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Who looks out for you when you have diving equipment problems? Diver does. In our quarterly series, John Bantin fields your queries about gear, and calls on the suppliers for help where appropriate. If you have a problem with kit, let him know.
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A free-flow can occur when your regulator is set up to breathe too lightly |
I just had my regulator serviced and now it free-flows. Friends tell me that this can almost be considered normal, as the same thing has happened to them. Why can't service technicians get it right?
When a regulator goes in for a service, many or all of the parts that tend to wear are replaced. However, this is done in a workshop, and your regulator is not taken diving as part of the service.
During the stresses and strains of your first few immersions after the service, rubber O-rings (and there are many) need to bed in. That's why you might find that your regulator is set up to breathe too lightly and starts to free-flow.
Some technicians try not to adjust spring tensions so subtly, and although the regulator may not perform as sensitively to inhalations because it has a higher valve cracking-pressure than before, at least it doesn't gush air.
When your regulator has been serviced, take it on a few shallow dives and be prepared to take it back for tweaking by the service technician. I suggest that you try to avoid taking it away on a diving holiday without doing this first.
After a dive on the Scylla out of Plymouth, I became separated from my buddy. I was picked up by the boat to find that he had exited the water after a fast ascent and was not looking good. We asked the skipper for his oxygen set but were told he did not carry any and that it was not a legal requirement to do so. My buddy was later transported to DDRC by ambulance. Since this incident, I have tried to buy a small oxygen therapy kit. Can you help me find a supplier?
Phil Packer
I would certainly check when booking a boat whether it carries suitable emergency equipment for divers. This includes a marine-VHF radio, a basic first-aid kit and an emergency oxygen supply.
It is not a legal requirement that a vessel carrying people intent on recreational diving should carry such oxygen equipment, though things are different in a teaching scenario, because HSE Diving at Work regulations 1997 specify that a suitable therapeutic kit should be carried, and it is the diving contractor or dive school's responsibility to provide it.
Such portable O2 kits are not cheap, but a number of companies supply them. One is Cardiac Services (02890 669000) - see our review on www.divernet.com/equipment/1203divertests.shtml
The other thing you can do is try to have a closed-circuit rebreather diver with you as often as possible, because the unit can be used as an O2 therapy unit in an emergency, depending on the amount of oxygen remaining in the cylinder (assuming it's been dived) and by selecting a set-point of 1.0 bar for ppO2.
Can you tell me where I can get the sort of miniature air-cylinder James Bond uses? It's for my boyfriend to use while cleaning the underside of his boat.
Lucy Fordair
We checked with MI6, and it denies employing anyone by the name of James Bond, M, Miss Moneypenny or Q for that matter. We conclude that the whole JB story was nothing more than a cruel and elaborate joke played on us by the producers of a movie!
DIVER's own JB suggests that your boyfriend will find that cleaning a hull takes longer than he thought, and that a Mini-B compact scuba set-up might be suitable. The bonus is that you can actually buy one!
It's a British invention aimed at those who don't want or need to go very deep. The manufacturer also can direct you towards a suitable quick and easy-to-learn course. Take a look at: www.divernet.com/equipment/0501divertests.htm
The base of a steel cylinder is rounded - but why? |
Why do steel cylinders have round bottoms but aluminium cylinders have flat ones?
Lee Graham
Aluminium is far less strong than steel, so the walls of the cylinder are more than twice as thick. However it is also a lot lighter, allowing the manufacturer to include extra metal in the base to provide the convenient flat bottom.
If steel cylinders had enough material to have a flat bottom, they would be punitively heavy.
Can I use a Scubapro second stage on an Apeks regulator first stage?
A regulator first stage reduces the pressure of the gas in the tank to 8-10 bar more than ambient pressure. This is called the inter-stage pressure. The second stage reduces it further, to match exactly the ambient pressure of the water surrounding it. So any second stage will work with any first stage provided that they are set for matched inter-stage pressures.
For example, I use the same second stage as an octopus rig with virtually all the regulators I try for Tests, with a few notable exceptions, such as those from Poseidon.
Problems arise with servicing, because most service centres are set up for a limited number of brands and will not necessarily have the parts or the expertise for cross-brand set-ups.
On top of that, CE marking is limited to the first-stage/second-stage combinations that were CE approved, and these will certainly not have been across different brands.
An anchor bend |
On those occasions when I need to tie a slate to my BC via a lanyard, I make sure to use a bowline for a knot, but it always seems to come undone during the dive and the slate goes missing. Why is this?
J Summers
Bowlines are good bends to use for lines that are always under tension, because they rarely jam.
However, the sort of snatching effects experienced under water by a line you might use to tie a pencil to a slate or a slate to a BC, for example, often loosen such knots.
A more secure bend is an anchor bend. Finish it off with a few half-hitches to the loose end.
In an article entitled The Shape of Diving To Come (October 2003), you mention that liquid breathing has been researched for military applications. Is liquid breathing for leisure diving being researched by anyone?
C Duplessis
James Cameron, director of the movie The Abyss, is reported as saying that his film was based on a science experiment he saw at high school. He is further reported as saying that a man named Frank Felcek, known as the "Human Guinea Pig", had actually breathed a liquid in both lungs. Unfortunately, the saline solution used couldn't hold enough oxygen, and the man nearly died as a result.
Experimenters turned to fluorocarbons instead and have since demonstrated liquid-breathing successfully with rats and monkeys. Unfortunately, it seems that the US Federal Drug Administration would not allow use of these techniques in human experimentation.
We tried to find out how the idea is being used in military applications but were informed that if they told us, they would have to kill us!
I think we're a long way off the time when boat crews simply tip liquids into our lungs before we go diving. I would settle for a clean fill of air every time!
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