DSV Flapper Valve Noise, Humming

R

Raptor^

Member
My flapper valves on the JJ DSV suddenly started making a farting/humming noise when I breath very slowly in it. It has never been like this before, but I noticed it when building the unit the other day doing the stereo check. If I breath harder they open and close as they should, or if I partially close off the loop ends with my hands the sound does not always appear. It is probably a valve that opens/closes/opens/closes quite fast only letting out small amounts of air at the time until the pressure on it is high enough that it will stay open, as this only happens when I breath very lightly.

But the weird thing is that I replaced the valves two months ago, but now if I change back to the old ones the problem is still there. I then took apart the whole DSV, serviced it and cleaned everything - and it is still the same, no matter which ones of the four valves I have available I put in. All the valves looks fine, and the spiders looks fine also. When applying pressure doing the stereo check, they seal perfectly as they should. I usually just rinse the loop with cold water, and never had any chemicals during rinsing as long as the new set of valves has been installed.

I am not keen on diving the unit as it is, and have already cancelled dives due to this. My fear is that it might be leaking air the wrong way around until the sounds stop during a breath. I have tried listening myself via the loop hoses, and other people listening to just the DSV with the loop off, and we cannot tell for sure which side the problem is on. And switching valves every way possible around does not solve it either.

Any ideas as to what is going on?
Maybe I'm just paranoid, but I don't want to take any chances with these valves.
 
Can you tell what side the humming is coming from? If it was from the exhale side I don't think I would worry as much as the inhale side. Am I making sense?


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I agree, and it probably most likely is on the exhaust side. But I am not able to tell for sure so don't want to risk it. I'll get some brand new flappers to install and see if that fixes it.
 
Garth said:
Can you tell what side the humming is coming from? If it was from the exhale side I don't think I would worry as much as the inhale side. Am I making sense?


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Click to expand...

Why would it make a difference?

If you are inhaling and the flapping is happening on the exhale side then that could leak CO2 back into the loop.
If you are exhaling and the flapping is happening on the inhale side then that could push CO2 back into the inhale lung ready to be leaked back into the loop.

Or did I miss something?

Matt.
 
I'm guessing that when you are inhaling slowly the flapper is only partially opening (say by 1mm) and the "spring" qualities of the silicon are making it vibrate between open and contact with the spider. The humming you hear is vibration-contact between the flapper at the spider. When you inhale or exhale forcefully the flapper opens further and any vibration of the flapper edge isn't close enough to the spider to make contact and create the sound.

I don't know why this started now, perhaps it was always there and you didn't notice before? If they seal when you do a leak test (stereo check) I would dive them.
 
Had one that did that on my Inspo Classic. Passed stereo checks so I kept diving it until it stopped passing the stereo checks - and it was only a few dives later. Just as well, the continuous noise was really getting on my tits during the dive anyway.
 
Take the loop off the t pieces. One end against your cheek, other against your ear blow/suck against the mushroom. If it has any significant leak you'll hear it or feel the air on your ear. Swap sides for the other valve. Easiest way to verify good seal on the mushrooms and my first step of a unit build.
 
Captain Starfish said:
Take the loop off the t pieces. One end against your cheek, other against your ear blow/suck against the mushroom. If it has any significant leak you'll hear it or feel the air on your ear. Swap sides for the other valve. Easiest way to verify good seal on the mushrooms and my first step of a unit build.
Click to expand...

I do the same, but use the palm of my hand. Never heard it called stereo check though!
 
nickb said:
I thought everyone called it that
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Never heard it called stereo check. I just thought of it as flapper valve check.

I would not be missing dives if the flapper valve check showed they were working correctly. I get all kinds of noises, usually due to a small amount of water in the DSV just by the flapper, or in the exhale loop. Condensation, saliva, seawater, etc.. Depending on where the water is, different noises.
 
Mine makes some odd noises too. I figured it was the exhale flapper getting slightly stuck to it's seat by bits of gob.
 
Here is a little update on this issue.

I made a recording of the noise to clarify it. In the first half of the recording the Inhale hose to the DSV, where it usually connects to the T-piece, is held close to the microphone. And in the second half the Exhale hose from the DSV, the end where it usually connects to the T-piece, is held close to the microphone.

Take a listen to the sound recording of the problem and let me know what you guys think.
https://www.dropbox.com/s/x0l4bz85gpn4z1v/DSV Problem.mov?dl=0

I sent this to JJ and Jan wanted the DSV in for servicing as he had never heard of anything like it. So I sent the DSV and hoses to the factory. When I got it back, there was no info of what he thought about it, but it had obviously been serviced as there was new O2-grease in the barrel. However the sound is still there after return, but not nearly as pronounced.

I was also able to get it to almost shut up prior to sending it in by trying on different sets of flapper valves, some of which made a horrible noise and some that only made some noise.

I would really like to hear some opinions on this as in the beginning I never heard any sounds like this from the flapper valves, only precise opening and closing sounds.
 
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Sounds like it varies which suggests it may be caused/altered by differences in airflow; ie. changes to the way you breathe changes the sound/valve action. Given that you could almost eliminate the sound by changing flapper valves, it might be that slight variations in the valves also contribute to causing the sound.
 
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I get the same sound when diving my Frankenstein machine. But only when my lung volume is really low. Add a few puffs of dill and see it it gos away.
 
Sounds like it varies which suggests it may be caused/altered by differences in airflow; ie. changes to the way you breathe changes the sound/valve action. Given that you could almost eliminate the sound by changing flapper valves, it might be that slight variations in the valves also contribute to causing the sound.
Click to expand...

Yes, if I did breathe hard it would not make the sound so if the pressure difference was high enough it would open and close firmly. I also think variations in the flappers are the cause, but I would think at least some of them would be 100% and I already tried 4 pairs. I doubt that they are able to allow airflow against the valves allowing for the possibility to rebreathe exhaled gas without it being scrubbed, analyzed and having O2 added, but it's difficult to know for sure and this is my main concern.

Both sides does pass the stereo check and they do seal completely when testing them, its only when breathing normally or carefully in the DSV and listening in the hoses I can hear the sound.

Right now it does not make nearly as much sound, but if I breathe carefully I can still hear it. I'm wondering if this might be normal with a little noise like this, but like I said I never heard a sound like this the first 2 years of owning the unit.
 
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