At my place of work we have an LM2500DLE driven gas compressor. It uses Bentley Nevada Proximity Probes and Proximetors that are wired direct to a VVIB termination board on the MK6 so the signal conditioning/scaling is performed within the MK6 itself.

When carrying out testing, I injected a simulated value of 100microns (3.93mils) from the field. But when interrogating the MK6 logic from Toolbox I'm only reading 25microns (0.98mils), and the same on the Cimplicity HMI. This fault is common for all the Proximity Probes, on the Compressor Unit/Train

I can see the input from the probe in Mils inside the logic within the Toolbox software for MK6, but I can't find the raw data, or where the scaling is configured/carried out.

The mapping of data to the HMI and Station controls are correct. It is the initial value that is input to the MK6 that isn't being carried out correctly.

To be sure it's a MK6 Scaling issue, I have checked all the field devices (cabling, barrier, probe, proximetor) and made sure the galvanic barrier isn't suppressing the AC mV signal that is being used.

Any help would be great!

 

NGDave,

I hate to ask but, exactly how are you simulating the signal--AND, are you simulating the keyphasor input at the same time?

 

NGdave,

Also--is this only happening when the unit is not running? In other words, are the proximitor inputs working when the unit is running?

 

Sorry for not getting back with an update.

The issue turned out to be (as suspected) a scale factor issue on all the radial vibration probes in Toolbox (specifically the VVIB card).

The scale factor was set to 1 Volt/mil, where as the probes used produce an output of 200mV/Mil signal.

Still unsure as to how this happened as it was working fine before, looking through previous run data and maintenance records.

 

Thanks for the feedback!