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Subchapter 1. Unfired Pressure Vessel Safety Orders
Article 6. Anhydrous Ammonia

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§504. Installation of Tanks on Transportation and Bulk Delivery Vehicles.

(a) Transportation tanks mounted on truck or trailer frames shall be placed on saddles or bolsters with the center of gravity as low as possible. Such saddles, bolsters, and/or other fastenings shall be designed to withstand a loading in any direction equal to the loaded weight of the tank when filled to the maximum permissible level with a factor of safety of at least 8. Transportation tanks of the so-called "frameless-type" shall not be used in anhydrous ammonia service until the design of the tank and tank supports has been submitted to the Division and found acceptable. The installation must also comply with DOT requirements.

All transportation trailers shall be firmly and securely attached to the vehicle drawing them by means of suitable drawbars supplemented by a safety chain (or chains) or safety cables.

Every transportation trailer or semitrailer shall have a reliable system of brakes, and adequate provision shall be made to operate the brakes from the driver's seat.

Every transportation trailer shall be equipped with self-energizing brakes.

Transportation trailers shall be so designed that the towed vehicle will follow substantially in the path of the towing vehicle and will not whip or swerve dangerously from side to side.

Where a fifth wheel is employed, it shall be ruggedly designed, securely fastened to both units, and equipped with a positive locking mechanism which will prevent separation of the two units except by manual release.

(b) Every transportation tank shall be protected by a suitable steel bumper attached to the vehicle chassis or equivalent.

(c) All fittings on transportation tanks not protected by the vehicle frame shall be located in recessed wells or otherwise suitably guarded. Any such guards shall be designed to minimize the possibility of rupturing the tank head or shall in case of vehicular accident. The recessed well, if used, shall be of sufficient size and depth that the top of all fittings will be located below the tank shell or head line. The recessed well for safety relief valves shall be located at the top center of the tank and shall be equipped with an unlocked hinged cover or equivalent.

(d) No anhydrous ammonia piping or valves shall be installed within the cab or driver's compartment of a truck.

(e) All piping and fittings on the bottom of transport and bulk delivery tanks shall be adequately guarded.

(f) All tank trucks and all trucks pulling tank trailers used to transport anhydrous ammonia over 1,200 gallons water capacity shall be equipped with the following minimum safety equipment which shall be properly maintained and readily available for use:

(1) One pair of NH(3) resistant gloves.

(2) Full face mask for ammonia service.

(3) One fire extinguisher conforming to the provisions of Article 157 of the General Industry Safety Orders and having a rating of not less than 20B-C.

(4) A container of not less than 5 gallons of fresh water, so located as to permit immediate application. This container shall have a suitable opening to permit rinsing of eyes.

(g) Each liquid withdrawal opening 2 inches nominal pipe size or larger on transportation tanks and bulk delivery vehicles over 1,200 gallons capacity shall be fitted with a remotely controlled internal shutoff valve of the type listed in Sections 507 (e)(3) through (5). Such tanks over 3,500 gallons capacity shall have 2 remote stations for the valve controls, 1 at each end of the tank and diagonally opposite each other.

One control mechanism at each control station may be used to operated all such remotely controlled valves.

All replacement valves for the above service shall comply with these Orders, if the openings in the tank are adaptable for conversion.

(h) Where excess-flow valves [See Section 507 (e)(2)] are used, all liquid and vapor lines shall be at least full size from the excess-flow valve or equivalent shall be located as close to the point of pipe size reduction or other restriction as is practical, unless the excess-flow valve in the tank is designed to operate at the reduced flow conditions, in which case the excess-flow valve in the tank may suffice.

Where excess flow valves are used on tank trucks having 2 or more tanks with common loading and/or unloading lines, the common liquid or vapor lines shall be fitted with an excess-flow valve in the tank opening (unless the common line has a cross-sectional area equal to or in excess of the combined areas of the individual tank lines or unless the excess flow valves in the tank are designed to operate the tank may suffice). Where additional excess-flow valves are used in common loading and/or unloading lines, the additional excess-flow valve or equivalent shall be located as close to the point of restriction as is practical.

NOTE: A quick-closing manually operated valve may be considered equivalent to an excess-flow valve at the point of pipe size reduction or other restriction providing:

(1) It is equipped with a means for closing the valve manually from a point remote from the transfer hose connection.

(2) The loading and/or unloading line in which it is located is secured to the tank or vehicle framework as required by Section 504 (i).

(3) The quick-closing valve is located on the tank side of the structure used to secure the line or lines to the tank or vehicle frame.

(i) All liquid and vapor lines shall be adequately secured to the vehicle frame or tank. The device used to secure the lines shall be so designed that it will withstand the load imposed by the strongest hose and hose fitting to be used in the transfer operations without breaking, or 2,000 pounds, whichever is greater.

(j) All piping and fittings on transport and bulk delivery tanks shall be adequately guarded. The use of anhydrous ammonia hose between the tank and the transfer hose connection shall be limited to not more than 3 sections of metallic hose not over 24 inches in length in each liquid and vapor line. Such lengths of hose shall be used only where necessary to provide flexibility and shall not have 1 section of hose connected to another section of hose. Each section shall be so installed that it will be protected against mechanical damage and be readily visible for inspection. The manufacturer's identification required in Section 510 (b) shall be retained on each section.

(k) All transportation tanks shall be equipped for spray loading (filling in the vapor space), with an approved vapor return valve of adequate capacity.


1. Amendment of subsections (g), (h) and (j) filed 12-8-72 as procedural and organizational; effective upon filing (Register 72, No. 50).

2. Amendment of subsections (a) and (f) and new subsection (k) filed 3-28-75; effective thirtieth day thereafter (Register 75, No. 13).

3. Repealer and new subsection (f) filed 8-6-76; effective thirtieth day thereafter (Register 76, No. 32).

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