Filter For OPV

Frankie Pellegrino

Dear List
I've tried this and it works GREAT! I think this is the two cent answer to the Thousand Dollar question. What material will allow water to FREELY go through the OPV but block sofnolime chunks? Scotch Brite. It's that ugly green or blue stuff that you or your other half uses to wash your dishes.
What I did was cut a perfect circle of this material and sandwiched it in the OPV valve between it's body and interior cover. The material I used is about 1/2 inch thick. Make sure you singe the Scot Brite with a lighter so no little pieces of the material get between the diaphragm and the body. You have to buy a new (Apex cuff dry suit OPV valve) You need the back cover. Kevin's interior cover is cut a way to allow a CE approved venting issue, and the cover won't hold the Scot Brite material in place. When you get the cover, drill a bigger hole in the center so you won't have a problem with restrictions of water flow or air. Make sure you sand the edges of the drilled hole so you don't cut the interior of your counter lung. Put the PERFECT circular Scotch Brite filter into the OPV which has to come off of your counter lung. Then put a little RTV or silicone on the base of your OPV and threads and screw it back to the counter lung. I have pictures of every thing except the new interior cover. It's all ready installed on my counter lungs. I've tested this with sofnolime in the exhalation counter lung and NO sofnolime particles got between the diaphragm and the body. I've flooded the counter lungs and found no problems clearing the water. Be aware I'm not a engineer and there could be some bad points to this Mod.

BAD POINTS

1)Kevin's OPV has to vent a certain amount of air per minute if the lungs were to over pressurize

2) If you don't clean this filter with a garden hose it could get clogged over time. (unscrew the exterior cover and blast with garden hose)

3) I'm guessing but I doubt this would pass a CE test because your constricting the flow rate with the new filter and cover.

4) If you don't install the cover correctly and check it regularly it could come unscrewed causing a major flood and loop failure.

5) Your modifying the kit that a engineer spent thousands of man hours to design. Do at your own risk

GOOD POINTS

1) It works GREAT !!!

2) I'm not concerned with the CE venting issue. I feel this mod has more benefits then negatives. Remember what I posted I'm not a engineer. You should be a competent rebreather diver and be able to control loop volume of your kit.

3) When I figure out how to post pictures I'll send them to the forum

Please post good or bad points to this mod. I would like to here them all.
Cheers Frankie
_________________
Frank Pellegrino
Ouroboros number: 50

MHD

Funnily the azimuth SCR uses something similar (as in it green and looks like scotchbright) as a filter on the inside of the constant bleed valve to prevent junk getting in to it and effecting it's operation

Matt

Frankie Pellegrino

Pictures:

Picture #1: Two Scotch Brite filters cut into a perfect circle.
(side view & top view)

Picture #2: OPV with Scotch Brite filter installed
(You'll notice the factory interior cover won't hold the filter in place)

Picture #3: interior cover of OPV (this cover needs to be replaced if you
installed the filter)

Picture #4: OPV without filter ( You can clearly see how sofnolime particles
can get between the diaphragm and body
with out the filter)

Modification issues
I've never had a flood or loop failure in my kit...But a few of my negative tests have failed because of particles stuck between the OPV diaphragm and it's body. I hope the pictures paint a much clearer picture of this mod. BUT PLEASE remember this mod won't allow your lungs to vent accordingly to CE specifications. I've flooded the loop with a teaspoon of sofnolime in the exhalation counter lung and NO particles got to the diaphragm.. Other Boris divers stated that they had loop failures and believe it was the failure of the OPV. I personally feel this mod has more benefits then negatives and makes the OPV much more muck resistant.
Cheers Frankie

JJK

What about oxygen compatibility of the materials used in the modification?

JJK

__________________
Fate is the hunter

Frankie Pellegrino

What about oxygen compatibility of the materials used in the modification?


That's a good question !

I don't know what the answer is ....But it's just like a soft plastic material. I can't see it being a problem in the counter lung. I know it's mildew resistant and doesn't degrade in a wet environment. And it's used to wash your dishes. I know anything in a 100% 02 environment will degrade quicker then in air. Also theres no oil base lubricant being used on this mod. So I'm not worried and comfortable in being my own Guinea pig. But that's something each person has to decide on thier own.
Cheers

Dave Sutton

Hi Frankie, long time no see! Think the last time I saw you were were at Dans eating tacos...

What comes around goes around... the old DIVEX 3000 semi-closed rebreather backpack that was hooked to the helmet in our old mixed-gas system when I worked offshore had, you guessed it: Scotchbrite pads as the original factory 'sorb filter to keep the crap outta the rest of the rig. There was a pad top and bottom on the scrubber and it worked well and was the factory thing. "Chore Girl" was the brand we used offshore as we got it thru the supply system... I think that the femi-nazis ended up getting the name changed to "chore boy" so look for it under that name. That stuff was the same only not formed into pads, we used "wads" of it in the rigs. For the Boris application the pads would be great.

The DIVEX system was used with pure 02 for deco as well as for mix on the bottom and this system was perfect.

When divers write about "oxygen compatability" in the low pressure environment I always laugh.... for an 02 fire to occur you need fuel, heat, and oxygen. Ask yourself "where will the heat come from?" Bottom line: 02 fires take place in diving systems due to adiabatic compression, almost *always* caused by the sonic shock wave behind a small piece of debris in a high pressure line when the velocity of the gas is high, like when *instantly* pressurizing an 02 line with a ball valve (bad practice). You could smear the low pressure side of any rebreather with axle grease and there would never be an issue. It's simply not a problem. We used to grease the internal O-Rings of ALL of our 02 systems offshore with vaseline (petroleum jelly!). This is just like people thinking that any PP02 over 1.6 is going to kill them... just aint the case. Comes from lack of knowlage in the people doing the training. Use the pads and live long.

Good on ya for rediscovering this. Must be the good Jersey seawater...


Dave

__________________
.

"All animals are equal, but some animals are more equal than others"


Professional Small Boy: Never Successfully Cubicled.

Sutty

Already been there with my Classic Kiss too. I used to get occasional leaks from the OPV (an apex suit shoulder-dump valve) due to odd bits of lime getting into the valve. I now have a disk of scouring pad under the valve (fits nicely due to the head design. No problems since.

__________________
Never forget that life is a finite resource.

JJK

Vaseline on O2 components, PPO2´s higher than 1.6 O2 being no potential killer...

Has your number of T/O´s and LDG´s been equal lately or did you have to bailout now and then? :-)

JJK

__________________
Fate is the hunter

Dave Sutton

Never needed to bail out of a jet or a rebreather.... but fully prepared to do either..

With formal schooling at the degree level in diving science and several years spent as an industrial mixed gas diver using rebreathers every day, my opinions are based on the facts personally observed in the conduct of literally thousands of mixed gas dives *averaging* 500 FSW. In the oil field, what we do as divers for "extreme sport" is a daily job.... just another days dive and depth bonus opportunity.

02 cleaning is a great idea if you are working with *high pressure* 02, but is nonessential in a low pressure environment. Feel free to do it, but low pressure seals in a 02 environment can be lubed with about anything. Feel free to use Halocarbon if you like, but we survived using vaseline or normal siliconme grease at low pressure and reserved Halocarbon for HP regulators and valves where there *was* the potential for high temperatures caused by debris impinging into a sonic velocity gas stream. Ain't nothing else going to cause enough heat for a fire!

In water-pure 02 deco at 40 FSW was observed by me personally for literally *thousands* of hours., right out of the US Navy dive manual and using the tables custom produced for us by Dr. Bill Hamilton..... and we never saw an 02 tox symptom ever. We did *much* longer 40 foot chamber decompressions (hours) after the in-water portion of the deco was done and never saw an issue there either. Every 6 months each diver did a 60 FSW for 30 minute chamber run on pure 02 for the "02 tolerance test" and in literally hundreds of chamber runs we *never* had a hit. Don't take me wrong: 02 tox *is* an issue, just that it's a "fuzzy" limit and not a "hard" one. Go see how the SEALs use LAR-V's for emergency combat escape dives to 75 feet plus (diving in an emergency to below hand-grenade sinking depth) and then talk to me.

My only point is to just be reasonable in your approach to these things and let's not all get nuts about "02 compatability of scotchbrite pads", that's all. They are a great tool for many things. Come to think about it, we used them as noise silencers in our helmets too (Divex 3000 and Aquadyne GH-2, each with their umbilical-fed SCC rebreather systems).


Sorry to get off topic.... but it's good data. I only saw two divers die offshore... both due to low PP02 (in one bell-bounce system accident...) but never saw an 02 fire or a 02 tox symptom ever.





Dave

__________________
.

"All animals are equal, but some animals are more equal than others"


Professional Small Boy: Never Successfully Cubicled.

Joe

Quite true Dave.

When was the last time any of us O2 cleaned a second stage and even if you did how could you possibly expect it to remain O2 clean?

Heat is generated going from low pressure to high pressure. Heat is lost going from high pressure to low pressure. Upon entry into the LP chamber(s) the gas is cool, much the same as when you crack a tank valve open more than a trickle and the valve freezes.