[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: 49CFR178.38]



[Page 816-819]

 

                        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. 178.38  Specification 3B seamless steel cylinders.



    (a) Type, size, and service pressure. A DOT 3B cylinder is seamless 

steel cylinder with a water capacity (nominal) of not over 1,000 pounds 

and a service pressure of at least 150 to not over 500 psig.

    (b) Steel. Open-hearth or electric steel of uniform quality must be 

used. Content percent may not exceed the following: carbon, 0.55; 

phosphorus, 0.045; sulphur, 0.050.

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

suitable method except that plates and billets for hot-drawn 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 fissure or other defect is permitted 

that is likely to weaken the finished cylinder appreciably. A reasonably 

smooth and uniform surface finish is required. If not originally free 

from such defects, the surface may be machined or otherwise treated to 

eliminate these defects. The thickness of the bottoms 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 to be measured within an area bounded by a line representing 

the points of contact between the cylinder and floor when the cylinder 

is in a vertical position.

    (e) Welding or brazing. Welding or brazing for any purpose 

whatsoever is prohibited except as follows:

    (1) Welding or brazing is authorized for the attachment of neckrings 

and



[[Page 817]]



footrings which are non-pressure parts, and only to the tops and bottoms 

of cylinders having a service pressure of 500 psig or less. Cylinders, 

neckrings, and footrings must be made of weldable steel, 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.

    (2) As permitted in paragraph (d) of this section.

    (f) Wall thickness. The wall stress may not exceed 24,000 psi. The 

minimum wall thickness is 0.090 inch for any cylinder with an outside 

diameter of 6 inches. Calculation must be made by the following formula:



S = [P(1.3D\2\+0.4d\2\)]/(D\2\-d\2\)



Where:



S = wall stress in psi;

P = at least two times service pressure or 450 psig, whichever is the 

greater;

D = outside diameter in inches;

d = inside diameter in inches.



    (g) Heat treatment. The completed cylinders must be uniformly and 

properly heat-treated prior to tests.

    (h) Openings in cylinders and connections (valves, fuse plugs, etc.) 

for those openings. Threads, conforming to the following, are required 

on all openings:

    (1) Threads must be clean cut, even, without checks, and to gauge.

    (2) Taper threads when used, must be of a length not less than as 

specified for American Standard taper pipe threads.

    (3) Straight threads having at least 4 engaged threads are 

authorized. Straight threads must have a tight fit, and calculated shear 

strength at least 10 times the test pressure of the cylinder. Gaskets, 

adequate to prevent leakage, are required.

    (i) Hydrostatic test. Cylinders 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 either of 1 percent or 0.1 

cubic centimeter.

    (2) Pressure must be maintained for at least 30 seconds and 

sufficiently longer to insure 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) Each cylinder; to at least 2 times service pressure; or

    (ii) 1 cylinder out of each lot of 200 or less; to at least 3 times 

service pressure. Others must be examined under pressure of 2 times 

service pressure and show no defect.

    (j) Flattening test. A flattening test must be performed on one 

cylinder taken at random out of 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 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) Gauge length of 8 inches with a width of not over 1\1/2\ inches; 

or 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 thickness is authorized when a cylinder wall is not over \3/16\ 

inch thick.



[[Page 818]]



    (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. 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, the flattening test is 

not required.

    (2) An elongation of at least 20 percent for a 2-inch gauge length 

or 10 percent in other cases and yield strength not over 73 percent of 

tensile strength. Flattening is required, without cracking, to 6 times 

the wall thickness.

    (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 and limitations:

    (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 one 

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, a 

cylinder must be rejected if there is any leaking.

    (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. Reheat treatment of rejected cylinders is 

authorized. Subsequent thereto, cylinders must pass all prescribed tests 

to be acceptable. Repair by welding or spinning is not authorized. 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.

    (o) Marking. Markings may be stamped into the sidewalls of cylinders 

having a service pressure of 150 psig if all of the following conditions 

are met:



[[Page 819]]



    (1) Wall stress at test pressure may not exceed 24,000 psi.

    (2) Minimum wall thickness must be not less than 0.090 inch.

    (3) Depth of stamping must be no greater than 15 percent of the 

minimum wall thickness, but may not exceed 0.015 inch.

    (4) Maximum outside diameter of cylinder may not exceed 5 inches.

    (5) Carbon content of cylinder may not exceed 0.25 percent. If the 

carbon content exceeds 0.25 percent, the complete cylinder must be 

normalized after stamping.

    (6) Stamping must be adjacent to the top head.



[Amdt. 178-114, 61 FR 25942, May 23, 1996, as amended by 66 FR 45185, 

45386-45388, Aug. 28, 2001; 67 FR 51652, Aug. 8, 2002; 68 FR 75748, Dec. 

31, 2003]