tbone1004
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Re: Fill Rate Challenge

Thu Sep 27, 2018 8:18 am

what were ambient conditions? Remember compressors get quite a bit slower when the ambient conditions are hot and or humid

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SurfLung
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Re: Fill Rate Challenge

Wed Jan 16, 2019 11:24 am

Clogged Moisture Drains and Fill Rate...
- All of last season I was noticing a significant amount of moisture coming out of the drain I installed in the bottom of my Back Pressure Regulator. Remember that the original RIX set up was to fill tanks directly off the BPR. Also remember that a BPR or PMV is supposed to force almost all of the moisture OUT of the air and into your condensation towers. Well, the drain in my BPR is spewing a wet mist at every 10 minute drain interval.
- The last couple of evenings I've been filling tanks and noticed it was going kind of slow. I did a fill rate test and it came out to 2.2 cfm... My RIX has been filling as high as 2.7 cfm and so I got out the manual and looked at all of the trouble shooting steps. But I found no leaks, no belt slipping... All of the easy stuff to check, I did and found no solution.
- Then I noticed that the drains on my moisture towers seemed to be under pressurized. Usually I open them and get a blast of water and air and then just air. NOW, I'm getting a slow dribble out of the 2nd stage tower drain and a high pressure spit out of the 3rd stage tower drain. Neither of them continues to blow after the initial release.
- Tonight I'm going to take the drain valves off and see if there's anything clogging them. If not, I'll try installing some different drain valves. At the least, I hope to reduce the amount of moisture that makes it into the BPR. But also, I hope to get my fill rate back up where it should be.
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The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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antique diver
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Re: Fill Rate Challenge

Wed Jan 16, 2019 11:40 am

Check all your hoses for leaks at crimps, JIC swivels and all along the length. Those can have small leaks that are easily missed, making virtually no audible sound. Modern hoses are somewhat notorious for seeping air, especially in cold weather, and 1 cfm would hardly be noticed diffusing out of the perforated outer cover unless carefully soaped and observed. See email.
The older I get the better I was.

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SurfLung
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Re: Fill Rate Challenge

Mon Jan 28, 2019 11:40 am

Found a Couple of Possibilities...
- I pressurized everything to 2000 psi and turned off the compressor to look for leaks in silence. All three gauges stayed solid on 2000 psi for about a minute. Then, I began to hear a growing hiss and traced it to the final over pressure valve... Which is not supposed to let go until 3600 psi. So MAYBE this OPV is leaking a little. Bill sent me instructions for rebuilding it with a new O-ring.
- I THOUGHT I had checked every connection, all seals, etc. for leaks with soapy water and found none. But with the compressor off, and no fan running to blow the soap away, I saw a soap bubble growing off one of the filter tubes. Opened it up and found a scratch that's right on the surface that seals the O-ring. It probably happened when I was trying to remove the Lawrence filter with a filter pic tool and slipped... Had to be awhile back and still sealed okay until recently. Bill says the old O-ring maybe got hard and will no longer seal over the scratch. So, we'll try a new O-ring there.

Before fixing anything, I did a fill rate test from 0-3000 on an AL80 and it took 44 minutes... Which was 1.8 cfm. Last year at this time I did the same fill rate test and got 2.6 cfm using the same method. So, I have a baseline to compare with when these two weak points are fixed.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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SurfLung
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Re: Fill Rate Challenge

Wed Jan 30, 2019 12:24 pm

- I was able to get the filter tube to seal up fine with a new O-Ring. Did the fill rate test again and got pretty much the same result. It probably helped some... No leaks are good... But it wasn't the main cause.
- Last night I did a "Glove Test"... This is where you put a rubber glove over the Over Pressure Valves and seal it with a zip tie. If there's a leak there, its hard to see or hear while the compressor is running but you can see the rubber glove inflating if the OPV valves are leaking... One of AntiqueDiver Bill's many tricks of the trade.
- I pumped the compressor up to 3000 psi and watched but no rubber glove inflation.
- I have gauges on each pressure zone so I turned off the compressor and watched the needles. All held solid on 3000 psi... So, no leaks.
- There are two last things on the RIX Trouble Shooting list: One is a faulty valve function in the first stage. The other is too much piston clearance in the first stage. I can check both of these at once if I take the 1st stage cylinder head off and service the O-rings and reed valves... So, that's the next step.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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captain
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Re: Fill Rate Challenge

Thu Jan 31, 2019 11:10 am

As as you shut it down listen at the intake for any air leaking back out. It does appear it may be a stage outlet valve that is leaking or piston ring.
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SurfLung
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Re: Fill Rate Challenge

Thu Jan 31, 2019 6:15 pm

Thanks Tom. I checked the 1st stage piston clearance and that was fine. But the 1st stage inlet and outlet reed valves were dirty. I took them apart, cleaned and re-assembled with a new O-Ring. Put it all together again and filled an AL80 tank... NO DIFFERENCE. Still only 1.8 cfm. I've had this compressor pu,ping as high as 2.6-2.7 cfm.
- When I pressurize everything and then turn it off, there is no sound... It seems to be solid and leak free... External leaks anyway. I agree the next step should be to clean the other two cylinder heads and replace O-Rings. Maybe there's some inefficient sluffing of high pressure back and forth into low pressure cylinders.
- It seems like it out to be a pretty major leak which should be easily detectable. Last year, I had a leak like this and couldn't find it. When I did finally find it, it was a bronze elbow fixture with an invisible hairline crack in the threads. I still can't see it visually. It was camouflaged in the puff-puff from the air filter intake. But, when I turned the airfilter around, it was easy to see a BUNCH of air leaking from that elbow crack.
- I was thinking last night that I wished I could run the whole thing submerged to I could see the leaking bubbles coming out. :)
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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captain
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Re: Fill Rate Challenge

Thu Jan 31, 2019 11:36 pm

If possible you could hook up an air supply to the compressor intake and pressure up the whole unit to 150 psi to look for external leaks.
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SurfLung
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Re: Fill Rate Challenge

Mon Feb 04, 2019 10:42 am

Rebuilding the heads... Again.
- Over the weekend I took all three heads apart and discovered severely cooked O-rings in the 3rd stage and extruded O-rings in the 2nd stage. The first stage was dirty but the O-ring was like new. In my enthusiasm to re-build these the first time around, I used hardware variety O-rings when I should have used 90 durometer Viton rings... Those are tougher and more high temperature resistant. Anyway I re-built them again and then did the tank fill test again. No change... Still only 1.86 cfm. The next step is to check the piston rings... These were ordered direct from the factory on the last re-ring so nothing substandard parts-wise.
- But, since every thing I've tried has resulted in no improvement and no change, I began to wonder if maybe the compressor is running fine and I'm doing something different in my fill rate test. So, I went back to my compressor journal and looked up the original test where I got 2.7 cfm. It was a steel 72 filled from 0-2200 psi. I repeated that test though... and still got the 1.86 cfm fill rate. So, whatever the cause turns out to be, it hasn't changed in all of my efforts to find it or cure it by trial and error.
- Actually, this isn't too far off from the way this coimpressor was behaving before I did the first re-build. That time, I re-built the heads one by one and got no improvement. Then I re-ringed the pistons starting with the HP 3rd stage, then the 2nd, and finally the LP 1st... And it was the 1st that solved the problem.
- Fortunately, the RIX isn't difficult to work on. If you have the manual it tells you just about everything and how to service it. Except for one thing: Taking apart the 2nd and 3rd stage cylinder heads. The manual says to smack the head against a solid surface like a board and the guts will pop out by inertia. This positively does not work. But I discovered a threaded hole in the middle of the guts. And this works perfectly for making a "puller" with a machine screw, a nut, and appropriate sized washers.
- Pulling the pistons is easy because there is no crank case. This time, I will start with the 1st stage.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

tbone1004
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Re: Fill Rate Challenge

Mon Feb 04, 2019 1:06 pm

when you rip it apart, you may want to look at putting a pressure gauge on each stage of compression since that will help tremendously

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antique diver
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Re: Fill Rate Challenge

Mon Feb 04, 2019 1:27 pm

tbone1004 wrote:
Mon Feb 04, 2019 1:06 pm
when you rip it apart, you may want to look at putting a pressure gauge on each stage of compression since that will help tremendously
Tbone is absolutely right about that. It sure helps diagnose and pinpoint compressor issues.

You should be able to tee into the first and second stage relief valve ports for adding a gauge and still keeping the relief there too. A gauge snubber on those lower stages might be needed to keep the gauge reading steadier and make it last longer too. At least probably helpful on the first stage.
The older I get the better I was.

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SurfLung
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Re: Fill Rate Challenge

Tue Feb 05, 2019 10:52 am

Found It... Fill Rate is Now a True 2.875 cfm...
- Well the good news is I discovered what the problem is, corrected it, and the compressor filled a tank from 0-full at 2.875 cfm... That's the fastest fill rate it has ever achieved for me. Closest to the 3 cfm advertised by RIX... Its a RIX SA3 compressor. Nearly 2.9 cfm!
- The bad news is that the 3rd stage piston is broken at the bottom... There's the bottom rider ring and then the first compression ring... The break is through the first compression ring groove. I think it was being held together by the gummed up compression ring... It came apart in my fingers as I was pulling it out of the cylinder. Anyway, I'm going to have to get a new 3rd stage piston before I run it again.
- How did I run the 2.875 cfm test with a broken piston? Well, I got away with it but shouldn't have. I figured since it is a floating piston, and since the broke-off part has plenty of "Rider Ring" to keep it straight, and since it has already been running this way for what looks like awhile, it should work enough to see if the solution will fix the fill rate. The truth is, with the piston, rings, expanders, and riders all cleaned up, it rattled a bit and I attribute the rattle to the broken floating piston... Banging its parts together.
- Okay so what was the "Fix" - Well, when I pulled the 1st stage piston, I immediately noticed there was no resistance... no friction nor suction. Then I looked at the ring and it was completely compressed into the piston groove and gummy. The ring ends overlapped and actually pinched in the ring groove, holding the ring in the compressed state. Closer examination showed nothing wrong with the rings. It took awhile to free up the overlapped pinch with a razor blade. But I finally coaxed it loose and was able to remove the ring and expander O-ring beneath it. Both were in good shaped but gummed up. So, I cleaned them with warm water and Dawn dishwashing liquid. I snipped a bit of length off the ends so there won't be an overlap to pinch into the ring groove. When the expander and compression rings were re-installed, they were visually expanded beyond the piston diameter. And when I re-installed the piston into the cylinder, I could feel friction and compression properly.
- I experienced and did pretty much the same thing with all three pistons.
- So what caused the "gummed up" condition. Well, the grease used on the turn buckles is a special "low sling" type so as not to get flung around where it shouldn't be. But you can see and feel old grease residue on the bottom of the cylinders, piston rods, thrust bearing springs, etc. I believe this is what gummed up the rings. I'm thinking I should get a tooth brush and some Dawn and hot water to clean up the whole bottom of the compressor.

Lessons Learned:
1. Ring failure doesn't necessarily mean you have to replace the rings. It costs $141 to replace all of the rings so, I'm glad it isn't always necessary. In this case, ALL of the rings were working in good contact after the clean up. Perhaps a good idea to check and service the rings (and heads) 1-2 times a year. Its not all that difficult to do with the RIX.
2. Turn buckle lubrication. You can do a much better job with the piston removed because you can rotate the ball and get fresh grease on all surfaces. AND, you can wipe off the excess before re-installing the piston and thereby reduce grease slinging.
3. I learned how to check for and adjust piston head gap... Didn't need to do it but, learned it while trying to find a solution.
4. I learned to use balloons or rubber gloves to check for leaks on over pressure valves (thanks Bill).

Finishing Up:
- I've got to call RIX today and order a new 3rd stage piston. Its $768 with all new rings installed. Or, $333 for just the piston. GEEZ! I thought the piston was brass but maybe its gold? If they have it on the shelf and can ship 2nd day air, I can have this compressor restored to proper running condition by next weekend. I don't need it that fast but it bothers me when its not running right. - Best Regards, Eben

P.S. - It occurs to me that anyone who has been following all of my trials and tribulations with this RIX SA3 compressor must think, "What a pain in the neck it must be to own a compressor." Or, "That RIX must be a piece of junk." I think I need to comment on that: Remember that this was a well used compressor that I bought awfully cheap. From the start, there were alot of non-standard issues with it that had to be figured out and corrected... By me, an absolute amateur at compressor service. With the help of my friend Bill the Antique Diver and others, I learned the working of this compressor as well as some general things about other compressors. I still don't know everything about this RIX. But I know alot more than I did when I started. AND, I've been filling tanks for 30-40 dives a year for the past 3-4 years that I've owned this compressor!
- It may be that a RIX has to be checked and service more often and in greater detail than I have done it. But the RIX is relatively easy to pull and service the heads and rings once you get the hang of it. Anyway, I have enjoyed filling tanks as well as learning to service my compressor.
- But that doesn't mean EVERY compressor is a pain in the neck. Buy a new one and you won't have to put up with an adventure like mine!
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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antique diver
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Re: Fill Rate Challenge

Tue Feb 05, 2019 11:39 am

You are the official RIX expert! I have never been inside mine, and have learned a lot from your experiences that will be helpful when I do have to make repairs. :D
The older I get the better I was.

tbone1004
Vintage Diver
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First Name: Tom

Re: Fill Rate Challenge

Tue Feb 05, 2019 12:54 pm

Two things you may want to very seriously consider. Getting the CFM that it is rated for is great because it means that you have now sorted out all of the issues with it. What I would HIGHLY recommend doing is slowing it down to 2cfm if you can. Those compressors are NOT designed for longevity *from the engineers that designed them as recently as last month*. They are designed for high fill rates for the military. They run very hot and that is why their service interval is quite short. You said you have the sheaves to run it at half speed and I would very much recommend putting them back on if you can deal with the slower fill rates. It will greatly extend the compressors life.

Second one you may want to do, especially if you slow it down, is remove the fan and replace with an electric fan. This will give you constant air flow over the unit regardless of speed and should quiet it down a bit as well.

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SurfLung
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Re: Fill Rate Challenge

Tue Feb 05, 2019 4:03 pm

tbone1004 wrote:
Tue Feb 05, 2019 12:54 pm
What I would HIGHLY recommend doing is slowing it down to 2cfm if you can.
Tbone, you gotta know I can't do that. Its definitely good advice and I appreciate it, but one of the satisfactions I get out of this little RIX is knowing that I got it running at peak performance. When I am filling a tank and it feels warm from the fast fill... It makes me proud.

BTW - I just got off the phone with "Art" from RIX tech support. He said the gumminess I am experiencing that keeps my rings from expanding is caused by filling tanks in high humidity. The moisture in the air mixes with the teflon from the teflon rings and it gets "gummy". Minnesota in the Summer is hot and humid. The solution is simply and exactly what I did. Clean them up with warm water and Dawn or Simple green. He said to clean the inside of the cylinders with scotch brite green pads and dawn or simple green.
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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