Rix SA-6 rebuild?

[1bubbleoff]

Ok all-

Have a newer SA-6. On the boat...Powered by Honda gas...

While filling tanks this am...very sudden, VERY loud, knocking . Shut it down within 5-10 seconds. Sounded definitely mec hanical in nature. Reminded me of a rod knock.

I have disconnected duel belts from engine to compressor.... Honda runs fine, and quiet. Obviously the compressor side of the setup.
I have spun the pulley wheel, and everything turns freely, very smooth, very easy... ( filter tower and both moisture seperators in open ( drain) position.

2nd Stage is definitely loose... as in...I assume not building compression. I can hear and feel the escape when I turn by hand. Did a smoke check on back side of all three stages...2nd stage is definitely escaping air on back side imo. ( Wobble bearing/fan side).

Can hear an "air squeak" on front side of 2nd stage with each revolution...

I have definite qualms about attempting to do a stage rebuild. I am on a boat, no workshop, minimal tools, and limited knowledge in regards to compressor builds.

I am located near Wilmington NC. Anyone who knows these things, and might help? I am willing to dismount the compressor side and drive it if it gets me back up. This is a dive boat, and quite frankly..I am pretty much out of business without the SA 6.. it's the heart of my operation!!

Thanks in advance,

bubs


Note-

Serial # 10250, which makes this a newer model SA-6B

 

[rob.mwpropane]

I won't pretend to be an expert, but I own one.

Did you have any blow by leading up to this point? (Would hear air escaping when you shut it down). Interstage gauges installed on 1st / 2nd stages? I attached a pic where mine are. Have you times it at all to make sure you're still making ~ 5-5.5cfm?

It sounds like you need a rebuild of at least 2nd stage piston... I'm getting ready to do the same thing. Might as well rebuild the 1st while you're at it.

@iain/hsm has a good write up on turning the bearings so they aren't being used in the same spot. I'm paraphrasing but he said you can get a lot more life out of the expensive 3rd stage piston if you redo the rings (at least the expansion / rider rings) in the 1st and 2nd stage.

Gosh, I wish my Yanmar diesel ran "fine and quiet". It's the smallest loudest thing I think I've ever heard, lol.

 

[rob.mwpropane]

Sorry.. forgot the pic. I periodically check these... at least I would hope that I would catch something happening before it actually went to ****.

 

[PrffsrE]

Quite an extensive (recent) talk on the topic including some great videos from @iain/hsm here:

Rix SA-6 Parts

Good day all. In reference to this post by lain I'd like to purchase the expansion o rings. I was wondering if anyone has done this and if you would recommend replacing the rider rings or the compression rings while "in there"? Is there anywhere I can purchase just a few o rings? I am under the...

scubaboard.com

It is VERY hard to diagnose from a short text document but..... (You gotta love the 'Butt")
It sounds like you lost the compression ring on the second stage. The third stage is an free floating piston meaning it is not connected to the rod and when you do not have enough pressure from the second stage to drive it down as fast as the rod the rod returns and slams into the piston! Sounds really bad! New rings all the way around and Bob's your uncle! (I always wanted to say that! LOL)

Seriously read the thread!

 

[1bubbleoff]

Have pulled all three pistons...2nd stage worn compression ring....3rd stage worn rings as well.

Have ordered all rings and o rings for all 3 stages...gonna just rebuild em all. Bore all look really good.

Total price for all o rings, compression rings rider rings and breaker rings 3 rd stage... $330 bucks.

 

[rob.mwpropane]

Have pulled all three pistons...2nd stage worn compression ring....3rd stage worn rings as well.

Have ordered all rings and o rings for all 3 stages...gonna just rebuild em all. Bore all look really good.

Total price for all o rings, compression rings rider rings and breaker rings 3 rd stage... $330 bucks.

Any pictures what you found?

 

[1bubbleoff]

Working on it Rob...

 

[rob.mwpropane]

So @1bubbleoff was nice enough to send me his pictures and said it was ok to post. Here is what he is dealing with.

Naturally I am interested because I have the same pump and it gives me an idea what I'm in for in the future, but I think it's good for anyone later down the road that might need these.

 

[1bubbleoff]

So Rob...as you can see, I pulled all 3 stages...

Big concern is the 2nd stage.... it's obvious that the compression ring was (is) an issue....if I were to hazard a guess...the 2nd was rebuilt at some point before I got the compressor, and I suspect that the ring got pinched.
In inspecting the cylinder bore ( eyeball and strong light) I am of the opinion that it's a case of " no harm no foul" so to speak... I need to rebuild the piston, but the bore looks to be in exceedingly good condition. No scrapes, no streaks, no concentricity issues....nothing tells me that the bore is out of round or has any kind of problem. I think that a piston rebuild, reinstall and away we go.

Given that I have her cracked open, I am doing full rebuild on all 3 stages... just pistons, and reusing the 3rd stage piston proper. Not into the heads, if all is well on return to service I will rebuild heads in the near future... just not now.

Bubs

 

[Golan68]

since the heads valves are relativeliy easy to work on I would clean them and replace seals too.