Caster Wheel Load Rating: What Is It and Why Is It Important?
Any responsible business that depends on equipment for daily business operations cannot afford to overlook manufacturer safety guidelines. The casters that move your furniture and heavy equipment are vital to efficiency and workplace safety.
Understanding and applying caster wheel load rating is crucial in preventing workplace accidents and property damage. It is essential to consider the different parts of the caster, including the caster wheel, and the forces they withstand while in operation.
What Are Casters?
Casters are devices that attach wheels to heavy furniture or conveyances. A caster consists of a wheel and a metal or plastic fitting that holds the wheel in place and anchors it to the structure it supports. Casters provide support for:
- Chairs and office furniture
- Gurneys and carts
- Heavy equipment
- Pallets for construction sites and warehouses
Types of Caster
The ability of a caster to function depends on the strength of different caster components. Potential weak points include:
- The caster wheel
- The bearings that allow the caster to swivel
- The caster fitting that anchors the wheel to the furniture
The two most common caster fittings are stem casters and plate casters. Stem casters attach to furniture through a central stem that can swivel, while plate casters attach through a metal plate fastened by screws.
Stem casters tend to have lower weight ratings because the stem can snap under heavy loads. Conversely, plate casters are sturdier because the four screws anchoring the caster each share the load.
You can choose from many different caster styles and materials. The load rating of a caster or a caster wheel depends on its material composition, design, size, and other factors.
Factors That Influence Wheel Load Rating
Caster Wheel Material
All other things being equal, cast iron caster wheels have a high load-bearing capacity. Polymer caster wheels, such as nylon or polyurethane wheels, vary in their load-bearing capacity depending on the specific material they contain. Wooden caster wheels are well-suited for light duty but might not always be the best choice for bearing heavy loads.
The Size of Caster Wheels
Large caster wheels can typically support heavier loads. For example, a caster with a wide wheel distributes the weight over a larger area, while stem casters with wider stems and plate casters with thicker screws can bear heavier loads without breaking. Additionally, caster wheels with a larger wheel diameter also have higher load ratings.
The Danger of Exceeding Caster Load Ratings
Casters are a dependable technology with a tradition of safety going back well over a century. However, casters could suffer damage, seize, or fail catastrophically if they bear a load beyond their intended design. The impact on your business could far exceed the cost of a replacement caster.
If any of these events occur, the consequences could be significant:
- Breakage of casters
- Workplace injuries
- Loss of control while moving heavy objects
- Collisions with people, walls, or equipment
- Spillage of potentially hazardous material
- Damage to the reputation of your business
You never can tell when a core function of your business could depend on something as small as a furniture caster. The manufacturer’s load rating helps you avoid accidents and take the guesswork out of:
- Decisions to order inventory
- Training and instruction to employees
- Workplace rules and best practices
By keeping the load capacity of casters in mind, you and your employees can work together confidently.
Consider the furniture, pallets, and equipment you currently own. Do you know the load ratings for every caster or wheeled piece of furniture you own? Can you say without a doubt that the load on those casters and wheels is appropriate?
Familiarize yourself with the caster types and their load ratings. If you have any questions or concerns, contact Caster Central to discuss them with a caster expert.
Determining the Load Rating for a Conveyance or Piece of Furniture
The manufacturers provide a rating of the static load that a caster can support. To calculate the load that a caster will have to support for a particular application, multiply the load rating by the number of casters, considering the following factors.
The Number of Casters
One way to increase the load-bearing capacity of a cart or pallet is to add more casters. For example, if a caster has a load rating of 50 pounds, increasing the number of casters from four to six would increase the load-bearing capacity from 200 to 300 pounds.
The Weight of the Pallet or Transport Vehicle
When loading a cart, dolly, or pallet, do not neglect their weight when determining the load on the casters. For example, if a cart weighs 25 pounds and carries a load of 100 pounds, the total weight on the casters would be 125 pounds.
Tips for Using the Load Rating
The load rating does not always provide a complete picture of how casters will respond in specific situations. Keep the following caveats in mind when purchasing casters and develop safety policies for the use of casters by your employees on your property.
Include a Margin of Error
If you calculate the load-bearing capacity of a set of casters to be, for example, 300 pounds, avoid loading the conveyance with material that approaches the weight limit for the casters. If someone miscalculates the load weight or adds more weight, it could overload and damage the casters.
In general, add one-third to the weight on the casters to calculate the weight capacity you need. For example, if a 50-pound cart will be conveying 250 pounds of weight, the best practice would be to ensure a combined weight rating for the casters should be 300 pounds plus a safety margin of 100 pounds for a total wheel caster rating of 400 pounds.
Consider That Dynamic Load Can be Higher Than Static Load
Caster wheel load rating can be a measure of either static or dynamic load. Static load capacity refers to the ability to bear a load while stationary. Meanwhile, dynamic load capacity is the ability to support a load while the wheels are in motion.
The forces on a caster wheel are not always constant over time. For example, if someone were to throw a heavy object onto a cart or if the object were to fall onto the cart, the force on the caster wheels could exceed the caster wheel load rating at the moment of impact. The casters could fail even if the resting weight of the item was less than the caster weight rating.
Be Mindful of Unequal Distribution of Load
Calculations for load capacity based on the caster wheel load rating assume that each caster will bear an equal share of the weight.
However, if a cart is on an uneven surface or tilted, one or more casters could lose contact with the ground. The remaining casters could bear the weight, which could exceed their individual caster wheel load rating.
Unequal weight distribution could occur instantaneously as a cart rolls over a broken or uneven surface.
Caster Central Can Help You Find the Best Casters for Safety and Performance
If you need to upgrade your furniture and equipment with new casters with a higher caster wheel load rating, let Caster Central help. The experts at Caster Central work with you to find the best casters for your business needs.
Explore our extensive inventory of high-quality casters on our website or call us at 1-800-445-4082. You can also learn important tips when removing casters so that your retrofitting process goes smoothly and protects your workers and property.