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Active Contributor

Join Date: Jul 2009
Location: india
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DVC Troubleshooting

03/25/2016 9:49 AM

DVC series have found when in Bypass mode have found supply pressure and positioner output fluctuating ,would like to know the troubleshoot and why does it occur.

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cajetan
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#1

Re: DVC troubleshooting -

03/25/2016 9:52 AM
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Active Contributor

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#2
In reply to #1

Re: DVC troubleshooting -

03/25/2016 9:58 AM

Digital valve controller 6000 series

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#3
In reply to #2

Re: DVC troubleshooting -

03/25/2016 9:59 AM

Talk to the supplier. They will want some actual information.

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#4

Re: DVC Troubleshooting

03/25/2016 8:23 PM

Historically, the term "bypass", when used with respect to valve positioners, referred to an optional pneumatic switch used on pneumatic positioners that switched a pneumatic 3-15psi/20-100kPa (or other ranged) control signal from the positioner's input directly to the positioner output, ie, the pneumatic actuator.

By using bypass mode, loop control (pneumatic control signal applied to the pneumatic actuator) is maintained while the positioner is taken out-of-service, albeit without the precision 'positioning' that a positioner offers. The rules for bypass use include direct action and 1:1 ratio of control input signal to the positioner's control output signal.

The DVC6000 is an electropneumatic 'smart' positioner. Its input signal is an electronic signal, not a pneumatic signal. An electronic signal cannot be used directly for control of an actuator/valve.

The DVC6000 manual dated 2013 from the Rosemount web site does not contain the word 'bypass'.

http://www.documentation.emersonprocess.com/groups/public/documents/instruction_manuals/d102794x012.pdf

So I do not understand your reference to bypass mode with a DVC6000, unless your 'system' includes bypass controls outside of, and in addition to, the DVC6000 (I/P/solenoid valve(s)/piping/control logic).

How is your 'bypass' implemented, how do you expect it to work and how does that vary from the results that you report?

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Active Contributor

Join Date: Jul 2009
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Posts: 15
#5
In reply to #4

Re: DVC Troubleshooting

03/26/2016 4:57 AM

Positioners that are used for Partial stroke test for ESDV ans SDV valves ,Normal operation the valves are in Bypass mode pr acting through solenoid to actuator and Automatic mode through Positioner when we have to do PST or stroke the valve in %, As we have the valve in Normal Operation i.e through SOV to Actuator and the Auto Mode not in operation we have found the DVC supply pressure and the Positioner output fluctuating ,would like to have an idea is the issue with the configuration setup or with the calibration.

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#6

Re: DVC Troubleshooting

03/26/2016 12:27 PM

When I solve these problems, I need a considerable amount of information to analyze
- P&ID's
- loop drawings
- hook-up drawings,
- exact as-found configurations
- process readings in both normal mode and alternative modes,
- control logic for the change-over between normal and alternative modes

It may be one configuration parameter needs a change, but who knows? There is no detailed information on what your system is, how it is piped, how the position is configured, what the control logic is, what normal operation conditions are and how alternate mode operation fails to meet your expectations. You haven't provided a single number or better yet, a series numbers, to show operational conditions. The fact that the air supply pressure 'drops' is does not say much.

I looked back through your posts. You've brought this topic up 3 or 4 times since 2009. And you've provided precious little information with which to analyze the situation.

I wish you luck in finding someone with the crystal ball who can see your process from half a world away and discern the situation, but I'll take a pass on further participation and exit. I am not up for a game of 20 questions.

Iris

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Join Date: Apr 2016
Posts: 6
#7

Re: DVC Troubleshooting

04/04/2016 6:08 AM

1)is this FCV ?and also confirm controller is cascade?

2) you have to check air supply and voltage supply correct or not?

3)you simulate through mA source and supply pressure and positioner output fluctuating.

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