Regulations last checked for updates: Nov 22, 2024
Title 46 - Shipping last revised: Nov 04, 2024
§ 64.57 - Acceptance of pressure relief devices.
A pressure relief device for an MPT must be—
(a) From a supplier accepted under chapter I of title 46, Code of Federal Regulations; or
Note 1 to paragraph (a):
Accepted suppliers are listed in CG-190, Equipment list.
(b) Accepted by the Coast Guard in accordance with the procedures in § 50.25-10 of this subchapter.
[CGD 84-043, 55 FR 37410, Sept. 11, 1990, as amended by USCG-2020-0634, 89 FR 50199, June 12, 2024]
§ 64.59 - Spring loaded pressure relief valve.
A spring loaded pressure relief valve must—
(a) Be set at a nominal pressure of 125 percent of the maximum allowable working pressure;
(b) Have a minimum normal venting capacity that is sufficient to prevent the tank pressure from exceeding 137.5 percent of the maximum allowable working pressure;
(c) Close after discharge of a pressure not lower than 115 percent of the maximum allowable working pressure; and
(d) If closed, remain closed at any pressure less than 115 percent of the maximum allowable working pressure.
§ 64.61 - Rupture disc.
If a rupture disc is the only pressure relief device on the tank, the rupture disc must—
(a) Rupture at a pressure of 125 percent of the maximum allowable working pressure; and
(b) Have a minimum normal venting capacity that is sufficient to prevent the tank pressure from exceeding 137.5 percent of the maximum allowable working pressure.
§ 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
|
§ 64.65 - Vacuum relief device.
(a) Each MPT that is designed for an external pressure of less than 7.5 psig must have a vacuum relief device.
(b) A vacuum relief device for an MPT must—
(1) Open at an external pressure of not less than 3 psig; and
(2) Have an opening with a cross-section of 0.44 square inch or more.
[CGD 84-043, 55 FR 37410, Sept. 11, 1990]
§ 64.67 - Shutoff valve.
A shutoff valve may not be located—
(a) Between the tank opening and pressure relief device; or
(b) On the discharge side of the pressure relief device.
§ 64.69 - Location of the pressure relief device.
A pressure relief device must be—
(a) Accessible for inspection and repair before stowage of the tank; and
(b) Attached so that escaping gas does not impinge on the tank or framework.
§ 64.71 - Marking of pressure relief devices.
A pressure relief device must be plainly and permanently marked with the—
(a) Set pressure rating;
(b) Rated flow capacity expressed as cubic feet of standard air (60 °F 14.7 psia) per minute and the pressure at which the flow capacity is determined;
(c) Manufacturer's name and identifying number; and
(d) Pipe size of inlet.
source: CGD 73-172, 39 FR 22950, June 25, 1974, unless otherwise noted.
cite as: 46 CFR 64.71