The Automatic Pressure Filter


Pressure Belt Filter

Functional diagram of a pressure belt filter


Hoffmann Automatic Pressure Filter Systems are the most versatile filter systems for the metal working industry. Due to the variety of filter units, flow rates as low as 100 GPM to over 4,000 GPM are possible. All automatic pressure filter systems use an endless nylon belt that eliminates the need for filter media. However, for special applications, the units may utilize disposable filter roll media or cellulose, pre-coated on the nylon belt. Applications may range from entire transfer lines, groups of machining centers or grinders, as well as block hone lines. Additional fine filtration or wedge wire pre-filtration and coolant temperature stabilization may be added to complete the system to the customer’s requirements.

Advantages of the Automatic Pressure Filter:

  • No filter media
  • Fully automatic
  • Low maintenance
  • Self-regeneration
  • Continuously cleaned coolant
  • Easy set-up with exceptional results
  • High degree of filtration
  • High reliability


Hoffmann Automatic Pressure Filters are ideally suited for use in highly automated machine tool operations. These filters are opened and closed by two air cylinders, ensuring that the filter remains tightly closed, even in the event of a pressure loss.

Contaminated coolant is collected in the dirt tank and then pumped into the sealed filter chamber above the endless nylon belt. Contaminants are collected on the belt as the cleaned fluid flows through and the supply pump returns it to the machine tool. As contaminants build up to form a filter cake, the differential pressure across the belt increases until it reaches a preset limit. When this occurs, incoming flow is stopped, and the filter cake is dried by compressed air. The chamber then opens, and the filter belt conveys the cake into the sludge box.