Rix 3k3b-44 3rd stage valve seat

[lostsheep]

Let me preface this with I know little to nothing about compressors let alone this Rix.

That out of the way, I’m a machinist and I’m trying to help fix the 3rd stage head on a Rix 3K3B-44. I’ll do my best to describe the problem but if I say something non-sensical my apologies in advance.

The intake valve seat keeps failing and as I understand it, too high of a pressure is going back to 2nd stage components.

We have 3 heads here, the oldest of which appears to be a metal seat, the 2 “newer” heads have a plastic valve seat. According to Rix, the valve seat is made from Meldin 7021. Assembly drawings we have don’t show a valve seat but Rix was able to give us a drawing that matched the damaged valve seat I was able to extract.

The problem I’m having is getting the valve seat I’ve machined to screw in. My parts are dead nuts, but the female threads in the head have horrible build up. Cleaning up the threads is problematic because they go to a sharp corner and there is only 3 threads anyways (part is .12” pitch is ~.041”). It appears as though the head originally had the threads cut and then a round pressed in to create a hard corner / flat bottom that was then finished machined after the press.

First question, does anyone know if there was a design change , I.e., did the original part use a metal on metal valve seat that was then changed later to a plastic seat?

Has anyone ever repaired one of these and do you have any advice?

Pics of the assembly from top down :

 

[JohnN]

@iain/hsm

The Zen master of all things RIX

 

[iain/hsm]

@iain/hsm

The Zen master of all things RIX

Yeah Right......Chief cook and bottle washer more like. LOL

 

[-JD-]

The problem I’m having is getting the valve seat I’ve machined to screw in. My parts are dead nuts, but the female threads in the head have horrible build up. Cleaning up the threads is problematic because they go to a sharp corner and there is only 3 threads anyways (part is .12” pitch is ~.041”).

Sorry, I probably have little to offer except one suggestion - do you have available, and have you tried a good few rounds of ultrasonic cleaning to penetrate and loosen the bulidup?

Do you know what the "buildup" is. I could imagine some sort of assembly compound to act as both a sealant and threadlocker that has left its residue.

 

[iain/hsm]

You may have the wrong manual or part in your photos.
First thing you need to establish is if you have a 3K3B-44 made for breathing air.
and not an N2, Argon or methane variant

If you have access to the whole block on the brass data plate it should say size and serial number
The size are the piston diameters and the stroke so 6" & 2-1/4" & 7/8" the pistons by (x) 4-1/2" the stroke
This is an ambient pressure description and pretty much as per your drawing
Second your cross section drawing B2750-2 Rev A dated from 1982 is pretty old even at my memory
That drawing changed to B5959 some 10 years later and the valve seat was indeed metal to metal

Now the parts listed in your second drawing suction valve drawing (3rd stage) A3774 rev B you need to check as they don't line up with your photo, the build shows a metal to metal seat while your photo the polymer.

Frankly I would see if Rix US has a complete valve assembly part AN15-A3774 kicking around
I just won't tell you the pricing back then.

 

[JohnN]

Yeah Right......Chief cook and bottle washer more like. LOL

Thank you Obi-Wan !!

 

[lostsheep]

You may have the wrong manual or part in your photos.
First thing you need to establish is if you have a 3K3B-44 made for breathing air.
and not an N2, Argon or methane variant

If you have access to the whole block on the brass data plate it should say size and serial number
The size are the piston diameters and the stroke so 6" & 2-1/4" & 7/8" the pistons by (x) 4-1/2" the stroke
This is an ambient pressure description and pretty much as per your drawing
Second your cross section drawing B2750-2 Rev A dated from 1982 is pretty old even at my memory
That drawing changed to B5959 some 10 years later and the valve seat was indeed metal to metal

Now the parts listed in your second drawing suction valve drawing (3rd stage) A3774 rev B you need to check as they don't line up with your photo, the build shows a metal to metal seat while your photo the polymer.

Frankly I would see if Rix US has a complete valve assembly part AN15-A3774 kicking around
I just won't tell you the pricing back then.

Serial # 4145
Model KB-44

6 & 2 1/2 & 1 X 4 1/2

Does that model denote N2, Argon, or methane?

Sorry about the hodge podge drawing set, it’s what I was given by the owner.

I don’t have an exact number for the head assembly but I know they are absurdly expensive hence trying to repair the ones we have here.

Right now we are considering 2 options. For the plastic valve seat, machine a new seat and try to get it in.

For the metal on metal seat, re-cutting and / or lapping the sealing surfaces.

Thoughts?

 

[iain/hsm]

Serial # 4145
Model KB-44

6 & 2 1/2 & 1 X 4 1/2

Does that model denote N2, Argon, or methane?

Sorry about the hodge podge drawing set, it’s what I was given by the owner.

I don’t have an exact number for the head assembly but I know they are absurdly expensive hence trying to repair the ones we have here.

Right now we are considering 2 options. For the plastic valve seat, machine a new seat and try to get it in.

For the metal on metal seat, re-cutting and / or lapping the sealing surfaces.

Thoughts? View attachment 869252

Great we are on track, I trust and not a road to nowhere. So what you have so far is:

The serial number 4145 tells you its an ancient old build sold originally to Noah the guy with the big boat and all the animals (in their kind) 2 by 2 and not to be confused with NOAA the new guys on the block who warn you of tropical storms and hurricanes.

The part number KB-44 may be someone picking up the B stamp and hitting it offset to make a 3 because someone else was using the number 3 stamp at the time.

But its not a 3K3B-44 at least not for now its not

At this point you can't tell its application N2 Argon Methane etc
Except to say for methane it would have gas packing and unless you have a complete as build photo I can't say but say for now Air or N2 are the suspects

The piston sets are interesting especially the 2nd and 3rd stage being 2-1/2" second stage and a 1" 3rd stage. If I were a betting man my gut feeling would be that the 3rd stage is a fixed piston assembly in that like the 1st and second stage the piston is attached to the piston rod with 4 one inch piston rings

Where as on the 3K3B the final stage piston is floating and 7/8"

Now although I probably have the manual for this model and I have certainly serviced this model for Scott Speciality Gases ( Now Air Liquid) I'm just not sure where to look any more as so long has passed but they were never ambient air builds. Inlet pressure was from memory low around 5 psi and the gas nitrogen. They also had around a dozen of them over in Holland and a few in the UK. Bulk gas N2 but entrained with carbon monoxide at the low end from 2ppm up 5ppm/10ppm for trace analysis up to 20% The last one I scrapped out must be 20 years ago maybe longer and replaced with the 4VX model. When back in the works I will take a look see what I can dig up.

As for your options first define absurdly expensive.

 

[lostsheep]

I am playing middle man here as I’m not actually talking to anyone at Rix. That said, I have it in my mind that the last time one of these heads was purchased it was ~$10-15K ? I also have it in my mind they won’t make them anymore.

I was recruited on this one because I have a decent machine shop at my disposal and surprise surprise I’m a diver.

If I know what I need to do, I should have the skill and the tools. My problem is I just don’t know much about these compressors so I’m trying to get any and all info I can.

 

[iain/hsm]

1. Next option is we assume it really is a KB then something like the KBG-20 and specifically serial number 4480 is also something I worked on in the dim distant past and is the nearest to your serial number and your model number. The good news.

2. It was used for a diving application. Also good news.

3. The inlet pressure was ambient and outlet pressure 2500psi. Not so bad news.

3. The high pressure suction valve was metal to metal seat drawing A2536. Not so good news.

4. It was for Gas Reclaim on a diving bell/saturation chamber system. Bad news

5. The gas was Heliox. Very bad

The client Smit Tak Salvage