Published on 10/12/2003

One of the greatest dangers to divers is being caught in a differential pressure situation - otherwise known at "Delta-P" hazard. For non-divers, that means getting sucked into something like an intake or trapped against a suction intake. Read what CADC member "Maritime Innovation" is doing about it.

With obvious dangerous situations involving divers on their infrastructures, Quebec's electrical power corporation, Hydro-Québec, has made provincial's health and safety situation move a step forward by having Barry, a Montreal company specialized in rescue equipment, designed a totally adapted safety harness. They also put together, with the assistance of the Maritime Institute of Québec, a two days leadership and rescue training involving theoretical and practical sessions. These adapted new tools are now mandatory for whoever performed underwater works on their installations.

The following step they decided to go was to have tests involving aspiration realized. The results would lead to a better understanding of suction situations and would help to write down new procedures for rescuing a diver that would be wedged in a delta P situation.

CADC member, Maritime Innovation as been mandated by Hydro-Québec to proceed with these tests and to validate the efficiency of an alternative rescuing method using injected compressed air.

By designing a suction simulator, Maritime Innovation did several of these tests in different situations and found out that using air injection might decrease suction effect on an imprisoned diver. Results show that aspiration forces could be reduced by as much as 70% when facing a vertical drop water entry situation but the same forces were only reduced by 25% when the same entry was perfectly horizontal. All these tests where made with 8 inches pipes with a water columns of 2 and 10 feet. They also found out that the suction depth was not pertinent at all with regards to suction forces when facing a vertical pipe situation. The outlet depth of this pipe is dictating the delta P involved. It is exactly in this situation that air injection seems to have the greatest influence because of the piston action of the expanded air in the pipe.

Obviously, these results are preliminary and a deeper look has to be given in order to put together a rescue method that would be valuable. With this idea in mind, Hydro-Québec and Maritime Innovation are now putting together a series of tests that could be done in order to determine the best rescue methods when facing suction type situation.

For more information on Maritime Innovation, please follow this link to their website.
www.maritimeinnovation.ca or e-mail Mr. Luc Garand at lgarand@imar.ca