Basic question about scrubber media

[george1098]

Hi all
I just havce a basic question about the scubber media used in rebreathers. I understand that it is often the life of the scrubber media that is the limiting factor when determining the length of a rebreather dive. I was just wondering if this stuff has to be replaced after every dive, and roughly how much it costs and where you can get it. I am not considering buying a rebreather. I am just doing some research because I find it interesting.

thanks!

 

[caveseeker7]

Hi all
I understand that it is often the life of the scrubber media that is the limiting factor when determining the length of a rebreather dive.

That and the requirements to carry bailout gas are usually the limiting factors, at least on closed circuit rebreathers.

I was just wondering if this stuff has to be replaced after every dive, and roughly how much it costs and where you can get it.

Usually scrubbers are rated by duration, hours and minutes rather than times of use. Within limits you can use a filled scrubber more than once. Costs depend on the kind of absorbant (granular or cartridge), manufacturer (20+ % difference), grade (smaller granules tend to have a higher price) and location (shipping, sales taxes, customs).

That's for the material itself, different rebreathers take different amounts of absorbant so the price per fill varies, too. And different scrubbers designs have different effinciecy, so the price per hour varies yet again.

 

[SFLDiver3445]

Hi all
I just havce a basic question about the scubber media used in rebreathers. I understand that it is often the life of the scrubber media that is the limiting factor when determining the length of a rebreather dive. I was just wondering if this stuff has to be replaced after every dive, and roughly how much it costs and where you can get it. I am not considering buying a rebreather. I am just doing some research because I find it interesting.

thanks!

As caveseeker7 indicated, the cost and duration of the scrubber material can vary. Personally, I dive a Dive Rite Optima Closed Circuit Rebreather that uses the Extended Air Cartridge (EAC). The manufacturer has published test results that indicate the EAC last approx. 3 hours in duration, but that is heavily dependent on other factors (air and water temp, depth, etc.). However, practical use appears to indicate they last much longer. Myself and most of the divers I know, tend to limit the duration of the cartridge to 4 hours, and even that appears to be conservative, because we have heard reports of divers using it for much longer duration dives. As far as cost, the EAC cost approximately $30 each, but are not always readily available everywhere. I have a local dealer who stocks them, so it's not a problem for me. If I were to dive somewhere abroad, I would either have to take them with me or have them shipped to that location in advance, but that is often the case with granular sorb; althogh, granular sorb is much more readily available.

 

[george1098]

I c I c. thanks guys, that answeredmy question. Would you say thie extra cost it worth it for a rebreather set up?

 

[SFLDiver3445]

I c I c. thanks guys, that answeredmy question. Would you say thie extra cost it worth it for a rebreather set up?

That's a tough question to answer, because it depends on what you are going to use it for. The truth is, it's damn expensive, at least for me it was.

Back in the 90's I was heavily into open circuit deep mixed-gas technical wreck diving and I was now looking to get back into it. Instead of replacing all of my heavy doubles, I went the route of the rebreather, because it realy seems to make the deeper diving process so much easier. I'm still slowly edging my way back into the deeper diving, but I used it for many 60 to 140 foot wreck dives, and it's awesome! Saturday, I was on a dive boat all day (morning and afternoon trip) and dove four wreck between that depth. I never once had to switch tanks on my rebreather and I never once had to worry about having enough gas to complete the dives or the required decompression. Furthermore, I have been playing around with underwater photography, so the whole closed-circuit bubbless thing is very sweet as well.

But like I said, it comes at a price. I was told to expect to pay around $10K to $12K for the rebreather and the training (w/ a top instructor) and that was pretty accurate; however, I bought a top of the line additional computer (VR3 w/all the bells and whistles) with a 4th oxygen sensor for my rebreather and that put the grand total at about $14K to $15K.

For me, it's absolutely worth it! However, I can't speak for anyone else.

 

[caveseeker7]

Well, Billy Hearst once said "Pleasure is worth what you can afford to pay for it" and build himself a new home. :tongue:

For me it has been worth it as I simply enjoy it more than OC diving. And my Sport Kiss wasn't all that expensive.

If you're asking if RB diving can be justifed, it depends on the diving you do.
For extreme deep and/or long dives they can be the only way to go due to the gas extension they offer. Some of the cave in recent years would have been all but impossible due to the gas needs of OC diving.

The same gas savings add up fast if you use a lot of He on your dives. Curt Bowen of ADM did the math once for his diving, a Meg CCR paid off in just over a year - including the training.

On the other hand, if you only dive comressed air you get for cheap at the LDS a rebreather is an expensive proposition. In addition to purchase and training you'll need to buy pure O2, absorbant, batteries (depending on the model they can add up). You'll need three new sensors annually, figure around $220 or so. Maintainance for the units 2 first stages, bailout second stage on some units, O2 clean grease ... it all adds up.

You'll also want a deco computer that calculates pO2 (CC) rather than fO2 (OC/SC), a complete bailout tank with reg, maybe a booster for the O2 ... a bloody bottomless pit!

 

[george1098]

well I guess they aren't cheap, but I still think they are cool. Like I said, I'm not thinking about buying one, but mayb e a few years down teh road after I have done seome seriouse tech diving it may be an avenue i would like to persue. thanks guys

 

[Solitude Diver]

I’m diving the Evolution. It takes about 4 lbs of sofnolime (granular) to fill, and I get about 2-4 hrs per fill. (Recommended - 2 hrs for deeper dives, 4 hrs for shallower). The evolution has a “temp stick” which measures the temperature of the scrubber, and lets you know the percentage of use. (Back up with recommended times). Price in the Seattle area is running about $5 per pound or about $20 a fill.

The media cost does not concern me, because I have an ultimate nitrox mixing machine, that gives me ultimate mixes for each depth I’m at based on my preferred PO2, and it is only about $2 worth of oxygen per hour. That averages out to less than the cost of a normal nitrox fill so it is worth it (ignoring the initial investment for now).

The big savings comes from Helium if you dive tri-mix, etc. That is where I am heading. If you figure $80-100 per dive for Tri-mix on OC, compared to $10 (or less) per dive on a rebreather (including media), you can save almost $100 per dive. Just a little over a hundred dives and the initial cost of the rebreather is paid for. After that it’s all savings, plus the added benefits. You just have to get past the initial investment.

Now, all that aside, imagine having five to six hours of breathing time if you get lost in a wreck, (or in any trouble) compared to 20-60 minutes depending on depth. (Rebreathers have the same dive time at 250 feet as 50 feet). What you be willing to pay for that? Also, the constant changing 02 mixes (based on set PO2), shortens your deco time considerably when compared to OC mixes at set 02. That is certainly worth something as well.

A big initial investment, but well worth it if you use it enough.

 

[SFLDiver3445]

One other footnote: Locally, I have access to a dive shop that banks several different mixes, including Normoxic Trimix 21/35, so I pretty much use that exclusively for my recreational diving. The 35% helium in the mix helps with the ease of breathing in the breathing loop as well as helping with the effects of narcosis, so I tend to be VERY clear headed during those common recreational wreck dives in the 100' to 130' diving range, which is common here locally. Plus, the fact that my rebreather maintains an optimum PO2 level throughout the dive, minimizes the effects of the small amount of helium in the mix and minimizes any additional decompression.