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March 2000 Vol. 26, No. 3   RSS Feed for Undercurrent Issues
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What's DOT Going to Do?

from the March, 2000 issue of Undercurrent   Subscribe Now

All the controversy on tank explosions has caught the attention of the Department of Transportation (, which is considering taking restrictions even further, as government agencies are wont to do. They’re currently reviewing a slew of proposed revisions to the Hazardous Materials Regulations, including:

Utilizing shear wave ultrasonic testing either in place of hydro tests or as an added option to supplement them. Supposedly, ultrasound will detect subsurface faults, but the testing equipment is not yet available. And, as Bill High points out, ultrasound doesn’t detect some problems that hydro-testing does, such as the impact of continual overpressurization and the tendency of aluminum to soften under high heat.

Marking tanks in metric units to bring the U.S. in line with international standards.

Marking tanks with the test pressure instead of the service-pressure markings with which newly manufactured tanks are currently marked. This is a proposal that worries Bill High. He’s concerned that printing a higher number on tanks will merely encourage overfilling, leading to even more explosions.

Allowing a 10-year interval for requalifying new aluminum and steel scuba cylinders (those that would be marked in metric units under the previous proposal). Currently, U.S. tanks must be hydro-tested every five years. Folks in the U.S. dive industry, some of whom are now calling for annual hydros, seem dumbfounded by this proposal.

Discontinuing authorization for filling a cylinder with a specified service life. The term could be as short as 10 years or as long as 20, although it’s worth noting that many aluminum tanks made as far back as 1971 are still in service and have caused no problems.

Registering hydro and ultrasound inspectors. Beefing up registration requirements would give DOT more clout in the training, control, and enforcement of inspection standards. Bill High, whose company has trained over 10,000 cylinder inspectors, concedes that although the scuba industry has developed its own inspection standards, there is currently no legal requirement that inspectors must be trained or follow industry protocols. As an example, visual inspections must be performed before each hydro test. PSI recommends that another visual be done after the hydro to be sure all water has been removed and no damage has occurred during testing. But there is no way of ensuring whether this procedure is being followed by each inspector.

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