Damaging out of balance pressure is determined when thick and thin filter cakes are discharging from the filter platepack. This condition should be corrected as soon as possible to prevent filter plate damage. Normal low pressure differentials occur regularly and will flex the plate web within the design parameters. This flexing does not overstress the plate web and is normally not detected by operations.

Caused by the reasons:

1. Different permeability and separation characteristics of the filter cloths used inside the same plate stack

2. Blocked slurry feed holes

3. Plugged filtrate porting

4. Bridging of the feed hole between plates (fast filtering slurries)

5. Too high feed velocity

6. Different chamber depths (cake thicknesses) inside the same stack

Filter press chambers fill in two stages:

Build up of two separate cakes on both filter surfaces inside the chamber.

Growth of the two separated cakes into one single cake.

Out of balance pressure starts when the two separate “face”cakes become one. Once a chamber fills up completely with dry solids the feed pressure can no longer spread evenly from the feed channel to all the filter area. A rapid pressure loss through the cake to the inside of this chamber takes place. If the neighboring chamber still has two “face” cakes then a dangerously high out of balance pressure is exerted on the plate web which separates the chambers. This pressure can be as much as the feed pressure that is being generated at that time.