Achieving maximum production from your loading operation requires loader and truck operators to work in concert. Spotting of the truck relative to the loader is critical to productivity and cycle times.
"Generally, the truck would be horizontal to the digging position of the loader and set back at a distance that would allow the operator to hoist and dump at the same time to the dump position," says Dave Pooley, Hyundai.
Keeping the distance between the loader and the truck as short as possible boosts productivity. "The shorter the distance the loader must travel to the haul truck, the faster the operator can return to the pile for the next load," says Bryan Evans, assistant manager - training, Doosan Infracore America. "As the pile reduces, the loader operator must adjust the spot of the haul truck to maintain maximum cycle times."
Several companies have researched the precise placement. "Studies show that the ideal placement of the truck should be about 65 ft. from the stockpile so that the wheel loader can operate in a ‘Y' loading cycle between the truck and the pile," says Georg Seyrlehner, general manager - earthmoving product management, Liebherr Construction Equipment. "This reduces the possibility of a collision between the loader and truck, and maximizes the fuel economy and productivity of the loader by limiting the operating distance."
Alternatively, the trucks can be backed into the pile. In this case, the truck should be backed in as close to the pile as possible. "The further that truck is away from the pile and the loader, the further the loader has to travel to load the truck, costing additional time and, ultimately, production," says Matt Weaver, medium wheel loader marketing, North American Commercial Division, Caterpillar.
You need to make sure your loading operation is set up efficiently. Caterpillar estimates a basic cycle time (load, dump, maneuver) of .45 to .55 minutes.
This cycle time can be influenced by several factors. "The surroundings of a stockpile can hinder load operations, especially if other machine traffic is involved," says Evans. "Ensure the surface of the operating area is free of obstacles such as holes, fallen materials and material spillage."
Match loaders to the task
"Two things are important when sizing a loader to a truck: one is dump height and the second is bucket size," says Pooley.
"Either you select a truck to fit the machine, or you select the loader to fit the haul fleet. All manufacturers give load charts and material density charts to match bucket to machine."
To calculate bucket size, divide the volume required per cycle by the bucket fill factor. "A high fill factor naturally means more material can be moved per cycle," says Seyrlehner. "Factors affecting this are bucket shape, the material to be moved and the rollback angle of the bucket. Deeper buckets on machines that have a higher rollback at carry height will move more material."
The bucket size required and the material density will determine the correct size loader. When performing the calculations, always select a wheel loader with a greater capacity than you calculated. Excessive counterweights and running a machine above capacity will reduce component life and negatively impact stability.
"We don't recommend ballasting because it is a sign that the loader has been improperly sized," says Seyrlehner.
If added weight is required, Seyrlehner advises using Calcium Chloride (CaCl) in the tires as the preferred method, rather than adding physical weights to the loader, because it keeps excess weight off of the machine itself and will result in lower wear on the axles.
In some applications, ballasting can offer additional traction to prevent wheel spin in extreme conditions, as well as additional stability. "Today's modern machines have minimal slippage due to options of differentials, such as posi-lock, limited slip or lock up," says Pooley. "But some applications that involve slippery conditions for greater periods may require that ballast be put into the tire. This does help to keep traction.
"[Using a liquid ballast in the tire] is a tried and true method that can be reversed easily by draining the liquid cocktail out," Pooley adds.
Caterpillar suggests there are advantages to using RV antifreeze as a tire fill instead of CaCl. "RV antifreeze is recommended, since CaCl corrodes rims," says Weaver.
Housekeeping boosts productivity
It is also important to keep the load floor in front of the pile. "Cleaning the floor serves several purposes," says Weaver. "First of all, a clean load floor saves on tire wear by reducing cuts. Second, a clean load floor allows consistent cycle time to be maintained much more easily."
Cleanliness equals speed. "The operators can maintain a higher cycle speed because they are not being jarred around in the cab from uneven terrain. It also helps them retain material in the bucket once it has been loaded by minimizing spillage from jarring," says Seyrlehner.
The wheel loader should stay in motion. "Don't stand idle," says Evans. "Prep the load area and prepare for the next haul truck. Assist the drivers to position by communication for optimal cycle times and proper position."
Cleaning the platform is also very important, and does affect cycle times. "Cleaning the platform allows for a level surface and reduces the possibility of tipping and machine damage, not to mention a reduction in spillage," Evans explains.
Train operators on features
It is also important to understand any productivity-enhancing features. "Operators may not know the correct operating procedures for the unit they are using," says Pooley. "An example would be using the clutch cut-off device for a better transfer of available horsepower when digging and loading."
Other popular features include return to dig and return to carry. Proper training on the use of these features can increase productivity. "Special features such as return to dig and return to carry do assist the operator, reduce fatigue and can have a positive effect on production and cycle times if the features are properly used," says Evans. "There are operators who do not like these features because they have not been trained to use them effectively."
It is all about correct positioning. "These features take the guesswork out of the return-to-dig and return-to-carry positions, so that when the operator goes to the pile, he is in the correct position for loading," says Pooley. "It does help in fatigue, as well."
Consistency is the biggest benefit. "While these features certainly minimize operator fatigue, they allow high levels of consistent production to be maintained throughout a working cycle by automating some of the respective portions of the cycle," says Weaver.
In addition, don't downplay the role of operator comfort. "Operator comfort is the key to productivity," says Pooley.
Comfort in seating, climate control, ergonomic controls and a good radio/CD player all contribute to the productivity."