Pit & Quarry • February 2021 • HAULING

How rear-eject equipment offers increased versatility for aggregate applications

In aggregate, as in any industry, selecting the right tool for the job is the key to efficient operation.

Using a screwdriver to hammer in a nail might work, eventually, but only after a lot of wasted effort. For a number of primary applications, such as drilling, screening or hauling ore, single-purpose machines help producers maximize productivity and output by doing one task and doing it well. When it comes to support equipment, though, the solution lies in a multi-tool.

While select underground operations realize the value of rear-eject haul trucks for moving ore, many large-scale producers might consider these machines a one-trick pony – suitable for haul road maintenance, but not much else.

Rear-eject bodies, however, offer a number of productivity-enhancing benefits. And when paired with the right combination of attachments, they can revolutionize applications such as reclamation, haul road maintenance, stemming and more.

KEEPING IT LEVEL

In certain underground applications, including aggregate, gold, oil shale or salt, rear-eject haul trucks are an essential link in the production line.

Producers simply drive the vehicle in, load and return to the surface. This much could be done with a traditional end-dump vehicle, if size allows. But it’s the next step – offloading – that sets the rear-eject apart in terms of productivity.

As the name implies, rear-eject bodies use an ejector blade to discharge material. Without moving or raising the truck bed, the blade pushes material toward the rear of the truck. As the blade moves to the rear of the body, the unit’s tailgate lowers.

To reduce maintenance and the risk of breakdown, some rear-eject models incorporate the tailgate mechanism in the sides of the body. These units use simple mechanics, supplemented by gravity, to lower the tailgate without the need for additional hydraulic cylinders.

Some manufacturers also design their rear-eject bodies to feature a unique sweeping action that virtually eliminates carryback – even with materials prone to sticking to the sides or floor of the truck bed. This effective dumping action makes rear-ejects an ideal solution for increased productivity in a number of challenging hauling applications.

When considering the efficiency benefits of a rear-eject body in hauling, time savings is probably the most obvious. It takes roughly 12 seconds for an end-dump body to lift, a few seconds for the material to flow out, and another seven seconds to drop back down. With a rear-eject, there is no need to lift the body, saving producers at least 19 seconds per offload.

The rear-eject’s stationary body also provides an even greater benefit: consistent clearance. Every quarry has a number of overhead obstacles. Room height, legacy structures, bridges, conveyors and other equipment can all make access difficult – or impossible – for traditional end-dump bodies.

In situations where height restrictions rule out raising an end-dump body – such as offloading materials inside a building, near existing structures or underground – operators must rely on loaders and other smaller support equipment to move materials, which significantly reduces efficiency for these tasks.

Additionally, operations that use end dump haul trucks risk accidents while moving around low-clearance structures if the bodies are not completely lowered every time.

A rear-eject body, however, removes the height variable, allowing operators to safely access limited-clearance areas and maneuver around the quarry. This boosts productivity for applications like reclamation, where large amounts of material need to be moved.

Now, producers are able to quickly deposit overburden materials right where they need them – without worrying about lifting the body of the truck. This saves valuable time and can increase efficiency for these support tasks by up to 25 percent.

EVEN SPREAD

In addition to opening up access to more areas of the quarry, rear-eject haul trucks can also increase efficiency for tasks where materials need to be evenly and precisely distributed, such as haul road maintenance or certain drying applications like spreading salt, diatomaceous earth or lime onto leech beds.

Rear-eject bodies provide the operator with complete control of discharge and the ability to dump materials on the go – something highly discouraged with end-dump trucks due to increased safety risks such as tipping or material bridging. The ejector blade pushes material out of the truck body at a steady rate, even while the vehicle is moving, offering a uniform distribution of material to fall behind the truck.

For haul road maintenance, especially, rear-eject bodies offer optimized productivity. Traditional methods involve carefully trying to meter out aggregate with a loader from a large pile. This tends to leave an uneven spread of material that needs to be smoothed either by the loader or additional support equipment.

In the winter, when icy haul roads occur and grit must be regularly applied for safe and efficient use and much needed traction, a crew of two to four workers might spend their whole day spreading sand. This reduces the quarry’s overall efficiency, as labor and resources must be reallocated for this task.

With a rear-eject body, on the other hand, a single operator can effectively distribute sand, grit or other aggregate from the comfort of the vehicle’s cab, resulting in better workforce utilization and increased productivity.

Adding a material-spreading attachment provides maximum equipment versatility in every season. These attachments are designed to integrate seamlessly with their rear-eject bodies.

They can handle a range of aggregate – from very fine to 2-in.-plus-sized material – and spread width can be adjusted from about 5 ft. to 60 ft. or more.

In winter, operators can quickly and easily add traction to icy roads and surfaces throughout the quarry in a single pass. In spring and fall, the spreader can be used to build up and maintain haul roads. And in summer, the attachment can be removed to optimize hauling and spreading with the rear-eject body.

For many producers, the addition of a rear-eject haul truck with a material spreader attachment eliminates the need for a dedicated piece of sanding equipment, increasing efficiency throughout their operation and providing a fast return on investment.

STEMMING LOST PRODUCTIVITY

Stemming is another time-consuming task where the right attachment can revolutionize productivity and increase rear-eject versatility.

Like haul road maintenance, many operations rely on side-dump buckets or loaders to fill blastholes after the explosives are packed in the bottom. Using a single 3-ton loader, operators might only be able to fill two holes per load before traveling back to aggregate piles.

Depending on how close the stockpile is, this can result in cycle times of 15 minutes or more. With each blast averaging 100 or more holes, stemming could take several hours to several days and from two to four crew members, creating a significant drain on productivity.

Using the rear-eject body, producers can transport large amounts of stemming material – up to 60 tons, depending on the truck’s capacity – to the individual blastholes. The stemming attachment’s arm is then positioned over the hole to precisely deposit material. The ejector blade pushes material to a cross auger, which loads the stemming arm. The ejector blade speed, in-cab controls, stemming conveyor and operator controls at the stemming arm all precisely control the flow of stemming material for even distribution.

Producers running a rear-eject body with a stemming attachment on a 40-ton articulated truck have been able to streamline the process and increase efficiency 200 percent, reducing cycle times to just 7 minutes per blasthole.

When stemming is complete, the attachment can easily be removed, and the rear-eject body can be rerouted for other hauling and dumping applications.

MULTIPLYING OPPORTUNITIES

Support equipment might not be doing the heavy lifting when it comes to aggregate operations, but there’s no denying the role these machines play in overall efficiency.

With the right attachments, rear-eject bodies are capable of a few more tricks than just haul road maintenance. Their versatility offers producers an opportunity to streamline small-scale hauling operations with a single piece of equipment for increased productivity and long-term success.