A Guest Post from the Members of the Electrification and Controls Manufacturers Association (ECMA).
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Overhead cranes are essential equipment for many industries, including manufacturing and logistics. But in order for cranes to lift and move heavy loads within a facility, they need power. There are three primary crane electrification options: conductor bars, festoon systems, and cable reels. Each offers both advantages and disadvantages, making them ideally suited for different types of overhead cranes and applications.
Helping overhead crane owners and prospective buyers better understand their crane electrification options are the members of the Electrification and Controls Manufacturers Association (ECMA). The group publishes the American National Standard (ANSI) ECMA 35: Electrification Systems for Electric Overhead Traveling Cranes. This standard details minimum requirements and guidelines for both alternating current (AC) and direct current (DC) electrification systems used to power overhead electric cranes, monorails, gantry traveling cranes, and workstation cranes.
“All three types of crane electrification options — conductor bars, festoons, and cable reels — serve the same purpose,” explained Ben Hiebenthal, Mechanical Engineer III and Platform Lead of Rotary Motion Products at ECMA member Conductix-Wampfler. “They all provide power to the crane and its components. They each are simply different modes, or ways, to deliver electricity to the moving overhead equipment.”
The different form factors exist to accommodate different application limitations, Hiebenthal continued. “Often, what dictates the choice of which crane electrification option to use is the available space that surrounds the equipment. Each has different space requirements and, in many instances, a combination of two or more options is the optimal solution,” he said.
For that reason, Hiebenthal advises operations considering a new overhead crane to review ECMA 35. He also recommends engaging a crane electrification supplier early in the design process.
“Electrification is often an afterthought when a facility is planning a new crane purchase,” he said. “For the most cost-effective solution, an electrification supplier can advise about the amount of space required around the machinery to adequately support the power supply. They can also help to guide the selection of conductor bars, festoons, and/or cable reels individually or in combination to best suit the application.”
Conductor bar systems are a popular method for electrifying overhead cranes and their hoists. These systems generally consist of four linear bars (three live, one ground), collectors, and all mechanical components for installation. The collectors travel along the length of the bars as the crane moves to supply power to the crane and its components. Protective guarding options and grounding systems keep personnel safe from unintended contact.
“Inside a building, conductor bars are commonly mounted near the ceiling along the entire runway,” he said. “They’re also frequently mounted on a bridge to power the trolley’s movement back and forth across the crane.”
Conductor bars offer several advantages for overhead crane electrification. First, they provide a continuous power source to the crane, which eliminates the need for frequent stops and starts. This results in smoother and more efficient crane movements, as well as reduced wear and tear on the equipment.
Another benefit of conductor bars is easy customization. Options include different amperage ratings, voltage levels, and insulation options, depending on application requirements. “Some even permit transmission of data signals over the same bar used to transmit power,” Hiebenthal noted. “That can reduce the number of conductor bars needed on the crane.”
Additionally, conductor bars can be mounted for bottom or side collector entry to accommodate different crane designs and layouts. That makes them ideal for facilities with low ceiling heights. “While their sliding collector shoes do need adequate space to stack up at one end of the crane, they generally take up less space than festoons and cable reels,” he added.
Like all crane components, conductor bars require maintenance and inspection. Over time, the sliding contacts or collectors can wear down or become dirty, affecting their electrical conductivity. Regular cleaning and inspection of the conductor bars are necessary to ensure optimal performance and prevent downtime.
Festoon systems are another frequently used overhead crane electrification option. A festoon system consists of a series of power cables suspended along the crane runway or bridge managed by trolleys. The cables drape between each trolley; as the crane moves, so do the trolleys, which extend the cables, feeding out the slack. When the crane or bridge returns to its starting position, the trolleys retract and stack back up — accordion style — to compress the loops of cable.
Festoons are flexible and easily customized in terms of length and the number of cables needed to support the crane’s movement through a work area. They are also relatively easy to install and maintain. They do, however, require more storage space for the trolleys and cables, said Hiebenthal.
“The longer the travel distance of the runway or bridge, the longer that collection of cables will be and the more space you’ll need to store them,” he said. “Additionally, in a low headroom area, a festoon system can be problematic if the loops are hanging into a work cell under a jib crane, for example.”
Festoon systems, like all crane components, require routine maintenance and inspection. The cables, because of their continuous extension and retraction, are more susceptible to wear. Likewise, depending on the environment, they can be more prone to damage.
Cable reel systems are another common option for overhead crane electrification. These systems consist of a cable wound onto a spool and connected to a power source. As the crane moves along the runway or bridge, the cable unspools from the reel and provides electrical power to the crane. As the crane returns, the reel system automatically retracts the cable either with a spring or motor and winds it back onto the spool.
One of the main advantages of cable reel systems is their ability to provide a continuous power source to the crane. Cable reel systems are also relatively easy to install and maintain. As long as there is adequate space to house the spool, mounting for this system can be above, below, or alongside the crane.
“The downside to a cable reel system is that they typically only manage one cable,” Hiebenthal noted. “In some special circumstances, it may be possible to wind two cables on the same spool, but that can limit the diameter of the cable. So if a system needs multiple cables, a cable reel system is probably not the best choice.”
Further, an exceptionally long travel distance for either the runway or bridge will require an exceptionally large reel system. That may not be practical, space efficient, or cost effective, he explained.
As with conductor bars and festoons, cable reel systems also require routine maintenance and inspection. The cables can be more susceptible to wear and damage, depending on the operating environment. Additionally, there is a chance that the cable could become tangled on the reel if the system is not designed and managed properly.
Want to learn more about overhead crane electrification options, including conductor bars, festoons, and cable reels?
Ask the members of the Electrification and Controls Manufacturers Association (ECMA), the industry’s leading suppliers of electrification and controlling devices. They supply solutions worldwide and in virtually every major manufacturing and distribution sector. ECMA members manufacture and distribute equipment that controls, services, and enhances productivity and safety in industrial handling, including remote controls, anti-collision devices, weighing solutions, brakes, resistors, cabling, drives, motors, festooning, and more.
Overhead cranes and hoists are terms used interchangeably despite both having key distinct differences.
While a hoist and overhead crane may seem similar, it’s essential to understand the differences between the two. This will help you choose the best mechanism for lifting loads. It’ll also help with maintenance needs, whether it’s what action to take yourself or knowing the best way to communicate your issues with someone else.
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So, with all that in mind, let’s take a closer look at the differences between overhead cranes and hoists.
The main difference between an overhead crane and a hoist is their movement patterns. Overhead cranes transfer bulky loads from side to side or up and down. They move both vertically and horizontally. On the contrary, hoists lift items up and down only on the vertical axis.
Additionally, an overhead crane is the structure and a hoist is mounted onto the crane (fixed or mobile).
A hoist is specifically designed for lifting heavy loads up and down. This is all you need for a mechanism like an elevator, making a hoist a perfect solution in the right circumstances.
An overhead crane allows you to move heavy loads up, down, and sideways.
A hoist is a component of overhead cranes which allows for vertical movement. An overhead crane’s horizontal movement is created through bridges and a trolley.
Top running cranes have a track system or fixed rail installed on the top of each runaway beam. The end trucks can carry both the bridge and hoist along this runway system. These types of overhead cranes can be built with a single or double girder design. A double girder will allow your crane to carry heavier loads but may be an unnecessary expense if you deal in lighter loads.
Often referred to as an under-hung crane, wheels connect the bridge to the bottom flange of the runway. Usually, this type of crane uses a single girder and is used for lighter loads.
The distinguishing feature of a gantry crane is that it is supported by legs that are either on wheels or rails implanted in the ground. These are commonly seen in outdoor areas or for lifting below an existing overhead crane system.
A monorail crane operates on a stationary track that the trolley moves along to carry loads to predetermined locations. Perfect for linear tasks that you’ll frequently repeat (a factory setting, for example) and, in this scenario, can increase productivity.
When differentiating hoists, each type can be defined by three categories: Lifting medium, power, and suspension. Let’s take a closer look at these factors:
Various materials can be used for a hoist. The lifting medium refers to the flexible material connecting the overhead body of the hoist to the load hook. Some of the most common lifting medium materials include:
Hoists can be powered manually, pneumatically, hydro or with electric motors. Here’s a brief rundown of each option:
A manual hoist will utilize a gear system and pulley to provide extra lifting power.
A wire rope hoist will lift heavier loads off the ground.
Powered by electricity, there’s a convenience factor not found in a manual hoist (especially when used frequently).Overheating an electric motor is risky, especially if you exceed the recommended weight limit or frequency with which you use your machine. To avoid this, it’s best to find an electric hoist powerful enough to suit your needs.
A pneumatical (or air) hoist is powered by compressed air. These are best suited in work environments that already have compressed air power available. (Mining, small workshops)
The best way to power your hoist will depend on your situation. A factory with plenty of air tools would be a perfect place to use an air-powered hoist, whereas this would be impractical in other places. Consider what you’re using your hoist for and how often to help determine the best type of power system for you.
Now that you understand the difference between overhead cranes and hoists, learn how to extend the life of your machinery with wire rope maintenance. Proper wire rope care is vital for rope health and safety.
For example, regular wire rope maintenance and lubrication help prevent serious and expensive damage to your lifting equipment down the line while extending its life expectancy.
Keeping an eye on your ropes for any frays, splits, or damage could be the key to catching a potential problem.
How you look after your ropes when you’re not using them can be just as important when it comes to expanding their service life.
Whether you work indoors or out, it won’t take long for dust, mud, and debris to build up on your ropes which will affect their functionality and cause damage.
Lubricating your crane wire ropes helps them to function properly and extends their lifespan significantly. The best wire rope grease needs to be light enough to penetrate towards the core of the rope but pliable enough to adhere to the surface.
A wire rope lubricator will help prevent corrosion, reduce friction, and help your ropes last longer by ensuring the lubricant can penetrate effectively. The Viper WRL Mid MKII range of wire rope lubricators, which will provide a safer, easier, and more efficient way to maintain your wires.
Whether you’re looking for a more straightforward and effective solution for your wire rope lubrication or want to learn more about our range, get in touch today.
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