Overhead cranes, like all equipment, have benefits as well as disadvantages.
- Some of the disadvantages of an overhead crane include price and size.
- Some of the advantages of an overhead crane include safety and efficiency.
- There are many different types of overhead cranes.
What Is an Overhead Crane?
In the simplest terms possible, an overhead crane is a device, or piece of machinery, that enables you to lift and transfer heavy objects from one place to another.
Overhead cranes can be designed and built in a variety of configurations with various components swapped out or engineered to increase capacity and performance. Some of the most common reasons for using an overhead crane are as follows:
- Loading or unloading materials
- Transporting materials quickly and efficiently
- Flipping or pulling dies into and out of stamping machines
- Feeding raw materials into a machine
- Moving pieces or parts down an assembly line in a controlled manner
- Moving containers around a shipyard or railyard
There are many different types of overhead cranes and each one is specifically constructed and engineered for a specific purpose or application to meet a company’s material handling demands.
In this article, we will be discussing the pros and cons of using an overhead crane on the worksite. We will also be discussing the different types of cranes that are available to you and their unique features and uses.
Disadvantages of Using Overhead Cranes
Now that we have discussed what exactly an overhead crane is, we will dive into the different disadvantages that are associated with them. We will also discuss why some companies or business owners choose to use different types of equipment instead of an overhead crane.
Compared to other types of heavy lifting equipment, cranes generally have a pretty high price. So when it comes to choosing between a crane and some other equipment, the upfront cost often creates some hesitation and concern.
The other disadvantage to using an overhead crane in your workplace is how much space they take up. Overhead cranes are typically much larger than other equipment options. If an overhead crane is initially built into the facility, it is typically supported by the building’s infrastructure. However, if the crane is freestanding, it will necessitate the installation of support columns throughout the facility, which can take up a significant amount of space.
Due to the large size of overhead cranes and the way they are built into the structure of a building, moving a crane from one facility to another is extremely difficult, if not impossible. In some cases, the overhead crane is even included in the lease agreement for a building.
Advantages of Using Overhead Cranes
Now that we know the few disadvantages to overhead cranes, let’s discuss the different ways that overhead cranes benefit you, the company, and the facilitated operation.
It is not unusual for an overhead crane to last up to 65 years. This is due to the fact that overhead cranes are generally built specifically for the operation at hand and are less prone to damage than other equipment.
Another advantage of using an overhead crane in a manufacturing, assembly, or warehousing facility is that cranes can handle corrosive or dangerous materials. Some of these materials could include hot metals, chemicals, and heavy loads. Overhead cranes can be used to lift and move these materials in extreme environments. Some cranes can be installed to assist workers in moving heavy objects in a controlled manner, reducing repetitive motion injuries and muscle strains.
Overhead cranes have significantly higher potential load capacity than other heavy lifting equipment. Overhead crane lifting capacities can exceed 400 tons. Going along with that, regardless of how high or low the load must be lifted, overhead cranes maintain the same capacity.
Overhead cranes can work up to 2-3 times faster than a group of workers or tow motors to lift and move material. Consider how an overhead crane can help a manufacturer, mill, or warehouse streamline processes and procedures by automating the lifting, maneuvering, and unloading of materials at their facility.
Maintenance on a Crane
Performing maintenance on heavy machinery comes with the territory of working with heavy machinery. To some, it may be considered a disadvantage, and to others, it may be considered a benefit. Regardless of how you see it, maintenance is important.
Your overhead crane, like any other piece of equipment or machinery, will require regular maintenance to extend its life and keep it running efficiently. The following are some of the most common maintenance issues that come with overhead cranes.
Damage to the Rope
Damage or degradation of wire rope is one of the most common problems with an overhead crane system. There are several common wire rope issues, including the following:
- A wire rope has jumped the reeving system
- Loss of core support of the wire rope and internal or external corrosion
- Outside wires that are broken or worn
- End connections with corroded or broken wires
The life of wire rope can be influenced by a variety of operating conditions. Bending, stresses, loading conditions, load application speed, abrasion, corrosion, sling design, materials handled, environmental conditions, lubrication, and usage history will all influence how long wire rope can stay in service.
Alignment & Stability
An overhead crane that is out of alignment can put significant strain on the crane system as a whole. The problem with a crane that isn’t tracking properly is that, over time, forces that weren’t accounted for in the overhead crane’s design and installation cause stresses to the runway beams themselves as well as the tie-backs or building support structures. These kinds of stresses can lead to:
- Failure or derailment of a crane
- Downtime of equipment and loss of productivity
- Pricey repairs and replacement of parts
A crane that isn’t tracking properly prematurely wears out the wheels, wheel bearings, and wheel flanges, as well as the motor drives and other equipment.
There are several issues with an overhead crane’s electric system that may necessitate service or future maintenance:
- Contact interruption issues: These contact interruptions can lead to intermittent control issues with the overhead crane system.
- Problems with radio controls or push button pendants: Although uncommon, some environments produce their own radio waves that can interfere with the operation of an overhead crane.
- Blown fuses: If your overhead crane is blowing fuses, this indicates that a circuit in the crane’s electrification system is faulty.
A hook is intended to hold a load in a specific and precise direction. When a load is not supported as intended by the hook, the weight compromises the hook’s internal integrity and increases the likelihood of bending, stretching, or cracking. If the load stretches out the hook’s throat opening, it may slip off the hook.
Regular inspections of hooks and other rigging hardware should be performed at the start of each shift to look for deformities or damage.
What Are the Different Types of Overhead Cranes?
Overhead bridge cranes are the most common type of crane found on construction and work sites. They generally function while having two overhead bridge beams linked to the facility’s support system. They can either come in either a single or double configuration.
Monorails Overhead Crane
A monorail crane system is a stationary, overhead track on which trolleys travel to transport loads from one location in a facility to another. Because they improve production workflow and create a safe and secure work environment, monorail cranes are an ideal solution for linear, overhead material handling.
Mobile Truck Crane
A mobile crane truck is a crane that is mounted on the chassis of a heavy, modified truck and can lift, lower, or move loaded materials horizontally and vertically. Truck cranes are commonly used in scrap yards and are outfitted with wire rope-suspended implements such as grapples, clamshells, crane hooks, and electric magnets.
Jib cranes resemble an upside-down letter “L.” They are typically floor mounted, either with their own dedicated support or to a building’s support beam. Jib cranes are typically equipped with an electric chain hoist and can be rotated manually. This allows them to perform numerous lifts over short distances with great efficiency.
These cranes are commonly found in production and assembly lines, factories, and mines.
Workstation cranes are similar to bridge cranes, but instead of relying on the building for support, they have their own floor-mounted supports. These cranes are extremely popular among garage mechanics and fabricators. They can be installed almost anywhere because they do not rely on the structural integrity of your building. They are also used in large manufacturing plants where a crane is not required to be accessible to the entire factory floor.
A gantry crane is a type of overhead crane with one or two girders supported by freestanding legs that move on wheels or along a track or rail system. When an overhead runway system is not feasible, gantry cranes are usually considered.
These are typically used outdoors or beneath an existing overhead bridge crane system. A gantry crane, unlike a bridge crane, does not need to be connected to a building’s support structure, eliminating the need for permanent runway beams and support columns. In some cases, this can result in significant material cost savings and a more cost-effective solution than a similarly specified bridge crane.
Larger gantry systems may run on an embedded rail or track in the ground, usually in a straight line in a dedicated work area. Smaller portable gantry systems are moved around a facility on castors or wheels for maintenance or light fabrication work.
Gantry cranes are classified into several types based on the type of supporting structure and application. The following are some of the most common types of gantry cranes.
Full-Gantry Overhead Cranes
One of the most common types of gantry cranes is the full-gantry overhead crane. It is made up of two supporting legs that move across fixed rails. The crane is usually used in a specific working area where vehicles can pass beneath it. This crane’s trolley moves within the main span, and the main beam has no overhang.
Typically, one leg of a semi-gantry crane runs along a surface rail, while the other runs along a runway system attached to a wall or other vertical structure. Depending on your construction site or requirements, you can establish the height difference between the two legs.
Portable Gantry Crane
This type of gantry crane is portable and can be transported and assembled at various locations as needed. As a result, it offers more flexibility. However, because it is small, it can only handle light loads.
Adjustable Gantry Cranes
An adjustable gantry crane can be portable or stationary. It also has a variable height and span design. Depending on your load requirements, you can adjust the base width, height, and horizontal beam length.
Single Girder Gantry Crane
This crane is made up of only one girder and rail. The trolley and hoist are usually under-hung. They run on the bridge’s underside. It is frequently a light- or medium-duty crane that is appropriate for areas with limited floor space and low headroom. It also offers low-cost lifting solutions.
Double Girder Gantry Crane
This crane, on the other hand, is made up of two girder beams that form the bridge. It is typically made up of a top-running trolley and a hoist. Under-running designs, on the other hand, are quite common. It is intended for heavy-duty use.