tested as prescribed by paragraph (k), (2), (3), and (4) of this section.

(9) Any tank which has been out of transportation service for a period of one year or more shall not be returned to or placed in such service until it shall have successfully fulfilled the testing requirements prescribed by paragraph (k) (2), (3), and (4) of this section.

(10) The Commission may require the testing under prescribed conditions of any tank when probable cause appears for suspecting that such tank is in unsafe condition.

(1) The repair of tanks is authorized, provided such repairs are made under requirements prescribed in the "Code" for its original design and construction.

(1) In addition to any other provisions of the specification, no tank shall be repaired, or remodeled, as to cause leakage or cracks or likelihood of leakage or cracks, by areas of stress concentration due to shrinkage of cooling metal in welding operations, sharp fillets, reversal of stresses, or otherwise.

(2) No field welding shall be done except to non-pressure parts.

(m) On tanks used for compressed gases (except chlorine for which provisions are made at subparagraphs (9) to (11) of this paragraph), the bursting strength of any piping and fittings shall be not less than four times the design pressure of the tank, and not less than four times that pressure to which, in any instance, it may be subjected in service by the action of a pump or other device (not including safety relief valves) the action of which may be to subject certain portions of the tank piping to pressures greater than the design pressure of the tank.

(1) Welded pipe joints shall be used wherever possible. Joints in copper tubing shall be of the brazed type where permitted or of any equally strong metal union type. Melting point of brazing material must be not less than 1000° F. Such joints shall in any event be of such a character as not to decrease the strength of the tubing, as by the cutting of threads.

(2) Fittings shall be extra heavy. Non-malleable metals shall not be employed in the construction of valves or fittings.

(3) Suitable provision shall be made in every case to allow for expansion, contraction, jarring, and vibration of all pipe. Ship joints shall not be used for this purpose.

(4) Piping and fittings shall be grouped in the smallest practicable space and shall be protected from damage as required by the specification.

(5) All hose, wherever used, shall be designed for a bursting pressure not less than four times the design pressure of the tank with which it is used, and not less than four times that pressure to which, in any instance, it may be subjected in service by the action of a pump or other device, the action of which may be to subject the hose to pressures greater than the design pressure of the tank. Any coupling used on hose to make connections shall be designed for a pressure not less than 20 percent in excess of the design pressure of the hose and shall be so designed that there will be no leakage when connected.

(6) All piping, valves, and fittings on every tank motor vehicle shall be proved free from leaks at not less than the design pressure for the tank. This condition will be considered to have been met when such piping, valves, and fittings have been tested for leakage with gas or air after installation and proved tight at not less than the design pressure marked on the cargo tank with which they are used. In the event of replacement, all such piping, valves, or fittings so replaced shall be tested in accordance with the requirements of this section before the tank is returned to transportation service. The requirements of this section shall apply with equal force to all hose used on such tanks, except that such hose may be so tested either before or after installation on the tank.

(7) Liquid pumps or gas compressors, wherever used, must be of suitable design, adequately protected against breakage by collisions, and kept in good condition. They may be driven by motor vehicle power take-off or other mechanical, electrical, or hydraulic means. Unless they are of the certrifugal type, they shall be equipped with suitable pressure actuated by-pass valves permitting flow from discharge to suction or to the tank. Liquid pumps shall not be used on tanks for the shipment of sulphur dioxide.

(8) Each tank used for the shipment of carbon dioxide or nitrous oxide shall be provided with a suitable pressure gauge. A shut-off valve must be installed between the pressure gauge and the tank. This gauge need be used only during the filling operation.

(9) On cargo tank motor vehicles for the transportation of chlorine, no piping,

hose, or other means of loading or unloading shall be attached to the angle valves required by paragraph (o) (4) of this section except at the time of loading or unloading, nor shall any hose, piping, or tubing used for loading or unloading be mounted on or carried on the vehicle nor shall such devices be considered as part of the cargo tank motor vehicle. On cargo tank motor vehicles for the transportation of chlorine, except at the time of loading or unloading, pipe connections of the angle valves must be closed with screw plugs, chained or otherwise fastened to prevent misplacement.

(10) Angle valves on chlorine cargo tank motor vehicles shall be tested at not less than 225 p. s. i. g., using dry air or inert gas, before installation of such valves on the cargo tank, and such tests shall be made before each loading. The valves and gasketed joints shall be inspected for leaks, at a pressure of not less than 50 p. s. i. g., after loading and prior to shipment, and such inspections shall be made for each loading. Leaks which are detected shall be corrected before the cargo tank motor vehicle is shipped.

(11) Liquid chlorine pumps shall not be installed on cargo tank motor vehicles used for the shipment of chlorine.

(n) All materials of construction used in cargo tanks and their appurtenances shall not be subject to destructive attack by the contents of the tank.

(1) All parts of tanks and appurtenances for anhydrous ammonia shall be steel. No copper, silver, zinc, nor their alloys shall be permitted. Brazed joints shall not be permitted.

(0) Each outlet of cargo tanks used for the transportation of liquefied compressed gases, except carbon dioxide, shall be provided with an approved suitable automatic excess-flow valve or in lieu thereof may be fitted with an approved automatic quick-closing internal valve. These valves shall be located inside the tank or at a point outside the tank where the line enters or leaves the tank. The valve seat shall be located inside the tank or shall be located within a welded flange or its companion flange, or within a nozzle, or within a coupling. The installation shall be made in such a manner as reasonably to assure that any undue strain which causes failure requiring functioning of the valve shall cause failure in such a manner that it

will not impair the operation of the valve.

Exception. Safety device connections and liquid level gauging devices which are so constructed that the outward flow of tank contents shall not exceed that passed by a No. 54 drill size opening are not required to be equipped with excess-flow valves.

(1) Excess-flow valves shall close automatically at the rated flows of gas or liquid as specified by the valve manufacturer. The connections or lines on each side of the excess-flow valve, including valves, fittings, etc., shall have a greater capacity than the rated flow of the excess-flow valve.

(2) Excess-flow valves may be designed with a by-pass, not to exceed a No. 60 drill size opening, to allow equalization of pressures.

(3) Filling and discharge lines shall be provided with a shut-off valve located as close to the tank as is practicable, except where an automatic quick-closing internal valve or an automatic shut-off valve is used, in which case a manually operated shut-off valve shall be located anywhere in the line ahead of the hose connection.

NOTE 1: The use of so-called "Stop-Check" or excess flow valves to satisfy with one valve the requirements of this rule and of paragraph (o) of this section is forbidden.

(4) Angle valves and excess-flow valves on chlorine tank motor vehicles shall conform to the standards of The Chlorine Institute, Inc. Angle valve to conform with Dwg. 104-4, dated May 5, 1958; excess-flow valve to conform with Dwg. 101-3, dated January 23, 1959. An excess-flow valve shall be installed under each angle valve.

(p) Each tank for chlorine, carbon dioxide and nitrous oxide shall be lagged with a suitable insulation material of such thickness that the overall thermal conductance is not more than 0.08 B. t. u. per square foot per degree F. differential in temperature per hour. The conductance shall be determined at 60° F. In no event shall less than 4 inches of thickness of insulation be used. Insulation material used on tanks for nitrous oxide shall be noncombustible. Insulation material used on tanks for chlorine shall be corkboard.

(q) A refrigerating and/or heating coil or coils may be installed in tanks for carbon dioxide and nitrous oxide. Such coils must be tested externally to at least the same pressure as the test

pressure of the tank. The coils must also be tested internally to at least twice the working pressure of the heating or refrigerating system to be used but in no case less than the test pressure of the tank. Such coils shall be securely anchored. The refrigerant or heating medium to be circulated through the coil or coils must be such as to cause no adverse chemical reaction with the tank or tank contents in case of leakage. If desired, the unit furnishing refrigeration may be mounted on the motor vehicle.

[15 F.R. 8280, Dec. 2, 1950, as amended by Order 6, 17 F. R. 7280, Aug. 9, 1952; Order 13, 19 F. R. 1276, Mar. 6, 1954; Order 14, 19 F. R. 3258, June 3, 1954; Order 20, 20 F. R. 8098, Oct. 28, 1955; Order 21, 21 F. R. 670, Jan. 31, 1956; Order 25, 21 F.R. 3008, May 5, 1956; Order 34, 23 F.R. 2323, Apr. 10, 1958; Order 43, 25 F.R. 6624, July 14, 1960; Order 47, 26 F.R. 2502, Mar. 24, 1961]

§ 73.34 Qualification, maintenance, and use of cylinders.

(a) Cylinders in domestic use previous to the date upon which specifications therefor were first made effective may be used if the cylinders have been properly tested and otherwise comply with the requirements of paragraphs (c) to (k) of this section.

(b) Cylinders of foreign manufacture, received from foreign countries for charging with compressed gas, may be charged and shipped for export only:

(1) Provided, They are retested in accordance with paragraphs (j) and (k) of this section. This retest may be omitted only if the cylinder can be definitely identified as having been retested under these provisions within the prescribed retest period.

(2) Provided further, That the maximum filling density and service pressure for each cylinder shall be in accordance with all packaging requirements of this part for the compressed gas involved and the test pressure established by the retest of the cylinder.

(3) Records giving data showing the results of the tests made on all cylinders must be preserved for inspection for at least 5 years.

(4) Bill of lading or other shipping paper shall, when possible, identify the cylinder and shall carry the following certification: "These cylinders have been retested and refilled in accordance with the I. C. C. requirements for export."

87180-63

(c) Cylinders previously used in any service in accordance with this part may be transferred to a service requiring less strength and for which they are suitable, upon application to the Bureau of Explosives and receipt of advice to change the marking on the cylinders.

(d) Cylinders made prior to October 1, 1930, for which steel manufacturer's certificates are not available but for which physical and chemical tests on samples taken from one out of each 200 cylinders are in proper form, each cylinder having been satisfactorily tested in water-jacket apparatus to 2 times the service pressure (see § 73.301 (g)), properly reported as otherwise in full compliance with spec. 71 effective at date of manufacture and lawfully marked ICC-7-150,1 are authorized for use under the provisions of this part.

(e) When containers with a marked pressure limit are prescribed, other containers made under the same specification, but with a higher marked pressure limit are authorized. For example, containers marked ICC-4B500 ($78.50 of this chapter) may be used where ICC4B300 (§ 78.50 of this chapter) is specified.

(f) Safety relief devices. Each cylinder charged with compressed gas, unless excepted in this paragraph, must be equipped with one or more safety relief devices approved, as to type, location, and quantity, by the Bureau of Explosives and must be capable of preventing explosion of the normally charged cylinder when it is placed in a fire. (Cylinders shall not be shipped with leaking safety relief devices. Safety relief devices must be tested for leaks before the charged cylinder is shipped from the cylinder filling plant; it is expressly forbidden to repair leaking fuse plug devices, where leak is through the fusible metal or between the fusible metal and the opening in the plug body, except by removal of the device and replacement of the fusible metal.) Exceptions are as follows:

(1) Except as provided in Notes 1, 2 and 3, safety relief devices are not required on cylinders 12" or less in length, exclusive of neck, and 41⁄2" or less in outside diameter.

NOTE 1: Safety relief devices are required on specs. 9, 40, and 41 (§§ 78.63, 78.66, and 78.67 of this chapter) cylinders.

1 Use of existing cylinders authorized, but new construction not authorized.

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NOTE 2: Safety relief devices are required on cylinders charged with a liquefied gas for which this part requires a service pressure of 1,800 pounds per square inch or higher.

NOTE 3: Safety relief devices are required on cylinders charged with nonliquefied gases to a pressure of 1,800 pounds per square inch or higher at 70° F.

(2) Safety relief devices are not required on cylinders charged with nonliquefied gas, except acetylene in solution, under pressure of 300 pounds per square inch or less at 70° F.

(3) Safety relief devices are prohibited on cylinders charged with poisonous gas or liquid as defined in § 73.326 (a).

(4) Safety relief devices are prohibited on cylinders charged with fluorine.

(5) Safety relief devices are not required on cylinders charged with methyl mercaptan; mono, di, or trimethylamine, anhydrous; with not over 10 pounds of nitrosyl chloride; or with less than 165 pounds of anhydrous ammonia.

(6) Safety relief devices are not required on drums containing liquefied petroleum gas as provided for in § 73.312 (a).

(g) Marking on cylinders must not be changed except as follows:

(1) By application of additional marks not affecting the test pressure or filling pressure; these must not obliterate previously applied marks.

(2) By application of test pressure or filling pressure marks, or alteration of such marks, to indicate a reduced test and filling pressure; authorized only for cylinders that have not failed in the quinquennial test.

(3) By change of serial numbers or ownership marks or both; before remarking, report must be filed with the Bureau of Explosives, in sufficient detail and arranged consecutively according to registered ownership symbol and serial or lot numbers, so that specification marking, previous serial number, registered ownership symbol, and original test date can be determined for each cylinder.

(4) By change in marks which indicate compliance with specifications and charging and testing pressures (such as ICC-3, ICC-3A-1800) to indicate a higher test and filling pressure; authorized only upon written instructions from the Bureau of Explosives.

(5) When restrictions imposed by § 73.304 will result in condemnation of cylinders previously in authorized use, the Bureau of Explosives shall, upon application, approve change in marks for pressures not greater than as follows: ICC-7-70 for change to ICC-7-116; ICC26-150 for change to ICC-26-300; ICC26-300 for change to ICC-26-450; ICC26-600 for change to ICC-26-900; ICC26-1000 for change to ICC-26-1200.

(6) When the space originally provided for dates of subsequent retests becomes filled, the stamping of additional test dates into the external surface of footrings of cylinders is authorized.

(7) Marking on cylinders must be kept plain. All prescribed markings on cylinders must be maintained in a readable condition, or a copy of said markings reproduced by stamping on brass plates permanently secured to the cylinders is permitted.

(h) Cylinders subjected to action of fire. A cylinder which has been subjected to the action of fire must not again be placed in service until it has been properly reconditioned by being reheattreated and retested as specified in paragraph (i) of this section. Exceptions are as follows:

(1) A cylinder made of plain carbon steel with not over 0.25 percent carbon nor over 0.90 percent manganese need not be reheat-treated but must pass the periodic retest requirements as specified in paragraphs (j) and (k) of this section.

(2) ICC-8 (§ 78.59 of this chapter) cylinders made of plain carbon steel with not over 0.25 percent carbon nor over 0.90 percent manganese must be reinspected to determine the condition of the cylinder and the porous filling. the cylinder is undamaged and the filler is unchanged and intact, the cylinder may be returned to service without reheat treatment or test.

If

(3) The inner cylinders made under specification ICC-4L (§ 78.57 of this chapter) may be used after again passing the original hydrostatic test.

(4) ICC-4E (§ 78.68 of this chapter) aluminum cylinders must be removed from service.

(i) Reheat treatment and retest of cylinders. The reheat treatment of cylinders must be followed by hydrostatic retest and these operations must be carried out, supervised, and reported, as pre

scribed for the original heat treatment and hydrostatic test by the specification covering the manufacture of the type of cylinder in question. The retest pressure shall be as prescribed for the quinquennial retesting of cylinder: Provided, That increased retest pressure is authorized under testing procedure approved in writing by the Bureau of Explosives. In the case of cylinders of outside diameter exceeding 4 inches, a permanent expansion of not less than 3 percent or more than 10 percent of the total expansion must be shown in the retest: Provided, That if the cylinders can be segregated into lots having practically the same chemical composition, the allowable permanent expansion in the retest may be from zero to 10 percent of the total expansion, if one cylinder out of each such lot of 100 cylinders or less is subjected to and passes the requirements of the flattening and physical tests as specified by the specification for the manufacture of the type of cylinder in question.

(j) Retest and reinspection of cylinders. Each cylinder, except as specifically provided in paragraph (k) of this section, must be subjected, at least once in five years, to a test by interior hydrostatic pressure in a water jacket, or other apparatus of suitable form, for the determination of the expansion of the cylinder. The test apparatus must be approved as to type and operation by the Bureau of Explosives. This periodic retest must include a visual internal and external examination, except that the internal inspection may be omitted for cylinders of the type and in the service described under paragraph (k) (11) of this section: Provided, That without regard to date of previous test, cylinders of ICC-4 type that show bad dents or other evidence of rough usage, or that are corroded locally to such extent as to indicate possible weakness, or that have lost as much as 5 percent of their official tare weight, must be retested before being again charged and shipped. After any retest, the actual tare weight for those cylinders passing the test may be recorded as their new official tare weight.

(1) In hydrostatic retesting of a cylinder the pressure must be maintained for at least 30 seconds and as much

longer as may be necessary to secure complete expansion of the cylinder. The gauge indicating the total expansion of the cylinder must be such that the total expansion can be read with an accuracy of 1 percent, except that a reading to 0.1 cubic centimeter shall be acceptable. The gauge indicating the pressure must be capable of being read to within 1 percent of the test pressure. Any internal pressure applied previous to the test pressure shall 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 pounds per square inch, whichever is the lower value.

(2) A cylinder must be condemned when it leaks, or when internal or external corrosion, denting, bulging, or evidence of rough usage exists to the extent that the cylinder is likely to be weakened appreciably or when the permanent expansion exceeds 10 percent of the total expansion, except that for ICC-4E (§ 78.68 of this chapter) aluminum cylinders, when the permanent expansion exceeds 12 percent of the total expansion. Except for ICC-4E aluminum cylinders, a cylinder condemned for excessive permanent expansion may be reheattreated. (See paragraph (i) of this section.) ICC-4 series cylinders, condemned for other than excessive permanent expansion, may be repaired or rebuilt as prescribed in paragraphs (m), (n), (o), and (p) of this section.

(3) Records giving data showing the results of the tests made on all cylinders must be kept, and each cylinder passing the test must be marked with the date (month and year) plainly and permanently stamped into the metal of the cylinder. For example, 4-50 for April 1950. Dates of previous tests must not be obliterated. Records showing the results of reinspection and retest must be kept by the owner or his authorized agent until either expiration of the retest period, or until the cylinder is again reinspected or retested, whichever occurs first.

(k) The tests prescribed by paragraph (j) of this section must be in accordance with the following table and exceptions thereto.