[Code of Federal Regulations]
[Title 49, Volume 2]
[Revised as of October 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR178.45]
[Page 810-814]
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. 178.45 Specification 3T seamless steel cylinder.
(a) Type, size, and service pressure. A DOT 3T cylinder is a
seamless steel cylinder with a minimum water capacity of 1,000 pounds
and a minimum service pressure of 1,800 psig. Each cylinder must have
integrally formed heads concave to pressure at both ends. The inside
head shape must be hemispherical, ellipsoidal in which the major axis is
two times the minor axis, or a dished shape falling within these two
limits. Permanent closures formed by spinning are prohibited.
(b) Material, steel. Only open hearth, basic oxygen, or electric
furnace process steel of uniform quality is authorized. The steel
analysis must conform to the following:
Analysis Tolerances
------------------------------------------------------------------------
Check Analysis
Element Ladle analysis -----------------
Under Over
------------------------------------------------------------------------
Carbon........................... 0.35 to 0.50....... 0.03 0.04
[[Page 811]]
Manganese........................ 0.75 to 1.05....... 0.04 0.04
Phosphorus (max)................. 0.035.............. ....... 0.01
Sulphur (max).................... 0.04............... ....... 0.01
Silicon.......................... 0.15 to 0.35....... 0.02 0.03
Chromium......................... 0.80 to 1.15....... 0.05 0.05
Molybdenum....................... 0.15 to 0.25....... 0.02 0.02
------------------------------------------------------------------------
(1) A heat of steel made under the specifications in the table in
this paragraph (b), the ladle analysis of which is slightly out of the
specified range, is acceptable if satisfactory in all other aspects.
However, the check analysis tolerances shown in the table in this
paragraph (b) may not be exceeded except as approved by the Department.
(2) Material with seams, cracks, laminations, or other injurious
defects is not permitted.
(3) Material used must be identified by any suitable method.
(c) Manufacture. General manufacturing requirements are as follows:
(1) Surface finish must be uniform and reasonably smooth.
(2) Inside surfaces must be clean, dry, and free of loose particles.
(3) No defect of any kind is permitted if it is likely to weaken a
finished cylinder.
(4) If the cylinder surface is not originally free from the defects,
the surface may be machined or otherwise treated to eliminate these
defects provided the minimum wall thickness is maintained.
(5) Welding or brazing on a cylinder is not permitted.
(d) Wall thickness. The minimum wall thickness must be such that the
wall stress at the minimum specified test pressure does not exceed 67
percent of the minimum tensile strength of the steel as determined by
the physical tests required in paragraphs (j) and (k) of this section. A
wall stress of more than 90,500 p.s.i. is not permitted. The minimum
wall thickness for any cylinder may not be less than 0.225 inch.
(1) Calculation of the stress for cylinders must be made by the
following formula:
S = [P(1.3D2 + 0.4d2)] / (D2 -
d2)
Where:
S = Wall stress in psi;
P = Minimum test pressure, at least \5/3\ service pressure;
D = Outside diameter in inches;
d = Inside diameter in inches.
(2) Each cylinder must meet the following additional requirement
which assumes a cylinder horizontally supported at its two ends and
uniformly loaded over its entire length. This load consists of the
weight per inch of length of the straight cylindrical portion filled
with water compressed to the specified test pressure. The wall thickness
must be increased when necessary to meet this additional requirement:
(i) The sum of two times the maximum tensile stress in the bottom
fibers due to bending (see paragraph (d)(2)(ii) of this section), plus
the maximum tensile stress in the same fibers due to hydrostatic testing
(see paragraph (d)(2)(iii) of this section) may not exceed 80 percent of
the minimum yield strength of the steel at this maximum stress.
(ii) The following formula must be used to calculate the maximum
tensile stress due to bending:
S = Mc / I
Where:
S = Tensile stress in psi;
M = Bending moment in inch-pounds (wl2/8);
I = Moment of inertia--0.04909 (D4-d4) in inches
fourth;
c = Radius (D/2) of cylinder in inches;
w = Weight per inch of cylinder filled with water;
l = Length of cylinder in inches;
D = Outside diameter in inches;
d = Inside diameter in inches.
(iii) The following formula must be used to calculate the maximum
longitudinal tensile stress due to hydrostatic test pressure:
S = A1 P / A2
Where:
S = Tensile stress in psi;
A1 = Internal area in cross section of cylinder in square
inches;
P = Hydrostatic test pressure-psig;
A2 = Area of metal in cross section of cylinder in square
inches.
(e) Heat treatment. Each completed cylinder must be uniformly and
properly heat treated prior to testing, as follows:
[[Page 812]]
(1) Each cylinder must be heated and held at the proper temperature
for at least one hour per inch of thickness based on the maximum
thickness of the cylinder and then quenched in a suitable liquid medium
having a cooling rate not in excess of 80 percent of water. The steel
temperature on quenching must be that recommended for the steel
analysis, but it must never exceed 1750 [deg]F.
(2) After quenching, each cylinder must be reheated to a temperature
below the transformation range but not less than 1050 [deg]F., and must
be held at this temperature for at least one hour per inch of thickness
based on the maximum thickness of the cylinder. Each cylinder must then
be cooled under conditions recommended for the steel.
(f) Openings. Openings in cylinders must comply with the following:
(1) Openings are permitted on heads only.
(2) The size of any centered opening in a head may not exceed one
half the outside diameter of the cylinder.
(3) Openings in a head must have ligaments between openings of at
least three times the average of their hole diameter. No off-center
opening may exceed 2.625 inches in diameter.
(4) All openings must be circular.
(5) All openings must be threaded. Threads must be in compliance
with the following:
(i) Each thread must be clean cut, even, without any checks, and to
gauge.
(ii) Taper threads, when used, must be the American Standard Pipe
thread (NPT) type and must be in compliance with the requirements of NBS
Handbook H-28 (IBR, see Sec. 171.7 of this subchapter).
(iii) Taper threads conforming to National Gas Taper thread (NGT)
standards must be in compliance with the requirements of NBS Handbook H-
28.
(iv) Straight threads conforming with National Gas Straight thread
(NGS) standards are authorized. These threads must be in compliance with
the requirements of NBS Handbook H-28.
(g) Hydrostatic test. Each cylinder must be tested at an internal
pressure by the water jacket method or other suitable method, conforming
to the following requirements:
(1) The testing apparatus must be operated in a manner that will
obtain accurate data. Any pressure gauge used must permit reading to an
accuracy of one percent. Any expansion gauge used must permit reading of
the total expansion to an accuracy of one percent.
(2) Any internal pressure applied to the cylinder after heat
treatment and before the official test may not exceed 90 percent of the
test pressure.
(3) The pressure must be maintained sufficiently long to assure
complete expansion of the cylinder. In no case may the pressure be held
less than 30 seconds.
(4) If, due to failure of the test apparatus, the required test
pressure cannot be maintained, the test must be repeated at a pressure
increased by 10 percent or 100 psig, whichever is lower or, the cylinder
must be reheat treated.
(5) Permanent volumetric expansion of the cylinder may not exceed 10
percent of its total volumetric expansion at the required test pressure.
(6) Each cylinder must be tested to at least \5/3\ times its service
pressure.
(h) Ultrasonic examination. After the hydrostatic test, the
cylindrical section of each vessel must be examined in accordance with
ASTM E 213 for shear wave and E 114 for straight beam (IBR, Standard see
Sec. 171.7 of this subchapter). The equipment used must be calibrated
to detect a notch equal to five percent of the design minimum wall
thickness. Any discontinuity indication greater than that produced by
the five percent notch must be cause for rejection of the cylinder,
unless the discontinuity is repaired within the requirements of this
specification.
(i) Basic requirements for tension and Charpy impact tests.
Cylinders must be subjected to a tension and Charpy impact as follows:
(1) When the cylinders are heat treated in a batch furnace, two
tension specimens and three Charpy impact specimens must be tested from
one of the cylinders or a test ring from each batch. The lot size
represented by these tests may not exceed 200 cylinders.
(2) When the cylinders are heat treated in a continuous furnace, two
tension specimens and three Charpy impact
[[Page 813]]
specimens must be tested from one of the cylinders or a test ring from
each four hours or less of production. However, in no case may a test
lot based on this production period exceed 200 cylinders.
(3) Each specimen for the tension and Charpy impact tests must be
taken from the side wall of a cylinder or from a ring which has been
heat treated with the finished cylinders of which the specimens must be
representative. The axis of the specimens must be parallel to the axis
of the cylinder. Each cylinder or ring specimen for test must be of the
same diameter, thickness, and metal as the finished cylinders they
represent. A test ring must be at least 24 inches long with ends covered
during the heat treatment process so as to simulate the heat treatment
process of the finished cylinders it represents.
(4) A test cylinder or test ring need represent only one of the
heats in a furnace batch provided the other heats in the batch have
previously been tested and have passed the tests and that such tests do
not represent more than 200 cylinders from any one heat.
(5) The test results must conform to the requirements specified in
paragraphs (j) and (k) of this section.
(6) When the test results do not conform to the requirements
specified, the cylinders represented by the tests may be reheat treated
and the tests repeated. Paragraph (i)(5) of this section applies to any
retesting.
(j) Basic conditions for acceptable physical testing. The following
criteria must be followed to obtain acceptable physical test results:
(1) Each tension specimen must have a gauge length of two inches
with a width not exceeding one and one-half inches. Except for the grip
ends, the specimen may not be flattened. The grip ends may be flattened
to within one inch of each end of the reduced section.
(2) A specimen may not be heated after heat treatment specified in
paragraph (d) of this section.
(3) The yield strength in tension must be the stress corresponding
to a permanent strain of 0.2 percent of the gage length.
(i) This yield strength must be determined by the ``offset'' method
or the ``extension under load'' method described in ASTM E 8 (IBR, see
Sec. 171.7 of this subchapter).
(ii) For 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 extension of the gage length under
appropriate load and adding thereto 0.2 percent of the gage length.
Elastic extension calculations must be based on an elastic modulus of
30,000,000. However, when the degree of accuracy of this method is
questionable 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 must
be set with the specimen under a stress of 12,000 p.s.i. and the strain
indicator reading set at the calculated corresponding strain.
(iv) The cross-head speed of the testing machine may not exceed \1/
8\ inch per minute during the determination of yield strength.
(4) Each impact specimen must be Charpy V-notch type size 10 mm x 10
mm taken in accordance with paragraph 11 of ASTM A 333 (IBR, see Sec.
171.7 of this subchapter). When a reduced size specimen is used, it must
be the largest size obtainable.
(k) Acceptable physical test results. Results of physical tests must
conform to the following:
(1) The tensile strength may not exceed 155,000 p.s.i.
(2) The elongation must be at least 16 percent for a two-inch gage
length.
(3) The Charpy V-notch impact properties for the three impact
specimens which must be tested at 0 [deg]F may not be less than the
values shown as follows:
------------------------------------------------------------------------
Average value for Minimum value (1
Size of specimen (mm) acceptance (3 specimen only of
specimens) the 3)
------------------------------------------------------------------------
10.0x10.0...................... 25.0 ft. lbs...... 20.0 ft. lbs.
10.0x7.5....................... 21.0 ft. lbs...... 17.0 ft. lbs.
10.0x5.0....................... 17.0 ft. lbs...... 14.0 ft. lbs.
------------------------------------------------------------------------
(4) After the final heat treatment, each vessel must be hardness
tested on the cylindrical section. The tensile strength equivalent of
the hardness
[[Page 814]]
number obtained may not be more than 165,000 p.s.i. (Rc 36). When the
result of a hardness test exceeds the maximum permitted, two or more
retests may be made; however, the hardness number obtained in each
retest may not exceed the maximum permitted.
(l) Rejected cylinders. Reheat treatment is authorized for rejected
cylinders. However, each reheat treated cylinder must subsequently pass
all the prescribed tests. Repair by welding is not authorized.
(m) Markings. Marking must be done by stamping into the metal of the
cylinder. All markings must be legible and located on a shoulder.
(n) Inspector's report. In addition to the requirements of Sec.
178.35, the inspector's report for the physical test report, must
indicate the average value for three specimens and the minimum value for
one specimen for each lot number.
[Amdt. 178-114, 61 FR 25942, May 23, 1996, as amended at 66 FR 45385,
43588, Aug. 28, 2001; 67 FR 51652, Aug. 8, 2002; 68 FR 48571, Aug. 14,
2003; 68 FR 75748, 75749, Dec. 31, 2003]