Q&A | Relief Valve Discharge Piping

Question: Is it permissible to use galvanized pipe on pressure relief valve discharge piping?

Answer: As a “best practice” we recommend using the same piping materials for the closed circuit refrigeration system as for the relief valve discharge piping. Specifically, IIAR-2 states that piping in the closed circuit portion of the system should be of one of the following grades:

• Carbon steel: ASTM A53 — Grade A or B, Type E or S
• Carbon steel: ASTM A106 — Grade A or B
• Stainless steel: ASTM A312 — Type 304, 304L, 316, or 316L
• Carbon steel (low temperature): ASTM A333 — Grade 1 or 6 [ref.4.1.3.11].

Note: ASTM A120, A53/A-120, A53 — Type F pipe and cast iron or wrought iron pipe shall not be used for ammonia refrigeration service.

However, the latest version of IIAR-2 has a specific exception for relief valve discharge piping that states:

EXCEPTION:
Relief piping is permitted to be galvanized or un-galvanized ASTM A120, A53/A120, or A53- Type F. It is recommended that when these grades of un-galvanized pipe are used, the pipe be clearly identified with paint striping to prevent their use in the closed refrigeration system.

Therefore, IIAR has answered this question very succinctly in making special allowance for galvanized piping to be used on relief valve discharge piping.