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

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§509. Transfer of Liquids.

(a) No anhydrous ammonia shall be vented to the atmosphere during the transfer operation unless the vent is led to a safe point of discharge.

Anhydrous ammonia shall not be storaged in or transferred into a container at a temperature lower than that shown on the nameplate.

Containers shall be charged or used only upon authorization of the owner.

(b) No gas other than anhydrous ammonia vapor shall be used to displace anhydrous ammonia during the transfer operation.

(c) All filling connections and/or permanently installed transfer hoses shall be equipped with a shutoff valve at the discharge end and shall be kept effectively capped when not in use. These caps or plugs may be plastic or metallic, but must be so designed that they will be vented to the atmosphere while at least 3 full threads are engaged.

(d) During the transfer of anhydrous ammonia, at least 1 attendant familiar with the installation shall remain in attendance at the controls necessary to stop the transfer operation. This attendant shall be considered familiar with the installation only after he has been provided with a set of operating instructions for the unloading operation and has been instructed through a minimum of 3 full cycles of operation. During the transfer of anhydrous ammonia into or from a transportation tank, the brakes of the transporting vehicle shall be set and the wheels blocked.

Provisions for unloading tank cars shall conform to the applicable recommendations contained in the DOT regulations. See 560 (e) for Railroad Tank Car Loading and Unloading.

(1) Caution signs shall be so placed on the track or car as to give necessary warning to persons approaching the car from open end or ends of siding and shall be left up until after the car is unloaded and disconnection from discharge connections. Signs shall be of metal or other suitable material, at least 12 by 15 inches in size and bear the words "STOP -- Tank Car Connected" or "STOP -- Men at Work" the word, "STOP", being in letters at least 4 inches high and the other words in letters at least 2 inches high. the letters shall be white on a blue background.

(2) The track of a tank car siding shall be substantially level.

(e) No anhydrous ammonia shall be transferred with the point of delivery less than 10 feet from any residential building, street, public highway, or sidewalk unless the failure to transfer would create a hazard.

(f) All pumps and compressors used for the transfer of anhydrous ammonia shall be suitable for this service and shall be equipped with a pressure-actuated bypass valve and/or other acceptable device to prevent pressure in the transfer equipment of more than 400 psi unless the piping system is specifically designed for higher pressures. In no case shall safety relief valves used for this purpose be set to open at pressures of less than 325 psi or more than 400 psi.

(1) Pumps shall be designed for at least 250 psi working pressure. Positive displacement pumps shall have, installed off the discharged port, a constant differential relief valve discharging into the suction port of the pump through a line of sufficient size to carry the full capacity of the pump at relief valve setting, which setting and installation shall be according to the pump manufacturer's recommendations.

On the discharge side of the pump, before the relief valve line, there shall be installed a pressure gage graduated from 0 to 400 psi.

Plant piping shall contain shutoff valves located as close as practical to pump connections.

(2) Compressors used for transferring or refrigerating ammonia shall be recommended for ammonia service by the manufacturer.

Compressors shall be designed for at least 250 psi working pressure.

Plant piping shall contain shutoff valves located as close as practical to compressor connections.

A relief valve large enough to discharge the full capacity of the compressor shall be connected to the discharge before any shutoff valve.

Compressors shall have pressure gages at suction and discharge graduated to at least one and one-half times the maximum pressure that can be developed.

Adequate means, such as drainable liquid trap, shall be provided on the compressor suction to minimize the entry of liquid into the compressor.

Where necessary to prevent contamination, an oil separator shall be provided on the discharge side of the compressor.

(g) The filling densities for containers that are not refrigerate shall not exceed the following:

Type of Container Percent By Weight Percent By Volume
Uninsulated 56 82
Uninsulated (see 509(h)) 87.5
Insulated 57 83.5

D.O.T. In accordance with D.O.T. Regulations

(h) Uninsulated containers may be charged 87.5 percent by volume provided the temperature of the anhydrous ammonia being charged is determined to be not lower than 30 F. or provided the charging of the container is stopped at the first indication of frost or ice formation on its outside surface and is not resumed until such frost or ice has disappeared.

Any container, including DOT cargo and portable tanks, shipped under DOT jurisdiction shall be filled according to DOT regulation.

(i) Every portable unloading facility shall comply with the following additional requirements:

(1) A set of written instructions shall be posted at the location or supplied to the operating personnel, describing in detail the proper procedures to follow in operating the transfer equipment.

(2) A container of at least 5 gallons of fresh water shall be located at this facility. This container shall have a suitable opening to permit the application of water to flush the eyes. (A suitable deluge-type, fresh-water shower may be installed in lieu of the above if connected to a reliable source of supply.)


(3) The point of delivery from portable transfer facilities shall be in compliance with the requirements for stationary tanks, as listed in Section 501 (c); except that such point of delivery may be less than 50 feet but not less than 25 feet, from a highway or main track of a railroad.

(4) The working area at the portable transfer facility shall be kept clear of debris, and all compressors, pumps, hoses, valves, etc., shall be protected from vehicle impact. Such equipment shall also be suitably locked or otherwise confined when unattended, to prevent the release of ammonia to the atmosphere by unauthorized persons.

(5) The portable unloading facility must be secured at the end of each period of operation; i.e., the point at which it becomes unattended, the end of a workday, etc.

The facility will be considered secured when all ammonia liquid is confined in the pressure vessel and the gas pressure in any hose is less than 25 psi.

(6) All pressure vessels, hoses, piping, fittings, etc., shall be as required elsewhere in these orders for anhydrous ammonia in the liquid state (high pressure).

NOTE: Portable transferring facilities for anhydrous ammonia is defined as any site at which anhydrous ammonia is transferred from one pressure vessel to another in which the compressor and receiving vessel are not permanently installed on concrete in accordance with Safety Section 501.

(j) Compressors, excepting those on farm vehicles, shall be equipped with manually operated shutoff valves on both suction and discharge connections. Pressure gages of bourdon-tube type shall be installed on the suction and discharge of the compressor before the shutoff valves. The compressor shall not be operated if either pressure gage is removed or is inoperative. A spring-loaded safety-relief valve capable of discharging to atmosphere the full flow of gas from the compressor discharge and the discharge shutoff valve.

(k) Valve functions shall be clearly and legibly identified by metal tags or nameplates permanently affixed to each valve.


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

2. Amendment filed 3-28-75; effective thirtieth day thereafter (Register 75, No. 13).

3. Amendment of subsection (d) filed 5-6-77; effective thirtieth day thereafter (Register 77, No. 19).

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