Stellite 6

[RobinHood]

The last design I have seen has no annular rings. Just two flat surfaces.

The more complicated design (with the annular rings) was supposed to reduce the (more common) two-stage (2500 psi & 500 psi) homogenization process in to a single stage (hybrid) - or something like that. Sounds like they will be going back to 2-stage.

Not sure about Titanium. I would think that they thought of that since my brother used to design plate heat exchangers systems.

The only two materials they are considering so far are the Stellite 6 (original) and Tungsten Carbide (new).

We’ll see where this all goes.

 

[PeterT]

Maybe not an answer to your specific application (unless Titanium or Inconel would work & you can find a service with a MetalX). More out of interest for applications like this - ongoing metal 3DP evolution. At ~41:00 he discusses the 'older' laser sintered powder system compared to this process.

But my question is always what kind of finish? I think some 3DP metal parts I see in brochures have been have been finished so may not be indicative of fresh from the machine. Some still look like hideous glue gun work. But maybe that's the old system? Maybe the MetalX green state allows some degree of pre finishing before sintering? I'll volunteer do the CAD work just to know how much it would cost LOL.
https://markforged.com/metal-x/

 

[RobinHood]

Update:

We are now using 440C stainless steel. This stuff is used in medical instruments, pumps components, and ball bearings, among others.
It is about C20 annealed and can be hardened to C50. It is rated at 30% of B1112 on the machinability scale, with “tough, stringy chips”. That is what i got when turning at 700 rpm with 0.106 mm/rev. For finishing (1000 rpm, 0.053 mm/rev), the chips were still stringy, but it left a decent finish. I could get the chips to break at 230 rpm and 0.106 to 0.053 mm/rev - it just took forever - so stringy chips it was. The strings can easily be crushed and broken into small pieces.





And the valve seat is taking shape

 

[PeterT]

Finish looks good so far. What are you finding is working for cutting tool? Will the part be hardened or you are just mentioning the alloy can be?
Can any of the free machining SS variatels used in this industry or does the bit of sulphur content pose an issue? (I think 430 is a FM cousin).

 

[Tom Kitta]

Looks like standard SS turning. It is harder then regular steel for sure - about as tough to deal with as 4330 I have.

Through I played with some inconel and that is even worse.

 

[RobinHood]

I use SOWA TNMG MT30P - has been working great in all the SSs I use (304, 316, and now the 440C). They also work great in AL.

So they want two valve seats now, I went through 1 1/2 corners per seat face. The back side will probably need another new edge each.

For now they are going to use the parts as is - we may try heat treating the next round though.

I am not sure how much Sulfur content is allowed in the Food Industry; there is some allowed, as 304 and 316 SS both have a small amount - 0.015% S - per the Thyssen-Krupp website.

 

[PeterT]

I'm going to be watching close how you make those funky (I assume they are seat) profiles on your first pic. Will those also be profiled in the lathe or...?

I was just messing around with different 'clone' inserts I have. Part of the problem is they are all Ebay specials so I don't really know which might be 'real' knockoffs vs just some random pos. But this one particular one is just a better cutting standout on stainless (303). Then I tried it on some crap 1018CRS which always cuts gritty & it was significant improvement compared to my usual go to inserts. This was just light turning, nothing heavy & no chip issues. I also tried a spare uncoated insert from my razor sharp series normally reserved for aluminum on the 1018 steel & it cut better too. But I don't think it would last as long. I think nose radius is a bigger factor than I've realized, or maybe that's just a function of my lathe & what I'm cutting. I guess the moral of the story its worth tweaking things a bit within reason because we cant easily replicate industrial/cnc conditions often times going by the book.

 

[RobinHood]

Peter, here is a cross -section sketch of the OEM valve & seat design.



I would have used a 45* chamfer tool plunged into the face to make the profile.

Their claim to fame apparently is that with their “saw-tooth”, one could homogenize in a single pass. My brother tells me that that works only in very few cases -> traditionally, homogenization is done in a dual pass process (that works all the time). So either you have a dual valve homogenizer (both passes happen sequentially by going through the machine once (high stage & low stage), or by going through a single valve machine twice (once at high pressure, once a low pressure).

Using a two step process, the valve and seat design is much simpler - this is what I am making.



The items in pink were going to be made from Stellite 6 as an improvement to the OEM design to try and get more mileage out of the parts (hence the original query to this forum).

Now we just made the seat wear surface 4mm higher and the plunger longer. As the parts start to wear (mostly pitting), we’ll just take them on the lathe, turn off the worn part and polish. That could be done 4 - 5 times before the parts are too short. We are making two of each, so the customer does not have any down time (the plunger and seat get removed for cleaning all the time) as they’ll always have a usable spare.

 

[PeterT]

Very interesting, thanks for the background.

 

[RobinHood]

And the parts are done. Old seat is front and center. The bar (valve) on the left is the original one they want to re-use; hence the different chamfers. The faces are machined square and polished, so relatively straight forward.





There was one more challenge: the valve seat has a cone (taper) in the back. I needed a way to measure the size of it with some degree of accuracy. The drawing above shows the cone‘s large end to be ~18mm. That is measured using calipers at the intersection of the cone to the step. As you know, that is not very precise. So I came up with this method (probably nothing new to all the pros here):

Here you can see the cone in the back of the original


I found a suitable ball bearing that was small enough to enter the cone so it would be touching the cone wall at some tangent line (it’s actually a circle at some point down in the cone). I then used a height gauge to measure how far the ball stuck out wrt the flat flange face (the area with all the scribbles on it).



I then took the same ball over to the work piece and measured how far it stuck out using the lathe’s DRO (Z-axis) in this case. Then it was just a matter of increasing the OD of the cone until the depth matched the original (about 8.62mm).



Here is the turned part (back side) before polishing



This was fun and once again thanks to everyone that chimed in with all their good advise and suggestions.

I mentioned this to @Dabbler & @johnnielsen the other day: some homogenizers have ceramic seats. My brother tells me that operators keep cracking them because of shock cooling during the cleaning process of the machine.... he’s thinking of going back to some form of SS for them, as each ceramic seat is US$4K. So there may be more of the same projects for me in the future...

 

[johnnielsen]

You are a talented fellow.

 

[RobinHood]

Thanks or the compliment John.

 

[Former Member]

Late to the game, if it is corrosion resistance you are after have you consider PEEK (a plastic) very dense, very corrosion resistant, very temperature stable, used where SS doesn't standup. Very expensive.

Comes from the nuclear sub industry.

 

[whydontu]

My business partners makes high pressure, high temperature, high abrasion, high corrosion valves for mineral processing. 2500 PSI, 750* F, pH 3, 30% solids. Nickel processing autoclaves. Our valve seats are typically HVOF chromium carbide overlays on alloy substrates.

HPAL & POx Autoclave Valves - ValvTechnologies

The mining industry poses some of the most challenging of all severe service applications. The most difficult of these challenges are high pressure acid leaching (HPAL) and pressure oxidation (POx). These applications require experience, reliability and resistance to high-temperatures...

www.valv.com

If someone came to us and described this application, we’d probably look at Hastelloy C276 or C2000, Ferralium, AL6XN substrate and then we’d be considering different overlay materials

HVOF RiTech® - Robotically Integrated Technology - ValvTechnologies

We focus on providing the best metal seated isolation valves to ensure our customers receive the highest level of safety, reliability, & performance.

www.valv.com

Be interesting to see what valv.com engineers could develop for this application.

Bragging - pulp mill in BC historically used Stellite-seated valves as steam isolation for blowdown at the bottom of their power boilers. They replaced the Stellite valves at every full mill outage, a new valve every year, sometimes more often if the valve failed prematurely. They bought a test valv.com valve in 1998. Sold them their first valv.com replacement last June. Lasted 23 years.

 

[RobinHood]

Late to the game, if it is corrosion resistance you are after have you consider PEEK (a plastic) very dense, very corrosion resistant, very temperature stable, used where SS doesn't standup. Very expensive.

Comes from the nuclear sub industry.

Yes, I have made parts for the same customer using PEEK.

This material will not stand up to the pressures inside a homogenizer - hence the industry does not use it in this application.

 

[RobinHood]

My business partners makes high pressure, high temperature, high abrasion, high corrosion valves for mineral processing. 2500 PSI, 750* F, pH 3, 30% solids. Nickel processing autoclaves. Our valve seats are typically HVOF chromium carbide overlays on alloy substrates.

HPAL & POx Autoclave Valves - ValvTechnologies

The mining industry poses some of the most challenging of all severe service applications. The most difficult of these challenges are high pressure acid leaching (HPAL) and pressure oxidation (POx). These applications require experience, reliability and resistance to high-temperatures...

www.valv.com

If someone came to us and described this application, we’d probably look at Hastelloy C276 or C2000, Ferralium, AL6XN substrate and then we’d be considering different overlay materials

HVOF RiTech® - Robotically Integrated Technology - ValvTechnologies

We focus on providing the best metal seated isolation valves to ensure our customers receive the highest level of safety, reliability, & performance.

www.valv.com

Be interesting to see what valv.com engineers could develop for this application.

Bragging - pulp mill in BC historically used Stellite-seated valves as steam isolation for blowdown at the bottom of their power boilers. They replaced the Stellite valves at every full mill outage, a new valve every year, sometimes more often if the valve failed prematurely. They bought a test valv.com valve in 1998. Sold them their first valv.com replacement last June. Lasted 23 years.

Thanks for the great info @whydontu . I’ll add the referenced companies to my arsenal…

The main goal of this exercise was to find a longer lasting valve seat material. 410 SS was not it in the end. We went back to 316 / 304 SS (the industry standard).

Turns out that cleaning solutions/chemicals play a huge role in the longevity of the internal components of a homogenizer. The wrong combo/duration of cleaning cycle can apparently ruin a seat in very short order - as they have found out the hard way…