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Ronald

This is only a hedge against common failure mode if you are not really aware of
what triggers the failures.  Generally you should be selecting equipment that
has the lowest probability of failure under the given conditions.  If you
select a backup with a higher failure probability, your overall chance of
failure increases, and your chance of total failure also increases.  In the
particular case you mention, I would suggest that the HP tanks, and D400 2nd
stages are inappropriate choices if reliability is truly of concern.

Cheers
David Pearson


In message "common failure mode and redundancy", srodekoh@ma*.co*.mi*.ed*
writes:

> Chuck and other List participants:
> 
> "Common failure mode", as applied to scuba equipment, is an issue that
> concerns me greatly.  I've often wondered whether, for example, a tech
> diver ought to utilize different (albeit both superior) regulators on
> his/her manifolded doubles--say, a Scubapro Mk 20/G250 on one post and a
> Poseidon Odin on the other, since they appear to have distinct failure
> modes--as a hedge against the common failure mode of "redundant"
> regulators.
> 
> As a second example, should a tech diver carry backup lights that are
> both identical?
> 
> All replies shoud be addressed to the List.  Thanks in advance for your
> input.
> 
> Ronald
> 
> P.S.  For the record, in my five years of extended range diving in the
> Great Lakes, I have personal knowledge of only one occasion when both of a
> diver's regulators failed.  Both of the diver's regulators were Poseidon
> Odin first stages with Scubapro D400 second stages.  The diver was using
> air in his manifolded HP 100's.  Water temperature was near 40 F.
> Depth was approximately 200 ffw.  The diver switched to his backup second
> stage reg when his primary began free-flowing.  The backup began
> free-flowing almost immediately.  Common failure mode?
> 
> P.P.S.  My apologies if this topic has been discussed before;  I've been
> observing the List for only one year.  And I was unable to find any
> reference to this topic in the Archives.
> 
> Sherie Rodekohr				Columbia Career Center
> Vocational Horticulture			4203 S. Providence Rd.
> Voice:  (314)886-2610			Columbia, MO 65203
> FAX:  (314)886-2904			
> Internet:  srodekoh@ma*.co*.mi*.ed*
> x
> 
> 
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