Conveyor Roller (mis) Application

By: Franklin

Some years ago I had a client contact me who prepared granite headstone surfaces.
It seems that the stone needs to be sandblasted during this process so the client places the granite piece on a gravity roller conveyor and through it's gravitational impetus it slowly rolls down the conveyor through a sand blasting booth and out the other side. Apparently, the client had recently replaced this conveyor through a local distributor and the bearings on the rollers were failing after just a few months. Given the roller and bearing configuration provided, I'm surprised they lasted that long. Let me explain generally, how a roller and the bearing shielding work.

While a myriad of configurations is possible, A conveyor roller is essentially a metal tube with the ends crimped to hold a bearing assembly in each end. The shaft is either spring loaded so that it can be easily retained in a conveyor bed or is removable, in either case it rides inside the bearings so that they carry the roller load. The roller tube and shaft thickness are dependent on the load as is the bearing configuration. An important variable to the bearings is the environment that the roller will be functioning in. A clean facility with minimal dust, ambient temperature and relatively light product would require a plain oiled bearing with minimal shielding. Conversely, a high particulate environment requires greater shielding to protect the bearing and extend the life of the roller. The decision often comes down to cost versus ROI.

Some of the common bearing types are:
Plain, oiled bearings, on this bearing you can see the ball bearings and they are directly lubricatable.

Shielded, oiled bearings, this bearing has a flange of metal on the outside of the ball bearings but they are still viewable and lubricatable.

Sealed, oiled bearings, these are totally enclosed and prevent contaminants from entering. No reapplication of lubricant is necessary or possible but the downside is that they potentially have a shorter life span.

Grease packed bearings, typically these are shielded or sealed as grease will trap contaminants and wear faster but they remain self-lubricated.

Sealed, grease packed bearings, this bearing remains lubricated and is totally sealed to prevent any contaminant intrusion. These are the most expensive, but provide the longest life span.

That said, the client mentioned above obviously required as strong bearing shielding as possible but what they received was a non shielded plain oiled bearing. To reiterate, this application is in a sandblasting booth with the blast perpendicular to the conveyor or directly at the conveyor roller bearings.

The client had addressed the issue to the distributor that provided the conveyor who replaced the rollers once but then refused to address the issue further. Apparently, on the premise that the client was misapplicating the conveyor although the distributors field representative recommended the conveyor for the sandblasting booth. They were of course happy to sell the client more of the same rollers however. To say the least, I was disappointed in the manufacturers representative as their lack of diligence reflects poorly on everyone in our field and ultimately cost the end user more in down-time and replacement parts than necessary. The distributor representative, wanted a quick sale and sold the client an inexpensive (IE: low profit) piece of gravity conveyor and was just going to lose money continuing to deal with their mistake so they just walked away from the client. This could have easily been prevented and additional sales opportunity's developed had the distributor done their homework.

After the client contacted me and explained the situation, it was obvious that they required a impact resistant sealed greased bearing in the conveyor rollers and that is what I provided for them. They last around two years in that extreme environment and the client has been very pleased with their performance. Having been selling long life rollers to this client for this conveyor for years I see repeat business and have received referrals from them as well although I am in a different state.

Moral of the story?
Do your homework and understand that small companies, although not as potentially lucrative as large manufacturing facilities need your expertise as much or more than the big boys. If you help them be profitable you can develop long-term business relationships that add to your bottom line.

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