Mark 6 Diagnostic Alarm

M

Thread Starter

Mohamed Salem

We have Mark6 control system , and one Alarm is repeated continuously this alarm is
[R]slot 14 VAIC diagnostic alarm G1\xvaict0s14_a
slot 14 VAIC diagnostic alarm G1\xvaict0s14_a
[T]slot 14 VAIC diagnostic alarm G1\xvaict0s14_a

pls tel me why this alarm is generating and how to fix this alarm.

Thanks,
Mohamed salem.
 
When did this problem begin? After a maintenance outage? After some work was done on the BOP or DCS panel? After some mA transmitter was recently replaced or "calibrated"? After an electrical storm (lightning)?

The alarm, likely being annunciated on, and copied to this forum from, the CIMPLICITY Alarm Viewer is trying to tell you that at least one of the mA signals configured via the VAIC card in Slot 14 of the three processor racks (so, a TMR mA input or mA output) has a problem, and if it's being continuously annunciated then clears then re-annunciated then clears, continuously (in other words, the alarm condition is toggling or dithering), then it's likely an intermittent problem.

The problem may be in the cables connecting the I/O terminal board (usually a TBAI) to the three VAICs in the three processor racks (unlikely, since it would require three simultaneous cable failures under normal circumstances), or the VAICs (again, unlikely since it would require three simultaneous card failures under normal circumstances), or the TBAI (more likely, since it's common to all three VAICs in all three processors), or the wiring of the affected point (more likely, since it's common to all three VAICs/processors), or the actual field device (more likely, since it's common to all three VAICs/processor).

You will need to use Toolbox to check the Diagnostic Alarms of the VAICs in at least one of the processor racks to determine which signal, specifically, is being affected, and which terminals the signal is connected to on which TBAI.

I would suspect there are other alarms, Process or Diagnostic, related to an intermittent analog signal, or that some value on some display is intermittent and that would most likely be the affected signal the Diagnostic Alarm is trying to alert you to.

Lastly, the CIMPLICITY Alarm Window should have a button labeled 'ALARM LOCK' that can be used to temporarily disable a nuisance alarm (and if the Alarm Logger is working, it will prevent repeated logging of the alarm as it dithers/toggles). Select the offending alarm by left-clicking on it, then click on ALARM LOCK. If the ALARM LOCK button was properly configured (and that's never a guarantee on a GE HMI...) then the alarm will be prevented from being continuously dithering. It will still be visible in the Alarm Window (as it should be to alert a conscious operator or technician to a condition that needs to be resolved) until such time as it is resolved and can be then unlocked by left-clicking on it to select it and then clicking on ALARM UNLOCK (also never a guarantee that this button works properly either on any GE HMI).

So, this should help for now.

Please write back and let us know what you find.
 
Y

yasser rashad

Dear/mohamed

how are you?

we have after the commissioning finished, the same alarms repeated. i have checked with I&c people told no problem, fault alarm came in VAIC rack, but do not affect the operation of the unit.

if click master reset it will go and return back again, from 3 years back still alarm persisting.

please if you found the solution tell us.

regards
Yasser Rashad
UAE
 
K

Kamel Ibrahim

we have 9Fa machine with Mark 6 and this alarm

[R]slot 14 VAIC diagnostic alarm G2\xvaicR0s14_a
slot 14 VAIC diagnostic alarm G2\xvaicR0s14_a
[T]slot 14 VAIC diagnostic alarm G2\xvaicR0s14_a

persisted and after 75 milli second a combustion trouble alarm and high exhaust temp spread trip happened.

trends show that load dropped in no time from 175 mw to 110 mw with no change in TTRF, little decrease in exhaust temp. and after mw dropped spread 1, 2, 3 increased rapidly in same rate and same values and exceeded the allowable with little decrease in exhaust temp and FSR speed and temp was increasing.

so what is the possible reasons and how to detect the fault.

thank you
 
Kamel Ibrahim,

175 MW on a 9FA is not Base Load, so the machine was probably being operated on Pre-Selected Load Control at Base Load. For such a dramatic loss of load in such a short period of time coupled with a sudden increase in exhaust temperature spreads, something either extinguished the flame in some combustors (a slug of liquid in the fuel line or atomizing air line (we don't know if the machine is gas fuel-only or dual fuel), probably condensate or water), or there was some problem with the fuel supply (you didn't say what fuel was being burned--natural gas or liquid fuel), or possibly, if liquid fuel was being burned and NOx Water Injection was running, some problem with water injection flow-rate control.

Please provide the list of all of the inputs (and outputs) connected to the VAIC cards in slot 14 of <R>, <S> and <T>. You can get the list from Toolbox. Usually, the I/O will be connected to a TBAI and the TBAI will be connected to the VAIC cards in the three processor racks via cables. (Note that while a VAIC is primarily an analog input card, they can have as many as two (2) analog outputs.)

It would also be helpful if you could tell us exactly what the Diagnostic Alarms were on the VAIC cards. The alarm you listed only tells an operator that one (or more) Diagnostic Alarms is(are) present on the VAIC card; one needs to use Toolbox to actually view the specific Diagnostic Alarms (though I'm told some newer versions of TCI/CIMPLICITY can actually record/display individual card Diagnostic Alarms, so you might find them in a log file on an HMI).

If load dropped and spreads increased, it's a pretty safe bet that flame was lost in multiple combustors. It may--or may not--be related to the VAIC problems. I suspect there were other alarms (Process- and Diagnostic) that were annunciated at the time of the trip that haven't been listed, and that this post is an attempt to tie the trip to the VAIC card(s) in some way, which, again, may--or may not--be the case. It would be most helpful if we had ALL of the alarms prior to and during and immediately after the event to review.

I'm at a loss to understand and explain the bit about increasing exhaust temperature spreads and "stable" exhaust temperature (I presume you mean TTXM) during the loss of load. If flame is lost in multiple combustors then TTXM should also be decreasing by virtue of the fact that a loss of flame in multiple combustors would cause the associated exhaust T/C values to decrease which would cause TTXM to decrease. FSRN would probably be increasing since most DLN machines use load-biased Droop Speed Control (called "Constant-Settable Droop Speed Control") and load decreased. But that whole paragraph is difficult to understand.

At any rate, the trip is likely NOT related to VAIC problems. The possible exception might be if there was a 125 VDC battery ground (a "hard" ground") that had existed for some time without being resolved. But, even then, a series of problems would have had to occur for this scenario to cause what's being described.
 
thank you for the useful explaination

regarding fuel it's dual fuel DLN2+ and machine was using natural gas in this time and it was in AGC control.

before the diagnostic alarm there is one alarm for fuel coalser filter condensate level high. and after unit trip fuel change over command given by DCS due to 2 high level alarm persisted, but notice that some times before turbine tripped due to condensate level 3 high without affecting the spread. and this time it was only high. and i don't know how condensate will reach the turbine, coalser filter should prevent it.

i meant that spread 1,2,3 was increasing and TTXM was NOT changing so much and thermo couples 20-30 had less values and 24-26 were 300 F less than TTXM

VAIC 14 contains
FPG1C,2A
AFPAP1A,1B
DWATT
FD-INTENS1,2
HAZARDOUS GAS SENSORS
CSRIHOUT
CPD1B
FPG2B
DVAR
CPBH
AFPCS
CUST_DWATT
CUST_FSR
AGAIN THANK YOU FOR YOUR HELP
 
Kamel Ibrahim,

You are welcome for the information, and thanks for answering most of the questions.

The fact that the coalescing filter levels have been high before is interesting. Coalescing filters don't always catch everything, and, if the gas fuel temperature is too low then moisture can condense as the pressure drops across fuel control valves and fuel nozzles. There have also been many cases where coalescing filter level switches have malfunctioned, as in, they didn't indicate high levels when high levels were actually present.

The last two signals on the list of VAIC I/O are likely analog outputs to some DCS or other control system or data archival/retrieval system. If the load data you were looking at came from that output then it may be suspect because of whatever caused the VAIC Diagnostic Alarms.

Based on the information provided, it's not possible to say for sure what happened with the VAIC or why the turbine tripped on high exhaust temperature spread. It's difficult to understand how load could drop so much and TTXM could remain "steady" AND exhaust temperature spreads were increasing. It just doesn't make much sense.

Again, I have seen odd trips like this occur when a 125 VDC battery was present for some time and left unresolved. Also, it certainly seems like the VAIC in question is pretty heavily loaded; it would be a good idea to ask the packager/OEM if this card in this slot in the processor racks should have as much I/O connected to it as it seems to have. There are limits to the amount of I/O per groups of slots in Mark VI processor racks, and this seems to be nearing a limit, especially if there are other VAICs in adjacent slots.

Without knowing what Diagnostic Alarm(s) were specifically present on the VAIC, again, it's very difficult to say precisely what happened.
 
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