A visual test or inspection of a diving cylinder is made before a hydrostatic test is made. It is also done half way between the hydrostatic test cycle to verify the condition of the cylinder.
Step 1 – Checking the threads
The first step is to inspect the threads for damage and to gauge them to see if they are in tolerance. This is done with a pair of calibrated gauges called the “GO” and “NO-GO” gauge. Simply the GO should wind on or into the thread and the NO-GO should not. Threads are one of the major causes of cylinders to fail and usually it is due to maintenance by non-trained persons.
Step 2 – Visual Inspection
This is done externally and internally. Externally the boot is removed and the general condition of the cylinder is checked. Defective paint will not fail a cylinder. Deep rust marks and damage are the problem. Internal visual inspection is done by using a bright light and endoscope. This can even look back a the shoulder of the valve internally. Deep rust marks are the issue. Cylinders may have a light rusting over the inside. This is not a fail.