Overhead cranes are critical infrastructure for the industries which use them, including shipping, rail, freight, warehousing, metallurgy, paper production, heavy manufacturing, and any industry where heavy weights must be continually lifted in the same area. When an overhead crane goes out of service, it can bottleneck significant portions, or the entirety, of a company’s daily operations. This delay can result in a loss of revenue and profit. If it delays the eventual delivery of products, it can even impact contract renewals and future bids.
As with all heavy machinery, observing proper preventative maintenance and following correct repair procedures is essential to keeping overhead cranes functional and safe. Designed to support heavy loads and move along predetermined paths, overhead cranes depend on heavy bolts to handle the weight. The only way to ensure these bolts are tightened to the right degree is to use quality torque tools while maintaining or repairing overhead cranes.
Preventing Overhead Crane Downtime with Accurate Torque Control
Overhead cranes are subject to large, dynamic stress loads. They continually lift, move, and lower heavy loads throughout their time in operation. These loads apply force in different amounts, from different angles, to the structure of the crane, including on the nuts and bolts that hold the crane together. At the same time, overhead cranes are subject to vibration from their motive units and changing temperatures and humidities, whether they’re exposed to the elements outside or inside hot steel refineries and other metallurgical plants.
These stressors can cause individual parts of the crane, such as the nuts and bolts, to fail. When even a single part fails, it increases the amount of stress on the other parts of the mechanical system. In turn, this ups the likelihood that other parts, pushed beyond their tolerances, will fail. If an overhead crane fails, a business will suffer from the crane’s unproductive downtime and will have to pay for repairs to the crane and any other equipment damaged or workers injured by a falling load.
Any system is only as strong as its weakest point. If the nuts and bolts that hold overhead cranes together aren’t torqued to the right amount, they can become failure points, weak enough to fail even when working within weight tolerances. These tolerances, after all, are specified on the assumption that the nuts and bolts in cranes have received the proper torque during assembly, maintenance, and repair.
The amount of torque applied to nuts and bolts determines their effectiveness and capacity. If less torque is applied than is called for, the bolts can work free under stress, vibration, or expansion and contraction due to shifts in temperature. If more torque is applied than recommended in the designer’s specifications, then a bolt’s threads can be crimped or damaged, and the bolt’s shaft can shear, deform, or warp. Bolts weakened by over-application of torque are more likely to fail under stress, even amounts of stress that are supposed to be safe.
Choosing Pro Torque Tools for Overhead Crane Maintenance and Service
In order to apply the correct amount of torque to a nut or bolt, a maintenance or repair worker must use a tool which can detect and limit the amount of torque applied. This tool must also be able to apply enough torque to meet the demands of the large fasteners used in overhead cranes. Finally, it must be sturdy and dependable, able to stand up to difficult environmental conditions.
Hand torque tools, like click torque wrenches and cam-over torque wrenches, can both be used to effectively to maintain or repair fasteners on overhead cranes. Click torque wrenches provide more power than cam-over wrenches. However, they don’t physically prevent their operator from applying too much torque, relying instead on an audible “click” to tell their user when to stop. Cam-over wrenches, while less powerful, have an internal clutch mechanism which disengages when the designated amount of torque is reached. This removes any chance of over-torquing a bolt.
Many bolts in overhead cranes may be too heavy for cam-over wrenches, and some may even be beyond the range of click wrenches. For these bolts, repair and maintenance workers can turn to hand, pneumatic, or electric torque multipliers, all of which significantly increase a tool’s torque output while maintaining accuracy. Hand torque multipliers are the simplest and most powerful, but they are also slower than pneumatic or electric multipliers. Pneumatic and electric multipliers operate at similar speeds (both of which are much faster than hydraulic ratchets), but pneumatic multipliers can provide much more torque, almost as much as hand torque multipliers. Pneumatic and electric torque multipliers are limited by their need to be near compressed air or AC power, respectively.
Companies which rely on overhead cranes have little tolerance for unplanned equipment downtime. Likewise, the nuts and bolts which these cranes rely on do not tolerate over- or under-torque conditions. By using powerful, accurate torque wrenches and torque multipliers, repair and maintenance personnel working on overhead cranes can be sure that their equipment is ready to carry the weight.
