secure closure, and means shall also be provided for the closing of pipe connections or valves.

[Order 12, 18 F. R. 6784, Oct. 27, 1953]

§ 78.331-13 Heads, bulkheads and baffles. (a) Flat heads or flat bulkheads without reinforcement are not permitted. The use of baffles is not a specification requirement.

[Order 20, 20 F. R. 8115, Oct. 28, 1955]

(a)

§ 78.331-14 Outage indicators. Every cargo tank, and every compartment of cargo tank must be equipped with a means of indicating outage. [Order 12, 18 F. R. 6785, Oct. 27, 1953]

§ 78.331-15 Closures for manholes. (a) The manhole cover shall be designed to provide a secure closure of the manhole. All joints between manhole covers and their seats shall be made tight against leakage of vapor and liquid by use of gaskets of suitable material not subject to attack by the corrosive liquid to be transported in the tank.

[Order 12, 18 F. R. 6785, Oct. 27, 1953]

(a)

§ 78.331-16 Overturn protection. All closures for filling openings and outlets shall be protected from damage in the event of overturn of the motor vehicle by being enclosed within the body of the tank or dome attached thereto or the use of substantial metal guards securely attached to the cargo tank or frame of the motor vehicle. [Order 12, 18 F. R. 6785, Oct. 27, 1953]

§ 78.331-17 Heater coils. (a) Heater coils, when installed, shall be so constructed that the breaking off of their external connections will not cause leakage of contents of tanks.

[Order 12, 18 F. R. 6785, Oct. 27, 1953]

§ 78.336 Specification MC 330; steel cargo tanks.

§ 78.336-1 Requirements for design and construction. (a) Tanks shall be of seamless or welded steel construction or combination of both and shall be designed and constructed in accordance with and fulfill the requirements of (1) Section VIII of the Code for Unfired Pressure Vessels of the American Society of Mechanical Engineers, 1949 Edition, except that construction under Par. U-70 is not authorized; or (2) Section VIII of the Code for Unfired Pressure Vessels of the American Society of Mechanical Engineers, 1950 Edition; or (3) Section VIII of the Code for Unfired Pressure Vessels

of the American Society of Mechanical Engineers, 1952 Edition; or (4) the A. P. I.-A. S. M. E. Code for Unfired Pressure Vessels for Petroleum Liquids and Gases, 1943 Edition; or (5) the A. P. I.-A. S. M. E. Code for Unfired Pressure Vessels for Petroleum Liquids and Gases, 1951 Edition; no revisions (any or all of which hereinafter referred to as "the Code").

Exception: Chlorine tanks shall be fully radiographed and stress relieved in accordance with the provisions of the Code under which they are constructed.

(b) Except as noted below, all openings in the tank shall be grouped in one location, either at the top of the tank or at one end of the tank.

Exceptions: (1) Chlorine tanks shall be equipped with a nozzle located in the top of the tank. The nozzle shall be fitted with a dome cover plate which shall conform with the standard of The Chlorine Institute, Inc. Dwg. 7-B-345, dated March 3, 1953. There shall be no other opening in the tank. (2) The openings for liquid level gauging devices, or for safety devices may be installed separately at the other location or in the side of the shell. (3) One plugged opening of 2-inch National Pipe Thread or less provided for maintenance purposes may be located elsewhere. (4) Loading and unloading connections may be located in the bottom of the tank.

(c) On and after August 31, 1953, every uninsulated cargo tank permanently attached to a tank motor vehicle shall, unless it be covered with a jacket made of aluminum, stainless steel, or other bright nontarnishing metal, be painted all over a white, aluminum, or similar reflecting color.

[Order 13, 19 F. R. 1287, Mar. 6, 1954; Order 20, 20 F. R. 8115, Oct. 28, 1955; Order 28, 21 F. R. 9364, Nov. 30, 1956]

§ 78.336-2 Material. (a) All material used for the construction of the tank and appurtenances shall be suitable for use with the commodity to be transported therein.

(b) Material of thickness less than 316 inch shall not be used for the shell, heads and protective housings specified in § 78.336-5, except for chlorine tanks the wall thickness shall be not less than % inch, including corrosion allowance.

(c) All plates for tank, manway nozzle and anchorage of tanks used in the transportation of chlorine must be made of steel complying with requirements of A. S. T. M. Specification A-300-52T

titled "Steel Plates for Pressure Vessels for Service at Low Temperatures", Class 1, Grade "A", flange or fire box quality. Impact test specimens made by the plate manufacturer shall be of the Charpy Keyhole notch type and must meet impact requirements (in both longitudinal and transverse directions of rolling) of this specification at a temperature of minus 50° F.

[15 F. R. 8372, Dec. 2, 1950, as amended by Order 20, 20 F. R. 8116, Oct. 28, 1955; Order 21, 21 F. R. 676, Jan. 31, 1956]

§ 78.336-3 Design working pressure. (a) The design working pressure of a tank authorized under this specification shall be not less than the vapor pressure of the commodity contained therein at 115° F., or as prescribed for a particular commodity by Part 73 of this chapter, except that in no case shall the design working pressure of any container be less than 100 psig nor more than 500 psig. When corrosion factor is prescribed by these regulations, the wall thickness of the tank calculated in accordance with the "Code" (see § 78.336-1 (a)) shall be increased by 20 percent or 0.10 inch, whichever is less.

NOTE 1. The term "design working pressure" as used in this specification is identical to the term "Maximum allowable working pressure" as used in the "Code" (see § 78.336-1 (a)).

§ 78.336-4

Provisions for anchoring tanks to motor vehicles. (a) Except as provided in paragraph (c) of this section, adequate "hold-down" devices shall be provided which will anchor each tank used as part of any motor vehicle in a suitable and safe manner that will not introduce undue concentration of stresses. These devices shall incorporate turnbuckles or similar positive devices for drawing the tank down tight on the frame of the motor vehicle. Suitable stops or anchors shall be attached to the motor vehicle and the tank to prevent relative movement between them due to stopping, starting, or changes in direction.

(b) The means of attachment of any tank to the cradle, frame, or chassis of a motor vehicle shall be designed with a factor of safety of not less than four, and be built to withstand loadings in any direction equal to two times the weight of the tank and attachments when filled with water.

(c) Whenever any tank motor vehicle is so designed and constructed that the

cargo tank constitutes in whole or in part the stress member used in lieu of a frame, then such cargo tanks shall be designed so as successfully and adequately to withstand the stresses thereby imposed in addition to those covered by "the Code" (see § 78.336-1 (a)).

(d) Stops and anchors shall be installed so as to be readily accessible for inspection and maintenance, except that for lagged tanks lagging is permitted to cover such areas.

§ 78.336-5 Protection of valves and accessories. (a) All valves, fittings, accessories, safety devices, gauging devices, and the like shall be adequately protected against mechanical damage by a housing closed with a cover plate.

Exceptions: (1) Liquid and vapor valves, fittings, and accessories installed in the bottom of the tank shall be adequately protected against mechanical damage, but the housing and cover plate may be omitted. (2) In lieu of a housing closed with a cover plate, tanks used for the transportation of carbon dioxide may have all valves, piping, fittings, accessories, safety devices, and the like installed within the motor vehicle framework, or a suitable collision-resisting subframe, guard or housing. (3) On chlorine tanks the protective housing and cover plate shall conform to the standard of The Chlorine Institute, Inc. Dwg. CS-843, dated July 27, 1954 and shall be of a design to permit the use of standard emergency kits for controlling leaks in fittings on the dome cover plate.

(b) Protective housing shall comply with the requirements under which the tanks are fabricated with respect to design and construction, and shall be designed with a minimum factor of safety of four to withstand loadings in any direction equal to two times the weight of the tank and attachments when filled with water.

(c) Requirements concerning types of valves, retesting, and qualification of cargo tanks contained in §§ 73.33 and 73.315 of this chapter must be observed. [15 F. R. 8372, Dec. 2, 1950, as amended by Order 20, 20 F. R. 8116, Oct. 28, 1955]

§ 78.336-6 (a) Name plate. In addition to the markings required by the "Code" (See § 78.336-1 (a)) under which tanks were constructed, they shall have permanently affixed, on one of the heads of the tank, a metal plate. This plate shall be permanently affixed by means of soldering, brazing, or welding around its perimeter. Neither the plate itself nor the means of attachment to the tank