or from a competent testing agency, certifying that each such cargo tank is designed, constructed and tested in accordance and complies with the requirements contained in the applicable specification shall be procured, and such certificate shall be retained in the files of the carrier during the time that such cargo tank is employed by him plus one year. In lieu of this certificate, if the motor carrier himself elects to ascertain that any such tank fulfills the requirements of the specification by his own test, he shall similarly retain the test data.

[Order 73, 32 F.R. 3462, Mar. 2, 1967] § 178.341

tanks.

Specification MC 306; cargo

[Order 73, 32 F.R. 3462, Mar. 2, 1967]
§ 178.341-1 General requirements.

(a) Specification MC 306 cargo tanks must comply with the general design and construction requirements in § 178.340 in addition to the specific requirements contained in this section.

(b) Design pressure: The design pressure of each cargo tank shall be not less than that pressure exerted by the static head of the fully loaded tank in the upright position.

[Order 73, 32 F.R. 3462,, Mar. 2, 1967] § 178.341-2 Thickness of shells, heads, bulkheads, and baffles.

(a) Material thickness. The minimum thicknesses of tank material authorized in § 178.340-3 shall be predicated on not exceeding the maximum allowable stress level (§ 178.340-4(a)) but in no case less than those indicated in Tables I and II below:

MSH

SS

Less than 70

inches

SS

(1) Product density. The material thicknesses contained in Tables I and II are minimums based on a maximum 7.2 pounds per gallon product weight. If the tank is designed to haul products weighing more than 7.2 pounds per gallon, the gallon per inch value used to determine the minimum thickness of heads, bulkheads, baffles or shell sheets shall be the actual section capacity required in gallons per inch multiplied by the actual product density in pounds per gallon divided by 7.2.

[Order 73, 32 F.R. 3462, Mar. 2, 1967]

§ 178.341-3 Closures for fill openings and manholes.

(a) Each compartment in excess of 2,500 gallons capacity shall be accessible through a manhole of at least 11 x 15 inches. Manhole and/or fill opening covers shall be designed to provide secure closure of the openings. They shall have structural capability of withstanding internal fluid pressures of 9 p.s.i.g. without permanent deformation. Safety devices

(a) Each cargo tank compartment shall be provided with safety relief devices in accordance with the requirements contained in this paragraph. All of such devices shall communicate with the vapor space. Shutoff valves shall not be installed between the tank opening and any safety device. Safety relief devices shall be so mounted, shielded, or drained as to eliminate the accumulation of water, the freezing of which could impair the operation or discharge capability of the device.

(b) Normal venting: Each cargo tank compartment shall be provided with pressure and vacuum vents having a minimum through area of 0.44 square inch. All pressure vents shall be set to open at no more than 1 p.s.i.g. and all vacuum vents at no more than 6 ounces

Pressure and vacuum vents shall be designed to prevent loss of liquid through the vent in case of vehicle overturn.

(c) Loading and unloading venting protection: If the tank is designed to be loaded or unloaded with the dome cover closed, the vent or vents as described in paragraph (b) of this section or additional vents shall limit the vacuum to 1 p.s.i. and the tank pressure to 3 p.s.i.g. based on maximum product transfer rate to be included on the metal certification plate 178.340-10(b). Unless effective protection against overfilling is made, the pressure vent shall also have sufficient liquid capacity to prevent the pressure from exceeding 3 p.s.i.g. in case of accidental overfilling. This pressure vent may be pressure operated or interlocked with the tank loading device, and shall be designed to prevent loss of liquid through the vent under any condition of vehicle rollover attitude.

(d) Emergency venting for fire exposure:

(1) Total capacity. The total emergency venting capacity (cu. ft./hr.) of each cargo tank compartment shall be not less than that determined from Table

III.

(2) Pressure-actuated venting. Each cargo tank be compartment shall equipped with pressure-actuated vent or vents set to open at not less than 3 p.s.i.g. and close when pressure drops to 3 p.s.i.g. or below.

The minimum venting capacity for pressure-actuated vents shall be 6,000 cubic feet of free air per hour (14.7 p.s.i.a. and 60° F.) from a tank pressure of 5 p.s.i.g. Pressure-actuated devices shall be designed so as to prevent leakage of liquid past the device in case of surge or vehicle upset, except that they shall function in case of pressure rise under any condition of vehicle rollover attitude.

(3) Fusible venting. If the pressureactuated venting required by subparagraph (2) of this paragraph does not provide the total venting capacity required by subparagraph (1) of this paragraph additional capacity shall be provided by adding fusible venting devices each having a minimum area of 1.25 square inches, such fusible elements shall be so located as to not be in contact with the tank lading under normal operating conditions. The fusible vent or vents shall be actuated by elements which operate at a temperature not exceeding

(e) Flow testing and marking of vents: Each type and size of venting devices shall be flow tested in the ranges specified in the applicable preceding paragraphs. The actual rated flow capacity of the vent in cubic feet of free air per hour at the pressure in p.s.i.g. at which the flow capacity is determined shall be stamped on the device. The fusible vent or vents shall have their flow rating determined at 5 p.s.i.g. differential.

(1) These flow tests may be conducted by the manufacturer or may be delegated to a certified outside agency. [Order 73, 32 F.R. 3463, Mar. 2, 1967]

§ 178.341-5 Emergency flow control.

(a) Each product discharge opening shall be equipped with a self-closing shutoff valve, designed, installed, and protected in accordance with § 178.340-8(d) and operated so as to assure against the accidental escape of contents. 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 within the welded flange, its companion flange, nozzle, or coupling. Such product discharge valves (outflow) shall, in addition to normal means, be closed by (1) an automatic heat actuated means which will become effective at a temperature not over 250° F., (2) a secondary closing means, remote from tank fill

in event of fire or other accident. [Order 73, 32 F.R. 3464, Mar. 2, 1967]

§ 178.341-6

Gauging devices.

(a) No applicable provisions. [Order 73, 32 F.R. 3464, Mar. 2, 1967]

§ 178.341-7 Method of test.

(a) Test for leaks. Every cargo tank shall be tested by a minimum air or hydrostatic pressure of 3 p.s.i.g. or at least equal to the tank design pressure of § 178.341-1(b) whichever is greater applied to the whole tank and dome if it be noncompartmented. If compartmented each individual compartment shall be similarly tested with adjacent compartments empty and at atmospheric pressure. Air pressure, if used, shall be held for a period of at least 5 minutes during which the entire surface of all joints under pressure shall be coated with a solution of soap and water, heavy oil, or other material suitable for the purpose, foaming or bubbling of which indicates the presence of leaks. Hydrostatic pressure, if used, shall be done by using water or other liquid having a similar viscosity, the temperature of which shall not exceed 100° F. during the test, and applying pressure as prescribed above, gauged at the top of the tank, at which time all joints under pressure shall be inspected for the issuance of liquid to indicate leaks. All closures shall be in place while test by either method is made. During these tests, operative relief devices shall be clamped, plugged, or otherwise rendered inoperative; such clamps, plugs, and similar devices shall be removed immediately after the test is finished. Any leakage discovered by either of the methods above described, or by any other method, shall be deemed evidence of failure to meet the requirements of this specification. Tanks failing to pass this test shall be suitably repaired, and the above described tests shall be continued until no leaks are discovered, before any cargo tank is put into service.

(b) Test for distortion or failure. Every cargo tank shall be tested by pressures prescribed in paragraph (a) of this section and shall withstand such pressure without undue distortion, evidence of impending failure, or failure. Failure to meet this requirement shall be deemed as sufficient cause for rejection under this specification. If there is undue distortion, or if failure impends or occurs,

returned to service unless an adequate repair is made. The adequacy of the repair shall be determined by the same method of test.

[Order 73, 32 F.R. 3464, Mar. 2, 1967]

§ 178.342 Specification MC 307; cargo tanks.

[Order 73, 32 F.R. 3464, Mar. 2, 1967]

§ 178.342-1 General requirements.

(a) Specification MC 307 cargo tanks must comply with the general design and construction requirements in § 178.340, in addition to the specific design requirements contained in this section.

(b) The design pressure (maximum allowable working pressure) of each cargo tank shall be not less than 25 p.s.i.g. For working pressures in excess of 50 p.s.i.g. the tank must be designed in accordance with the requirements of the ASME Code.

(c) Tanks shall be of circular crosssection.

[Order 73, 32 F.R. 3464, Mar. 2, 1967, as amended by Amdt. 178-7, 34 F.R. 18251, Nov. 14, 1969]

§ 178.342–2 Thickness of shell, heads, bulkheads, and baffles.

(a) Material thickness. The minimum thicknesses of tank material authorized in § 178.340-3 shall be not less than those obtained by applying the following formulas nor less than those specified in Tables I and II below:

SW

Thickness...

10 or less

Over 10 to 14

14 to 18

18 to 22

22 to 26

AL

MS

HSLA, SS

AL

SW

HSLA, SS

AL

MS

Inches

36 or less.

Over 36 to 54.. 54 through 60..

(1) The knuckle radius of the head shall not be less than three times the material thickness. The straight flange shall not be less than three times the material thickness for butt-welded heads.

(2) For heads with pressure on the convex side, the material thickness as obtained by the above formula shall be increased by 67 percent unless such heads are adequately braced to prevent excessive distortion.

(b) Corrosion allowance. Vessels or part of vessels subject to thinning by corrosion, erosion, or mechanical abrasion, shall have provision made to withstand the intended life and service by a suitable increase in the thickness of the material over that determined by the design formulas, or by using some other suitable method of protection. Material added for these purposes need not be of the same thickness for all parts of the vessel if different rates of attack are expected for the various parts.

[Order 73, 32 F.R. 3464, Mar. 2, 1967]

Closures for manholes.

(a) Each compartment shall be accessible through a 15-inch minimum inside diameter manhole. 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. Gaskets, if used, shall be of suitable material not subject to attack by lading.

(1) Closures shall have structural capability of withstanding internal fluid pressures of 40 p.s.i.g. or 1.5 times the design pressure of the tank whichever is greater without permanent deformation. Safety devices to prevent the manhole and/or fill cover from opening fully when internal pressure is present shall be provided.

[Order 73, 32 F.R. 3465, Mar. 2, 1967] § 178.342-4

Vents.

(a) Each cargo tank compartment shall be provided with safety relief devices in accordance with the requirements contained in this paragraph. All

AL