High temperature use
Standard M, J and O Series castors have a temperature range of 5°C to 60°C. As temperatures increase, wheels become weaker, which lower their load capacity and shorten their lifespan. It is important that you specify the temperature and type of application before ordering a castor, to ensure that the appropriate wheel type is selected. We make three different wheel types designed specifically for use in high temperature environments. These specialised wheels use standard lithium complex grease (STABUTHERM® GH 461) which has excellent water resistance (24 hrs at 90°C), bearing retention and long life.
Glass filled nylon (150–230°C)
The best choice for hospitality based applications such as ‘food baking’ ovens, glass filled nylon can sustained high temperatures and is gentle and quiet on most floor surfaces. Fibreglass reinforced nylon wheels are the preferred wheel for extended periods of up to 210°C (assuming most of their life is spent outside the oven), and for short periods up to 230°C.
Phenolic is more brittle than glass filled nylon and it has a shorter life cycle but can go up to very high temperatures. Phenolic is a good choice for light duty industrial applications with very high temperatures such as ovens used for curing paint. The load capacity decreases from 125 kg at 100°C to 40 kg at 300°C therefore it is very important to ensure that the load capacity of the trolley fits within the appropriate temperature and load capacity.
Phenolic wheels (with special inorganic fillers and PTFE bushes) are preferred for extended periods up to 280°C assuming most of their life is spent outside the oven and for short periods up to 300°C. These have a thick cross section, but are more brittle than either nylon or ordinary grades of phenolic. Please note that phenolic wheels are not suitable for medium duty applications or applications where wheels are subjected to impact such as when a trolley is rolled down steps.
Cast iron (200–400°C)
The best choice for Industrial based applications such as ‘paint curing’ ovens and also for use in sustained high temperature environments, cast iron wheels can withstand extreme high temperatures as well as higher load capacities than all other wheel types. Cast iron wheels do not have bearings. They have a plain bore fitted with an axle spacer that is lubricated with high temperature grease. This grease can be used up to 230°C for long periods. For temperatures that exceed 230°C a more exotic grease is required. For sustained high temperature use, we offer a range of cast iron wheeled castors used with high temperature grease. Please note that cast iron is heavy, noisy and may damage concrete floors and other floor surfaces.
Low temperature use
Below 5°C you must specify temperature of use at the time of ordering. The standard grease we use in our castors is a lithium complex grease. This has excellent water resistance, bearing retention and long life. However below 5°C it begins to stiffen quickly, and will soon freeze the bearings so that neither the castor swivels nor the wheel bearings revolve. If specified at the time of ordering, we use a special aeronautical grease which is a synthetic oil with a microgel thickener. This is compounded for use down to -30°C, and will need to be refreshed every 6–12 months, but will continue to work effectively in chilling rooms, freezing stores and outdoor winter use in northern countries where ordinary greases would be useless.
As the temperature becomes lower, the softer rubber and polyurethane treads on our wheels become less elastic. For example, the polyurethane used on the ‘H’ series slowly stiffens from +20°C down to -20°C, but then rapidly stiffens until at -50°C, when it becomes brittle.
As temperature goes below 5°C, nylon can become brittle (particularly if it is kept for long periods in the very dry air in freezing rooms). At such times we recommend glass filled nylon reinforced wheels, which can be used down to -30°C.