Yokogawa EJA430A pressure transmitter
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According to the operator, the measured pressure is too low. However, after draining waste and restarting the system, the pressure level remains unchanged. I would like to ask the experts: what could be the reasons for such a low measured pressure, given that the substance inside is hot water?
This post was last edited by qugd on 2020-7-8 09:30. Transmitters of this model are estimated to be around 20 years old; since they are original, the manufacturers that supplied them must have been large companies from earlier times. If the detected pressure is too low, it indicates that the pressure-sensitive diaphragm box has not detected the deformation of the measuring element caused by pressure; or perhaps it is actually damaged and unable to produce sufficient deformation. It’s been in use for so many years; replacing it with a new pressure transmitter isn’t costly at all.
By how much is it lower? Is there a pressure gauge nearby for comparison? Remove it to check for blockages; there’s no need to rush the verification – just install a pressure gauge to compare the pressures.
Check the zero point and range of the gauge; if everything is fine, inspect the pressure lead pipes and condenser tank (if present). If those are also in order, replace the transmitter with a new one or install a pressure gauge to check the reading.
This is most likely due to the deterioration of the silicone oil, caused by heat or penetration through the diaphragm box
Check the zero point and see if there is any blockage in the pressure transfer tube. If standard calibration equipment is available, use it to check whether water rust has blocked the pressure transfer tube or accumulated on the diaphragm box. Check whether the DCS range matches the field range
Change the table; it’s the fastest and most direct way. It’s also the most intuitive. It can be downgraded for use in less critical locations
Something this old is probably already out of production