Providing a stable platform for the excavator is an essential element of site setup. “The machine has to be on even ground and the ground has to be stable,” says Powell. “If the machine is already standing on a slight slope, this will affect all of the machine’s movements and its stability.”
“A rocking excavator is not a productive excavator,” Hendry comments. “As the excavator rocks forward on its idlers, it is putting added ground pressure on the banks of the trench. This can contribute to cave-ins. OSHA requires operators to be sure the excavator is at least 2 ft. back of the end of the trench.”
The weight of an excavator angles out in more of a pyramid shape, rather than straight under the tracks. “If you have an excavator that’s sitting right next to the edge of the trench, that weight distribution goes out at an angle, so you’re really resting on a couple of inches of support,” Cannon states. “As you’re digging, you’re creating vibration and the machine itself is vibrating, so you create instability, especially if the material has been worked before.”
As such, it’s critical to maintain a safe distance from the edge based on soil type. “If it’s not rock, you’re safe always assuming that it’s Type C soil,” Cannon says. “That requires that you be back the length of distance from the edge as you are height wise, so that you have a 1:1 ratio of support.”
Position the machine at a productive height for loading material. “The bench height should be about the height of the haul unit dump box sideboards,” says Hendry. “Set up for the trucks to come down the left side of the excavator, which is best for loading angle and visibility.”
Avoid digging from the bottom up. “This wastes time and fuel and can lead to under cutting the excavator,” says Hendry.
“You want to start out with the top layer, which is a marking path,” says Cannon. “Dig the teeth in just enough to mark the direction of the trench so it’s in alignment. Then, you can start gradually going down layer by layer, taking more out as you go down. That does a couple of things. It keeps the trench from becoming too large, and it also makes your efficiency better. You don’t have to go down to the bottom of the trench each time to pull material out.”
Long reach excavators require added caution. “When using long-reach booms/sticks on excavators, the operator needs to be aware that it is easier to dig the material out from under the spot where the excavator is sitting without knowing,” says Powell.
“The SLF operator has to be very skilled and patient,” adds Hendry. “If your operator gets in a hurry or loses focus, he/she will damage the machine. Each move of the boom/arm and bucket has to be deliberate. If your operator swings the house before the bucket is clear of the excavation, damage to the boom/arm will result.”
Don’t slide on slopes
Working on slopes presents some specific challenges. “There are always risks when working on slopes,” says Hendry. “Improper positioning and operation of the machine can lead to tipover.”
It’s important to take the right approach to the job. “The height and degree of the slope will dictate how you use the excavator,” says Hendry. “If the slope is tall, you will need to crawl up to the top and pull your grade down to the toe. Cutting a bench across the face for the excavator to sit on and pulling the grade from the top of the slope down to the bench is another option. The operator can reach down below the bench and grade the slope up to the bench.”
If the project requires working on the face of a hill, it’s important to consult the equipment operator’s manual to determine the safe operating ratios. “It’s very important not to exceed that,” Cannon stresses.
Position the tracks of the excavator straight up and down the hill. “You should never have your tracks going parallel to the slope, because if you start to slide, once the edge catches, it’s going to tip the machine over,” Cannon explains. “If the tracks are going up and down the slope, if something catches, you’re just going to roll over it.”