Oil Pot has to meet Cal/OSHA Safety Orders Title 8, Article 2, Section# 458 rules for ammonia vessels. This includes at least spot x-ray, .1875" minimum material thickness and stress relieving the heads before fabrication. Ours are rated for 350# working pressure at -50 degrees F, by post weld stress relieving the entire vessel. We invite you to consider upgrading the systems you are currently responsible for legal oil pot in future systems.