hyperbaric chamber

[WillHartNZ]

Do you know the maximum operating pressure of that chamber. I suspect it is lower than is required for conventional DCS treatment. HBOT (HyperBaric Oxygen Treatment) is mostly in the 20-30' depth range while DCS treatments call for 60-225'.

In any case, operating a chamber that is not certified by a locally recognised agency is a huge liability if it explodes and someone is injured. That puts chambers of all kinds out of reach for DIYers. Don't forget that pressure vessel failures are bombs.

The max pressure while I was in there was 2.8 atmospheres. I wouldn’t have clue about the max pressure it can handle. It’s one of only two chambers available in New Zealand with the other being at navy headquarters.

 

[Searcaigh]

well I'm not advocating doing this but you could try

 

[Akimbo]

the square ones are likely cheaper to manufacture since there is no metal bending involved,

I know that it is not intuitive but square-edge pressure vessels are much more expensive because there is more material cost (weight) and far more linear welds that also requires NDT (Non-Destructive Testing). Rolling services are very inexpensive compared to material, labor, and NDT costs; even with transportation cost from the rolling fabricator. Drawn (pressed) or spin-formed ends are more expensive than rolling but still cheaper than labor and NDT costs.

A double-lock rolled cylinder like a 54" chamber only requires three circumference and two linear welds (besides hatches, penetrators, and viewports). Square or rectangular chambers requires 12 edge welds plus the stiffeners. Stiffeners may not always require full linear welds, but skip welds on both sides of the beams are the minimum.

Cylinders dominate pressure vessel design because of the production cost to volume ratio. That is why you rarely see unpressurized rectangular liquid storage tanks compared to cylinders. The lightest-weight pressure vessels for a given volume are spheres and have the lowest weld length -- except that deep-drawing (pressing) hemispherical ends are usually more expensive than shallower pressed ends.

Most pressure vessel welds have been semi to totally automated since the 1970s so further robotic advancements will probably not change the cost ratios very much. Technology could certainly drive NDT costs down. Material usage is pretty simple physics so innovations in geometry isn't a variable. Material cost per unit of weight applies to any geometry. Carbon nanotube technology would probably shift the cost advantage in favor of spheres.

 

[Kevrumbo]

In general, sharp right hand corners cause local areas of high stress-concentration that provide very detrimental conditions for crack initiation and propagation under fatigue loading. Furthermore, circular cylindrical structures, such as a jetliner fuselage or submarine hull, develop internal membrane stresses (constant through the thickness) to resist the internal pressure loads.

Hospital and University Medical Center Hyperbaric with supporting Emergency Departments which have 6ATA Chamber capability and higher, in close proximity to areas with frequent recreational Scuba activities, and routinely treat the most acute civilian diving casualties 24/7 such as near drowning AGE are all multi-occupant, auxiliary lock entry, and large cylindrical designed permanent in-place structures:

Univ of Hawaii School of Medicine/Kuakini Medical Center, Hyperbaric Treatment Center Oahu:

Univ of Southern Calif/Los Angeles County General Hospital, Catalina Hyperbaric Chamber:
Location > USC Catalina Hyperbaric Chamber > USC Dana and David Dornsife College of Letters, Arts and Sciences

 

[tbone1004]

@Kevrumbo hey, at least one of those still treats divers....

@Akimbo I knew it would be much more material for comparable pressure ratings, but I'm curious if that chamber was only rated for say less than 4ata if there is a breaking point where the cost of those square chambers or logistics if installation maybe is lower than tubes

 

[Kevrumbo]

@Kevrumbo hey, at least one of those still treats divers....

Over 2500 miles away from Los Angeles, this vital civilian facility should never be subjected to closure again:

Mānoa: Hyperbaric Treatment Center reopens | University of Hawaii News

HTC REOPENS WITH DR. SUSAN STEINEMANN APPOINTED AS INTERIM MEDICAL DIRECTOR |

Treatment history research on deep recompression chamber therapy profiles at the Hawaiian HTC:
http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/4054/16457085.pdf?sequence=1

 

[Akimbo]

@Akimbo I knew it would be much more material for comparable pressure ratings, but I'm curious if that chamber was only rated for say less than 4ata if there is a breaking point where the cost of those square chambers or logistics if installation maybe is lower than tubes

I suppose that would depend on the cost of deck/floor space, amortization period, and how you run your accounting. My gut says it is doubtful. Even slight rounding makes a huge difference, but it also depends on which certification agency you design for. Take this illustration as an example:

Let's say that the blue square is the effective working cross-section you need. The center option is the least expensive to produce of the three, but requires more floor space and slightly larger compressors to run it. The right profile could be produced without ribs (which are very costly to fabricate) requires a slightly thicker shell, and has eight linear weld seams compared to one or two on the cylinder. The head (end caps) will also be significantly more expensive to fabricate. You have to run the numbers for the specific pressure rating, material, and code but I suspect that the space savings with a square section would be pretty marginal after you add the shell thickness and ribs required. As an engineer you know that flat surfaces are not your friend when it comes to distributing hydrostatic forces.

Does this incredibly general and non-specific reply help at all?

 

[flyboy08]

For claustrophobic people, the squares the way to go!

 

[tbone1004]

@Akimbo oh I'm with you and wouldn't have thought to design a square chamber, but the chamber that was posted in #6 is definitely just a box and doesn't look like it has any ribs on it. It's also relatively new
Canterbury District Health Board - Hyperbaric Medicine

I wonder if @Duke Dive Medicine has any information on that chamber in terms of pressure or why it is rectangular

 

[Akimbo]

For claustrophobic people, the squares the way to go!

The square is the smallest option of the three. The round is the largest, so probably induces the least confining sensation.

but the chamber that was posted in #6 is definitely just a box and doesn't look like it has any ribs on it.

The vertical members on the outside of the rectangular shell are ribs that they manage to use for shelf space. Ribs are intended to reduce deflection. External pressure vessels such as submarines also use ribs since resisting deflection instead of largely tensile forces is the problem.