Robert, have you removed a valve knob and seen how large the stem is? 
This is not, IMO, a non-existent problem.  In addition to that,
consider the possibility of tank neck o-ring extrusion... not common,
but it does happen, as has been attested to by several list members. 
The isolator solves both problems.

-Sean


On Tue, 23 Feb 1999 08:10:33 -0500, Robert Wood wrote:

>Sean T. Stevenson wrote:
>> 
>
>> >2.  Isolator valve on manifold:  Si or No ?
>> 
>> The isolator is necessary.  In overhead environments, the possibility
>> exists to break off the right post knob, and if after doing so you have
>> a first stage failure on this post, by closing the isolator you save
>> half your gas (and probably your life).
>> 
>
>At the risk of being a peon in a holy war, Robert Wood adds:
>
>	Are you seriously telling me that you will be crashing
>	around in a wreck or cave with such force and carelessness
>	that you are going to be breaking the tank valve/post/knob?
>
>	If this is the case, then rather than add additional 
>	equipment, and thus failure points, why not either
>	place a small shield by the valve knob (not a cage)
>	or use a different design of valve/post/knob?
>
>	How many incidents of broken valve/post/knob have there
>	been? Are we not trying to solve a non-existant problem?
>
>[\] Robert Wood   
>
>The St. Lawrence river - fresh, warm, visible diving.
>
>mailto:robert_wood@mi*.co*
>--
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