Nominal Size Selection Calculation Formula; Installation; Example Of Piping - Yoshitake GP-1000 Installation & Operation Manual

5.5 Nominal size selection calculation formula

The appropriate nominal size can be calculated by obtaining the Cv value for the operating conditions
in question, as shown below.
• Cv value calculation formula
P
> 1
P
2
2
Cv
P
< 1
P
2
2
Cv =
• Rated Cv value table (When Cv correction coefficient is C=1)
Nominal size
Rated Cv value
※ Correction of rated Cv value
If the inlet pressure exceeds 0.7 MPa, and the pressure reducing is 0.4 MPa or less,
find the appropriate correction coefficient C using chart below, and multiply the rated
Cv value, and obtain the corrected Cv value.
1.0
0.9
(イ)
(ロ)
0.8
0.7
0.6
0.5
0.4
0.00 0.05 0.10 0.15

6. Installation

6.1 Example of piping

Wk
=
∆ +
138 P(P P )
1 2
Wk
120P
1
15A 20A 25A
1 2.3 4
0.20 0.25 0.30
P ：Reduced pressure MPa
2
W: Max. steam flow rate [kg/h]
P : Inlet pressure [MPa･A]
1
P : Reduced pressure [MPa･A]
2
ΔP: P −P
1
k: 1+0.0013 × {super-heated steam
32A 40A 50A
6.5 9 16
[Ex.]
Take a pressure reducing valve whose inlet
pressure is 0.8 MPa, reduced pressure is 0.05
MPa. Find the inlet and reduced pressure
intersection point (A) at the left chart, then
draw a horizontal line in the leftward
direction to point (B) which indicates a
correction coefficient of 0.85. For a nominal
size of 25A, the corrected Cv value would be
calculated as follows:
4(rated Cv value) × 0.85(correction
0.35 0.40
coefficient) = 3.4
-6-
[MPa]
2
temp.[℃]−saturated steam
temp.[℃]}
65A 80A 100A
25 36 64
■EPDT-081a■