Mailing List Archive Mailing List Archive
>Date: Thu, 20 Aug 1998 09:48:10
>To: Maggie <mmowens@pa*.co*>
>From: Kevin Rottner <Kevin@So*.co*>
>Subject: Re: Stage bottle rigging
>
>
>>Could someone please explain why is it necessary to put an innertube behind
>>the hose clamp?
>
>
>Dear Maggie Owens :
>
>IMHO - In my humble opinion, here's an answer for you.
>
>Dissimilar metals that are in contact with each other in aqueous solutions
create an electro-chemical reaction that accelerates corrosion. Corrosion
can eventually cause compressed gas cylinders to fail. This is bad.
>
>If you mount a hose-clamp on a stage bottle and dive it, you run the risk
of corrosion at the point where the clamp contacts the cylinder wall. This
is especially true in salt-water conditions. The noteworthy consideration
for this type of corrosion is that it it banded corrosion, usually running
the entire circumference of the cylinder. This corrosion is much like the
corrosion caused by cylinder boots that are not removed or properly rinsed
after a dive, assuming the diver dives with the boots. Instead of "ring
around the collar" its "ring around the tank". This can be very bad.
>
>Corrosion and pitting and rustspots and nicks and dings are sometimes
acceptable for a cylinder provided they are not too deep, too wide, too
numerous and not in straight lines or specific patterns and not in the wrong
locations on the cylinder. Each cylinder manufacturer and other groups and
agencies have guidelines for what is acceptable and what is not. The problem
with corrosion from hose clamps is that it is linear and banded and usually
at the weakest part of the cylinder, where the cylinder wall are the
thinnest. ( Shoulders, valve necks and bottoms of cylinders are generally
stonger and some types of corrosion or damage in these areas are acceptable,
whereas they would not be on the sides of the cylinders. ) I follow the
guideline of PSI when inspecting SCUBA and SCBA cylinders. I also do not
fill cylinders that are "out of visual" or fail my cursory visual prior to
filling.
>
>By placing innertube material, or electrical tape, or pipe insulation tape
between the hoseclamp and cylinder, you dramatically reduce the possibility
of this electro-chemical reaction, and the eventual failure of the cylinder
either by the annual visual inspection or dramatic and rapid content loss in
the field ( which is a nice way to say a cylinder goes " boom ". )
>
>The funny thing is that if you were to go on a boat, and check the pressure
on most stage bottles, you would fing that they are filled in excess of the
maximum working pressure that the cylinder was designed for. Also, most
stage cylinder are filled with rather rich gas in some cases, sometimes even
pure 02. These are exactly the cylinders that you want to be in perfect
shape, with NO corrosion what-so-ever. ( Not that I have ever considered
"pumping" an tank ! ;-} )
>
>Hope this answers your question, and I'm sure you will get additional
opinions and comments from others on the TD list.
>
>Kevin
>
>
>
" You'll never miss the water,
until the well runs dry . . .. "
as sung by Bob Marley
[\]
|
|
^^^^^^^^^^^^^^^^^^^^^^
o o
o o
o o
_____ o o
(_/\_) o o o
=( )= oo
Kevin Rottner
--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]