4" ABS Pipe enough?

undrh2o

I was wondering about the sizing of a homebuild scrubber. The biggest pipe I can get at home depot is 4" ABS. I want to avoid PVC due to it's off gassing if I can. Is this really a problem??

My question is this is a 4" diameter good enough for a scrubber and if so what's the best scrubber length for KISS Classic type duration (4-5 hours)?

Simon A

from my own playing about with home builds I'd have to say that 4" pipe is not going to be big enough, you may get away with it on a pure O2 rebreather but at any depth the Work of breathing is going to be very high.
You may well find it worth while looking through Duncan Price's website ( WWW.sump4.com ) as he's gone through quite a few designs in the evolution of his side mount rebreathers.

Simon A

Genesis

The reading I have done is that the ideal is 2-3:1 in terms of length to diameter. A 4" pipe isn't going to hold enough material to do much, and the WOB if you make it longer to compensate will be quite high.

I'd look at McMaster-Carr - they have various pipe materials available in larger sizes, including acrylic which is easily solvent-welded.

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RebreatherDave

ABS doesn't have a whole lot of strength. ABS stands for acrylic butadiene styrene. Remember though, ABS drain pipe is CELLULAR CORE, meaning it is lightly foamed in the center of its mass, with a denser inner and outer layer.

ABS is readily available in 6". The other problem is ABS does not haveultaviolet stablizers in the material, so it will become a tad brittle with signficiant exposure to sunlight, meaning several years....

I would think PVC would be a more structurally superior choice....I don't think there has been studies though to confirm offgassing of ABS.

Duncan Price

4" is too small. I've used 5" i.d. PVC and this is really too small unless you are using an axial pendulum design. I believe that you need a scrubber with a volume equal or greater than your tidal volume to get the tight dwell time.

PVC no problem unless you are going to use your rebreather to escape from a fire.

undrh2o

Thanks Guys,
Green blob to you all - it looks like I'll look into PVC or acrylic for the scrubber. Anyone have the dimensions for the classic kiss scrubber?

zepp

I have used 4" for a prototype. It did work but reallty you need 6". I do happen to have about 18 feet of 6" ABS and 12 feet of 6" PVC, but I am in the UK.

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spacemanspiff1974

Its frustrating that the most readily available and cheapest pipe isn't really the best idea for rebreathers (PVC). Sigh. Ever try looking for kynar or polypropylene pipe prices online in a 6" diameter. Trust me. Don't even bother.

Acrylic can work quite well. Mcmaster.com has all sizes available. And the stuff should be strong enough. Ever see a 500 gallon acrylic aquarium? Also, due to the knowledge of the aquarium world, we know that acrylic can withstand constant salt, pressure and high intensity lighting. Acrylic cement works well also. It actually fuses the pieces of acrylic together instead of simply sticking to two pieces of material.