(a)

1. (1) Every container used for anhydrous ammonia shall be provided with one (1) or more safety relief valves of spring-loaded type.
2. (2) The discharge from safety relief valves shall be directed away from the container upward and unobstructed to the open air.
3. (3) The rate of discharge shall be in accordance with the provisions of the flow chart in this subpart, 20 CAR § 880-1113.

(c)

1. (1) Safety relief valves used on containers or systems as outlined in this part shall be constructed to discharge at the rates required in subsection (b) of this section.
2. (2) The design of these valves must ensure such discharge before the pressure exceeds one hundred twenty percent (120%) of the maximum start-to-discharge pressure setting.

(d)

1. (1) Safety relief valves shall be so arranged that the possibility of tampering will be minimized.
2. (2) If the pressure setting adjustment is external, the relief valves shall be provided with approved means for sealing the adjustment.
3. (3) Shutoff valves shall not be installed between the safety relief valves and the container.

(e) Each safety relief valve shall be plainly and permanently marked as follows:

1. (1) With the letters “AA”;
2. (2) The pressure in pounds per square inch gauge (psig) at which the valve is set to start-to-discharge;
3. (3) The rate of discharge of the valve at its full open position in cubic feet per minute of air at sixty degrees Fahrenheit (60° F) and atmospheric pressure; and

4. (4)

   1. (A) The manufacturer’s name and catalog number.
   2. (B) For example, a safety relief valve marked AA-250-4050 (air) would mean that:

(i) This valve is suitable for use on an anhydrous ammonia container;

1. (ii) It is set to start-to-discharge at two hundred fifty pounds per square inch gauge (250 psig); and

   1. (iii) Its rate of discharge at full open position is four thousand fifty cubic feet (4,050 ft³) per minute of air.

(g)

1. (1) A safety relief valve venting to atmosphere at a safe location shall be installed between each pair of shutoff valves in an ammonia line where liquid may be trapped.
2. (2) The start-to-discharge pressure of such relief valves shall not be less than two hundred forty pounds per square inch gauge (240 psig), and not in excess of three hundred pounds per square inch gauge (300 psig).
3. (3) Discharge from safety relief devices shall not terminate in or beneath any building.