To choose the right wheel, it’s also important to determine if the wheel materials are compatible with the chemical-environmental conditions, the temperature, the humidity and the inductive electrostatic phenomena that may affect wheel operation. The standard operating conditions are indicated in the manufacturer’s catalogue for each type of wheel.
Because there are so many different types of aggressive chemical agents in work environments, it’s difficult to provide a complete and exhaustive description.
The main chemical substances that a wheel may come in contact with include:
- weak acids (e.g. boric acid, sulphurous acid);
- strong acids (e.g. hydrochloric acid, nitric acid);
- weak bases (e.g. alkaline solutions);
- strong bases (soda, caustic soda);
- chlorinated and aromatic solvents (e.g. acetone, turpentine);
- hydrocarbons (e.g. petrol, oil, diesel oil, mineral oils);
- alcohol (e.g. ethyl alcohol);
- fresh water;
- salt water;
- saturated steam.
Therefore, when choosing a wheel, it’s very important to check if the material forming the covering, the wheel centre body, the rolling actions and the bracket is compatible with the specific features of the operating environment. Caution is required in those sectors in which water, acids, bases, steam and other aggressive agents are often present.
For example, a polyurethane wheel should be used instead of a tyred wheel in environments with a large quantity of oils, fats and hydrocarbons, while it is recommended to use stainless steel castors in humid environments and in the presence of high saline concentrations.
If operating temperatures in an application differ from the standard range of values indicated by the manufacturer, check the resistance of the wheel materials. This not only applies to the rolling strip and the wheel centre body, but also to the type of lubricant used (it may be necessary to contact the manufacturer). The indicative percentages of carrying capacity variation as a function of temperature are shown in the following table.
The above-mentioned variation values refer to the prolonged and continued use (over 30 minutes) of the wheels at the specified ambient temperatures.