Tore My Rix SA-6B Apart

[iain/hsm]

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....

Good point, I forgot the America fixation for buying nuts and bolts from the cheapest tat suppliers out of China and India bought online or at the nearest shopping "mall" Bolts from supermarkets in buckets.

Take note from now on when I reference nuts and bolts in general I really mean these folk for you lot. Unbrako

https://unbrako.com/images/downloads/engguide.pdf

Catalog & Downloads | Unbrako

unbrako catalog, unbrako catalogue, unbrako engineering guide, fastener guide, case studies about unbrako

unbrako.com

In addition also note the threaded bolt holes on the back of the SA-3 and SA_6 block for the heads have inserted stainless steel helicoils and these folk apply:

HELICOIL® – Thread inserts for metals | Böllhoff

HELICOIL® thread inserts reinforce and repair thread. Discover our product variants for different requirements.

www.boellhoff.com

It is also prudent to use a small amount of even the cheap "Copperslip" from your local supermarket or
if your budget reaches the likes of Swagelok Goop
And if the budget is exceeded and the wife doesn't know try Rocol Anti Seize stainless

Anti-Seize Paste Specifically Designed for Nimonic and Stainless Steel - ANTI-SEIZE Stainless - ROCOL - ROCOL

Nickel-free stainless steel anti-seize, designed for stainless, nimonic and silver-coated fasteners. Ideal for use at high temperatures over long periods.

www.rocol.com

And for those who really want to know it goes by the uninspiring name of Rocol SA-610 Go figure LOL Iain

 

[Gone for diving]

Good point, I forgot the America fixation for buying nuts and bolts from the cheapest tat suppliers out of China and India bought online or at the nearest shopping "mall" Bolts from supermarkets in buckets

I normally get most of my hardware from a nut and bolt supplier....
They should be decent, but one never knows these days.
I am sure the alloy is important.

I was more concerned of the SS work hardening. From repetitive loads.
I have been told SS likes to let go in most inconvenient times.

But have never really experienced it.
But I could be way out to lunch.....

Lube is a forsure.

 

[iain/hsm]

I normally get most of my hardware from a nut and bolt supplier....
They should be decent, but one never knows these days.
I am sure the alloy is important.

I was more concerned of the SS work hardening. From repetitive loads.
I have been told SS likes to let go in most inconvenient times.

But have never really experienced it.
But I could be way out to lunch.....

Lube is a forsure.

To kick off the three head bolts are:

3rd. 5/16-24UNF x 2.250"Socket Head Bolt
2nd. 5/16-24 UNF x 2.50" Socket Head Bolt
1st. 1/4-28 UNF x 2.0" Socket Head Bolt

Each with two (2) bolts per head

The head loads at TDC per head are as follows:
3rd Stage 744.6 lbs (at 3000psi rising) and 1241.89 lbs at 5000 psl
2nd Stage 770.55 lbs
1st Stage 707.26 lbs

And the numbers measured nominal at 5000psi G
I would add if your going to lube the threads lower the torque
10 ft/lbs for the 1st and 15 ft/ lbs for stages two and three
They are all 0-ring sealed like an A clamp yoke or DIN connector don't go mad Iain

 

[rob.mwpropane]

Alright, so just following up with this thread. I went back and forth with Rix and they helped me out. I had to order a few more pieces but everything is finally rolling again. Rix has been nothing but stellar to go back and forth with, really top notch.

I did ask about using only rider / compression rings in lieu of pressure breaker rings and this was the conversation had;

Me:
In talking with someone that works on compressors he said that I could use 2 more 3rd stage piston rings and rider rings in place of the pressure breaker rings (so 6 total)? Is there anyone in your department that can confirm if that's an idea?

He said that's how you're doing it on the new 3rd stage pistons in the newer machines?

Would this prolong or shorten maintenance and is it of any benefit, or is it just sacrificing those instead of using the pressure breaker rings? I honestly don't know what purpose the PB rings have?

Them:
I had to reach out to the engineers. According to them “the pressure breaker faces the highest pressure and throttles the flow of gas, lowering the pressure that the main seals must withstand. Pressure breakers are typically required for differential pressures over 300 psi, i.e. 3rd stage.” They do not recommend replacing the pressure breakers with piston/rider rings, it will definitely shorten the life of the other rings.

Me:
I understand but how come the newer machines only use rider rings / compression rings? They do not have any pressure breaker rings, which is on the 3rd stage and sees more than 300psi?

Them:
We no longer make the SA6, and the newer compressors are made with different materials (and different sizes).

 

[-JD-]

Them:
I had to reach out to the engineers. According to them “the pressure breaker faces the highest pressure and throttles the flow of gas, lowering the pressure that the main seals must withstand. Pressure breakers are typically required for differential pressures over 300 psi, i.e. 3rd stage.” They do not recommend replacing the pressure breakers with piston/rider rings, it will definitely shorten the life of the other rings.

IANACE (I Am Not A Compressor Enginner) but ...

OK, If 2 sets of relatively weaker-sealing pressure breaker rings protects the following 4 sets of strongly-sealing primary compression rings, wouldn't 2 sets of strongly-sealing Comp rings in place of the weakly-sealing PB rings better protect the following 4 sets of Comp rings from seeing pressure? That would suggest lower wear probability in that case.

Now those advance Alternate Comp rings should be seeing the brunt of the pressure initially and it would not be unreasonable that they would wear harder and start to eventually experience blow-by, and you know, act like the PB rings, transferring more pressure to the 4 normal compression rings.

Where I see the possible concern is if the net usable lifetime of the advance Alternate Comp rings, where they are at least acting with the equivalent effect of what the PB rings would, is significantly less than the PB rings.

On the other hand if the PB ring replacements are not available:

• Is running old PB rings likely to lead to a longer life cycle vs. substituted Comp rings?
• If your PB rings are total trash, substitute Comp rings are probably >>>>>>> nothing.

 

[rob.mwpropane]

IANACE (I Am Not A Compressor Enginner) but ...

OK, If 2 sets of relatively weaker-sealing pressure breaker rings protects the following 4 sets of strongly-sealing primary compression rings, wouldn't 2 sets of strongly-sealing Comp rings in place of the weakly-sealing PB rings better protect the following 4 sets of Comp rings from seeing pressure? That would suggest lower wear probability in that case.

Now those advance Alternate Comp rings should be seeing the brunt of the pressure initially and it would not be unreasonable that they would wear harder and start to eventually experience blow-by, and you know, act like the PB rings, transferring more pressure to the 4 normal compression rings.

Where I see the possible concern is if the net usable lifetime of the advance Alternate Comp rings, where they are at least acting with the equivalent effect of what the PB rings would, is significantly less than the PB rings.

On the other hand if the PB ring replacements are not available:

• Is running old PB rings likely to lead to a longer life cycle vs. substituted Comp rings?
• If your PB rings are total trash, substitute Comp rings are probably >>>>>>> nothing.

Yeah... I don't know.

Iain wasn't kidding when he said the left and right don't know what the other is doing. From one side of the pond to the other. I get that they don't recommend the additional rings because it's not how it was built.. but to completely contradict by saying "They do not recommend replacing the pressure breakers with piston/rider rings, it will definitely shorten the life of the other rings."

 

[-JD-]

Yeah... I don't know.

Iain wasn't kidding when he said the left and right don't know what the other is doing. From one side of the pond to the other. I get that they don't recommend the additional rings because it's not how it was built.. but to completely contradict by saying "They do not recommend replacing the pressure breakers with piston/rider rings, it will definitely shorten the life of the other rings."

Remember, he didn't say it was BETTER. In his opinion roughly the same. It could be only 249 hours instead of 251 if you don't use the PBs

No not really the advised service life is still around 250 hours either way hence the suggestion if you don't have the PB ring (pressure breaker ring ) on hand just use 2 additional comp rings to do the same job. You could also re use both the PB Rings but the $30 saving does have risks if the life is not doubled. And with no real labour cost saved.

Some more modern designs and another models have done away with the PB ring and additional compression rings have been used (I may show these later as examples)

Technically its not an upgrade its just a field application to get you up and running
Not withstanding if (and its a big if) the SA-3 and SA-6 were to be re introduced would you go with a compete piston re design or stick with the 1000's of rings already still available and cheap . Computer minimum stock levels permitting that is. As for the pint money forget it I don't drink besides you couldn't afford my rates LOL Iain

 

[1bubbleoff]

My take on this...and keep in mind I'm by no means an engineer...is that " No, don't substitute CR's for the PB's" ....but if you HAD no other options...as in..." Compressors dead without new PBR's..." you COULD get away with substituting CR's for PB rings as a last resort, without really compromising the 3rd stage.

Remember..these things were DESIGNED to be maintained shipboard or on a beach in the jungle by 17 year old kid's who's tool knowledge is basically.., " what's a wrench"????? ( spanner for the rest of the english speaking world)

I am completely gobsmacked by the fact that you can literally rebuild this entire compressor with a few hex wrenches and a 10" cresent wrench if you have a screwdriver...

Maybe Rob...you should volunteer your rig as a test bench...go with the "substitute" ring build and log the eventual outcome?...Just a thought.

Kurt

 

[Gone for diving]

For what it's worth. In hydraulic cyl.
Some have a buffer seal before the main seal...
So main seal doesn't see a spike.
It still will see full pressure.

 

[rob.mwpropane]

For what it's worth. In hydraulic cyl.
Some have a buffer seal before the main seal...
So main seal doesn't see a spike.
It still will see full pressure.

From my primitive caveman understanding the compression rings will still see full pressure just not the shock that they would see without the pressure breaker rings. I think that's more of a question than a statement.