Wednesday 20th Nov, 2019

Expert advice on the evolution of apron feeder design

With 37 years of experience in the mining industry, Metso Product Specialist Thomas Thomas shares his insights on apron feeders and their applications with ABHR.

With 37 years of experience in the mining industry, Metso Product Specialist Thomas Thomas shares his insights on apron feeders and their applications with ABHR.

Apron feeders are used to transport large, lumpy, abrasive and heavy ores under severe impact conditions – including wet, sticky or frozen operations.

They are robust machines, designed for long-term use across a diversified range of industrial applications. Their primary function is to extract or feed material short distances at a controlled rate, preventing choking of material that feeds crushers and other equipment. Additionally, apron feeders can be used to reclaim material at a uniform rate from hoppers, vaults, bins and stockpiles.

Over time, the designs of these machines have evolved to meet changing industry requirements and address common problems that operators face.

Thomas Thomas, an Australian-based Product Specialist with global mining and aggregates equipment manufacturer Metso, explains that there has been a quantum shift in the design of apron feeders over the past 20 to 25 years.

Related stories:

“Machine design characteristics have evolved over time and many improvements have been introduced to reduce the need for routine servicing,” he says.

“Apron feeders were traditionally designed with many components that required constant lubrication and maintenance. Cast and forged apron feeder chains are an example of this. Traditional chain designs that required regular lubrication have given way to Sealed and Lubricated (SALT) units, which do not require any lubrication throughout the life of the unit.”

Metso has 150 years of engineering experience and has been manufacturing and designing apron feeders for 125 years. Throughout this time, the company has installed more than 2000 of these machines.

SALT designs for components such as rollers and tractor-type tail wheels have become incorporated into the company’s apron feeders. This was done to improve ease of use for operators and machine reliability, reducing the need for overall maintenance.

“The apron feeder has become so reliable and user-friendly that it generally needs very little maintenance and is now widely available to suit most applications,” Mr Thomas says.

Machine designs have also evolved to improve operator safety. An example of this can be seen in the design of apron feeder pans, also known as flights.

Pans are high impact, abrasion resistant wear parts responsible for extracting material and discharging it from the feeder. During routine maintenance, these components need to be stopped and secured.

Mr Thomas says that if pans move while workers are on the machine, it can be like having a rug pulled from underneath them, posing significant risks for worker safety.

“We have developed a locking mechanism for Metso feeders to address this issue. When the locking mechanism is engaged, a pin made from high-tensile steel secures the chain and prevents it from moving in any direction,” he says.

“To further improve safety, a limit switch or proximity sensor is incorporated to indicate pin disengagement via an audible or visual alarm.”

Proper maintenance is key to ensuring apron feeders remain safe. Mr Thomas says apron feeders don’t require significant amounts of maintenance, although monthly checks to make sure that bolts aren’t loose, and the chains are at the correct tension, is a good practice.

This only requires a brief inspection, but can guarantee smooth operation and longer component life.

If simple tasks, like checking the clearance between the pans and skirts is overlooked, it can lead to premature wear.

Larger clearances also increase the risk of bigger lumps of hard ore getting wedged in the gap. In some cases, this may cause the machine to stall, however it is also possible for a machine to fail catastrophically at its weakest point.

Servicing an apron feeder will often require heavy rollers to be lifted, which can present a potential safety risk.

Rollers sit underneath the apron feeder pans and chain, but changing them can be difficult due to their weight. Even smaller rollers can be too difficult for manual lifting. To address this, Metso developed a tool that allows operators to remove and replace rollers without the need for lifting equipment.

When it comes to selecting an apron feeder, one of the major challenges that the resource industry faces is increased pressure to reduce capital expenditure costs.

Sometimes producers will opt for a cheaper machine that is satisfactory for operating parameters, but doesn’t have the capability to reach future production targets.

Mr Thomas says it is better to choose a design that is future-proofed, rather than purchasing the cheapest machine available.

“This allows greater flexibility in the long term and you will avoid the need to replace or retrofit a larger machine into an existing footprint, which can be a costly exercise,” he says.

Mr Thomas says smart technology could be the future of apron feeder design, with advances in connectivity allowing for greater insight.

Industry 4.0 technology will provide operators the capability to optimise their feeders to production requirements in real time and help them to accurately forecast maintenance requirements to avoid unplanned downtime.

Replacing apron feeder components can be a costly process, often as a result of where it is located in a plant. Access can be difficult, making servicing components an extensive exercise for many operators.

Mr Thomas says there is an opportunity to design feeders in such a way to synchronise the life of key componentry and associated changeout, drastically reducing the total maintenance costs over the life of the machine.

“I think the future is very exciting for apron feeders, with many technological improvements on the horizon.”