46 C.F.R. § 64.63

Current through October 31, 2024
Section 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)

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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/in2 a and 60 °F]

Exposed area square feet 1 Cubic feet free air per hour Exposed area square feet 1Cubic feet free air per hour
2027,600275237,000
3038,500300256,000
4048,600350289,500
5058,600400322,100
6067,700450355,900
7077,000500391,000
8085,500550417,500
9094,800600450,000
100104,000650479,000
120121,000700512,000
140136,200750540,000
160152,100800569,000
180168,200850597,000
200184,000900621,000
225199,000950656,000
250 219,500 1,000685,000

1 Interpolate for intermediate sizes.

46 C.F.R. §64.63

CGD 73-172, 39 FR 22950, June 25, 1974, as amended by CGD 84-043, 55 FR 37410, Sept. 11, 1990; 55 FR 47477, Nov. 14, 1990
89 FR 50199 , 9/10/2024