Pressure belt filters are commonly used to clean cooling lubricants, such as in the metalworking industry. Among other things, one of the basic processes in metal working is machining, such as machining or grinding. Friction between the tool and the workpiece generates heat during machining and produces chips and metal particles. So-called cooling lubricants are used to reduce the heat generated and carry away the resulting chips and metal particles. These working fluids must be thoroughly cleaned in order to obtain the best cooling and lubricating properties during operation. Careful cleaning not only significantly extends the service life of the cooling lubricant, but also greatly protects the environment. In addition, cooling lubricant cleaning helps to obtain better surface quality and increase cost effectiveness during processing.