5
■EPDT-179c■
5.4 Nominal size selection
5.4.1 Nominal size selection chart
Determination of nominal size when the inlet pressure is in a range 2.5 kPa to
200 kPa (fluid: air, at 20
℃
)
《
Example
》
Select the nominal size of a pressure reducing valve to be operated with the inlet pressure
10 kPa and reduced pressure 3 kPa at a flow rate 15 m
3
/h (normal condition): First locate the
point (A) on the chart where the inlet pressure 10 kPa line and reduced pressure 3 kPa line
intercross. Draw a line from the intersection straight down to the point (B) where it meets the
line representing flow rate 15 m
3
/h (normal condition). The point (B) locates between nominal
size 20 A and 25 A. It is selected to use 25 A (larger one) as the desired nominal size.
T
able 1 Determination of nominal size when inlet pressure in
the range 200 to 400 kPa
Rated flow rate (Nm
3
/h)
Reduced pressure
（
kPa
）
Nominal
size
Inlet pressure
（
kPa
）
0.5-4 excl.
4-20 incl.
15A
200-400 incl.
60
60
200-300 excl.
90
90
20A
300-400 incl.
90
120
200-300 excl.
120
120
300-400 excl.
120
150
25A
400
120
190
