DP type Orifice plate for flow measurement is used to measure the bidirectional flow measurement to measure the Flow for Export and import of steam.

DP type Orifice plate for flow measurement is used to measure the bidirectional flow measurement to measure the Flow for Export and import of steam.
but, it is not measuring accurate.
orifice for the both Transmitter is common. Export is Transmitter-A and Import is Transmitter-B.
Range for Export is 0-78TPH and import is 0-20 TPH.
what is the reliability of such orifice type flow measurement DP type flow transmitter?
 
DP type Orifice plate for flow measurement is used to measure the bidirectional flow measurement to measure the Flow for Export and import of steam.
but, it is not measuring accurate.
orifice for the both Transmitter is common. Export is Transmitter-A and Import is Transmitter-B.
Range for Export is 0-78TPH and import is 0-20 TPH.
what is the reliability of such orifice type flow measurement DP type flow transmitter?
Hello Nikhil,
When using an orifice for bi-directional flow, the bore edge must be square edged on both sides of the plate. For the left to right flow, your HP tap connection would be on the upstream flange tap and your low pressure connection would be on the downstream flange tap; for the reverse flow, your HP tap connection would be on the upstream flange tap and the LP on the downstream. Note also that your bore size must be such that the orifice plate will develop a high enough DP at the minimum reverse flow in order for your DP transmitter to process it and the calibration of the reverse flow DP transmitter must be consistent with the DP that is occurring. Finally, you need to check your pipe Reynolds number to be sure that there are not excessive bias errors that would impact accuracy. Hope this helps. Bruce Briggs, President, Primary Flow Signal Inc.
 
Thank You sir, for your valuable reply.
the orifice for the both the transmitter is common, i think the beta ratio for the orifice to be same for both the transmitter.
but i found to the data sheet that the beta ration for Transmitter-A is 0.7061and Reynold number is 3914136.11.
where as the beta ratio for Transmitter-B is 0.682 and Reynold no is 1017913.58.
can it be the reason for the accuracy which is the issue to my transmitter?
 
Hi Nikhil,
Beta ratio is the ratio of the bore/throat “d” over the ID of the pipe “D”. Therefore, from your data sheets Transmitter A has a Beta ratio of 0.7061 and unless the pipe ID on the downstream pipe is different that the pipe ID for Trasmitter A, they should be the same ratio. Can you confirm the pipe ID for both upstream pipe sections (forward and reverse). Your pipe Reynolds numbers are fine for standard accuracy. The other question, once the pipe ID question is resolved is what is the calibrated span on your DP transmitters - if the beta ratio for each direction is not the same (pipe ID is different) then each transmitter must be calibrated according to the differential developed by the meter in that flow direction.
 
I also made use of such plates to measure air/nitrogen flow. What I learned is to put the plate with pressure connections in a straight pice of pipe (at least 5x diameter away from a bend) and the pressure differences were very low, just a few pascals. So I had to make use of a very accurate low delta-P pressure measurement device that is temperature independent.
Also note that these plates must be calibrated with a real flowmeter since I had problems that they were not linear (deltaP pressure was not fully linear to flow).
It is a nice and simple measurement, but you need to take the limitations into account.
 
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