Drive chain reliability key to maintaining quarry performance

The quarrying and mining industries have some of the most arduous working conditions for plant and equipment, which makes designing a product that will endure the environment and deliver reliable performance a difficult task.

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With tight margins and continuous production cycles, downtime for maintenance work needs to be kept to a minimum. Derek Mack, UK Sales Director for Tsubaki Europe, looks at the challenges and some possible solutions.

The process of extracting materials from the earth requires heavy duty equipment, the scale of which is increasing steadily in an effort to reduce operating costs and increase efficiency and productivity. However, in the event of a piece of this larger equipment requiring unscheduled maintenance work, the lost production costs increase rapidly, making reliability more important than ever.

The tough challenges of designing products to operate effectively in the quarrying industry have, thankfully, remained relatively constant; but the technology is constantly evolving. One of the main issues to address is the abrasive nature of the materials and the dust generated by the application, which can quickly attack moving parts such as drive chains and sprockets.
As an example, the drive system used on many bucket elevators involves heavy duty chains and sprockets, which can often have a short service life caused by the ingress of abrasive dust between the pins and bushes of the chain. The increased levels of wear leads to chain elongation and damage to the sprocket teeth, all of which will have to be replaced; incurring loss of production and increased maintenance costs.

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With considerable experience in the quarrying industry, Tsubaki has strived to deliver solutions to these challenges through innovative materials technology and product design. The latest FB-specification conveyor chain uses a unique O-ring design between the link plates to protect against dust contamination and uses a solid lubricant which is bonded to the inner surface of the chain bush. Designed for bucket elevators, this design has been shown to double the service life of the chain.

At the same time the bucket elevator sprockets are also subjected to this harsh working environment and often have a short service life which can lead to regular, high replacement costs. To further reduce maintenance requirements, Tsubaki now supplies Thermal Sprayed Replaceable Sprocket Inserts, which are manufactured with a quench hardening system and then treated with thermal spraying to reduce wear. Each single insert can be quickly removed and replaced as necessary when it becomes worn, saving both time and material costs.

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For many maintenance managers within the quarrying industry, keeping control of the budget and trying to reduce maintenance costs can be difficult. When margins are tight, there is always a temptation to reduce short term costs, however this decision can have long term consequences that ultimately will result in higher costs. The key is to concentrate on the Total Cost of Ownership (TCO).

An illustration of this is provided by one of Europe's largest producers of asphalt for road construction, which was using standard 16B chain on a conveyor drive system in order to reduce purchasing costs. However, the chain was suffering from excessive elongation and provided an exceptionally short service life before a replacement was required. This was leading to regular downtime which meant that the TCO remained high.

Tsubaki was approached to provide a solution which came in the form of its GT4 Winner chain, one of the most advanced designs available and capable of significantly outlasting other premium chains on the market. However, rather than just expecting the customer to accept these increased service life claims, Tsubaki offered to run a KG (Koos Geskus) test in which the GT4 Winner chain would be directly compared with the standard chain and another premium chain under the same real-life conditions.

Following 1,750 hours in operation, each chain was measured for elongation, with the competitor's premium chain suffering from 3.3% elongation while the Tsubaki product had only lengthened by 1.9%, making a 42% improvement. When compared to the standard chain previously used by the client, the GT4 Winner had delivered a 45% less elongation, which provided sufficient evidence to the customer that the Tsubaki claims actually stood up in the real world application.

While Tsubaki does supply some OEMs with drive chain and sprocket arrangements, there are many that select a cheaper chain in order to help improve margins on the complete product. Fortunately Tsubaki offers a RetroFIT service which allows customers to source an exact dimensional replacement chain, with no need to change sprockets or chain attachments.

This service allows customers to benefit from the design expertise and improved materials technology that is offered in every Tsubaki product. This includes the use of alloy-grade steels which are heat-treated to precise specifications and assembled with the heavy press-fits necessary to withstand the punishment of today's more powerful, high production mining equipment. 

Tsubaki has developed a surface treatment for its chain and sprockets that provides superior corrosion resistance and significantly extends the service life of the components.  The revolutionary mechanical plating system forms a lasting bond to the steel and is recommended for use on any equipment that may be exposed to external conditions, chemicals or salt water.

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The key to achieving reduced maintenance costs is to improve the overall performance and efficiency of the operation which means looking at the longer term costs and ensuring that the cost of lost production due to mechanical failure is included in the cost of ownership. In the long term, choosing a replacement part purely on a cost basis produces a false economy that will ultimately result in elevated costs and reduced efficiency.

– 2014 October 22