Inhale Test After Rebuild

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Discussion of diving methods and equipment available prior to the development of BCDs beyond the horse collar. This forum is dedicated to the pre-1970 diving.
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Location: Columbus, OH

Inhale Test After Rebuild

Wed Oct 19, 2016 1:01 am

Didn't know how to search for this because I'm not really sure what it is called, but when I get finished rebuilding a DH, I always put the mouthpiece in my mouth (with inlet filter covered) and inhale to breath in all the air in the hose and body and make sure the diaphragm collapses and stays that way when I stop inhaling to make sure I don't have a noticeable leak. I do this out of water. The one I just finished, I can keep inhaling. I took the hose off and inhaled through the horn and it worked like it was supposed to. I never do this connected to an air source in case you all just gasped. So my thoughts are my hose has a hole or the clamps aren't tight enough. Or maybe I have some slight imperfections in the horn that the hose wont properly seal around or maybe this is normal and don't worry about it.

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Re: Inhale Test After Rebuild

Wed Oct 19, 2016 5:24 am

I call that a vacuum test or a water tight test, and it should hold a vacuum without leaking. If the leak is so small that you barely notice it, maybe you can tolerate it, but it may breath a bit wet.

Take a look at this link, in particular step 4.

Buceador con escafandra autónoma clásica.

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Greg Barlow
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Re: Inhale Test After Rebuild

Wed Oct 19, 2016 2:57 pm

I use a positive pressure test if I detect a leak. I place the intake horn in my mouth, and create enough positive pressure to cause the diaphragm to rise approximately 1/2-3/8". I hold the cans at an angle where I can see the diaphragm rise. If there is a significant leak, I can typically hear the escaping air.

At times, I have even placed the cans into water, and watched for escaping bubbles. Not a perfect test, but it generally will indicate the origin of the leak if the reg has water intrusion.

Greg Barlow
PADI Assistant Instructor
TDI Decompression Procedures
IANTD Full Cave
NSS/CDS Full Cave

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Master Diver
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Location: Benzonia, Michigan

Re: Inhale Test After Rebuild

Sun Nov 13, 2016 5:50 pm

Earlier this summer I acquired a Voit Sportsman VR-1 (green label) and after I got it completely restored I found out that I had a similar problem. During the restoration I also installed a pair of new green hoses and mouthpiece that I got from Rob so I was certain that the problem was not in that area. I had a reg that was breathing wet and after checking everything over several times I finally discovered the problem. I tried Greg's method by sealing off the air inlet and then submerging the reg with the hoses off in a bowl of water. While the reg was submerged with the inhalation horn out of the water I was able to blow into the outlet creating air pressure inside the dry chamber and sure enough I soon saw some bubbles emerge from an area where the cans and LP diaphragm are held together with a band clamp. As it turned out the problem was the diaphragm. It was a single stage diaphragm and looked just fine with plenty of flexibility, and I believe that it might have been the original one for this reg. Upon very close examination it was soon discovered that there was a very slightly damaged area on the lip area of the diaphragm that is sandwiched in between the top and bottom cans. The reg at some point years ago may have been opened up and when put back together it appears that the diaphragm may not have been properly installed. The lip had an area where it had a very slight flat spot on it as if it had been slightly crushed between the 2 cans when it was reassembled. I put in another diaphragm and tested it by holding it together while inhaling and exhaling from the horn. When inhaling she locked right up as it should and when blowing into it no sound of air leaks or bubbles. Hope this info helps any of you having a similar problem. Terry
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