A Rate of Discharge

Section 215 Section 215.TABLE A   Rate of Discharge Minimum required rate of discharge in cubic feet per minute (CFM) of air for safety relief valves.  Discharge measured at 60 degrees F. and atmospheric pressure (14.7 pounds per square inch). Surface Area Sq. Ft. CFM Surface Area Sq. Ft. CFM Surface Area Sq. Ft. CFM 20 258 185 1,600 900 5,850 25 310 190 1,640 950 6,120 30 360 195 1,670 1,000 6,380 35 408 200 1,710 1,050 6,640 40 455 210 1,780 1,100 6,900 45 501 220 1,850 1,150 7,160 50 547 230 1,920 1,200 7,410 55 591 240 1,980 1,250 7,660 60 635 250 2,050 1,300 7,910 65 678 260 2,120 1,350 8,160 70 720 270 2,180 1,400 8,410 75 762 280 2,250 1,450 8,650 80 804 290 2,320 1,500 8,900 85 845 300 2,380 1,550 9,140 90 885 310 2,450 1,600 9,380 95 925 320 2,510 1,650 9,620 100 965 330 2,570 1,700 9,860 105 1,010 340 2,640 1,750 10,090 110 1,050 350 2,700 1,800 10,330 115 1,090 360 2,760 1,850 10,560 120 1,120 370 2,830 1,900 10,800 125 1,160 380 2,890 1,950 11,030 130 1,200 390 2,950 2,000 11,260 135 1,240 400 3,010 2,050 11,490 140 1,280 450 3,320 2,100 11,720 145 1,310 500 3,620 2,150 11,950 150 1,350 550 3,910 2,200 12,180 155 1,390 600 4,200 2,250 12,400 160 1,420 650 4,480 2,300 12,630 165 1,460 700 4,760 2,350 12,850 170 1,500 750 5,040 2,400 13,080 175 1,530 800 5,300 2,450 13,300 180 1,570 850 5,590 2,500 13,520 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: a)         Cylindrical container with hemispherical heads area = (overall length in feet times outside diameter in feet times 3.1416) b)         Cylindrical container with semi-ellipsoidal heads. Area = (overall length in feet plus 0.3 outside diameter in feet) times diameter in feet times 3.1416. c)         Spherical Container. Area = Outside diameter in feet squared times 3.1416 Flow Rate SCFM Air = cubic feet per minute of air required at standard conditions, 60 degrees F. and atmospheric pressure (14.7 psia). The rate of discharge may be interpolated for intermediate values of surface area.  For container with total outside surface area greater than 2,000 sq. ft., the required flow rate can be calculated using the formula, Flow Rate SCFM Air = 22.11A degrees .82, where A= outside surface area of the container in square feet.