welll that's not terrible
welll that's not terrible
Hydro is no substitute for a good visual inspection. Some friends recently proved that when they found three cracks in an AL cylinder that had just come back from hydro (and had passed!) Water will not be pushed through smaller cracks and deficiencies the same way that air will, so a hydro will not find every deficiency. After noting the cracks in that AL cylinder, they got the hydro station to agree to let them test a few sample cylinders to see if this was a true miss or just a rare occurance. Their testing confirmed that a cylinder can pass hydro with neck cracks present. I will see if I can find the pics of that cylinder and post them if you are interested.
It would be neat to see those pics. Makes sense though ... the hydro isn't specifically looking for neck cracks, gouges, rust ... it is just testing the cylinder's ability to expand and bounce back . . .
The hydro test uses water under pressure to measure cylinder expansion. What my friends found out is the water will not pass through some neck cracks as easy as air will. These photos show three neck cracks detected during a VIP on an AL 80 that had just come back from hydro (it passed hydro with flying colors.Originally Posted by seasnake
that's a little scary, but that's why with every hydro you have to get a VIP
There was a pretty good debate circulating about prior to this incident as whether a VIP was needed in conjunction with a hydro. Many argued that the hydro should suffice if the techs looked for dents and dings. Looks like they were wrong. It is interesting to note that the two guys who found this cylinder (and took the photos) like to experiment, ala the myth busters of the scuba industry.
OOOO wheres them pics?
Matt
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