Journal Bearings, Lead, and the ethics thereof

[tk90]

Hello, my company is constantly exploring alternate bearing materials (largely as a means of boosting catalogue options- there isn’t a specific performance goal in mind). One such material family is leaded bronzes like SAE 660.

I have been opposed to adding leaded products to our catalogue- these are wear items and I believe it is in our best interest to limit lead introduction into the environment if possible. Am I entirely off base in this idea? A new team member has been strongly advocating for them and his argument is simply the ubiquitous nature of these materials within the industry today. I don’t doubt or deny their beneficial properties, it’s simply an ethics perspective for me.

(To that end, we have been minimizing our ptfe usage as well).

 

[dgeesaman]

I think it makes sense to minimize PTFE generally. It's just so hard to keep it out of the environment and our bodies.

Lead is a more nuanced question. Lead in aviation fuel = awful. Lead in airgun pellets that end up in the dirt = minor issue. Lead in ammunition that ends up being eaten by birds = serious issue. Lead in batteries that ends up recycled = minor issue. So really, how is lead in your products hazardous on the production, usage, and end-of-life stages? There are numerous toxic materials out there that serve us very well - if we use them intelligently and manage their risks. Lead in bearing materials doesn't strike me as a highly risky application but I have not done much research on that specifically.

"ubiquitous nature... within the industry" begs some thought. Will you lose business today if you offer fewer leaded materials? Will you lose future business if your products are suddenly undesirable (or illegal) when a less toxic material option takes over?

 

[Stick.]

I would tend to agree with you (and generally switch to non-leaded alloys when the opportunity arises in my work), although I admit I don't have a rigorous technical basis for that; it's basically just "lead is toxic, probably best to avoid it if I can".

As for you coworker's reasoning that lead's ubiquity makes it acceptable, you could have used that to justify the continued use of nearly any pollutant in the past, like asbestos, leaded gasoline, DDT, CFCs, so I don't think that argument really holds up.

 

[dtimberlake]

If the bronze bearing ever experience less than EXCELLENT full film lubrication you may find that a leaded bronze offers huge benefits.

 

[TugboatEng]

It's difficult sourcing even non-leaded bronze materials that can be advertised as lead free. This is a requirement to sell certain products in Europe.

With that said, I suggest to look into metalized graphite if you're looking to avoid lead and PTFE.

 

[Sparweb]

Do you have a way to tell how much of your products end up in landfill rather than recycling?
I would want to know something about the final destination, not just the user's application, to make my judgment of lead in bearings.

 

[Tensile_test_my_spine]

Why not oil or polymer-impregnated sintered bronze bearings? You would lean away from the lead and (I think) still avoid PTFE by tuning your impregnation media to the use case.

 

[TugboatEng]

The lead is in the bronze. It's difficult to get bronze to meet the low lead requirements for sale in the EU.