There are several reasons why a shop might legitimately require a new visual exam such as:
A previous exam may have been invalid if the cylinder markings are in some way deficient. This may result if the previous hydro examiner failed to overstamp an old aluminum cylinder that was manufactured under a Special Permit. Until the cylinder is overstamped 3AL, if eligible, it may not be filled. Certain cylinders manufactured under Special Permits are not eligible for overstamping and must be removed from service in the USA.
It may be that none of these apply in this case.
- tank is brought in completely empty
- previous visual inspection has expired (usually 12 months)
- unusual sound such as rattling or sloshing
- foul odor from cylinder gas
- evidence of contamination (rust/oil) on your reg's first stage filter
- cylinder is leaking from neck
- previous exam was invalid
- evidence of exposure to excessive heat or fire
- cylinder or valve has suffered external damage (dent, rust, bulge)
- cylinder is unusually heavy
- previous inspection sticker has been altered or destroyed
A previous exam may have been invalid if the cylinder markings are in some way deficient. This may result if the previous hydro examiner failed to overstamp an old aluminum cylinder that was manufactured under a Special Permit. Until the cylinder is overstamped 3AL, if eligible, it may not be filled. Certain cylinders manufactured under Special Permits are not eligible for overstamping and must be removed from service in the USA.
It may be that none of these apply in this case.