Section 355IAC3-2-8. Pressure relief valves

   (a) Every container used with systems embodied in sections 4  through 7 of this rule shall be provided with one (1) or more pressure relief valves of spring-loaded or equivalent type. The discharge from pressure relief valves shall be directed away from the container upward and unobstructed to the open air. The rate of discharge, except as provided in 355 IAC 3-8, shall be in accordance with p 355 IAC 3-8-5(a).

  (b) Container pressure relief valves shall be set to start-to-discharge as follows, with relation to the design pressure of the container:

Containers	Minimum	Maximum*
ASME Code–1950, 1952, 1956, 1959, and 1962 editions	95%	100%
ASME Code–1946 and 1949 editions, Par. U-200 and U-201	95%	100%
API-ASME Code–all editions	95%	100%
ASME Code–1949 and earlier editions, Par. U-68 and U-69	110%	125%
DOT	As established by DOT regulations
*Note: A plus tolerance of 10% is permitted.

  (c) Pressure relief valves used on containers or systems described in sections 4 through 7 of this rule shall be constructed to discharge at the rates required in subsection (a). The design of these valves must ensure such discharge before the pressure exceeds one hundred twenty percent (120%) of the maximum (not including the ten percent (10%) referred to in subsection (b) start-to-discharge pressure setting specified in subsection (b).

  (d) Pressure relief valves shall be so arranged that the possibility of tampering will be minimized. If the pressure setting adjustment is external, the relief valves shall be provided with approved means for sealing the adjustment.

  (e) Shutoff valves shall not be installed between the pressure relief valves and the container, except that a shutoff valve may be used where the arrangement of this valve is such as always to afford full required capacity flow through the relief valves. This exception is made to cover such cases as a three-way valve installed under two (2) pressure relief valves, each of which has the required rate of discharge and is so installed as to allow either of the valves to be closed off at the same time. Another exception to this may be where two (2) separate relief valves are installed with individual shutoff valves. In this case, the two (2) shutoff valve stems shall be mechanically interconnected in a manner that allows full required flow of one (1) relief valve at all times. Still, another exception is a pressure relief valve manifold that allows one (1) valve of two (2), three (3), four (4), or more to be closed off and the remaining valve or valves will provide not less than the rate of discharge shown on the manifold nameplate.

  (f) Pressure relief valves shall have direct communication with the vapor space of the container.

  (g) Each pressure relief valve used with systems described in sections 4 through 7 of this rule and this section shall be plainly and permanently marked as follows:

(1) With the letters AA or NH₃. If not so marked, documentation demonstrating suitability for ammonia service, traceable to the manufacturer, is required.

(2) The pressure in psig at which the valve is set to start-to-discharge.

(3) The rate of discharge of the valve at its full open position in cubic feet per minute of air at sixty (60) degrees Fahrenheit and atmospheric pressure (fourteen and seven-tenths (14.7) psia).

(4) The manufacturer's name and catalog number.

  (h) Connections, such as couplings, flanges, nozzles, and discharge lines for venting, to which relief valves are attached, shall have internal dimensions of sufficient size to avoid any restriction of flow through the relief valves.

  (i) The manufacturer or supplier of a relief valve manifold must publish complete data showing the flow rating through the combined assembly of the manifold with pressure relief valves installed. The manifold flow rating must be determined by testing the manifold with all but one (1) valve discharging. If one (1) or more openings have restrictions not present in the remaining openings, the restricted opening or openings or those having the lowest flow shall be used to establish the flow rate marked on the manifold nameplate. The marking shall be similar to that required in subsection (g) for individual valves.

  (j) A hydrostatic 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. The start-to-discharge pressure of pressure relief valves shall be not less than three hundred fifty (350) psig and not more than four hundred (400) psig for hose assemblies and not more than five hundred (500) psig for piping.

  (k) Discharge from pressure relief devices shall not terminate in or beneath any building. (State Chemist of the State of Indiana; Agricultural Ammonia PT A, Sec II, Rule 2.8; filed Dec 30, 1965, 2:15 p.m.: Rules and Regs. 1966, p. 7; filed Jan 19, 2001, 2:04 p.m.: 24 IR 1631; errata filed Apr 24, 2001, 9:06 a.m.: 24 IR 2709; readopted filed Jun 20, 2001, 3:22 p.m.: 24 IR 3822; readopted filed Apr 27, 2007, 2:03 p.m.: 20070509-IR-355070039RFA; readopted filed Nov 25, 2013, 3:27 p.m.: 20131225-IR-355130482RFA)