flowmeter rerange

[helpyou]

HI

need to rerange orifice plate differential pressure flow transmitter. Should I worry about the orifice plate capacity/parameters or I just have to look at the transmitter factory differential pressure range to make sure the new DP falls within the transmitter range. your thoughts please ? for info the new flow is +50% of the old flow which means the new DP will be double the old DP.

Thank you

 

[danw2]

No, when the flow rate increases by 50% from 100% to 150%, the DP increases 225%, not by 150%

Flow rate is the square root of the normalized percentage of DP (not the DP itself, but its percentage in relationship to the design DP for max flow at design conditions).

normalized percent of flow squared = normalized percent DP
square root of normalized percent DP = normalized percent of flow rate

150% flow rate = 1.5 normalized percent
1.5^2 (flow rate) = 2.25 (DP)
2.25 normalized percent DP = 225% DP

or working backwards, DP to flow rate
square root 2.25 (DP) = 1.5 or 150% (flow rate)

You need to decode the model number on the transmitter and see what its maximum range is to see if can be re-ranged to cover the increased DP range.

For example, if the xmtr was configured for 0-100 inwc for your X max flow rate, then it would need to be configurable for 0-225 inwc for the increased 150% X flow rate.

The permanent pressure drop across the orifice plate will also increase.