Emerson daniel 1500 series, Руководство пользователя

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Back pressure calculation
Back pressure calculation Equation 2-1:
P
b
≥ 2
△
p + 1.25 p
e
P
b
Minimum back pressure, pounds per square inch gauge (psig).
△
p
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.
Flow straightening devices
For accurate operation of the turbine meter, a flow conditioning plate, flow straightener
(designed for the turbine meter), or a straight run of pipe (20 pipe diameters long) is
required. All piping must be the same diameter as the turbine meter. Flow straightening
devices must be installed directly upstream of the turbine meter and should not contain
flow restricting devices which could cause reversal of the flow straightening effect.
Strainers
Install the correct size strainer upstream of the turbine meter to protect it from foreign
material damage. Recommended mesh sizes include: 80 mesh for refined products, and
20 to 40 mesh for crude products (depending on the product being measured).
Clean the strainer basket regularly, to prevent filling and rupturing of the screen.
Pressure gauges installed on both sides of the strainer monitor differential pressure across
the strainer. High pressure differential caused by filling of the basket or occlusion of
foreign material can cause a strainer basket rupture, resulting in possible turbine meter
damage.
Operating conditions and specifications
User manual 31