Hi, just wondered if anyone's using Rosemounts and could help us out a little here. We are running a huge, fairly new facility here and have started running into problems with this type of transmitter. I'm talking about the type where you have 2 pressure sensitive pads, arranged vertically one above the other. The liquid level is calculated by sensing the presure differential between the 2 pads. What we THINK we are seeing is that these transmitters are very sensitive to pressure fluctuations and whenever we have a compression trip ,( we have centrifugal compressors) the resulting pressure transients are causing spurious high and low level trips on the production trains. Any help would be appreciated.
2006-08-20 09:56:02 · 3 answers · asked by Not Ecky Boy 6 in Science & Mathematics ➔ Engineering
We have thought about introducing "damping" the ESD signal in the DCS, maybe a 10 second timer to stop spurious shutdowns . Would this be an appropriate response?
2006-08-20 10:00:32 · update #1
Unless the transmitter range you use is very small, it shouldn't be that sensitive. And at any rate, the pressure transient would affect both pads equally so the differential should remain the same. So you will have to put the time delay "damping" into the DCS. This last solution means that the response time to level changes would be longer, so you'd have to adjust your HH and LL limits accordingly. Also your limits may be set too tight at the tank is operating nearly at the limits. If its a sealed tank, depending on the liquid in it, the pressure transients MAY be affecting the levels and the trips are real level changes.
2006-08-20 10:23:38 · answer #1 · answered by LoneWolf 3 · 0⤊ 0⤋
I may be way off beam here and have no information on your process but could variations in foaming with the pressure fluctuations be causing your problems?
Edited comment: I see from the Rosemount site that this is unlikely to be a problem unless you have separate sensors for high and low level trip which are located both above normal operating level and both below normal operating level respectively.
2006-08-20 11:09:30 · answer #2 · answered by Robert A 5 · 0⤊ 0⤋
IF you do add a trip delay of, say, t seconds, make certain that the system can survive an over or under level condition for at least 2t seconds.
Doug
2006-08-20 11:08:14 · answer #3 · answered by doug_donaghue 7 · 0⤊ 0⤋