Ind. Admin. Code tit. 355, r. 3-4-5 – Pressure relief valves; vent pipes

Sec. 5. Every storage container shall be provided with two (2) or more pressure relief valves installed in a manner (see manifold or other arrangement in 355 IAC 3-2-8(e)) which allows one (1) valve of the two (2) or more to be closed while providing the full required capacity flow through the remaining valve or valves. The valves shall be of the spring-loaded or equivalent type and shall comply with the following:

(1) The discharge from pressure relief valves shall be directed away from the container upward and unobstructed to the open air. Vent pipes, if used, shall not be restricted or smaller in size than the relief valve outlet connection. All relief valve discharges shall have suitable rain caps that will allow free discharge of the vapor and prevent the entrance of water. Suitable provision shall be made for draining condensate that may accumulate.
(2) Vent pipes from two (2) or more pressure relief devices located on the same unit, or similar lines from two (2) or more different units, may be run into a common header, provided the cross-sectional area of such header is at least equal to the sum of the cross-sectional area of the individual vent pipes.

(State Chemist of the State of Indiana; Agricultural Ammonia PT A, Sec IV, Rule 4.4; filed Dec 30, 1965, 2:15 p.m.: Rules and Regs. 1966, p. 13; filed Jan 19, 2001, 2:04 p.m.: 24 IR 1636; 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; readopted filed Jul 2, 2019, 10:42 a.m.: 20190731-IR-355190258RFA; readopted filed Nov 4, 2025, 2:37 p.m.: 20251119-IR-355240619RFA)