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I attempted to post the following discussion this weekend. The new list
filter for registered users was incompatible with my email system. If your
system reports a different address in the "from" listing than your actual
email address you might want to contact the list owner to have the filter
modified.
Why? - Pony Gauges
The previous discussions regarding pony gauges prompt this philosophical
consideration. Why or should you use a pressure gauge on a pony bottle?
As a basis for this discussion I am considering a pony bottle as an
unmanaged gas source. This discussion therefore excludes managed gas
sources such as stage bottles.
As an unmanaged gas source the gas volume is checked prior to the dive and
assumed to be available if needed during the dive. To insure this the
valve is normally (or should be) closed during the dive and opened if the
gas source is needed.
Under this scenario what purpose does a pressure gauge serve?
Points to consider:
1. Failure points of a pressure gauge:
Gauge with hose: 3 o-rings, 1 hose, and the valve.
Gauge without hose: 1 o-ring, and the valve.
Plugged high pressure port: 1 o-ring.
2. Potential for failure is greatest when the regulator is initially
pressurized, e.g.. when you need it, therefore the increased number of
failure points significantly decreases the reliability of the pony bottle.
3. Proper use of a pony bottle as a back-up gas supply would assure that
the diver has sufficient gas supply to safely exit the water from any point
during the dive. In calculating the necessary gas supply divers often
assume their normal gas consumption rate for a non stress situation. In an
emergency situation the diver would execute their mandatory decompression
(if necessary) with no modifications to the schedule. If the gas supply
runs out prior to completion of decompression the diver would then surface
and handle such an situation consistent with previously determined
procedures.
4. Use of a pony bottle is usually associated with an increased stress
situation. Such situations are often coupled with increased respiratory
rates.
5. It has been my experience during situations where divers, particularly
less experienced divers tend to closely monitor their gas supply in such
situations producing increased anxiety and increased respiratory rates.
When the ability to monitor the pressure gauge is removed these divers have
noticeable decrease in respiratory rates. In these situations it is
apparent that the presence of a pressure gauge is adversely affecting the
handling of an emergency situation.
Given these considerations I do not feel that a pressure gauge adds any
benefit to the diver when using a pony bottle.
Curt
Curt W. Smitka Phone: (313) 747-0252
Administrative Manager Fax: (313) 936-8620
Reproductive Sciences Program Email: cwsmitka@um*.ed*
University of Michigan
1109 300 North Ingalls Bldg
Ann Arbor, MI 48109-0404
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