I've dug through all the IO and CSP and Application manual and I can't get a solid answer.

MkV TMR on a steam turbine, WinNT HMI. The alarm reads something like "Probe Failure" but it traces back to a logic signal called L39VF4Y. This logic is "attached" to an IO. In the IO.asg here's the line:

TCQB_VFLT_8 L39VF4Y LOG ; TCQB_VFLT_8 Probe failure on PROX08 Circuit

From the application manual I see that the TCQB card is inside the modules and used for vibe/proximeter. To me, this failure signal looks like a DIGITAL INPUT...but I can't find it on any of my I/O wiring diagrams (though I may be missing something).

Any input on what turns this failure logic on? (Some things were changed in the plant...I just want to know what this input is "watching")

When I force the L39VF4Y to 0 (it's currently 1) the probe failure alarm clears but I get a voter mismatch alarm on L39VF4Y.

Lastly, why do sites install a bently nevada system (in our case 3300) when the signal from the sensors is just paralleled to both the 3300 and the mkV? What's the point...the MkV does the protection, why have a 3300 too?

 

I don't believe this is a discrete input; it's probably an "internal" logic signal that is written to by some diagnostic software in the PROMs on the TCQB card.

Have you confirmed that the prox and probe on the turbine are working correctly?

Have you checked the cabling between the B-N rack and the Mark V? I believe there is some kind of card between the B-N output and the Mark V input terminals; is that "channel" working correctly?

Lastly, you must not have read the press release of a decade or more in the past. B-N is owned by GE. And, there are usually some diagnostic vibration functions that cannot be done with the Mark V that can be done with the B-N equipment. So, the B-N rack is usually sold with most steam turbines. Especially is the unit was sold before the assimilation of B-N by GE.

 

> Have you confirmed that the prox and probe on the turbine are working correctly? <

The MkV and BN are showing valid vibration readings most of the time. What started this ordeal was something was causing erratic high vibrations spiking up and down (like 15-25mills). It wasn't a valid reading.

> Have you checked the cabling between the B-N rack and the Mark V? I believe there is some kind of card between the B-N output and the Mark V input terminals; is that "channel" working correctly? <

From all the references I have, it appears the signal from the probe is parallel into the mkV and the BN. I initially figured the BN just sent a signal over to mkV, but the drawings say otherwise.

PV said in another thread that a small current is put in the prox sensor loop and if the mkV doesn't see this current it will give an error--don't know if that is applicable or not.

I'm just doing some side-line thinking. The decision making structure is unique here. I do lots of the figuring for self education Therefore, I haven't dug in hard to troubleshooting. It's probably something simple as most things usually are.

My initial assumption was that the BN system provides many more functions and analysis than the mkV. I'm aware GE bought BN--and as some will argue, did to BN what GE does best..............we all know what that is LOL

Thanks again!

 

GE Steam Turbine practice (before and after GE purchased B-N) is to wire the vibration proximitors directly to the turbine control (Mark V or Mark VI or Mark VIe). This is because on the steam turbines, the proximity probes are used for protection (unlike on gas turbines where seismic probes are used for protection). The B-N monitoring equipment is just that - monitoring, and thus is secondary to the turbine control.

 

The vibration inputs of the Mark V impress a small current through the transducers when the turbine is not running (and the velocity pick-ups are not putting out any signal). This is how it checks for pick-up "readiness" when the turbine is not running. This practice started with the Mark IV, and has continued through the latest generation.

But, I don't believe this happens when the turbine shaft is spinning.

 

I forgot to paste a section I had wanted to move to the top of the post: This refers to velocity (seismic) vibration pick-ups only, because they are passive devices which don't have any signal unless there is some minimal "vibration".

That's why the Speedtronic passes a small current through the circuit when the unit is not running.

I don't believe this applies to active inputs like proximity inputs which are powered and have a voltage present at all times regardless of whether or not there is movement/"vibraton".

Sorry for any possible confusion.