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:
- Cylindrical container with hemispherical heads Area = Overall length X outside diameter X 3.1416
- Cylindrical container with semi-ellipsoidal heads Area = (Overall length + .3 outside diameter) X outside diameter X 3.1416
- 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.
