How Do You Compensate For Boom Deflection?

Crane boom deflection is a normal phenomenon when heavy load lifting occurs; therefore, when the boom appears to bend, it absorbs the force of the weight. All crane designs, hydraulic and lattice, incorporate the potential boom flexibility within a limit. This boom deflection, generally calculated in inches, must be managed and controlled for technical and safety purposes.

The crane operator needs to manually adjust the boom position to compensate for radius changes that will affect boom deflection. However, with a lift adjuster system, this process is automated, and the system can sense deviation and adjust the hoist cylinder to compensate for boom deflection.

Experienced crane operators can manage the boom deflection manually. Still, with the modern demand for work output and technology development, crane designs include computer and mechanical enhancements to assist with boom deflection control and management. So, how do you compensate for boom deflection, and what are these technologies to aid in the crane lifting operation?  

Compensating And Managing Boom Deflection

Deflection is when there is a deviation from a set course; therefore, for overhead cranes, it relates to the horizontal or vertical variation of the boom when under load. This deviation or deflection of the crane boom can be configured and managed. It stands to reason that when you can calculate something, you can control it by manipulation, either manually or with technology.

What Happens When Lifting Weight With A Crane?

Crane booms can elastically and safely bend within predetermined degrees without risking damage to the structure or compromising safety. However, crane operators must be constantly aware of the lifting and movement process to pre-empt any deviation and allow for compensation.

First, adhere to the crane specifications. All cranes have a safe working load defined in their load specifications. The first requirement is to ensure you do not exceed the crane’s load capacity. Although modern extendable crane booms are solid and lightweight, they will flex more as they extend and can cause problems when not adhering to the max load specifications.

Second, control the swinging motion. As the weight leaves the floor during the lifting process, the boom deflection will cause the load to swing away from the crane. In addition, as the boom extends and the deflection increases, the load’s tendency to sway away increases. Therefore, you should always ensure that there is room to allow for possible swinging cargo.

In addition, you need to limit the swinging as it can build momentum and cause crane instability when the radius increases with the additional motion force on the crane and boom. Again, adhering to the crane specifications is essential as the load swing risk will be about the crane size, allowable radius, and load weight.

Third, manage the boom-up and hook rise. While lifting a load, you should control the boom-up in conjunction with raising the load. The purpose is to keep the boom head directly over the lifting weight. Similarly, when the operator lowers the weight, the boom down function and lowering of the load should be closely vertically aligned.

While considering the crane’s limitations and load capacity, understand that the less weight it can carry if winching a load further away from the crane center. In addition, longer or extended crane booms will deflect more because the weight is further away from the crane’s center.

Fourth, anticipate the boom deflection. Although boom deflection is in inches, it is essential to predict the flex compared to the surrounding structures. For example, a flexing boom with a swinging load can cause havoc when making contact with a building side. Thus, consider the surroundings when planning a load lift.

Similarly, the relaxing boom will need space to return to its original unflexed position once the load touches the floor and is released. For example, when you operate in small areas, take cognizance of ceilings or overhead beams and allow the boom to unflex. You can compensate for it by lowering the load slowly and boom down simultaneously before the weight touches the ground.

Fifth, don’t be too hastily. Lifting or lowering a load too quickly will cause excessive load motion, resulting in increased swing and boom elasticity. In addition, dropping a load can create an instant crane boom release reflux that can damage the crane and the boom.

Using Technology To Manage And Control Boom Deflection

Technology plays an integral part in managing and controlling crane boom deflection in the modern world. Without it, the crane operator would rely on ultimate awareness and perfect reflexes to mimic the effects of technology. The lift adjuster, for example, is a system that technically controls the crane load operation while the operator monitors the movement of the loads.

The system will sense any boom deflection and can compensate for radius changes by adjusting the hoist cylinder. In addition, it manages the load to move in a vertical line from the moment the cargo leaves the ground. Therefore, minimizing boom flexing and reducing deflection. As a safety feature, it will stop the moment when reaching the safe-load torque.

Thus, without this feature, the operator must manually compensate for deflection by constantly adjusting the boom position. Once the load is in place, the operator lowers and releases the load. Again, while ensuring the safety of the surrounding area, the boom, without the load weight, will flex back to its original position.

How Much Boom Deflection Are Allowed?

All crane booms deflect while holding the load, so their design and material will set an allowable deflection factor. This flex tolerance is typically calculated in inches as a fraction of the boom span. Therefore, you can calculate the potential deflection by dividing the span length in inches by the crane deflection limit specification.

In essence, the level of flexibility depends on the load weight, the span, and the rigidness of the boom.

In addition, short-boom cranes do not need to allow deflection as it does not affect the crane’s load abilities. However, the deflection factor increases with long-boom cranes, and you should always consider it in controller design and load capacity.


All crane boom can deflect within a limited allowable range; therefore, the crane operator constantly adjusts the load hoisting and boom extension to compensate and control the deflection. With technology, a lift adjuster system can assist the operator by automating this task, allowing the operator to monitor and manage the load operations more effectively.


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