Dear All,

Is it safe to continue running the Unit with small part of the DTBD card at <QD2> core burn due to shorting solenoid? Ours is ST with Mark V control system. A part of JS1 & JS2 ribbon cable connected to TCRA card also burn.

Regards

 

Please do not remove any terminal boards from the panel when the unit is running especially from QD2 is inviting trouble or maybe disaster. Shutdown the unit and do the work

 

It's presumed from the original post that the unit is still running or did not shut down or trip because of the damaged cards.

The answer to a question like this can only be determined on site by someone who can evaluate the outputs which are affected by the damage. The easiest way to do this is to review the I/O Assign file, or the I/O Report (though many Mark V's used for steam turbine control did not include an I/O Report (TC2KREPT.TXT), but rather a Turbine Connection Diagram, which can be difficult to search through in a condition like this).

This is at a minimum, because there may be other damage to communications (IONET) that are not immediately clear.

Continuing to run a turbine with a damaged card and cables is a recipe for disaster. The unit may run just fine, but during a shutdown or an emergency trip there may be problems associated with the outputs which are inoperable.

My immediate concern is that it's probably unlikely anyone has isolated the power which is present in the damaged cards/connectors/cables from outside sources, and which may cause a serious danger to continued operation with damaged cables and cards.

But, managers and supervisors get paid to evaluate the risks and make these kinds of decisions. If they are lucky or good managers/supervisors then they may save the company some money by delaying a shutdown to replace the damaged components.

If they are unlucky/ungood, well, the cost of the eventual shutdown to replace the damaged components may increase by orders of magnitude.

In any case, managers and supervisors opinion, beliefs and spreadsheets will win out.

I've always heard it's better to be lucky than good. One can be good and unlucky, and that can be fatal. One can be not so good and lucky and live to tell about it.

It's also curious that a Steam Turbine would have a second, optional <QD2> core, since most steam turbines don't have that much discrete I/O. Hmmm....

 

Thanks all for the reply, yes the unit is still running until next weekend where we plan to shut it down to replace the card. From i/o list most of the signal is connected to test solenoid so what we did just do the test by using manual bypass valve and it's working. My concern is the damage ribbon cable, can it affected the TCRA card?

regards

 

TCRAs are pretty simple cards; 30 relays per card. It's certainly possible that if the cables interconnecting the TCRAs and the DTBC/DTBD cards are damaged, then the TCRA can be damaged.

Remember when replacing DTBC/DTBD cards that power may--and quite often--does come from sources other than the Mark V! So, be sure all power to the DTBC/DTBD card(s) is isolated before lifting wires and replacing the interconnecting cables to the TCRA card(s).