Mailing List Archive

Mailing List: techdiver

Message Display

Its interesting that in accordance with the U.S. Navy manual,"System
Certification Procedures and Criteria Manual for Submarine-Oriented 
Deep Submergence Systems," a typical cave diving light cannister
(apx.190 cu.inches excluding battery gel and plates displacement)
would have a minimum standoff distance away from the pressure hull of a 
deep submergence submarine or habitat of about 2.1 ft if used outside 
the pressure hull with a 1 atmosphere compartment, a diameter of about 
4 ft, and a design depth of about 500 ft deep. If located closer than 
the minimum standoff distance (2.1 ft) the implodable volume would be 
considered a Critical Volume which by definition is a volume which may 
affect the safety of the deep submergence system. Now if this can be a 
potential hazard to a steel structure with a design crush depth of 1.5 
times max. operating depth (750 ft in this example), just think about 
the effects on the human body if located 2.1 ft away or closer?

Having conducted a lot of pressure vessel implosion testing, I can 
appreciate the effects of an imploding light housing (e.g. Sheck 
Exley's account in Mexico where I believe just the top pushed in) With 
much respect for Jim Bowden, I still cringe when I see his acrylic 
battery cannister mounted on top of his tanks just behind his head 
(TechDiver magazine).  Most of the acrylic housings I have tested to 
failure end up making the inside of the water-filled test chamber look 
like one of those crystal balls with a Christmas scene you shake to see 
the snow flakes. I still use an acrylic housing mounted on my backplate 
waist belt anyways - risk taker I suppose.  One day I'm going to do a 
structural analysis of the housing. The results may be interesting 
considering all of the non-metallic light housings I have seen have 
some basic design flaws that are well understood in the Ocean 
Engineering community. Prismatic, externally loaded cannisters, not on 
my watch, unless they are pressure compensated, which can be 
accomplished quite easily to depths in excess of 20,000 ft! That is if 
you are willing to pay the price.

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]