The best way to find the load capacity of a crane is to consult its load chart. Crane load charts explain a crane’s load capacity at different boom lengths and lift angles and show how the load capacity decreases as the boom length increases.
You typically find load moment indicators (LMI) or rated capacity indicators (RCI) on modern cranes. These devices enhance crane safety by warning you when your load exceeds the lifting capacity suggested by the crane manufacturer. Even if you have these features, it’s essential to understand the load chart.
In this post, we explain how to find the load capacity of your crane using a load chart, what to do if you don’t have one, and how to choose the right crane for your job.
Table of Contents
- How to Find the Load Capacity of a Crane Using the Load Chart
- Components of a Crane Load Chart
- 3 Ways to Find the Load Capacity of a Crane if You Don’t Have the Load Chart
- OSHA Standards for Crane Capacity
- How to Choose the Right Crane Capacity for Your Needs
- Rent a Suitable Crane from BigRentz
How to Find the Load Capacity of a Crane Using the Load Chart
Each crane model has a unique load chart. A crane may have one or multiple load charts based on its configurations. Load charts are typically provided by the manufacturer in the operator manual usually found in the cab of the machine.
Using this chart helps you create a lift plan that is safe from start to finish. Here’s how to use one.
1. Calculate the Load Radius
Most load charts will have a lift range diagram showing the load radius, which is the horizontal distance between the centerline of the crane’s rotation to the load. The shorter the load radius, the higher the load capacity of the crane.
Find the length of the boom that you’ll be using and the angle it will be positioned at on the diagram. Then, look for the corresponding number at the bottom of the chart to find the radius.
2. Look Up the Crane Lifting Capacity
Once you have the load radius, find it on the load chart and look across the chart to see the lifting capacity. Load charts will typically list both the gross capacity and net capacity of the crane, so you can see both what a machine is rated for as well as what its maximum capacity is.
Load charts also contain other information that needs to be taken into account when determining your crane’s lifting capacity. For example, the chart should state if the capacity is calculated over the rear or front of the machine or at a 360-degree rotation, and whether the machine is stabilized by tires or has its outriggers or stabilizers down. Factors like these all affect a crane’s net capacity, or the actual load it can lift.
Typically the lifting capacity at the rear or front of a crane is higher due to the machine’s structure and weight distribution. If you’re calculating the capacity from this position, you must make sure the boom stays in this position during operation or you could overload it.
Also, don’t forget to check the chart for the correct crane configuration (including any attachments or accessories in use).
3. Consider Environmental Factors
In addition to how the crane is being used, environmental factors are also considered on the load chart, such as ground conditions (the slope of the ground) and wind speed. Both of these affect the crane’s stability, which can affect its load capacity
Components of a Crane Load Chart
A typical crane load chart has a few key components:
- Lifting capacity: The total weight a crane is able to lift safely based on load radius
- Boom length: The length of the crane’s arm
- Boom angle: The angle between the boom and the ground
- Capacity deductions: Shows what weight to deduct for the accessories in use
- Operation notes: Covers considerations such as slope and windspeed
Crane load charts also usually have a bold line splitting them in half. This line separates the two major limitations on a crane’s capacity: structural strength and stability. Capacities below the bold line are limited by a crane’s stability, while capacities above the line are limited by the machine’s strength.
3 Ways to Find the Load Capacity of a Crane if You Don’t Have the Load Chart
A crane’s load capacity should always be calculated from the load chart—it’s the safest bet and the most foolproof way to ensure you aren’t overloading your crane. Load charts are created based on various configuration details from the manufacturer, details that are difficult to properly account for if you’re calculating from a formula yourself.
If you don’t have your crane’s load chart, these sources can provide the critical information you need.
1. Download the Operator Manual
If you don’t have the physical operator manual for your crane, check the manufacturer’s website. Many manufacturers provide operator manuals for their cranes online, which you can download and print. You should be able to find the load chart in the manual.
2. Contact the Manufacturer
You could also contact the manufacturer directly using customer service. They may be able to provide you with the load chart for your crane and might be able to find load charts for older models from their archives.
3. Hire a Professional to Conduct an Inspection
If you can’t find a load chart from other sources, you could hire a qualified crane inspector to inspect the crane and calculate its limits.
OSHA standard 1926.1417 states that if the manufacturer’s procedures are unavailable, procedures for safe operation (including lifting) must be developed by a registered professional engineer familiar with the equipment. This professional can also check the crane for damage or other safety issues.
OSHA Standards for Crane Capacity
If you’re using, buying, or renting a crane, make sure that you adhere to OSHA standards.
The United States Department of Labor Occupational Safety and Health Administration (OSHA) standard 1926.1417 states that cranes should not be operated beyond their capacity as indicated on the load chart. Doing so could cause structural or mechanical failure or cause the crane to tip over, which could lead to legal consequences as well as serious injury.
This standard also states that employers must ensure that operators understand a crane’s load chart and limitations and that the load charts are verified by a competent person. Additionally, the load chart (and other materials needed for operation) must be in the cab at all times for the operator’s reference.
OSHA standard 1926.1427 requires that crane operators are trained and certified to use a crane.
How to Choose the Right Crane Capacity for Your Needs
It’s essential to ensure you get the right piece of equipment for the job at hand. Here’s how to find a crane with the right lifting and load capacities for your needs.
1. Understand the Job Requirements
The most important step in choosing the right crane is to consider the type of load that needs to be lifted—you need to make sure the crane is capable.
At the same time, you want to make sure the crane you choose can handle the weight of the load. Choosing a crane that can’t do what you need, or can do much more than you need, wastes time and money.
You’ll also want to consider what height this load needs to be lifted to so you choose the correct crane boom length. You may need a longer boom to lift vertically, but if you’re lifting vertically within a small lifting radius, you may not need such a high load capacity.
Also consider the material you’re lifting. For example, liquid-filled tanks versus concrete blocks will require different equipment and accessories.
2. Assess Conditions at the Jobsite
Ground and weather conditions on your jobsite affect the capacity of the crane you use, mainly because they can affect the machine’s stability. Wind can be a major factor, especially if you’re working at higher lift heights—the higher they are, the more likely it is that the wind can sway the boom. Rough or uneven ground might require an all-terrain crane for safe operation.
Also consider the degree of mobility you need. If you don’t need as much lifting capacity, smaller cranes usually have more precision and are easier to drive around obstacles on the site.
3. Check Load Charts in Advance
Once you have a clear sense of your site and job requirements, look at the spec sheets and load charts of the cranes you’re considering. Make sure the crane you choose is capable enough and able to access the jobsite.
You should always choose a crane that has a capacity higher than what you need to lift your maximum load, so you have a safety net.
4. Consider How the Crane Will Be Transported
Different sizes and types of cranes have different transportation requirements, and some may need to be disassembled to be transported. Be sure to check any relevant city and state laws to see if you need permits to transport the crane, and what route it will need to take. If the jobsite is difficult to access, you may need to drive the crane.
Rent a Suitable Crane from BigRentz
If you’re looking for a crane rental, you’ve come to the right place. From mobile cranes to carry deck cranes to all-terrain models, the extensive equipment catalog at BigRentz makes it easy to find the best crane for your needs.