Selecting the Right Overhead Crane
Purchasing an overhead crane system is a long-term investment that can dramatically improve operations, streamline production, and increase worker safety. Selecting the best system for your application and facility will ultimately save you money in the future. However, choosing the right crane can be overwhelming and confusing. There are a lot of factors to consider, but we can make that process a little easier by providing critical information that will help you to make the right choice—and the best possible investment.
It’s important to consider what types of overhead cranes are available and become familiar with them. There are four main types of overhead cranes: gantry cranes, monorail cranes, workstation bridge cranes, and jib cranes. Knowing what each type of crane does and how it is designed will help you to select the right system for your application. Check out our Products page for additional information about each type of crane, or contact us to request a brochure or to speak with a material handling expert.
Once you have a general understanding about the different overhead cranes available, there are two major categories that will help you to select the right crane for your operation: application and facility. Each category includes a set of factors, which are broken down to provide a basic overview that will help you to select a crane.
Analyze Your Application
Starting with an honest evaluation of your material handling needs is a fundamental part of selecting the right system. Choosing a crane that is inappropriate for your application could be a dangerous, inefficient, and costly mistake. Consider the needs of your specific application and what you would like to achieve by integrating a new overhead lift system into your facility.
To help you develop a detailed analysis of your application and material handling needs, we have broken down the application category into five parts: capacity and service rating, structural components, mechanical and electrical components, motor controls and operator controls.
1. Capacity and Service Rating
The load rating capacity is the maximum load weight a crane can handle. It’s important to note the load capacity and frequency of operation. Operating a crane above its load rating capacity is extremely dangerous and can cause serious damage to your new system. Be sure that the maximum weight requirements of your application are less than the load rating capacity of the crane. Knowing this information will also help you to identify the right service rating classification for your new crane.
The CMAA offers six different service-rating classes. Each service rating is used to describe the type of service performed and frequency of use. The service rating helps users to select a crane designed for their particular application. These classes are listed from Class A Service—standby or infrequent service for installation and maintenance, to Class F Service—continuous, severe service for cranes capable of handling loads approaching rated capacity on a daily basis. Cranes are specifically designed for particular service ratings, and using a crane with a lower service rating than your application requires is unsafe and could result in serious damage to your system or property.
2. Structural Components
Most overhead cranes are made from welded steel plates or aluminum sections. The more steel, the heavier the crane. Consider your service classification and compare it to the type of crane you are interested in purchasing. Spanco A Series Gantry Cranes, for example, can either be steel or aluminum. Whereas aluminum gantry cranes are designed for lightweight applications and total portability, a steel gantry crane will provide a higher load rated capacity and is designed for heavier applications. Understanding these options will help you to make the best choice for your operation and to control some of the structural elements that impact the weight of the crane and its cost.
3. Mechanical & Electrical Components
Overhead cranes in general provide a variety of options beyond design and structure. Choosing the best mechanical and electrical options can be a daunting task without the right approach. But, if you consider the needs of your application and facility first, you can eliminate some of that confusion. There are multiple mechanical and electrical component options for each type of overhead crane we manufacture. Knowing what each component does and how it will impact your particular application will help you to decide which options are necessary.
In some instances, you might find that your application requires something that just doesn’t work in your facility. For instance, a telescoping bridge crane is a viable option for applications that require extended reach, especially when there are a lot of obstructions in or around your work area. The telescoping bridge travels beneath the bridge track, providing a larger scope of reach and the ability to move beyond a support column or under a mezzanine.
If your operation requires a system that can easily transport materials from one work area to another, you can leverage your system’s flexibility by using a mixed capacity bridge crane. Using heavier capacity runways with multiple smaller capacity bridges increases your coverage and provides a more versatile system. Depending on your application, adding or altering mechanical components can mean the difference between the wrong system and a highly effective system. Defining the needs and limitations of your application and facility will give you the opportunity to choose a system with the right components.
Depending on your operation, electrical components may also contribute to the overall efficiency of your new crane system. For applications and facilities that require workers to move materials in and out of hard-to-reach areas and around obstacles, adding a tractor drive to motorize the bridge or hoist trolley is extremely helpful. If your application requires workers to lift and transport heavy machinery, you can motorize the rotation of your jib boom for ease of use and increased efficiency. For assembly applications that require workers to move materials along a fixed path, an electric track mounted gantry may be the best solution. Track mounting ensures that the crane moves along its fixed route, and adding the electrical component provides motorized travel for ease of use and increased productivity. Take the time to discuss key components with your supplier to decide which electrical component, if any, is suited for your application.
4. Motor Controls & Operator Controls
Another notable option to consider when choosing the right system for your operation is the use of motor controls. Electrical control systems allow you to manipulate bridge and trolley motions for increased precision and safe, controlled lifting. These components also impact the cost of the crane, so making the best choice for your operation is crucial. If you choose to purchase a motorized system, ask your supplier if they provide speed control. A variable frequency drive, for instance, is an adjustable-speed drive used to control motor speed and torque by varying motor input frequency and voltage. VFD provides cushioned acceleration and de-acceleration, which is especially important when handling fragile or oversized loads. At Spanco, we provide VFD technology on every motorized system that we manufacture. Knowing what your supplier provides with each system and how it will benefit your application is a fundamental step in your buying process.
Operator control systems also impact crane design. These components greatly increase worker safety and improve efficiency. Operator controls are like a TV remote for your crane, allowing workers to control the system electronically. This is particularly useful for applications that require workers to multi-task safely or at a distance. For example, a festooned push button pendant station allows the crane operator to stand at a distance—or to work in multiple stations—and still control the hoist and load travel. This is an important component for motorized systems that are mounted in hazardous conditions or an inaccessible area.
Evaluate Your Facility
Next to your application, your facility space and size is the most important factor you need to consider when selecting the right crane. These parameters include building size, installation needs, potential obstructions (including preexisting equipment and machinery), clearance requirements, and operating environment.
1. Building Size & Crane Span
To start, think about the size of your facility and how it could potentially impact the installation of your new crane. Your supplier will need to know the length and width of your facility or work area. It’s also important to note any overhead obstructions or height restrictions. OSHA requires a minimum clearance of three inches overhead and two inches laterally between the crane and any obstructions. Furthermore, if you have a height restriction, your supplier can recommend options for your new system to safely increase trolley-clevis height. Your trolley-clevis height, which is the distance from the floor to the bottom of the trolley clevis, directly impacts your hook height and that could limit the overall efficiency of your system. For instance, installing a double girder bridge on a bridge crane can help to increase trolley-clevis height when overall height in your facility is restricted. Knowing this information will help you to select an optimal crane design for your operation and facility.
It’s also important to note what crane span your application requires. The span of the overhead beam is essential to determine the size of the crane. This could be the full length of your workshop, or for workshops without attached runway beams, an under-hung system may be ideal. Your application may require a gantry crane that can be transported to specific work areas. The perfect crane for your application may not work for your facility, which is why it’s important to take both factors into consideration. Knowing the needs of your facility is critical to selecting the best material handling solution at the right price.
2. Obstructions
Obstructions in your facility may directly impact your application if they limit crane mobility or installation. It’s a good idea to walk around your facility or workspace and make a note of any overhead, wall, or column obstructions that may prohibit the use of a ceiling- or wall-mounted system. Since OSHA mandates a three-inch overhead clearance and a two-inch lateral clearance, large equipment or machinery, beams, columns, and supports can obstruct the safe installation and use of certain cranes. Knowing any potential obstructions will allow you to consider all of your mounting and installation options and purchase an overhead crane that works for your operation and set-up.
It’s also important to note what type of coverage your application requires and whether or not your facility will support a particular system. If you need circular coverage or if you are considering a jib crane, for instance, do you need 360 degrees or 200 degrees of rotation to get the job done? A jib crane will provide circular coverage, but whether or not the coverage is 360 or 200 degrees depends on the mounting and installation. This can be tricky in some situations where the application and facility have opposing needs. For example, an application may require 360-degrees of coverage, but the facility may only support a wall-mounted system. Wall-mounted jib cranes only provide 200-degrees of rotation. But, in some cases, the wall-mounted jib crane can be mounted on a column to provide 360-degree rotation. Identifying where your facility and application “disagree” can save you a lot of headache later.
3. Installation & Assembly
When considering what type of installation or mounting device to use, it’s also important to consider runway beams, column supports, and the overall environment where the crane will be installed or assembled. These factors will directly influence which system you choose to install and where/how you install it. Each particular type of overhead crane lends itself to several installation options, which makes mounting and installation an important part of your decision making process.
Consider whether or not your application and facility require a portable system that is easily transported from one part of your facility to another. Gantry cranes, for example, don’t require any installation at all, unless they are track mounted. This makes them ideal for rented facilities or for future workflow changes. Most gantry cranes are quick and easy to assemble and disassemble, so transportation is not a problem.
If portability is not an issue, there are multiple options for installing a permanent overhead crane system. A freestanding jib crane, for instance, requires a particular foundation and ample space for safe mounting. Most freestanding jibs offer multiple mounting options depending on the needs of your facility. On the other hand, ceiling- and wall-mounted systems require no floor space or special foundation, and wall-mounted systems quickly fold out of the way for large overhead cranes.
Assembling and installing your overhead crane may also require specific equipment, and in most instances, an engineer or qualified person may need to check your facility’s structural support. A ceiling-mounted workstation bridge crane, for example, may not be a feasible option in a building without adequate support. It’s crucial that these systems be assembled and installed by a qualified individual who can properly assess existing roof beams or trusses. Some systems—like ceiling-mounted bridge cranes—also require a fork-truck to elevate the bridge and place it into the tracks once its assembled. That’s why it’s so important to consider not just the needs of your application, but also the needs of your facility.
4. Inspection & Maintenance
According to CMAA specifications and standards, once you have selected and installed an overhead crane, the owner is responsible for several other factors attributed to its proper use and maintenance. Discuss maintenance requirements with your supplier before purchasing a system to be sure you’re aware of your responsibilities. Maintenance requirements will vary depending on the type of lift equipment installed.
OSHA standards (OSHA 1910.179) require crane inspections at set intervals based on your crane’s service rating classification (outlined above). A crane with a Class C Service Rating—moderate service, for instance, requires an annual OSHA inspection and a bi-monthly preventative maintenance schedule.
Additional inspections may be required depending on hours of operation, environment, and severity of service. There are also additional inspection requirements set forth by ANSI (B30.2, B30.11 and B30.17), and oftentimes, your crane manufacturer will outline its own set of guidelines. Once your crane has been properly installed and tested, it is essential to develop and follow a strict maintenance and inspection schedule to ensure long-term satisfaction with your material handling investment.
Contact Spanco, Inc. for additional information about our products and services. For more information about overhead crane standards, regulations, and guidelines, check out the following organizations.
American National Standard Institute (ANSI): http://ansi.org/
American Society of Mechanical Engineers (ASME): https://www.asme.org/
Occupational Safety & Health Administration (OSHA): https://www.osha.gov/