kiss valve / needle valves

[rbdave]

Hi All,

I'm hoping someone can explain the difference between a standard kiss valve and Kerry Mckenzies needle valve.


Thanks

Dave

[caveseeker7]

The KISS has a small, unadjustable orifice. Adjustments to O2 volume are made by adjusting the interstage pressure on the reg.
Kerry's needle valve is adjustabel. Either of those rigs is rare on Scubaboard.
Try Dive-Oz, there is at least one KISS diver, several Dolphin conversions using Tubby's idea (not parts, though, it's strictly DIY) including himself.
There are threads on it, too. Don't know if Tubby's site is back up yet, but it explained the conversion he made rather well.
I've had off the board contact with 2 or 3 of the divers down under, they've always been accessable and helpfull.

[dirt diver]

Caveseeker's reply is accurate, although a little misleading. Here's a different perspective on it:

KISS orifice: adjusted PRE-DIVE via the 1st stage interpressure to just less than the rest consumption rate, so that the PO2 is slowly falling at all times. During the dive, PO2 is adjusted UP by manually adding a small amount to the loop as needed, say every 10 to 30 minutes. NOTE: the orifice and interstage pressure are tied closely; as the ambient pressure approaches 1/2 of the interstage pressure, the orifice falls out of critical flow (choked flow, sonic flow, whatever) and the mass flow is notably lower when ambient is at 60%+ the interstage pressure, requiring more frequent addition. With this configuration, the O2 level is "fail-safer" if you forget to check the PO2. Max depth without frequent addition would be around 150fsw, worse as you went deeper. I haven't dived that deep, so I can't offer any empirical advice. Gordon, if you're out here, feel free to critique my description...

With a needle valve, you're still running critical flow during the shallower portions of the dive, but since it's an adjustable orifice, you could reasonably expect to dive to twice the depth (or more). HOWEVER, it requires just as much attention to PO2, particularly at ascent. If you've tweaked it to account for depth or workload, then you have to tweak it back down as you relax and/or ascend or the PO2 will go too high. Your chances of oxtox are a lot better with an adjustable orifice if you forget to check often enough.

Unless you're doing a lot of deep dives, the orifice method is substantially safer for normal recreational depths, although more of a pain (frequent addition) at greater depths. You could probably take either mass injection system to 300fsw, but the KISS valve would be more of an annoyance down there.

Here's a few different sites with info about CMF (constant mass flow):

http://www.optimal-systems.demon.co.uk
http://gc.discussing.info/gs/f_gas_supply/pneumatic_system_construction.html
http://www.lenoxlaser.com/calculator/orifice.html

[lonestarfl]

This is exactly backwards. The deeper you go the greater mass of oxygen molecules in the loop and the LESS frequent that a manual addition is required assuming your metabolic rate is constant. All rebreathers "move" slower the deeper you go requiring less and less oxygen addition. They are most dangerous and require more monitoring shallow.
Lee

[TechBlue]

Lee, right on! Also while we are on the subject the new KISS orifice will get you down to 300' so deep is all in the definition, and there are very simple ways to bypass that depth limitation if you so desire, the disadvantage of a needlevalve is user error of which there is always the potential.

[Scubaroo]

Kerry's site is back up, with disclaimers:

http://www.vk4tub.org/rebreather.htm

[lonestarfl]

I am in the process of converting a deep modified Dreager to a mCCR with the help of Gordon Smith's parts. I have the KISS valve and DS4 plug.
I have an Atlantis and a Ray. I want to use the Ray split over the shoulder bags with the Atlantis hoses and DSV. I already have the adaptors for the P-ports. I will use an oxygauge and an Ox2/Air X to monitor. I just haven't decided about the scubber. I am not enamored with the Atlantis design, but the Ray scrubber is too small. I want a 4-5hr BT capability. I have thought of using two Ray scubbers if the WOB isn't too high. I have also out-sourced
an FMG scrubber which is en route from Germany and may work. I have also looked into some of the scubbers off the Russian rebreathers. If you have any thoughts or suggestions, let me know.
Lee

[deepblueh2o]

I just wrote this on another thread, but here goes again. You can take two of the cannisters, cut off opposite ends, plastic weld them, and have one, 6 pound cannister. looks just like the one you have, only longer. Also, Bird Precision makes Ruby orifices any size you want, about $75. God only knows what gas nuts can do with that knowledge.

[TechBlue]

I just wrote this on another thread, but here goes again. You can take two of the cannisters, cut off opposite ends, plastic weld them, and have one, 6 pound cannister. looks just like the one you have, only longer. Also, Bird Precision makes Ruby orifices any size you want, about $75. God only knows what gas nuts can do with that knowledge.
Welding two cannisters together will increase your WOB dramatically and will not neccesarily give you a 4 hour duration scrubber there is a formula that relates directly to the diameter and length of the cartridge. You could just get the ExtendAir cartidge and extended scrubber and solve all your problems in a nice clean package and improve your WOB to boot.

[deepblueh2o]

I've been on my cannister for 6 hours.

[TechBlue]

How do you calculate your duration? Believe me I am not knocking you, we cater to the homebuilder, but as a business we have to back up whatever we say with hard data.

[deepblueh2o]

I did it once using the dive sorb small grain. cannister sealed when not in use. two days of diving, 6 dives. was closer to 5.5 hours.
This is where I should say that I have experience with what a CO2 hit feels like and how to respond when it happens. My normal usage is large grain 3 hours, then thow it away cause that's the end of the day.