Shrimp BOV for JJ

damianb

damianb

Member
Two guys I know have recently (within the past 6 weeks) purchased the shrimp BOV for their JJ's. They have both experienced a fair bit of water ingress in the loop and had to abort dives within minutes of entering the water. The odd thing is that both the units passed pos and neg tests on the surface.. I am looking into getting a BOV but before I commit to the spend, wondered if you guys knew anything about any fitting issues with the shrimp and JJ? As well as the guys I mentioned, I am also a fairly new CCR diver so we could easily be missing something obvious here. :)
 
had this happen to me last week, i am almost sure it has something to do with the mouthpiece, i think that i put the loop on slightly off line causing the mouthpiece to not fit correctly, altered on sat and went down to 66 mtr no problems

alby
 
Alby R said:
had this happen to me last week, i am almost sure it has something to do with the mouthpiece, i think that i put the loop on slightly off line causing the mouthpiece to not fit correctly, altered on sat and went down to 66 mtr no problems

alby
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Ah, interesting. I will tell the guys. Thanks for sharing. I take it you also did not notice anything during pos / neg tests?
 
this began happening to me and my buddy noticed the lever wasn't at its furthest point of rotation.
me being a little more precise when opening and closing fixed the issue
 
As above, I found that the divex mouthpiece off the JJ DSV isn't a good fit and will let water in. I tried an apex comfy-bite mouthpiece next which is a good fit but IMO too soft for the shrimp, in the end I now use a draeger gag strap and haven't had any problems.
 
dunny said:
As above, I found that the divex mouthpiece off the JJ DSV isn't a good fit and will let water in. I tried an apex comfy-bite mouthpiece next which is a good fit but IMO too soft for the shrimp, in the end I now use a draeger gag strap and haven't had any problems.
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I hate the Divex mouthpiece.

The JJ originally came with an Apeks but, at the time, they were prone to split. For a few years I used the Poseidon which is very good but have now switched to the Drager with retaining strap and that is brilliant
 
whats important when fitting aftermarket bov's is that the actual mouthbite opening is the same size as the JJ dsv. the rubber mouthpiece was chosen because of its orifice size and the thickness of the bites. If you put something on smaller it will alter the wob, give possible rise to co2 retention issues. We spent many thousands of pounds in testing getting the wob right and you can easily screw it up by fitting components that dont match. if you dont like the hard rubber mouth bite try an inspiration silicone one, the dimensions are the same.

Oh I should add there are other reasons why an aftermarket bov may not be compatible, bore size, flapper valve size and material, dead space, gas flow, etc. etc.
 
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I've been suffering water ingress into my Shrimp that becomes noticeable after about 30 mins. The unit passed both pos & neg tests on all occasions. I came across a couple of possible suggestions that I've implemented but not been able to validate yet. I added a bit of self amalgamating tape under the mouthpiece & tightened the cable tie up a bit more that previously. Also reseated the two plastic cir-clips inside of the flappers on the BOV. I'll report back when I've dived the unit on whether I've been successful or not.
 
hamishmorrison said:
I've been suffering water ingress into my Shrimp that becomes noticeable after about 30 mins. The unit passed both pos & neg tests on all occasions. I came across a couple of possible suggestions that I've implemented but not been able to validate yet. I added a bit of self amalgamating tape under the mouthpiece & tightened the cable tie up a bit more that previously. Also reseated the two plastic cir-clips inside of the flappers on the BOV. I'll report back when I've dived the unit on whether I've been successful or not.
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Thanks. Pls let us know if you have any joy with that.
 
Just a thought - how are the JJ BOV's? I presume they will fit like a dream with no leaks? Can you still get them?
 
damianb said:
Just a thought - how are the JJ BOV's? I presume they will fit like a dream with no leaks? Can you still get them?
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JJ ceased production of the BOV when they started issuing the CE compliant unit. It's my bet that they will eventually produce another, superior model but CE compliance will be the hurdle here.

The old BOV, as issued from the factory, had a woeful OC performance, although I had a mod that improved it by at least 15% when I tested it on a magnahelic gauge. Quite a few people added this to their own devices.

Your Shrimp is unlikely to be leaking if it holds a pos/neg. The problem will almost certainly be loose lips or an damaged/ill-fitting mouthpiece, which sort of equates to the same thing. My old unit had a BOV and I always got water in the loop. I've mostly solved that now by adding a Drager retaining strap.
 
ccrdave said:
whats important when fitting aftermarket bov's is that the actual mouthbite opening is the same size as the JJ dsv. the rubber mouthpiece was chosen because of its orifice size and the thickness of the bites.
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I thought that about the bites on the Draeger retaining strap, the seemed to a lot thinner than the original JJ one. Back to the question the leak is from the mouthpiece, I have flooded my unit that way.
 
mick4707 said:
I thought that about the bites on the Draeger retaining strap, the seemed to a lot thinner than the original JJ one.
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Quite the opposite. When the Drager mouthpiece is installed the opening is bigger than that on the Divex.

Not the it makes any difference as the Divex pretty much exactly matches the orifice on the DSV or JJ BOV anyway. Can't speak for any third-party BOVs though.

EDIT: Ah you're talking about the bite pieces. Not a problem though as one does't need to bite-down to keep the mouthpiece in. It makes breathing a lot more relaxed. You can actually open your mouth quite wide without letting water in if the strap's tight enough.
 
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mick4707 said:
I thought that about the bites on the Draeger retaining strap, the seemed to a lot thinner than the original JJ one. Back to the question the leak is from the mouthpiece, I have flooded my unit that way.
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I find with the Drager one with the strap I don't have to bite down to keep it
I'm my mouth it just sits in place, is very easy to vent gas from loose lips
and have never got water in.
 
ccrdave said:
whats important when fitting aftermarket bov's is that the actual mouthbite opening is the same size as the JJ dsv. the rubber mouthpiece was chosen because of its orifice size and the thickness of the bites. If you put something on smaller it will alter the wob, give possible rise to co2 retention issues. We spent many thousands of pounds in testing getting the wob right and you can easily screw it up by fitting components that dont match. if you dont like the hard rubber mouth bite try an inspiration silicone one, the dimensions are the same.

Oh I should add there are other reasons why an aftermarket bov may not be compatible, bore size, flapper valve size and material, dead space, gas flow, etc. etc.
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Dave, As fitting a Shrimp to the JJ already incurs quite a WOB penalty, going from a DSV of 1.06J/L to ~1.44J/L for the Shrimp. How much have you noted that the WOB on the JJ increases by, when a less efficient mouthpiece is fitted?

On the OC side I am presuming that the Shrimp's performance isn't that much less that the JJ-BOV was. I understand somewhat recent testing on an ANSTI machine of the Shrimp identified its maximum performance of only 50lpm when at 50m resulted in a WOB of 3.24J/L. The tester noting that this BOV was on the point of catastrophic failure at even that low work rate and that it failed completely when the breathing rate was increased only slightly. EN250 obviously requiring it to be under 2.5J/L at 50m on air at 62.5lpm.
 
Contrary to many I like the Divex mouthpiece which is fitted to the five Shrimps I own - 1 x JJ, 3 x HH and 1 x Flex and I don't have any issues with water ingress into the loop(s).

I totally agree with Dave that the wide(r) orifice of the Divex mouthpiece contributes to an improved WOB, not only to the JJ but also, IMO, the other units I own. I also find the Divex mouthpiece much more comfortable to use than the softer Apeks which requires a firm 'bite' whereas the wider and stiffer Divex flange rests nicely between my lips and teeth without gripping. No doubt the chin rest of the Shrimp BOV helps this. To date, I havn't used a gag strap but will be trying the Drager in the very near future.

I'm not that interested in the test figures relating to WOB or OC performance. I just know that from about five years of use I am more than happy with the Shrimp. The longevity of its production, wide uptake and reputation is testament to IQSub's design. In terms of CE approval the Shrimp is, of course, presently a component under assessment as part of the XCCR approval process. Anyway, CE is just a couple of letters in the alphabet, that's all, and would not and does not have any bearing or influence on my aquisitions.

Sent from my SM-T800 using Tapatalk
 
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Brad_Horn said:
Dave, As fitting a Shrimp to the JJ already incurs quite a WOB penalty, going from a DSV of 1.06J/L to ~1.44J/L for the Shrimp. How much have you noted that the WOB on the JJ increases by, when a less efficient mouthpiece is fitted?

On the OC side I am presuming that the Shrimp's performance isn't that much less that the JJ-BOV was. I understand somewhat recent testing on an ANSTI machine of the Shrimp identified its maximum performance of only 50lpm when at 50m resulted in a WOB of 3.24J/L. The tester noting that this BOV was on the point of catastrophic failure at even that low work rate and that it failed completely when the breathing rate was increased only slightly. EN250 obviously requiring it to be under 2.5J/L at 50m on air at 62.5lpm.
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Brad at 40m with air as a diluent the JJ loop ventilated at 45lpm has a work of breathing of 0.82 j. I dont have figures but the testing we did with a smaller orifice mouthbite had a significant impact on wob as does the actual bites being too narrow. Anything added to the loop aftermarket may have a large impact on performance, of course the only way to determine that is to test, and just because a component works well on one loop design does not mean it will work well on another.
CE testing of a loops performance is done as a complete unit for very good reasons.

Tim I agree with you CE is just two letters and a large pain in the butt, on the other hand machine testing is of paramount importance to determine safe performance, and in my opinion ALL rebreathers should be machine tested and the results made avalible to prospective buyers
 
Tim1 said:
To date, I havn't used a gag strap but will be trying the Drager in the very near future.
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Well worth doing. This feature being an EN14143 requirement has to be one of the best single requirements for the safety of rebreather divers in the standard.

Tim1 said:
In terms of CE approval the Shrimp is, of course, presently a component under assessment as part of the XCCR approval process.
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Good luck to them, however, if the ANSTI testing of the shrimp that I have seen is anything to go on they will hit a brick wall (as did JJ with their JJ-BOV) when it comes to it meeting the EN250 requirement to ensure it is safe to bailout to. Not only does it have to be able to actually get to a gas flow rate of 62.5lpm but it also has to get under 2.5J/L when at 50m on air. Something your average poseidon or Apeks reg does easily and is expected of any good OC reg used for bailout.

ccrdave said:
Brad at 40m with air as a diluent the JJ loop ventilated at 45lpm has a work of breathing of 0.82 j.
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Thanks Dave, I hadn't seen the JJ-CCRs WOB at the lower rate used to test the scrubber duration.

ccrdave said:
and in my opinion ALL rebreathers should be machine tested and the results made avalible to prospective buyers
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Wouldn't that be nice.... Just as long as the criteria match, which is where the CE standards are useful, as everyone is on the same playing field.
 
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