My RIX SA3-E

[SurfLung]

My RIX SA3-E
- I bought a used RIX SA3 in 2014 and have been repairing, rebuilding, and improving it (I think) these past few years while also refilling my Scuba tanks with it. Most of the project has been documented on the two vintage diving forums. I didn't realize there is a lot more RIX related info on THIS forum. So, I thought I'd join the compressor discussion and introduce myself and my compressor.

- This is what I received from the seller... Plus a couple of expired composite cylinders for a storage bank. It was being used for compressing air at an airgun or paintball shop prior to me.
- A friend on the VDH forum found me a used filter array at a reasonable price. This and some basic stuff got me up and running to pump lots of air in my first summer of compressor ownership.

 

[RayfromTX]

They are a joy aren't they?

 

[SurfLung]

Goal From the Start: Achieve 3 cfm...
- "A Joy"... For me it has certainly been all of that and then some. But for others, it might look like a lot of Fixer Upper work. I removed the auto-drain system to simplify setting it up and got an electrician to wire it properly for my 220 dryer outlet. My friend AntiqueDiver (from the VDH forum) sold me a filter array from an old Olmeva 6000 compressor. And I was pumping clean, dry air right away. But it wasn't long before I realized my RIX SA3 was not pumping anywhere near the 3 cfm it was supposed to. And that's where I began a personal mission to achieve the full 3 cfm fillrate.

- My friend AntiqueDiver had the idea to calculate the RPMs from the pulley/sheave diameters. And sure enough, the pulley on the motor was downsized and the compressor was running about half its 2300 rpm specification. We got a bigger pulley and that speeded up the fill rate quite a bit. Later on, I got an adjustable sheave and a laser rpm reader and was able to adjust the compressor rpms to 2260... As close to 2300 as I can get.
- It still wasn't filling very fast and AntiqueDiver said I should look for leaks. And sure enough, I found a crack in one of the ports on the 3rd stage moisture separator (one of the two black tubes above). Christa at RIX helped me out here and I got a new one for a reasonable price. That got the fill rate to go faster again.

- I've done a lot of re-plumbling during this project. Above is the most recent configuration. I have a pressure gauge before the BPR, one up on the filter array, and one at the fill whip. I re-built the BPR and if you look at it, you'll see I have the air coming out the top and moisture drain on the bottom. I get considerable moisture out of the bottom of the BPR. The pressure switch can be seen between the gauge and the 3rd stage over pressure valve (OPV) in the foreground. And the 2nd stage OPV can be seen in the background between the 3rd stage OPV and the BPR.

- My filter array is from an old Olmeva 6000 (now Coltri Sub) and it has complete moisture and filtration capabilities. The first tube is all moisture accumulator... With a vertical dip tube on the bottom and drain valve. The second tube also has a drain valve but not dip tube. I use a full length Lawrence Factor (LF) pre-pack with 13X in the 2nd and 3rd tubes. And the fourth tube has LF 13X, Hopcalite, and Activated Charcoal filter media.
- I have re-built the piston heads twice with cleaning and new O-rings.
- I re-ringed the pistons once a year ago... And achieved 2.7 cfm fill rate.
- I replaced a broken 3rd stage piston more recently.
- I re-ringed the new 3rd stage piston and "re-freshed" the rings and cylinder walls on the 1st and 2nd stage pistons at the same time.
- And the RIX now fills at a fill rate between 2.9 to 3.1 cfm depending on atmospheric conditions.
- So after 4 years of ownership, I think I finally have it working perfectly.

 

[iain/hsm]

With all this "Joy" sloshing about I guess its about time for some killjoy. Trust a Brit to kick a dampener in the works.

First the low RPM issue was due to the original 2 pole 3600RPM motor being replaced with a 4 pole 1800 RPM motor.
That we can blame on the clueless ability of grown men firing paint at each other for entertainment I guess.

Second the water separator cracking. Again not surprised when you look at the weight "hanging" off that separator
and the induced vibration that causes. If the original fittings were a 1/4 Male run Tee in what looks like stainless then the seperator will crack. If you have replaced this with what now looks like a Brass 1/4 street elbow then in due time the brass threaded portion of the fitting will shear off leaving the thread "tail" stuck in the separator when the rest of the assembly falls off.
A small "easy out" tool will be needed soon to remove the remaining thread IMHO

Third I see you have removed the Mil spec Rix air intake filter (no doubt due to its high cost) but it was a polyester
micronic filter assembly. Now what is being used is a cheap rubber edged paper pleated element inside a tin can
The flow rate is now substantially lower and a bigger area filter element should have been considered IMHO to compensate
The flow restiction or pulsation dampening when using paper pleatings is much much greater than with polyster
hence the cheap option is to use a much bigger filter area and dont believe the data given for compressors by the filter sales guy.

I note from the 2nd photo down that the third stage cooling coil is a 3/16" stainless coil this shows the compressor is either an up to date current model SA-3 or a later replacement or upgrade has been done.
The original SA-3's used a copper coil for the 3rd stage coil.

The 3rd stage heads are no shown in the photos and should also be made of stainless as with the 2nd stage. They also should be fitted with a small 1/8 NPT blanking plug positioned centre back.
The earlier versions in stainless didnt have the plug while even earlier versions the 2nd and 3rd stage heads were made of aluminium.

On the 1st photo the DOL starter would have been mouted directly on the compressor with a nickle plated bracket

Of the Olmeva filter contraption I guess it was free but beggers the question why bother with activated carbon its not like your going to need it on a SA-3

Good call on scrapping those (after thought) auto dumps, chances are they were blocked up already.

Interesting that you have busted two 3rd stage pistons you checked the BPR is working OK and you have two opposing counter weights on the crankshaft the correct way around? Also you dont tell us your typical working pressure and run times.
The original piston was made from brass but alternatives are available in both nickle and phosphor bronze for high pressure gas applications.

Enclosed three photos below showing:
The current SA-3 standard build spec.
The custom 3rd stage gas piston variants
The breathing air filtration system arrangement for the SA-3

Its kept clean and simple in design, costs reduced by using brass fittings than stainless with all the additional add on contraptions fitted well off that separator tower fitting.

Oh and Joy to you both LOL Iain

 

[SurfLung]

Well, I posted to this forum because I wasn't getting feedback from other forums so, I can't complain if I get feedback that's a little negative. You make some good points Iain but there are some areas where you've made assumptions that might be wrong. So, I'll try and clear those up first, to get our discussion started on the right foot...

1. My Motor - It's an aftermarket 3 HP that runs at 3450 RPM. I have always assumed a previous owner must have converted my RIX from a gas engine powered unit. It has no bracket for the switch on the frame and the Air Intake filter was a DIY conversion from (probably) an intake hose set up.

2. My Replacement Air Intake Filter - It's a Solberg compressor filter for compressors with up to 8 SCFM flow rate and the filter media is Solberg #07 Polyester 25 Micron (paper is 2 micron). Filter media data is at Solberg 07 Air Intake Replacement Filter | eCompressedAir
The hardware for it is at Solberg FS-07-038 Air Inlet Filter Silencer, Mine's the 1/4" version
- I don't know about the MilSpec status of the intake filter that came on my RIX. When I unscrewed it and looked up under the bottom, I saw a brass fitting that had been epoxied into place and I assumed the whole thing was a garden variety air filter like what goes on a lawnmower or something.
3. The Cracked Separator - I looked through my old emails and found that the crack was discovered shortly after I got the RIX in 2014. It might be why the previous owner sold it. It was cracked at the in-port (not the exit port). I was told by somebody who knows more about compressors than I do that the rapid pressure drop from the auto drain system might have embrittled the metal in the separator. We bypassed that separator and connected directly to the first tube moisture separator on my filter array to fill tanks for about a year. Later on I replaced it to restore my RIX to it's original configuration.
4. Broken 3rd Stage Piston - I only broke one (not two). And it was just in the past 3-4 months. I do believe its my fault but not for the reasons you think. I think it was due to my re-ring job last year on the 1st stage. I believe the ring got gummed up and stuck in the compressed position. So it was seriously diminishing the speed of pressure up and increased the hammering on the 3rd stage piston. Or, maybe I didn't remember to close the drains before powering up and got some serious hammering there. You can bet I'm VERY careful about that now.
5. The Olmeva Contraption - As explained above, this has turned out to be quite handy as I was able to use its moisture separator when my RIX separator cracked. But you ask why I bother with Hopcalite and Activated charcoal filtering... I would say it's BECAUSE I CAN. The two 13X Sieve tubes are more than enough moisture filtration as evidenced by the blue test strips. And since I run the compressor in my garage in the Summer, the Hopcalite and Charcoal just give added protection whether I need it or not.
6. Piston Heads - My 3rd stage is stainless. I believe the other two are anodized aluminum. There's no blanking plug in the middle. To get at the O-Rings and Reed valves, I had to make up a simple PULLER tool. The inside centers are threaded and a puller can be made from a screw, a nut, and some washers.
7. Back Pressure Regulator - Just to be sure this was sealing properly, I bought a re-build kit a year or so ago. Sure enough the insides were seriously corroded. I replaced them, tested, and adjusted it for proper function. I have tried using it at 2000 psi but back it down to 1500 psi per the RIX manual after visiting with Eric at RIX.
8. Working Pressure/Run Times - Until this year, I have been filling tanks up to 3,300 psi at a rate of 2-2.5 cfm. Sometimes coming back from a trip, I might fill 5 sets of Twin 50s and Twin 38s, and 5-10 singles in one fill session. But that's not typical. Usually I was filling 1-3 Aluminum 80s to 3000 psi.
9. My Plumbing Issues - I can tell you the stuff hanging out there vibrates a heck of a lot less since I moved the gauge back to where you see it now! Until I read your comments I was kind of proud of how I have it set up right now. I can see immediately if pressure isn't coming up as fast as it should. And, I can drain the condensation out of the BPR.
- But you make some very good points on possible vibration damage. I'm already thinking about better ways to re-do my plumbing. And your photos of a showroom new RIX SA3-E are beautiful. But you haven't got it hooked up to anything... Not even a BPR to protect the 3rd stage piston. I'd appreciate whatever you might suggest to improve my plumbing.

 

[iain/hsm]

Well, I posted to this forum because I wasn't getting feedback from other forums so, I can't complain if I get feedback that's a little negative.

The one thing you will get here is plenty of feedback as much as you want or need on any question about the subject topic. Dont worry about negative comments your breathing air quality is much too important and the primary objective. Reliability and Maintainability are the two key aspects for SA-3 and SA-6 compressor owners and builders.

You make some good points Iain but there are some areas where you've made assumptions that might be wrong. So, I'll try and clear those up first, to get our discussion started on the right foot...

1. My Motor - It's an aftermarket 3 HP that runs at 3450 RPM. I have always assumed a previous owner must have converted my RIX from a gas engine powered unit. It has no bracket for the switch on the frame and the Air Intake filter was a DIY conversion from (probably) an intake hose set up.

Yes I see that but with second hand compressors you always need to make assumptions as to the quality (or not) of workmanship and service details from any/all previous owner/s. Another issue lately on the forum we have had a number of folk roll up ask questions on the compressor they have, only to use the information as a sales blurb on their Ebay sales description. But on this backwater section of the forum we all try as best we can to help.

A good way to asses if its had a petrol/gas engine is to check underneath the baseplate for bolt crimp marks on the paint slots where the Honda GX120 would have been mounted.

2. My Replacement Air Intake Filter - It's a Solberg compressor filter for compressors with up to 8 SCFM flow rate and the filter media is Solberg #07 Polyester 25 Micron (paper is 2 micron). Filter media data is at Solberg 07 Air Intake Replacement Filter | eCompressedAir
The hardware for it is at Solberg FS-07-038 Air Inlet Filter Silencer, Mine's the 1/4" version
- I don't know about the MilSpec status of the intake filter that came on my RIX. When I unscrewed it and looked up under the bottom, I saw a brass fitting that had been epoxied into place and I assumed the whole thing was a garden variety air filter like what goes on a lawnmower or something.

You are good with the polyester element from Solburg. However the next size up Tin can is a better match for 3 SCFM but needs the addition of a female to male Pipe Thread Reducer PTR fitting as you normally use the next size up Solburg diameter tin can but critically also with the larger thread option as well. 3/4" from memory, I can check

3. The Cracked Separator - I looked through my old emails and found that the crack was discovered shortly after I got the RIX in 2014. It might be why the previous owner sold it. It was cracked at the in-port (not the exit port). I was told by somebody who knows more about compressors than I do that the rapid pressure drop from the auto drain system might have embrittled the metal in the separator. We bypassed that separator and connected directly to the first tube moisture separator on my filter array to fill tanks for about a year. Later on I replaced it to restore my RIX to it's original configuration.

Cant see metal embrittlement with the specific T6 alloy used on the separators unless it was pumping Hydrogen and I cant see anyone doing that either. I would call that comment out. The SA separators are batch hydro tested to 8000 psi 10 or 20 at a time. The most common problem is folk over turning the male branch tee to get correct positioning. They get it up vertical find a leak so jack it around another half turn so much so that using a stainless threaded fitting and the taper busts out the wall. With the brass fitting most folk I see strip the thread than the filter wall.
Hence my comment on investing on an "easy out" especially if you continue having that "Hanging Garden of Babylon" hanging off that poor separator tower LOL

4. Broken 3rd Stage Piston - I only broke one (not two). And it was just in the past 3-4 months. I do believe its my fault but not for the reasons you think. I think it was due to my re-ring job last year on the 1st stage. I believe the ring got gummed up and stuck in the compressed position. So it was seriously diminishing the speed of pressure up and increased the hammering on the 3rd stage piston. Or, maybe I didn't remember to close the drains before powering up and got some serious hammering there. You can bet I'm VERY careful about that now.

Busting a piston really sucks glad it was only one lets hope it wasnt wishful thinking on my part.
We need to come back to this point in the future I'm not that happy with the current piston material there is a school of thought that argues if it was made stronger then it could rattle around all day without a BPR fitted but there is a fine balance with that option and the effect it would have on the piston liner material.
We will discuss this in much greater detail later in the year.

5. The Olmeva Contraption - As explained above, this has turned out to be quite handy as I was able to use its moisture separator when my RIX separator cracked. But you ask why I bother with Hopcalite and Activated charcoal filtering... I would say it's BECAUSE I CAN. The two 13X Sieve tubes are more than enough moisture filtration as evidenced by the blue test strips. And since I run the compressor in my garage in the Summer, the Hopcalite and Charcoal just give added protection whether I need it or not.

I take your point its just I'm not a great advocate for using activated charcoal or carbon with the SA design. Again its a long and complicated issue any time we have approached it someone pipes up about their Bauer or Coltri and we go off on some wild goose chase tangent.

6. Piston Heads - My 3rd stage is stainless. I believe the other two are anodized aluminum. There's no blanking plug in the middle. To get at the O-Rings and Reed valves, I had to make up a simple PULLER tool. The inside centers are threaded and a puller can be made from a screw, a nut, and some washers.

Ok you have the earlier version of the newer build spec. I like it, its clean and tidy and pulling the valves is no big deal
But you need a special tool and one of the major design brief instructions was to be able to service the compressot " In the Field" with no special tools hence the cap that was fitted so you can now push it out with a stick I guess LOL

7. Back Pressure Regulator - Just to be sure this was sealing properly, I bought a re-build kit a year or so ago. Sure enough the insides were seriously corroded. I replaced them, tested, and adjusted it for proper function. I have tried using it at 2000 psi but back it down to 1500 psi per the RIX manual after visiting with Eric at RIX.

I know Eric, (for the last 30 years) LOL what I think would be helpful here is to give you some of the design thinking and background why he told you 1500psi Again for bravity maybe better doing this also later. 1500 psi is OK but we have another topic brewing on the SA-6 at low RPM and small motors you should tag along with as it applies to both SA-3 and SA-6 and optimum BPR setting options will be discussed.

8. Working Pressure/Run Times - Until this year, I have been filling tanks up to 3,300 psi at a rate of 2-2.5 cfm. Sometimes coming back from a trip, I might fill 5 sets of Twin 50s and Twin 38s, and 5-10 singles in one fill session. But that's not typical. Usually I was filling 1-3 Aluminum 80s to 3000 psi.

You pretty much described the ideal design loading for the SA-3 and the optimum flow rate 2-2.5 cfm
I will put some design loading figures based on this info up later in a week or two .

9. My Plumbing Issues - I can tell you the stuff hanging out there vibrates a heck of a lot less since I moved the gauge back to where you see it now! Until I read your comments I was kind of proud of how I have it set up right now. I can see immediately if pressure isn't coming up as fast as it should. And, I can drain the condensation out of the BPR.
- But you make some very good points on possible vibration damage. I'm already thinking about better ways to re-do my plumbing. And your photos of a showroom new RIX SA3-E are beautiful. But you haven't got it hooked up to anything... Not even a BPR to protect the 3rd stage piston. I'd appreciate whatever you might suggest to improve my plumbing.

Sorry about that being a Scot by birth I have few social skills in tact and deplomacy. But we are a well meaning lot if for our gallows humor. So at least on the compressor forum you will have certainty. Life's last and kindest gift I guess. LOL Iain

 

[iain/hsm]

And your photos of a showroom new RIX SA3-E are beautiful. But you haven't got it hooked up to anything... Not even a BPR to protect the 3rd stage piston. I'd appreciate whatever you might suggest to improve my plumbing.

Oh yes I omitted the filter photo.
Pretty much all you need parts wise but located off the frame and with a long enough whip you can wall mount.
Option two fitted with a handle for portability and keeps the SA-3 at a liftable weight although an aluminium tubular frame would be a better lighter option but much more expensive.
Option 3 is you can bolt the filter base channel direct to the SA-3 baseplate but you loose pretty much any portability.

In Europe we have to have a filter fitted by law if its a breathing air compressor in order to achieve the breathing air standard of EN 12021 only if its HP compressed air can we omit it.
Also note the filter is much shorter than your standard 18 inch towers at from memory 300mm a tad shorter than 12 inches. Again there is a design reason for this.

Its set up is non return valve, filter drain wet side (dry side also a discussable topic )
Filter shell with a stainless steel repack cartrige pack. On the outlet discharge side
you have a 10/20/30 relitive humidity water vapour indicator, Back pressure regulator non return valve and pressure gauge cylinder side (Again with options for BPR setting side )
Likewise you can orientate the plumbing vertical for a shorter foot print

 

[SurfLung]

FYI - The Solberg intake filter cans are the same size whether you order the large or the small... I know because I mistakenly ordered the large one first. It required an adaptor and kept vibrating loose. The smaller 1/4" model fits directly into the RIX SA3 port. The cans are the same size and take the same #07 filter. I think its the size if the intake hole in the compressor that dictates the flow rate capacity of these filters.

Here's a Topic I've been interested in:

There are two "Erics" at RIX. Eric Zenius was who I would speak to 4 years ago. But more recently I spoke with and emailed back and forth with Eric Connally. He was very knowledgable and helpful with my broken cylinder replacement. Our conversation evolved a bit and that's where I learned some about the Back Pressure Setting of 1500 psi that the RIX manual specifies.

I had increased my BPR setting to 1800 psi and then 2000 psi because I read about the higher pressure squeezing 99% of the water out of the air. But I was getting moisture to drain out of the BPR that I thought would have been squeezed out in the moisture separators.

When I asked Eric about this, he said the purpose of the BPR is to increase pressure fast so that the floating 3rd stage piston settles on the piston rod right away. It's not for knocking out moisture. "1500 psi is sufficient for the piston".

Furthermore, the moisture coming out of my BPR is due to the high pressure air expanding after the BPR releases it... Which causes moisture to condense. And the amount of condensation is directly affected by the pressure the BPR is set at. The higher you set it, the more condensation. My filter array has its own PMV set at 1500... As for knocking out moisture I still don't understand the difference between a BPR and a PMV.

Okay, now lets talk about work load. If I set my BPR for 2000 psi, it will always be working at 2,000 psi and higher pressures when I fill a typical AL80. But if I set the BPR for 1500 psi, it will be working at the lower pressure for half the time of the same fill. That's less of a work load. And especially when I'm filling my vintage Twin38s to 1800 psi... Keeping the workload down for my poor little compressor.

 

[tbone1004]

@SurfLung BPR and PMV are the same thing. They won't let gas thru until a certain pressure is achieved.

@iain/hsm can correct me on this, but this is my school of thought on this. You want one IMO as close as possible to the outlet of the final stage so the piston seats quickly where the pressure really doesn't matter. In terms of seating the valve, as long as the pressure is set to somewhere higher than the pressure required to seat the piston, the pressure is irrelevant. You want to be careful in terms of how close you put it because you want moisture to come out somewhere between the two, but that's why you don't want to oversize the moisture separator since it will be that many more revolutions before it seats. Volume is everything. It's a fun balance.
A second one should go after the filter assembly, and that pressure should be set to whatever pressure you feel the filters need to work properly. The higher the pressure, the more the compressor has to work. IMO that pressure needs to be the "balance" pressure of the compressor. Up to a certain pressure, the compressor is out of balance, and over that pressure it is out of balance in the other direction.
I don't know what that pressure is for the Rix, but it would be ideal if it was around 4000psi for compressors hooked up to bank bottles, and 3000psi for compressors filling tanks directly. This puts the compressor in balance for all but the final high pressure run. With banks, that is 4000 up to 4500psi, and for tanks that's 3000 up to 3300-3800psi depending on tanks. The compressor has to work harder the whole time in terms of work required since it is compressing against a higher pressure, but the system as a whole is stable during that whole time instead of having big pressure fluctuations.

Sounds like 1500psi is the ideal BPR for the piston to seat which is good, and hopefully Iain can outline what the "balance" pressure is when the compressor is truly in balance, and whatever that pressure is, is what the filter PMV should be set to.

 

[2airishuman]

Hi SurfLung. Good to see someone else making air in the land of 10,000 lakes.

It's a long run at 2-3 cfm but beats driving across the state to get fills.

I have 4 bank bottles and am going to have to take them in to Airgas to be revalved soon. The packing and seats are shot and no one will sell me valve parts. I'll probably have them hydro'd while they are there since they're halfway through the hydro period already and it's such a hassle to take them in.