[Title 46 CFR C]
[Code of Federal Regulations (annual edition) - October 1, 2006 Edition]
[Title 46 - SHIPPING]
[Chapter I - COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)]
[Subchapter F - MARINE ENGINEERING]
[Part 64 - MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS]
[Subpart C - Pressure Relief Devices and Vacuum Relief Devices for MPTs]
[From the U.S. Government Publishing Office]
46SHIPPING22006-10-012006-10-01falsePressure Relief Devices and Vacuum Relief Devices for MPTsCSubpart CSHIPPINGCOAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED)MARINE ENGINEERINGMARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS
Subpart C_Pressure Relief Devices and Vacuum Relief Devices for MPTs
Sec. 64.57 Acceptance of pressure relief devices.
A pressure relief device for an MPT must be--
(a) From a supplier \2\ accepted under Chapter I of Title 46, Code
of Federal Regulations; or
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\2\ Accepted suppliers are listed in CG-190, Equipment list.
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(b) Accepted by the Coast Guard in accordance with the procedures in
Sec. 50.25-10 of this chapter.
[CGD 84-043, 55 FR 37410, Sept. 11, 1990]
Sec. 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.
Sec. 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.
Sec. 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 or the
following formula based upon the pressure relief device operating at a
pressure not to exceed the test pressure:
[GRAPHIC] [TIFF OMITTED] TC13NO91.047
where:
Q=Minimum required rate of discharge in cubic feet per minute of free
air at standard conditions (60 [deg]F and 14.7 psia).
M=Molecular weight of the product, or 86.7.
T=Temperature, degrees Rankine (460[deg] + temperature in degrees F of
gas at relieving temperature), or 710[deg] 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;
[[Page 322]]
(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/in\2\a and 60 [deg]F)
------------------------------------------------------------------------
Exposed area Cubic feet free Exposed area Cubic feet free
square feet \1\ air per hour square feet \1\ 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
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\1\ Interpolate for intermediate sizes.
[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]
Sec. 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]
Sec. 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.
Sec. 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.
Sec. 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
[deg]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.
Subpart D [Reserved]