Flow Calculations (4)

   

Characteristic Flow Curves for Globe Stop, Stop-Check, Lift-Check Valves

Estimating Cv For Less Than Fully Open Valves



Figure 2
Globe Stop, Stop-Check and
Lift-Check Valves

Pressure Seal T-Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv

Valve Size

Pressure Class

900

1500

2500

21/2
3
4
6
8
10
12
14

90
105
195
455
800
1250
1820
2205

65
95
170
395
695
1085
1580

45
65
105
265
470
750
1100

 Pressure Seal Y-Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv

Valve Size

Pressure Class

600

900

1500

2500

8
10
12
14
16
18
20
24

2025
3025
4600
4300
7650
7325
11800
16450

1750
2725
3825
3650
6000
5825
9125
13500

1750
2725
3825
3650
6000
5825
9125
13500

1175
1875
2650
4075
3775
6625
6225
9050

    The flow coefficient (Cv) listed in the tables apply to fully open valves only. Flow coefficients at other than fully open may be approximated by use of the characteristic flow curves for tilting disc check and globe valves. Gate valves are not recommended for throttling service.

EXAMPLE:
  What is the Cv of a 12 inch Class 900 Hanover pressure seal globe valve 1/4 open?

 



Figure 3
Y-Globe Stop, Stop-Check and
Lift-Check Valves

Pressure Seal Venturi Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv

 

Valve Size

Pressure Class

900

1500

2500

8 x 6 x 8
10 x 8 x 10
12 x 10 x 12
14 x 12 x 14
16 x 14 x 16

450
770
1215
1775
2125

390
690
1055
1550

260
465
745
1070

 

Pressure Seal Venturi Y-Globe Stop,
Stop-Check and Lift-Check Valves FULL OPEN Cv

Valve Size

Pressure Class

600

900

1500

2500

8 x 6 x 8
10 x 8 x 10
12 x 10 x 12
14 x 12 x 14
16 x 14 x 16
18 x 16 x 18
20 x 18 x 20
22 x 20 x 22
16 x 24 x 26

1100
1925
2875
4375
4075
7250
6950
11200
15850

1000
1675
2600
3650
3450
5700
5525
8675
12825

1000
1675
2600
3650
3450
5700
5525
8675
12825

650
1125
1775
2525
3875
3575
6300
5925
8600

SOLUTION:
  From the flow coefficient table above, the fully open Cv for a 12 inch, Class 900 globe valve is 1820.

    Consulting Figure 2, the percent of fully open Cv at 1/4 valve open is 52%.

    The Cv at 1/4 open is then computed as:
  0.52 x 1820 = 946.