Figure 2-1: Effects of back pressure
Back pressure calculation
Equation 2-2: Back pressure calculation
P
b
≥ 2Δp + 1.25p
e
P
b
Minimum back pressure, pounds per square inch gauge (psig)
Δp
Pressure drop through the meter at the maximum operating flow rate for the liquid
being measured, pounds per square inch (psi).
P
e
Equilibrium vapor pressure of the liquid at the operating temperature, pounds per
square inch absolute (psia), gauge pressure plus atmospheric pressure.
Additional devices for accurate measurement
Valves
The metering system should have a flow rate control valve located at a convenient
distance downstream of all measurement equipment. The function of the control valve is
to limit and maintain system pressure on the meter. This avoids cavitation.
Valves should be capable of rapid, smooth opening and closing with positive shut-off.
• When used for intermittent flow, valves should be fast-acting and shock-free.
• Bypass lines should be equipped with blind or positive shutoff devices.
• Shut-off or control valves should be located downstream of the turbine meter.
User manual Operating conditions and specifications
P/N 3-9008-515 March 2019
User manual 45
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