[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: 49CFR178.50]



[Page 835-838]

 

                        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. 178.50  Specification 4B welded or brazed steel cylinders.



    (a) Type, size, and service pressure. A DOT 4B is a welded or brazed 

steel cylinder with longitudinal seams that are forged lap-welded or 

brazed and with water capacity (nominal) not over 1,000 pounds and a 

service pressure of at least 150 but not over 500 psig. Cylinders closed 

in by spinning process are not authorized.

    (b) Steel. Open-hearth, electric or basic oxygen process steel of 

uniform quality must be used. Content percent may not exceed the 

following: Carbon, 0.25; phosphorus, 0.045; sulphur, 0.050.

    (c) Identification of material. Material must be identified by any 

suitable method except that plates and billets



[[Page 836]]



for hotdrawn cylinders must be marked with the heat number.

    (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. Exposed bottom welds on cylinders 

over 18 inches long must be protected by footrings. Welding procedures 

and operators must be qualified in accordance with CGA Pamphlet C-3 

(IBR, see Sec. 171.7 of this subchapter). Seams must be made as 

follows:

    (1) Welded or brazed circumferential seams. Heads attached by 

brazing must have a driving fit with the shell, unless the shell is 

crimped, swedged, or curled over the skirt or flange of the head, and be 

thoroughly brazed until complete penetration by the brazing material of 

the brazed joint is secured. Depth of brazing from end of shell must be 

at least four times the thickness of shell metal.

    (2) Longitudinal seams in shells. Longitudinal seams must be forged 

lap welded, by copper brazing, by copper alloy brazing, or by silver 

alloy brazing. Copper alloy composition must be: Copper, 95 percent 

minimum; Silicon, 1.5 percent to 3.85 percent; Manganese, 0.25 percent 

to 1.10 percent. The melting point of the silver alloy brazing material 

must be in excess of 1000 [deg]F. When brazed, the plate edge must be 

lapped at least eight times the thickness of plate, laps being held in 

position, substantially metal to metal, by riveting or electric spot-

welding; brazing must be done by using a suitable flux and by placing 

brazing material on one side of seam and applying heat until this 

material shows uniformly along the seam of the other side.

    (e) Welding or brazing. Only the attachment of neckrings, footrings, 

handles, bosses, pads, and valve protection rings to the tops and 

bottoms of cylinders by welding or brazing is authorized. Such 

attachments and the portion of the container to which they are attached 

must be made of weldable steel, the carbon content of which may not 

exceed 0.25 percent except in the case of 4130X steel which may be used 

with proper welding procedure.

    (f) Wall thickness. The wall thickness of the cylinder must comply 

with the following requirements:

    (1) For cylinders with outside diameters over 6 inches the minimum 

wall thickness must be 0.090 inch. In any case, the minimum wall 

thickness must be such that calculated wall stress at minimum test 

pressure (paragraph (i)(4) of this section) may not exceed the following 

values:

    (i) 24,000 psi for cylinders without longitudinal seam.

    (ii) 22,800 psig for cylinders having copper brazed or silver alloy 

brazed longitudinal seam.

    (iii) 18,000 psi for cylinders having forged lapped welded 

longitudinal seam.

    (2) Calculation must be made by the formula:



S = [P(1.3D2 + 0.4d2)] / (D2 - 

    d2)



Where:



S = wall stress in psi;

P = minimum test pressure prescribed for water jacket test or 450 psig 

whichever is the greater;

D = outside diameter in inches;

d = inside diameter in inches.



    (g) Heat treatment. Cylinder body and heads, formed by drawing or 

pressing, must be uniformly and properly heat treated prior to tests.

    (h) Opening in cylinders. Openings in cylinders must conform to the 

following:

    (1) Each opening in cylinders, except those for safety devices, must 

be provided with a fitting, boss, or pad, securely attached to cylinder 

by brazing or by welding or by threads. Fitting, boss, or pad must be of 

steel suitable for the method of attachment employed, and which need not 

be identified or verified as to analysis except that if attachment is by 

welding, carbon content may not exceed 0.25 percent. If threads are 

used, they 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



[[Page 837]]



calculated shear strength at least 10 times the test pressure of the 

cylinder; gaskets required, adequate to prevent leakage.

    (iv) A brass fitting may be brazed to the steel boss or flange on 

cylinders used as component parts of hand fire extinguishers.

    (2) The closure of a fitting, boss, or pad must be adequate to 

prevent leakage.

    (i) Hydrostatic test. Cylinders must withstand a hydrostatic test as 

follows:

    (1) The test must be by water-jacket, or other suitable method, 

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. Any internal pressure 

applied after heat-treatment and previous to the official test may not 

exceed 90 percent of the test pressure. 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) Cylinders must be tested as follows:

    (i) At least one cylinder selected at random out of each lot of 200 

or less must be tested as outlined in paragraphs (i)(1), (i)(2), and 

(i)(3) of this section to at least two times service pressure.

    (ii) All cylinders not tested as outlined in paragraph (i)(4)(i) of 

this section must be examined under pressure of at least two times 

service pressure and show no defect.

    (j) Flattening test. After the hydrostatic test, a flattening test 

must be performed on one cylinder taken at random out or each lot of 200 

or less, by placing the cylinder between wedge shaped knife edges having 

a 60[deg] included angle, rounded to \1/2\-inch radius. The longitudinal 

axis of the cylinder must be at a 90-degree angle to knife edges during 

the test. For lots of 30 or less, flattening tests are authorized to be 

made on a ring at least 8 inches long cut from each cylinder and 

subjected to same heat treatment as the finished cylinder.

    (k) Physical test. A physical test must be conducted to determine 

yield strength, tensile strength, elongation, and reduction of area of 

material as follows:

    (1) The test is required on 2 specimens cut from 1 cylinder, or part 

thereof heat-treated as required, taken at random out of each lot of 200 

or less. For lots of 30 or less, physical tests are authorized to be 

made on a ring at least 8 inches long cut from each cylinder and 

subjected to same heat treatment as the finished cylinder.

    (2) Specimens must conform to the following:

    (i) A gauge length of 8 inches with a width of not over 1\1/2\ 

inches, a gauge length of 2 inches with a width of not over 1\1/2\ 

inches, or a gauge length at least 24 times the thickness with a width 

not over 6 times the thickness is authorized when a cylinder wall is not 

over \3/16\ 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 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:

    (i) The yield strength must be determined by either the ``offset'' 

method or the ``extension under load'' method as prescribed in ASTM E 8 

(IBR, see Sec. 171.7 of this subchapter).

    (ii) In using the ``extension under load'' method, the total strain 

(or ``extension under load'') corresponding to



[[Page 838]]



the stress at which the 0.2 percent permanent strain occurs may be 

determined with sufficient accuracy by calculating the elastic extension 

of the gauge length under appropriate load and adding thereto 0.2 

percent of the gauge length. Elastic extension calculations must be 

based on an elastic modulus of 30,000,000. 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 must 

be set while the specimen is under a stress of 12,000 psi, and strain 

indicator reading must be 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.

    (l) Acceptable results for physical and flattening tests. Either of 

the following is an acceptable result:

    (1) An elongation of at least 40 percent for a 2-inch gauge length 

or at least 20 percent in other cases and yield strength not over 73 

percent of tensile strength. In this instance, a flattening test is not 

required.

    (2) When cylinders are constructed of lap welded pipe, flattening 

test is required, without cracking, to 6 times the wall thickness. In 

such case, the rings (crop ends) cut from each end of pipe, must be 

tested with the weld 45[deg] or less from the point of greatest stress. 

If a ring fails, another from the same end of pipe may be tested.

    (m) Rejected cylinders. Reheat treatment is authorized for rejected 

cylinder. Subsequent thereto, cylinders must pass all prescribed tests 

to be acceptable. Repair of brazed seams by brazing and welded seams by 

welding is authorized.

    (n) Markings. Markings must be stamped plainly and permanently in 

any of the following locations on the cylinder:

    (1) On shoulders and top heads when they are not less than 0.087-

inch thick.

    (2) On side wall adjacent to top head for side walls which are not 

less than 0.090 inch thick.

    (3) On a cylindrical portion of the shell which extends beyond the 

recessed bottom of the cylinder, constituting an integral and non-

pressure part of the cylinder.

    (4) On a metal plate attached to the top of the cylinder or 

permanent part thereof; sufficient space must be left on the plate to 

provide for stamping at least six retest dates; the plate must be at 

least \1/16\-inch thick and must be attached by welding, or by brazing. 

The brazing rod must melt at a temperature of 1100 [deg]F. Welding or 

brazing must be along all the edges of the plate.

    (5) On the neck, neckring, valve boss, valve protection sleeve, or 

similar part permanently attached to the top of the cylinder.

    (6) On the footring permanently attached to the cylinder, provided 

the water capacity of the cylinder does not exceed 25 pounds.



[Amdt. 178-114, 61 FR 25942, May 23, 1996, as amended at 62 FR 51561, 

Oct. 1, 1997; 66 FR 45385, 45388, Aug. 28, 2001; 67 FR 51653, Aug. 8, 

2002; 68 FR 75748, Dec. 31, 2003]