Life Support

[VBra676539@aol.com]

Good Morning All
	Was that Rick or Jon that asked about like support?  Anyway FLI:
	Oxygen was normally kept between 18% and 19% in the boats, depending 
on who did your training.  Perry classes said 21% at the maximum with 
slightly under preferred.  Hyco training called for 18%--period.  You can do 
a pretty good job of approximating this by using a good quality barometer and 
an O2 meter.  Set the barometer marker needle to ambient when you dive (and 
figure on adjusting it after the hull cools a bit) the watch the little 
needle.  You are adding O2 steadily, and consuming it at the same rate, so 
any increase on the barometer is CO2 and temperature/humidity changes.  We 
usually let the barometer come up 2 inches, then ran the scrubber until it 
was down an inch (10 to 15 minutes per hour).
	Your average Psubber consumes approximately .85 scfm of O2 while 
sitting and doing light work.  If you add this to your atmosphere (flow 
metered) and keep an eye on your O2 meter, then all will be well.  The same 
psubber will also generate approximately .73 scf per man per hour of CO2 
(and, if you must know, about 550 BTUs of heat).  For two people, I usually 
ran our big scrubber for about 10-15 minutes per hour to bring the barometer 
down.
	Hyco had more flammables in the boat, and used PVC insulated wire, 
but had fewer arcing sources inside (motors, etc.).  Perry boats were much 
more electric internally.  Main motor, hydraulics, solenoids and all the rest 
were inside, where Hyco thrusters and hydraulic packages were extenal.  The 
two manufacturers had different approaches for similar  problems.  Perry, 
with few exceptions, was dealing with pressure hulls designed to operate at a 
<500 psi and this made things relatively simple.  It was easy for us to run 
stuff through the hulls and have all our gear right at hand for maintenance 
and upkeep.  Hyco, on the other hand, designed deep, often >3000 psi external 
operating pressures and had compensated, externally mounted power systems.  
This makes a whale of a difference in the engineer's approach to sub design.
	Of course, George Kittredge said something entirely different.  He 
figured a standard 1-man K350 had about 1 &1/2 hrs air inside, and trained 
all his purchasers and plans buyers to do 1 hour dives and surface to 
ventilate the interior then dive again.  Simple and direct, although it 
doesn't take into account the possibility of being hung up in a fishing net 
at 300 plus feet and needing an extra hour to get loose.  His personal K350 
(which he sold last year, I think) and his K600 both have O2 systems and CO2 
scrubbers.
	Fire fighting:  I agree about the squirt of water being just what the 
doctor ordered in some circumstances.  One instance in particular, a paper 
wrapped bayonet filter from the main thruster of the PC-8 (I was on the 
bottom in 600 feet of water in a Norwegian fjord at the time) kept right on 
smoking until I dropped it into my coffee cup.  Lessons?  Don't use paper 
wrapped filters and don't forget the coffee.  Fire extinguishers, as you 
surmise, are very hard on your life support control features.  And make a 
mess?  Oh, my!  I have never used one in extremis, but we have discharged 
them as an object lesson (after they go out of date).  It is instructive to 
actually put out a fire with one, even in the open air.  And NEVER use an 
inert gas extinguisher in a psub without some form of SCBA or BIBBS system!  
OSHA describes those as IDLH atmospheres.  Immediately Dangerous to Life or 
Health.  Read that last sentence carefully.  OSHA reg 0041 is relevant and 
will prove informative to anyone interested in pursuing this further.
Vance