Most techs know that you shouldn’t fill a recovery tank more than 80% with liquid based. Many know that the WC rating stands for “water capacity” and that you need to adjust for the density of the actual refrigerant rather than just using 80% of WC.
I hope most of you know that the TW marking stands for “Tare Weight” and tells you empty weight of the tank.
But do you know the service pressure your tank is designed for?
Because R-410a is one of the higher pressure refrigerants in common use today most modern recovery tanks are built to handle R-410a pressures. The standard they are built to is called DOT-4BA400 and will be stamped on the tank collar. The DOT (department of transportation) is the governing body in the USA that has the rule making and enforcement authority on tanks, tank handling and tank shipment.
Tanks listed as DOT-4BA400 are designed for a service pressure of 400 PSIG with a test pressure of 800 PSIG. This means that R410a is safe in the tank at a tank temperature of up to 116°F which equates to 400 PSIG for typical use but that the tank is tested not to fail until over 800 PSIG.
If a tank has any physical signs of damage it is to be taken out of service and tanks must be re-certified via hydro-static test and visual inspection forma certified facility every 5-years.