Decompression Chamber-homemade

[Brandon]

I imagine you might have some success with this...

Until the accident.

Then I wouldn't want to be in your shoes.

This just doesn't seem to be the kind of thing to homebrew... safety/liability issues all around that may be very difficult to work around.

-B.

 

[roakey]

I took the post as being serious.

With over 700 posts by the person establishing the thread, I took the post as being serious too. So, given that we're discussing a fiberglass septic tank, I felt my response was appropriate.

Roak

 

[Brandon]

Well... the other problem is that a septic tank isn't a pressure vessel.

I couldn't google a PSI rating for a fiberglass septic tank, but I imagine it isn't much, if it's even computed.... I found some info about the water holding tanks, which are very similar in terms of construction, and the tested pressure was very low, far below what you'd need for a deco chamber.

Think about the application these systems are used for: residential or small commercial water/septic holding tanks. The contents are rarely under much pressure... maybe just a little bit more then your tap water is... max.

All the deco chamber pictures I've seen look like the chamber is made out of steel... and fairly thick steel at that (judging from the viewing portals). Just compare the weights... a normal deco chamber weighs in somewhere around 5500 - 6500 pounds... that 2,000 gallon fiberglass septic tank weighs about 550 pounds. That'd make the wall thickness of your septic tank what.. 1/2" thick? Doubtful you're going to hold much pressure with that, considering the real chambers are made out of several inches of steel...

There's no way... I'd say they're similar in cylinder size only.

Maybe I'm way off... there's plenty of more experienced folks on this board who are better versed in these matters... but this is what common sense and a little bit of reason is telling me.

-B

 

[simbrooks]

Well... the other problem is that a septic tank isn't a pressure vessel.

Lets just say that septic tanks are for use with hydrostatic pressure upto only 15-20 deep, really not meant for pressure.

 

[fdog]

Lawman, just like Roakey, I assumed you were serious by your history.

So, here's were the start: $165 to buy the "bible of chamber construction" .

Best of luck!

All the best, James

 

[rmediver2002]

just some more information for those interested:

Recompressions chambers are low pressure vessels, but since they are used for human occupancy they are signifigantly over engineered for safety.

Chambers are built from steel, aluminium (most common), lexan, and more recently synthetic cloth.

Most systems are designed to operate to 165 FSW (73.425 psi) or 60 FSW (26.7 psi)

This is an example of a portable system we used in the military, it is quite expensive since it was designed to military specification not produced for sale.


http://www.hqmc.usmc.mil/factfile.n...b6bb2f0c31edc4f28525628a004fba06?OpenDocument

This is am example of a cloth / transport chamber, the US Navy has also purchased several of these and already successfully used it to transport a sick fisherman / diver in Hawaii

http://www.nautilussystems.com/chambers/chamber-frame.htm

This shows a typical 220 cubic foot double lock chamber, the most commonly used military and commercial diving chamber. For military and commercial operations the chamber is used as a tool to facilitate surface decompression as well as a device for treating diving injuries.

http://www.ambergriscaye.com/pages/town/hyperbar.html

Here is one of the most extensive types of systems you will find, a saturation diving system. These systems include pressurized bells for transporting the divers under pressure to and from the work site as well as pressurized living quarters.

http://www.nut.no/html/saturation_diving_systems.html

Here is a photo of the ocean test facility at the Navy Experiemental Diving Unit, a floodable chamber allowing equipment to be tested in a controlled environment at simulated water depths at a variety of temperature extremes.

http://www.supsalv.org/nedu/images/Photos/Osf10.jpg

 

[DA Aquamaster]

Your compressor (8 HP) is more than likely only going to provide between 6 and 8 cubic feet a minute so your decent time is going to be very slow and the compressor is going to be running at 100% duty cylcle so the air is going to be extremely hot (this temperature is going to be a big issue with your compressor especially if it is oil free / teflon rings)

Once the chamber is at depth your flow from the compressor is not going to be enough to allow venting of the chamber, this is going to cause a build up of CO2 from the exhaled air from the divers inside. Another more serious issue would be a build up of O2 if you are having the patients breath O2 during the treatment.

Even with only an 8 cu ft per minute compressor, you could still use an airbank to provide the air required to blow the chamber down to the required depth and to ventilate the chamber as needed. With a big enough air bank and enough time between cycles, you could do it with 3.5 cfm compressor.

The pressure vessel itself is the big issue. The 75 psi needed to reach 165 ft. is no big deal with a small pressure vessel, but the stresses involved could pose a real challenge for a 2000 gallon septic tank. The effects of rapid decompression (ie. a near instaneous ascent from 165 ft) if it failed would be a real killer even if it did not explode.

 

[diversteve]

Here's one for sale, I think he's a surplus dealer so you might get a better price:

http://forums.deeperblue.net/showthread.php?t=57170

 

[Robert Phillips]

Come on guys, Lawman is the Troll King, but you all took the bait!

 

[Rick Inman]

Hey, I got a good name for your new chamber:

Darwin Hall!