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Topic Title: Orifice Plate/ DP cell issues
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Created On: 29 September 2008 03:10 PM
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 29 September 2008 03:10 PM
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Joined: 01 February 2007

Hello there,

I have an Orifice Plate installation with flanged tapping on an 8" horizontal pipe for flow measurement. The tapings which is at 3 o'clock is connected to a DP cell transmitter via impulse lines below the Orifice.

Of late we have been having repeated blockage in the impulse line (Service contains Amine, H2S, Sour water and a few particulates Iron & Salts etc). This is usually at the HP side. I was told by process emulsion (Water & Hydrocarbons) may have occurred on the service.

To ensure accurate measurement I do not envisage we move the tapping point above 3'oclock. However following discussion with other engineers we had a number of suggestions which I do not feel too comfortable with hence the post to a wider audience.

Solution 1: Increase the Orifice plate: the rapid drop in DP may have resulted in the build up particulates on the HP side. Hence a larger orifice plate would reduce flow resistance.

Solution2: Re-orientate impulse lines; with the 3 o'clock tapping, re-orientate the impulse line such the DP cell is above the orifice and gravity would prevent a build up of particulates or blockages. (Wouldn't this affect the accuracy of the measurement?)

Solution 3: Use a new technology. Which one?

Ladies & Gents any contributions?

Many thanks
Young Engineer
 29 September 2008 03:19 PM
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Joined: 18 January 2003

You could consider filling your impulse lines with glycol or some other material compatible with your process. This would act as a barrier preventing the process from entrying the impulse lines and choking them. Best of luck.

 25 November 2008 03:21 PM
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Joined: 21 September 2003

I think you have 2 choices solution 2 above, this will not affect the measurement as you are measuring DP i.e. if your transmitter is say 2 foot above the process pipe then you will have the same -ve header (-ve header as in a lower pressure due to gravity) on the high and low impulse connections, You can always adjust the measuring range to take into account of the -ve header.

With solution 3 it depends on what the contents of the pipework is, and what you are measuring ie volumetric or mass flow. An ultrasonics flow meter may work better and without any of the problems associated with the blocking of the impulse lines.
 07 August 2013 06:46 AM
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Dear Sir,

Clearguard design and manufacture the Autorodder, which comes under solution 3.



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