[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: 49CFR178.55]



[Page 845-848]

 

                        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. 178.55  Specification 4B240ET welded or brazed cylinders.



    (a) Type, spinning process, size and service pressure. A DOT 4B240ET 

cylinder is a brazed type cylinder made from electric resistance welded 

tubing. The maximum water capacity of this cylinder is 12 pounds or 333 

cubic inches and the service must be 240 psig. The maximum outside 

diameter of the shell must be five inches and maximum length of the 

shell is 21 inches. Cylinders closed in by a spinning process are 

authorized.

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

quality must be used. Plain carbon steel content may not exceed the 

following: Carbon, 0.25; phosphorus, 0.045; sulfur, 0.050. The addition 

of other elements for alloying effect is prohibited.

    (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. No defect is permitted that is likely to 

weaken the finished cylinder appreciably. A reasonably smooth and 

uniform surface finish is required. Heads may be attached to shells by 

lap brazing or may be formed integrally. The thickness of the bottom of 

cylinders welded or formed by spinning is, under no condition, to be 

less than two times the minimum wall thickness of the cylindrical shell. 

Such bottom thicknesses must be measured within an area bounded by a 

line representing the points of contact



[[Page 846]]



between the cylinder and the floor when the cylinder is in a vertical 

position. Seams must conform to the following:

    (1) Circumferential seams must be by brazing only. Heads must be 

attached to shells by the lap brazing method and must overlap not less 

than four times the wall thickness. Brazing material must have a melting 

point of not less than 1000 [deg]F. Heads 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 of the joint by the brazing material is secured. Brazed 

joints may be repaired by brazing.

    (2) Longitudinal seams in shell must be by electric resistance 

welded joints only. No repairs to longitudinal joints is permitted.

    (3) Welding procedures and operators must be qualified in accordance 

with CGA C-3 (IBR, see Sec. 171.7 of this subchapter).

    (e) Welding or brazing. Only the attachment, by welding or brazing, 

to the tops and bottoms of cylinders of neckrings, footrings, handles, 

bosses, pads, and valve protection rings is authorized. Provided that 

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

attached are made of weldable steel, the carbon content of which may not 

exceed 0.25 percent.

    (f) Wall thickness. The wall stress must be at least two times the 

service pressure and may not exceed 18,000 psi. The minimum wall 

thickness is 0.044 inch. Calculation must be made by the following 

formula:



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

    d2)



Where:



S = wall stress in psig;

P = 2 times service pressure;

D = outside diameter in inches;

d = inside diameter in inches.



    (g) Heat treatment. Heads formed by drawing or pressing must be 

uniformly and properly heat treated prior to tests. Cylinders with 

integral formed heads or bases must be subjected to a normalizing 

operation. Normalizing and brazing operations may be combined, provided 

the operation is carried out at a temperature in excess of the upper 

critical temperature of the steel.

    (h) Openings in cylinders. Openings in cylinders must comply with 

the following:

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

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

cylinder by brazing or by welding or by threads. A 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 calculated shear strength at least 10 times the test 

pressure of the cylinder; gaskets required, adequate to prevent leakage.

    (2) Closure of a fitting, boss, or pad must be adequate to prevent 

leakage.

    (i) Hydrostatic test. Each cylinder must successfully 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 of either 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



[[Page 847]]



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.

    (5) Each 1000 cylinders or less successively produced each day must 

constitute a lot. One cylinder must be selected from each lot and 

hydrostatically tested to destruction. If this cylinder bursts below 

five times the service pressure, then two additional cylinders must be 

selected and subjected to this test. If either of these cylinders fails 

by bursting below five times the service pressure then the entire lot 

must be rejected. All cylinders constituting a lot must be of identical 

size, construction heat-treatment, finish, and quality.

    (j) Flattening test. Following the hydrostatic test, one cylinder 

taken at random out of each lot of 200 or less, must be subjected to a 

flattening test that is between knife edges, wedge shaped, 60[deg] 

angle, rounded to \1/2\ inch radius.

    (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 in the case of cylinders of capacity greater than 86 cubic 

inches and out of each lot of 500 or less for cylinders having a 

capacity of 86 cubic inches or less.

    (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 a width 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 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 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.

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

results for the physical and flattening tests are an elongation of at 

least 40 percent for a 2 inch gauge length or at least 20 percent in 

other cases and a yield strength not over 73 percent of tensile 

strength. In this instance the flattening test is required, without 

cracking, to six times the wall thickness with a weld 90[deg] from



[[Page 848]]



the direction of the applied load. Two rings cut from the ends of length 

of pipe used in production of a lot may be used for the flattening test 

provided the rings accompany the lot which they represent in all thermal 

processing operations. At least one of the rings must pass the 

flattening test.

    (m) Leakage test. All spun cylinders and plugged cylinders must be 

tested for leakage by gas or air pressure after the bottom has been 

cleaned and is free from all moisture, subject to the following 

conditions:

    (1) Pressure, approximately the same as but no less than service 

pressure, must be applied to one side of the finished bottom over an 

area of at least \1/16\ of the total area of the bottom but not less 

than \3/4\ inch in diameter, including the closure, for at least 1 

minute, during which time the other side of the bottom exposed to 

pressure must be covered with water and closely examined for indications 

of leakage. Except as provided in paragraph (n) of this section, 

cylinders which are leaking must be rejected.

    (2) A spun cylinder is one in which an end closure in the finished 

cylinder has been welded by the spinning process.

    (3) A plugged cylinder is one in which a permanent closure in the 

bottom of a finished cylinder has been effected by a plug.

    (4) As a safety precaution, if the manufacturer elects to make this 

test before the hydrostatic test, he should design his apparatus so that 

the pressure is applied to the smallest area practicable, around the 

point of closure, and so as to use the smallest possible volume of air 

or gas.

    (n) Rejected cylinders. Repairs of rejected cylinders is authorized. 

Cylinders that are leaking must be rejected, except that:

    (1) Spun cylinders rejected under the provisions of paragraph (m) of 

this section may be removed from the spun cylinder category by drilling 

to remove defective material, tapping, and plugging.

    (2) Brazed joints may be rebrazed.

    (3) Subsequent to the operations noted in paragraphs (n)(1) and 

(n)(2) of this section, acceptable cylinders must pass all prescribed 

tests.

    (o) Marking. Markings on each cylinder must be by stamping plainly 

and permanently on shoulder, top head, neck or valve protection collar 

which is permanently attached to the cylinders and forming an integral 

part thereof, provided that cylinders not less than 0.090 inch thick may 

be stamped on the side wall adjacent to top head.



[Amdt. 178-114, 61 FR 25942, May 23, 1996, as amended at 66 FR 45386, 

Aug. 28, 2001; 67 FR 51653, Aug. 8, 2002; 68 FR 75748, 75749, Dec. 31, 

2003]