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8-7
Specifications
Pressure Loss Equations to determine approximate pressure loss:
English
Metric
where:
∆P = Pressure loss (psi or kPa)
f
= Density at operating conditions (lb/ft
3
or kg/m
3
)
D = Flowmeter bore diameter (in. or mm)
Q
gpm or lpm
= Actual volumetric flow rate (gallons/minute or
liters/minute)
Q
acfm or acmh
= Actual volumetric flow rate (cubic feet/min or cubic
meters/hour)
NOTE
Pressure loss is 1.8 ∆P for the dual-sensor meter.
Minimum Back Pressure
(Liquids)
Cavitation, the release of vapor from a liquid, may be avoided by
remaining within the proper flow range of the meter and by following
appropriate system design. For some liquid applications, incorporation
of a back pressure valve should be considered. To prevent cavitation,
the minimum back pressure should be:
P = 2.9
∆P + 1.3 p
v
where:
P = Line pressure, five pipe diameters downstream of the meter (psia
or kPa)
∆P = Pressure loss across the meter (psi or kPa)
p
v
= Liquid vapor pressure at operating conditions (psia or kPa)
NOTE
Pressure loss is 1.8 ∆P for the dual-sensor meter.
Damping
Adjustable between 0.2 and 255 seconds.
Response Time Maximum time required to reach 63.2% of actual input flow with
minimum damping (0.2 seconds) shall be 0.2 seconds or three vortex
shedding cycles, whichever is greater.
Turn-on Time Performance within specifications no greater than 10.0 seconds after
power is applied.
Liquids()∆P
3.40 10
5–
×()ρ
f
× Q
gpm
()
2
×
D
4
---------------------------------------------------------------------------=
Gases()∆P
1.90 10
3–
×()ρ
f
× Q
acfm
()
2
×
D
4
-----------------------------------------------------------------------------=
Liquids()∆P
0.425()ρ
f
× Q
lpm
()
2
×
D
4
----------------------------------------------------------=
Gases()∆P
118()ρ
f
× Q
acmh
()
2
×
D
4
----------------------------------------------------------=