provisions shall be made for the equivalent of the breakage groove. On cars without continuous center sills, the breakage groove or its equivalent must be no more than 15 inches below the tank shell. On cars with continuous center sills, the breakage groove or its equivalent must be above the bottom of the center sill construction.

(8) The flange on the outlet nozzle or the valve body of exterior valves must be of a thickness which will prevent distortion of the valve seat or valve by any change in contour of the shell resulting from expansion of lading, or other causes, and which will insure that accidental breakage of the outlet nozzle will occur at or below the "V" groove, or its equivalent.

(9) The valve must have no wings or stem projecting below the “V” groove or its equivalent. The valve and seat must be readily accessible or removable for repairs, including grinding.

(10) The valve operating mechanism on interior valves must have means for compensating for variation in the vertical diameter of the tank produced by expansion, weight of the liquid contents, or other causes, and may operate from the interior of the tank, but in the event the rod is carried through the dome, or tank shell, leakage must be prevented by packing in stuffing box or other suitable seals and a cap.

(b) If indicated in § 179.201-1, tank may be equipped with bottom washout of approved construction. If applied, bottom washout shall be in accordance with the following requirements:

(1) The extreme projection of the bottom washout equipment may not be more than that allowed by Appendix E of the AAR Specifications for Tank Cars.

(2) Bottom washout shall be of cast, forged or fabricated metal. If welded to tank, they shall be of good weldable quality in conjunction with metal of tank.

(3) If the washout nozzle extends 6 inches or more from the shell of the tank, a V-shaped breakage groove shall be cut (not cast) in the upper part of the nozzle at a point immediately below the lowest part of the inside closure seat or plug. In no case may the nozzle wall thickness at the root of the "V" be more than 1⁄4 inch.

Where the nozzle is not a single piec provisions shall be made for the equi alent of the breakage groove. Th nozzle must be of a thickness to insur that accidental breakage will occur a or below the “V” groove or its equiv lent. On cars without continuou center sills, the breakage groove or i equivalent may not be more than 1 inches below the outer shell. On ca with continuous center sills, the breal age groove or its equivalent must t above the bottom of the center si construction.

(4) The closure plug and seat mus be readily accessible or removable fo repairs, including grinding.

(5) The closure of the washou nozzle must be equipped with a 4-inc solid screw plug. Plug must be a tached by at least a 1⁄4-inch chain.

(6) Joints between closures and thei seats may be gasketed with suitabl material.

[29 FR 18995, Dec. 29, 1964. Redesignated a 32 FR 5606, Apr. 5, 1967, and amended by Amdt. 179-10, 36 FR 21351, Nov. 6, 1971 Amdt. 179-40, 52 FR 13047, Apr. 20, 1987)

§ 179.200-18 Safety relief devices.

(a) Safety relief valves. (1) When permitted in § 179.201-1, each tank or compartment shall be equipped with one or more safety relief valves of ap proved design, made of metal not subject to rapid deterioration by the lading, and mounted on expansion dome of Class DOT-103 or 104 cars or top of tank shell of Class DOT-111A cars. Total valve discharge capacity shall be sufficient to prevent building up of pressure in the tank to more than 10 psi above start-to-discharge pressure. See AAR Specifications for Tank Cars, Appendix A, for formula for calculating discharge capacity.

(2) The start-to-discharge pressures and vapor tight pressures shall comply with § 179.201-1.

(b) Safety Vents. (1) When permitted in § 179.201-1, a safety vent, having an inside diameter of at least 14 inches and an approved design to prevent interchange with other fixtures may be installed in place of a safety relief valve on tank cars or compartments used for the transportation of corrosive materials, flammable solids, oxi

dizing materials, or poisonous liquids or solids.

(2) The safety vent shall be closed with a frangible disc which:

(i) Is compatible with the lading;

(ii) Is not subject to rapid deterioration by the lading;

(iii) Is designed to rupture at 100 percent of the tank test pressure, and manufactured and marked in accordance with Appendix A of the AAR Specifications for Tank Cars;

(iv) Is provided with a means for holding the frangible disc in place that will prevent distortion or damage to the disc when properly applied.

(3) A cover, with suitable means of preventing misplacement, shall be provided for the safety vent that will direct any discharge of the lading downward.

(4) All tanks equipped with safety vents shall be stenciled "NOT FOR FLAMMABLE LIQUIDS”.

(c) When a safety relief valve is used in combination with a frangible disc on a 100 psi-test pressure tank, the frangible disc must be designed to burst at 75 psi and the safety relief valve must be set for a start-to-discharge pressure of 71 psi. On 60 psitest pressure tanks, the frangible disc must be designed to burst at 45 psi and the safety relief valve must be set for a start-to-discharge pressure of 35 psi. Provision must be made to detect accumulation of pressure between the frangible disc and the safety relief valve. The detection device shall be a needle valve, try-cock, tell-tale indicator or other approved device. The detection device must be closed during transportation. The tolerance on the valve start-to-discharge pressure is ±3 psi. The minimum vapor tight pressure is 80 percent of the valve start-todischarge pressure.

[29 FR 18995, Dec. 29, 1964. Redesignated at 32 FR 5606, Apr. 5, 1967, and amended by Amdt. 179-42, 54 FR 38798, Sept. 20, 1989]

$179.200-19 Reinforcements, when used, and appurtenances not otherwise specified.

(a) All attachments to tank and dome shall be applied by approved means. Rivets if used shall be caulked inside and outside.

(b) Reinforcing pads must be used between external brackets and shells if the attachment welds exceed 6 lineal inches of 1⁄4-inch fillet or equivalent weld per bracket or bracket leg. When reinforcing pads are used, they must not be less than one-fourth inch in thickness, have each corner rounded to a 1 inch minimum radius, and be attached to the tank by continuous fillet welds except for venting provisions. The ultimate shear strength of the bracket to reinforcing pad weld must not exceed 85 percent of the ultimate shear strength of the reinforcing pad to tank weld.

[29 FR 18995, Dec. 29, 1964. Redesignated at 32 FR 5606, Apr. 5, 1967, and amended by Amdt. 179-10, 36 FR 21351, Nov. 6, 1971]

§ 179.200-20 Interior heater systems.
(a) See § 179.12.
(b) [Reserved]

§ 179.200-21 Closures for openings.

(a) All plugs shall be solid, with NPT threads, and shall be of a length which will screw at least 6 threads inside the face of fitting or tank. Plugs, when inserted from the outside of tank heads, shall have the letter "S" at least % inch in size stamped with steel stamp or cast on the outside surface to indicate the plug is solid. (b) [Reserved]

§ 179.200-22 Test of tanks.

(a) Each tank shall be tested by completely filling the tank and dome or nozzles with water, or other liquid having similar viscosity, of a temperature which shall not exceed 100° F. during the test; and applying the pressure prescribed in § 179.201-1. Tank shall hold the prescribed pressure for at least 10 minutes without leakage or evidence of distress. All rivets and closures, except safety relief valves or safety vents, shall be in place when test is made.

(b) Insulated tanks shall be tested before insulation is applied.

(c) Rubber-lined tanks shall be tested before rubber lining is applied.

(d) Caulking of welded joints to stop leaks developed during the foregoing tests is prohibited. Repairs in welded joints shall be made as prescribed in

§ 179.200-25 Stenciling.

(a) The tank, or the jacket if tank is insulated, shall be stenciled in compliance with the requirements of AAR Specifications for Tank Cars, Appendix C.

(b) [Reserved]

§ 179.200-26 Certificate of construction. (a) See § 179.5. (b) [Reserved]

§ 179.200-27 Alternative requirements for tank head puncture resistance systems Class DOT 111 tank cars required to have puncture resistance systems in accordance with § 179.105-5 may, as an alternative, be equipped with a head shield at each end of the car conforming to the requirements of § 179.10023.

(49 U.S.C. 1803, 1804, 1808; 49 CFR 1.53, Appendix A to Part 1)

[Amdt. 179-35, 49 FR 3472, Jan. 27, 1984]

§ 179.201 Individual specification requirements applicable to non-pressure tank car tanks.