Setting of safety valves for liquid ammonia storage tanks
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How many safety valves should be installed on a 100-cubic-meter liquid ammonia storage tank? Which specification has such requirements?
\"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" (SH/T 3007-2014): 6.4.2 The installation of safety valves on pressure tanks shall comply with the following provisions: d) Safety valves on pressure tanks shall be equipped with an online standby safety chamber and one backup safety valve line. One full-bore isolation valve should be installed in front of and one behind the safety valve, and “LO” (seal broken) should be indicated on the design drawings. Therefore, two safety valves and one safety valve bypass line should be provided.
It doesn’t specify how many are needed; as long as the required safety discharge capacity is met, that’s sufficient. Generally, two safety valves are installed, one in use and one as a backup. Ammonia is corrosive and toxic; a ball valve can be installed in front of the safety valve – this valve remains open under normal conditions and is only isolated during maintenance.