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Graveyard Diver cylinder hydrostatic test

In the United States, hydrostatic testing on aluminum and steel SCUBA cylinders is normally required every five years.  This test is required by DOT and must be done by a DOT approved and licensed facility.  Reputable dive shops will not fill any cylinder that does not have a valid hydrostatic stamp.  Hydrostatic testing measures the permanent elastic expansion of your cylinder to determine if the cylinder is safe to hold pressure.

If your cylinder is 6351 alloy aluminum, the hydrostatic tester is required by DOT to also do an Eddy Current test on your cylinder a the time of recertification that may detect any sustained load cracking in the neck and thread area that are too small to be easily seen with normal optical devices.  Eddy current testing is normally not done on 6061 aluminum SCUBA cylinders or steel SCUBA cylinders becuase these cylinders are not susceptible to sustained load cracking, and the test is not recommended by the cylinder manufacturers due to the number of excessive false positive results.

Regardless of what your local dive shop may tell you, 6351 alloy cylinders are safe to use according to DOT, and may remain in service IF they pass an Eddy Current Test and Visual Inspection at the time of Hydrostatic requalification.  Although no 6351 cylinders have ever been recalled, and though they are safe and legal to use according to DOT regulations, some dive shops may refuse to fill or visually inspect them under the theory of safety of their employees.

During a Hydrostatic test, also called a "requalification", the technician will first visually inspect your cylinder.  If the cylinder passes his visual inspection, it will then be submerged in a sealed steel tank filled with water, then pressurized will water to it's DOT specified test pressure.  For many SCUBA cylinders, the test pressure is 5,000 PSI.  Once the cylinder is pressurized to it's test pressure, the pressure is held for several minutes.  The technician will then read the level of water shown in several glass tubes to determine how much your cylinder has expanded.  Then, he will release the pressure in your cylinder and read the water level in the glass tubes agaiin to determine if your cylinder returned to it's previous size.  All SCUBA cylinders expand a tiny bit each time they are filled, and the technician will compare the amount of expansion to the manufacturers specifications to make sure your cylinder is within the range of expansion permitted by DOT.  If your cylinder fails a hydrostatic test, it will be condemned and returned to you.  Once a cylinder has been condemned under DOT regulations, it cannot be "repaired" or put back into service.

After your cylinder has passed the hydrostatic test, the inside of the cylinder is dried on a hot air blower and then visually inspected again.  This second visual inspection is done becuase it is possible that pressurizing a 6351 alloy cylinder to 5,000 PSI may open cracks in the threads or neck area that were not previously detectable before it was pressurized to it's test pressure.  Then, the technician will stamp a date and his DOT identification number into the neck of the cylinder.  Once your cylinder comes back from a successful hydrostatic test,  a PSI-PCI trained and certified technician will visually inspect the cylinder again and apply a valid visual inspection decal.

Graveyard Diver cylinder hydrostatic test   Graveyard Diver scuba cylinder hydrostatic test

Graveyard Diver scuba cylinder hydrostatic test   Graveyard Diver scuba cylinder hydrostatic requalification date stamp




Why bring your cylinder to Graveyard Diver when your 5-year hydrostatic requalification is due?

Our turn around time is usually about 2 weeks for a hydrostatic requalification.   We don't let your cylinder sit around the dive shop for weeks trying to accumilate enough cylinders to "make it worth our while" to hydrostatically test them.  At Graveyard Diver, every customer is "worth our while".

We get your cylinder hydrostatic tested, Eddy Current tested (if required by DOT), visually inspected by a PSI trained and certified technician, and returned to you as soon as possible.

Are you planning on diving while your cylinder is out for hydrostatic requalification?  Not a problem.  Many dive shops will be glad to rent you a cylinder while they are hydrostatically testing yours.  But at Graveyard Diver, we offer FREE loaner cylinders for you to use while your cylinder is being tested.  The only other place you can find service like that is in Mayberry!

Graveyard DIver and DOT strongly recommend you consider replacing your cylinder valve burst disk at every 5-year hydrostatic test.  While the outside of the cylinder valve burst disk is visually inspected during a formal visual inspection, burst disks can not be re-used once removed, so there is no practical way to accurately determine if your burst disk is gouged, deformed, or weakened by corrosion without removing it and looking at it. 100 feet below the surface is not the time to find out your burst disk is too weak to hold service pressure.  While cylinder burst disk failure is very rare while actually diving, your life and safety is definately worth the few bucks for a new burst disk.

Simply stated, Graveyard Diver doesn't cut corners on customer safety or customer service.