Control options for compressors with single phase & 3 phase AC electric motors.

[PBcatfish]

I'm interested in solutions that handle the following:

• stop the compressor if the oil pressure in the last stage isn't built up after 10 seconds
• timer (15min/6s) for condensate draining
• turn off the compressor at a specific pressure

I've been using a self-designed controller since two years successfully, now redesigning that so I can control it from my phone.
...

Oil Pressure switches are easy enough to find. The same is true of delay on break timers. 10 seconds is a commonly available setting. Pressure switches can be found at most auto parts stores. The timers can be found at industrial supply places like Grainger.

A repeat cycle timer would give you the on/off timing you want for the drain. They come in many shapes & sizes. You can get them from Compressor supply guys like August Industries or industrial supply places like Grainger.

Air Pressure switches in the 3,000 to 4,000 psi range are similarly available from August & probably industrial sources as well. Some are adjustable as a process variable.

You could also use a small PLC in place of the timers, but for something this simple, the timers are probably cheaper & easier to set up.

I know how to set up standard industrial controls as described above. I don't have experience setting up remote control from a phone.

 

[PBcatfish]

...Isn't the major drawback of oxygen concentrators that argon is part of output?

I'm working on an automatic continuous blending controller at the moment, using a K14 with 900 to 1000 rpm. Oxygen and helium flow are controlled by motorised needle valves. Gas sensors measure the mixed gas, a processing unit reads the sensors and adjusts the needle valves.

I'm just starting to look at concentrators now. I am unaware of their drawbacks. This is the first I have known of argon being a concern. Please fill me in a little more about their use & idiosyncrasies. I'm looking to learn about them. I am not well informed at this time.

Your blending application seems like a natural fit for a PLC with a couple of analog cards on it. I'm curious what type of processing unit you chose to use. If you were to use a PLC, then you would automatically have a large number of timer functions at your fingertips for no additional charge. A PLC does require some programming though. The general family of programming languages are known as ladder logic.

It's interesting that you chose to use needle valves & motors. My first thought would have been to pulse width modulate solenoids. There is certainly more than one good way to skin a cat.

 

[tbone1004]

@PBcatfish the concentrators scrub most of the nitrogen out and the balance remaining is predominantly O2 and Ar. Technology is pressure-swing adsorption and O2 and Ar are similar enough that it's very difficult to distinguish between the two. It essentially means the mix coming out is 95% O2 and 5% Ar.
For rebreather use in lieu of distilled O2 this is a bit irritating as the Ar builds up so you have to dil flush every once in a while but for OC use it's completely inconsequential and is the predominant method for making O2 in remote parts of the world like Truk.

 

[PBcatfish]

I strongly support your venture on that as that is the ultimate goal I have with my Rix build. The only compressor you'll be able to practically do this with is a Rix though as an FYI as the others don't have wide enough of an RPM band and are also too big/fast. You have to slow the pump down to about 1.5-2cfm depending on nitrox mix to sort out the O2 concentrators output which is quite low. Biggest ones are 10lpm so you'd have to daisy chain them to the stick.

I had only casually looked into this in the recent past. I haven't really had time to do any proper research.

What I did find so far was that most home concentrators usually either have a 5lpm or 10lpm capacity and can be throttled down from full capacity. since a compressor like a Bauer Jr runs about 100lpm, that would only allow about a 10% boost if you ran the compressor and the bigger concentrator at full speed. Adding more concentrators is an expensive option. Running the compressor more slowly to boost up the mix would seem a slower but more cost effective choice, assuming that the compressor is OK being run more slowly. I do not know how much wiggle room there is on compressor speed. I do know that the electric version of a Jr & the gas version of a Jr have different speeds by a few hundred RPM, so there is at least a little room there to play. I'm curious to learn what the acceptable range is.

 

[PBcatfish]

If the compressor speed can't be fiddled with very much, then another option would be to divert a percentage of the enriched output air from the compressor back into the inlet, so that it can get a second O2 boost. This adds wear & tear to the compressor as it requires more total pumping. It is also similarly slow compared to running the compressor at lower RPM.

 

[PBcatfish]

@PBcatfish the concentrators scrub most of the nitrogen out and the balance remaining is predominantly O2 and Ar. Technology is pressure-swing adsorption and O2 and Ar are similar enough that it's very difficult to distinguish between the two. It essentially means the mix coming out is 95% O2 and 5% Ar.
For rebreather use in lieu of distilled O2 this is a bit irritating as the Ar builds up so you have to dil flush every once in a while but for OC use it's completely inconsequential and is the predominant method for making O2 in remote parts of the world like Truk.

Dude, you're like an encyclopedia. This is great info.

 

[PBcatfish]

I'm finding this all very interesting and useful. One question; where do you put the jumper on a 3 phase magnetic contactor when using it on single phase?

Tracy already covered you on the wiring change. I'll add to that, you need to check the current capacity on the contactor & the overload relay. A single phase motor draws a lot more amps than a 3 phase motor of the same HP rating.

 

[tbone1004]

I had only casually looked into this in the recent past. I haven't really had time to do any proper research.

What I did find so far was that most home concentrators usually either have a 5lpm or 10lpm capacity and can be throttled down from full capacity. since a compressor like a Bauer Jr runs about 100lpm, that would only allow about a 10% boost if you ran the compressor and the bigger concentrator at full speed. Adding more concentrators is an expensive option. Running the compressor more slowly to boost up the mix would seem a slower but more cost effective choice, assuming that the compressor is OK being run more slowly. I do not know how much wiggle room there is on compressor speed. I do know that the electric version of a Jr & the gas version of a Jr have different speeds by a few hundred RPM, so there is at least a little room there to play. I;m curious to learn what the acceptable range is.

Generally speaking with splash lubricated pumps you can go down to somewhere like 70% of their rated RPM.

You need ~14% of O2 being added to get EAN32. 14/0.95~15%, so on a 100lpm/3.5cfm pump you'd need 15lpm of concentrator. At 5lpm you top out at about 36lpm or 1.3.
The JR can go down to about 1500rpm/82lpm/2.9cfm on the E1 configuration but I wouldn't imagine it would be happy much lower than that. You could probably get close with a 10lpm concentrator but I think you'll be a bit disappointed with lean mixes.

 

[Gone for diving]

@PBcatfish the concentrators scrub most of the nitrogen out and the balance remaining is predominantly O2 and Ar. Technology is pressure-swing adsorption and O2 and Ar are similar enough that it's very difficult to distinguish between the two. It essentially means the mix coming out is 95% O2 and 5% Ar.
For rebreather use in lieu of distilled O2 this is a bit irritating as the Ar builds up so you have to dil flush every once in a while but for OC use it's completely inconsequential and is the predominant method for making O2 in remote parts of the world like Truk.

I thought someone on scubaboard mentioned that there is some other zeolite that does a better job removing argon,. Do you have any practical experience with changing the zeolite, for more concentrated o2?
So it's more pure.
What type.
Etc

 

[PBcatfish]

Generally speaking with splash lubricated pumps you can go down to somewhere like 70% of their rated RPM.
...

Lubrication is one concern. Cooling the tubes between the cylinders also seems worth considering. With a slower running compressor, the fan is also slower & that makes me wonder if the cooling may become insufficient.

Maybe I might need to poke around with an IR thermometer sometime