We had an HMI upgrade on Frame 7EAs in December and since that time receive SOEs for low lube pressure 63QA-1 and low lube pressure-trip load63QT2A/B on one unit. The problem is it appears to be demanding a start of Aux Lube Pump and as soon as pump starts those 3 bits' logic returns to a "0" logic but the pump continues to run for approx. an hour. Yesterday I saw the logic states had changed on the event logger and in checking discovered the immersion heaters were not on. With the unit at zero speed this should not initiate the aux lube pump and not receiving alarms only seq of event. All units received upgrade at same time and this is occurring on only one. If anyone has encountered this previously or can point me in the right direction will be greatly appreciated.

 

I've never seen this particular problem, and it's very odd that if you are getting all three signals going to a logic "1" at the same time that the unit isn't tripping. It's not clear if you're saying this is happening when the unit is running or when it's shut down, or both. Can you please clarify?

What have you done to try to troubleshoot the problem?

Are there any Diagnostic Alarms when this is not happening? Are there any Diagnosic Alarms when this is happening?

Are there any other "unusual" SOEs or EVENTs when this occurring?

Are there any Process Alarms when this is happening? Because you should be getting an 'Aux. L.O. Pump Running' alarm when the pump starts when the unit is at rated speed and should be running on the Main L.O. Pump.

These three signals should not be all on the same contact input terminal board on the same core (I'm presuming the turbine has a Mark V Speedtronic control system, but even if it has any other Speedtronic they should be on separate contact input terminal boards). So, it's not likely a single I/O terminal board or I/O card.

The two 63QT-2 switches are usually in a completely different location from the 63QA-1 switch, so they should not be sharing a common "bus" wire.

If the Aux. L.O. Pump starts when the unit is at rated speed and the low pressure condition resolves itself, generally the only thing that will shut the pump down is to turn the HAND-OFF-AUTO switch on the motor's starter to the OFF position for a couple of seconds then release it to the AUTO position. There's not usually any logic in the Mark V to automatically shut it down if the pressure returns to normal, even for some period of time.

This is a pretty strange problem. The fact that it's happening to all the L.O. pressure switches is pretty interesting. It might indicate that there is actually a low L.O. pressure condition if/when it's happening when the unit is running.

When the unit is shut down and OFF Cooldown, the L.O. pressure *should* be low, and the signals associated with 63QA-1, 63QT-2A and 63QT-2B should all be logic "1" all the time, indicating low pressure. They should not be changing to logic "0" when the unit is not running and is not ON Cooldown. So if the signals are changing state when the unit is not running and is not ON Cooldown, then something is amiss.

Usually, the signal L4QAZ has to go to a logic "0" to start the Aux. L.O. Pump.

<pre>L14HSX L63QALY L52QA L4QAZ
--| |--------| |--------|/|-------------------( )
| |
| |
L1Z | L14HSZ |
--| |-------------------|/|----</pre>

In the rung, L14HSX would be a logic "0" when the unit was shut down and OFF Cooldown, so the state of L63QELY wouldn't matter if it changed state. L1Z would be a logic "1" when the unit was not running and OFF Cooldown, and L14HSZ would be a logic "0", and because L1Z is a "1" and L14HSZ is a "0" L4QAZ will be a logic "1". So, the signal to start the Aux. L.O. Pump should not be coming from Speedtronic if your L4QAZ rung matches the one above.

The only other thing that starts the Aux. L.O. Pump is the L.O. Tank Immersion Heater, and that's usually done through a hard-wired contact from the heater control circuit which is usually driven by a low tank temperature signal from temp switch 26QL-1. Usually this switch is directly connected to the L.O. Tank Immersion Heater's control circuit, but sometimes it wired through the Speedtronic. I have heard there were some units which used L.O. Tank Temperature T/Cs connected to the Speedtronic to drive a logic signal to turn the L.O. Tank Immersion Heaters from the Speedtronic. But, I've never actually seen a unit configured like this.

If you have a Mark V, or a Mark VI or Mark VIe, you could run a VIEW tool (for the Mark V) or a Toolbox Trend to look at the signals from the L.O. pressure switches, the L.O. Tank Temperature signals, the Aux. L.O. Pump Master Control Logic (L4QAZ), and the Aux. L.O. Pump Motor Starter Status contact (L52QA). If you have a status contact from the L.O. Tank Immersion Heater control circuit (L52QT, I think) you should trend that as well.

If the panel received new PROMs as part of the HMI upgrade it's possible some part of the upgrade was not completed properly.

I'm not a fan of just running the "total job compiler" if there were no changes and then downloading the compiled files to the panel, but that might help in this case (and it might not; but it probably won't hurt).

I would recommend recreating UNITDATA.DAT, then recompliing the Table files, then recompiling the CSP, then downloading USER to all the processors (<C>, <R>, <S>, and <T>). With the unit OFF Cooldown, shut down all the motor starters, including the Emer. L.O. Pump, and then shut down the Mark V processors, one at a time, until they are all off.

Then start powering them up one at a time.

When the processors all get back to A7, the Speedtronic will try to put the unit ON Cooldown, so as you start re-energizing all the motor starter breakers it's likely that the Aux. L.O. Pump will start, as well as the Hyd. Ratchet or Hyd. Pump, and maybe even the Emer. L.O. Pump. You might be able to just select COOLDOWN OFF and stop the cooldown sequence before you start powering the motor starters back on, which would be a good thing to try.

You'll need to clear all erroneous Process- and Diagnostic Alarms, and make note of any that won't clear that should.

Once everything is back on and the unit is OFF Cooldown, monitor for the condition again.

If it continues, you'll probably need to get GE involved.

Whatever happens, please write back and let us know.

 

srl,

Is there any update to this thread?