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Just what is a Safe Working Load?

Determining Safe Working Load is Critical when Choosing Industrial Wheels

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A model R-3547 steel wheel by Reliance Foundry is shown on a white surface with no background.

The Right Wheel for the Right Work Environment

"When asking how much a wheel can hold, it’s really necessary to examine the specific application and the stresses that will be placed on the wheel," says Reliance Foundry’s Product Manager, Len Cranmore. "Over the years, we’ve noted a lot of factors that can affect a wheel’s ability to bear weight. Sometimes it’s as simple as the way the load is placed in the cart."

Some factors include:

  • The variety of stresses and strains placed on the wheel
  • Differing stresses due to the direction from which carts are loaded
  • How often the cart is loaded
  • Speed the wheel will travel
  • Distribution of the load
  • The number of wheels and how they interact with one another

How to Calculate a Wheel's Safe Working Load for Ideal Conditions

To give some idea of a wheel’s suitability for an application, manufacturers and suppliers often discuss load rating or load capacity. A more definite term, and the term that Reliance Foundry provides for its wheels, is safe working loadSafe working load, sometimes referred to as normal working load, is the maximum weight that a manufacturer suggests a wheel can safely hold or transfer under ideal circumstances. It is calculated by determining the wheel’s breaking point under a static load, and then dividing that number by an appropriate factor of safety.

Assuming that the load will be distributed in an even manner in the cart and that the wheel will be used in ideal conditions, determining wheel requirements is easy. Of course, using a greater number of wheels will decrease the strain placed on each wheel. A general rule for calculating the safe working load requirement for each wheel is to add 25% to the total load the cart will carry and then divide that number by the number of wheels that will be used. For example, if an industrial cart has four wheels and must carry 10,000lbs, the equation would be

(10,000 lbs. + 25%) ÷ 4 = 3,125 lbs.

In this example, the safe working load requirement for each wheel would be 3,125 lbs. when the wheels are used in ideal conditions.

A screen shot of a wheel product is shown with an arrow pointing out where “safe working loads” are listed is shown.

Safe working loads are clearly listed on every wheel’s product page.

When Conditions Are Less Than Ideal

Of course, in the real world, conditions can be adverse, and such an environment may affect a wheel’s ability to bear weight. If this is the case, it may be necessary to consult an engineer for advice and specifications. Factors, among others, that indicate an engineer's advice may be needed are:

  • A moist or damp environment
  • Abnormally hot or cold conditions
  • Customizations to wheel dimensions
  • Potential exposure to chemicals
  • Speeds that will exceed 3 mph (4.92 kph)
  • Loads that cannot be distributed evenly against the wheel's tread
  • Multiple load or other load stress conditions, such as where there will be different types of loads or where there may be varying load directions

Track Conditions: An old, skewed, or vibrating track may damage wheels and limit their ability to bear weight. For ideal performance, wheels should be used on tracks that are well aligned, level, and composed of a material that is of similar hardness to the wheel.

We Will Work with Your Engineer to Provide the Standard or Custom Wheels for Your Specific Needs

Determining the SWL requires an assessment by a competent person of the maximum load the wheel can sustain in the environment in which it will be used, and in any doubt you should call in a specialist.

A freshly manufactured steel wheel sits on a bench at the old Reliance Foundry.

An engineer or other qualified professional should always be consulted when a wheel is used for applications that fall outside of the manufacturer's recommendations. Product drawings for all of Reliance Foundry's wheels can be easily accessed online and we will gladly provide you with materials and design data.

To help ensure job site safety and to mitigate its customer's risks, Reliance Foundry uses conservative factors when determining SWL limits. However, safe working load recommendations provided by suppliers are only suggestions; manufacturers assume no liability, and Reliance Foundry does not market its wheels for specific applications.

We normally carry eight varieties of double flanged wheels and two varieties of single flanged wheels in stock; it's likely we'll have the wheel you need. If you need a wheel that is a little out of the ordinary, we will source the best manufacturer to make quality custom wheels for you and a reasonable price. To learn the safe working load of Reliance Foundry's steel wheels, visit our informative, industrial cart wheel website.

About Reliance Foundry Co. Ltd.
Reliance Foundry has been a trusted supplier of cast metal products since 1927. Specialists in wheel design, production and usage, Reliance Foundry’s innovative catalogue also features innovative bollards and cutting-edge bike parking systems. Reliance Foundry sources cast metal solutions from across the globe to provide competitive prices and conveniently ships to all locations within North America. For more information on Reliance Foundry’s many innovative cast metal solutions and services, please visit www.reliance-foundry.com.

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