Hydrostatic Pressure Testing A Compressor Air Tank

I have a 60-gallon compressor air tank that I would like to use as an auxiliary tank for my compressor, and possibly eventually build a larger capacity compressor on. The original compressor that was on this tank caught fire. Since there was some heat involved and since the tank has been stored outside I wanted to confirm that the tank is safe to hold the pressure that I intend to use it at, so I did a hydrostatic pressure using a pressure washer as a source to test it to 2x the pressure that I intend to use it for.
These were the parts I used to connect the pressure washer to the tank, surprisingly all found in the outdoors section at the local Lowes hardware:
- M22 male Standard Pressure washer fitting to a 3/8" industrial quick disconnect coupler (female) screwed onto the end of the pressure washer gun.
- Male 3/8" quick connect to 3/8" mpt (male npt)
- 3/8" ball valve (most have female ends on both sides)
- 3/8" mpt close nipple (to change one of the female ends of the ball valve to male)