--- kind: "range" citation: "49 C.F.R. §§ 178.337-1–178.337-18" title: "49" from: "178.337-1" to: "178.337-18" count: 18 url: "https://uscodex.org/cfr/49/178.337-1..178.337-18" --- # §178.337-1. General requirements. - (a) **ASME Code construction.** Tanks must be— - (1) Seamless or welded construction, or a combination of both; - (2) Designed, constructed, certified, and stamped in accordance with Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter); - (3) Made of steel or aluminum; however, if aluminum is used, the cargo tank must be insulated and the hazardous material to be transported must be compatible with the aluminum (see §§ [178.337-1(e)(2)](#e-2), [173.315(a)](/cfr/49/173.315.md?p=a) table, and 178.337-2(a)(1) of this subchapter); and - (4) Covered with a steel jacket if the cargo tank is insulated and used to transport a flammable gas (see [§ 173.315(a)](/cfr/49/173.315.md?p=a) table Note 11 of this subchapter). - (b) **Design pressure.** The design pressure of a cargo 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 in [§ 173.315(a)](/cfr/49/173.315.md?p=a) of this subchapter, except that in no case shall the design pressure of any cargo tank be less than 100 p.s.i.g. nor more than 500 p.s.i.g. - (c) **Openings.** - (1) Excess pressure relief valves shall be located in the top of the cargo tank or heads. - (2) A chlorine cargo tank shall have only one opening. That opening shall be in the top of the cargo tank and shall be fitted with a nozzle that meets the following requirements: - (i) On a cargo tank manufactured on or before December 31, 1974, the nozzle shall be protected by a dome cover plate which conforms to either the standard of The Chlorine Institute, Inc., Dwg. 103-3, dated January 23, 1958, or to the standard specified in [paragraph (c)](#c) (2) (ii) of this section. - (ii) On a cargo tank manufactured on or after January 1, 1975, the nozzle shall be protected by a manway cover which conforms to the standard of The Chlorine Institute, Inc., Dwg. 103-4, dated September 1, 1971. - (d) **Reflective design.** Every uninsulated cargo tank permanently attached to a cargo tank motor vehicle shall, unless covered with a jacket made of aluminum, stainless steel, or other bright non-tarnishing metal, be white, aluminum, or a similar reflecting color on the upper two-thirds of area of the cargo tank. - (e) **Insulation.** - (1) Each cargo tank required to be insulated must conform with the use and performance requirements contained in [§§ 173.315(a)](/cfr/49/173.315.md?p=a) table and 178.337-1 (a)(3) and (e)(2) of this subchapter. - (2) Each cargo tank intended for chlorine; carbon dioxide, refrigerated liquid; or nitrous oxide, refrigerated liquid service must have suitable insulation of such thickness that the overall thermal conductance is not more than 0.08 Btu per square foot per °F differential per hour. The conductance must be determined at 60 °F. Insulation material used on cargo tanks for nitrous oxide, refrigerated liquid must be noncombustible. Insulating material used on cargo tanks for chlorine must be corkboard or polyurethane foam, with a minimum thickness of 4 inches, or 2 inches minimum thickness of ceramic fiber/fiberglass of 4 pounds per cubic foot minimum density covered by 2 inches minimum thickness of fiber. - (f) **Postweld heat treatment.** Postweld heat treatment must be as prescribed in the ASME Code except that each cargo tank constructed in accordance with Part UHT of Section VIII of the ASME Code must be postweld heat treated. Each chlorine cargo tank must be fully radiographed and postweld heat treated in accordance with the provisions in Section VIII of the ASME Code under which it is constructed. Where postweld heat treatment is required, the cargo tank must be treated as a unit after completion of all the welds in and/or to the shells and heads. The method must be as prescribed in Section VIII of the ASME Code. Welded attachments to pads may be made after postweld heat treatment. A cargo tank used for anhydrous ammonia must be postweld heat treated. The postweld heat treatment must be as prescribed in Section VIII of the ASME Code, but in no event at less than 1,050 °F cargo tank metal temperature. - (g) **Definitions.** The following definitions apply to [§§ 178.337-1 through 178.337-18](/cfr/49/178.337-1..178.337-18.md): Emergency discharge control means the ability to stop a cargo tank unloading operation in the event of an unintentional release. Emergency discharge control can utilize passive or off-truck remote means to stop the unloading operation. A passive means of emergency discharge control automatically shuts off the flow of product without the need for human intervention within 20 seconds of an unintentional release caused by a complete separation of the liquid delivery hose. An off-truck remote means of emergency discharge control permits a qualified person attending the unloading operation to close the cargo tank's internal self-closing stop valve and shut off all motive and auxiliary power equipment at a distance from the cargo tank motor vehicle. Excess flow valve, integral excess flow valve, or excess flow feature means a component that will close automatically if the flow rate of a gas or liquid through the component reaches or exceeds the rated flow of gas or liquid specified by the original valve manufacturer when piping mounted directly on the valve is sheared off before the first valve, pump, or fitting downstream from the valve. Internal self-closing stop valve means a primary shut off valve installed in a product discharge outlet of a cargo tank and designed to be kept closed by self-stored energy. Primary discharge control system means a primary shut-off installed at a product discharge outlet of a cargo tank consisting of an internal self-closing stop valve that may include an integral excess flow valve or an excess flow feature, together with linkages that must be installed between the valve and remote actuator to provide manual and thermal on-truck remote means of closure. # §178.337-2. Material. - (a) **General.** - (1) All material used for construction of the cargo tank and appurtenances must be suitable for use with the commodities to be transported therein and must conform to the requirements in Section II of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter) and/or requirements of the American Society for Testing and Materials in all respects. - (2) Impact tests are required on steel used in the fabrication of each cargo tank constructed in accordance with part UHT in Section VIII of the ASME Code. The tests must be made on a lot basis. A lot is defined as 100 tons or less of the same heat treatment processing lot having a thickness variation no greater than plus or minus 25 percent. The minimum impact required for full size specimens must be 20 foot-pounds in the longitudinal direction at −30 °F., Charpy V-Notch and 15 foot-pounds in the transverse direction at −30 °F., Charpy V-Notch. The required values for subsize specimens must be reduced in direct proportion to the cross-sectional area of the specimen beneath the notch. If a lot does not meet this requirement, individual plates may be accepted if they individually meet this requirement. - (3) The fabricator shall record the heat, and slab numbers, and the certified Charpy impact values, where required, of each plate used in each cargo tank on a sketch showing the location of each plate in the shell and heads of the cargo tank. Copies of each sketch shall be provided to the owner and retained for at least five years by the fabricator and made available to duly identified representatives of the Department of Transportation. - (4) The direction of final rolling of the shell material shall be the circumferential orientation of the cargo tank shell. - (b) **For a chlorine cargo tank.** Plates, the manway nozzle, and anchorage shall be made of carbon steel which meets the following requirements: - (1) **For a cargo tank manufactured on or before December 31, 1974—** - (i) Material shall conform to ASTM A 300, “Steel Plates for Pressure Vessels for Service at Low Temperatures” (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter); - (ii) Material shall be Class 1, Grade A, flange or firebox quality; - (iii) Plate impact test specimens, as required under [paragraph (a)](#a) of this section, shall be of the Charpy keyhole notch type; and - (iv) Plate impact test specimens shall meet the impact test requirements in [paragraph (a)](#a) of this section in both the longitudinal and transverse directions of rolling at a temperature of minus 45.5 C. (−50 °F.). - (2) **For a cargo tank manufactured on or after January 1, 1975—** - (i) Material shall conform to ASTM A 612 (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), Grade B or A 516/A 516M (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), Grade 65 or 70; - (ii) Material shall meet the Charpy V-notch test requirements of ASTM A 20/A 20M (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter); and - (iii) Plate impact test specimens shall meet the impact test requirements in [paragraph (a)](#a) of this section in both the longitudinal and transverse directions of rolling at a temperature of minus 40 °C. (−40 °F.). - (c) A cargo tank in anhydrous ammonia service must be constructed of steel. The use of copper, silver, zinc or their alloys is prohibited. Baffles made from aluminum may be used only if joined to the cargo tank by a process not requiring postweld heat treatment of the cargo tank. # §178.337-3. Structural integrity. - (a) **General requirements and acceptance criteria.** - (1) Except as provided in [paragraph (d)](#d) of this section, the maximum calculated design stress at any point in the cargo tank may not exceed the maximum allowable stress value prescribed in Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), or 25 percent of the tensile strength of the material used. - (2) The relevant physical properties of the materials used in each cargo tank may be established either by a certified test report from the material manufacturer or by testing in conformance with a recognized national standard. In either case, the ultimate tensile strength of the material used in the design may not exceed 120 percent of the ultimate tensile strength specified in either the ASME Code or the ASTM standard to which the material is manufactured. - (3) The maximum design stress at any point in the cargo tank must be calculated separately for the loading conditions described in paragraphs [(b)](#b), [(c)](#c), and [(d)](#d) of this section. Alternate test or analytical methods, or a combination thereof, may be used in place of the procedures described in paragraphs [(b)](#b), [(c)](#c), and [(d)](#d) of this section, if the methods are accurate and verifiable. - (4) Corrosion allowance material may not be included to satisfy any of the design calculation requirements of this section. - (b) **Static design and construction.** - (1) The static design and construction of each cargo tank must be in accordance with Section VIII of the ASME Code. The cargo tank design must include calculation of stresses generated by design pressure, the weight of lading, the weight of structure supported by the cargo tank wall, and the effect of temperature gradients resulting from lading and ambient temperature extremes. When dissimilar materials are used, their thermal coefficients must be used in calculation of thermal stresses. - (2) Stress concentrations in tension, bending and torsion which occur at pads, cradles, or other supports must be considered in accordance with appendix G in Section VIII of the ASME Code. - (c) **Shell design.** Shell stresses resulting from static or dynamic loadings, or combinations thereof, are not uniform throughout the cargo tank motor vehicle. The vertical, longitudinal, and lateral normal operating loadings can occur simultaneously and must be combined. The vertical, longitudinal and lateral extreme dynamic loadings occur separately and need not be combined. - (1) **Normal operating loadings.** The following procedure addresses stress in the tank shell resulting from normal operating loadings. The effective stress (the maximum principal stress at any point) must be determined by the following formula: - (i) S = effective stress at any given point under the combination of static and normal operating loadings that can occur at the same time, in psi. - (ii) Sy = circumferential stress generated by the MAWP and external pressure, when applicable, plus static head, in psi. - (iii) Sx = The following net longitudinal stress generated by the following static and normal operating loading conditions, in psi: - (A) The longitudinal stresses resulting from the MAWP and external pressure, when applicable, plus static head, in combination with the bending stress generated by the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; - (B) The tensile or compressive stress resulting from normal operating longitudinal acceleration or deceleration. In each case, the forces applied must be 0.35 times the vertical reaction at the suspension assembly, applied at the road surface, and as transmitted to the cargo tank wall through the suspension assembly of a trailer during deceleration; or the horizontal pivot of the truck tractor or converter dolly fifth wheel, or the drawbar hinge on the fixed dolly during acceleration; or anchoring and support members of a truck during acceleration and deceleration, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall. The following loadings must be included: (1) The axial load generated by a decelerative force; (2) The bending moment generated by a decelerative force; (3) The axial load generated by an accelerative force; and (4) The bending moment generated by an accelerative force; and - (C) The tensile or compressive stress generated by the bending moment resulting from normal operating vertical accelerative force equal to 0.35 times the vertical reaction at the suspension assembly of a trailer; or the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall. - (iv) Ss = The following shear stresses generated by the following static and normal operating loading conditions, in psi: - (A) The static shear stress resulting from the vertical reaction at the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; - (B) The vertical shear stress generated by a normal operating accelerative force equal to 0.35 times the vertical reaction at the suspension assembly of a trailer; or the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; - (C) The lateral shear stress generated by a normal operating lateral accelerative force equal to 0.2 times the vertical reaction at each suspension assembly of a trailer, applied at the road surface, and as transmitted to the cargo tank wall through the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; and - (D) The torsional shear stress generated by the same lateral forces as described in [paragraph (c)(1)(iv)(C)](#c-1-iv-C) of this section. - (2) **Extreme dynamic loadings.** The following procedure addresses stress in the tank shell resulting from extreme dynamic loadings. The effective stress (the maximum principal stress at any point) must be determined by the following formula: - (i) S = effective stress at any given point under a combination of static and extreme dynamic loadings that can occur at the same time, in psi. - (ii) Sy = circumferential stress generated by MAWP and external pressure, when applicable, plus static head, in psi. - (iii) Sx = the following net longitudinal stress generated by the following static and extreme dynamic loading conditions, in psi: - (A) The longitudinal stresses resulting from the MAWP and external pressure, when applicable, plus static head, in combination with the bending stress generated by the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the tank wall; - (B) **The tensile or compressive stress resulting from extreme longitudinal acceleration or deceleration.** In each case the forces applied must be 0.7 times the vertical reaction at the suspension assembly, applied at the road surface, and as transmitted to the cargo tank wall through the suspension assembly of a trailer during deceleration; or the horizontal pivot of the truck tractor or converter dolly fifth wheel, or the drawbar hinge on the fixed dolly during acceleration; or the anchoring and support members of a truck during acceleration and deceleration, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall. The following loadings must be included: (1) The axial load generated by a decelerative force; (2) The bending moment generated by a decelerative force; (3) The axial load generated by an accelerative force; and (4) The bending moment generated by an accelerative force; and - (C) The tensile or compressive stress generated by the bending moment resulting from an extreme vertical accelerative force equal to 0.7 times the vertical reaction at the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or turntable; or the anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall. - (iv) Ss = The following shear stresses generated by static and extreme dynamic loading conditions, in psi: - (A) The static shear stress resulting from the vertical reaction at the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; - (B) The vertical shear stress generated by an extreme vertical accelerative force equal to 0.7 times the vertical reaction at the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; - (C) The lateral shear stress generated by an extreme lateral accelerative force equal to 0.4 times the vertical reaction at the suspension assembly of a trailer, applied at the road surface, and as transmitted to the cargo tank wall through the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or turntable; or anchoring and support members of a truck, as applicable. The vertical reaction must be calculated based on the static weight of the fully loaded cargo tank motor vehicle, all structural elements, equipment and appurtenances supported by the cargo tank wall; and - (D) The torsional shear stress generated by the same lateral forces as described in [paragraph (c)(2)(iv)(C)](#c-2-iv-C) of this section. - (d) In order to account for stresses due to impact in an accident, the design calculations for the cargo tank shell and heads must include the load resulting from the design pressure in combination with the dynamic pressure resulting from a longitudinal deceleration of “2g”. For this loading condition the stress value used may not exceed the lesser of the yield strength or 75 percent of the ultimate tensile strength of the material of construction. For cargo tanks constructed of stainless steel the maximum design stress may not exceed 75 percent of the ultimate tensile strength of the type steel used. - (e) The minimum metal thickness for the shell and heads on tanks with a design pressure of 100 psig or more must be 4.75 mm (0.187 inch) for steel and 6.86 mm (0.270 inch) for aluminum, except for chlorine and sulfur dioxide tanks. In all cases, the minimum thickness of the tank shell and head shall be determined using structural design requirements in Section VIII of the ASME Code or 25% of the tensile strength of the material used. For a cargo tank used in chlorine or sulfur dioxide service, the cargo tank must be made of steel. A corrosion allowance of 20 percent or 2.54 mm (0.10 inch), whichever is less, must be added to the thickness otherwise required for sulfur dioxide and chlorine tank material. In chlorine cargo tanks, the wall thickness must be at least 1.59 cm (0.625 inch), including corrosion allowance. - (f) Where a cargo tank support is attached to any part of the cargo tank wall, the stresses imposed on the cargo tank wall must meet the requirements in [paragraph (a)](#a) of this section. - (g) The design, construction, and installation of an attachment, appurtenance to the cargo tank, structural support member between the cargo tank and the vehicle or suspension component, or accident protection device must conform to the following requirements: - (1) Structural members, the suspension sub-frame, accident protection structures, and external circumferential reinforcement devices must be used as sites for attachment of appurtenances and other accessories to the cargo tank, when practicable. - (2) A lightweight attachment to the cargo tank wall such as a conduit clip, brake line clip, skirting structure, lamp mounting bracket, or placard holder must be of a construction having lesser strength than the cargo tank wall materials and may not be more than 72 percent of the thickness of the material to which it is attached. The lightweight attachment may be secured directly to the cargo tank wall if the device is designed and installed in such a manner that, if damaged, it will not affect the lading retention integrity of the tank. A lightweight attachment must be secured to the cargo tank shell or head by a continuous weld or in such a manner as to preclude formation of pockets which may become sites for corrosion. Attachments meeting the requirements of this paragraph are not authorized for cargo tanks constructed under part UHT in Section VIII of the ASME Code. - (3) Except as prescribed in paragraphs [(g)(1)](#g-1) and [(g)(2)](#g-2) of this section, the welding of any appurtenance to the cargo tank wall must be made by attachment of a mounting pad so that there will be no adverse effect upon the lading retention integrity of the cargo tank if any force less than that prescribed in [paragraph (b)(1)](#b-1) of this section is applied from any direction. The thickness of the mounting pad may not be less than that of the shell wall or head wall to which it is attached, and not more than 1.5 times the shell or head thickness. However, a pad with a minimum thickness of 0.25 inch may be used when the shell or head thickness is over 0.25 inch. If weep holes or tell-tale holes are used, the pad must be drilled or punched at the lowest point before it is welded to the tank. Each pad must— - (i) Be fabricated from material determined to be suitable for welding to both the cargo tank material and the material of the appurtenance or structural support member; a Design Certifying Engineer must make this determination considering chemical and physical properties of the materials and must specify filler material conforming to the requirements in Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter). - (ii) Be preformed to an inside radius no greater than the outside radius of the cargo tank at the attachment location. - (iii) Extend at least 2 inches in each direction from any point of attachment of an appurtenance or structural support member. This dimension may be measured from the center of the attached structural member. - (iv) Have rounded corners, or otherwise be shaped in a manner to minimize stress concentrations on the shell or head. - (v) **Be attached by continuous fillet welding.** Any fillet weld discontinuity may only be for the purpose of preventing an intersection between the fillet weld and a tank or jacket seam weld. # §178.337-4. Joints. - (a) Joints shall be as required in Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), with all undercutting in shell and head material repaired as specified therein. - (b) Welding procedure and welder performance must be in accordance with Section IX of the ASME Code. In addition to the essential variables named therein, the following must be considered as essential variables: Number of passes; thickness of plate; heat input per pass; and manufacturer's identification of rod and flux. When fabrication is done in accordance with part UHT in Section VIII of the ASME Code, filler material containing more than 0.08 percent vanadium must not be used. The number of passes, thickness of plate, and heat input per pass may not vary more than 25 percent from the procedure or welder qualifications. Records of the qualifications must be retained for at least 5 years by the cargo tank manufacturer and must be made available to duly identified representatives of the Department and the owner of the cargo tank. - (c) All longitudinal shell welds shall be located in the upper half of the cargo tank. - (d) Edge preparation of shell and head components may be by machine heat processes, provided such surfaces are remelted in the subsequent welding process. Where there will be no subsequent remelting of the prepared surface as in a tapered section, the final 0.050 inch of material shall be removed by mechanical means. - (e) The maximum tolerance for misalignment and butting up shall be in accordance with the requirement in Section VIII of the ASME Code. - (f) Substructures shall be properly fitted before attachment, and the welding sequence shall be such as to minimize stresses due to shrinkage of welds. # §178.337-5. Bulkheads, baffles and ring stiffeners. - (a) **Not a specification requirement.** - (b) [Reserved] # §178.337-6. Closure for manhole. - (a) Each cargo tank marked or certified after April 21, 1994, must be provided with a manhole conforming to paragraph UG-46(g)(1) and other applicable requirements in Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), except that a cargo tank constructed of NQT steel having a capacity of 3,500 water gallons or less may be provided with an inspection opening conforming to paragraph UG-46 and other applicable requirements of the ASME Code instead of a manhole. - (b) The manhole assembly of cargo tanks constructed after June 30, 1979, may not be located on the front head of the cargo tank. # §178.337-7. Overturn protection. - (a) See [§ 178.337-10](/cfr/49/178.337-10.md). - (b) [Reserved] # §178.337-8. Openings, inlets, and outlets. - (a) **General.** The requirements in this [paragraph (a)](#a) apply to MC 331 cargo tanks except for those used to transport chlorine. The requirements for inlets and outlets on chlorine cargo tanks are in [paragraph (b)](#b) of this section. - (1) An opening must be provided on each cargo tank used for the transportation of liquefied materials to permit complete drainage. - (2) Except for gauging devices, thermometer wells, pressure relief valves, manhole openings, product inlet openings, and product discharge openings, each opening in a cargo tank must be closed with a plug, cap, or bolted flange. - (3) Except as provided in [paragraph (b)](#b) of this section, each product inlet opening, including vapor return lines, must be fitted with a back flow check valve or an internal self-closing stop valve located inside the cargo tank or inside a welded nozzle that is an integral part of the cargo tank. The valve seat must be located inside the cargo tank or within 2.54 cm (one inch) of the external face of the welded flange. Damage to parts exterior to the cargo tank or mating flange must not prevent effective seating of the valve. All parts of a valve inside a cargo tank or welded flange must be made of material that will not corrode or deteriorate in the presence of the lading. - (4) Except as provided in paragraphs [(a)(5)](#a-5), (b), and (c) of this section, each liquid or vapor discharge outlet must be fitted with a primary discharge control system as defined in [§ 178.337-1(g)](/cfr/49/178.337-1.md?p=g). Thermal remote operators must activate at a temperature of 121.11 °C (250 °F) or less. Linkages between closures and remote operators must be corrosion resistant and effective in all types of environmental conditions incident to discharging of product. - (i) On a cargo tank over 13,247.5 L (3,500 gallons) water capacity, thermal and mechanical means of remote closure must be installed at the ends of the cargo tank in at least two diagonally opposite locations. If the loading/unloading connection at the cargo tank is not in the general vicinity of one of the two locations specified in the first sentence of this [paragraph (a)(4)(i)](#a-4-i), additional means of thermal remote closure must be installed so that heat from a fire in the loading/unloading connection area or the discharge pump will activate the primary discharge control system. The loading/unloading connection area is where hoses or hose reels are connected to the permanent metal piping. - (ii) On a cargo tank of 13,247.5 L (3,500 gallons) water capacity or less, a thermal means of remote closure must be installed at or near the internal self-closing stop valve. A mechanical means of remote closure must be installed on the end of the cargo tank furthest away from the loading/unloading connection area. The loading/unloading connection area is where hoses or hose reels are connected to the permanent metal piping. Linkages between closures and remote operators must be corrosion resistant and effective in all types of environmental conditions incident to discharge of product. - (iii) All parts of a valve inside a cargo tank or within a welded flange must be made of material that will not corrode or deteriorate in the presence of the lading. - (iv) An excess flow valve, integral excess flow valve, or excess flow feature must close if the flow reaches the rated flow of a gas or liquid specified by the original valve manufacturer when piping mounted directly on the valve is sheared off before the first valve, pump, or fitting downstream from the excess flow valve, integral excess flow valve, or excess flow feature. - (v) An integral excess flow valve or the excess flow feature of an internal self-closing stop valve may be designed with a bypass, not to exceed 0.1016 cm (0.040 inch) diameter opening, to allow equalization of pressure. - (vi) The internal self-closing stop valve must be designed so that the self-stored energy source and the valve seat are located inside the cargo tank or within 2.54 cm (one inch) of the external face of the welded flange. Damage to parts exterior to the cargo tank or mating flange must not prevent effective seating of the valve. - (5) **A primary discharge control system is not required on the following—** - (i) A vapor or liquid discharge opening of less than 1 1/4 NPT equipped with an excess flow valve together with a manually operated external stop valve in place of an internal self-closing stop valve. - (ii) An engine fuel line on a truck-mounted cargo tank of not more than 3/4 NPT equipped with a valve having an integral excess flow valve or excess flow feature. - (iii) A cargo tank motor vehicle used to transport refrigerated liquids such as argon, carbon dioxide, helium, krypton, neon, nitrogen, and xenon, or mixtures thereof. - (6) In addition to the internal self-closing stop valve, each filling and discharge line must be fitted with a stop valve located in the line between the internal self-closing stop valve and the hose connection. A back flow check valve or excess flow valve may not be used to satisfy this requirement. - (7) An excess flow valve may be designed with a bypass, not to exceed a 0.1016 centimeter (0.040 inch) diameter opening, to allow equalization of pressure. - (b) **Inlets and discharge outlets on chlorine tanks.** The inlet and discharge outlets on a cargo tank used to transport chlorine must meet the requirements of [§ 178.337-1(c)(2)](/cfr/49/178.337-1.md?p=c-2) and must be fitted with an internal excess flow valve. In addition to the internal excess flow valve, the inlet and discharge outlets must be equipped with an external stop valve (angle valve). Excess flow valves must conform to the standards of The Chlorine Institute, Inc., as follows: - (1) A valve conforming to The Chlorine Institute, Inc., Dwg. 101-7 (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), must be installed under each liquid angle valve. - (2) A valve conforming to The Chlorine Institute, Inc., Dwg. 106-6 (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), must be installed under each gas angle valve. - (c) **Discharge outlets on carbon dioxide, refrigerated liquid, cargo tanks.** A discharge outlet on a cargo tank used to transport carbon dioxide, refrigerated liquid is not required to be fitted with an internal self-closing stop valve. # §178.337-9. Pressure relief devices, piping, valves, hoses, and fittings. - (a) **Pressure relief devices.** - (1) See [§ 173.315(i)](/cfr/49/173.315.md?p=i) of this subchapter. - (2) On cargo tanks for carbon dioxide or nitrous oxide see [§ 173.315 (i)](/cfr/49/173.315.md?p=i) (9) and (10) of this subchapter. - (3) Each valve must be designed, constructed, and marked for a rated pressure not less than the cargo tank design pressure at the temperature expected to be encountered. - (b) **Piping, valves, hose, and fittings.** - (1) The burst pressure of all piping, pipe fittings, hose and other pressure parts, except for pump seals and pressure relief devices, must be at least 4 times the design pressure of the cargo tank. Additionally, the burst pressure may not be less than 4 times any higher pressure to which each pipe, pipe fitting, hose or other pressure part may be subjected to in service. For chlorine service, see [paragraph (b)(7)](#b-7) of this section. - (2) Pipe joints must be threaded, welded, or flanged. If threaded pipe is used, the pipe and fittings must be Schedule 80 weight or heavier, except for sacrificial devices. Malleable metal, stainless steel, or ductile iron must be used in the construction of primary valve body parts and fittings used in liquid filling or vapor equalization. Stainless steel may be used for internal components such as shutoff discs and springs except where incompatible with the lading to be transported. Where copper tubing is permitted, joints must be brazed or be of equally strong metal union type. The melting point of the brazing material may not be lower than 538 °C (1,000 °F). The method of joining tubing may not reduce the strength of the tubing. - (3) Each hose coupling must be designed for a pressure of at least 120 percent of the hose design pressure and so that there will be no leakage when connected. - (4) Piping must be protected from damage due to thermal expansion and contraction, jarring, and vibration. Slip joints are not authorized for this purpose. - (5) [Reserved] - (6) Cargo tank manufacturers and fabricators must demonstrate that all piping, valves, and fittings on a cargo tank are free from leaks. To meet this requirement, the piping, valves, and fittings must be tested after installation at not less than 80 percent of the design pressure marked on the cargo tank. - (7) **A hose assembler must—** - (i) **Permanently mark each hose assembly with a unique identification number.** - (ii) Demonstrate that each hose assembly is free from leaks by performing the tests and inspections in [§ 180.416(f)](/cfr/49/180.416.md?p=f) of this subchapter. - (iii) **Mark each hose assembly with the month and year of its original pressure test.** - (8) **Chlorine cargo tanks.** Angle valves on cargo tanks intended for chlorine service must conform to the standards of the Chlorine Institute, Inc., Drawing; Dwg. 104-8; or “[Section 3](/cfr/49/3.md), Pamphlet 166, Angle Valve Guidelines for Chlorine Bulk Transportation;” or “[Sections 4 through 6](/cfr/49/4..6.md), Pamphlet 168, Guidelines for Dual Valve Systems for Bulk Chlorine Transport” (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter). Before installation, each angle valve must be tested for leakage at not less than 225 psig using dry air or inert gas. - (c) **Marking inlets and outlets.** Except for gauging devices, thermometer wells, and pressure relief valves, each cargo tank inlet and outlet must be marked “liquid” or “vapor” to designate whether it communicates with liquid or vapor when the cargo tank is filled to the maximum permitted filling density. A filling line that communicates with vapor may be marked “spray-fill” instead of “vapor.” - (d) **Refrigeration and heating coils.** - (1) Refrigeration and heating coils must be securely anchored with provisions for thermal expansion. The coils must be pressure tested externally to at least the cargo tank test pressure, and internally to either the tank test pressure or twice the working pressure of the heating/refrigeration system, whichever is higher. A cargo tank may not be placed in service if any leakage occurs or other evidence of damage is found. The refrigerant or heating medium to be circulated through the coils must not be capable of causing any adverse chemical reaction with the cargo tank lading in the event of leakage. The unit furnishing refrigeration may be mounted on the motor vehicle. - (2) Where any liquid susceptible to freezing, or the vapor of any such liquid, is used for heating or refrigeration, the heating or refrigeration system shall be arranged to permit complete drainage. # §178.337-10. Accident damage protection. - (a) All valves, fittings, pressure relief devices, and other accessories to the tank proper shall be protected in accordance with [paragraph (b)](#b) of this section against such damage as could be caused by collision with other vehicles or objects, jack-knifing and overturning. In addition, pressure relief valves shall be so protected that in the event of overturn of the vehicle onto a hard surface, their opening will not be prevented and their discharge will not be restricted. - (b) The protective devices or housing must be designed to withstand static loading in any direction equal to twice the weight of the tank and attachments when filled with the lading, using a safety factor of not less than four, based on the ultimate strength of the material to be used, without damage to the fittings protected, and must be made of metal at least 3/16-inch thick. - (c) **Rear-end tank protection.** Rear-end tank protection devices must: - (1) Consist of at least one rear bumper designed to protect the cargo tank and all valves, piping and fittings located at the rear of the cargo tank from damage that could result in loss of lading in the event of a rear end collision. The bumper design must transmit the force of the collision directly to the chassis of the vehicle. The rear bumper and its attachments to the chassis must be designed to withstand a load equal to twice the weight of the loaded cargo tank motor vehicle and attachments, using a safety factor of four based on the tensile strength of the materials used, with such load being applied horizontally and parallel to the major axis of the cargo tank. The rear bumper dimensions must also meet the requirements of [§ 393.86](/cfr/49/393.86.md) of this title; or - (2) Conform to the requirements of [§ 178.345-8(d)](/cfr/49/178.345-8.md?p=d). - (d) **Chlorine tanks.** A chlorine tank must be equipped with a protective housing and a manway cover to permit the use of standard emergency kits for controlling leaks in fittings on the dome cover plate. For tanks manufactured on or after October 1, 2009, the housing and manway cover must conform to the Chlorine Institute, Inc., Dwg. 137-5 (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter). - (e) **Piping and fittings.** Piping and fittings must be grouped in the smallest practicable space and protected from damage as required in this section. - (f) **Shear section.** A shear section or sacrificial device is required for the valves specified in the following locations: - (1) A section that will break under strain must be provided adjacent to or outboard of each valve specified in § [178.337-8(a)(3)](/cfr/49/178.337-8.md?p=a-3) and [(4)](/cfr/49/178.337-8.md?p=a-4). - (2) Each internal self-closing stop valve, excess flow valve, and check valve must be protected by a shear section or other sacrificial device. The sacrificial device must be located in the piping system outboard of the stop valve and within the accident damage protection to prevent any accidental loss of lading. The failure of the sacrificial device must leave the protected lading protection device and its attachment to the cargo tank wall intact and capable of retaining product. # §178.337-11. Emergency discharge control. - (a) **Emergency discharge control equipment.** Emergency discharge control equipment must be installed in a liquid discharge line as specified by product and service in [§ 173.315(n)](/cfr/49/173.315.md?p=n) of this subchapter. The performance and certification requirements for emergency discharge control equipment are specified in [§ 173.315(n)](/cfr/49/173.315.md?p=n) of this subchapter and are not a part of the cargo tank motor vehicle certification made under this specification. - (b) **Engine fuel lines.** On a truck-mounted cargo tank, emergency discharge control equipment is not required on an engine fuel line of not more than 3/4 NPT equipped with a valve having an integral excess flow valve or excess flow feature. # §178.337-12. Reserved # §178.337-13. Supporting and anchoring. - (a) A cargo tank that is not permanently attached to or integral with a vehicle chassis must be secured by the use of restraining devices designed to prevent relative motion between the cargo tank and the vehicle chassis when the vehicle is in operation. Such restraining devices must be readily accessible for inspection and maintenance. - (b) On a cargo tank motor vehicle designed and constructed so that the cargo tank constitutes in whole or in part the structural member used in place of a motor vehicle frame, the cargo tank must be supported by external cradles. A cargo tank mounted on a motor vehicle frame must be supported by external cradles or longitudinal members. Where used, the cradles must subtend at least 120 degrees of the shell circumference. - (c) The design calculations of the support elements must satisfy the requirements of § [178.337-3](/cfr/49/178.337-3.md), [(a)](/cfr/49/178.337-3.md?p=a), [(b)](/cfr/49/178.337-3.md?p=b), [(c)](/cfr/49/178.337-3.md?p=c), and [(d)](/cfr/49/178.337-3.md?p=d). - (d) Where any cargo tank support is attached to any part of a cargo tank head, the stresses imposed upon the head must be provided for as required in [paragraph (c)](#c) of this section. # §178.337-14. Gauging devices. - (a) **Liquid level gauging devices.** See [§ 173.315(h)](/cfr/49/173.315.md?p=h) of this subchapter. - (b) **Pressure gauges.** - (1) See [§ 173.315(h)](/cfr/49/173.315.md?p=h) of this subchapter. - (2) Each cargo tank used in carbon dioxide, refrigerated liquid or nitrous oxide, refrigerated liquid service must be provided with a suitable pressure gauge. A shut-off valve must be installed between the pressure gauge and the cargo tank. - (c) **Orifices.** See [§ 173.315(h)](/cfr/49/173.315.md?p=h) (3) and (4) of this subchapter. # §178.337-15. Pumps and compressors. - (a) Liquid pumps or gas compressors, if used, must be of suitable design, adequately protected against breakage by collision, 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 centrifugal type, they shall be equipped with suitable pressure actuated by-pass valves permitting flow from discharge to suction or to the cargo tank. - (b) A liquid chlorine pump may not be installed on a cargo tank intended for the transportation of chlorine. # §178.337-16. Testing. - (a) **Inspection and tests.** Inspection of materials of construction of the cargo tank and its appurtenances and original test and inspection of the finished cargo tank and its appurtenances must be as required by Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter) and as further required by this specification, except that for cargo tanks constructed in accordance with part UHT in Section VIII of the ASME Code the original test pressure must be at least twice the cargo tank design pressure. - (b) **Weld testing and inspection.** - (1) Each cargo tank constructed in accordance with part UHT in Section VIII of the ASME Code must be subjected, after postweld heat treatment and hydrostatic tests, to a wet fluorescent magnetic particle inspection to be made on all welds in or on the cargo tank shell and heads both inside and out. The method of inspection must conform to appendix 6 in Section VIII of the ASME Code except that permanent magnets shall not be used. - (2) On cargo tanks of over 3,500 gallons water capacity other than those described in [paragraph (b)(1)](#b-1) of this section unless fully radiographed, a test must be made of all welds in or on the shell and heads both inside and outside by either the wet fluorescent magnetic particle method conforming to appendix U in Section VIII of the ASME Code, liquid dye penetrant method, or ultrasonic testing in accordance with appendix 12 in Section VIII of the ASME Code. Permanent magnets must not be used to perform the magnetic particle inspection. - (c) All defects found shall be repaired, the cargo tanks shall then again be postweld heat treated, if such heat treatment was previously performed, and the repaired areas shall again be tested. # §178.337-17. Marking. - (a) **General.** Each cargo tank certified after October 1, 2004 must have a corrosion-resistant metal name plate (ASME Plate); and each cargo tank motor vehicle certified after October 1, 2004 must have a specification plate, permanently attached to the cargo tank by brazing, welding, or other suitable means on the left side near the front, in a place accessible for inspection. If the specification plate is attached directly to the cargo tank wall by welding, it must be welded to the tank before the cargo tank is postweld heat treated. - (1) The plates must be legibly marked by stamping, embossing, or other means of forming letters into the metal of the plate, with the information required in paragraphs [(b)](#b) and [(c)](#c) of this section, in addition to that required by the ASME Code, in characters at least 3/16 inch high (parenthetical abbreviations may be used). All plates must be maintained in a legible condition. - (2) Each insulated cargo tank must have additional plates, as described, attached to the jacket in the location specified unless the specification plate is attached to the chassis and has the information required in paragraphs [(b)](#b) and [(c)](#c) of this section. - (3) The information required for both the name and specification plate may be displayed on a single plate. If the information required by this section is displayed on a plate required by the ASME, the information need not be repeated on the name and specification plates. - (4) The specification plate may be attached to the cargo tank motor vehicle chassis rail by brazing, welding, or other suitable means on the left side near the front head, in a place accessible for inspection. If the specification plate is attached to the chassis rail, then the cargo tank serial number assigned by the cargo tank manufacturer must be included on the plate. - (b) **Name plate.** The following information must be marked on the name plate in accordance with this section: - (1) **DOT-specification number MC 331 (DOT MC 331).** - (2) **Original test date (Orig.** Test Date). - (3) **MAWP in psig.** - (4) **Cargo tank design temperature (Design Temp.** Range) ______ °F to ______ °F. - (5) Nominal capacity (Water Cap.), in pounds. - (6) **Maximum design density of lading (Max.** Lading density), in pounds per gallon. - (7) **Material specification number—** shell (Shell matl, yyy***), where “yyy” is replaced by the alloy designation and “***” is replaced by the alloy type. - (8) **Material specification number—** heads (Head matl. yyy***), where “yyy” is replaced by the alloy designation and “***” by the alloy type. - (9) **Minimum Thickness—** shell (Min. Shell-thick), in inches. When minimum shell thicknesses are not the same for different areas, show (top____, side____, bottom____, in inches). - (10) **Minimum thickness—** heads (Min. heads thick.), in inches. - (11) **Manufactured thickness—** shell (Mfd. Shell thick.), top____, side____, bottom____, in inches. (Required when additional thickness is provided for corrosion allowance.) - (12) **Manufactured thickness—** heads (Mfd. Heads thick.), in inches. (Required when additional thickness is provided for corrosion allowance.) - (13) **Exposed surface area, in square feet.** - (c) **Specification plate.** The following information must be marked on the specification plate in accordance with this section: - (1) Cargo tank motor vehicle manufacturer (CTMV mfr.). - (2) **Cargo tank motor vehicle certification date (CTMV cert.** date). - (3) Cargo tank manufacturer (CT mfr.). - (4) Cargo tank date of manufacture (CT date of mfr.), month and year. - (5) **Maximum weight of lading (Max.** Payload), in pounds - (6) **Lining materials (Lining), if applicable.** - (7) **Heating system design pressure (Heating sys.** press.), in psig, if applicable. - (8) **Heating system design temperature (Heating sys.** temp.), in °F, if applicable. - (9) **Cargo tank serial number, assigned by cargo tank manufacturer (CT serial), if applicable.** - (d) The design weight of lading used in determining the loading in §§ [178.337-3(b)](/cfr/49/178.337-3.md?p=b), [178.337-10(b)](/cfr/49/178.337-10.md?p=b) and [(c)](/cfr/49/178.337-10.md?p=c), and [178.337-13(a)](/cfr/49/178.337-13.md?p=a) and [(b)](/cfr/49/178.337-13.md?p=b), must be shown as the maximum weight of lading marking required by [paragraph (c)](#c) of this section. # §178.337-18. Certification. - (a) At or before the time of delivery, the cargo tank motor vehicle manufacturer must supply and the owner must obtain, a cargo tank motor vehicle manufacturer's data report as required by Section VIII of the ASME Code (IBR, see [§ 171.7](/cfr/49/171.7.md) of this subchapter), and a certificate stating that the completed cargo tank motor vehicle conforms in all respects to Specification MC 331 and the ASME Code. The registration numbers of the manufacturer, the Design Certifying Engineer, and the Registered Inspector, as appropriate, must appear on the certificates (see [subpart F](/cfr/49/subpartF.md), [part 107](/cfr/49/part107.md) in subchapter A of this chapter). - (1) For each design type, the certificate must be signed by a responsible official of the manufacturer and a Design Certifying Engineer; and - (2) For each cargo tank motor vehicle, the certificate must be signed by a responsible official of the manufacturer and a Registered Inspector. - (3) When a cargo tank motor vehicle is manufactured in two or more stages, each manufacturer who performs a manufacturing function or portion thereof on the incomplete cargo tank motor vehicle must provide to the succeeding manufacturer, at or before the time of delivery, a certificate that states the function performed by the manufacturer, including any certificates received from previous manufacturers, Registered Inspectors, and Design Certifying Engineers. - (4) **Specification shortages.** When a cargo tank motor vehicle is manufactured in two or more stages, the manufacturer of the cargo tank must attach the name plate and specification plate as required by § [178.337-17(a)](/cfr/49/178.337-17.md?p=a) and [(b)](/cfr/49/178.337-17.md?p=b) without the original date of certification stamped on the specification plate. Prior manufacturers must list the specification requirements that are not completed on the Certificate of Compliance. When the cargo tank motor vehicle is brought into full compliance with the applicable specification, the cargo tank motor vehicle manufacturer must have a Registered Inspector stamp the date of certification on the specification plate and issue a Certificate of Compliance to the owner of the cargo tank motor vehicle. The Certificate of Compliance must list the actions taken to bring the cargo tank motor vehicle into full compliance. In addition, the certificate must include the date of certification and the person (manufacturer, carrier or repair organization) accomplishing compliance. - (5) The certificate must state whether or not it includes certification that all valves, piping, and protective devices conform to the requirements of the specification. If it does not so certify, the installer of any such valve, piping, or device shall supply and the owner shall obtain a certificate asserting complete compliance with these specifications for such devices. The certificate, or certificates, will include sufficient sketches, drawings, and other information to indicate the location, make, model, and size of each valve and the arrangement of all piping associated with the cargo tank. - (6) The certificate must contain a statement indicating whether or not the cargo tank was postweld heat treated for anhydrous ammonia as specified in [§ 178.337-1(f)](/cfr/49/178.337-1.md?p=f). - (b) The owner shall retain the copy of the data report and certificates and related papers in his files throughout his ownership of the cargo tank motor vehicle and for at least one year thereafter; and in the event of change in ownership, retention by the prior owner of nonfading photographically reproduced copies will be deemed to satisfy this requirement. Each motor carrier using the cargo tank motor vehicle, if not the owner thereof, shall obtain a copy of the data report and certificate and retain them in his files during the time he uses the cargo tank motor vehicle and for at least one year thereafter.