This guide contains everything you need to know about overhead cranes.
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An overhead crane is a type of heavy-duty machinery designed to safely and precisely move extremely heavy loads and equipment across a manufacturing facility using the overhead space. Given their critical role, these cranes are precisely configured and engineered to meet the specific requirements of different loading applications.
Overhead cranes are available in various sizes, types, shapes, and configurations, and come with a range of components and accessories. They are utilized for tasks such as loading and unloading, moving materials, lifting dies from stamping machines, and feeding raw materials.
The primary reasons for installing an overhead crane are efficiency and safety. Overhead cranes operate significantly faster than floor-mounted or land-based devices. In hazardous environments involving heated metals, chemicals, or toxic substances, overhead cranes can safely transport materials, reducing the risk to workers.
When moving bulky materials or extremely heavy loads through a manufacturing facility, using an overhead crane is more convenient and efficient than maneuvering through aisles and floor space. Overhead cranes can lift, lower, and move loads horizontally along a rail or beam, handling extremely heavy weights safely. The crane's travel and speed are managed by an operator via a pendant station or wireless control.
Overhead cranes span a rectangular area and can move loads both side to side and forward and backward. While not all overhead cranes are identical, they generally include standard components such as a hoist, trolley, beams, girders, and control systems.
The bridge of an overhead crane traverses longitudinally along tracks mounted on runway beams across the rectangular working area. These bridges are constructed from steel girders that connect to the runways at each end.
The lifting trolley houses the lifting mechanism, which includes a brake, motor, reducer, drum, and pulleys. The motor powers the drum, which rotates through the reducer to drive the wire rope or chain, thereby raising and lowering the load.
There are two parts to the driving mechanism of a crane. There is the long transmission that drives the wheels on both sides, while a separate motor drives each set of wheels individually.
The power supply for overhead cranes involves various systems, each with different connection methods. The three common types are conductor bars, festoon systems, and cable reels.
Most overhead cranes rely on electricity for their power supply, although pneumatic versions are also available. Power is transferred to the crane's runway and bridge control through cable festoons, conductor bars, or reel cables. This power is then used to operate the trolley and hoist.
Conductor Bar – A conductor bar system is installed on the crane‘s runway or monorail. They can be used on runways with more than one bridge. Power is supplied through a sliding shoe collector system, which is safer than other methods.
The installation height of the crane affects both the type of motor and the crane's capacity. The lift height of an overhead crane, measured from the floor to the saddle of the hook, is a critical factor. It ensures there is sufficient clearance for lifting and repositioning the load.
Another critical factor is the C dimension, which represents the maximum height to which the hook can be lifted. The C dimension measures the distance from the trolley wheels to the hook saddle.
Each aspect of an overhead crane's movement is managed by software and electronics designed for seamless operation and safety. The crane controls allow the operator to have full control over the load at all times. Basic controls typically feature start and stop buttons, while more advanced systems may include joysticks and tablets for programming a broader range of motions. These controls are programmed with the crane’s operational limits, specifying its capabilities and movement areas. Control systems also offer usage data, diagnostics, and error management tools.
The two primary types of hoists used in overhead cranes are chain hoists and wire rope hoists. A chain hoist, supported by a chain holder, is designed for lifting loads of up to ten tons. It offers true vertical lifting and rises straight up without any lateral drift.
Wire rope on hoists are hooked to the load and capable of lifting ten tons or more. They allow for more options and greater flexibility. Unlike chain hoists, wire rope hoists are susceptible to lateral movement.
Transporting bulky, heavy, and cumbersome loads along the aisles and floor of a manufacturing facility can be both dangerous and time-consuming. Installing an overhead crane to utilize the factory's overhead space enhances efficiency, cost-effectiveness, and safety. It allows for easy lifting, lowering, and movement of loads through unused vertical space, saving both time and energy.
Specially trained operators use various control devices to manage the crane’s movements. When considering movement options, it’s crucial to assess the available space and the feasibility of installing an overhead crane.
The first industry that often requires an overhead crane is warehousing, where supplies, equipment, and materials are frequently moved, positioned, and prepared. A key advantage of using an overhead crane in warehousing is its ability to efficiently transport large items from storage to the shipping dock.
Industries that assemble large equipment need a method for lifting and relocating incomplete assemblies during production. Forklifts, AGVs, and other material handling equipment often fall short in terms of safety and efficiency, making an overhead crane essential. It facilitates the smooth movement of assemblies as a natural part of the production process.
The parameters applicable to warehousing also apply to transportation, where heavy, bulky products must be loaded onto planes, trains, and trucks. Overhead cranes efficiently position large materials for transport, including in situations like overseas shipping, where they lower massive containers and goods into ship holds.
When the repair of a punch press or other factory equipment is required, overhead cranes assist in facilitating the repair by gradually moving and positioning pieces for easy access. Gantry and bridge cranes can remove heavy equipment from their permanent location to a repair shop and then return them. Overhead cranes make it easier to lift machines up and over other equipment to be placed at a repair station.
Once the decision to install an overhead crane is made, the next step is to choose the type that best suits your needs. Overhead cranes are available in two main types: single girder and double girder. Single girder cranes feature a hung trolley hoist, while double girder cranes use a double girder crab-style trolley hoist. Both types can be configured as either top-running or under-running.
From these two basic types, there are numerous crane sizes with variations in capacity, configuration, and function. Selecting the right crane involves careful consideration, as the appropriate choice and specifications can significantly enhance productivity, efficiency, and workflow.
A bridge crane features two runways mounted on either side of a building and attached to its superstructure. These runways are linked by a bridge with end trucks that travel on wheels along the runways. The bridge can be configured as either single or double girder, with a trolley running on each type. The trolley and hoist are mounted underneath and move along the bottom of the bridge.
A gantry crane A gantry crane closely resembles a bridge crane, with one key difference: instead of having its runways attached to the building's superstructure, a gantry crane rests on four legs that support and move it. The bridge, trolley, and hoist are connected to these legs, which move along rails to position the crane for loading, lifting, and moving. These rails are mounted on the floor, ground, or foundation, similar to railway tracks.
Unlike gantry and bridge cranes, monorail cranes lack a bridge or girders. Instead, the trolley is attached to an I-beam fixed to the ceiling and moves along the flat surface of the beam. The material is transported in a straight line along the beam, with the hoist and trolley facilitating movement. The key advantage of a monorail crane is its flexibility, allowing for curves, branches, and switches to adjust elevation and direction.
A jib crane Jib cranes are another variation of overhead cranes that do not rely on a bridge, runway, or track system. They can be mounted in various configurations, such as attached to a wall or standing independently. Jib cranes are space-efficient, cost-effective, and ideal for moving assemblies. They can be designed for either full 360-degree rotation or limited rotational range. Even smaller jib cranes can lift and move several tons..
Top running and bottom running crane configurations refer to the placement of the wheels along the bridge girders. In top running cranes, the bridge travels on top of the runway beams. In contrast, bottom running, or underhung cranes, have the bridge supported on the underside of the runway beams, with the crane wheels running along the lower flange of the girders.
Top running cranes offer higher capacity and can lift heavier loads compared to underhung cranes. Underhung cranes are typically used for lighter loads, have a lower capacity, and are supported by roof or ceiling structures.
An overhead crane can be either fully automated, where the operator programs the crane to perform tasks without manual intervention, or semi-automated, where some functions are controlled by the operator. A fully automated system relies on specialized software and is ideal for demanding or hazardous environments where operator safety is a concern. Additionally, automation reduces the repetitive strain on operators by handling monotonous tasks automatically.
Automated systems minimize errors and operate with high efficiency and precision by removing the need for manual intervention. These systems can handle various tasks such as lifting, positioning, stacking, and storing, with the ability to repeat these operations continuously over time, from eight to twenty-four hours a day.
Workstation cranes are a type of bridge crane designed for light to heavy production tasks, with lifting capacities of up to two tons. They are compact and customizable to fit specific workspaces. Their smaller size allows them to be installed alongside jib or other overhead cranes, enhancing the efficiency of work cells.
The key benefit of workstation cranes is their ergonomic design, which reduces the need for manual lifting of heavy materials. This not only enhances worker safety but also boosts morale, improves quality, and increases productivity.
Grab overhead cranes come in various designs, including bridge, gantry, and folding arm configurations. They feature attachments such as buckets, orange peels, or clam shells for handling bulk materials. With options for single or double girder designs, grab cranes are commonly used in mines, ports, and yards to load and manage materials like logs, minerals, coal, sand, and gravel.
In production operations, the supply chain is vital for transporting raw materials and components to assembly areas. While forklifts, pallet jacks, and AGVs are suitable for many tasks, handling large or bulky materials often requires a more precise solution to ensure safety and efficiency. In these situations, overhead cranes are essential for effective and secure material handling.
Unlike other industrial equipment, overhead cranes must be specifically configured and designed for their intended operations. A crane suited for automotive production might not be suitable for shipping tasks, and similarly, cranes used in steel production may not be appropriate for other types of work.
Since their debut in the first industrial revolution, overhead cranes have become indispensable in countless production operations due to their safety, time-saving efficiency, and ease of use.
Overhead cranes in the automotive industry perform multiple roles, from material handling and supply chain management to lifting and transport tasks. In press plants, these cranes are essential for moving and storing dies and tools while ensuring production lines remain well-supplied. In assembly plants, workers depend on overhead cranes to enhance efficiency and eliminate the need for manual lifting.
Every aspect of an automotive production plant benefits from the time-saving and convenience of overhead cranes. Their use enhances production efficiency and helps prevent delays caused by supply chain interruptions.
The primary requirement for cranes in the steel industry is their ability to operate under harsh conditions, including elevated temperatures, high-grade dust, and severe vibrations. Ladle cranes are reinforced and stabilized to handle ladles safely and efficiently. Double girder overhead cranes are commonly used to deliver components like casting molds and to supply casting parts.
The steel industry heavily relies on overhead cranes for both safety and efficiency. In addition to ladle handling cranes, the industry utilizes tundish, slab, scrap, billet or ingot, coil, and foundry cranes, among others.
The plastic industry employs various molding techniques like extrusion, injection molding, and rotational molding. Regardless of the method, frequent mold changes are essential to maintain production and meet customer demands. The dies used in these processes require precise handling and accurate placement, which is achieved using cranes capable of millimetric precision.
Similar to the steel industry, shipbuilding heavily relies on overhead cranes due to the size and weight of the materials involved in constructing a ship. The industry primarily uses three types of cranes: jib, gantry, and overhead. The choice between a chain or wire rope hoist depends on the specific material being moved.
The primary role of overhead cranes in shipbuilding is to handle materials throughout the assembly process. Overhead cranes are utilized at every stage of shipbuilding, including processing, assembly, fieldwork, launch, rigging, and delivery. These cranes are specifically designed to meet space requirements and are equipped with steel plate hooks and various types of chain hoists.electric motors.
Biomass overhead cranes are specialized for handling various types of waste, including refuse, garbage, slag, sludge, and straw bales. Each type of waste requires a specific crane design. Similar to other industries, the biomass sector utilizes jib, gantry, and overhead cranes, equipped with either chain or wire rope hoists, depending on the application.
When purchasing a biomass crane, several factors must be considered, including truck delivery schedules, the tonnage and density of the biomass, and the size and dimensions of the storage area. Biomass hoists are typically equipped with a bucket, orange peel, or clamshell attachment for effectively grabbing and handling the load.
Due to the volatile nature of gas and petroleum, overhead cranes used in these industries must be designed to prevent ignition risks. They are constructed from explosion-proof materials that are spark-resistant. One of the significant challenges in the oil and petroleum sector is designing cranes for offshore drilling sites. Initially, land-based designs were adapted to meet the unique conditions of these offshore environments.
Offshore platforms present unique conditions, such as waves that can affect loading and unloading operations. Therefore, cranes on these platforms are engineered to manage loads while considering factors like the distance of the load from the crane. Additionally, the mounting structure and other environmental conditions are crucial factors in the crane's design.
In the food and drink industry, the primary qualification for material handling equipment is cleanliness and sanitation. Overhead cranes are employed to move rail-mounted containers for production and storage in food processing. While these cranes significantly enhance efficiency, maintaining their sanitation to meet industry standards presents a key challenge.
Controlled environments are crucial in the food industry. To meet strict requirements and high standards, producers develop custom-designed lifting equipment tailored to these specific conditions.
The semiconductor industry involves handling heavy components that require reliable, hygienic lifting solutions to prevent contamination. Overhead cranes in this sector must be precise, accurate, clean, and efficient to adhere to stringent quality standards.
For an overhead crane to be suitable for the semiconductor industry, it must comply with cleanroom standards. Unlike other material handling solutions, cleanrooms have strict controls on particulate dust levels, presenting a unique challenge in designing overhead cranes for this sector.
The demanding conditions of the mining industry require overhead cranes that can withstand harsh environments. These cranes are essential for repairing and servicing underground mining equipment. Due to the corrosive nature of mining environments, equipment experiences rapid wear and tear, making durable and reliable cranes crucial for maintaining operations.
Mining cranes are heavy-duty machines designed to handle several tons of equipment and materials. Constructed from heat-, dust-, and moisture-resistant metals, these cranes must operate efficiently and reliably despite the harsh conditions.
The paper industry requires robust cranes capable of handling materials with high precision and care, as paper rolls are easily damaged by even minor impacts. These cranes must manage the large, heavy rolls of paper delicately and maintain sanitary conditions during production.
To ensure worker safety, cranes in the paper industry are equipped with automated control systems, essential for both pulp production and paper manufacturing. These systems allow precise regulation of crane speed to handle materials properly and are outfitted with slings for the safe loading and unloading of paper rolls.
Choosing and constructing an overhead crane requires considering several factors beyond just the load or materials involved. Since overhead cranes are tailored to specific conditions and configurations, it is crucial to thoroughly understand how the crane will integrate into the operation and meet the operational needs.
It is extremely important to carefully plan and prepare for the installation of an overhead crane. Manufacturers work closely with their clients to ensure what is planned and installed exactly meets the needs of the customer.
The span is the distance between the runway rails, which is one of the more costly aspects of the construction process. A longer and wider span determines the amount of material required to construct the girders, which increases the cranes weight and cost.
The determination of a crane‘s capacity is the maximum load that may be applied to the crane under the required working conditions. When figuring the load capacity, the first condition is the size and weight of the material to be lifted. Once the load capacity is determined, the type of hook and hoist can be decided.
In cases where the crane will have a large span, capacity, and must endure severe circumstances, a double girder design may be necessary. For extra strength, double girders are made of welded reinforced steel.
Overhead cranes have six classifications established by the Crane Manufacturer Association of America (CMAA). The determination of a crane‘s classification uses these criteria:
The severity of the work environment, including the presence of obstructions and potential hazards, is a critical factor in overhead crane construction. Factors such as heat, chemicals, fumes, steam, dust, and moisture necessitate the use of specialized construction materials to prevent crane deterioration. Additionally, protective coatings may be required to ensure the crane operates effectively and remains in good condition.
Operations that have the potential of explosions such as wastewater processing, fertilizer plants, and oil and gas processing necessitate explosion proof qualifications, which means the crane must not generate sparks. This type of crane operates using a pneumatic air powered system or a specially designed explosion proof electrical system.
The installation of the runway can be a challenge depending on the type of structure where the overhead crane will be installed. This does not apply to gantry models that have supporting legs, while buildings have the runways placed along the upper part of the walls. The first determination is the length of the runway, which determines the speed and movement of the trolley and hoist up and down the runway.
When a crane is being placed in a new building, the runways are planned as a part of the construction and are included in the blueprints. In this case, the contractor has to pay close attention to crane tolerances since they are more restrictive than typical construction codes.
Adding an overhead crane to an existing structure can be expensive since several steps have to be taken in the fabrication, design, and installation process. To ensure proper performance and safety, it is usually necessary to add extra support to the existing structure.
The nature of overhead cranes and the dangers involved in their use is the concern of several regulating agencies, which includes the National Electrical Manufacturers Association (NEMA), the Occupational Safety and Health Administration (OSHA), the American National Standards Institute (ANSI), and Crane Manufacturers Association of America (CMAA).
Each of these organizations have a different approach to the operation and use of overhead cranes. What is the concern of all groups is the safety of workers and materials. The operation of an overhead crane falls into the category of heavy industrial equipment, which requires that it be operated and used by trained staff.
The CMAA is a voluntary membership organization where affiliated producers adhere to mutually agreed manufacturing standards for overhead cranes. They provide training, guidance, and classifications for overhead cranes. They classify cranes according to their per hour use and number of times they are at full capacity. The A to F classification system is:
| CMAA Classifications | ||
|---|---|---|
| A | Infrequent Service | This Service Class Covers Crane Where Precise Handling of Equipment at Slow Speeds with Long Idle Persiods Between Lifts. Lifting May Be Required for Initial Installation of Equipments and for Infrequent Maintenance. This Crane Usually is Used for Turbine Rooms, Power Houses, Motor Rooms, Transformer Stations, etc. |
| B | Light Service | This Service class Covers Crane Where Service Requirements are Light and The Speed is Low. Loads Vary from None to Occational Full Capacity. This Crane Usually is Used for Warehouses, Workshops, Service Buildings, etc. |
| C | Moderate Service | This Service Class Covers Crane Where Service Requirements are Deemed Moderate, Handling Loads which Average not Over 50% if the Rated Capacity with Until 10 Lifts per Hour. This Crane Usually is Used for Machine Shops, Paper Mill Machine Rooms, etc. |
| D | Heavy Service | This Service Class Covers Crane Where Handling Loads Approaching 50% to 65% of the Rated Capacity and Constantly During the Working Hour Period, with 10 Until 20 Lifts per Hours. This Crane Usually is Used for Fabricating Plants, Production Plants, Maintenance Shops, Heavy Machine Shops, Lumber Mills, Steel Warehouses, etc. |
| E | Severe Service | This Service Class Covers Crane Where Handling Loads Approaching Near the Rated Capacity Throughout its Life with 20 or More Lifts per Hour. This Crane Usually is Used for Cement Mills, Lumber Mills, Fertilizer Plants, Heavy Machine Shops, Container Handling, etc. |
| F | Continuous Severe Service | This Service Class Covers Crane Where Handling Loads Approaching Near the Rated Capacity Continuously. This Crane is Designed to Performing the Critical Work Tasks Affecting the Total Production Facility. |
Class A refers to installation and maintenance cranes that operate at slow speeds, have long periods of idleness, and infrequently have capacity loads. Class F covers the top of the line bridge, gantry, multiple girder, electric overhead, and monorail cranes that constantly handle full capacity loads.
OSHA standards regarding crane operation are under classification 1910.179 titled Overhead and Gantry Cranes. The over 300 standards cover every aspect of crane operation from the type of clothing and fire prevention equipment to methods for avoiding the dropping of loads - and the methods of inspection.
OSHA load handling requirements address the following:
The NEMA publishes ratings for construction, testing, and performance guidelines for industrial control systems for crane and hoist controllers under standard ICS 8-2019.
Much like OSHA, the ANSI has a wide range of requirements and standards regarding load capacity, ropes, inspection guidelines, and every aspect of the construction and maintenance of an overhead crane. Included in their documentation are diagrams and designs regarding proper use and manufacturing of overhead cranes.
The ASME is a professional organization that supports various manufacturing practices through offering classes, training, and developmental information. The organization has regular conferences to provide guidance and assistance to ASME members.
For cranes, ASME provides specific information on common terms, inspection criteria, and criteria of when to take out of service.
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