Alarms in frame V machine in <R> core (L39VF12, L39VF8 and etc)

N

Thread Starter

NVS

Hello sir,

We have Frame 5 GT
Today we observed following Diagnostic VOTER MISMATCH alarms in <R> core generated and reseted

L39VF12, L39VF8, LV39VF5, LV39VF4, LV39VF9Y, LV39VF8Y, LV39VF7Y, LV39VF5Y, LV39VF4X, LV39VF3Y and LV39VF1Y.

we don't observed any abnormality in the system, but we don't find any reasons for this alarms

only things we observed are this signals belongs to vibration probes connected to TBQB board in <R> core

so what might be the problem and any checks can be performed for analyse the above alarms

Thank you sirs,
 
Hello, NVS,

The turbine is a Frame <b>5</b>, and the control system is a Mark <b>V</b> Speedtronic.

Intermittent problems, especially Diagnostic Alarms, are difficult to troubleshoot. And, you didn't tell us if the Mark <b>V</b> was a TMR or a SIMPLEX control panel.

In any case, ALL of the seismic (velocity) vibration pick-ups are connected to the TBQB or <R> (regardless of whether or not the control panel is TMR or SIMPLEX). For a TMR control panel, the signals are "fanned out" to all three TCQA cards in the control processors. So, while the problem may be the TBQB, if only <R> annunciated the Diagnostic Alarms (in a TMR control panel), it would seem more likely the problem was:

1) the cable/connectors on the cable connecting the TBQB to the TCQA; or,

2) the TCQA card in <R>.

It is a well-known fact that the cable connector receptacles and the printed circuit card connector pins can become corroded. It is necessary to periodically (approximately every two years) to re-apply a light film of conductive grease to the female connector faces and then insert the connector into the receptacle. The female connector should be removed and re-inserted a couple of times to ensure the receptacles and the pins get the best possible coating of grease. (NOTE: Too much grease is as bad--or worse--than too little.) Any time a new card is installed to replace an existing card the conductive grease should be applied and the same process followed.

Many times nuisance alarms (Process- and Diagnostic) can be traced to corroded or loose connectors and/or terminals.

The cable itself may be damaged. If the TCQA card in <R> has been replaced many times, it's common for the female connector to be loosened by too much force being used to pull the tab of the connector, or not using the tab (which happens all to frequently).

So, check all the ribbon cable connectors for tightness, and it it's been a while since conductive grease was applied (to any connector!), try applying some. It's a good idea to shut off the power to <R>, or any processor being worked on for this procedure, before removing any cables from their connector. It should not be done with the turbine running, either.

In the future, when posting for assistance please post as much information about the turbine at your site as possible. Tell us what was happening when the problem occurred; how long since the last maintenance outage; if the problem occurred after a trip from load or during starting or shutdown; or if the problem occurred during loaded operation, while loading or unloading or at steady-state load. The more information you provide, the happier you will be with the response(s) you receive.

Lastly, you can do some proactive research by discovering which of the 15 or 16 possible seismic vibration inputs are actually used at your job, and which physical pick-ups are connected to which inputs. The I/O Report (F:\UNIT1\TC2KREPT.TXT) and the I/O Assignment file (F:\UNIT1\IO.ASG) can both be helpful for this. Both files are ASCII text files which can be viewed using any text editor (MS-Windows Notepad, for example). But remember: if you are viewing the file just looking for information when you close the file if you are prompted to save any changes before closing--just say, "NO!"

Unintended changes can cause problems, but that shouldn't prevent you from viewing the file(s). You can copy the files to a floppy or optical media and then view it on another computer, or copy it to another directory (F:\USER, for example) and then view it without any danger of accidentally causing any unintended problems!

Hope this helps!
 
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