i have pressure transmitter Yokogawa EJX ser. with capilary and diaphram seal. i know that it cant be calibrated in the lab so how i can calibrate this type at the field. specially there is no input for the pressure because the diaphram conected direct to the falnage

 

Yes you can calibrate it in the lab but you may get a zero shift when you install it.

Try to calibrate it with the seal and transmitter at the same Zlevation difference it will see in the field. Once it's installed re-check and correct the zero.

 

We are talking about "Clever Transmitters" that means if by diagnostics (Hart, Brain, etc) not problem reported. then the only source of problems my be due only by capilars, flange fittings and so on.

put both flanges on the table, put the transmiter on the floor. with insulation tape, join both capilars as close as possible within them and apply heat by an hot air blower. record the changes (In theory must 0)

one quick test is to make an span of about +-1500 mmh20. put one flange on the floor and another on the table and reverse, and check for simetrical desviation. but the best of all is to use a pot with two flange adapters placed at the same heigth, and apply and remove pressure in the pot (About 5 Bar). record the deviations and see if there are aceptable. Check also for leakages.

If everything is O.K, then the transmiter may work propertly on the field.

regards:
[email protected]

 

A good reason to avoid diaphragm seals, too much trouble, too often damaged.
Roy

 

You have to create an adapter to connect to the diaphragm.

They can easily be calibrated in a lab as long as you use the precautions above. You must set the diaphragms at the same height above the transmitter they are mounted in the field (where the capillaries are mounted to the transmitter.

For example. If one side is 1 meter above the transmitter, and the other side is 4 meters above the transmitter, they must be positioned the same way in the lab. There is a way to simulate this when one side is mounted very high, but I'll only go into that if you need it.

As far as heating the sensors- no need to if all you want is an initial calibration. All heating the diaphragms does is tell you what the temperature effect on the seals are and the manufacturere will give you those numbers. If they heat equally on a DP transmitter, you won't see a change in reading anyway unless there is a fill problem in a capillary or a damaged/warped diaphragm.

As for the comment about them being a pain. There are many cases where <b>you have to use them</b>, especially in the pharmaceutical industry, so if you don't have a constructive comment, don't reply.

 

"As for the comment about them being a pain. There are many cases where <b>you have to use them</b>, especially in the pharmaceutical industry, so if you don't have a constructive comment, don't reply"

If you look back a couple of posts I did have some constructive advice.

Your instructions on how to calibrate have done nothing to change my view of capillary systems. <b>"Avoid them if you can"</b>
Regards
Roy