Cranes have been around in one form or another for thousands of years, and have been pivotal to modern construction and the structure built in our society. Today, the crane industry — employing thousands of people — is worth billions of dollars.
Cranes are very complex machinery that incorporate some of the latest technology, and operating a crane is no rudimentary task, as it requires a good deal of training and know-how — not to mention a steady hand.
Cranes are used in a variety of different industries, creating a robust rental market. The sheer number of cranes available can make selecting the right one for the job intimidating. There are all-terrain cranes, prized for their versatility, as well as rough terrain cranes, built for rugged worksites. Additionally, some cranes, like tower cranes, are designed to handle lifts hundreds of feet in the air, whereas some are made specifically for heavy lifts weighing thousands of tons.
Indeed, selecting the right crane from the dizzying array of options can be challenging. However, learning basic information about a crane’s utility makes the choice easier, and that starts with knowing how to interpret a crane’s load chart.
Load Charts and Their Importance
Simply put, a load chart is a summary of what a crane can and cannot do. It gives a brief overview of the crane’s capabilities and goes over the cranes’ features and characteristics, including the loads it can handle given certain specifications — lift height, lift angle, etc.
Most load charts include sections on boom length, boom angle, and lift range in addition to information on other important variables. An experienced crane engineer can interpret these factors in light of present circumstances to determine the viability of a given lift.
If the boom length, lift angle, and lift weight are not measured properly, the crane may fail.
Load Charts Rules and Regulations
For the above reason, Occupational Safety and Health Administration —commonly known as OSHA — considers load charts critical. OSHA requires crane operators to consult load charts before attempting a lift, and crane operators are required to know how to interpret load charts. The same requirements are demanded of all project supervisors and managers.
OSHA has published a wide variety of rules and regulations dictating where and how load charts must be displayed and what information they must contain.
According to OSHA’s regulations [i.e., 1917.46(a)(1)(i)(A), 1917.46(a)(1)(i)(B), 1917.46(a)(1)(i)(C)], load charts must provide:
- A direct indication in the cab of actual weight hoisted or a means of determining this by referencing a weight indication to crane ratings posted and visible to the operator, except that the use of a dynamometer or simple scale alone will not meet this requirement
- Indications in the cab according to the radius and load at the moment
- A direct means to prevent an overload from occurring
Interpreting a Crane Load Chart
Crane load charts may vary according to a few different factors, but they generally contain information related to the crane’s lift capacity, lift range, boom angle, movement, and deduction.
This measure tells you how much load can the crane lift considering the nature of the lift, the dimensions of the load, lift height, and lift angle.
Many load charts include a diagram illustrating the required boom length given the distance and lift height.
In mathematical terms, the boom angle is found between the longitudinal centerline of the boom and the horizontal centerline. The stability of the crane must be considered when determining the appropriate boom angle. If the crane tries to lift too large a weight at too large an angle, it may lose balance.
Cranes must often move or rotate to complete a lift. How far and at what speed a crane should rotate must be considered when ascertaining a lift’s feasibility. Some lifts require the crane to complete a full 360-degree turn. If movement is not considered, the crane may lose balance and tip over.
When determining how much weight a crane can lift at a given angle, the weight of the crane and its accessories must be deducted. These accessories include:
- The rigging
- The line
- The ball and jib
- The block
- The windspeed and windsail
The Bold Line
Most load charts are split in half by a bold line which serves an important function. A crane’s capacity has two limitations: structural strength and stability. The bold line separates capacities according to these limitations. All capacities listed on one side of the line are limited by the crane’s structural strength, and those on the other side are limited by the crane’s stability.
Now, You Ready to Read Load Charts
The modern crane has revolutionized the construction industry and made once impossible projects possible. New cranes incorporate the latest technology for improved efficiency and safety. However, if the proper precautions aren’t observed before use, a disaster may occur.
Consulting a load chart is a necessary step before using a crane. It tells the operator how to properly perform a given lift, reducing the likelihood of harm to person and property.
It’s important to consider the type of load, the weight, and the environment prior to selecting a crane. Hundreds of different types of cranes exist, and some are only suitable for certain kinds of jobs. Using an ill-suited crane increases the likelihood of property damages and puts lives at risk.
When searching for the appropriate crane, it’s best to consult a company that specializes in crane rentals. They understand the suitable differences between crane types and brands and can factor in elements such as weather, capacity, lift type, and the nature of the load. Once you select a crane, you can have the crane delivered to the worksite and hauled away when the job is completed.
No matter what type of crane you need, Maxim is happy to serve you at one of its 60 U.S. locations. Our easy-to-use website lets you browse hundreds of different makes and models according to crane load charts. Shop from our extensive selection of rental cranes today!