Material spillage at conveyor transfer points can pose significant safety risks to operations.
The Mine Safety & Health Administration estimates that 85 percent of conveyor maintenance is a result of fugitive material spillage at transfer points. Along with safety concerns, material spillage can be costly in terms of tons of lost material per year, additional labor for cleanup and excessive wear and damage to conveyor components, as a result of belt mistracking.
Here are four tips operations should note to reduce spillage and, in turn, create a safer work environment.
1. Reduce impact – Loading-zone impact causes wear and damage to the conveyor belt, weakening the belt carcass. To reduce impact at transfer points, position impact cradles under the conveyor. Or, use impact idlers at a transfer point. These are troughing idlers that have rubber-cushioned rollers to absorb impact.
2. Load in the center – Ideally, each transfer point should be designed to load the belt in the center and at a uniform rate. Off-center loading can be corrected by using systems such as deflectors, liners, baffles, screens, grizzly bars or a curved loading chute – all of which are designed to consistently direct material flow onto the center of the belt.
3. Maintain proper belt scraper tension – For effective cleaning, belt scrapers should be installed at the appropriate locations and at the proper angles. Since multiple belt-cleaning systems are often factory-installed, operators need only concern themselves with maintaining accurate belt scraper tension and replacing worn scrapers. The majority of blade-to-belt cleaning systems feature some form of tensioning device that should typically be checked or adjusted on a weekly basis. An improperly adjusted belt scraper will lead to material carryback, premature wear to components, and eventual spillage and belt mistracking headaches.
When retensioning is required, the cleaner and tensioning unit should allow for easy access and maintenance, without the need for special tools or multiple service technicians. Tensioning instructions are often located on the side of the belt scraper manufacturer’s bracket.
4. Select and maintain proper skirtboards – Skirtboards are key to preventing material spillage in and around the loading zone – from the moment that material leaves the loading chute and until it reaches belt speed. So skirting usually extends from the loading chute and along some distance of the conveyor. Skirting should make slight contact with the belt, and should be mounted close enough so that the gap can be sealed with flexible rubber or urethane strips. Multiple-layer edge seals (a primary seal against the chute wall and a secondary seal that lies on the belt surface outside the chute) are best as they can contain any escaping fines.
Note that seal wear life is dependent upon minimizing belt sag, which can allow material entrapment. Wear liners should be installed inside the chute to protect the sealing strips from the forces of the load. To prevent spillage and maintain skirting life, hoppers should be lined, checked for wear areas or both.
Also, it’s important that skirtboards and loading and discharge chutes be selected and installed to match the characteristics of the material, as well as the conveyor.
Information from this article derived from Pit & Quarry University. Learn more here.
Related: Safety considerations to make related to belt cleaners