Test A Hydrostatic Air Bottle

It is important to test all scuba equipment before use.

A hydrostatic bottle is more commonly known as a scuba cylinder or diving cylinder. The cylinders come in different sizes and materials, such as steel, aluminum or composite cylinders. The Department of Transportation requires cylinders to be hydrostatically tested for safety reasons. Furthermore, it is necessary to find out the maximum pressure the tanks can hold. The maximum pressure is usually embedded or stamped near the top of the tank.


Hydrostatic Bottle Testing

1. Ensure the tank is empty. Remove the tank valve. Perform a visual inspection on the tank. Look for any corrosion, dents, rust or other abnormalities on the outside and inside of the tank. Check the threads and the neck of the cylinder for corrosion or cracks. Use an electronic device called Visual Plus to test for cracks in the neck threads on aluminum tanks.

2. Fill the cylinder with water to perform the hydrostatic test. If the tank ruptures, water does not compress like air and would not cause an explosion. Place the valve on the top of the cylinder. Seal the valve with Teflon tape. Lower the cylinder into the test chamber.

3. Check the hose on the back of the test vessel. This hose supplies water to the interior of the cylinder, as well as high pressure to the test chamber. Enclose the cylinder in the test chamber. Apply pressure to the cylinder. Any air that remained in the tank is being released. Increase the pressure on the valves to five-thirds of the pressure stamped on the cylinder. For instance, if the stamp reads “3000 psi,” increase the pressure to 5000 psi.

4. Use a burette to test the water level. Check to make sure the water level does not change for at least 30 seconds. Release the pressure and observe the water level. Make sure the burrette reading returns to at least 10 percent of the original reading. If it does not, the cylinder is not safe to use at high pressures.