When caster manufacturers design a caster, they start by picking components for the most straightforward, simple application – then they look at more complex situations, and make modifications. For example, the basic model of a caster might be designed to operate indoors, at comfortable temperatures, on smooth, clean floors, and under moderate loads.
Next, the complications are considered. High temperatures, like those found in bakery ovens or autoclaves, might require different wheel materials. Caster use in moist environments might rule out components that can rust, and if the moisture is from harsh chemicals or wash-down sprays, the caster designer must take that into account, and pick rubber, plastic or metal components that won’t be damaged by the chemicals and liquids. If casters are to be used outdoors, their components must keep rolling in summer heat or winter cold – possibly both – and not be destroyed by harmful UV radiation from the sun.
Then there’s debris. Not all floors are clean and smooth. Many surfaces on which casters must roll are located in industrial settings, with floors covered in debris. Metal shavings found around machining centers are a typical example. The caster manufacturer will look for tread and wheel material that can resist picking up the metal, and quickly shed it if some is attached.
One particular type of challenging surface for casters is sand or loose particles. The sand can be in the form of debris covering on a concrete floor, for example, or the entire working area might be sand or small sized gravel, as found outdoors in material storage yards or construction sites. Here, we’ll talk about some of the modifications that caster manufacturers have made to their products, to help them function in sandy or loose particulate applications.
Gritty Indoor Applications
In an iron foundry, hot melted iron is poured into molds made of sand. The iron is allowed to cool until it hardens. The newly formed part is separated from the sand, by a variety of methods – all of which can shower sand across the floor.
Sand blasting operations shoot sand (or other particles) at high velocities at glass to etch designs, at metal to create textures or remove coatings, or at other materials. Despite efforts to control and collect the sand, the floors that casters must roll over will often be covered with coarse grit.
Food processing facilities can produce loose particulates. In a nut processing facility, the shells are separated from the nut inside. Bits of the shell can be spread across the floor, and form rough surfaces for casters to traverse.
The sand and other particles mentioned in these three examples present a different debris challenge to casters than do metal shavings. The main problem with metal shavings comes from their sharp edges – if the wheel tread material is not carefully chosen to specifically reject the metal shavings, they can cut into the tread, embed themselves, accumulate over time and destroy the wheel. Sand, on the other hand, presents two different problems.
The first problem with sand and particles stems from their abrasiveness. Rather than cut into the caster tread, like metal shavings can do, sand will grind it down.
The second problem that loose particles present is their ability to work their way into bearings, and prevent them from rolling smoothly. This problem is made worse by the small size of particles that can result if sand, for example, is repeatedly crushed, eventually forming an abrasive powder that can waft through any openings in the bearing raceway.
Manufacturers have designed optional features for their casters that can help with these two problems.
- Tread Material for Wheels – This can be designed to disperse sand or loose particles. Check with your caster manufacturer or distributor, and find out which tread material will reject the pickup and accumulation of abrasive particles. Your wheels will last longer, if they never pick up the particles in the first place; or shed them in the fastest possible time.
- Sealed Bearings – The standard caster offerings from manufacturers usually come with bearings that are not sealed. However, sealed bearings are an option with many models. If your equipment must operate in situations where abrasive sand or other particles are present, then you may want to consider using casters that have sealed bearings.
Other specifications for casters and wheels can help. Larger diameter wheels spread the load out over a wider area; less pressure per square inch of tread surface means the tread will be less likely to pick up any particles, and abrasive effects from the particles will be reduced. Round tread wheels instead of flat tread can sometimes be beneficial, for the opposite reason – they present less tread area to the abrasive particles, which can lessen their impact.
Soft or Sandy Outdoor Situations
In an outdoor setting like a landscape nursery, material-handling carts might be required to traverse sandy soils. This is very different from the applications with grit-covered floors discussed above. In an outdoor application, the challenge is to keep the casters rolling on top of the surface, and avoid sinking into it.
The best way to meet this challenge is often to use pneumatic (air-filled) tires. Select wheels with as large a diameter as possible, in order to get the most tread in contact with the surface. Increasing the tread width will also increase surface contact, which will help “float” the wheel on the surface of the sand or other particles.
Are You Using Casters on Sand or Loose Particles? Call Douglas Equipment!
We hope this knowledge will help you think about and understand some of the problems you might face if you need to choose casters that will work well around sand or other particles.
If your application involves sand or loose particles, that there are casters available that will work well for you. For help in specifying options like the best tread material, wheel shape, or sealed bearings, contact the experts at Douglas Equipment by phone at 800-451-0030, or 305-888-3700 in the Miami area. You can also reach us through our online form. We look forward to hearing from you soon.