Minimum required rate of discharge in cubic feet per minute of air at 120% of the maximum permitted start to-discharge pressure for safety relief valves to be used on containers other than those constructed in accordance with DOT ( Department of Transportation ) specification.

Surface Area

Sq. Ft.
Flow Rate

CFM Air
Surface Area

Sq. Ft.
Flow Rate

CFM Air
Surface Area

Sq. Ft.
Flow Rate

CFM Air
20 or less

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

145

150

155

160

165
626

751

872

990

1100

1220

1330

1430

1540

1640

1750

1850

1950

2050

2150

2240

2340

2440

2530

2630

2720

2810

2900

2990

3080

3170

3260

3350

3440

3530
170

175

180

185

190

195

200

210

220

230

240

250

260

270

280

290

300

310

320

330

340

350

360

370

380

390

400

450

500

550
3620

3700

3790

3880

3960

4050

4130

4300

4470

4630

4800

4960

5130

5290

5450

5610

5760

5920

6080

6230

6390

6540

6690

6840

7000

7150

7300

8040

8760

9470
600

650

700

750

800

850

900

950

1000

1050

1100

1150

1200

1250

1300

1350

1400

1450

1500

1550

1600

1650

1700

1750

1800

1850

1900

1950

2000


10170

10860

11550

12220

12880

13540

14190

14830

15470

16100

16720

17350

17960

18570

19180

19780

20380

20980

21570

22160

22740

23320

23900

24470

25050

25620

26180

26750

27310



Surface area = Total outside surface area of container in square feet.
When the surface area is not stamped on the name plate or when the marking is not legible, the area can be calculated by using one of the following formulas:
  1. Cylindrical container with hemispherical heads Area = Overall length X outside diameter X 3.1416
  2. Cylindrical container with semi-ellipsoidal heads Area = (Overall length + .3 outside diameter) X outside diameter X 3.1416
  3. Spherical container Area = Outside diameter squared X 3.1416

Flow Rate-CFM Air = Required flow capacity in Cubic feet per minute of air at standard conditions, 60°F. and atmospheric pressure (14.7 psig).

The rate of discharge may be interpolated for intermediate values of surface area. For containers with total outside surface area greater than 2000 square feet, the required flow rate can be calculated using the formula:

Flow Rate - CFM Air = 53.632 A 0.82 Where A = total outside surface area of the container in square feet.

Valves not marked "Air" have flow rate marking in cubic feet per minute of liquefied petroleum gas. These can be converted to ratings in cubic feet per minute of air by multiplying the liquefied petroleum gas ratings by the factors listed below. Air flow ratings can be converted to ratings in cubic feet per minute of liquefied petroleum gas by dividing the air ratings by the factors listed below.

Air Conversion Factors

Container Type 100 125 150 175 200
Air Conversion Factor 1.162 1.142 1.113 1.078 1.010

See Rego Products Safety Warning WB-6 for important warning Information.