I have a problem in calibration of pneumatic valves with using Hart communicators.
Please advice me with a good procedure.

 

You shouldn't need to use a HART communicator. A mA source is what you need. Start the stroke at about 4.5 mA and it should be fully open at 20 mA.

This assumes the valve is N/C and not split range.

Roy

 

I know, but if I need to program the control valve to be full open when it reaches to 60% of the full stroke mechanically, So what to do on the valve it self. And another problem, when the control valve is not at 50% openning when giving 12mA to it, what to do?

Please advice.

Amer

 

If I was in your position, First thing I would do is located the manual for the control valve you are working on and read it. It should provide some information on the adjustments if needed

 

Amer,

Sometimes the control valve positioner is not linear travel wise i.e. 50% signal doesn't give 50% travel, you need to read the manual as Mike pointed out.

There are too many different types of valves for us to give you a comprehensive answer.

 

What is the exact problem?

What aspect of the positioner are you trying to calibrate?

- input (setpoint) current trim?

- position feedback sensor trim (valve stroking to find open and closed positions)?

- position feedback current trim?

There is a white paper on calibration of HART transmitters here:
http://www.eddl.org/DeviceManagement/Pages/Calibration.aspx

Are you able to communicate with the positioner?

Cheers,
Jonas

 

Thanks for all.

The positioner is linear which means that the roller shall be vertical with the stem when the valve is at 50% opening (12mA).
I have HART 375. I don't have a separate mA injector. I have two questions:

1- Is there any special thing that I have to do when connecting the HART with the Control Valve which is Smart type by the way?

2- What to do if the valve is not at 50% when injecting of 12mA by the HART.and what to do if I need to make the full open at the 75% of the stroke. I think that I have to adjust the stroke mechanically. Please to Advice.

 

Thanks for all.

 

Amer,

Please, Can you tell us the positioner model, brand, type?

same information about the control valve

Regards
J.Pinzon

 

> 1- Is there any special thing that I have to do when connecting the HART with the Control Valve which is Smart type by the way? <

No, I don't know of anything special, just wire it up as you would a smart transmitter

> 2- What to do if the valve is not at 50% when injecting of 12mA by the HART.and what to do if I need to make the full open at the 75% of the stroke. I think that I have to adjust the stroke mechanically. <

Yes adjust the linkage to give you the right opening. If it's only a few % off at 50% don't worry about it, the PID will take care of that.
Linear doesn't always mean linear travel 50% might mean 50% open. The valve trim has it's own characteristics.
Hope this helps.

If you want to make a simple cheap 4-20 mA calibrator drop me an e-mail roy_matson at yahoo dot ca

Regards
Roy

 

All HART positioners have an auto-calibration function (I don't know any that don't) This is one of the best features of "smart" positioners. Other features like split-ranging, reverse acting and setting stroke limits "should" be able to be accomplished by either the Hart software or directly at the positioner. Some positioners (like the Samson 3730-3) have a rotary push-button on the inside cover that allows you to set all these features. Try checking in your IOM for your positioner or download one from the supplier. This positioner MUST be able to do what you are asking. You may have to re-initialize the positioner again by doing a cold-start to get it back to default settings.