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Life Ending Seconds – 3000 to Zero in 72 Seconds – Advanced Diver Magazine – by Curt Bowen

We train for equipment failures in our certification courses, practice our emergency drills, and conduct pre-dive safety inspections. We do all this in hopes that we may catch a problem before it happens or have the knowledge to remedy the situation at depth just in case one occurs. In all the preparation and drills, it always seems that an equipment failure happens at the worst time.

Advanced Diver Magazine looked into equipment failure one step further and conducted a series of tests at multiple depths in an attempt to calculate if increased depth can escalate a potential life threatening equipment failure. Afterwards, we posted the results on the technical diving forum, The Decostop (www.thedecostop.com), to see what the responses and suggestions from other technical divers would be.

The test

Four different equipment failures were simulated at four different preset depths and timed for their results. Each test included a full aluminum 80 cubic foot cylinder filled to 3000 psi. The test timed how long it would take to drain each aluminum 80 from 3000 psi to 0 psi.

The equipment failures tested
1. High-pressure hose failure. Simulated by putting a pre-cut high-pressure hose on a first stage regulator. The cylinder valve was fully opened at the predetermined depths, and the time it took to drain an 80 cubic foot cylinder was recorded.
2. Low-pressure hose failure. Simulated by putting a pre-cut low-pressure hose on a first stage regulator. The cylinder valve was fully opened at the predetermined depths, and the time it took to drain an 80 cubic foot cylinder was recorded.
3. Burst disk failure. Simulated by removing a burst disk from the cylinder valve at depth. The time it took to drain an 80 cubic foot cylinder was recorded.
4. Free-flow second stage regulator. Simulated by manually purging a high performance second stage at the predetermined depths until the cylinder was emptied. The time was recorded.
Depth Tests Conducted

Equipment Failure Test Results

This test (see above results) produced clear and precise results indicating that any major equipment failure, with the exception of a high-pressure hose rupture, would result in a catastrophic gas volume loss in just a few seconds.

Applying this knowledge to real life situations.

The far right column in the chart above provides the amount of gas lost in cubic feet in 15 seconds. (The estimated time it takes for an unsuspected diver to fully analyze and shut down the failed regulator or isolation valve.) Of course with some situations, such as a ruptured burst disk or tank neck o-ring failure, all the volume in the affected cylinder will be lost.

The best reaction and solution to save the maximum amount of gas will vary according to the type of rig each diver is using from doubles with an isolation valve, independent doubles, and side mount cylinders. The ending consensus indicated that a good buddy team, especially for extreme technical diving and proper gear maintenance was of top priority.