Jeremy Macdonald had an experience with a free-flow regulator while training under ice.
This causes the air in his tank to rush out. The problem with ice diving and running out of air is that you can’t just go straight up; you must return to the hole in the ice.
Jenny is also flooded in this episode, and she almost becomes a hypothermia victim. There are many lessons to be learned here.
Freeflow
In scuba diving, a freeflow occurs when the diving regulator continues to supply air rather than cutting off the supply when the diver stops inhaling, or when air begins to flow out of the diver’s mouth due to a pressure difference over the diaphragm or a bump to the purge button, and continues to flow due to the “venturi effect” of reduced internal pressure caused by high flow velocity of the escaping air. If the freeflow is caused by a “venturi effect”, simply closing the mouthpiece over will immediately stop it.
When backpressure is increased, the freeflow does not always stop. This could be due to very cold water freezing the first or second stage valve open, or to a problem with one of the stages. If the freeflow is caused by freezing, it can only be corrected by closing the cylinder valve and allowing the ice to thaw, which necessitates the use of an alternative air supply while the valve is closed. As long as there is freeflow, the refrigerating effect of the air expanding through the valves will keep the ice frozen, and air will escape until the cylinder valve is closed or the cylinder is empty.
“”It wasn’t as bad as it could have been. It really just sucked to cut the dive short due to the free flow regulator. The real lesson learned was recognizing intermediate pressure creep and the impact on the first state while ice diving. Hint: IP creep turns first stage to a block of ice.“”
Jeremy Macdonald
