49 CFR Ch. I (10–1–06 Edition) §178.37
not less than 3⁄4inch in diameter, in-cluding the closure, for at least 1 minute, during which time the other side of the bottom expod to pressure must be covered with water and cloly examined for indications of leakage. Except as provided in paragraph (n) of this ction, a cylinder that is 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驱动顶尖
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, the manu-facturer should design the test appa-ratus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to u the smallest possible volume of air or gas.
(n) Rejected cylinders. Reheat treat-ment is authorized for rejected cyl-inders. Subquent thereto, cylinders must pass all prescribed tests to be ac-ceptable. Repair by welding or spinning is not authoriz
ed. Spun cylinders re-jected under the provisions of para-graph (m) of this ction may be re-moved from the spun cylinder category by drilling to remove defective mate-rial, tapping and plugging.
[Amdt. 178–114, 61 FR 25942, May 23, 1996, as amended at 62 FR 51561, Oct. 1, 1997; 66 FR 45185, 45386–45387, Aug. 28, 2001; 67 FR 51652, Aug. 8, 2002; 68 FR 75748, Dec. 31, 2003]
§178.37Specification 3AA and 3AAX amless steel cylinders.
(a) Type, size and rvice pressure. In addition to the requirements of §178.35, cylinders must conform to the fol-lowing:
(1) A DOT-3AA cylinder is a amless steel cylinder with a water capacity (nominal) of not over 1,000 pounds and
a rvice pressure of at least 150 psig.
(2) A DOT-3AAX cylinder is a am-less steel cylinder with a water capac-ity of not less than 1,000 pounds and a rvice pressure of at least 500 psig, conforming to the following require-ments:
(i) Assuming the cylinder is to be supported horizontally at its two ends only and to be uniformly load
ed over its entire length consisting of the weight per unit of length of the straight cylindrical portion filled with water and compresd to the specified test pressure; the sum of two times the maximum tensile stress in the bottom fibers due to bending, plus that in the same fibers (longitudinal stress), due to hydrostatic test pressure may not ex-ceed 80 percent of the minimum yield strength of the steel at such maximum stress. Wall thickness must be in-cread when necessary to meet the re-quirement.
(ii) To calculate the maximum ten-sile stress due to bending, the following formula must be ud:
S = Mc/I
(iii) To calculate the maximum lon-gitudinal tensile stress due to hydro-static test pressure, the following for-mula must be ud:
S = A1P/A2
Where:
S = tensile stress-p.s.i.;
M = bending moment-inch pounds (wl2)/8;
w = weight per inch of cylinder filled with water;
l = length of cylinder-inches;
c = radius (D)/(2) of cylinder-inches;
I = moment of inertia-0.04909 (D4¥d4) inches fourth;
D = outside diameter-inches;
d = insid
e diameter-inches;
A1= internal area in cross ction of cyl-inder-square inches;
A2= area of metal in cross ction of cyl-inder-square inches;
P = hydrostatic test pressure-psig.
(b) Authorized steel. Open-hearth, basic oxygen, or electric steel of uni-form quality must be ud. A
heat of steel made under the specifications in table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is accept-able, if satisfactory in all other re-spects, provided the tolerances shown in table 2 of this paragraph (b) are not exceeded. When a carbon-boron steel is ud, a hardenability test must be per-formed on the first and last ingot of each heat of steel. The results of this test must be recorded on the Record of Chemical Analysis of Material for Cyl-inders required by §178.35. This hard-ness test must be made 5⁄16-inch from the quenched end of the Jominy quench
Pipeline and Hazardous Materials Safety Admin., DOT §178.37
bar and the hardness must be at least Rc 33 and no more than Rc 53. The fol-lowing chemical analys are author-ized:
T ABLE1—A UTHORIZED M ATERIALS
幼儿园纲要Designation
4130X (per-
cent) (e Note
1)
NE–8630 (per-
cent) (e Note
1)
9115 (percent)
(e Note 1)
9125 (percent)
(e Note 1)
Carbon-boron
(percent)
Inter- mediate
造句大全>足球点球规则mangane
(percent)
<0.25/.0.28/.0.10/.0.20/.0.27–0.40 max. 0.40/.0.70/.0.50/.0.50/.0.80– 1.35/1.65. 0..0..0..0..0.0.04 max. 0..0..0..0..0.0.05 max. 0.15/.0.20/.0.60/.0.60/.0.0.10/0.30. 0.80/.0.40/.0.50/.0.50/0.65. 0.15/.0.15/0..0.05/.0.05/0.0.40/0.70. .0.0005/0.003.
N OTE1: This designation may not be restrictive and the commercial steel is limited in analysis as shown in this table.
T ABLE2—C HECK A NALYSIS T OLERANCES
Element Limit or maximum specified
(percent) Tolerance (percent) over the maximum limit or under the minimum limit Under min-
imum limit
Over max-
imum limit
Over 0.15 to 0.03 .To 0.03 .03
Over 0.60 to 1.0.04 0.04
Over 1.15 to 2.0.05 0.All ranges.. (01)
Over 0.30 to 1.05 .To 1.03 .To 0.03 .03
0.90 to 2.05 .To 0.01 .01
Over 0.20 to 02 ..01 .05 1Rephosphorized steels not subject to check analysis for phosphorus.
(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 process adequate to ensure that each cylinder produced conforms to the re-quirements of this subpart. No fissure or other defects 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 other-wi treated to eliminate the defects. The thickness of the bottoms of cyl-inders 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 thickness must be measured within an area bounded by a line reprenting the points of contact between the cyl-inder and floor when the cylinder is in a vertical position.
(e) Welding or brazing. Welding or brazing for any purpo whatsoever is prohibited except as follows:数控加工编程
(1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts, and only to the tops and bottoms of cylinders having a rvice pressure of 500 psig o
奶瓶r less. Cylinders, neckrings, and footrings must be made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the
49 CFR Ch. I (10–1–06 Edition) §178.37
ca of 4130X steel which may be ud with proper welding procedure.
(2) As permitted in paragraph (d) of this ction.
(f) Wall thickness. The thickness of each cylinder must conform to the fol-lowing:
(1) For cylinders with a rvice pres-sure of less than 900 psig, the wall stress may not exceed 24,000 psi. A min-imum wall thickness of 0.100 inch is re-quired for any cylinder with an outside diameter of over 5 inches.
(2) For cylinders with rvice pres-sure of 900 psig or more the minimum wall must be such that the wall stress at the minimum specified test pressure may not exceed 67 percent of the min-imum tensile strength of the steel as determined from the physical tests re-quired in paragraphs (k) and (l) of this ction and must be not over 70,000 psi.
(3) 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;
巡视整改工作方案
D = outside diameter in inches;
d = insid
e diameter in inches.
(g) Heat treatment. The completed cyl-inders must be uniformly and properly heat treated prior to tests. Heat treat-ment of cylinders of the authorized analys must be as follows:
(1) All cylinders must be quenched by oil, or other suitable medium except as provided in paragraph (g)(5) of this c-tion.
(2) The steel temperature on quench-ing must be that recommended for the steel analysis, but may
not exceed 1750 °F.
(3) All steels must be tempered at a temperature most suitable for that steel.
(4) The minimum tempering tempera-ture may not be less than 1000 °F ex-cept as noted in paragraph (g)(6) of this ction.
(5) Steel 4130X may be normalized at
a temperature of 1650 °F instead of being quenched and cylinders so nor-malized need not be tempered.
(6) Intermediate mangane steels may be tempered at temperatures not less than 1150 °F., and after heat treat-
ing each cylinder must be submitted to
a magnetic test to detect the prence
of quenching cracks. Cracked cylinders must be rejected and destroyed.
(7) Except as otherwi provided in paragraph (g)(6) of this ction, all cyl-inders, if water quenched or quenched with a liquid producing a cooling rate
in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle, dye penetrant or ul-trasonic method to detect the prence
of quenching cracks. Any cylinder de-signed to the requirements for speci-fication 3AA and found to have a quenching crack must be rejected and may not be requalified. Cylinders de-signed to the requirements for speci-fication 3AAX and found to have cracks must have cracks removed to sound metal by mechanical means. Such specification 3AAX cylinders will be acceptable if the repaired area is subquently examined to assure no de-fect, and it is determined that design thickness requirements are met.
(h) Openings in cylinders and connec-tions (valves, fu plugs, etc.) for tho openings. Threads are required on open-ings.
(1) Threads must be clean cut, even, without checks, and to gauge.
(2) Taper threads, when ud, must be
of a length not less than as specified for American Standard taper pipe threads.
(3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required.
(i) Hydrostatic test. Each cylinder must successfully withstand a hydro-static test as follows:
(1) The test must be by water-jacket,
or other suitable method, operated so as to obtain accurate data. The pres-sure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total ex-pansion to an accuracy of either 1 per-cent or 0.1 cubic centimeter.
(2) Pressure must be maintained for
at least 30 conds and sufficiently longer to ensure complete expansion. Any internal pressure applied after
Pipeline and Hazardous Materials Safety Admin., DOT §178.37
heat-treatment and previous to the of-ficial 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 incread by 10 percent or 100 psig, whichever is the lower.
(3) Permanent volumetric expansion may not exceed 10 percent of total vol-umetric expansion at test pressure.
(4) Each cylinder must be tested to at least 5⁄3times the rvice pressure.
(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° included angle, rounded to 1⁄2-inch ra-dius. The longitudinal axis of the cyl-inder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are author-ized 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 speci-mens cut from 1 cylinder taken at ran-dom out of each lot of 200 or less. For lots of 30 or less, physical tests are au-thorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to the same heat treat-ment as the finished cylinder.
(2) Specimens must conform to the following:
(i) Gauge length of 8 inches with a width of not over 11⁄2inches, a gauge length of 2 inches with a width of not over 11⁄2inches, or a gauge length of at least 24 times the thickness with width not over 6 times thickness when the thickness of the cylinder wall is not over 3⁄16inch.
(ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced ction.
(iii) When size of cylinder does not permit curing straight specimens, the specimens may be taken in any lo-cation or direction and may be straightened or flattened cold, by pres-sure only, not by blows. When speci-mens are so taken and prepared, the in-spector’s report must show in connec-tion with record of physical tests de-tailed information in regard to such specimens.
(iv) Heating of a specimen for any purpo 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 deter-mined by either the ‘‘offt’’ method or the ‘‘extension under load’’ method as prescribed in ASTM E 8 (IBR, e §171.7 of this subchapter).
(ii) In using the ‘‘extension under load’’ method, the total strain (or ‘‘ex-tension under load’’) corresponding to the stress at which the 0.2 percent per-manent strain occurs may be deter-mined with sufficient accuracy by cal-culating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension cal-culations must be bad 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 per-cent offt.
(iii) For the purpo of strain meas-urement, the initial strain must be t while the specimen is under a stress of 12,000 psi, the strain indicator reading being t at the calculated cor-responding strain.
(iv) Cross-head speed of the testing machine may not exceed 1⁄8inch per minute during yield strength deter-mination.
(l) Acceptable results for physical and flattening tests. An acceptable result for physical and flattening tests is elon-gation at least 20 percent for 2 inches of gauge length or at least 10 percent in other cas. Flattening is required, without cracking, to 6 times the wall thickness of the cylinder.
(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. Pressure, approxi-mately the same as but no less than the rvice pressure, must be applied to
49 CFR Ch. I (10–1–06 Edition)
§178.38
one side of the finished bottom over an area of at least 1⁄16of the total area of the bottom but not less than 3⁄4inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom expod to pressure must be covered with water and cloly examined for indications of leakage. Except as provided in para-graph (n) of this ction, a cylinder must be rejected if there is any leak-ing.
(1) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spi
nning process. (2) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug.
(3) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manu-facturer should design the test appa-ratus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to u the smallest possible volume of air or gas.
(n) Rejected cylinders. Reheat treat-ment is authorized for rejected cyl-inders. Subquent thereto, cylinders must pass all prescribed tests to be ac-ceptable. Repair by welding or spinning is not authorized. Spun cylinders re-jected under the provision of paragraph (m) of this ction may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging.
[Amdt. 178–114, 61 FR 25942, May 23, 1996, as
amended at 65 FR 58631, Sept. 29, 2000; 66 FR 45386–45387, Aug. 28, 2001; 67 FR 51652, Aug. 8, 2002; 68 FR 75748, Dec. 31, 2003]
§178.38Specification 3B amless
steel cylinders.
(a) Type, size, and rvice pressure. A DOT 3B cylinder is amless steel cyl-inder with a water capacity (nominal) of not over 1,000 pounds and a rvice
pressure of at least 150 to not over 500
psig.
(b) Steel. Open-hearth or electric steel of uniform quality must be ud. Con-tent percent may not exceed the fol-lowing: carbon, 0.55; phosphorus, 0.045;寻找有缘人
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 process adequate to ensure that each cylinder produced conforms to the re-quirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smoo
th and uniform surface finish is required. If not originally free from such defects, the surface may be machined or other-wi treated to eliminate the defects. The thickness of the bottoms of cyl-inders 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 thickness to be measured within an area bounded by a line reprenting 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 purpo whatsoever is prohibited except as follows:
(1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts, and only to the tops and bottoms of cylinders having a rvice 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 ca of 4130X steel which may be ud with proper welding procedure.
(2) As permitted in paragraph (d) of this ction. (f) Wall thickness. The wall stress may not exceed 24,000 psi. The minimum wall thickness is 0.090 inch for any cyl-inder 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 rvice pressure or 450
psig, whichever is the greater;
D = outside diameter in inches;
d = insid
e diameter in inches.
(g) Heat treatment. The completed cyl-inders must be uniformly and properly heat-treated prior to tests.
