Hello All


I am interested to discuss here about Mark V works ( like lvdts calibration...)on a HGPI for a frame 9E DLN1

Thank you for your attention
James

 

James,

ALMOST everyone will tell you you need to calibrate valves and IGVs.

Except for CSA and I.

We will tell you that you should first verify the existing calibration of LVDT feedback. Because AutoCalibrate has NOTHING to do with servos or stability (unless the AutoCalibration isn't done correctly).

And ONLY if the existing calibration of the LVDT feedback for a particular device is found to be inaccurate THEN and ONLY THEN should the LVDT calibration be performed. And ONLY if the end-points of travel are known and correct in ACALIB.DAT.

Particularly for gas fuel valves (except the SRV) if the valves are "calibrated" and it changes the LVDT feedback calibration significantly it can cause problems with emissions output. So, this should be a very large concern when considering gas fuel valve LVDT calibration without actually verifying the existing calibration.

IF the gas fuel valve(s) is(are) replaced during the outage, then it will be necessary to calibrate the LVDT feedback.

And, when performing LVDT feedback calibration on newly replaced devices, the servo valve current polarity should ALWAYS be verified before calibrating LVDT feedback.

You should also record the existing (as-found) values of null bias current and regulator gain and then check them against the values in the Control Specification, especially for devices which are replaced during the outage, and the proper starting point under these circumstances is to return the device values to the proper values before performing a calibration.

And that's that for LVDT calibrations.

Now, for the Mark* V, depending on the condition of the area where the Mark* V control panel is located it may require housekeeping. Dust, cobwebs, etc. The panel should be powered-down in an orderly fashion--DO NOT FORGET to unplug the J7 cabled in the <PD>, as well as the J8 and J12 cables--and a good cleaning should be performed using a vacuum cleaner with an anti-static brush, and each card should be vacuumed gently and completely. BEFORE powering-down the Mark* V, it's a good idea to make copies of all alarms--Process and Diagnostic! This may be VERY important when it comes time to start up.... And, if you have any time before powering down, it's a good idea to investigate and resolve any alarms (Process and Diagnostic) as soon as possible. You may get some push-back from site personnel--but I can tell you that when it comes to start-up time if there are Diagnostic Alarms or Process Alarms that are unresolved, you are going to be the one on the hook for fixing them all, and there won't be much time to do that (because the mechanical work ALWAYS takes longer than expected and the controls work always get minimized when it's time to finally push the button!). Best to have a record of alarms (Process and Diagnostic) that you can point to to say, "That existed before the outage!" (You have been warned.)

While the panel is powered-down it's a good time to apply conductive grease to all of the ribbon cable connectors to prevent corrosion and poor electrical connections. And, the grease should be applied in a sparing, even manner--because too much grease is worse than no grease at all. Each ribbon cable should be removed from it's receptacle and re-installed, several times to loosen any corrosion, and then a small amount of conductive grease should be applied to the ribbon cable connector over the entire face of the connector. Then the ribbon cable connector should be inserted into the receptacle and removed a couple of times, and then firmly pressed into the connector.

There is one cable on each of the four processors, the 3PL cable, which has NO pull tabs. When removing this ribbon cable from its receptacle (each time it's removed from its receptacle) extreme care should be used to make sure the clip on the back of the connector does not come loose. This cable connects the LCC/SLCC to the DCC/SDCC and TCQA, and TCQB if installed. It was HUGE oversight of GE not to put pull tabs on this cable, and it is easy to damage the cable and cause unintended problems....

Many field devices (pressure switches, limit switches, etc.) will be removed and reinstalled. Before powering-up the Mark* V it's always a good idea to do a check for grounds of discrete (contact) inputs and solenoid outputs, particularly.

The wheelspace T/Cs will be removed and reinstalled--and it's highly likely that one or two or more of them will be reinstalled improperly. This goes for many of the exhaust T/Cs, as well. It's very good to check each of the exhaust T/Cs in their radiation shields to make sure they are not bent or the tips are not touching metal (many "well-meaning" millwrights/pipefitters will play with the T/C tips, bending them and not returning them to the same position). Any exhaust T/Cs which are removed--if they aren't the "Frankenstein" style T/Cs, may not be reconnected properly in the junction box. T/C terminations (ALL T/C terminations for wheelspace and exhaust T/Cs) are extremely important. GE typically uses unique terminal boards which are misunderstood and can cause problems with T/C readings which can lead to performance issues, small ones--but sometimes they are enough to cause contract concerns if the unit is only performing marginally to begin with.

It's HIGHLY recommended to do loop-checks of all field devices and instruments that were disconnected or removed and reinstalled or replaced during the outage. This has to be done AFTER the Mark* V is powered up again.

Once the Mark* V is powered-up again, it's a good idea to investigate and resolve any Diagnostic Alarms. The sooner the better--before start-up, that is. This goes for all Process Alarms, too.... Remember that list of alarms you made before the panel was powered-down.?.?.?

You may be asked, nicely, to do some "extra" work. If it was broke before, and you can't fix it, it's your problem after you get involved. DON'T GET persuaded to make CIMPLICIY display changes--especially on a multi-unit site. That's not your job, unless you are VERY familiar with the version of HMI (or <I>) in use at the plant and know the exact steps for completing such changes. And before you do anything--MAKE BACK-UPS. (And Make back-ups when you're done!)

So, is that enough? Be wary of being forced into "calibrating" valves and IGVs, just because that's what we always do. There's likely NO RECORD of previous calibrations, the as-found and as-left conditions. And, if even one gas valve LVDT calibration wasn't done correctly the emissions after the re-start might not be what they were before, and everyone is going to point to the controls person.

That's about it. Cover. Your. Arse. Do your job and document what you did. I think CSA attached an LVDT calibration record to a post a few years ago. VERY important.

Go forth and conquer!

 

@WTF

Thank you very much for this post
It contains many important advises to follow!

Stay healthy & blessed

James