Pressure Tap and sensor location for orifice plate 2

[ajs83]

Does anybody know the correct spacing for pressure taps before and after an orifice plate. I read in a book that D and D/2, Flange, and corner taps were recommended. However, the same book also had a figure for the pressure tap locations at 2D and 2D.

Also, where is the best location to mount a temperature sensor relative to the orifice plate.

 

[btrueblood]

You want a copy of ISO 5167-1, and -2.

You can use corner taps, flange taps (located 25.4mm up- and downstream) or D and D/2 taps. "D and D/2 taps" imply the upstream pressure sensor is D away, and downstream D/2. Any other spacing of taps is going to give you increased uncertainty relative to published data correlations. The above gives a correlation formula that depends on the tap location; I would bet that a published correlation in a book somewhere doesn't include those effects, since they are generally pretty small...but it's safest to use corner taps IMO.

From the above reference, the preferred method is a downstream tap. The temp sensor or densitometer well, of diameter < .03*D should be located at least 5D upstream, or at least 4D to 8D downstream depending on the diameter ratio d/D ([&beta;]).

 

[zdas04]

In API 14.3 Part 2, section 2.5.4.1 for flange taps, the taps must be 1-inch upstream of the upstream plate face and 1-inch downstream of the downstream plate face.

Pipe taps are no longer allowed.



David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[ajs83]

Does anyone have a copy of ISO 5167-1 and 2 that they could send to me. I would really appreciate it.

Why are pipe taps no longer allowed?

 

[Zapster]

Is this part of a metering train for custody transfer of gas?

 

[zdas04]

If you're in the US then the code is API 14.3 not ISO 5167 (I haven't looked at 5167 in a few years, but they used to be really close to API 14.3). You need Part 2, and downloads with copyright protection usually costs about $167 if you download it from IHS (

http://store.ihs.com/specsstore/con...urVer=false&docId=ONGYIBAAAAAAAAAA&mid=W097).

The book is also known as AGA 3.

"sending you a copy" is against the law.

The committee found that the quality control on field installed pipe taps was universally inconsistent and found that improper taps were creating excessive uncertainty. I just found that my copy of Part 2 is out of date by a few years so I just bought a new copy. I'll let you know if they've added them back in .

David

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[zdas04]

OK, in the April, 2000, version of Part 2, the only reference is to Appendix 3-D of Part 3. In Part 3, Appendix D (current version, August, 1992) "Meter tubes that use pipe taps shall have the center of the upstream tap hole located 2.5 times the published or actual inside diameter from the upstream face of the orifice plate" and "the center of the downstream tap hole shall be located eight times the published or actual inside diameter from the downstream face of the orifice plate." And then they have a 10 page table of factors that have to be used to calculate a C prime for pipe taps. An OFU is cheaper than reprogramming an RTU.

David