Tell me what y'all think about this idea...

[Rick Murchison]

Genesis once bubbled...
Total tank fill cost is about $2.50 for Nitrox, and most of that ($1.50 or so) is filter consumption. Nearly all of the rest ($0.75 or so) is O2. The rest, all together is less than 10% of the total.

If you're paying $10/fill for Nitrox, you will pay for the compressor in ~500 or so fills....

Uh, you forgot to amortize your 4 grand over the life of the system... 1,000 hours, shall we say? That's another $2/fill approximately, if no repairs are required to *anything*.
And of course you have to figure your time is worth nothing...
Rick

 

[Genesis]

1,000 hours?

Rick, that's just the first VALVE INSPECTION interval!

Second, let's look at this, shall we? Let's assume that we only get 3.0cfm of "real" output ('cause we have to drain condensate, there is some gas lost when you bleed down lines, and besides, I'm conservative.)

Ok, so what IS 1,000 hours?

Its 1000 X 60 X 3, or 180,000 cubic feet of gas, which happens to be EIGHTEEN HUNDRED HP100 tanks.

I "pay" for the ENTIRE system, in saved costs, in FIVE hundred tanks. How do I figure this? I allocate all $7.50 of the difference between my "do it yourself" and "buy the fill" cost to the hardware account. Why wouldn't I? If I didn't buy the compressor I'd be giving someone else that money.

When is the compressor "worn out"? To what degree? Where I need to replace valves or rings? Those aren't expensive, and I can strip one of these things in about a half-hour to the bare block. They are NOT complicated or difficult to work on. Where I need to scrap the BLOCK? That's expensive, but is it realistic in 1,000 hours? No. In 2,000 hours? No. In 5,000 hours? Maybe. But by then I'll have filled something on the order of 8,000 tanks, and frankly, I don't think I'll give a good damn whether the compressor needs replacement or not! Hell, if I have to replace rings and valves every 1000 hours it is, in the grand scheme of things, inconsequential in terms of "cost per hour"; those things are NOT expensive.

What is my time worth? Exactly the same as its worth to get in the car, drive to the shop, and sit there while they fill my tanks. I can fill them myself in less time than I can do the above. So in terms of time, its a net WIN to own my own unit. It takes me about an hour to drive to the shop and back, and about a half-hour for them to do the job.

I can fill three tanks and top my pony bottle in about that much time, so on a "time" basis its a wash.

 

[jeffkruse2000]

Hey can you post a link on where you get your $100 O2 clean digital gauge please.

I bought the Halcyon whip. I added my own needle valve. The gauge that comes with the whip is a 2" gauge and it goes to 6000psi!!! What the hell is that all about? Oh, and you have to tap it to get a good reading. I have posted some pictures on my web site at http://www.seanet.com/~katrinakruse/mixing_log.htm
You can see the hoke needle valve and the $300 digital gauge I used.

Also, please post where you got your hyper filter. Some day I to will have to get a compressor because I hate going to the dive shop.

I am using the parker ST QD on my whip. I pay $25 for a K O2 and $65 for a T He.

I figure $10 for a trimix fill of 21/35 in an HP100. (The local dive shop fills tanks almost for free)

 

[Genesis]

Their "inexpensive digital gauges".

I emailed them and asked about O2 compatability. They replied and said they were clean from the factory, and compatable with Oxygen.

http://www.coleparmer.com/catalog/product_list.asp?cls=14309&par=&cat=&sch=290&sku=&sel=

I got the Hyperfilter from Clark Yacht Compressors in South Florida - they're a Lawrence Factor dealer. The guy here who sells the Alkin units ("The Curly One" on Scubaboard) is also a LF dealer now and can probably source them as well.

 

[jeffkruse2000]

Do these digital gauges turn off every three minutes? Sound like a pain and not very usefull?

 

[Genesis]

Its not a big deal. You just tap the "on" button to turn them back on.

I have interstage pressure gauges on my compressor, along with an analog one on the Hyperfilter, so I don't need the accuracy on my fill gauge except at the last few minutes, and its fine for that. On the O2 side its the same deal - you do the fill slowly, and just tap the button if it shuts off on you - if you're doing it at a slow rate it probably won't, other than once you shut off the fill and then let the temperature normalize before making your final O2 add adjustment (just click it back on, make the adjustment, you're done)

 

[jeffkruse2000]

Thanks for the quick replies. Wow. I just can't keep up with this board.

BTW I did call ColePalmer about the auto off. They said I could order one with the auto off feature turned off but it would cost more. She didn't give me a price but she though about $20 more.

Thanks again.

Jeff

 

[Genesis]

There's not much to these gauges. I will have to see if there's a jumper inside or something that can disable the "auto off"; I took the back off mine when I got it to check it out (just three screws) but if there is, then its no big deal to modify it - 30 seconds

Will post back here this evening if I find something obvious.

 

[jeffkruse2000]

Here is the "quote" I got for a 30 minute shutoff

The part number of the 68111-50 pressure gauge with a 30 minute auto-shutoff
feature is NCI 00125DF. Current pricing on this unit is $125, but since
this is not a formal quotation, this is subject to change. As this is a
special order item, it is not cancelable or returnable unless it is faulty.
Lead time is 2-3 weeks.

 

[Genesis]

and there is a pad for "SVE", but no obvious connection to it that can be cut, so it may be a custom firmware revision on the chip inside.