UNDERSTANDING THE BASIC PRINCIPLES OF PULLEY LAGGING
The Two Principle Functions of Pulley Lagging
Provide Traction Between the Conveyor Belt and Pulley
This is especially important for drive pulleys. Maximizing traction helps to prevent slippage during start up and operation. Slippage in the best-case scenario will wear away the conveyor belt, but in the worst case will cause a fire. Slippage is the main cause of fires on conveyor belts.
Provide Wear Protection for the Conveyor Belt and Pulley
Pulley Lagging should be viewed as the sacrificial material due to the fact that it is far less expensive than the Conveyor Belt or Pulley and far less expensive to replace in terms of material costs, downtime costs and replacement job costs. It is important to note that bare pulleys wear away quickly through normal operation of the conveyor belt.
Pulley Lagging should provide a cushioning effect to prevent or reduce damage to the Conveyor Belt and Pulley caused by debris trapped between the Conveyor Belt and Pulley.
Additional Operational Requirements of Pulley Lagging
Pulley Lagging should have a decent service life so as not to introduce unplanned or frequent downtimes. The cost of downtime, especially unplanned downtime, is far greater than the marginal cost difference between a high quality Pulley Lagging product and a low quality one.
The process of replacing Pulley Lagging should not introduce significant downtime or require excess spares of Pulleys. See our article on Cold Bond vs. Steam Cure.
Pulley Lagging itself should not wear away the Conveyor Belt. The material cost of Pulley Lagging is far less than the Conveyor Belt and the associated costs for replacement of Pulley Lagging are far lower. See our article on Epoxy-Ceramic Pulley Lagging.
Pulley Lagging should not damage other components or risk damaging them. Damage could be caused by vibration or by a failure mode of the Lagging.
20mm Thick Diamond Lagging absorbing the impact of stones and mud on a tail pulley on a coal mine in Thailand. The plough was not operating properly.
The Basics of Pulley Lagging Design
Tread Pattern
The primary function of Tread Pattern is to efficiently and effectively expel foreign matter that comes between the Pulley Lagging and the Conveyor Belt. Typical examples of foreign matter are water/moisture, other liquids, mud, sand and stones. By expelling this matter, the Pulley Lagging maintains direct contact with the Conveyor Belt thus traction remains largely unaffected.
Tread Vs. No Tread. An Argument Against Plain Lagging.
Material
The material or combination of materials dictate the coefficient of friction between the Pulley Lagging and Conveyor Belt. The higher the friction coefficient, the more power can be transferred from the Pulley to the Conveyor Belt.
The material or combination of materials dictates the potential service life of the Pulley Lagging.
Rubber Compound
The rubber compound plays a large role in dictating the service life as well as the inherent safety of the Pulley Lagging.
We always recommend our Type F compound for a few reasons:
- Conveyor belt slip can happen, especially during start-up of a fully loaded belt. Slip incidents create extreme heat and fire is therefore a risk.
- Bearing failure creates extreme heat, which could also set the Pulley Lagging alight.
- The cost difference between our Type F and our Abrasion Resistant compound is marginal.
- Given the total cost of a Conveyor Belt System, nevermind the cost of losing an operational conveyor belt system, reducing the risk of a fire that could burn the whole system down should be a priority.
- The ABEAR Type F compound still has excellent strength and decent abrasion resistance, so the overall service life is not too negatively affected.
Should the decision be taken to not use Type F, we then recommend our Abrasion Resistant Compound. It offers the longest service life, excellent traction and minimal heat build-up.