By Josh Swank, Philippi-Hagenbuch
Fine-tuning your fleet means choosing the best of all equipment, not just crushers, screeners and earthmoving equipment.
While those assets are clearly key players, taking a look at things that may not be top of mind — like water tanks, specialty off-highway haul trucks and rear eject material spreaders — may be an effective way to improve productivity.
Examining these aspects of equipment doesn’t only make financial sense, it can also be a determining factor in keeping an operation up and running efficiently and safely.
On the surface, it may appear as though truck bodies don’t deviate much from one design to another. However, new truck bodies, designed to move overburden within mines, now address two major concerns mine operators have expressed. First, the designs have virtually eliminated the loafing effect — that loads of packed material that releases all at once from a truck body during the dumping stage.
Second, they minimize material carryback, ensuring the bulk of the load is dumped the first time for better efficiency.
With a significant amount of load over the rear axle, the dumping motion of a truck body that isn’t designed to combat material loafing often causes the front of the truck — which weighs hundreds of tons on its own — to lift off of the ground. The entire weight then releases at once, slamming the truck and its driver back to the ground. This process stresses both the truck chassis and the driver.
Several carefully engineered modifications now move truck bodies from standard dumps to proficient machines.
First, the shape of the truck bed has been redesigned. Traditional truck beds are parallel-sided, forming a chute for the material to release all at once without breaking up. This often causes the truck to rock with the sudden weight on the rear of the bed. By tapering the sides of the truck and making the end of the truck bed wider than the front, the overburden and other materials are given an opportunity to spread out while exiting the truck body.
Material is further broken up by angling the back third of the body floor down and raking the edge of the floor away from the centre point. By taking the floor away from the underside of the loaf, it’s forced to break apart and exit the truck body with considerably less force on not only the truck chassis, but also the driver.
Additionally, many materials, when transported in truck beds, adhere to the truck’s surface. In essence, the same load is carried again and again when it fails to release when dumped, so it takes a joyride back at the expense of the company. As much as 30 per cent of a truck body’s volumetric capacity can stay behind through added carryback, making for a significant decrease in productivity unless it’s manually scraped from the body floor and sides.
The answer to carryback problems lies in both the design of the truck body and the materials used within and outside of the body itself.
Coating key parts of the truck body underside with a hydrophobic paint will produce what’s known as the “lotus effect.” Moisture within the haul material prevents it from sticking to the hydrophobic surface, similar to the water-repelling characteristic of a lotus leaf. As a result, it’s nearly impossible for anything to remain on the truck. Similar results can be achieved within the body when strategically using hydrophobic and oleophobic steel liners to minimize material carryback.
This hydrophobic technique is being added as a retrofit to existing systems to improve productivity.
Spreading materials may seem like a simple concept, but it’s actually one that involves a great deal of variability and potential for lost efficiency. Material spreaders can be used to build haul roads, for road safety in the winter by spreading sand or gravel across slick and icy roads and in other areas that require dry, solid materials to be discharged and broadcast.
Typical material spreaders operate in a passive mode by using steep slopes to move the material from the body to the material spinners. This results in unsafely raising the vertical centre of gravity. Even though the units have vibratory devices on them, the material still tends to bridge, adversely affecting the operation of the equipment. There are also safety concerns when crew members must manually address the material clogging the highly sloped bodies, often requiring them to get into tight, confined spaces.
An updated option involves an active system, which uses a rear eject body that horizontally pushes material towards the back of the bed and into a cross auger that delivers the material to broadcast spinners. This process increases efficiency by saving time on maintenance and upkeep and is able to cover more ground in a uniform manner safely, efficiently and effectively.
Material spreaders have the ability to evenly distribute material to improve efficiency. Operators no longer need to alter their haul cycles to bypass areas that have poor traction as they can maintain traction on various grades as needed, which optimizes cycle times.
How equipment operators haul and apply water may impact an operation’s bottom line. These water trucks, primarily used for dust control, are designed with several factors that affect efficiency.
In traditional applications, round water tanks are the most common. However, the tank’s curved sides raise the water’s centre of gravity, making the tank smaller than the truck can handle and the truck less stable when navigating haul roads. To mitigate instability, operators often avoid completely filling their tanks. This means they need to refill more frequently, contributing to added downtime and increased fuel consumption as they backtrack to the water source.
Alternatively, water tanks with square corners minimize churning and often have a larger capacity by simply not rounding off the sides of the tank. The design also lowers the unit’s overall centre of gravity, enhancing stability and allowing drivers to safely fill the tank to capacity. The box-shaped structure makes it possible to haul about 20 per cent more water than rounded tanks.
To minimize surging, some tanks feature sophisticated water control systems that use baffling that runs from floor to ceiling as well as along the complete length and width of the tank, resulting in full compartmentalization of the water. Baffles inside the tank help minimize water from surging side-to-side and front-to-back. Almost all water tanks feature baffles, but many have large holes cut out to provide maintenance personnel access to the individual compartments. Within the outer compartments, some manufacturers install side-surge stabilizers along the walls to prevent water from rolling or churning. The number of compartments can vary between tanks.
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To offer the best level of water compartmentalization, these baffles require holes to allow water to flow freely throughout the tank, but they need to be small enough to prevent water from surging during use. To address this, some water tanks feature access doors that are about as tall as an average-sized worker to provide a more advanced solution than simply a hole near the ground in the baffle walls. These baffle doors, which technicians walk through easily, practically eliminate the need to crouch down while they maintain the tank, and the doors remain shut while the water tank is in operation, further restricting water movement between compartments.
To allow technicians into the tank for maintenance, some manufacturers incorporate external doors, which can provide fresh air and natural light throughout the tank after opening all of the external and baffle doors. When the tank is empty and the inside needs servicing, technicians simply enter the tank and open the baffle doors. This system offers easy service and maintenance, allowing technicians to access the inside of the tank safely and easily, instead of putting off the difficult work for later.
Having complete and easy control over their tank’s water output gives truck drivers control over their safety on haul roads. For instance, individually controlled spray heads help water truck drivers optimize their water usage as well as minimize the chance of oversaturating haul roads, which can create slick driving conditions. Inside the cab, operators can turn on the individual spray heads — and, in some systems, program a spraying interval. This optimizes water usage, so operators cover more surface area with minimal risk of making haul roads too slick for other equipment. Water metering controls contribute to overall safety by allowing the water truck driver to better focus on his or her surroundings while driving.