1. Special Provisions

49 CFR 172 Special Provisions – B-Codes

These provisions apply only to bulk packagings. Except as otherwise provided in this subchapter, these special provisions do not apply to UN portable tanks or IBCs.
CodeDescription
B1If the material has a flash point at or above 38 °C (100 °F) and below 93 °C (200 °F), then the bulk packaging requirements of §173.241 of this subchapter are applicable. If the material has a flash point of less than 38 °C (100 °F), then the bulk packaging requirements of §173.242 of this subchapter are applicable.Browse B1
B2MC 300, MC 301, MC 302, MC 303, MC 305, and MC 306 and DOT 406 cargo tanks are not authorized.Browse B2
B3MC 300, MC 301, MC 302, MC 303, MC 305, and MC 306 and DOT 406 cargo tanks and DOT 57 portable tanks are not authorized.Browse B3
B4MC 300, MC 301, MC 302, MC 303, MC 305, and MC 306 and DOT 406 cargo tanks are not authorized.Browse B4
B5Only ammonium nitrate solutions with 35 percent or less water that will remain completely in solution under all conditions of transport at a maximum lading temperature of 116 °C (240 °F) are authorized for transport in the following bulk packagings: MC 307, MC 312, DOT 407 and DOT 412 cargo tanks with at least 172 kPa (25 psig) design pressure. The packaging shall be designed for a working temperature of at least 121 °C (250 °F). Only Specifications MC 304, MC 307 or DOT 407 cargo tank motor vehicles are authorized for transportation by vessel.Browse B5
B6Packagings shall be made of steel.Browse B6
B7Safety relief devices are not authorized on multi-unit tank car tanks. Openings for safety relief devices on multi-unit tank car tanks shall be plugged or blank flanged.Browse B7
B8Packagings shall be made of nickel, stainless steel, or steel with nickel, stainless steel, lead or other suitable corrosion resistant metallic lining.Browse B8
B9Bottom outlets are not authorized.Browse B9
B10MC 300, MC 301, MC 302, MC 303, MC 305, and MC 306 and DOT 406 cargo tanks, and DOT 57 portable tanks are not authorized.Browse B10
B11Tank car tanks must have a test pressure of at least 2,068.5 kPa (300 psig). Cargo and portable tanks must have a design pressure of at least 1,207 kPa (175 psig).Browse B11
B13A nonspecification cargo tank motor vehicle authorized in §173.247 of this subchapter must be at least equivalent in design and in construction to a DOT 406 cargo tank or MC 306 cargo tank (if constructed before August 31, 1995), except as follows:
  • a. Packagings equivalent to MC 306 cargo tanks are excepted from the certification, venting, and emergency flow requirements of the MC 306 specification.
  • b. Packagings equivalent to DOT 406 cargo tanks are excepted from §§178.345-7(d)(5), circumferential reinforcements; 178.345-10, pressure relief; 178.345-11, outlets; 178.345-14, marking, and 178.345-15, certification.
  • c. Packagings are excepted from the design stress limits at elevated temperatures, as described in Section VIII of the ASME Code (IBR, see §171.7 of this subchapter). However, the design stress limits may not exceed 25 percent of the stress for 0 temper at the maximum design temperature of the cargo tank, as specified in the Aluminum Association's “Aluminum Standards and Data” (IBR, see §171.7 of this subchapter).
Browse B13
B14Each bulk packaging, except a tank car or a multi-unit-tank car tank, must be insulated with an insulating material so that the overall thermal conductance at 15.5 °C (60 °F) is no more than 1.5333 kilojoules per hour per square meter per degree Celsius (0.075 Btu per hour per square foot per degree Fahrenheit) temperature differential. Insulating materials must not promote corrosion to steel when wet.Browse B14
B15Packagings must be protected with non-metallic linings impervious to the lading or have a suitable corrosion allowance.Browse B15
B16The lading must be completely covered with nitrogen, inert gas or other inert materials.Browse B16
B18Open steel hoppers or bins are authorized.Browse B18
B23Tanks must be made of steel that is rubber lined or unlined. Unlined tanks must be passivated before being placed in service. If unlined tanks are washed out with water, they must be repassivated prior to return to service. Lading in unlined tanks must be inhibited so that the corrosive effect on steel is not greater than that of hydrofluoric acid of 65 percent concentration.Browse B23
B25Packagings must be made from monel or nickel or monel-lined or nickel-lined steel.Browse B25
B26Tanks must be insulated. Insulation must be at least 100 mm (3.9 inches) except that the insulation thickness may be reduced to 51 mm (2 inches) over the exterior heater coils. Interior heating coils are not authorized. The packaging may not be loaded with a material outside of the packaging's design temperature range. In addition, the material also must be covered with an inert gas or the container must be filled with water to the tank's capacity. After unloading, the residual material also must be covered with an inert gas or the container must be filled with water to the tank's capacity.Browse B26
B27Tanks must have a service pressure of 1,034 kPa (150 psig). Tank car tanks must have a test pressure rating of 1,379 kPa (200 psig). Lading must be blanketed at all times with a dry inert gas at a pressure not to exceed 103 kPa (15 psig).Browse B27
B28Packagings must be made of stainless steel.Browse B28
B30MC 312, MC 330, MC 331 and DOT 412 cargo tanks and DOT 51 portable tanks must be made of stainless steel, except that steel other than stainless steel may be used in accordance with the provisions of §173.24b(b) of this subchapter. Thickness of stainless steel for tank shell and heads for cargo tanks and portable tanks must be the greater of 7.62 mm (0.300 inch) or the thickness required for a tank with a design pressure at least equal to 1.5 times the vapor pressure of the lading at 46 °C (115 °F). In addition, MC 312 and DOT 412 cargo tank motor vehicles must:
  • a. Be ASME Code (U) stamped for 100% radiography of all pressure-retaining welds;
  • b. Have accident damage protection which conforms with §178.345-8 of this subchapter;
  • c. Have a MAWP or design pressure of at least 87 psig: and
  • d. Have a bolted manway cover.
Browse B30
B32MC 312, MC 330, MC 331, DOT 412 cargo tanks and DOT 51 portable tanks must be made of stainless steel, except that steel other than stainless steel may be used in accordance with the provisions of §173.24b(b) of this subchapter. Thickness of stainless steel for tank shell and heads for cargo tanks and portable tanks must be the greater of 6.35 mm (0.250 inch) or the thickness required for a tank with a design pressure at least equal to 1.3 times the vapor pressure of the lading at 46 °C (115 °F). In addition, MC 312 and DOT 412 cargo tank motor vehicles must:
  • a. Be ASME Code (U) stamped for 100% radiography of all pressure-retaining welds;
  • b. Have accident damage protection which conforms with §178.345-8 of this subchapter;
  • c. Have a MAWP or design pressure of at least 87 psig; and
  • d. Have a bolted manway cover.
Browse B32
B33MC 300, MC 301, MC 302, MC 303, MC 305, MC 306, and DOT 406 cargo tanks equipped with a 1 psig normal vent used to transport gasoline must conform to Table I of this Special Provision. Based on the volatility class determined by using ASTM D 439 and the Reid vapor pressure (RVP) of the particular gasoline, the maximum lading pressure and maximum ambient temperature permitted during the loading of gasoline may not exceed that listed in Table I.

Table I—Maximum Ambient Temperature—Gasoline

ASTM D439 volatility classMaximum lading and ambient temperature (see note 1)
A131 °F
(RVP<=9.0 psia)
B124 °F
(RVP<=10.0 psia)
C116 °F
(RVP<=11.5 psia)
D107 °F
(RVP<=13.5 psia)
E100 °F
(RVP<=15.0 psia)

Note 1: Based on maximum lading pressure of 1 psig at top of cargo tank.

Browse B33
B35Tank cars containing hydrogen cyanide may be alternatively marked “Hydrocyanic acid, liquefied” if otherwise conforming to marking requirements in subpart D of this part. Tank cars marked “HYDROCYANIC ACID” prior to October 1, 1991 do not need to be remarked.Browse B35