Familiarization with equipment and establishing a regular maintenance routine are habits that ensure a diver's safety. The scuba or air tank is no exception, and each scuba tank should be visually inspected every two years and complete hydrostatic testing every five to ensure the interior and exterior of the tank are sound enough to support pressurized air. The crown markings are imprinted information that enable manufacturers to track each unit in case of problems. When buying a used scuba tank, these crown markings provide information on the quality and care of the tank.
Place the scuba tank on the table and orient it so that the tank valve is pointing to you. Place ankle weights on each side of the scuba tank to secure its position.
Identify three rows of imprinted letters at the top (crown) of the tank, near the tank valve. Write down each row of letters and numbers.
Translate the first row of information using the legend below and reading each line from left to right: Transport mark: "TC" or "CTC" means "Transport Canada" Tank material: "3AL" means the tank is aluminum Working pressure in bar (e.g., M207) Tare weight in kilograms (e.g., T11.3KG)
Translate the markings in the middle row: "DOT" specifies US Department of Transportation Tank material code (e.g., "3AL" is the code in the US) Working pressure in PSI (e.g., 3000) Tank model (e.g., S80) Manufacturer name or code (e.g., LUXFER or M4002) Tank serial number assigned (e.g., U123456)
Translate the markings on the bottom line: Month and year of hydrostatic test, each expressed in two digits and separated by an inspection code (e.g., 01A00 for January 2000 independently inspected) Carbon dioxide capacity (e.g., 20#CO2) Tare weight in pounds (TW24.9)
Check whether additional markings are included such as: Overfill is indicated with a "+" sign which enables some steel tanks to be filled 10% greater than the pressure indicated on the tank (see Step 3 or Step 4) Test pressure in PSI (e.g., TP4500 which is greater than the working pressure)
- Note the hydrostatic date (in Step 5) and see whether the date is within the last five years. If the date of hydrostatic testing is more than five years ago, the tank needs to undergo hydrostatic testing before use.