BCD pressure test

[Rich Keller]

Someone told me about a way to test how well a BCD holds pressure that I never heard of before. He uses a reg with two BCD hoses, one attached to the BCD and the other with an intermediate pressure gage attached. He fills the BCD then drains the air from the reg, then he opens the inlet to the BCD allowing the pressure from the BCD back into the reg and reads the IP gage. Once he has that reading he repeats but waits a half hour before allowing the pressure from the BCD back into the reg for a second reading. The first problem that came to mind was there is no way to gage how much pressure was in the BCD to begin each test. Has anyone ever tried this?

 

[Couv]

Rich, if I understand this setup correctly, you are basically using the IP gauge to check-then recheck the pressure in the BC bladder. The first problem I see is that the pressure a BC will contain before the pressure relief valve gives way (or worse the bladder develops a leak) would be so low it would hardly register on a pressure gauge. The second problem is that the inflator button would have to be depressed to get pressure from the bc to the gauge. Finally, the regulator itself along with the hoses will act as an accumulator and skew the leak/pressure test. If you're going to use a pressure gauge to measure the leakage, why not modify a tee fitting so that one leg could have a quick disconnect to pressurize the BC-then disconnect it. The second leg would of course be attached to the BC; and the third would have the gauge.

Now having said that God awful mouthful, what is wrong with filling the BC, disconnect it from the regulator and simply see how well it holds air? Soapy water painted over the entire BC will quickly show any leaks of significance.

 

[Rich Keller]

So with a modified tee fitting the IP gage would then directly read the pressure in the BCD. That sounds like a much better way to do this. Any idea if the pressure a BCD could normally hold would be enough to register on an IP gage? Have you ever tried that? If so what do you think would be an acceptable pressure loss rate over a half hour?

 

[steveharriss]

I prefer couv's second approach. Why over complicate a simple process? Blow the thing up and go back in an hour. If it's still inflated then it's doing it's job.

 

[dumpsterDiver]

You guys serious? The pressure in a BC is maybe what 2-3 psi max? Who the hell cares. blow it up till the valve bleeds, throw it a corner for 20 minutes, if it is still hard it has no meaningful leaks. You really have over 5,000 dives?

 

[pasley]

Someone told me about a way to test how well a BCD holds pressure that I never heard of before. He uses a reg with two BCD hoses, one attached to the BCD and the other with an intermediate pressure gage attached. He fills the BCD then drains the air from the reg, then he opens the inlet to the BCD allowing the pressure from the BCD back into the reg and reads the IP gage. Once he has that reading he repeats but waits a half hour before allowing the pressure from the BCD back into the reg for a second reading. The first problem that came to mind was there is no way to gage how much pressure was in the BCD to begin each test. Has anyone ever tried this?

The correct name for this pressure testing meathod is Rube Goldberg Device. A very complicated device to do a simple task. Inflate BCD till the overpressure pops. Wait overnight, if still inflated it is doing its job. What more do you need to know. If it loses a pound of pressure in 30 minutes the guage will not show that anyway and who cares if it loses 1 pound in 30 minutes. If it goes soft in 30 minutes, well the guage may or may not show that but your eyes and hands will.

 

[graham_s]

After a dive when you're cleaning your BCD, fill it with air, hold it underwater in the bath.
If you get bubbles, it's leaking.
Why make life complicated?

 

[Couv]

So with a modified tee fitting the IP gage would then directly read the pressure in the BCD. That sounds like a much better way to do this. Any idea if the pressure a BCD could normally hold would be enough to register on an IP gage? Have you ever tried that? If so what do you think would be an acceptable pressure loss rate over a half hour?

Rich,

I have not attempted to connect a gauge to a BC. In fact, given more thought I realize that my idea for a tee fitting is also flawed as one would still need to depress the inflator button to check the pressure. If the inflator hose was previously disconnected, then air would escape from the inflator fitting.

I know that I can orally blow up my wing to a point where the over pressure valve releases, so the pressure inside the bc is going to be less than 2 psi.

I appreciate that you are attempting to put metrics to this test, but remember the BC's function is to provide buoyancy. So how about tying a weight to the BC that is just under it's lift capacity-just a number say 30 lbs for a 32 lb wing. Put the bc in a pool and see how long it takes to lose 2lbs of lift. That would give an idea of how much real effect the gas loss has on performance.

Again, I applaud your attempt at putting a measure on this. If you find a method, I'd be interested in hearing it.

 

[herman]

Couv, my method for measuring such things is totally opposite....go figure

Attach weights to the BC to slightly over it over it's listed lift- say 40 lbs into a 35 lb bladder, inflate fully then suspend it completely submerged hanging on a digital fish scale. You can see exactly what the lift is by subtracting the reading on the scales to the known weight. For example, if you take the 40 lbs attached to a BC that is listed as a 35 lb lift and the scales read 10 then the actual lift of the BC is 30 , not 35. If so inclined you can actually watch the lift change as (if) the BC leaks air. With all that said, I do like the rest, blow it up until the relief lifts, set it aside and if it's still nice and firm an hour or so later, it's good to go...it is just a BC after all and considering 90% of the time I don't even wear one, I don't see the big deal with a little leak anyway.

That method is also a great way to determine the exact bouyancy of anything...much to my surprize when I tested my twin 38's in it's backpack they were only 2 lbs negative full. Perfect weight, no wonder they dive so well.

 

[jIM STEELE]

Herman is right if you must maybe to check the op valve setting for relief pres. use a 5 psi gauge so it will measure something a ip gauge wouldn't show anything because they are 175 to 300 psi gauges and are not good for showing very low pressures in the 1 to 2 psi range. just push under water to find leaks. very small leaks don't mean much , just exhale and see how much you leak.