jjccr negative pressure test

marco73

marco73

New Member
Hello all

I've tried negative test pressure on my new jjccr (200 min of dive) for all night (12 hours) but does not pass.

The negative test pass only after about 30 mins - 45 mins.

How many time I can consider secure the negative pressure test?


have a nice dive :D

MArco
 
marco73 said:
5 min 10min 30 min is enought?
Click to expand...


5 mins is about 4 mins longer than i usualy do


I became prety relaxed about Neg testing when i baught a KISS. You cant do a neg on those for long without dammaging the ADV

On my old Inspo I could hold a neg overnight no problem at all. i dont know why a JJ cant do this but it cant.

One of the things i beleive is a problem is the spring type clamps on the breathing loop. I dont beleive they provide a seel that will stand up to the presure of a neg test


My units neg teast have improved since i got the Drager connectors for my Golum BOV.

ATB

Mark
 
I usually do somewhere between 3-5 minutes, whenever I forget it and leave it for 15-30 minutes it fails. It doesn't seem to matter much, my unit is always bone dry anyway.
 
On my inspo big leaks will show immediately, you will not get any time on negative.

Smaller leaks do not show for 3 minutes, I do 5-10 mins where I want rock solid for 5 mins and "decent" for 10.

I do not do longer as it is not showing me anything and can cause issues for the ADV diaphragm.

Tiny leaks (shown after 10 mins) do not ingress water IMHO.

I do the same for positive.

Matt.
 
Check the rubber disk in the opv .. Could be facing in a little bit.. They do that every now and then after sucking too much of a negative...my JJ holds a neg or a pos overnight easy... Can sometimes hold a neg for days
 
mine can also get easy hours............ ( DSV .. i do not have a BOV.. )
After i changed the hose connections in tyraps .

I often prepare the unit at home, stick it in the car.
then i drive to dive site and....
Often it is still negative when i arrive on site and get it out the car.
 
Mine was good until it was 2 years old then it started failing pos and neg tests.

Solution was binning the split rings and going for stainless steel tongued cable ties as recommended by NickB. Holds pos and neg tests indefinitely now.
 
marco73 said:
Hello all

I've tried negative test pressure on my new jjccr (200 min of dive) for all night (12 hours) but does not pass.

The negative test pass only after about 30 mins - 45 mins.

How many time I can consider secure the negative pressure test?


have a nice dive :D

MArco
Click to expand...

Negative test is for only about 5 seconds, positve is for a few minutes,

I use to sometimes leave a positive overnight, but not necessary
 
marco73 said:
Hello all

I've tried negative test pressure on my new jjccr (200 min of dive) for all night (12 hours) but does not pass.

The negative test pass only after about 30 mins - 45 mins.

How many time I can consider secure the negative pressure test?


have a nice dive :D

MArco
Click to expand...

With appropriate precision engineering, machining tolerances, O ring selection etc, the negative loop test should last many hours if not days. However 30 - 45 mins sounds fine considering a 5min test is the pre-dive norm. I would therefore not be overly concerned. Indeed many a CCR diver would be delighted if their neg test lasted that long on their particular unit. Rgds Paul
 
I watched a neg test done in less than 30seconds last weekend.
On a Kiss, and it proved a rock solid neg.
The owner connected a digital manometer to the loop via the lp inflate on the wing inflate (just plug in) pulled a neg, watched the reading on the meter, no change, neg test done.
Trouble is digital manometers are ***163;110. But fastest, cleanest most reassuring neg I've ever seen. No watching to see if the loop drops. If the meter doesn't change you've got neg.
Regards
B
 
On the JJ , you look at the ADV button....
It is that simple... if you need a digital tester for that ...:bigdump:
 
barrygoss said:
I watched a neg test done in less than 30seconds last weekend.
B
Click to expand...

Good thing too, much longer than that and the stock ADV starts to get floppy on the KISS (over time)

I always wondered about negative and positive tests, why do people do "long" tests?

As a KISS diver a quick test was required but I would pull the neg (or blow the pos) then let the unit stand for 30seconds, if no noticable change give the hoses, DSV, lungs, scrubber and regs and good prod- still holding then it must be all good right? All done in 60secs flat, it might get left a full 2 minutes some times if I was preoccupied.

What does testing for even 5mins prove? IF the leak is so tiny it takes 5min+ to impact a RB loop will you even notice it? (I'm sure someone will come along with an ancedote of how one did just that to prove me wrong...) So okay 5-10minutes but hours and days? Comeon thats just boasting BS surely, it can't have any benefit can it!

IMO the most important thing is not to leave the unit alone, I've seen alot of people do a pos/neg and very carefully back off and inspect the unit from a few ft away almost as if them breathing close to it will cause a leak- I think you need to give the unit abit of a shake and poke around to see if the unit or its hoses position is hiding a leak.

It seems to me this is another source of diving myth (like scrubber durations and CO2 monitors :chuckle:)
 
I agree with Ben on 5-10 mins. Longer isn't proving much. I'm unconvinced by 30 seconds - not sure that shows much either!

Matt.
 
matthewoutram said:
I'm unconvinced by 30 seconds - not sure that shows much either!
Click to expand...

I'd never say 30secs was enough but... if you have a leak somewhere the most noticable change will be when the loop is most negative or positive, which in the case of a small leak is in the first few seconds.

On CK we have a heavy BOV, when you pull a neg this is lifted up off the deck by the compression of the breathing hoses, if there is any kind of leak the BOV begins to sink down under its weight. IME if it didn't move in the first 30sec-minute it isn't going to, same with positive, if the lungs, hoses etc aren't taught and full after 30secs its rarely going to change.

30secs isn't enough, but it tells you alot.

Lastly I have seen diver battling to resolve incredible small leaks on the DSV and breathing hoses then they jump in and let in far more water via loose lips and generated spit... makes you wonder what their goal was solving the leak :chin:
 
Ben Field said:
I'd never say 30secs was enough but... if you have a leak somewhere the most noticable change will be when the loop is most negative or positive, which in the case of a small leak is in the first few seconds.

On CK we have a heavy BOV, when you pull a neg this is lifted up off the deck by the compression of the breathing hoses, if there is any kind of leak the BOV begins to sink down under its weight. IME if it didn't move in the first 30sec-minute it isn't going to, same with positive, if the lungs, hoses etc aren't taught and full after 30secs its rarely going to change.

30secs isn't enough, but it tells you alot.

Lastly I have seen diver battling to resolve incredible small leaks on the DSV and breathing hoses then they jump in and let in far more water via loose lips and generated spit... makes you wonder what their goal was solving the leak :chin:
Click to expand...

Agreed. Big leak will fail fast, and only a nutter would dive with a big leak.

I've seen units pass 10 mins or more positive and negative with a 1-2" gash in the convoluted hose (it's rubber, it seals).

I've seen someone 80m gas diving the same - few bubbles, about 1/2 cup of water.

Ambient pressure.

Matt.
 
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