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49 CFR 173.302
(a) Detailed requirements. Nonliquefied compressed gases (except gas in solution) for which charging requirements are not definitely prescribed in §173.304(a)(2) must be shipped, subject to §173.301, and §173.305 in
specification containers as follows:
(1) Specification 3,1 3A, 3AA, 3B, 3C,1 3D,1 3E, 4,1 4A,1 4B, 4BA, 4BW, 4C,1 25,1 26,1 33,1 or 38,1 (§§178.36, 178.37, 178.38, 178.42, 178.50, 178.51, 178.61 of this subchapter). See §§173.34 and 173.301(e).
Note 1: Authorized cylinders containing oxygen which is continuously fed to tanks containing live fish may be shipped irrespective of the provisions of §173.24.
(2) Specification 3HT (§178.44 of this subchapter) cylinders for aircraft
use only, having a maximum service life of 24 years. Authorized only for
nonflammable gases. Cylinders must be equipped with safety relief
devices only of the frangible disc type which meet the requirements of
§173.34(d). Each frangible disc must have a rated bursting pressure which
does not exceed 90 percent of the minimum required test pressure of the
cylinder. Discs with fusible metal backing are not permitted. Spec. 3HT
cylinders may be shipped only when packed in strong outside packagings.
(3) Specification 3AX, 3AAX, or 3T (§§178.36, 178.37, 178,45 of this
subchapter) cylinders are authorized only for the following nonliquefied
gases: Air, argon, boron trifluoride, carbon monoxide, ethane, ethylene,
helium, hydrogen, methane, neon, nitrogen, or oxygen, except that
specification 3T is not authorized for hydrogen. As used in this paragraph
methane is a nonliquefied gas which has a minimum purity of 98.0 percent
methane and which is commerically free of corroding components.
(4) Specification 39 (§178.65 of this subchapter) cylinder. For flammable
gases, internal volume may not exceed 75 cubic inches. Aluminum
cylinders are authorized for oxygen only under the following conditions:
(i) Cylinder threads must be straight threads;
(ii) Cylinder must be equipped only with brass or stainless steel valve; and
(iii) Each cylinder must be cleaned in compliance with the requirements of
Federal Specification RR-C-901c, dated January 15, 1981, paragraphs
3.7.2 and 3.8.2. Cleaning agents equivalent to those specified in
RR-C-901c, may be used; however any cleaning agent must not be
capable of reacting with oxygen. One cylinder selected at random from a
group of 200 or less cleaned at the same time, must be tested for oil
contamination in accordance with specification RR-C-901c, paragraph
4.4.2.3 and meet the standard of cleanliness specified.
(5) Specification 3AL (§178.46 of this subchapter) cylinders are
authorized only for the following nonliquefied gases: air, argon, carbon
monoxide, diborane, ethylene, helium, mercury free hydrogen, krypton,
methane, nitrogen, neon, oxygen and xenon. Flammable gases shipped in
3AL cylinders are authorized only when transported by highway, rail and
cargo-only aircraft. When used in oxygen service, aluminum cylinders must
be in compliance with the following conditions:
(i) Cylinder must be equipped only with brass or stainless steel valve;
(ii) Cylinder must have only straight threads in the opening;
(iii) Each cylinder must be cleaned in compliance with the requirements of
Federal Specification RR-C-901c, dated August 1, 1967, paragraphs
3.7.2, and 3.8.2. Cleaning agents equivalent to those specified in
RR-C-901c may be used; however, any cleaning agent must not be
capable of reacting with oxygen. One cylinder selected at random from a
group of 200 or less, cleaned at the same time, must be tested for oil
contamination in accordance with Specification RR-C-901c, paragraph
4.4.2.3, and meet the standard of cleanliness specified; and
(iv) The pressure in the cylinder may not exceed 3,000 psig at 70° F.
(b) Filling limits. (See §173.301(e).)
(c) Special filling limits for Specifications 3A, 3AX, 3AA, 3AAX, and 3T
cylinders. Specifications 3A, 3AX, 3AA, 3AAX, and 3T (§§178.36,
178.37, 178.45 of this subchapter) cylinders may be charged with
compressed gases, other than liquefied, dissolved, poisonous, or
flammable gases to a pressure 10 percent in excess of their marked
service pressure, provided:
(1) That such cylinders are equipped with frangible disc safety relief
devices (without fusible metal backing) having a bursting pressure not
exceeding the minimum prescribed test pressure.
(2) That the elastic expansion shall have been determined at the time of
the last test or retest by the water jacket method.
(3) That either the average wall stress or the maximum wall stress does not
exceed the wall stress limitation shown in the following table (see Notes 1,
2 and 3):
Type of steel Average wall Maximum wall
stress stress
limitation limitation
Plain carbon steels over 0.35 53,000 58,000
carbon and medium manganese
steels
Steels of analysis and heat- 67,000 73,000
treatment specified in spec.
3AA
Steel of analysis and heat 87,000 94,000
treatment specified in Spec.
DOT-3T
Plain carbon steels less than 45,000 48,000
0.35 carbon made prior to 1920
Note 1: The average wall stress shall be computed from the elastic expansion data using the following formula:
where:
S = wall stress, pounds per square inch;
EE = elastic expansion (total less permanent) in cubic centimeters;
K = factor x 10-7 , experimentally determined for the particular type of
cylinder being tested, or derived in accordance with CGA Pamphlet C-5;
V = internal volume in cubic centimeter (1 cubic inch=16.387 cubic
centimeters);
P = test pressure, pounds per square inch.
Formula derived from formula of Note 2 and the following:
Note 2: The maximum wall stress shall be computed from the formula:
where:
S = wall stress, pounds per square inch;
P = test pressure, pounds per square inch;
D = outside diameter, inches;
d = D-2t, where t=minimum wall thickness determined by a suitable
method
Note 3: Compliance with average wall stress limitation may be determined through computation of the elastic expansion rejection limit in accordance with CGA Pamphlet C-5 or through the use of the manufacturer's marked elastic expansion rejection limit (REE) on the cylinder.
(4) That an external and internal visual examination made at the time of
test or retest shows the cylinder to be free from excessive corrosion,
pitting, or dangerous defects.
(5) That a plus sign (+) be added following the test date marking on the
cylinder to indicate compliance with paragraphs (c) (2), (3), and (4) of this
section.
Other Sections: DOT Definitions | DOT Regs. 172.600