[Code of Federal Regulations]
[Title 49, Volume 2]
[Revised as of October 1, 2005]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR178.47]
[Page 833-835]
TITLE 49--TRANSPORTATION
CHAPTER I--PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION,
DEPARTMENT OF TRANSPORTATION
PART 178_SPECIFICATIONS FOR PACKAGINGS--Table of Contents
Subpart C_Specifications for Cylinders
Sec. 178.47 Specification 4DS welded stainless steel cylinders for
aircraft use.
(a) Type, size, and service pressure. A DOT 4DS cylinder is either a
welded stainless steel sphere (two seamless hemispheres) or
circumferentially welded cylinder both with a water capacity of not over
100 pounds and a service pressure of at least 500 but not over 900 psig.
(b) Steel. Types 304, 321 and 347 stainless steel are authorized
with proper welding procedure. A heat of steel made under the
specifications in table 1 in this paragraph (b), check chemical analysis
of which is slightly out of the specified range, is acceptable, if
satisfactory in all other respects, provided the tolerances shown in
table 2 in this paragraph (b) are not exceeded, except as approved by
Associate Administrator. The following chemical analyses are authorized:
Table 1--Authorized Materials
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Stainless steels
----------------------------------------------------------------------------
304 (percent) 321 (percent) 347 (percent)
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Carbon (max)....................... 0.08 0.08 0.08
Manganese (max).................... 2.00 2.00 2.00
Phosphorus (max)................... .030 .030 .030
Sulphur (max)...................... .030 .030 .030
Silicon (max)...................... .75 .75 .75
Nickel............................. 8.0/11.0 9.0/13.0 9.0/13.0
Chromium........................... 18.0/20.0 17.0/20.0 17.0/20.0
Molybdenum
Titanium........................... .......................... (\1\)
Columbium.......................... .......................... .......................... (\2\)
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\1\ Titanium may not be more than 5C and not more than 0.60%.
\2\ Columbium may not be less than 10C and not more than 1.0%.
Table 2--Check Analysis Tolerances
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Tolerance (percent) over
the maximum limit or
under the minimum limit
Element Limit or maximum specified (percent) -------------------------
Under Over
minimum maximum
limit limit
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Carbon......................... To 0.15 incl......................................... 0.01 0.01
Manganese...................... Over 1.15 to 2.50 incl............................... 0.05 0.05
Phosphorus\1\.................. All ranges........................................... ........... .01
Sulphur........................ All ranges........................................... ........... .01
Silicon........................ Over 0.30 to 1.00 incl............................... .05 .05
Nickel......................... Over 5.30 to 10.00 incl.............................. .10 .10
Over 10.00 to 14.00 incl............................. .15 .15
Chromium....................... Over 15.00 to 20.00 incl............................. .20 .20
[[Page 834]]
Titanium....................... All ranges........................................... .05 .05
Columbium...................... All ranges........................................... .05 .05
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\1\Rephosphorized steels not subject to check analysis for phosphorus.
(c) Identification of material. Materials 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. No defect is permitted that is likely to
weaken the finished cylinder appreciably, a reasonably smooth and
uniform surface finish is required. No abrupt change in wall thickness
is permitted. Welding procedures and operators must be qualified in
accordance with CGA Pamphlet C-3 (IBR, see Sec. 171.7 of this
subchapter). All seams of the sphere or cylinder must be fusion welded.
Seams must be of the butt type and means must be provided for
accomplishing complete penetration of the joint.
(e) Attachments. Attachments to the container are authorized by
fusion welding provided that such attachments are made of weldable
stainless steel in accordance with paragraph (b) of this section.
(f) Wall thickness. The minimum wall thickness must be such that the
wall stress at the minimum specified test pressure may not be over
60,000 psig. A minimum wall thickness of 0.040 inch is required for any
diameter container. Calculations must be made by the following formulas:
(1) Calculation for sphere must be made by the formula:
S = PD / 4tE
Where:
S = Wall stress in psi;
P = Test pressure prescribed for water jacket test, i.e., at least two
times service pressure, in psig;
D = Outside diameter in inches;
t = Minimum wall thickness in inches;
E = 0.85 (provides 85 percent weld efficiency factor which must be
applied in the girth weld area and heat zones which zone must extend a
distance of 6 times wall thickness from center of weld);
E = 1.0 (for all other areas).
(2) Calculation for a cylinder must be made by the formula:
S = [P(1.3D2 + 0.4d2)] / (D2 -
d2)
Where:
S = Wall stress in psi;
P = Test pressure prescribed for water jacket test, i.e., at least two
times service pressure, in psig;
D = Outside diameter in inches;
d = Inside diameter in inches.
(g) Heat treatment. The seamless hemispheres and cylinders may be
stress relieved or annealed for forming. Welded container must be stress
relieved at a temperature of 775 [deg]F 25[deg]
after process treatment and before hydrostatic test.
(h) Openings in container. Openings must comply with the following:
(1) Each opening in the container must be provided with a fitting,
boss or pad of weldable stainless steel securely attached to the
container by fusion welding.
(2) Attachments to a fitting, boss, or pad must be adequate to
prevent leakage. Threads must comply with the following:
(i) Threads must be clean cut, even, without checks, and tapped to
gauge.
(ii) Taper threads to be of length not less than as specified for
American Standard taper pipe threads.
(iii) Straight threads having at least 4 engaged threads, to have
tight fit and calculated shear strength at least 10 times the test
pressure of the container; gaskets required, adequate to prevent
leakage.
(i) Process treatment. Each container must be hydraulically
pressurized in a water jacket to at least 100 percent, but not more than
110 percent, of the test pressure and maintained at this
[[Page 835]]
pressure for a minimum of 3 minutes. Total and permanent expansion must
be recorded and included in the inspector's report.
(j) Hydrostatic test. Each cylinder must successfully withstand a
hydrostatic test as follows:
(1) The test must be by water-jacket, operated so as to obtain
accurate data. The pressure gauge must permit reading to an accuracy of
1 percent. The expansion gauge must permit reading of total expansion to
an accuracy either of 1 percent or 0.1 cubic centimeter.
(2) Pressure must be maintained for at least 30 seconds and
sufficiently longer to ensure complete expansion. If, due to failure of
the test apparatus, the test pressure cannot be maintained, the test may
be repeated at a pressure increased by 10 percent or 100 psig, whichever
is the lower.
(3) Permanent volumetric expansion may not exceed 10 percent of
total volumetric expansion at test pressure.
(4) Each container must be tested to at least 2 times service
pressure.
(5) Container must then be inspected. Any wall thickness lower than
that required by paragraph (f) of this section must be cause for
rejection. Bulges and cracks must be cause for rejection. Welded joint
defects exceeding requirements of paragraph (k) of this section must be
cause for rejection.
(k) Radiographic inspection. Radiographic inspection is required on
all welded joints which are subjected to internal pressure, except that
at the discretion of the disinterested inspector, openings less than 25
percent of the container diameter need not be subjected to radiographic
inspection. Evidence of any defects likely to seriously weaken the
container is cause for rejection. Radiographic inspection must be
performed subsequent to the hydrostatic test.
(l) Burst test. One container taken at random out of 200 or less
must be hydrostatically tested to destruction. Rupture pressure must be
included as part of the inspector's report.
(m) Flattening test. A flattening test must be performed as follows:
(1) For spheres the test must be at the weld between parallel steel
plates on a press with welded seam at right angles to the plates. Test
one sphere taken at random out of each lot of 200 or less after the
hydrostatic test. Any projecting appurtenances may be cut off (by
mechanical means only) prior to crushing.
(2) For cylinders the test must be between knife edges, wedge
shaped, 60[deg] angle, rounded to \1/2\-inch radius. Test one cylinder
taken at random out of each lot of 200 or less, after the hydrostatic
test.
(n) Acceptable results for flattening and burst tests. Acceptable
results for flattening and burst tests are as follows:
(1) Flattening required to 50 percent of the original outside
diameter without cracking.
(2) Burst pressure must be at least 3 times the service pressure.
(o) Rejected containers. Repair of welded seams by welding prior to
process treatment is authorized. Subsequent thereto, containers must be
heat treated and pass all prescribed tests.
(p) Duties of inspector. In addition to the requirements of Sec.
178.35, the inspector must verify that all tests are conducted at
temperatures between 60 [deg]F and 90 [deg]F.
(q) Marking. Markings must be stamped plainly and permanently on a
permanent attachment or on a metal nameplate permanently secured to the
container by means other than soft solder.
[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; 68 FR 75748, Dec. 31,
2003]