Deaerator Level Measurement
Deaerator Level Measurement
(OP)
Hi there,
We have a spray type deaerator in our boiler house.
The existing level measurement on this deaerator is Through a DP cell.
it has been found that slight pressure fluctuations in the top deaerator scrubber drum(i.e. a jump in steam pressure for only few psig), have had a huge impact on level in storage drum(70 to 90%).
Any idea what is happening? for me it does not make sense. the pressure jump should be sensed by both high and low press. connections and should not affect the level measurement unreasonably.
if we have to change the type of level measuremnt, what would be the best choice?
A guided wave radar or a displacer type?
Any kindly advice/exerience would be highly appreciated.
these are the process data:
Vessel Height 12 feet
Units Min Operating Max
Temperature OF 262 298 298
Pressure psig 22 50 50
Liquid heights are measured from the bottom of the vessel.
Regards,
We have a spray type deaerator in our boiler house.
The existing level measurement on this deaerator is Through a DP cell.
it has been found that slight pressure fluctuations in the top deaerator scrubber drum(i.e. a jump in steam pressure for only few psig), have had a huge impact on level in storage drum(70 to 90%).
Any idea what is happening? for me it does not make sense. the pressure jump should be sensed by both high and low press. connections and should not affect the level measurement unreasonably.
if we have to change the type of level measuremnt, what would be the best choice?
A guided wave radar or a displacer type?
Any kindly advice/exerience would be highly appreciated.
these are the process data:
Vessel Height 12 feet
Units Min Operating Max
Temperature OF 262 298 298
Pressure psig 22 50 50
Liquid heights are measured from the bottom of the vessel.
Regards,





RE: Deaerator Level Measurement
Is your signal bouncing and settling back to the correct reading, or permanently off?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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RE: Deaerator Level Measurement
I am not quite sure, since operations are insisting on replacement I did not ask more questions.
The only thing that I can think of is the tapping points of either high or low (or maybe both) might have blockage or something like that, although there are a lot of bends in tubing too.
Anyway my concern right now is type of instrument for replacement. I was considering displacer type, but the maintenance do not want a 9 ft. displacer type and instead asking for guided wave radar.
What do you guys think?
Thanks in advance
RE: Deaerator Level Measurement
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Deaerator Level Measurement
Any experience with same type of service?
Thanks in advance.
Regards,
RE: Deaerator Level Measurement
I do mostly storage tanks. And, we don't bubble.
In most tanks, the maximum fill level is usually not 100% of the tank capacity. Hence, even with the bubbling, in as long as it is not a large percentage of the total level, it may be okay, depending on accuracy.
I am assuming that your bubbling zone is more or less constant. If so, then it is pretty much just a bias of the signal. If it is variable, then you need to do a bit more work, perhaps vary the bias depending on current level?
Most likely, you need to stay within a range of levels (between the upper and lower operating ranges). If this is the case, the bubbling effect on radar should be negligible.
Also, I have been told that radar is actually fairly good at "looking through" vapor and dust. It is dependent more on density changes to reflect the wave back up. So, I guess if it is just water bubbles, then it should not be too much of an issue? Maybe talk to the radar vendor and see what they say about the application.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Deaerator Level Measurement
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RE: Deaerator Level Measurement
The upper connection should slope upward from the aerator to a datum chamber (condensate pot) . Connection must be above max water level. The datum chamber will continuously fill with condensate and hold a constant level. Excess condensate will follow the slope and dribble back to the DA. Measure the differential from the datum chamber to the connection near the bottom of the DA. Small differential: High level. Large differential: Low level.
RE: Deaerator Level Measurement
RE: Deaerator Level Measurement
I might have suggested the dp transmitter if you had no problems with the existing installation. DP transmitters are affected by density changes - including the temperature changes and the affects of flashing. Could the existing transmitter impulse line be connected to point where a valve is occasionally opened? The flow would knock the dp for a loop.
Capacitance might work well in this application too.
RE: Deaerator Level Measurement
RE: Deaerator Level Measurement
RE: Deaerator Level Measurement
RE: Deaerator Level Measurement
Use two pressure transmitters and subtract the two values to get the level, thats exactly what all new Dp transmitters do. The LP transmitter can be placed above the tap point so the leg will not fill with water.
RE: Deaerator Level Measurement
RE: Deaerator Level Measurement
Level measurements based on DP are affected by liquid density which in varies with the process Temperature and Pressure. Hence suitable corrections are to be made to the DP transmitter output.
R.Thiyagarajan.
t
RE: Deaerator Level Measurement
Did you try looking into a magneto restrictive float type. Basically the same principle as the displacer however you do not have the torque tube mechanics to deal with. The only problems we have had have been at extreme cold ambient temp (-40 deg) and in start-up conditions (no process heat), but who works when it is that cold.
Check out www.ktekcorp.com or www.isemagtech.com we have hundreds of k-teks in our plant and they work well and the cost would be in the ball park of 5000 (CAD)
RE: Deaerator Level Measurement
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RE: Deaerator Level Measurement
I agree with you that the pressure should be equal on both legs, therefore there is a restriction in one of the legs. Have the maintenance people ream out the tubing.
Hacksaw has a good point about the process surges. Try slowing down the rate that the spray operates.
Steve
RE: Deaerator Level Measurement
How did you get on have same problem. Due to leg of DP constantly blocking up and was thinking of Guided radar but feel the turbulence may be to great.Is there any reason why a 1:1 pressure repeater cannot be used to eliminate condensate and blocking up of LP side.