View all text of Subpart C [§ 64.57 - § 64.71]
§ 64.63 - Minimum emergency venting capacity.
(a) The total emergency venting capacity (Q) of the relief devices of an uninsulated MPT must be in accordance with table 1 to § 64.63 or the following formula based upon the pressure relief device operating at a pressure not to exceed the test pressure:
Formula 1 to Paragraph (a)
Where:
Q = Minimum required rate of discharge in cubic feet per minute of free air at standard conditions (60 °F and 14.7 psia).
M = Molecular weight of the product, or 86.7.
T = Temperature, degrees Rankine (460° + temperature in °F of gas at relieving temperature), or 710 °R.
A = Total external surface area of the tank compartment in square feet.
L = Latent heat of the product being vaporized at relieving conditions in Btu per pound, or 144 Btu per pound.
Z = Compressibility factor of the gas at relieving conditions, or 1.0.
C = Constant based on relation of specific heats, equal to 315. (b) The total emergency venting capacity (Q) of an insulated portable tank may have a reduction if—
(1) It is shown to the Coast Guard that the insulation reduces the heat transmission to the tank;
(2) The present reduction of the emergency venting capacity (Q) is limited to the percent reduction of the heat transmission to the tank or 50 percent, whichever is less; and
(3) The insulation is sheathed.
Table 1 to § 64.63—Minimum Emergency Venting Capacity in Cubic Feet: Free Air/Hour
[14.7 lb/in 2a and 60 °F]
| Exposed area
square feet 1 | Cubic feet free air
per hour | Exposed area
square feet 1 | Cubic feet free air
per hour | 20 | 27,600 | 275 | 237,000 | 30 | 38,500 | 300 | 256,000 | 40 | 48,600 | 350 | 289,500 | 50 | 58,600 | 400 | 322,100 | 60 | 67,700 | 450 | 355,900 | 70 | 77,000 | 500 | 391,000 | 80 | 85,500 | 550 | 417,500 | 90 | 94,800 | 600 | 450,000 | 100 | 104,000 | 650 | 479,000 | 120 | 121,000 | 700 | 512,000 | 140 | 136,200 | 750 | 540,000 | 160 | 152,100 | 800 | 569,000 | 180 | 168,200 | 850 | 597,000 | 200 | 184,000 | 900 | 621,000 | 225 | 199,000 | 950 | 656,000 | 250 | 219,500 | 1,000 | 685,000 |
|---|
1 Interpolate for intermediate sizes.