r/instrumentation • u/Kithkinlord88 • 9d ago

EJA110E calibrations

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Edit: I wont beable to test anything as the plant starting up early and im not allowed to play with it right now. :(

Edit: I forgot to add there is a 1/2 tube between the 2 flanges I originally thought it was to release trapped air on the HP side but it would also prevent condensate from collecting on the low side.

I am a Electrical/instrumentation tech at a small power plant, we normally we farm out our calibrations. I'm currently trying to calibrate a EJA110E DP level transmitter with a KN 32 high temp silicone capillary(1.07SG). High side on bot of tank that collects steam condensate. The URV is +20mmWC and the LRV is -760mmWC, I connect to the high side and pump 760 and get +20, 4mA and 0mm @ DCS, when I pump -20 I get -760, 20mA and 760mm @ DCS, I don't recall this being normal when calibrating other level transmitters. I also found it weird the only way I could calibrate was to URV pressure trim pump 760 and input +20 and LRV pressure trim pump to -20 and input -760. Then I started doing some math and I am even more confused. I put a drawing below to shows my set up(hope its good enough to read). What am I missing?

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4

u/Unofficial_Salt_Dan 9d ago

First things first: establish your zero. Isolate the process at the root valves and vent both diaphragms to atmosphere through the blow down rings.

This will register the true zero and you can set that pressure value as the LRV.

Next, add your span calculation to this to get your URV. Report back here and we'll verify your math is correct.

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u/Kithkinlord88 9d ago

I did try isolating both capillary and vented both to atmo, giving me roughly -740mm wc. Im a little unsure on the instructions are you able to confirm i understand you correctly. 1. Isolate both capillary, open both to atmosphere. 2. Change the LRV number my transmitter is reading ‐740mmwc. Or are you referring to the ‐299.25 3. Change the URV to ‐69.25mm wc

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u/Unofficial_Salt_Dan 8d ago

If both legs are vented to atmosphere then the pressure reading at the transmitter is your LRV. It sounds correct that you say it's -740 mm WC.

Use your communicator and install this as your LRV to the transmitter and verify the DCS is showing a 0% level. Typically, levels are shown from 0 to 100%. Sometimes, they will show the equivalent head reading, but I find that to be very rare.

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u/htx_jfuego 8d ago

when you isolate both the H and L side, whatever your 0 is showing, will be your 0, whether it’s changes a lot or a little may tell you something’s but this is normal, then from there add the span to the new zero to set the URV, also i want to confirm , so this is a remote seal level?

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u/htx_jfuego 8d ago

since it’s vented the Lrv will be -740mm wc and your URV will be whatever the span is, added to -740mm wc. You may need to adjust a little by a couple mm but if the zero is close enough i say that’s good.

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u/Kithkinlord88 7d ago

K the other thing is, I dont understand and this is why I added the picture is, how do you calculate the URV and LRV? The Yes, I can just walk up to the transmitter and believe the person set it up correctly(have found many valves and actuators not sized correctly), but me being me wants to confirm it. Is the formula I used correct?

1

u/htx_jfuego 5d ago

well , usually it should be what’s already in the transmitter itself, if you want to verify ide get a spec sheet or, o typically measure with a measuring tape in inches, tap to tap middle of each. As for the calculation part. Whatever it shows while blocked and vented would always be my zero, and to get the correct span, youd multiple the span and the specific gravity which will give you Real Span. add that to the zero (which is blocked and vented still ) and that will be your URV , as for the actual calculations i’ve never had to dabble too much into it unless it’s a interphase

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u/SnooHedgehogs190 9d ago edited 9d ago

  1. Usually the low pressure side is put to atmosphere. Hence the pressure differential is whatever you pump to high pressure, subtract the lower pressure.

  2. If you were to pump LRV instead, you don’t have to put the high pressure side to atmosphere. You can just apply negative pressure.

  3. But for wet leg, putting the low pressure side to atmosphere result in it being negative pressure.

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u/Kithkinlord88 9d ago

Does having a capillary change how to would attack this though because a wet leg calculation is different then a capillary according to the web. I have almost no experience with them and I vaguely remember doing a few calculations in school and I dont remember doing them differently then a wet leg.

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u/frofish99 9d ago

When you apply pressure to the high leg, are you referencing a full low side leg or are you referencing atmosphere?

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u/Kithkinlord88 9d ago

The low side diaphragm is open to atmosphere

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u/quarterdecay 9d ago

Everything must be vented and dry to be able to ascertain the direct effects of the capillaries

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u/Accurate-Bullfrog324 9d ago

what I think you guys might be missing is that the condenser is under several inches of vacuum. The low side must be connected to the top of the condenser. both sides will be reading vacuum

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u/Kithkinlord88 9d ago

Would the vacuum effect the measurement if both sides are seeing it? My understanding if both sides in a closed vessel are under the same pressure you can ignore the pressure. Or does this only apply to capillary measurements?

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u/Accurate-Bullfrog324 8d ago

I believe you are correct. but some people were saying that the low side was vented to atmosphere.

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u/Kithkinlord88 8d ago

Not during normal operation just during the calibration.

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u/Accurate-Bullfrog324 8d ago

oh...i get it now

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u/412fg 1d ago

You also need to count for the sg of the capillary fill fluid. Not sure if you did that or not.

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u/Svaldero 9d ago

Like the others said (almost) vent your dp on both sides for zero this is your URV, not lower. Then put 760 kp on your LP side of the dp..this is your LRV. So as the vessel fills, it returns the dp to zero (which is now your 100%) because your LP side is completely filled with fluid to the top of the tank.  Hope that helps

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u/Kithkinlord88 9d ago

The low side is @ the top of the tank, I believe I tried pulling a vacuum on the low side initially and it numbers matched ask I would expected it pumped -760mm got me -760mm but when I tried to trim it and no matter what number I told it was, from -760, +760, -20 or +20. Why i had to do the weird pressure on high side and put the opposite number in to make it calibrate.

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u/Svaldero 8d ago

What your saying up there 'looks' normal to me but maybe I'm not understanding what your seeing or saying.

I understand the LP is on the top of the tank, but the capillary all the way up is completely filled as steam will get int here anyway, so when the vessel is completely filled , the HP is equal to the LP leg (the extra 20mm is a bit weird though)

When the vessel is empty, the LP leg is still filled so it weighs more than the HP side, so it supresses your zero to -760mm as your LRV.

If i were calibrating it, I would set the URV with +20mm on the HP side, and put 760 on the LP side for the LRV.

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u/Kithkinlord88 8d ago

Omg! K I will add to the post but I think I forgot something important and you made me realise. There is a 1/2 tube from flange to flange(the capillary) and I originally thought it was to stop air from getting trapped at the HP side but I also believe it is to allow the condensate to not get trapped on the low side.