Slow & steady little compressor- curious and/or seeking

[jeff h]

You can get steel storage bank bottles that are rated for 4500-6000psi. With that amount of diving a 5cfm or larger compressor would serve you better. Having said that, a Bauer Varius compressor is a nice small 2cfm compressor that could probably run on a 110v motor. It will take about 40 minutes to fill one cylinder, and it is probably not rated for "continuous duty", meaning it will get hot and bad things will happen. So during the setup phase, if you need 12 cylinders/day, then it would need to run 8 hours continuous and be monitored. It's really not worth it.

If it were me, I would switch to a rebreather. That's exactly what I did after I was tired of filling doubles and paying for helium. You can use an AL-80 as a "bank" and just keep topping your bottles all week, and then fill them at the end. Even a SCR might be useful if you have nitrox and no O2. Or get that 2 cfm compressor and fill 12 "small" bottles per day in a couple of hours.

 

[tbone1004]

@iain/hsm it seems like you are talking about under-driving the SA3? Is that correct?

 

[iain/hsm]

Larger machine is more noise, thus timing issues with work, sea, sleep, neighbours etc. and/or tank-changes at X-minute intervals. I'd prefer to go to bed and wake up to a rack of ready-to-go bottles but fully appreciate the risks with "set & forget".

No you can't say that, RPM and the cooling Fan tip speed and angle noise are the culprits.
You can reduce loads of noise by going from a 6-blade fan to a 4-blade, even more if you adjust the blade angle from a zero degree pitch to say a 30 degree pitch only hitch from an engineering perspective is you reduce the cooling effect. LOL
Then your into the engineers vs salesmen and customers argument, we can make it cooler or quieter just not both.

Also you can produce a push to start and forget compressor most of our oxygen compressors are just that in fact all of them are that 24/7 running with fully automatic cut outs with safety back up and over-ride lock outs just adds to the parts list and cost.

(Amongst) my problem(s) is the down-time of compressors at dive-shops & Marine Park office (mechanical & professional), plus time, travel & traffic in drop-collect. Autonomy is becoming my general ethos with efficiency getting to be getting to more important than actual cost, though I'm still a wee start-up so up-front cost remains extremely relevant.

Power is my greatest consideration first. If you have 50Hz what is available? single phase or 3 phase and the voltage or any thing else
that would allow the options of motor size available to you to be made. 3 phase would be my preferred option as its cheaper to buy and
both parts and control are cheaper and it uses less amperage on start.
If single phase is only available to you then this limits your available motors (and so compressor size) they take much more amperage on start
and running cost for electricity may be greater.

In UK we have the same 50Hz and a 230 volt domestic supply to your home power costs is around 0.22p GBP per Kw/hr
while a 440 volts 3 phase supply to a commercial premise is (from memory is 0.12p per Kw/hr)

Steel banks only go to 2500PSI, no? Thus still need to let machine run at elevated PSI, then start machine to top-up before work-day or spring for the Haskel? I'm trying to not make yet another investment (in gear & importation, space, time, risks etc) if there's an option, though I appreciate that there's not much for options unless I take BRT's kind offer (thanks, but it'd strain the budget for now).
Thanks again, Andrew

Steel bank cylinders over here UK are 300 or 350 bar working pressure 4350- 5000psi working pressure and 50L water capacity by volume.
The USA have similar size and pressure cylinders under the DOT transportable regulations. Both are thin wall high tensile cylinders and require periodic hydrostatic testing that may present a problem to you on an island.

For those applications and for on board ships etc we both also have the ASME 8 Div 1 Appendix 22 cylinder specification that never needs a hydro test. Just a visual inspection every 5 or 10 years depending on gas content and application.

 

[tbone1004]

@iain/hsm and @seascaper if you have single phase available and it's 1-2hp motors, you can use a 3p motor with a VFD that accepts 1p/110v input and can output higher voltage and phase counts which is ideal.

 

[iain/hsm]

@iain/hsm it seems like you are talking about under-driving the SA3? Is that correct?

Not really. To be honest I'm not sure where we are going with the until all the facts are in.
A green light for the SA-3 from my point of view would only happen if the OP had only say 0.75Kw maximum power available to him.

At present to my mind I'm keeping the model and brands open as I'm not sure under running the RPM is a pragmatic option for the OP at this stage. 20 bottles and 6 to 12 fills a day will need more power than he may have available and even if he does, this remote power aspect to my mind is a problem that needs better understanding before we can make an informed choice.

If it turns out he can only run a 1HP motor I would still be be tempted to go with the SA-6 block and at some time in the future I may suggest he also considers a spare small diesel engine or spare petrol engine or in the event of a complete power outage a back up generator.

Although we haven't yet covered service parts and self maintenance costs on a remote Island but again as the SA-6 would fill twice as many cylinders in the same service interval as the SA-3 and the service parts aren't that much different in cost again I think I would be going for the SA-6 block than the SA-3.

 

[iain/hsm]

You can get steel storage bank bottles that are rated for 4500-6000psi. With that amount of diving a 5cfm or larger compressor would serve you better. Having said that, a Bauer Varius compressor is a nice small 2cfm compressor that could probably run on a 110v motor. It will take about 40 minutes to fill one cylinder, and it is probably not rated for "continuous duty", meaning it will get hot and bad things will happen. So during the setup phase, if you need 12 cylinders/day, then it would need to run 8 hours continuous and be monitored. It's really not worth it.

If it were me, I would switch to a rebreather. That's exactly what I did after I was tired of filling doubles and paying for helium. You can use an AL-80 as a "bank" and just keep topping your bottles all week, and then fill them at the end. Even a SCR might be useful if you have nitrox and no O2. Or get that 2 cfm compressor and fill 12 "small" bottles per day in a couple of hours.

With this idea your back to the same problem as discussed earlier.
For a remote Island and little power if you compress gas from ambient to 4500-6000psi your going to need much more power than pumping to 2500psi. Now as the power for the island is odd (from memory) at 110V 50Hz your going to need 1.4Kw and be running at 26 amps on the Bauer Varius. 26 amps in a hot humid climate, some would say Too much for too little for too long.

And again if you go down the rebreather route, for the amount of diving the OP is doing your going to need to consider an oxygen generator on site IMHO that and a commercial land fill licence for the mountain of soda sorb your going to need to dispose of unless of course like the Chinese your intent on developing your own man made offshore islands.
Could be a winner LOL but the budget just went up from $6,000 USD to $10,000 for a new oxygen generator and little 0.37Kw electric oxygen compressor.

 

[tbone1004]

@iain/hsm I was also half looking at it for me... I don't have the power ability to run my SA6's and due to noise can't leave them as gas so was looking at a Walter Kidde which uses a high pressure oil pump vs. splash lube so it can be under-driven, or a SA3. The WK has a massive cost advantage on upfront cost and rebuild parts though, Rix likes to rape us out here.

Can the 6's be run on a 1hp motor at super slow rpm's without problems? If so that may be my ticket since I already have a pair.

 

[BRT]

No you can't say that, RPM and the cooling Fan tip speed and angle noise are the culprits.
You can reduce loads of noise by going from a 6-blade fan to a 4-blade, even more if you adjust the blade angle from a zero degree pitch to say a 30 degree pitch only hitch from an engineering perspective is you reduce the cooling effect. LOL
Then your into the engineers vs salesmen and customers argument, we can make it cooler or quieter just not both.

Also you can produce a push to start and forget compressor most of our oxygen compressors are just that in fact all of them are that 24/7 running with fully automatic cut outs with safety back up and over-ride lock outs just adds to the parts list and cost.



Power is my greatest consideration first. If you have 50Hz what is available? single phase or 3 phase and the voltage or any thing else
that would allow the options of motor size available to you to be made. 3 phase would be my preferred option as its cheaper to buy and
both parts and control are cheaper and it uses less amperage on start.
If single phase is only available to you then this limits your available motors (and so compressor size) they take much more amperage on start
and running cost for electricity may be greater.

In UK we have the same 50Hz and a 230 volt domestic supply to your home power costs is around 0.22p GBP per Kw/hr
while a 440 volts 3 phase supply to a commercial premise is (from memory is 0.12p per Kw/hr)



Steel bank cylinders over here UK are 300 or 350 bar working pressure 4350- 5000psi working pressure and 50L water capacity by volume.
The USA have similar size and pressure cylinders under the DOT transportable regulations. Both are thin wall high tensile cylinders and require periodic hydrostatic testing that may present a problem to you on an island.

For those applications and for on board ships etc we both also have the ASME 8 Div 1 Appendix 22 cylinder specification that never needs a hydro test. Just a visual inspection every 5 or 10 years depending on gas content and application.

Downside to my small one is that it is high speed and loud.

 

[iain/hsm]

@iain/hsm I was also half looking at it for me... I don't have the power ability to run my SA6's and due to noise can't leave them as gas so was looking at a Walter Kidde which uses a high pressure oil pump vs. splash lube so it can be under-driven, or a SA3. The WK has a massive cost advantage on upfront cost and rebuild parts though, Rix likes to rape us out here.

Can the 6's be run on a 1hp motor at super slow rpm's without problems? If so that may be my ticket since I already have a pair.

Yes you can run the SA-6 on a 1 BHP motor by reducing the RPM and the discharge pressure
The cooling fan flow speed over RPM is as near as, and cancels each other out, so at half the RPM is half the flow with half the heat generated balanced by half the heat load generated cooled. (near enough)

You just cant fit the belt guard unless you lift the 1 HP motor up on a couple of brackets to make the drive shafts at near equal height. I need to work out the driver pulley diameter and the motor speed
Also the belt length will change if you want to retain the 14 inch shaft distance between centres.
You also dont want to get the driver pulley too small or the belt/belts will slip, two twin SPZ cogged belt size work better at tranfering the load than the old single SBA or V belt size.

Or use your VFD and direct drive the block variable speed. We did one some time back it was a thing of beauty but it will need an additional opposing shaft balancing plate if you remove the flywheel.

Now as for the WK alternative I'm guessing as the WK has not been made in 30+ years your talking ex army surplus cost and the rebuild parts similar are only available ex surplus while stocks last. In other words the parts were bought scrap and the price you pay is pure profit to the supplier you get them from while stocks last.

The Rix parts costs are by contrast frankly very reasonable, they at least offer a printed spares parts price list each year so to my mind are the only company that offer this. Spare parts costs are a critical aspect in choosing a compressor without knowing the spare parts price in writing up front I would not consider any brand or any model.

Now the issue we all have is that these Rix parts are for a military application with both a NSN and NATO stock number, each part has to be supplied with full traceability QA shelf life, etc etc. Further some of the testing (X-ray, dye pen and PMI cost more than the product itself.
Add to this that some of the Mil-Spec components O-ring for example have to be made from a known compound of known age and shelf like and each one identified with a yellow dot (I kid you not) All add a cost that only the military are prepared to pay.

In time as the full Mil-Spec stuff runs down and the commercial build alternatives are introduced these will replace the military model and parts will in addition be considerably cheaper.
Unlike your WK alternative I guess.

 

[tbone1004]

@iain/hsm what would max discharge pressure be? I don't need 300bar out of it, but I do need 250 bar.

Not really concerned with fan flow because I have removed the built in fan on my compressor and put an aux fan on there that moves the same amount of air but is on a separate power supply and stays on for 10 minutes after the compressor shuts off.

The mil-spec associated pricing is what kills the Rix from a rebuild. I don't have a current price list on me, but the maintenance kit was $700 at that time and I think has doubled since then