Cement asphalt plants use bucket elevators to move the material to the plant mixing tower. Bucket elevators used in asphalt plants should withstand high material temperatures (frequently reaching 180-200°C) and operate at high capacity (e.g. up to 100-200 tonne/hour).

An asphalt plant in South Australia had operational capacity problems and frequent DIN bracket-type bucket elevator system breakage. The plant was only producing 85,000t annually, which was quite low compared to the standard 100t per hour over a 2,000-hour system life (200,000t per year). In addition, they experienced significant downtime due to replacing the chains and brackets every 8-12 months, negatively impacting their efficiency and throughput.

The Challenges with the Current System

The current system had a few shortcomings, such as:

• Low chain hardness: Forged chain links were wearing faster due to lower hardness.
• Small wheel diameter: The small wheels did not fit the chain size, accelerating wear in the interlink area.
• Single-link contact: Each wheel rotated and pivoted the bucket on a single link, concentrating the centrifugal load and causing high interlink wear.

In comparison to the short life of the DIN system, RUD endless chains only need to be replaced after producing approximately 200,000t. The bucket attachments, however, can be replaced after approximately 400,000t, which was a huge advantage to the plant. The RUD system is superior, with endless chains and bucket attachments, doubling the chain life and increasing component life by four times.

Description of the problem: 

The chain contact with the DIN shackles was wearing out faster in the interlink area because it had lower hardness. The wheel diameter was also too small for optimal chain life.  All the centrifugal load was applied on the bucket shackle as it moved around the wheel, resulting in higher interlink wear.

Some of the issues the plant was facing were:

• High temperature - Resulting in the tempering of the forged shackles.
• Head wheels getting worn - Because they were non-hardened.
• High link wear due to the small diameter of the wheels and single link contact.
• Noisier operation due to chain and shackles not being matched. For example, an 18mm chain was used for a 20mm shackle.

Why did the client approach RUD?

Most bulk material handling sites in Australia using the DIN shackle system are gradually being replaced with the RUD 2WIN solution. The 2WIN system has a 3-link interlink contact, which makes conveyors more stable and provides longer component life.

The client was aware that RUD had successfully completed many upgrades of 2WIN conversions, so they invited RUD to propose a full conversion plan.

Some of the reasons for approaching RUD were:

• Limited availability: The original 20mm shackles required frequent replacement and became difficult to source globally.
• Proven quality: RUD's German-made components ensured reliability.
• Enhanced chain performance: The 19x75 chain spacing offered improved pitch length and higher hardness (82hV, a 10% increase).
• Superior hardening: Continuous chain case hardening provided significant advantages over existing chain hardness.

The RUD Solution:

RUD implemented the 2WIN solution with a 3-link contact with the 19x75 chain, making the conveyor stable even on smaller-diameter wheels. This included replacing the treads with hardened wheels which fitted the existing casings. The treads were a bolt-on design for easy installation and replacement when required. The added benefit was that the capacity could be maintained or even increased with bucket spacing on a 19x75 chain.

RUD bucket elevator systems offer a range of proven, high capacity and flexible solutions for all vertical handling applications. The hardened steel chain systems support large capacity conveying, providing maximum throughput.

• Increased Efficiency - Ultra-hardened chain R100 chain systems handle larger capacities and process more material.
• Easy Adaptability - Perfect for a lump or granular material.
• Durability - German-engineered with long-lasting hardened steel chains and components ensure reliable operation.
• Simplified Maintenance - Easy access casings facilitate fast replacement of teeth, treads, and wheel segments.

The Result:

Regular chain wear measurements will be monitored with a service and support plan to maximise chain life and performance. We use predictable life projections for scheduled maintenance to avoid unplanned downtime. Most of our component kits are planned and delivered well before a shutdown. Backup kits are supplied before planned outages to avoid unscheduled downtime.

A Win-Win Situation

The RUD 2WIN system ensures efficient operation in the demanding hot asphalt environment for many years. The 2WIN attachment, fixed on the bucket, distributes load, and extends the bucket lifespan. Additionally, these attachments are replaced only with every second chain change, maximising efficiency. Full tensioner wheel contact minimises tread wear and extends chain life. The hardened RUD components are superior to the previous wheel, and the treads only require changing every second chain set.

This upgrade with the 2WIN system is a WIN-WIN for both RUD and the client.

If you want more details of our conveyor and drive systems, email us or call us on 07 3809 1300.

Article copyright to RUD Ketten and RUD Australia. This information is accurate at the time of publication, and RUD Australia takes no responsibility for any errors, inadvertent or otherwise. Some pictures are for illustration only.