Our Frame-V machine is running with Mark-Vie control system. Out of two, One flame scanner reading is not matching in all three R, S & T packs in Mark-Vie control system and voting mismatch alarm is appearing frequently between R, S & T packs.

As per settings, Voting mismatch alarm will appear in case of value difference greater the 5 between any two packs.

Please guide us for resolve this alarm.

Regards,
Vimal Gupta

 

Dear Vimal Gupta,

you need to use the toolboxST application to look at the flame values being reported from each core to understand which core is causing the voting mismatch. If you navigate to the appropriate hardware input and then click on that signal you should see the values being reported from each core before being voted. Let us know what you find and report back. The fact that all the cores do not agree can usually be caused by a problem with the I/O pack for that particular core. Assuming your unit is using 2 flame scanners and the signals are fanned to the three cores then the problem is usually not a problem with the scanner itself. The only situation I have seen where that is not the case is when a scanner is very erratic to the point that the value is changing so fast the cores see different values during each scan.

 

I have checked in toolbox ST and found value of each core is changing very fast manner. Total variation band is almost same for each core as below:-
PR3: 236 (Varying band 215-258)
PS3: 250 (Varying band 229-258)
PT3: 246 (Varying band 229-257)
Voted: 246

Second another flame scanner value is fine. it is almost constant (not varying such fast) and voting matched with all packs. Both flame scanner hardwire connected on same pack. One scanner is not having problem in same pack, another is having voting mismatch.

Kindly guide us.

 

VKGUPTA,

How long has this problem been persisting?

What are the exhaust temperature spreads when this problem is occurring?

What fuel is being burned when this problem is occurring?

It could be that there is, in fact, an unstable flame in this particular combustor which is causing the erratic and unstable flame intensity signals.

Have you tried replacing the flame detector? Or swapping flame detectors to see if the problem follows the flame detector/wiring?

Have you checked the wiring and field terminations for this flame detector circuit?

While you are troubleshooting the problem, can your operator use the 'Alarm Lock' function to prevent nuisance alarms until the problem is resolved?

 

Dear Vimal,

so based on the information you provided. there is one flame detector indicating good steady flame, and the 2nd is erratic. At this point you need to work on a logical path to identify the what is causing the flame detector input to be erratic. This could be caused by wiring from the terminal board to any junctions and finally to the detector device itself. It could be the detector failing or an obstruction in the path to the flame. Or it could be a problem with the MKVIE hardware. If these are the older style of detectors that use 335VDC to excite them, it could be an issue with the voltage being supplied. So you need to work systematically to identify the cause, one step at a time. Please report back and let us know how you proceed.

 

Sir,
Right now our machine is running so we will sweap the flame scanner during shutdown condition.