Rolling the competition

The Weir Enduron HPGR.

Weir Minerals’ Enduron High Pressure Grinding Rolls can unlock improved productivity and efficiency gains through its technical capabilities. 

There is a fine line between cost of ownership and productivity gains that must be considered when purchasing plant and equipment for minerals processing applications.

High pressure grinding rolls (HPGRs) have become the machine of choice for many hard rock crushing and grinding operations. 

Due to the inter-particle compression mechanism, HPGRs offer a step up from conventional rod and ball mills when producing fine products.

These traditional methods consume up to 40 per cent more energy than HPGRs as more power is required to break down coarser particles in the feed, which can drive up energy costs.

The Enduron HPGR mechanism involves inter-particle grinding, achieved through the action of two counter rotating rolls that compress the feed bed, enabling particles to grind one another. The crushed particles also display significant levels of microcracking which has the benefit of improving downstream liberation, optimising the ore recovery process, increasing productivity and profits.

Weir Minerals’ Enduron HPGR adopts a dynamic skewing technique to ensure consistent grinding pressure across the full width of the rolls. 

The company regards skewing as an essential feature of HPGRs, as poor uneven grinding and selective tyre wear are common issues faced without it. 

A lack of skewing or the suppression of skewing can lead to reduced product quality, early machine failure, increased downtime and costs, as well as lower productivity.

Many HPGRs offer some form of skewing suppression, however, these methods suffer from feed variance and segregation. 

Weir’s Enduron HPGR instead adopts dynamic skewing, which maintains optimal pressure for comminution.

“The challenge for HPGR manufacturers is to design a machine that can handle the skewing in a good way,” Weir Minerals’ minerals process manager Peter Lempens tells Australian Mining. 

“Without a proper design in place, skewing can cause mechanical failures on the equipment such as its bearings.”

According to Lempens, the Enduron HPGR uses a bearing design that can enable skewing. 

The bearing construction allows the machine to have stress-free skewing control.

Many HPGR models use fixed positioned lateral walls, but Weir’s spring-loaded alternative gives a perfect seal and prevents materials from exiting the high-pressure area without being ground correctly – a common problem associated with traditional lateral walls. 

Lempens says the Enduron HPGR’s unique spring-loaded lateral wall is one of the many features that makes Weir’s machine a superior option.

“We have a special design that allows roller skewing, which also includes self-adjusting spring-loaded lateral walls,” he says.

“At the moment when the roller is skewing, the lateral wall can follow the roller and that will give you a very good sealing at the edges of the tyre, which makes the process more efficient, optimising the recirculating load.”

Weir’s Enduron HPGR uses dynamic skewing to increase productivity and efficiency.

The Enduron HPGR also features a length over width (L/D) ratio of close to one.

“That means the diameter is very similar to length of the tyre,” Lempens says.

This further minimises a common HPGR-related issue known as the edge effect, which occurs when ore bypasses both rolls and is not crushed.

“Most of the designs of other manufacturers have a smaller L/D ratio, which results in more pronounced edge effect than (what) you see from our designs,” Lempens explains.

“The lateral walls that follow the roller, combined with the L/D ratio make sure that the edge effect is almost not present, so it does not have a significant impact on the grind that the machines are giving.”

Weir has incorporated a stud-lined roll surface to the Enduron HPGR’s tyre that increases the tyre’s overall lifetime.

“The HPGR tyres are the most important wear part within the HPGR,” Lempens says. “Even for the most abrasive applications, we can provide customers a lifetime of at least one year, however, we also have applications with softer and finer ores where the lifetime goes up to three to five years.”

Weir does extensive testing on the customer’s ore samples to validate equipment sizing recommendations. Lempens says the company conducts testing on ore for particular applications to give accurate determination of the tonnage that the Enduron HPGR can achieve. 

“Our scale-up from test to industrial scale has been validated for almost 25 years. Tonnage wise, our HPGR achieves what we calculate it will do,” Lempens says. “Product-wise, many of our customers give us the feedback that the quality of the product is even better than what they expected and further downstream benefits also exceed their expectations.”  

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