January 24, 2018

Composite conveyor rollers

 

Rollers - rollers on a weigh scale on the ship loader  conveyor belts at Richards bay Coal terminal in South Africa 3

The quest for superior efficiency Lorbrand Composites South Africa explains to African Mining Brief how composite conveyor rollers, which are made of reinforced proprietary materials, are addressing the limitations of standard conveyor roller offerings in mines worldwide.

In recent years, the mining industry has been confronted by conveyor roller manufacturers offering their low cost hdpe and steel conveyor rollers as a replacement option for OEM equipment. Its challenge is to identify whether these options would enable mines to comply with legislation on safety and environment, counter escalating operating costs, as well as add value to the conveyor system value chain.

The consensus has been that the low cost steel roller and hdpe or other plastic options are limited in scope, as they can only work best in certain areas and fall dismally short in others.

Steel rollers, despite their undisputable structural strength are more susceptible to corrosion and abrasion in wet environments. These high wear environments create the possibility that a damaged or worn roller can cut the belt, causing rapid and significant damage to the belt. Furthermore, steel rolls are heavier and they require more lifting effort, exposing workers handling them to back injuries. Unwittingly, this situation increases a mine’s potential for incurring unanticipated compensation costs. Steel rollers are also not easy to recycle, as they require significant inputs before recycling is complete.

The typical hdpe roller simply cannot compete with a similarly dimensioned steel roller in terms of handling load in high performance applications. There are very few composite roller manufacturers offering Cema E and Cema F load capability across the typical belt widths in these conditions. The advanced composite plastic roller is designed to compete head on with a quality steel roller in the highest load and fastest belt applications and will match or exceed steel’s performance.

Practical alternative

Lorbrand and Lorbrand Composites, two companies on the cutting edge of composite technology, have spent years exploring ways in which the composition of a composite roller can be improved to enhance its durability. The team at Lorbrand Composites share with African Mining Brief their perspectives in the area, with particular reference to their infield experience. They say that the company has gone a step further by providing composite rollers in a range of materials encompassing Nylon, sintered reinforced hdpe, and the new FRZ material approved for use in underground applications through polymer technology. This has resulted in products that offer a wide range of advantages in terms of safety benefits, operational benefits, significant cost savings and carbon footprint reduction.

Safety benefits

Users need to choose the right material for the environment. Flame retardant material should be used in a mine where the risk of fire is assessed as high. HDPE or composite should be used where the risk of fire is assessed as low.

Most hdpe cannot be made fire resistant without a significant loss of mechanical properties. A nylon based product is best suited for an application where fire is a risk because in its standard form it is fire resistant to V2/V3. Where static and fire are issues then a bespoke compounded material usually nylon based is the correct material choice. An anti-static and flame retardant roller will combine a flame retardant capability with real conductivity across the shell. The typical copper wire through the bearing housing is literally useless in conducting static charge buildup if the shell is not conductive.

At the advanced end of composite rollers, very few rollers can comply with the FRAS requirement. The roller manufacturers that do comply have typically passed the requirements of Australia’s underground mining authorities, which is the most demanding specification.

Toxicity of burning materials must not be ignored. A number of materials are flame retardant but in order to achieve this chemicals added to deliver the flame retardancy   emit very toxic gases when burnt. In the tragic event of a mine fatality linked to fire underground, the death is often caused by asphyxiation caused by the presence of harmful gases. These gases need to be kept below significant ratios and only advanced materials deliver this result.

Operational benefits

Advanced composite rollers consistently show that in the most testing environments a composite roller will outlast steel or less advanced hdpe counterparts. This means more uptime, fewer roller replacements, less inventory holding,less roller inflicted damage to belt, much lower noise emissions and most importantly significantly reduced power consumption.

  1. Significant costs savings

Cost savings is another area where the composite rollers offer better value over steel or typical hdpe alternatives. The average mining customer should expect significant cost savings when using a high quality composite roller in terms of the following factors:

  • Reduced cost due to fewer replacements
  • Reduced power consumption and potentially reduced service costs to motors and drives due to lowered startup stresses
  • Lower noise emissions
  • Reputable manufacturers will offer warranties beyond the typical 12 months –in a few cases the warranty can be increased from 12 months to 36 months or in some cases 60 months (provided the mine inspects and maintains the conveyor and creates accurate records )

Easily recyclable    

Composite rollers also help a mine achieve “green points or carbon footprint reduction” through recycling. Composite roller material is of a high quality and has a significant value in the recycling market .The construction also lends itself to easier recycling with disassembly far simpler and more energy efficient than typical steel rollers.

‘Not all composites are made equal’

The typical hdpe roller is made using an off-the-shelf pipe typically made for the plumbing or storm water industry. This pipe is typically made from a combination of hdpe materials aimed at keeping cost low. This kind of tube will not have the mechanical properties required for making rollers. These requirements are stiffness ,straightness, roundness and some heat resistance .In some instances, hdpe rollers have been seen to bow beyond the tolerable limits i.e. 0.5mm per metre spending just a few minutes in the sun which would compromise bearing and roller integrity very quickly.

The above average user of composite high performance rollers should be looking for benefits such as:

  • A roller life cycle far exceeding a typical steel or hdpe roller
  • An improved life expectancy reducing cost of ownership over time – say 3 to 5 years minimum life with a reduction in conveyor roller spend exceeding 20% per annum
  • Improved shell wear by at least 40%
  • Significantly less roller change outs
  • Significantly less belt damage from rollers
  • Reduced energy costs-at start up and during operation
  • Reduced noise –at least 60%
  • Ease of handling
  • Recycling and improved waste management

Research and Development Research and development is key. The conveyor roller industry needs to contribute to the profitability of mining and developing products that outlast and outperform their predecessors is key to ensuring a sustainable mining industry. Simply tweaking existing designs does not achieve this goal. A commitment to technology and research incorporating the newest cutting edge design software and suitably qualified designers is the only way the conveyor roller industry can move forward and play its part.

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