Mobile Crane Capacity: Understanding Key Factors for Safe Operations

When it comes to operating a mobile crane, safety should always be the top priority. One of the most critical aspects of crane operation is understanding the capacity of the machine. In this article, we'll explore some of the key factors that affect the load-carrying capacity of a mobile crane.

Soft Footing: A Crucial Consideration

The ground condition must have enough stability and bearing capacity to support all loads placed on it by the crane. Extreme caution should be used when performing lift operations beside buildings, especially if newly constructed with uncompacted backfill, along trenches, or in areas where water mains, sewer pipes or steam lines are buried.

Improper Use of Outriggers

If lifting on outriggers, the load chart rating applies only when all the outrigger beams are fully extended and all tires are clear of the ground. If these two conditions are not met, then the 'on rubber' capacity charts should be used. Additionally, some mobile cranes have load charts for mid-extended outrigger beams, which require the outriggers to still be extended to the proper point and all tires must be clear of the ground.

Unbalanced Rope Reeving: A Common Mistake

Unbalanced rope reeving occurs whenever the main hoist line is reeved to one side of the boom tip. This condition causes the boom to twist, which subsequently reduces the rated capacity of the crane. To avoid this, full chart ratings may only be applied when the boom tip is symmetrically rigged.

Proper Reeving and Load Chart Selection

On single-line reeving, when the hoist line runs along the center sheave or on the sheave beside the centerline of the boom, the boom twist is minimized. On multi-part reeved systems, if the parts of the line are evenly distributed on either side of the boom centerline, the boom twist will also be minimized. It's essential to check the manufacturer's reeving diagrams to ensure proper reeving.

Understanding Crane Configuration

Operators must know the configuration of the crane, ensure the configuration is correct, and use the appropriate load chart. This includes understanding the hoist reeving configuration, counterweights used, and whether they are configured according to the manufacturer's specifications, as well as the type of boom used, its length, and where the boom insert locations are.

Load chart ratings may only be applied if the machine is rigged according to the manufacturer's specifications. By understanding these key factors and following proper operating procedures, operators can ensure the safe operation of mobile cranes and minimize the risk of accidents or equipment damage.

Mobile crane capacity