on any of the unit's gas valves, it is not just isolated to one. When in the dropped state, there are no additional diagnostic alarms that appear, the only alarms that are in are the normal ones associated with manually moving gas valves.
Typical servo readings at 50% with no issue:<pre>
<R> <S> <T>
Required 50 50 50
Actual 49.91 49.83 49.9
Servo Current -4.66 -4.68 -4.05</pre>
Same valve with the core dropped<pre>
<R> <S> <T>
Required 50 -25 50
Actual 32.52 32.37 32.5
Servo Current -35.4 56.83 -34.77</pre>
Troubleshooting efforts so far:
As I mentioned, this problem is intermittent so trouble shooting is slow going.
Checked shield connections at Mark V - No change
Rebooted <S> core - No change
Re-seated ribbon cables in <S> core (applied nyogel)- No change
Replaced TCQA board in <S> core - No change
My servo connections in <S> core terminate on my QTBA terminal board, travel to the TCQC board, and then on to the TCQA. If I unplug just the JGG cable running from QTBA to TCQC, then the valves will move just fine and <S> core will not have any information but will not drop out.
My question to the group is, has anyone experienced this before? If so, what did you find? If anyone has any insight that might point me in the right direction it would be much appreciated.
Hopefully I have provided enough information, but if not I'll get whatever info the group deems necessary as long as it is within my capabilities to get.
Thanks in advance.