It’s digging season and your compact excavator is getting a workout. But did you know that one of the most frequent — and often overlooked — jobs performed by excavators is lifting?
On a typical jobsite, excavators may be used to lift, move and place a range of materials. Learning to lift safely is critical for anyone who owns or operates an excavator. Let’s begin with the basics.
Two Factors That Limit Lifting Capacity
The lifting capacity of any compact excavator is limited by two factors: hydraulic capacity and tipping capacity. Hydraulic capacity is the point at which the excavator runs out of hydraulic power, or stalls. Tipping capacity is just that — the point at which the excavator begins to tip or lift off the ground.
Manufacturers test excavators to determine how much weight they can safely lift at various heights and distances from the centerline of the machine. Based on these tests, they create lift charts, which are printed in the machine’s Operation and Maintenance Manual and posted within sight of the operator, such as on the canopy, cab roof, hood or window.
How to Calculate Lifting Capacity
1. Find your excavator’s configuration.
Your excavator lift chart provides information that will keep you safe and get the job done right. At the top of the chart, you’ll find information indicating the machine configuration. For a compact excavator, this may include boom length, arm length, the weight of the standard bucket and weight of the quick coupler, if standard. Published lift capacities assume the excavator is on a flat, level working surface.
Typically, lift capacities marked with an asterisk are limited by the machine’s hydraulic capacity and do not exceed 87 percent of test. Lift capacities without an asterisk are limited by the machine’s stability, or tipping capacity, and do not exceed 75 percent of test.
2. Determine the lift point height.
Next, look at the far left column on the lift chart to determine the lift point height — the distance from the ground to the bucket pivot pin, NOT from the ground to the object you’re lifting. When you’re measuring the lift point height, consider how high you will need to lift the item, including the height of the item itself, the length of the lifting device (such as chain or sling), and at what height you want to place the item. (Is it going on a trailer? A scaffold?)
3. Find the lifting radius.
Now determine the lifting radius from the centerline of the swing point. This distance is shown in the top row of the lift chart. Are you lifting over the front of the excavator or over the side? If you’re using an excavator with a dozer blade, determine if it will be in the raised position to allow travel or in the lowered position to optimize stability.
4. Calculate your lifting capacity.
You can now find the cell on the lift chart where the lift point height and lifting radius intersect. This number is the excavator’s lifting capacity. If there is no number listed, the excavator has no lifting capacity and the lift should not be attempted.
Generally speaking, as your lifting radius increases, the lifting capacity will decline. Also, lifting over the side is generally more limited than lifting over the front of the excavator.
See how a Bobcat excavator’s lift capacity stacks up to the competition.