Differential Pressure Transmitters

Few questions

From where is the tapping taken. Top of the pipe or bottom?

Does it happen everysingle time it crosses 86%.

Where have you seen zero in TX or in The HMI or PLC. Did you see what is the mA at 85% in the TX and what is it at 86%.

i belive the URV equal to 20 mA and configured correctly as 100% in HMI & PLC.

Please clarify.

86% of what? of 2,500? Do you mean that when the differential pressure reaches 2,150mmWC, the transmitter output goes to 0mA or 0mmWC?

With insufficient information, I'll have to make a guess. I think you may be be dealing with the "burnout" parameter ('don't know what yokogawa calls it). That's a parameter that some transmitters have to set the output at some value (usually either 0 or 100% - 4 or 20mA) when the measurement goes above a certain value. It's used for fail-safe purposes.

I usually see the burnout parameter with temperature transmitters but other transmitter types also have them.

regards,

Vulcan

HI Vulcan

I dont think thats likely because he's calibrating it full range, found ok. Also this happens everytime as per his explanation,. Could be the temp sensor in the Tx that could do this. Also from his explanation seems this Dp tx is for flow. so may be wrong config in the HMI or PLC also could create the problem.

But he needs to explain 86% of what first.

But he needs to explain 86% of what first

Which is why I said I'd make a guess. Also, it wasn't clear enough to me that he had calibrated it to full range. I interpreted his statement that when he reaches 86% applied pressure, the display suddenly goes to zero. That sounds very much like a burn-out parameter kicking in.

If he can come up with a more complete description, we can give a better answer.

regards,

Vulcan

Thank for interesting in my question.

first i calibrate dp transmitter with help of comarision tester. i check with apply 2100mmwc,2200mmwc and 2500mmwc pressure to transmitter. as per pressure output of mA are correct. dp give output upto110% (in display)

i fixed this transmitter with my orifice. i take orifce tapping 45 degree from top of taping and through condensate port.

we measure steam consumption through this flow meter.

it is working first class up to 85% of our calibration range. but when dp shows above 85.2% in display after then it is directly show "0". i check mA it is 3.97 mA.

thanks with regards

hitesh purani

What is the transmitter brand and model number?

Also, steam taps go to the side of the orifice flange, not 45° from the top. Do you have enough length in your impulse piping to prevent live steam from getting to your transmitter? You didn't mention how you connected it but just in case, I'm putting a drawing from Rosemount's 1151 manual.

regards,

Vulcan

Do the transmitter specifications allow the unit to be used with steam? Usually that is too hot for a pressure transmitter and it will act funny.

sir i used yokogawa EJA10 dp transmitter.

as per datasheet the temp range is 80 degree. we not apply steam directly.

we use condesate pot for steam application. temp range of steam is 135-145 deg. c.

thanks

hitesh

hi

I had many doubt how is the

1 orifice installation vertical or horizontal.

2 direction of orifice is with the impulse tapping ie inlet of orifice should be the hp tapp and with the direction of flow

3 condensate pots leveled equally or there any offset between them .

4 check for equalising valve fully close

this should solve your problem if not give the feedback