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Code of Federal Regulations Title 46. Shipping § 46.64.63 Minimum emergency venting capacity

Current as of January 02, 2025 | Updated by Findlaw Staff

(a) The total emergency venting capacity (Q) of the relief devices of an uninsulated MPT must be in accordance with Table 1 or the following formula based upon the pressure relief device operating at a pressure not to exceed the test pressure:

Q=

633,000

(A0.82/LC)

square root(ZT/M)

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 degrees F of gas at relieving temperature), or 710° Rankine.

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, in accordance with appendix J of division 1 of section VIII of the ASME Code, 1974 edition, or 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—Minimum emergency venting capacity in cubic feet: free air/hour (14.7 lb/in2a and 60° F)

Exposed area square feet1

Cubic feet free air per hour

Exposed area square feet1

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.

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Cite this article: FindLaw.com - Code of Federal Regulations Title 46. Shipping § 46.64.63 Minimum emergency venting capacity - last updated January 02, 2025 | https://codes.findlaw.com/cfr/title-46-shipping/cfr-sect-46-64-63/

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