What does the marking 3AA on a tank signify?

The marking "3AA" on a tank signifies that the tank is made of steel and meets specific standards for certain pressure ratings. This designation indicates that the tank is constructed from high-strength steel and is designed to withstand higher pressures than typical aluminum tanks. The "3" in the marking refers to the ASTM (American Society for Testing and Materials) specification that the tank meets, while "AA" indicates that it is a certain type of steel grade.

Steel tanks often exhibit higher durability and resistance to damage compared to aluminum tanks, which is relevant for divers who require reliable and resilient equipment. Understanding these markings is critical for ensuring the safety and proper usage of tanks during diving activities.