Conveyor Belt Roller and Pulley Failures

This is indeed a severe duty. I don't know what types of bearings and strategies you have been trying, nor am I an expert anyway, but maybe some brainstorming is in order.

If you are using unrelubricable sealed bearings, I bet that fine dust would sooner or later work its way in anyway, expecially if they remain unattended for long. If unsealed bearings are greased often enough, the periodic outflow of grease will inhibit inward migration of dust, but the regreasing interval might need to be impractibly frequent. [I operate fish-processing equipment with a greasing period of 4 hours to prevent salt water from getting in. If you have 22,000 idlers that need a schedule like this, you can keep an army busy! (We just cheat--once a day if lucky. No problems so far, knock on wood; but we need to change a rotary knife and a surgical blade pretty often.)]

Maybe I'm daydreaming, but I would look for a bearing with lip seals on either side, so that new grease could be injected, say two squirts; the ejected old grease wiped off; and one more squirt of new grease, but not wiped off. Wild guess--once per week, so it doesn't need such a large army. That's the brainstorming part; I'm only guessing.

or Autolubers? For example:

http://www.perma.com.au/documents/perma%202nd%20Edition%20catalogue%202009%20web%20res_6.pdf

I am more familiar with those conveyors used in warehousing and manufacturing. Most the idle rollers are relatively inexpensive. There are manufactures that make labyrinth seals to protect the bearings in dusty applications. You will need to address that with the manufacturer they will want to know the contaminate. Are the metal dust shields still in place? I that application there are usually shields on the sides of the conveyor. That drop down around the roller end to keep the bulk of the dust from falling directly on the bearings ends of the roller.

you might try a weekly inspection with an infrared camera. The bearings that fail will start to heat up, and if you can find them in advance, replace them without stopping the line. With 22,000 of them, it might be a full time job for some person to go over the whole line again and again. One way would be to make the camera ride the line and look at them. There are many possibilities.

It might cost more to hire the kid with the camera than to fix them as they break...unless they fail catastrophically.

Hi Ed,

An excellent over-view and please accept my GA ! In a slightly different context I was involved for a time in the field testing of large earth movers and the issue there was with the idler roller seals on the track frames. Again simple lip seals failed early on despite the '2 pumps ' per 8 hour shift into each nipple. The solution was an extended clearance zone out-board of the main seal, this seemed to be a cost effective way of avoiding premature wear. The rollers were subject to ground conditions which varied so much that there never was a case of 'one size fits all'. We just kept things going at a realistic and tolerable repair rate.

Best wishes,

Massey.

Thanks, guys for the GA's.

I just noticed that I somehow clipped some lines off the part about wet sand foundries.

It should read:

"As a side note some of the larger and more modern iron foundries in order to reduce dust have gone over to using water to remove the molding sand from the castings. For reuse it is collected and handled wet until a final centrifuging process to lower the moisture content to the right level for mold making. I never had any experience in that area."

Ed Weldon

Stupid question, but has anyone tried a solid roller made from UHMW or Teflon? dispense with the bearing completely and just use a big chunk of bearing grade plastic. No more lubrication issues, just replace it when it gets worn out.

I suspect the loads and especially roller rotational speed in these conveyors are too high for the PV (pressure x velocity) limits of Teflon and UHMW or even the best grades of plastic sleeve bearing materials. This has a lot to do with the poor thermal conductivity of most plastics which allows destructive heat buildup. This is where antifriction bearings fit in.

The other problem with plastic materials of this type is that the costs begin to run away exponentially as the physical size of the plastic parts increases.

Lastly, plastics are not great in abrasive environments where the particle size is small enough to enter the running clearances. The particles get in and embed themselves in the plastic where they abrade the steel shafts they run on. Unlike a babbit or bronze hydrodynamic bearings (very high load "PV" capability but not suitable for excess abrasives) which embed the occasional tramp abrasive particle there is no oil film in the plastic bearing to prevent contact of the particle with the rotating shaft (or sleeve in the case of rollers on a stationary shaft).

Ed Weldon

Superior Industries manufactures an idler that uses HDPE rolls, but they still use sealed bearings. The units are marketed more as an energy saving device. If you are interested, here is a link:

http://superior-ind.com/products/components/idlers/moxie-rolls

I am assuming your system have Troughing Idlers, bend pulleys, return pulleys , head pulleys, tail pulley, impact idlers etc. If the failure rates are on the troughing and return idlers you may want to look at your lubrication program. years ago their pulleys carries lubrication point but within the last ten years manufacturer as replace these with seal bearing and of such previous rollers of these kind would only fail when the rollers wear. At that time a smart maintenance person would put in extra grease to form sealing and lubricating the bearing. the current condition do not accommodate that and in some cases like in an alumina industry these failures increase as the seal do not meet a standard that will seal entirely these bearing.

You can shop around for better troughing idlers and in some cases install your own lubricant point. also whenever you use non impact idlers where the load comes on the belt you increase these failure.

Leroy

The problem is likely related to dust and lubrication as the others have explained, but I would also make sure that the idlers are the correct CEMA grade for the load/duty. If CEMA B idlers are being used where CEMA D idlers should have been specified, failures will likely occur on a regular basis.

Saw your message here and had to comment.

Typically if the rollers are corectly dimensioned, the main reason for bearing failure is either the dirt getting to the bearings or that you get condensation inside the roller and it slowly ruins the bearing.

Assuming that the dimensioning is correctly done, you need to look for the bearing protection. A solution that I am working on is hte HDPE rollers such as the RET-Rollers. www.ret-rollers.de.

On these ones you have 4xlip seal on the outside and a single lip seal on the inside.

On the 15km long conveyor you could enjoy also a nice powe saving with a lower rolling resistance roller.