Position Transmitter

hi john

what we are having is a limit switches for open amd close indication

and there no feedback confirmation signal in dvc 6010 as it is only receiving signal

4 to 20 ma only .

Hi there,

Without an actual transmitter giving you the position feedback - it is impossible to get the real valve position.

The smart positioner will tell you where it thinks the valve is, but this might not actually correspond with what is happening in the field.

Regards,

Craig

It is unusual to require valve position feedback in 3-term control loop applications. Usually the measured variable is some process parameter, not the valve position. If only the valve position is available, then some correlation between the valve position and the process parameter is required, which often isn't available.

The valve position will strongly correlate with the 3-term controller's output signal. Could that be used instead?

Hi

I do not agree with earlier comments. There are a few smart positioner which give correct feedback.

DVC is a good example. I have installed all positioner as these in couple of plants only few feedbacks have been taken though and they show correct value.

Valtek positioner with magnetic feedback also gives good feedback and i use this very effectively in turbine applications to control the nozzle. I have added some logic in the processor if there is a difference btw Input to positioner and feedback more than a certain value.

Naveen

how to do the calibration

Hi,

If you are using DVC6000 Series or DVC2000 the calibration is very simple and straight forward.

TSE

Hi Naveen,

I do not agree with you there.

The position feedback arm is for the positioner itself to function.

If you want to be 100% certain of the actual valve position you will need a position transmitter. The positioner calibration might be out - and then that feedback arm is useless. The same would apply to valve stroke etc.

Regards,

Craig

Hi Craig

Understand what you are pointing out at.. One of the positioner i use for feedback aswell. This uses a magnetic feedback system.

http://www.westlockuk.com/assets/downloads/Westlock_IOM_TECHUK-20_ATEX_ICoT_5000.pdf

Yes this guides the positioner absolutely True. The position is fed into the Microprocessor of the Positioner. when we do the setting we set the full travel then the 100% 95-100% 0 % 5-0%. and these positions are fed to the positioner. So except these value are changed or wrongly fed no problems with respect to the feedback as such, In event that the positioner is failed or the microprocessor memory gets failed yes, then you will not know where the valve is.

But then wont that happen if the fuse in the input line or the wire disconnection happen.

Naveen

hi john

try with LVDT www.transtekinc.com generally they are used in hydraulic actuators

I have seen some controlvalve in waste heat recovery system having LVDT as feedback positon

regards

Adil

Hi

LVDT will help., yes but only in case of linear displacement. also saperate controller will be required in most cases

Yamatake has a line of smart positioners that provide a 4 to 20mA position feedback to the PLC or other. The positioner, therefore, has two cables going in and out of it. One is the position command signal and the other is the position feedback.

Specific model is the AVP-301.

regards,

Vulcan

Hi John,

Actually DVC6010 (Sliding Stem Application) providing the features of information, such as: supply pressure, output pressure and travel target. Through the hart communication, we can take this information by using Tri-Loop (HART to Analog Signal Converter) from Rosemount.

So you will get analog output information about the travel/feedback of your valve. Beside that of simplicity in the wiring. Tri-loop is very usefull for application using mulivariable transmitter. All the information for this Transmitter (D/P, temperature and gauge pressure) can be convert from digital HART signal into three additional analog signals.

Hope this usefull for you,

Regards

Golf Alfa

Hi,

1. Yes, it is possible for fieldbus positioner like DVC6000f series. For HART Protocol you can consider DVC2000 with options (built-in position transmitter and two Limit switches).

2. Yes, it is also reliable and accurate.

TSE