Equipment in Abrasive Environment 1

[Farmboy71]

I'm working on an application using pneumatics in a plant that will have airborne cement dust. Does anyone have practical tips for what works and what doesn't in this type of environment? I'm especially concerned about the cylinders, valves, bushings, and bearings(esentially anything that moves). The air used will be dry clean air, but there will be dust gathering on the cylinder rods, etc.

I've got some ideas of things that will probably work, but I'd like some practical feedback. Do bellows/boots help? Do cylinders last longer if they are run without lube? Are there special bearing materials that hold up well?

Thanks in advance,

Farmboy

 

[coatingengineer]

Hello.

Yes, I'd avoid any form of 'wet' lubrication. Lubricants will only trap dry erosive particulate and accelerate wear.

Erosive applications like this are best mitigated through surface hardening.

Consider heat treat for hardness, then polishing and coating. Coatings with 'micro-hardness' are key. Worthwhile examples include B4C ("black diamond") and PCD (polycrystalline diamond).

Erosive applications can be difficult. If you can't eliminate the cement dust through filtration or other isolation-containment, wear-abrasion will likely continue using coatings, albeit at a slower rate.

For more coatings help, see:
<a href="

http://www.industrialcoatingsworld.com/Wear-Resistant-Coatings/index.html">Wear

Resistant Coatings</a>

Good luck!




William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[JamesBarlow]

The most important thing to realize is that no matter how much effort you put into protecting everything it will eventaully fail because of the environment. You can delay that from happeneing but you can not stop it.

Know that the best thing you can do in an environment like that is make sure that everything can easily be replaced. Putting you cylinders in special enclosures and using covers can add a little life, but it also has the potential to add days of down time trying to get to something that is going to fail.

My last position was designing equipment in a foundry and a tremendous amount of effort was put into making sure that all the wear components can be easily changed. Protection is nice, but in some places the protective equipment may do more harm than good.

I would also include redundent systems into everything so the inevitable maintenance could be performed durring scheduled down times.

 

[Farmboy71]

Thanks for the advice.

I did a little research on Diamond-Like Carbon coatings and it seems like a good product for mass produced parts. Is it practical to have a just couple of parts coated? Where could I do this? It seems like it requires specialized equipment to perform the coating.

James, I think you've got a great suggestion. I think you've hit on the main problem with our existing equipment. It's too difficult to replace when it fails.

I may go with rebuildable cylinders that can be swapped out quickly and rebuilt offline.

Thanks,

Farmboy

 

[evelrod]

I spent much of the last four years before I retired at U.S. Borax Los Angeles Harbor replacing high maintenance machinery with more maintenance friendly equipment, replacing chain drives with cogged belts, sealed gearbox direct drives, etc. Borax dust is not quite as bad as cement, but it's bad enough. I agree with JamesBarlow...If you know it will fail, at least make it easily replaceable. A zero defects program is not a bad idea if it's economically feasible.

Rod

 

[coatingengineer]

Hi, again.

Take a look at coatings used in tool cutting. Since they too must combat high abrasive wear.

Coatings like these are processed in larger batches, which means lower minimum charges to you.

Try Oerlikon-Balzers' Futura Nano, which is associated with titanium alumina nitride (TiAlN). Minimum charges, I believe, are around $100-$150. Very reasonable.

Other coatings for extreme wear, like those from IonBond, include boron carbide (B4C or 'black diamond') and polycrystalline diamond (PCD). Minimum charges may be a little higher.

If you like, here's a little more help:
<a href="

http://www.industrialcoatingsworld.com/Wear-Resistant-Coatings/Vapor-Deposition.html">Vapor

Deposition</a>

Good luck!





William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[Newmanite]

Boots work great in a harsh environment,if you are not using lube on linkage points more the fool for you.In some instances it is more expensive to buy a rebuild kit that a new cylinder(go figure?).Brass bushes work well with automated greasing if and when they wear they are easily removed and replaced.Hardness coating is all well and good for the rod but the trick is to keep the seal integrity intact.
Abrasives will eventually get between moving parts in an environment such as yours thats where a stringent maintenance plan would need to be in effect.There are products out there that would protect your linkages to some degree an example of this is the wrapping thats used in protecting new parts from corrossion(sorry for the life of me I cannot remember the product name)and is used in pumping stations in mining to prevent water rusting bolts on pumps.This may be very effective in your environment.

 

[unclesyd]

I believe the tape mentioned by Newmanite is probably a product made by Denso.

http://www.densona.com/Index.htm

For bearing sealing look at products by Inpro or Isomag.

http://www.inpro-seal.com/design.html

http://www.isomag.com/

For sealing hydraulic cylinders there are double lip seals that do a very good job. We used one that was quite similar to the one used on CAT equipment.

On some systems we let a water tolerant grease be the excluding agent. We mainly used products from Lubrication Engineers. The grease products were 1275 or 3752. Both of these products are very water resistant.

http://www.le-inc.com/productPages.jsp?productID=198

 

[macmil]

I worked in cement and concrete for 20 years, most of it in maintenance. It's a tough environment, but regular clean up helps. For pneumatic applications, boots/ bellows work quite well on piston rods etc. For bushings, bearings etc, the airborne dust should not get into the bearing surfaces unless there's a barrier/ seal failure. I echo those who say make it easily replaceable, and have the spares as component relacements. Frankly, pneumatic equipment wasn't one of the major headache areas, other than some compressors. Except in super critical applications, I don't think exotic coatings are normally warranted. Remember grease and cement dust makes an excellent grinding paste ! Where required, non-lube, dry lubricant, and double sealed bearings are preferable to grease which picks up the dust. In a rotating high temperature dust handling situation I used graphite bushings with good success.

 

[Farmboy71]

Thanks for the good practical advice all. I've heard mixed reviews regarding the use of bellows. A couple of people have suggested that the bellows can pull dust in and exacerbate problems. Do they need to have filtered vents on them to allow clean air in when the cylinder extends? Or is it possible to put some positive air pressure in them to keep them purged?

 

[Newmanite]

Permitting the bellows are sealed tightly at both ends,you really shouldnt have a problem.BTW if you get the canvas type make sure you soak them in water for a night the let them dry naturally as this seals the canvas properly.

 

[rmw]

If you have a situation where you know that there is going to be wear due to the environment, design so that you control what wears. As an example, once when facing accelerated wear in star valves handling abrasive dust much like what you are faced with, after trashing some expensive valve housings, the process was redesigned so that replacable soft vane tips were mounted on the stars themselves and the valve bores were hard chrome plated. Under this scheme, the inexpensive blade tips did wear at a rapid rate, but the rate could be predicted and the replacement of those simple parts was much more quick and inexpensive than having to take the valve bodies out of the line to junk the bodies and stars. Often they were mounted in maintenance unfriendly locations.

While this example may not be germane to your specific application; the concept still applies. Accept that you are going to have wear in this environment and make the part that wears be the one that is quickest, easiest, and least expensive to replace.

rmw