MCH? And nitrox stick for an independent

[Diver-Drex]

I am in the market for a compressor. I have the space and I can run 230V single phase to the compressor. My budget is $8k.

Right now I’ll be filling cylinders for myself. In the very near term I’ll be operating as an independent instructor. Along with fills for classes, I’ll offer cylinder servicing. Service will include a full. It I am not going to operate a fill station per se.

Classes will be limited to 4 students. On pool days I’ll have 8 cylinders that will need to be topped off in between sessions. That’s four hours of my time and a bunch of trips to the garage. Having four more cylinders would cut my time in half.

My question is for my budget how would you spend the money? I’m in between an MCH6 and a nitrox stick or an MCH13 and PP blending until I can afford to add a stick.

 

[BRT]

I am in the market for a compressor. I have the space and I can run 230V single phase to the compressor. My budget is $8k.

Right now I’ll be filling cylinders for myself. In the very near term I’ll be operating as an independent instructor. Along with fills for classes, I’ll offer cylinder servicing. Service will include a full. It I am not going to operate a fill station per se.

Classes will be limited to 4 students. On pool days I’ll have 8 cylinders that will need to be topped off in between sessions. That’s four hours of my time and a bunch of trips to the garage. Having four more cylinders would cut my time in half.

My question is for my budget how would you spend the money? I’m in between an MCH6 and a nitrox stick or an MCH13 and PP blending until I can afford to add a stick.

A stick doesn't need to cost much.

 

[michael-fisch]

Get the MCH13 or MCH16. Those are real compressors that are made to be used. The MCH6 is an itty bitty little compressor that was made to occasionally fill tanks for 1 diver. If you are using it for multiple hours at a time it won't last.

Michael

 

[tbone1004]

as said above, sticks aren't expensive to make. Get bank bottles though, that's going to save you a lot of time and hassle. 4500psi bank bottles are around $350 each, so about $500 with fittings, lines, valves, etc. and are well worth it.
You may want to consider only filling with nitrox because switching back and forth requires you to purge the filter which is annoying.

Banks do however necessitate a bigger pump than the MCH6 though since they aren't rated for continuous duty. Up to you in terms of how much you're filling every day and all of that.
Having bottle service come full does make you a fill stations and opens you up to all of the liability associated with that, so make sure you're doing everything by the book.

 

[Diver-Drex]

Thanks for the replies.

A DIY stick is certainly an option for my own needs. I’m filling an AL40 with 50%, usually 30% in my lp85s and the 100s will get normoxic trimix.

But your comment about doing things ‘by the book’ makes lean to PP or a purchased stick. I see a DIY as a potential liability. The easy answer is to only fill air after VIPs and for classes. For EAN, students could test my cylinders and if they are doing the dives it would be at the quarry, where they bank nitrox.

The bank bottles always seem counterintuitive to me. You need the banks to handle peak demand your compressor can’t handle. But you need a bigger compressor, that can handle the peak demand, to fill the bank.

 

[grf88]

I don't understand how a DIY stick would potentially involve higher liability than PP as long as the correct testing of the finished mix is carried out. There is a risk of damage to the compressor if adequate precautions aren't taken however.

 

[tbone1004]

my comment about doing things by the book is making sure the compressor maintenance is done by the factory, you are getting air tests as required, etc etc. It's not a lot, just making sure you do it.
DIY nitrox stick is not one of the things I would be concerned about.

Banks aren't counter intuitive. You need a compressor that can run continuous duty yes, but they had a massive buffer to your ability to fill and then can run the compressor when you want to, or get the tanks filled quickly, then let the compressor run until it's done. I have a small portable compressor *Rix SA6* that is rated for continuous duty, so they do exist.

 

[Diver-Drex]

@tbone1004 - Do you have a low pressure set point for the bank that auto starts the compressor?

I don’t know if a jury and V&B (insurance carrier) would see the DIY stick as a ‘non-issue’. I’ll just stick to mixing for myself.

I’ll stay up in the maintenance and testing wether it is just me or anyone else breathing the gas I pump.

 

[tbone1004]

@Diver-Drex technically the pressure switch that cuts it off automatically will let it restart once the bank gets below the cutoff setpoint. If using a nitrox stick though, you don't really want it to run automatically with you not there since the mix can go sideways and blow something up

 

[Diver-Drex]

I was thinking you would bank air. To pump nitrox I would have to bypass the bank. Is that not right?