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From: J Shepherd <jms@ta*.ed*.ac*.uk*>
Subject: Al cylinders Re: FW: inflatable surface marker buoy
To: john thornton <johnpt@jo*.de*.co*.uk*>
Cc: techdiver@terra.net
Date: Sat, 20 Apr 96 10:22:46 BST


	Here's a point;

	Until not so very long ago, all (UK) BCs had a little 0.4l, 200
odd bar cylinder attached. A steel alloy, these things lasted well but
were  bloody heavy, which given most jackets were horsecollar ABLJs, was
a pain in the neck.

	So after many complaints by divers (prats that divers are who
don't know which side their bread is buttered) they swopped the steel
emergency cylinders for Al.

	Oh dear. You see the valves have this little electrolytic
reaction with the body of the tank, and they get fucked. They also
insisted on painting them, which means that salt water gets trapped
under scratches on the bottle and makes corrosive pockets (on a 4mm
thick pressurised container that you wear pointing at your balls).

	Yukky pooh.

	The overall lifespan of these things is about 2 years.

	A coupla questions;
	
	i) Does anyone make steel 0.4l 232bar cylinders anymore?
	ii) Why don't the big Al tanks go the same way - different
valve/tank materials, a larger size as an electron sink?
	
	Personally, I'd suggest keeping life simple and not bothering
with auto-inflating SMBs, heck even the non-return valves on these
things are widget too far IMO.

	Jason

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