Control valve with fisher DVC6020F positioner cannot move occasionally

[fjh502]

In our plant we use delV control system, some control valve with fisher DVC6020F can move by DCS, but occasionally these valve cannot move by DCS, after re-wiring(only disconnect then connect wire in valve terminal box) then it can move by DCS again, i want to know the root cause, anybody can tell me? Thanks a lot!

 

[itsmoked]

That's nasty!

Is this just one particular valve or more than one?

Are these small change commands or any change?

How far is this valve from the generated control signal?

What kind of facility is this, equipment density, electrical noise wise?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[fjh502]

First thanks Keith cress for your quick response!
for your question i answer here one by one
1.there are about 5-10 valves fault with this phenomenon.
2.Valve could not move regardless control signal change.
3.The distance is about 100 feets, but the valves which is far than 300 feets distance has no this phenomenon
4.The valves in the same enviroment has no this phenomenon.

i don't know my answer is clear or not, any more questions pls let me know. Thanks again!

 

[danw2]

Have the valves ever worked properly?

Exactly what is the control signal, 4-20mA or HART?

 

[controlnovice]

The DeltaV has some good diagnostics.

Start by investigating the control modules. Any block that has a question mark on it has something wrong with it.

Also, DeltaV has a diagnostics tool that will help determin what the actual output is. This may help.

Also, if it is HART, Profibus or Foundation Fieldbus, you may be able to check it our with AMS, if you have it. If you don't have AMS (an Emerson product very handy with DeltaV), use a handheld communicator for HART or Fieldbus.

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[fjh502]

thans all of you, For the valve i have mentioned work well in most time, and control signal are foundation fieldbus.
when fault occured, we have diagnose them with delV and AMS, We could not see any alarm but deviation alarm (between controller output and valve travel sensor feedback), this is what i wonder.

 

[itsmoked]

Could you have a case where the linkage is loose or maladjusted and the deviation alarm is "halting" further commands? The alarm is then cleared via the on/off power reset.

You could maybe duplicate this error by disconnecting the linkage momentarily.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[danw2]

If I understand the situation, it sounds like the valves have 'smart' positioners, with a Foundation Fieldbus control signal.

Are these positioners all of the same make and model and firmware version?

Are the 'problem' positioners all on the same FF communications link?

Further, several positioners periodically, but at the same time, fail to respond to a DCS position command. Correct?

Further, by disconnecting a positioner control wire in a field junction box and then reconnecting the wire, a valve positioner can be forced back into proper operation. Does disconnecting/reconnecting the wire solve the problem for more than one positioner at once? Like all the positioners on the comm link?

Would you agree with these restatements of your situation?

What brand and model positioners?

Dan

 

[fjh502]

you are right, the vlaves are digital valves with DVC6000 series controller and controlled by foundation fieldbus signal, these controller are hooked different segment,(communication through different communication card) and fail to respond to a DCS position command not at the same time.these failure valve can be reset disconecting/reconnecting the wire.I have checked whole loop and found no loose terminal.

 

[noshorts]

Maybe you should check your instrument air. Lack of signal when disconecting the wires (depending on the failure state of the valve) may allow enough pressure to build up to actuate the valve again.

 

[fjh502]

The IA pressure is enough and I/p is ok, I only suspect delV system.

 

[glowing]

What process is the valve controlling? Is it a simple loop, or are there stings of function blocks? Do all of the valves not respond properly at the same time, or is it a random thing?

 

[controlnovice]

We had a similar issue with a few DVC positioners. We installed new DVCs on existing valves. We kept of getting errors between output and actual position.

We found that the linkage attached to the stem of the valve was rubbing against the positioner cover. It ended up being a physical/mechanical issue, and not an issue with the DVC or communication. We found that there were different positioner covers also, and we were sent the wrong ones!

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[fjh502]

Thanks you all
Here i want to explain that:
first this thing only happen random and on specific valves which are hook on different segments. we have checked all hardware installation no problem.some valve are simple loop contrller output, some are a little complex but often use.I think it's no relationship about how complex the loop is since valve only execute the controller output.

Welcome your advice.
Thanks again.

 

[controlnovice]

Since this is Fieldbus:

Have you investigated the milliamp on each segment. I think they limit is 80mA or 120mA. If you are drawing to many mA, it will affect the overall signal quality.

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[glowing]

I have seen the same as controlnovice.

Also, if these DVCs are add ons, perhaps the wrong mounting kits were used. Many look the same.