Those of us who use casters ask a lot of them. In an ideal world, we desire that they function perfectly 24 hours a day, every day of the week—that they roll on endlessly, never needing any attention from us, and that they never fail or wear out.
In the real world stuff happen! Bearings lose their lubrication and stop turning. Kingpins crack and twist. Tires go flat, tire treads wear out, and tires that are supposed to be round develop flat spots. Casters that are supposed to swivel stop swiveling, and casters that are supposed to roll straight and true start shimmying.
Here’s the good news: by choosing the right casters at the start, it’s possible to make a selection that ensures your casters will function like you would want them to. In this article, we’ll give you some ideas about how to choose the right casters for long term daily use.
5 Ways that Operating Conditions can Cause Casters to Fail
If we’re searching for casters that never break down and go on working perfectly day after day, it’s useful to first take a look at the way casters typically fail. Armed with that knowledge, we can then choose features for our casters that help ensure they avoid those failure modes.
The so-called “average,” or typical caster is designed to work well when the load is evenly distributed, within specifications; the caster moves at walking speeds or lower, over smooth floors; and operates at room temperature in an indoor environment.
If any of the following operating conditions occur, caster failure can follow.
- Overloading – Every caster has a specified load limit. This limit can be easily exceeded, in numerous ways. The load can shift to one corner of a cart, for example, placing all of the weight on only one or two wheels. In another example, four-wheeled carts do not always travel with all four wheels on the ground. If the cart tips, all the weight may end up on three casters, or even two. And of course, there’s always the possibility that an excessive load may be placed on the casters by operators who are unaware of the specified limits.
- Excess Speed – Average casters are designed to function at walking speeds. If the casters operate faster than this – when towed by a powered vehicle, for example – problems can occur. Flexible wheel treads such as polyurethane can build up heat faster than it can dissipate, causing the tread material to degrade. Lubrication materials can liquefy, and fail to keep bearings rolling freely. To combat these problems, caster designs must be modified for operation at higher speeds.
- Uneven Terrain – When a caster encounters the bumps and dips of rough surfaces or debris, havoc can result. Sudden impact loading can be caused when the caster strikes an object, causing the caster to exceed its load specifications. Denting of metal parts such as bearing raceways (brinelling) can impair smooth operation. Pieces of softer tire tread material like rubber or polyurethane can break off, and even hard materials like cast iron can be chipped or cracked.
- Temperature Extremes – Although most casters are designed to operate at room temperature, many must withstand the heat of bakery ovens, laboratory autoclaves, or the frigid temperatures of industrial freezers. Casters that operate in extreme temperatures must be made with wheel materials that will maintain their properties under these challenging conditions.
- Punishing Environments – If a caster must leave the comfortable surroundings of an air-conditioned office or warehouse, things can get tough. Wet outdoor weather, possibly with salt spray from the ocean; chemical wash-downs in food processing facilities, or hospitals, corrosive vapors in chemical plants – all can take their toll on casters not specifically designed for damaging environments.
The five conditions above describe how we might operate with casters (loading and speed), or the situation in which we use them (terrain, temperature and environment). The next section discusses the casters themselves, and ways to modify them for long term daily use.
The Good News – Casters Can Be Designed for Tough Conditions
The more you take into account the conditions under which your casters will operate, the better job you can do of selecting the best casters for your situation:
- Load Calculations – Figure out how much weight each caster must support, and then leave plenty of reserve to compensate for things like load imbalance, impact loading, or accidental overloading by operators.
- Speed Calculations – If your operations involve anything faster than walking speed, make sure you choose casters that are designed to function well at higher speeds.
- Combating Rough Terrain – Manufacturers have designed casters to combat the hazards of uneven floors, or surfaces covered with debris. Look for features like kingpinless casters, which eliminate kingpin failures; tapered bearings instead of ball bearings, which stand up well to side impacts; or hardened steel components for the top plate or caster fork.
- Environment and Temperature Considerations – No matter what your environment or operating temperature, you and your distributor should be able to work with a manufacturer and select castor components such as stainless steel or chrome for wet conditions, high-temperature phenolics for ovens, or special composites for freezing conditions.
The most important step in selecting casters for long term daily use is to understand your own operating conditions, and how they might cause caster failure – and then choose casters designed for use under those conditions.
Even Better News – Douglas Equipment can help You Choose the Best Casters!
Many factors can stand in the way of reliable, long-term daily use of casters. If you contact Douglas Equipment’s customer service department and tell us about your operating conditions, we can help you choose casters that will overcome any situations that could cause failure. The phone number for our team of caster experts is 800-451-0030or 305-888-3700 in the Miami area. We also can be contact online through our contact form.
