Bently Nevada Vibration sensor with DCS issue

Hello,
We have an issue with our vibration sensor from bentlly nevada 4-20 ma is connecting directlly to DCS
The reading spikes and not stable
And over scale
We replace many new sensors and same problem.
The stange there are another unit working good in same DCS input card
Please advise us.
We consumed all spare parts in this problem.
 
Talal9001,

How long has this problem existed? Did it start after a maintenance outage? Or did it just begin suddenly?

Have you verified the cabling and the shield wire for the cabling for the sensor in question is correct and the same as the other working input? Including no loose terminal screws or crimp-0n terminal lugs?

Have you tried using a 4-20 mA simulator on the input, at the DCS, and in the field, to see what happens with a stable input?

I presume the B-N vibration sensor is a proximity probe. Have you verified the gap?

Have you tried exchanging the two input signals at the DCS input card? If the problem follows the sensor to the previously working DCS input card then it's either the sensor wiring or the "sensor." If the good sensor is now reading bad on the bad DCS input the problem is the DCS input card.

If you provide the B-N sensor type and configuration, we might be able to provide more help. For example, is the B-N sensor (proximity probe; proximitor) output connected directly to the DCS input card, or does it come from a buffered output from a B-N monitor rack?
 
Talal9001,

Would you please supply a B-N Part Number?

What about the wiring? Have you checked the shield drain wires of the good and the bad input circuits (from the sensors) to see if they are earthed properly (at one end only)?

Are the cables from the sensors routed in cable trays or conduits or cable vaults with other low-level signal wiring, or with higher-level (120-240 VAC or higher; 10 A or higher) signals?

Have you checked all the terminations all along the circuit of the intermittent sensor for loose crimp-on terminals, or loose terminal screws?

Have you, or can you, run a temporary cable from the DCS input card to the sensor having the problem to see if it's the cable or the sensor?

And, again--exchanging (swapping) inputs to the DCS input card would help a lot in determining if the problem is with the sensor/wiring or the DCS input card...!

Please write back when you can provide the answers to these questions, and update us on the progress you make in resolving this issue.
 
We used BN model 177230-01-01-05
WE checked the input card and connect the sensors direct to marsheling cabinets in DCS
Obsered the reading is stable without any spikes.
After that tried to connect again BN in field but same problem the reading not stable we replaced 4 new sensors and sam issue.

Then i try to Fix anothe model from Vibro meter we have , we suprise the reading was stable and perfect , we keep it for two days for observation.

So, BN Sensors 4-20ma not ideal products for monitoring the vibration of Pumps
We have alot of notes regarding BN.
And this is not first time we faced this problem.
 
Talal9001,

Without researching the part number, my first reaction is: We still don't have enough information to be of much help.

We don't know if the two B-N Sensors are mounted on the same piece of equipment running at the same speed, or two different machines running at the same or different speeds. We don't know the mass (inertia) of the equipment(s). There's just a lot we don't know.

We've tried suggesting some possible tests (swapping inputs), but you don't seem interested in doing any more swapping (even though this one is just a few wires).

VERY often when I encounter problems like this I am reminded of my first combined cycle plant assignment where there was a large, medium voltage AC induction motor driving a reciprocating natural gas compressor. The motor kept experiencing rotor issues, and the motor manufacturer was on site about every week trying to balance the motor or take all sorts of measurements and data to try to understand why this particular motor was having so many problems.

It took about a year after commissioning (don't ask why I was still on site more than a year after commissioning!!!) but it finally came out that the plant designer had ordered this motor from a supplier and mated it up with the compressor for the application. (This came out because some funny things had been discovered with regard to the coupling and footings of the two pieces of equipment, after having removed everything from the foundations during the first major plant outage after commissioning.) It turns out the motor was NOT designed for driving a reciprocating compressor, but for centrifugal pump applications (water). The motor for a reciprocating compressor drive would have cost about 40% more than this motor, and because the design firm had not asked for assistance from the vendor or motor manufacturers in choosing a motor and had simply based their selection on price, alone, the wrong motor had been sourced and coupled to the reciprocating compressor.

The motor manufacturer had spent SO MUCH money at this point troubleshooting the problems they provided the correct rotor for the application, assisted with correcting the mounting problems (working with the compressor manufacturer and the coupling manufacturer)--and, voila! All the problems and unreliability of the gas compressor went away. (Actually, that's not really true because the intercooler of the compressor AND the bypass valve were undersized and the compressor manufacturer was NOT going to provide the necessary components free of charge and the design firm/contractor refused to buy them--the Customer finally did so about 2-1/2 years later. (Yes; I was STILL getting called out to that plant almost three years after commissioning.)

Why do I tell this story? Because, the application where sensors are installed is very critical to the choice of sensors. Some sensors are simply NOT suited for any and every application. Working with the sensor manufacturer when problems like this arise, giving them all of the pertinent information, and in some cases asking the right questions, will usually reveal some small piece of information or specification that explains why the sensor was unreliable. I have seen it time and time and time again. Control valves; actuators; transmitters--just about everything you can imagine--has to be properly selected for the application.

So, based on the information provided, it would seem that there is something more to this story than has been provided. AND, if you work with the sensor manufacturer(s) you will, eventually, probably discover that the sensor which is giving you problems is not suited for the piece of equipment it is mounted on. It might be temperature; it be speed; it might be location; it might be one of any number of parameters--even a combination of more than one--that's preventing the B-N sensor from working properly.

I would suggest trying to get ALL of the specifications for the B-N sensor and the Vibro-meter sensor and comparing them closely to see if there's any differences that might explain why you are having problems. A GOOD B-N vendor (perhaps Baker-Hughes?) should be able to help with analyzing the application to determine if the installed sensor is right for the application.

It surprises a LOT of people in parts of the world that are relatively new to the industrial revolution that they can get FREE assistance from manufacturer's representatives and/or manufacturers when trying source equipment. They just seem to refuse to believe that salespeople and application engineers would freely give their knowledge and assistant--to try to help sell the CORRECT piece of equipment. AND, they simply refuse to believe that salespeople and application engineers would freely try to help solve a particularly vexing problem with some piece of equipment. But, they do and they will. Some companies and individuals are better than others when it comes to providing help, and a lot of that has to do with experience and knowledge. But, in general, vendors WANT to establish relationships with users/consumers to sell MORE equipment and sensors, and the good companies KNOW that they way to do that is help when asked, and that when new equipment or spares are required they will most likely get the P.O. (Purchase Order) for new equipment.

When you're stuck--try involving the manufacturer or the manufacturer's representative. Or, go to a competitor for similar help.

Best of luck. Just be prepared to provide information when requested. And I think you'll be very pleased (maybe not the first time, but eventually. This is how one finds good suppliers and providers.)
 
I do not make any swapping in input card
Because there are trip signals for another unit in same card all are workin good.
I connect the sensors direct to input card and are working properly.
But when again connect in field same problem happen.
Both sensors are connected in same equipment inboard and outboard motor of High pressure pumps for RO unit.

Both BN and Vibro meter in same of specification and range.

For BN senosr , this is not first time faced the problem , this problem happen in diffrent unit 3 years ago and contact the vendor to analyze the problem, they do not help untill charge the service and failed to solve the problem . Each time said the problem not from sensors and keep the unit in Bypass without protection.
As in that time we had a project in diffrent unit to upgrade Vibration system from another company, we request them to support us in this issue, they advise to use them sensor insteated of BN sensor
They supplied and install the senosrs and arw workiing properly without any problem.
That past story, for BN Vibration sensor.
Now we have two diffrent models for BN swnsor. We are planning to replace all sensors in future.
Thanks all,,,,
 
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