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Anonymous Poster #1

Dp Level Transmitter Calibration Under Vacuum Service

03/29/2012 2:48 AM

Hello every one,

We have a Multi Effect desalination package in NGL site. All Dp Level transmitter fail when package arrived to vacuum pressure. it means that fluctuation increase near -0.9barg (fluctuation depend on vacuum) . please describe cause and recommend reference or any comment that we can solve problem.

thanks

best regard
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PWSlack
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#1

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 3:08 AM

The fluctuation is as a result of the contents boiling. Either choose another level measurement technique, like radar, or slug the signal(s) with (a) low-pass filter(s).

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PWSlack
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#2
In reply to #1

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 3:36 AM

More thoughts: RF admittance would also work. It may be worth adding low-pass filters to any measurement technique.

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m.shahryari
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#4
In reply to #1

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 9:42 AM

Hi Dear.

thanks you that inform me but I think water in LP & HP legs don't didn't boiling because of boiling point chart (0.54 bara ~ 70 C) . temperature in effect 4 is about 50 C and impossible boiling. now please tell me about calibration of Dp level transmitter if we can't change to radar technology.

thanks
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PWSlack
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#5
In reply to #4

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 10:07 AM

That information doesn't correspond to Anonymous Poster #1's statement: <...near -0.9barg...>.

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ChaoticIntellect
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#6
In reply to #4

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 10:31 AM

I found it oddly coincidental that your problem occurs at -0.9bar (as stated in the original post) and the temperature of the process (as just described) is 50C which just happens to be the boiling point of water.

The fluctuation is due to flashing as stated earlier.

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PWSlack
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#7
In reply to #4

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 10:59 AM

Oh, and another thing. If it's an evaporator, how come the contents are supposedly not boiling?

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m.shahryari
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#8
In reply to #7

Re: Dp Level transmitter calibration under vacuum service

03/30/2012 5:40 AM

please review H&M balance of desalination package. so I checked again that fluctuation almost start after achieved to pressure -300mbarg and proportional by increasing vacuum. these LT install in effect 4 , 2 in brine side & the others in product side.

.
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PWSlack
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#3

Re: Dp Level transmitter calibration under vacuum service

03/29/2012 3:57 AM

During the next process design review, consider ways of making level control unneccessary for any following installations.

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