Transfill

[kenny kustom]

Recently got into rebreather diving.
I have a hollis explorer.
Two hp steel 40 tanks. 3442 psi
I also have six large steel tanks. 2-130's 2-100's and 2-80's.
By using the two 130 and one 100, would it be worth it to use them, to transfill into the 40's for the rebreather? Or would it be not worth it. ?
Where I dive is a 3 hour round trip to the nearest nitrox fill station.

 

[tbone1004]

you could setup a cascade system with the larger tanks yes, read some threads on how to work cascade systems to optimize pressure. You could also sidemount the larger tanks to help offset your lead requirements if you want and just keep the same mix in each set. Alternatively you could spend ~$3k and buy a small compressor, say Rix sa-3 and build a nitrox stick and blend your own if you have someone in the area to help you set it up and understand blending. May actually pay for itself quickly with the 3 hour round trip

 

[kenny kustom]

The compressor might be an idea.
I have my gas blender ticket.

 

[tbone1004]

I have no idea what fuel prices are in Manitoba, but the US government assumes each mile is worth about $0.65 between wear and tear and and fuel costs. For easy math we can even drop it down to $0.33 with 150 miles round trip, that's a cost to you of $50/round trip just in transportation. Plus assume $20/fill, so $70/trip. $3k will buy you a pretty nice Rix SA3 with a nitrox stick. 60 round trips and the fuel savings alone pay for the Rix. Assume 20 fills/year and you're at a 3 year ROI. The advantage to the Rix too comes in convenience of being able to fill on your own schedule, as well as being able to blend to custom mixes if you dive OC again or go to true CCR for your bailout mixes. Add a haskel down the road and you can fill pure O2 if you go that route.

 

[kenny kustom]

Thanks for the reply.
I'll start doing the transfill route. I'll see if that will last a weekend. If not.
Then I know what I need to do!

 

[tbone1004]

search for cascade calculations to see if there will be enough gas assuming they are all full at beginning. Then calculate the approximate number of weekends you plan on diving per year and you can figure out the ROI on the compressor. Also figure out if you have buddies close by who would benefit from it too and that will help the ROI out some as well if they pitch in for the compressor and/or supplies.

---------- Post added August 8th, 2014 at 07:06 PM ----------

search for cascade calculations to see if there will be enough gas assuming they are all full at beginning. Then calculate the approximate number of weekends you plan on diving per year and you can figure out the ROI on the compressor. Also figure out if you have buddies close by who would benefit from it too and that will help the ROI out some as well if they pitch in for the compressor and/or supplies.

The transfill whip does work on the compressors, it's the same fittings obviously so at least you won't lose money that way.

 

[kenny kustom]

I would only need it while I'm at the lake.
I have to drive past the dive shop to get there, so it's only a problem while I'm there.
I would start with the 2 40's full, and the three other tanks full as well.
I will try to find a cascade calculator.

 

[tbone1004]

ahh hah. Well, in that case a gas fired Rix is still a good deal to have for convenience. Other option is if your LDS will overfill LP steel tanks, you can get some LP121's and cave fill them. 175cf each at 3800psi.

 

[p1p]

I would get a booster before I got a compressor. Doing trimix on a compressor is rather tricky to get all setup and monitored properly, booster is pretty simple.

Only thing I use my compressor for anymore is to top off a dil tank, or my suit/wing bottles, and to drag down the last few hundred psi of helium out of a t bottle

 

[tbone1004]

Actually, that isn't that bad of an idea now that I think about it. May be a bit more awkward than a gas powered rix, but if you had a small gas powered air compressor *contractor type*, then you could power a small haskel. Start the cascade process, and use the haskell to scavenge the low pressure out of the bank bottles. I would only recommend this for your current situation if you plan on getting into O2 deco soon, or if you plan on getting a normal CCR later down the road where you are filling itty bitty bottles with pure O2 and/or dil