Determining Valve Position without Position transmitter

[charzree]

Hello All,

How can I calculate the valve position without position transmitter in PLC? all I have is open and close feedback signals and I know the time taken for the complete opening and closing operations.

 

[tragically1969]

Hello All,

How can I calculate the valve position without position transmitter in PLC? all I have is open and close feedback signals and I know the time taken for the complete opening and closing operations.

Have you not answered your own question ?

I would run something like an up/down counter/timer against the open and close commands and work it out from that ?

 

[Mickey]

Is this analog controlled? If so you could use the analog output to provide you with the position. If the valve follows the output, testing this would tell you. But that could change with time ( wear and tear).

 

[geniusintraining]

You can install one of these and run it back to the PLC?, you would just install a flag on the arm of the positioner and use the sensor to let you know where it is in the stroke

http://www.bannerengineering.com/en.../Analog-Output/231/U-GAGE-S18U-Series—Analog/

 

[Tom Jenkins]

Do you need to know valve position other than when it hits max or min open? Or do you really need to know a process variable, such as flow?

I have hundreds of valves on systems controlling flow without valve position feedback. I used to just use limit switches at max (usually set to about 70%) and min (usually set to about 15%). I would simply tweak the valve until I got the flow I wanted. When the limit switch tripped I knew I was out of adjustment and had to do something else.

Tracking time is unlikely to be satisfactory. The gearing in the operator usually has clearances, so every time you move there will be some error. When reversing direction the error is greater. At some point the errors will accumulate enough to make your "position' useless.