Hardened Rotating Shaft Material 1

[JoelGuelph]

Hello,
We are having a problem. We currently use a 316 lead screw in our water treatment reactors. We chose 316 for corrosion resistance, but we are having issues with our seals at the end of the chamber. Our seal supplier suggested having a harder material for the shaft and I am looking for suggestions. The material must be compatible with potable drinking water and resist corrosion. I am thinking that we will likely stick with the 316 lead screw and perhaps couple it to another shaft to go through the seals. Unless someone can suggest an appropriate lead screw.

Our lead screw runs about 4-5 times per day at ~150 rpm for about 5-10 minutes at a time. To be honest, I'm surprised the shaft hardness is causing us problems with such a low duty cycle. I believe that there might be contaminates in the water that are embedding in the shaft and hurting the seals although I'm not entirely sure since there is little to no axial motion. It is our seal supplier who is telling us that hardness is the problem although I'm not so sure.

Any tips, advice, leads?

Thanks in advance,
Joel

 

[arunmrao]

Have you considered Kolsterising the 316 shafts . This will improve the hardness without sacrificing the corrosion properties.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[desertfox]

Hi Joel

Why not get a sample of the water that surrounds the shaft and have it tested before leaping to change shaft material.

regards

desertfox

 

[EdStainless]

I could be. Annealed 316L is very soft. If you need something harder a simple step would be to use 2205. It is listed by NSF for potable water use and it is mush stronger and more corrosion resistant than 316.

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[Tmoose]

In my limited experiences hardness and wear don't necessarily follow each other very well. On the other hand, material compatibility is mighty darned important.

What bears on the ball screws? A metallic nut, or ???

This Cronidur stuff is expensive, but remarkable when paired with the right mating material.

http://www.umbragroup.it/Aerospace/Products/template?id_cat=Cat20

 

[sreid]

Can we assume that the seal is wearing? Is the shaft wearing? What is the seal material? For a water lubricated seal I would think that Teflon or HDPE would be the material to try.