Re: Unmanned test dives, a safty question

[protek@shreve.net]

    No, I was using the chart on page 815.  "Naval Civil Engineering
Laboratory" chart for flat plane windows.  Actually it is the lower end and
not well defined with the curve.  It looked to me like the short-term
critical pressure was around 5-Mega Pascals.  I used a factor to get
pressure in PSI.  Stachiw recommends a factor of, I believe 7 or 8.  This
will take into consideration certain scratches, cycling, temperatures and
other normal abusive conditions.

Gary B




At 10:24 PM 3/1/99 -0800, you wrote:
>Hi Gary,
>
>I take it that you are using the chart on page 284 ?
>I believe the use of a safety factor of 5 is from A.B.S.
>Thanks for pointing this out.
>
>protek@shreve.net wrote:
>
>>     I just looked up the short term critical loading failure prediction for
>> the window you mentioned and it is right at 725 PSI from the chart in
>> Stachiw's book.  It recommended you use a factor of 8.  I built my
>> annealing oven with a closed loop of aluminum with a high temp blower
>> purchased from Grainger.  I packed the whole assembly in a plywood (UhOh!)
>> box with a lot of fiberglass insulation backed around it.  I have a
>> resistive heater in the channel with a location where I can place the
>> window inside the channel.  The circulating air keeps the temp constant.
>> Stachiw's book has the numbers for annealing.  You need two cycles.  I used
>> a computer to monitor the temps and control the heating.  It took a full 10
>> hours to run one window.
>>
>> Gary B.
>>
>> At 09:05 PM 3/1/99 -0800, you wrote:
>> >Hello again Jon,
>> >
>> >Well maybe it wasn't as load as it seemed, you see, this was my first
>> destruction
>> >test and I was exited and not sure what to expect,
>> >it took me by surprise!  It sure did seem load... anyway...
>> >
>> >The "bang" was just the port.
>> >The test chamber is about 3 ft in length and 18 in. dia.. It belongs to my
>> friend
>> >Doug Previtt of Delta Oceanographics.
>> >I feel very lucky to have access to his facilities, He is a very nice guy.
>>  He
>> >has been building subs (about 7 or 8) for over 35 years.
>> >His sub, the Delta has over 4000 dives all over the world with a perfect
>> safety
>> >record.  He has dove for many government agencies and institutions, and
>> on, and
>> >on, and on...  I think you get the idea.
>> >
>> >When I was a kid my hero was Clint Eastwood.
>> >As an adult... sorry clint, doug has you beat !
>> >He has done in his life what I am just beginning.
>> >
>> >Sorry, back to the subject.
>> >
>> >The view port I was testing was a flat, acrylic disc, 1 in. thick, flat
>> bearing
>> >surface flange, I.D. of 6 in, O.D. of 8. this of coarse gives me a DO/DI
>> ratio of
>> >1.333 which is above the minimum 1.25 acceptable. I needed the port to
>> maintain
>> >to 675 psi to get my safety factor of 5 and it blew at 760 psi which
puts the
>> >depth at 1707 ft.  My operating depth goal is 300 ft. so I'm in the
green !.
>> >Oh yeah, the port I tested was not even annealed, even better because the
>> ports I
>> >use will be.
>> >
>> >Do you know anything about how to make a good port annealing oven ?
>> >ttyl
>> >Alan Long
>> >Subview
>> >Jonathan Shawl wrote:
>> >
>> >> Alan Long wrote:
>> >>
>> >> > Jon,
>> >> >
>> >> > Of coarse the chamber was water filled !
>> >> > What did I say that made you feel I was using air ???
>> >> > >It sounded like a gun shot !!!
>> >>
>> >> I didn't think it would be that loud if it was a small water filled test
>> rig.
>> >> I guess I made an assumption, sorry about that.
>> >> Was the bang just from the cracking or exploding plastic view port?
>> >> How big was the water filled chamber? volume?
>> >> How big was the lens?
>> >
>> >
>
>