Datasheet

12
464
Subject to change
SI UNITS, SYMBOLS AND DIMENSIONING
C value
C value (conductance) is the unit that ISO and the cur-
rent standard uses to indicate ow. One way to nd out
a product’s C value is dividing the product’s maximum
ow rate (Q
n
) with the absolute inlet pressure (P1a). The
unit is liter/second/bar. Q
n
≈ C · 270. The factor 270 will
vary depending on the product’s b value.
b value
A product’s b value is obtained by dividing the absolute
outlet pressure (P2a) with the absolute inlet pressure
(P1a), at the crossing between the upper and lower
critical ow. The value is a number less than 1 and is
without a unit as it indicates a relationship. The larger
the number, the greater the ow. Two products can have
the same C value but different b value. This means that
the products have the same maximum ow rate (Q
n
), but
different pressure drops in, for example, half the ow.
kv value
Metric measurements in “normal liters per minute”.
This measurement is based on measurements of water.
When a liter of water each minute passes with a pres-
sure drop of 1 bar is dened q value to 1. There is thus a
pure and dimensionless correlation factor.
Kv value
As the kv value above, however, expressed in m
3
/h, a
measure that meets the SI standard.
Cv factor
As the above value but based on the Anglo-Saxon sys-
tem of measurement. It is related to US gallons (USG)
per minute at a pressure drop of 1 psi (0.07 bar) and a
temperature of 60 °F (15.6 °C).
f factor
As Cv factor but in Imperial gallons (gal) per minute.
Pressure
regulator
Adjustable
ow controller
Measuring
object
Flow
meter
Pressure
gauge
Pressure
gauge
p
1
p
2