Tore My Rix SA-6B Apart

[iain/hsm]

An english man that doesn't drink.....

I don't drink tap water either LOL but I have been known to drink the water condensate drain contents from the SA-6 separator towers. Got it tested once turns out it was just pure distilled water.
I therefore suggested that you could pour it down the drains and got into a lot of trouble with the Health and Safety folk Go figure

Upshot was no consideration was given to the advantages of an oil less oil free breathing air compressor and that our request that an oil free breathing air compressor does not require an oil analysis to comply with our breathing air standard BS EN 12021 was also rejected.
Further more as the oil testing part of the test is the greater of the total air testing cost we were lumbered with a test we don't need or require. The advantage you can claim is the filtration lasts 4 times longer.
Iain

 

[iain/hsm]

Rix said these grooves should measure .076-.078

The pressure breaker rings pulled from my machine all measured .069 when pulled off.

The new pressure breaker rings all measured .0715-.072 and then one measured .075. Rix told me that the spec for the PB rings were between .070-.073

View attachment 830995

I'm having some sent over to measure ourselves and to compare with our stock in UK

Also don't stretch the 0-ring onto the brass tube like that you will never get the compression rings on if you do. Quite the reverse with the rider rings on first just flip the 0-ring on by hand starting at each end and meeting at the middle. Yeah yeah I can see another YouTube performance if you carry on like that
Iain

 

[iain/hsm]

Well, the compression ring should be applying significant pressure against the cylinder wall to provide a seal ,and the oring between the piston and compression ring seals that gap in addition to providing radial expansion of the ring.

My off-the-cuff thought is that rider ring fundamentally functions to keep the piston from banging around when the compression ring wears or fails. It may also aid in keeping things aligned.

Pretty yes, but I'll probably spend a buttload of hours and more $ than the factory part creating my shroud SYSTEM.

That post is spot on. Thank you

The only addition is the pressure breaker ring and consideration of pressure on the reverse travel of the piston.
In a standard air compressor the compression ratio is low as is the pressure dynamic. However in our high pressure scuba compressors the gas sealing dynamic requires three considerations. First the rider ring you suggested to avoid metal to metal contact of the piston with the liner during compression to extend the liner life. Second the compression ring or rings to effect a gas seal as you suggested on the compression stroke only and finally the pressure breaker ring to protect the compression ring or rings following from the dynamic pressure change created from the piston going from top dead centre (full stroke and highest pressure ) back to bottom dead centre and static pressure

This is calculated at the varying degrees of crank angle achieved during a singe stoke of the compressor. For example at Top dead centre the crank angle is zero and the discharge pressure is greatest as is the discharge adiabatic temperature while at 40 degrees crank angle all that pressure has gone and you reach suction pressure. The suction pressure continues from 40 degrees to 180 degrees and bottom dead centre until the up stoke approaches starting at 180 degrees BDC back to the upstroke and increasing in pressure and temperature until back at TDC. The static pressure load is from 40 to 180 degrees while the dynamic pressure load is on the upstroke is from say 180 to 300 degrees until 360 degrees is reached and is back down to repeat. Iain

 

[rob.mwpropane]

Alright, here's 2 3rd stage pistons next to each other. The one on the left is brand new, the one on the right is my old piston. I don't really see any difference to the naked eye. I need to take some measurements, hoping to get some later today.

I also got a new pair of pressure breaker rings to measure as well and compare them to the other new set.

 

[iain/hsm]

It was this photo you posted earlier that threw me. As the side holes nearest the loose Pressure Breaker ring definitely looked smaller in your photo Iain

 

[rob.mwpropane]

It was this photo you posted earlier that threw me. As the side holes nearest the loose Pressure Breaker ring definitely looked smaller in your photo Iain

View attachment 831877

But they look ok in the next set, yeah?

I can't see anything different with the naked eye.

 

[rob.mwpropane]

@iain/hsm you had mentioned listing the different head bolt sizes to switch them out to stainless. I tried to match them up at the hardware store, but they didn't carry stainless. I guess I'll just order them online.

 

[Gone for diving]

Just my opinion...
But I am not so sure I would use ss bolts in that kind of application....
Unless the bolts are not being overly stressed, then it should be fine.

If you do. I would run a die over the new SS bolts. It tends to be a smoother thread. And less chance of galling....

 

[rob.mwpropane]

Just my opinion...
But I am not so sure I would use ss bolts in that kind of application....
Unless the bolts are not being overly stressed, then it should be fine.

If you do. I would run a die over the new SS bolts. It tends to be a smoother thread. And less chance of galling....

My heads (vs those of older models) are stainless. I thought the fear with stainless bolts was if they were dissimilar metals?

 

[Gone for diving]

Don't think you really need to worry about dissimilar metals, in this case. It's not in salt water....

Outboards they use ss fasteners in aluminum....