Section

[Code of Federal Regulations]
[Title 49, Volume 2]
[Revised as of October 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR178.57]

[Page 810-816]

TITLE 49--TRANSPORTATION

CHAPTER I--RESEARCH AND SPECIAL PROGRAMS ADMINISTRATION, DEPARTMENT OF
TRANSPORTATION

PART 178--SPECIFICATIONS FOR PACKAGINGS--Table of Contents

Subpart C--Specifications for Cylinders

Sec. 178.57 Specification 4L welded insulated cylinders.

(a) Type, size, service pressure, and design service temperature. A
DOT 4L cylinder is a fusion welded insulated cylinder with a water
capacity (nominal) not over 1,000 pounds water capacity and a service
pressure of at least 40 but

[[Page 811]]

not greater than 500 psig conforming to the following requirements:
(1) For liquefied hydrogen service, the cylinders must be designed
to stand on end, with the axis of the cylindrical portion vertical.
(2) The design service temperature is the coldest temperature for
which a cylinder is suitable. The required design service temperatures
for each cryogenic liquid is as follows:

------------------------------------------------------------------------
Cryogenic liquid Design service temperature
------------------------------------------------------------------------
Argon..................................... Minus 320 deg.F or colder.
Helium.................................... Minus 452 deg.F or colder.
Hydrogen.................................. Minus 42 3 deg.F or colder.
Neon...................................... Minus 411 deg.F or colder.
Nitrogen.................................. Minus 320 deg.F or colder.
Oxygen.................................... Minus 320 deg.F or colder.
------------------------------------------------------------------------

(b) Material. Material use in the construction of this specification
must conform to the following:
(1) Inner containment vessel (cylinder). Designations and limiting
chemical compositions of steel authorized by this specification must be
as shown in table 1 in paragraph (o) of this section.
(2) Outer jacket. Steel or aluminum may be used subject to the
requirements of paragraph (o)(2) of this section.
(c) Identification of material. Material must be identified by any
suitable method.
(d) Manufacture. Cylinders must be manufactured using equipment and
processes adequate to ensure that each cylinder produced conforms to the
requirements of this subpart and to the following requirements:
(1) No defect is permitted that is likely to weaken the finished
cylinder appreciably. A reasonably smooth and uniform surface finish is
required. The shell portion must be a reasonably true cylinder.
(2) The heads must be seamless, concave side to the pressure,
hemispherical or ellipsoidal in shape with the major diameter not more
than twice the minor diameter. Minimum thickness of heads may not be
less than 90 percent of the required thickness of the sidewall. The
heads must be reasonably true to shape, have no abrupt shape changes,
and the skirts must be reasonably true to round.
(3) The surface of the cylinder must be insulated. The insulating
material must be fire resistant. The insulation on non-evacuated jackets
must be covered with a steel jacket not less than 0.060-inch thick or an
aluminum jacket not less than 0.070 inch thick, so constructed that
moisture cannot come in contact with the insulating material. If a
vacuum is maintained in the insulation space, the evacuated jacket must
be designed for a minimum collapsing pressure of 30 psig differential
whether made of steel or aluminum. The construction must be such that
the total heat transfer, from the atmosphere at ambient temperature to
the contents of the cylinder, will not exceed 0.0005 Btu per hour, per
Fahrenheit degree differential in temperature, per pound of water
capacity of the cylinder. For hydrogen, cryogenic liquid service, the
total heat transfer, with a temperature differential of 520 Fahrenheit
degrees, may not exceed that required to vent 30 SCF of hydrogen gas per
hour.
(4) For a cylinder having a design service temperature colder than
minus 320 deg.F, a calculation of the maximum weight of contents must
be made and that weight must be marked on the cylinder as prescribed in
Sec. 178.35.
(5) Welding procedures and operations must be qualified in
accordance with CGA Pamphlet C-3 (incorporated by reference; see
Sec. 171.7 of this subchapter). In addition, an impact test of the weld
must be performed in accordance with paragraph (l) of this section as
part of the qualification of each welding procedure and operator.
(e) Welding. Welding of the cylinder must be as follows:
(1) All seams of the cylinder must be fusion welded. A means must be
provided for accomplishing complete penetration of the joint. Only butt
or joggle butt joints for the cylinder seams are authorized. All joints
in the cylinder must have reasonably true alignment.
(2) All attachments to the sidewalls and heads of the cylinder must
be by fusion welding and must be of a weldable material complying with
the impact requirements of paragraph (l) of this section.
(3) For welding the cylinder, each procedure and operator must be
qualified in accordance with the sections of CGA Pamphlet C-3
(incorporated by reference; see Sec. 171.7 of this subchapter)

[[Page 812]]

that apply. In addition, impact tests of the weld must be performed in
accordance with paragraph (l) of this section as part of the
qualification of each welding procedure and operator.
(4) Brazing, soldering and threading are permitted only for joints
not made directly to the cylinder body. Threads must comply with the
requirements of paragraph (h) of this section.
(f) Wall thickness. The minimum wall thickness of the cylinder must
be such that the calculated wall stress at the minimum required test
pressure may not exceed the least value of the following:
(1) 45,000 psi.
(2) One-half of the minimum tensile strength across the welded seam
determined in paragraph (l) of this section.
(3) One-half of the minimum tensile strength of the base metal
determined as required in paragraph (j) of this section.
(4) The yield strength of the base metal determined as required in
paragraph (l) of this section.
(5) Further provided that wall stress for cylinders having
longitudinal seams may not exceed 85 percent of the above value,
whichever applies.
(6) Calculation must be made by the following formula:

S = [P(1.3D² + 0.4d²)] / (D² -
d²)

where:

S = wall stress in pounds psi;
P = minimum test pressure prescribed for pressure test in psig;
D = outside diameter in inches;
d = inside diameter in inches.

(g) Heat treatment. Heat treatment is not permitted.
(h) Openings in cylinder. Openings in cylinders must conform to the
following:
(1) Openings are permitted in heads only. They must be circular and
may not exceed 3 inches in diameter or one third of the cylinder
diameter, whichever is less. Each opening in the cylinder must be
provided with a fitting, boss or pad, either integral with, or securely
attached to, the cylinder body by fusion welding. Attachments to a
fitting, boss or pad may be made by welding, brazing, mechanical
attachment, or threading.
(2) Threads must comply with the following:
(i) Threads must be clean-cut, even, without checks and cut to
gauge.
(ii) Taper threads to be of a length not less than that specified
for NPT.
(iii) Straight threads must have at least 4 engaged threads, tight
fit and calculated shear strength at least 10 times the test pressure of
the cylinder. Gaskets, which prevent leakage and are inert to the
hazardous material, are required.
(i) Pressure test. Each cylinder, before insulating and jacketing,
must be examined under a pressure of at least 2 times the service
pressure maintained for at least 30 seconds without evidence of leakage,
visible distortion or other defect. The pressure gauge must permit
reading to an accuracy of 1 percent.
(j) Physical test. A physical test must be conducted to determine
yield strength, tensile strength, and elongation as follows:
(1) The test is required on 2 specimens selected from material of
each heat and in the same condition as that in the completed cylinder.
(2) Specimens must conform to the following:
(i) A gauge length of 8 inches with a width not over 1\1/2\ inches,
a gauge length of 2 inches with width not over 1\1/2\ inches, or a gauge
length at least 24 times thickness with a width not over 6 times
thickness (authorized when cylinder wall is not over \1/16\ inch thick).
(ii) The specimen, exclusive of grip ends, may not be flattened.
Grip ends may be flattened to within one inch of each end of the reduced
section.
(iii) When size of the cylinder does not permit securing straight
specimens, the specimens may be taken in any location or direction and
may be straightened or flattened cold by pressure only, not by blows.
When specimens are so taken and prepared, the inspector's report must
show in connection with record of physical tests detailed information in
regard to such specimens.
(iv) Heating of a specimen for any purpose is not authorized.
(3) The yield strength in tension must be the stress corresponding
to a permanent strain of 0.2 percent of the gauge length. The following
conditions apply:

[[Page 813]]

(i) The yield strength must be determined by either the ``offset''
method or the ``extension under load'' method as prescribed in ASTM E 8
(incorporated by reference; see Sec. 171.7 of this subchapter).
(ii) In using the ``extension under load'' method, the total strain
(or ``extension under load''), corresponding to the stress at which the
0.2 percent permanent strain occurs may be determined with sufficient
accuracy by calculating the elastic expansion of the gauge length under
appropriate load and adding thereto 0.2 percent of the gauge length.
Elastic extension calculations must be based on the elastic modulus of
the material used. In the event of controversy, the entire stress-strain
diagram must be plotted and the yield strength determined from the 0.2
percent offset.
(iii) For the purpose of strain measurement, the initial strain
reference must be set while the specimen is under a stress of 12,000 psi
and the strain indicator reading being set at the calculated
corresponding strain.
(iv) Cross-head speed of the testing machine may not exceed \1/8\
inch per minute during yield strength determination.
(k) Acceptable results for physical tests. Physical properties must
meet the limits specified in paragraph (o)(1), table 1, of this section,
for the particular steel in the annealed condition. The specimens must
show at least a 20 percent elongation for a 2-inch gage length. Except
that the percentage may be reduced numerically by 2 for each 7,500 psi
increment of tensile strength above 100,000 psi to a maximum of 5 such
increments. Yield strength and tensile strength must meet the
requirements of paragraph (o)(1), table 1, of this section.
(l) Tests of welds. Welds must be tested as follows:
(1) Tensile test. A specimen must be cut from one cylinder of each
lot of 200 or less, or welded test plate. The welded test plate must be
of one of the heats in the lot of 200 or less which it represents, in
the same condition and approximately the same thickness as the cylinder
wall except that it may not be of a lesser thickness than that required
for a quarter size Charpy impact specimen. The weld must be made by the
same procedures and subjected to the same heat treatment as the major
weld on the cylinder. The specimen must be taken across the major seam
and must be prepared in accordance with and must meet the requirements
of CGA Pamphlet C-3 (incorporated by reference; see Sec. 171.7 of this
subchapter). Should this specimen fail to meet the requirements,
specimens may be taken from two additional cylinders or welded test
plates from the same lot and tested. If either of the latter specimens
fails to meet the requirements, the entire lot represented must be
rejected.
(2) Guided bend test. A ``root'' bend test specimen must be cut from
the cylinder or welded test plate, used for the tensile test specified
in paragraph (l)(1) of this section and from any other seam or
equivalent welded test plate if the seam is welded by a procedure
different from that used for the major seam. Specimens must be taken
across the particular seam being tested and must be prepared and tested
in accordance with and must meet the requirements of CGA Pamphlet C-3
(incorporated by reference; see Sec. 171.7 of this subchapter).
(3) Alternate guided-bend test. This test may be used and must be as
specified in CGA Pamphlet C-3 (incorporated by reference; see Sec. 171.7
of this subchapter). The specimen must be bent until the elongation at
the outer surface, adjacent to the root of the weld, between the lightly
scribed gage lines a to b, is at least 20 percent, except that this
percentage may be reduced for steels having a tensile strength in excess
of 100,000 psig, as provided in paragraph (c) of this section.
(4) Impact tests. One set of three impact test specimens (for each
test) must be prepared and tested for determining the impact properties
of the deposited weld metal--
(i) As part of the qualification of the welding procedure.
(ii) As part of the qualification of the operators.
(iii) For each ``heat'' of welding rodor wire used.

[[Page 814]]

(iv) For each 1,000 feet of weld made with the same heat of welding
rod or wire.
(v) All impact test specimens must be of the charpy type, keyhole or
milled U-notch, and must conform in all respects to ASTM E 23
(incorporated by reference; see Sec. 171.7 of this subchapter). Each set
of impact specimens must be taken across the weld and have the notch
located in the weld metal. When the cylinder material thickness is 2.5
mm or thicker, impact specimens must be cut from a cylinder or welded
test plate used for the tensile or bend test specimens. The dimension
along the axis of the notch must be reduced to the largest possible of
10 mm, 7.5 mm, 5 mm or 2.5 mm, depending upon cylinder thickness. When
the material in the cylinder or welded test plate is not of sufficient
thickness to prepare 2.5 mm impact test specimens, 2.5 mm specimens must
be prepared from a welded test plate made from \1/8\ inch thick material
meeting the requirements specified in paragraph (o)(1), table 1, of this
section and having a carbon analysis of .05 minimum, but not necessarily
from one of the heats used in the lot of cylinders. The test piece must
be welded by the same welding procedure as used on the particular
cylinder seam being qualified and must be subjected to the same heat
treatment.
(vi) Impact test specimens must be cooled to the design service
temperature. The apparatus for testing the specimens must conform to
requirements of ASTM Standard E 23 (incorporated by reference; see
Sec. 171.7 of this subchapter). The test piece, as well as the handling
tongs, must be cooled for a length of time sufficient to reach the
service temperature. The temperature of the cooling device must be
maintained within a range of plus or minus 3 deg.F. The specimen must
be quickly transferred from the cooling device to the anvil of the
testing machine and broken within a time lapse of not more than six
seconds.
(vii) The impact properties of each set of impact specimens may not
be less than the values in the following table:

------------------------------------------------------------------------
Minimum
impact Minimum
value impact
required value
for avg. permitted
Size of specimen of each on one
set of only of a
three set of
specimens three
(ft.-lb.) (ft.-lb.)
------------------------------------------------------------------------
10 mmx10 mm....................................... 15 10
10 mmx7.5 mm...................................... 12.5 8.5
10 mmx5 mm........................................ 10 7.0
10 mmx2.5 mm...................................... 5 3.5
------------------------------------------------------------------------

(viii) When the average value of the three specimens equals or
exceeds the minimum value permitted for a single specimen and the value
for more than one specimen is below the required average value, or when
the value for one specimen is below the minimum value permitted for a
single specimen, a retest of three additional specimens must be made.
The value of each of these retest specimens must equal or exceed the
required average value. When an erratic result is caused by a defective
specimen, or there is uncertainty in test procedure, a retest is
authorized.
(m) Radiographic examination. Cylinders must be subject to a
radiographic examination as follows:
(1) The techniques and acceptability of radiographic inspection must
conform to the standards set forth in CGA Pamphlet C-3 (incorporated by
reference; see Sec. 171.7 of this subchapter).
(2) One finished longitudinal seam must be selected at random from
each lot of 100 or less successively produced and be radiographed
throughout its entire length. Should the radiographic examination fail
to meet the requirements of paragraph (m)(1) of this section, two
additional seams of the same lot must be examined, and if either of
these fail to meet the requirements of (m)(1) of this section, only
those passing are acceptable.
(n) Rejected cylinders. Reheat treatment of rejected cylinders is
authorized. Subsequent thereto, cylinders must pass all prescribed tests
to be acceptable. Welds may be repaired by suitable methods of fusion
welding.
(o) Authorized materials of construction. Authorized materials of
construction are as follows:

[[Page 815]]

(1) Inner containment vessel (cylinder). Electric furnace steel of
uniform quality must be used. Chemical analysis must conform to ASTM A
240/A 240M (incorporated by reference; see Sec. 171.7 of this
subchapter), Type 304 stainless steel. Chemical analysis must conform to
ASTM A240, Type 304 Stainless Steel. A heat of steel made under table 1
and table 2 in this paragraph (o)(1) is acceptable, even though its
check chemical analysis is slightly out of the specified range, if it is
satisfactory in all other respects, provided the tolerances shown in
table 3 in this paragraph (o)(1) are not exceeded. The following
chemical analyses and physical properties are authorized:

Table 1--Authorized Materials
------------------------------------------------------------------------
Chemical analysis, limits in
Designation percent
------------------------------------------------------------------------
Carbon \1\............................. 0.08 max.
Manganese.............................. 2.00 max.
Phosphorus............................. 0.045 max.
Sulphur................................ 0.030 max.
Silicon................................ 1.00 max.
Nickel................................. 8.00-10.50.
Chromium............................... 18.00-20.00.
Molybdenum............................. None.
Titanium............................... None.
Columbium.............................. None.
------------------------------------------------------------------------
\1\ The carbon analysis must be reported to the nearest hundredth of one
percent.

Table 2--Physical Properties
------------------------------------------------------------------------
Physical
properties
(annealed)
------------------------------------------------------------------------
Tensile strength, p.s.i. (minimum).......................... 75,000
Yield strength, p.s.i. (minimum)............................ 30,000
Elongation in 2 inches (minimum) percent.................... 30.0
Elongation other permissible gauge lengths (minimum) percent 15.0
------------------------------------------------------------------------

Table 3--Check Analysis Tolerances
----------------------------------------------------------------------------------------------------------------
Tolerance
over the
maximum
Elements Limit or specified range (percent) limit or
under the
minimum
limit
----------------------------------------------------------------------------------------------------------------
Carbon............................... To 0.030, incl............................................. 0.005
Over 0.30 to 0.20, incl.................................... 0.01
Manganese............................ To 1.00 incl............................................... .03
Over 1.00 to 3.00, incl.................................... 0.04
Phosphorus \1\....................... To 0.040, incl............................................. 0.005
Over 0.040 to 0.020 incl................................... 0.010
Sulphur.............................. To .40 incl................................................ 0.005
Silicon.............................. To 1.00, incl.............................................. 0.05
Nickel............................... Over 5.00 to 10.00, incl................................... 0.10
Over 10.00 to 20.00, incl.................................. 0.15
Chromium............................. Over 15.00 to 20.00, incl.................................. 0.20
----------------------------------------------------------------------------------------------------------------
\1\ Rephosphorized steels not subject to check analysis for phosphorus.

(2) Outer jacket. (i) Nonflammable cryogenic liquids. Cylinders
intended for use in the transportation of nonflammable cryogenic liquid
must have an outer jacket made of steel or aluminum.
(ii) Flammable cryogenic liquids. Cylinders intended for use in the
transportation of flammable cryogenic liquid must have an outer jacket
made of steel.
(p) Markings. (1) Markings must be stamped plainly and permanently
on shoulder or top head of jacket or on a permanently attached plate or
head protective ring.
(2) The letters ``ST'', followed by the design service temperature
(for example, ST-423F), must be marked on cylinders having a design
service temperature of colder than minus 320 deg.F only. Location to be
just below the DOT mark.
(3) The maximum weight of contents, in pounds (for example, ``Max.
Content 51 ''), must be marked on cylinders having a design
service temperature colder than minus 320 deg.F only. Location to be
near symbol.
(4) Special orientation instructions must be marked on the cylinder
(for example, THIS END UP), if the cylinder is used in an orientation
other

[[Page 816]]

than vertical with openings at the top of the cylinder.
(5) If the jacket of the cylinder is constructed of aluminum, the
letters ``AL'' must be marked after the service pressure marking.
Example: DOT-4L150 AL.
(6) Except for serial number and jacket material designation, each
marking prescribed in this paragraph (p) must be duplicated on each
cylinder by any suitable means.
(q) Inspector's report. In addition to the information required by
Sec. 178.35, the inspector's reports must contain information on:
(1) The jacket material and insulation type;
(2) The design service temperature

( deg.F); and
(3) The impact test results, on a lot basis.

[Amdt. 178-114, 61 FR 25942, May 23, 1996, as amended at 66 FR 45386-
45388, Aug. 28, 2001; 67 FR 51653, Aug. 8, 2002]