# Flow meter reading

K
Thread Starter

#### KS Jais

If I am a new to a plant and pull out a orifice calculation datasheet like below, how do I know whether the orifice is reading the flow at the "design" operating temperature or at the base temperature. Of course for mass balances, we would need to correct for the real operating temperature, but before even going to that, how do I interpret the flow that I see on the DCS screen?

Data Sheet:
Pipe ID @20 deg c= 154.080 mm
Pipe ID @ FTP = 154.314 mm

Orifice Bore @ 20 deg C = 106.802 mm
Orifice Bore @ FTP= 107.035 mm

Fluid = Liquid

Vol Max Flow Rate @ FTP = 180 m3/hr
Vol Nor Flow Rate @ FTP = 129 m3/hr

Density @ FTP = 758 kg/m3
Operating Pressure = 10.35 kg/cm2g
Operating Temp = 148 deg C
Base Temp = 15 deg C

If my real operating temp in the plant is say also 148 deg and I read a reading of 100 m3/hr.
Would this 100 m3/hr be 100 m3/hr at 148 deg C or 100 m3/hr at 15 deg C?

This is question is quite simple in nature, but appreciate any helptaht I can get.

R

#### R.Sundar

From your extract of data sheet, I see the Normal and Maximum flow rates are given as "@FT" meaning at flowing temperature. So what you read is at
flowing temperature. While sizing for orifice bore, there is Fa factor to account for orifice plate expansion and a resultant decrease in bore size. This is based on material and temperature data. Hope this clarifies.

Sundar

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