You are not giving us a lot to go on here. If you can answer the following questions then maybe we can help or certainly give it our best shot.

- By cover I am assuming that you mean rubber lagging or do you mean the steel shell?

- If lagged do you know the durometer rating of the rubber?

- Describe exactly which pulleys are recieving the wear? All or just drives, bends, take-up, etc.? Total number of pulleys in the system.

- What is the center to center distance between the head and tail pulleys?

- Does the belt track in center of the idlers or does it wander and then come back or does it stay to one side or the other?

- Is the return side of the belt dirty - product running on return side?

- How is the belt spliced - mechanical fasteners or vulcanized?

Any other information that you can think of may be helpful.

Regards,

Gary Blenkhorn ■

One other point I would like to bring up.

What is the thickness of the lagging or shell?

I have experienced excessive pulley wear and the only way I solved the problem was to install ceramic lagging on the pulleys. You may not have to go to that extreme but I just need to know more details.

Gary ■

One thing that I come across often is incorrect transition distances. The transition distance is the distance between the pulley and the first fully troughed idler. The correct transition distance is important in that it ensures that the entire surface of the pulley drives the belt. Too short of a transition distance will cause the belt to ride primarily on the center section of the pulley and not across its full width. This will cause the lagging or the belt itself to wear in this area. In the case of ceramic lagging the forces can be great enough to pull the ceramic tiles out of its rubber backing.

Transition distances vary from 1.2 times belt width for a fabric belt at less than 60% of rated tension troughed 20 degrees to 8 times belt width for a steel cable belt at over 90% of rated tension troughed 45 degrees. All this information is available in the CEMA Belt Conveyors for Bulk Material 5th Edition. ■

Few things to check:

1/ Vee return plough.

2/ Impact beds.

3/ Also look for new centre rollers as they may have changed out the seized centre rollers before you inspected the systems.

[ If their looking for warranty ] ■

Well I was totally misled as I was reading it that you were getting pulley wear while what you are getting is bottom cover wear on the belt itself. Sorry for my confusion.

Things to look for:

material build up on pulleys

return plow set too tight

Is the belt troughing fully down to the center roll. If not the belt will skid across the center roll instead of rolling the center roll. (a result of too much tension)

I did a quick calculation on the amount of cwt required and you are about double the weight that is necessary. This could be contributing to the problem.

Is this a replacement belt or a new installation?

Gary Blenkhorn ■

Dear Mr. James,

Looking at your query, numerous replies and your subsequent clarification, you have the problem of fast wear of bottom cover of belt. This could be for following reasons. Many of these reasons are already mentioned by earlier respondents :

1) Slippage between drive pulley and belt. This can arise due to inadequate tension with reference to the actual friction coefficient between belt and rubber lagging, as prevailing in your installation. The friction coefficient can go down substantially if material with adequate moisture is contaminating belt and pulley surface.

2) If you have got dual drive and if there is noticeable difference between natural speed of two pulleys due to mismatching ratio etc. or motor rpm.

3) Too much forward tilt of carrying run idlers.

4) Too much skew placement of carrying idlers. That means the carrying run idlers are not placed properly.

5) If you are using impact bed and its installation is not proper.

6) Excessive pressure from internal belt scraper.

7) Improper transition distance.

8) You are handling gypsum, which is not a very abrasive material, so bottom cover wear due to abrasive dust settled on idlers etc. will not be dominant.

In one of the installation in India; a conveyor with inadequate concave radius was having fast wear of the rubber lagging. It was found that belt was getting lifted marginally up resulting into slippage during starting. Also, it was found that take-up tension was not adequate during starting process and belt was slipping on pulley causing the wear. You have the tripper and if this is not designed properly, the belt will get lifted during starting process. In such situation the remedial measure can be use of heavier belt (more cover thickness) in future. Of course you have to check all the above points and the points mentioned by earlier respondents. Adequate tension is very important. The adequate tension implies with respect to the actual starting factor being applied by your drive unit and it could be different than what is being assumed, if fluid coupling type and other things are not appropriate for the application.

Properly designed, constructed conveyor will not have the problem of bottom cover wear.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

I've come across rapid belt bottom cover wear under the following conditions:

1) over-tensioning of the belt that is running over crowned pulleys;

2) frozen center carry idlers (or as Bruce suggested, new center idlers that have a larger diameter relative to the wing idlers);

3) material build-up on carry idlers, bend rollers, or pulleys;

4) improperly installed, or maintained V-plow (although you have stated that this system does not have a bottom cover cleaner);

5) frame rubbing along the return run; and

6) softening of the cover rubber from blown idler seals (deposits grease on the belt's bottom cover.

Naturally, there are other possibilities. Of the six listed, I've seen #3, #4, and #6 the most often.

To determine what is the cause of your customer's problem, a site visit is necessary.

Regards, ■