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Making my Rix SA6 better

Discussion in 'Compressors, Boosters and Blending Systems' started by tbone1004, Apr 4, 2019.

  1. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
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    Intake side
    This is largely going to remain in the garage for now, but will ultimately end up in an enclosed trailer at some point.
    Intake filter. Grabbed this Solberg despite @iain/hsm 's aversion. It is 2" to minimize the pressure drop, and hopefully keep it quieter than a smaller one. Rated at 135cfm, and as this is going to be going about 1.35cfm, I can't imagine I'm going to have any issues. We use these on all sorts of compressors at work including on our big 2500cfm behemoths and have not had any issues with them.
    https://www.amazon.com/gp/product/B00H43MP72/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
    Main reason to keep it at 2" though was to minimize adapters going into the nitrox stick. Grabbed one of these guys just to make life easier during the blending portion. Have a 2" T with reducers to put the solenoid and flow meter up top, then another at the bottom for the O2 sensor.
    https://www.amazon.com/gp/product/B00NG2XEHK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
    Could I have DIY'd cheaper? Obviously, but getting great pricing on both of the above through work meant that it was not worth my time/hassle to deal with making the mix stick from scratch.
     
  2. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
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    The parts got in a few weeks ago, but I just got back from 2 solid weeks of teaching obligations. The last big hiccup on time is my niece showing up. She should have her birthday by the end of the week and after that trek to Raleigh I should have some time to get to work on the Rix. My workbench is done and waiting, and while @victorzamora will probably argue that I need to finish my DPV project first, I'm thinking that the weekend of the 25th will be dedicated to starting work on the Rix.

    Step 1. Get everything cleaned. I have the compressors almost fully disassembled when Victor and I first found out they were in much worse shape than I initially thought, though that embarrassingly was in the fall of 2014. At that point I couldn't justify spending the money on rebuilding them as each of them needed close to $2k in parts, but times have changed. Ultrasonic is ready and the big parts cleaners at work will make it a quick job of getting everything cleaned.

    Step 2. assemble the compressor to stock-ish. Since I'm going way out of bounds on what this thing is going to ultimately me, I want to start with a clean slate with the compressor "as stock". That will include the stock fan, but will not be run to stock speeds. My garage does not have 220v power, and at this point I can't put it in there, so I am limited to the going slow. I also don't want to mount a different motor and do the initial run-in at work where I have unlimited 3p power. Outside of the motor, the only real thing that is going to be different is a ball valve and QF4 on the outlet instead of a hose, and an adjustable pressure cutoff switch being added to cut the motor off.

    Step 3. I am going to let the compressor run through an empty filter for a while to clean itself out and start watching with a thermal camera to see where the hotspots are and if the stock fan does the job. Once it clears out, I'll send it out for gas analysis without a filter cartridge just to see what I'm getting directly out of the coalescers.

    Step 4. Start filling bank #1 to ~4500psi ish. They're 4500psi banks, so that's not the issue, but they may only get filled to 4000psi or somewhere in between. What is going to determine this is watching the logs from the VFD and thermal camera. Depending on what happens with the heat on the final stage, and the speed reduction since the VFD will be set to constant current mode, I may determine that the lower pressures make more sense if we start getting really inefficient or hot on the higher pressures. Who knows. Perks of having nice tools to play with. Noting the RPM at max pressure is going to be critical so I can set the compressor to run at whatever that RPM is for mixing nitrox. If running air I can leave it in constant current to maximize speed, but can't do that while blending.

    Step 5. Based on temperature from the fan, convert to electric fans. Does that mean one big fan to replace the existing one? Does it mean several small axial fans mounted to various points on the compressor? Unsure, but will figure it out. Current thinking is a 10" diameter axial fan that will be tied to the input on the VFD and the auto-drains. Will be on whenever the compressor is plugged in to give some extra cooling after shut down in case there is any latent heat that wants to build up and just requires you to turn the fan off manually.

    Step 6. Auto-drains. Will be using surplus Asco solenoids from work and will be figuring out the timer mechanism on them. I'm assuming draining in sequence is better than draining all at once. Will have two on the compressor itself, then one for the big coalescer on my filter stack. The drains on the compressor will be mounted to the frame so they don't shake the actual coalescers apart as Iain brought up in a previous thread. Power on the drains and fans will be tapped into the inlet of the VFD for now which is slightly annoying since they will need a separate switch, but oh well. Ultimately I think I will put a relay on there that is tied to the VFD that will control everything automatically, but that's down the road. Auto-drains are very much a requirement to be able to let this thing run without babysitting it, so getting this right is a HIGH priority once the compressor is up and running.

    Step 7. Nitrox stick. Ultimately this thing needs to make EAN32 100% of the time. I have no use for banking air at home and anything that I would need compressed "air" for may as well be nitrox. With the nitrox stick, the VFD will have to change to constant RPM mode to match the O2 generators output. Will also be hooking up the normally closed O2 solenoid to the VFD so the compressor controls the flow.

    Step 8. With the steps above the compressor should be running stable. Next step wil be dependent on how motivated I'm feeling at learning arduino/rpi etc. I will either go with a screen that will display values, or just use cutoff switches. I would prefer to use the screen, but that's a LOT more work.
    Controls would ultimately.
    1st & 2nd stage pressure to look for valve failure.
    3rd stage will be looking for duration maintained below a setpoint looking for leaks or excessive hammering.
    1/2/3 stage temperatures. The key here is keeping the PTFE o-rings under 400f for longevity
    Control of the fan based on the temps above with an auto-cutoff once they get back to some predetermined temperature, likely 100f or so.
    Control of the solenoids.

    I hope to have step 1 and 2 done by the end of the month barring any issues. Step 3/4 hopefully by the end of June since I have to get the motor mounted and VFD programmed with both tested before hooking up to the compressor. Step 5/6/7 will hopefully be done by end of July just based on vacations and weekend commitments. Step 8 who knows but unlikely before end of the year.
     
    Johnoly likes this.
  3. Billy Northrup

    Billy Northrup ScubaBoard Supporter ScubaBoard Supporter

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    This is awesome, I love it.
     
  4. RayfromTX

    RayfromTX Student Of Gas Mixology Staff Member ScubaBoard Sponsor

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    Will you be able to control it from an app on your phone?
     
  5. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

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    Not in the plan. Getting start/stop control and monitoring would be easy, getting the blending stick automated and the ability to actually control the speed of the compressor would be quite a bit more difficult and involve programming of a PLC. Several guys that work for me can do it, but the cost/hassle to put it in is not worth it for intermittent use.
     
    Johnoly likes this.
  6. victorzamora

    victorzamora Solo Diver

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    Yes, I will argue that. Not having a scooter is negatively impacting my cave diving. Not having a fill station in SC isn't. Get your priorities right!

    My recommendation here would actually be to cut the fan off at a temp delta from ambient. At some point, the fan is going to be pretty ineffective because of the small delta of heads-to-ambient and won't be doing much cooling. 100F in the summer might be too low, but too high in the winter. Something like Ambient+30F is where I'd start.
     
    RayfromTX likes this.
  7. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
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    @victorzamora I'm working on the scooter, it's been a little crazy at work and haven't had time to fab the motor mount yet....

    on the fans for ambient+x is probably a solid idea, but will very much need your assistance on that towards the end of the year when we get bored
     
  8. RayfromTX

    RayfromTX Student Of Gas Mixology Staff Member ScubaBoard Sponsor

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    Dude, I was totally kidding and the fact that you considered it a serious question earns you my respect.
     
  9. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

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    @RayfromTX since the PLC is going to be raspberry pi based which has internet connectivity, if I was an app developer it should be fairly simple to have it spit out the data that it is monitoring and put a start/stop button on there
     

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