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Understanding Crane Lifting Capacity (How to Read a Load Chart)

Understanding Crane Lifting Capacity (How to Read a Load Chart)

Cranes have been in use on construction sites for millennia. Being a contractor is all about planning effectively. You have to plan every aspect of your project, from start to finish and beyond; regardless of the size of the project, the details matter. 

If a crane is expected on a job site, everyone involved, from the operators, supervisors, and planners, needs to know the chosen equipment capabilities and limits.


Understanding Crane Lifting Capacity

The first step in understanding crane loads and determining what machine you need on site is to accurately determine exactly what you need to lift. How heavy it is, and where you need to lift it from and to. 

When it comes to jobs that require cranes, one of the questions your crane rental company will ask is the total weight of the load. You need to know several things about calculating a load's weight before you rent a crane. This is especially relevant if you plan on performing a critical lift, a lift performed at 75% or more of the crane's capacity.

Calculating Total Load

Load calculation refers to the way in which you determine how much weight the crane will be lifting. While it can be relatively straightforward, at times, you will need to do some math and work with formulas in order to find the number your crane rental company will need.

Load calculations should take into account the weight of everything being lifted, including:

  • All lifting gear
  • Hooks and rigging
  • Ropes and harnesses
  • Construction materials on the load

These weights need to be as accurate as possible. Manufacturers are an excellent source for this information for individual parts that you can then add together. 

You can also physically weigh an example load using an industrial scale. It is worth investing in a dynamometer to allow you to measure each load before each lift. These devices can be attached directly to the rigging to give you an accurate measure.

How to Read a Load Chart

Once you have your measure of load weight, it is time to start looking at load charts and determining if your crane can operate safely under given parameters. Cranes have a maximum load, but that can only be reached under optimal conditions, which rarely occur on site. Ground stability, physical obstructions, and weather can affect a load

Every crane model will come with its own load chart. Review each section carefully to ensure you understand the machine's capabilities and limits.

1. Dimension and Weight

The first thing to look at on the load chart is the specifications concerning the crane itself. Each chart will show the dimensions and weight of the crane itself, along with information concerning standard operation features like outriggers. 

This data is crucial for understanding how the crane will sit on the site and determining any space constraints and special considerations for site prep. If you need to work in a severely confined space that won’t allow the use of outriggers, that will significantly influence the stability of the crane and lower the maximum capacity.

2. Effect of Lift Range and Angle

Before you get into looking at what your lift load capacity is, you need to understand how you are going to be moving the load. Lift range is the determination of how far the boom is going to need to extend to pick up and lift a load taking into account distance and height.

For every lift, you want to carefully calculate this and select your max capacity based on the furthest range of extension that will be required.

Cranes rarely lift loads straight up and down. Lift angle plays a significant role in determining maximum lift capacity as well. 

The greater the extension of the boom arm, the higher the angle needed for a lift to be completed and the lower the maximum capacity. This angle places strain on the stability of the crane itself, and exceeding lift angle capacity greatly increases the chances of tipping.

3. Lift Capacity

Once you have knowledge of what you would like to lift and the path it will take. You can use that load information, range, and angle planning to determine if you can safely operate within the crane's lift capacity. Follow the respective informational axis for distance and angle, and the load chart will indicate the appropriate maximum load weight. 

Remember that this lift capacity is representative of the ideal lift. That means a situation with fully extended outriggers, perfectly prepped ground, minimal obstructions, and non-inclement weather. For this reason, if you are planning a lift that exceeds 75% of the determined lift capacity, a critical lift plan must be formed and followed. 

A final factor that must be taken into consideration is at what speed you will perform the lift. Any movement, including winds, adds additional forces onto the load, which you will need to include in your calculations. 

Selecting the Right Crane

No matter the job, using the right tool makes all the difference. Make sure you select a crane that fits your job site requirements for the safest and most effortless experience. 

Serving the Carolinas for over 40 years, Parker’s Crane Service can help you get equipped with the right crane for the job. With a fleet of well-maintained hydraulic truck cranes, we offer not only the best equipment but can help with:

  • Pre-lift Job Assessments
  • Daily Risk Assessments
  • On-site Hazard Analysis
  • Routine Management Audits

Our crew is OSHA and MSHA compliant to ensure your site and crew safety. Browse our list of available cranes to see if we have the right crane for your job. And contact our team to discuss any services or equipment we can help you select for your project.