I ask a question regarding the flow rate measurement by the orifice plate, when the straight run is half of the required straight run. How can the error due to short straight run be solved?
If you are asking, "what is the error?" your answer is we can't tell. It depends on what is upstream of the foreshortened straight run. If you have two elbows out of plane, the error might be as high as 50% of reading. If you have a partially opened butterfly valve, your error might be as high as 100% of reading. Nobody knows.
If you are asking, "how do I fix the problem?" the answer is to either go back and install the correct amount of straight run, or install a flow
straightening device, such as Vortab, at the correct location in front of the orifice plate.
If this is a conductive liquid flow, you can install a magnetic flowmeter, which requires virtually no straight run.
If this is a nonconductive liquid flow, a V-cone can be installed, which will use the existing orifice plate's differential pressure transmitter, but which requires little or no straight run. You can also use a Swirlmeter in
this application.
If this is a gas flow, you can try a V-cone there, as well.
Hope this helps,
Walt Boyes
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Spitzer and Boyes LLC
"consulting from the engineer
to the distribution channel"
21118 SE 278th Place
Maple Valley, WA 98038
Ph. 425-432-8262
Fx. 253-981-0285 [email protected] www.spitzerandboyes.com
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You can use a Flow Rectifier Plate or tube bundle. The flow plate can reduce the required upstream length to 5D or less depending on the
application. You can build one yourself using ASME/AGA guidelines or buy them commercailly. We offer the flow plate type for virtually any
diameter pipe. Contact me if you would like details.
