Read part 1 here.
Mistracking, poor splice life
Improperly squared belt.
Square belt using appropriate tools. An accurate, squared cut will enhance belt and splice performance and ensure that the belt tension is distributed evenly across the belt. It also discourages mistracking, which can occur when a cut is made on an angle, causing the belt to wander. Squaring the belt involves marking the centre of the belt at 3 – 5 ft intervals for approximately 20 ft from the splice area, drawing a centre line based on those markings, and using a square to draw a line that is perpendicular to the average centre line across the belt width. A proper belt cutter (as opposed to a utility knife) should be used for a safer, straighter cut.
Ensuring that the belt conveyor components are compatible with each other is key to all parts running smoothly.
Spillage at the load zone
Poor skirting; no impact protection.
Check and maintain skirting with an easy-to-use system. Skirting is important in the load zone as it stops material spillage leaks, controls dust emissions and eliminates other resulting problems, such as belt damage and mistracking. A skirting system that is easy to service and has corrosion resistant components for less maintenance is recommended. It should be ensured that proper impact protection is available and the belt is properly supported in the load area. Impact protection should take into account lump weight and drop height, and should deliver maximum protection to the belt in the load zone.
Belt damage, conveyor structure damage
Before finding a device that can help solve the problem, the type of mistracking must first be identified. Misalignment of rollers or pulleys, an incorrect splice and material buildup are just a few of the things that can get a belt off track. If a belt is constantly moving back and forth, it is experiencing wander, while a belt that runs to one side constantly is simply mistracking. The device that is chosen depends on which type of mistracking is occurring, along with the belt tension, belt speed, thickness, width, and whether the belt reverses.
Belt damage from seized rollers
Seized rollers cut into belt.
Conveyors should be regularly inspected for seized (non-rotating) rollers. For steel rollers, look for flat spots with sharp edges; these should be replaced immediately or risk cutting the belt. For composite rollers with a steel core, look for flat spots with sharp edges; these should be replaced immediately or risk cutting the belt. For composite rollers without a steel core, replace when feasible.
Belt cleaners not working properly, resulting in carryback
Incorrectly mounted cleaners or belt cupped when passing by cleaners.
Ensure that the cleaners are mounted correctly by reviewing installation instructions. A plant in Canada had developed a whole system to clean up its carryback. The plant supervisor felt it was efficient and limited downtime. However, after seeing a new cleaner installed, the plant superintendent realised that all of the other cleaners were mounted incorrectly. Based on this observation, new cleaners were installed and mounted correctly throughout the plant. The result was an 80% decrease in carryback. Furthermore, if the belt is cupped, introduce a hold down roller to flatten the belt and ensure proper cleaner-to-belt contact.
Pulleys that are too small in diameter can cause several problems, including slippage and splice failure.
Poor cleaning edge and a dirty belt
Poor attack angle, worn blade, or incorrect blade in reference to the material path.
Pole location is vital to the success of the cleaner as it permits the correct blade attack angle, encourages maximum cleaning performance and ensures maximum blade life as the entire wear area of the blade can be used. Optimal cleaning can be attained by paying close attention to the material path of the belt, which is typically the centre two thirds of the belt width. Choosing a blade that is only slightly wider than the material path can decrease blade wear and replacement.
Along with visual checks every day, operations should perform a yearly belt conveyor audit. The audit can be carried out by an internal team; however, participation by a third party is helpful. Simple maintenance tasks that may have gone unnoticed can be identified and addressed by a plant’s team, or components can be replaced that will make the equipment run more efficiently. If nothing else, an audit can help keep the equipment running longer.
Whether a plant is performing proactive maintenance or reacting to a repair need, preparing to work safely is key. In addition to wearing personal protective equipment, using appropriate lock out/tag out procedures and making sure personnel are secured to a sturdy structure, following the proper procedures and using the right products is an essential part of safe and successful belt maintenance.
Over time, carryback, spillage, improper fastener selection and mistracking can cause serious problems for a belt conveyor system. Although these may seem to be everyday issues, solutions are available and are integral to an operation’s success. All too often, plant operators do not realise there is a problem until production is halted, which affects the operation’s bottom line. Quick and easy visual inspections can prevent this from occurring.
Written by Ryan Grevenstuk, Flexco, USA. This is an abridged version of the full article, which appeared in the December 2014 issue of World Cement. Subscribers can view the full article by logging in.
Read the article online at: https://www.worldcement.com/the-americas/15122014/flexco-on-quick-fixes-part-2-992/