Pressure Leaf Filter

The automatic pressure leaf filter is used wherever large quantities of oil are processed and manual effort is to be minimized.

Filter Caption

  1. Filter container
  2. Container lid
  3. Pivot screws
  4. Hydr. hoist
  5. Lifting arm
  6. Filter leafs
  7. Pneum. vibrator
  8. 8. Drain
  9. Cover flap
  10. Pneum. cylinder cover flap
  11.  Manometer

Operating principle

1. Cake suspension

The operation of the filter is based on the cake filtration principle.

The filter elements (filter leaves) consist of a frame covered with a fine-mesh metal net. Several filter leaves are arranged in the filter housing on the discharge pipe. The filter housing is filled with turbid oil under pressure. The oil penetrates through the surface of the filter elements into the interior of the frame and flows through the discharge pipe. The cake and filter aids collect on the surface of the filter leaves.This phase is called cake pre-coating. During cake pre-coating, the oil is returned to the unfiltered oil tank. Only when a sufficiently thick layer of filter cake has formed on the surface of the filter leaves can the filtered oil be diverted into the clean oil tank. This process can be accelerated by using filter aids.

2. Filtration

The sufficient formation of the cake on the filter elements is noticeable by the pressure increase and during the visual inspection. The duration of the filtration phase and the quantity of oil are determined by several influencing variables:

  • Oil temperature, which is decisive for the kinematic viscosity
  • Amount of sediment/particles in the oil
  • Particle size distribution of the cake – a variable which is strongly dependent on the operation of the oil press
  • Type and quantity of filter aids used (sawdust, cellulose…)
  • Filter surface

3. Regeneration

In this phase, the advantages of the pressure leaf filter compared to the use of chamber filter presses are apparent. This operation, and consequently the whole process, can be fully automated. Moreover, the filter elements made of metal mesh have a longer lifetime than the filter cloths of the chamber filter press.

When a certain pressure is reached, the supply of cloudy oil is stopped. The cloudy oil from the full filter is drained into the cloudy oil tank. The cake adhering to the filter elements is then “dried” by pressurizing it with compressed air. The air flowing out through the discharge pipe is very oily and is first led through an oil separator.

The dry filter cake can be easily detached from the filter elements by the pneumatic shaker. The filter cake is discharged from the filter by a pneumatic flap. The flap is closed again, the valves return to the positions for cake suspension, and a new filter cycle can be started.