Air blowdown:

at the end of the filtering process through the inlet pipe we blow air at high pressure into the closed filter pack. The air eliminates the filtrate left in the filter pack’s channels and in discharge piping and it dries the filter cake.

Automatic plate shifting:
the plates are separated by a plate shifting device. In this case plate shifting does not require manpower.

Cake discharge:
the process of eliminating from the filter press the cakes formed in the chambers. It happens at the same time as plate shifting.

Chamber filter plate:
it is the simplest and most frequently used filter plate. Because of this design it is “only” able to form the filter cake, inlet the material to be filtered and to discharge the filtrate. According to its function: it might be head plate, intermediate plate and tail plate.

Chamber filter press:
is a device used for the solid/liquid separation of sludge. The figure below illustrates the simplest chamber filter press. Way of functioning: The filter cloth covered filter plates (filter pack) are pressed together by a hydraulic cylinder. Then at high pressure a pump fills the chambers between the filter plates with material to be filtered. The particles that are smaller or of the same dimension as the filter cloth’s capacity leave the filter press as filtrate, while the others are withheld in the chambers. These particles form the filter cakes, which can be eliminated after the filter plates are opened. (filtering process)

Chamber volume:
it is the volume that the material to be filtered can fill. It can be calculated either for one filter plate or for the whole device.

Content of solid material:
is a characteristic feature of the material to be filtered and of the cake. It is always given in volume percent; the absolute content of solid material is relevant.

Discharge channel:
it is the piping system through which the filtrate leaves the filter press and heads to its destination (container or sewer).

Discharge:
after squeezing a pump forces the water out of the filter press.

Discharging pump:
after post dewatering this pump forces the water out of the membrane plates. Obviously in case of post dewatering by air this device is not required.

Drip tray:
it is an inclined metal or plastic tray provided with edges. It is situated under the filter pack. Its aim: when the material to be filtered is not so dense, it may leak. The drip tray leads this amount of liquid into the drip trough. According to its design it can be static or it can be opened. In the second case the drip tray’s function is increased: in opened position the falling cakes fall under the filter press into dumpers.

Drying:
the same as air blowdown.

End plate:
this is the “last” plate of the filter pack. It is situated on the on the follower head side of the metal structure. It conveys the hydraulic cylinder’s pressure to the other plates in the filter pack and transmits the forces deriving from the feeding and pressing back to the follower head. Its pattern is similar to the head plate’s one, but the inlet bore is missing and the filtrate discharge pipes close on the follower head’s side.

Feeding pump:
it is the pump that forces the material to be filtered into the filter press. It is usually a diaphragm pump or eccentric screw pump.

Feeding valve:
it is the valve that regulates the flow of the material to be filtered in the inlet piping. It is usually a ball or a butterfly valve.

Feeding:
the process of letting the material to be filtered into the filter press. It is usually done by a pump, but it may be done due to the gravity.

Filter cloth:
this is the element of filter plate that filters. Its parameters decide which parts of the material to be filtered leave the filter press as a filtrate, and which parts will be stacked to form the cake.

Filter pack:
total number of filter plates in a filter press. Standard elements are: 1 pc head plate, X pc intermediate plates, 1 tail plate – in case of single-sided feeding; or 2 pc head plates in case of feeding from both sides.

Filter plate:
part of the filter press that carries and supports the filter cloth. Its pattern ensures the formation of filter cakes, and thanks to its ports it enables the free flow of material to be filtered, filtrates and the material used for post dewatering. It is usually made of polypropylene, poliamid, polyester, PVC and so on.
According to their position in the filter pack we speak of:
- head plates
- end plates
- intermediate plates
According to their function we speak of:
- chamber filter plates
- membrane filter plates
- washing plates
- combination of these
- other specially designed plates
All these filter plate types are also available in gasketed version.
Their most important parameters:
- size
- position of the inlet and discharge channels
- max. applicable pressure on pressure on filter plates
- chamber volume
- dimension of the filtering surface
- type of material

Filtering surface:
it is the surface of the filter cloth that is effectively met by the material to be filtered. It can be calculated either for one filter plate or for the whole device.

Filtration cycle:
- feeding
- prepressing (rare)
- washing
- squeezing
- air blowdown
- cake discharge + plate shifting
In the simplest cases prepressing, washing and squeezing may be omitted.

Gasketed filter plate:
it is a special filter plate. There are O-rings on its surface, and it allows the use of filter cloth that ensures its gasketed characteristic. Its most important feature is that when the filter pack is closed it is tight sealed, due to the o-rings on its surface, so it is hermetically closed during the feeding. It means that when the filter press is operating neither liquids nor gas can leave the filter press unless in the appositely formed piping.

Head plate:
the “first plate” in a filter pack and it is situated on the feeding side of the filter press’s metal structure. When the filter press is closed the head plate conveys to the filter press’s metal skeleton the pressures that come from the feeding pressure and the closing hydraulic cylinder. Moreover the material to be filtered enters the filter pack here and the filtrate leaves the device through this plate.

Inlet channel:
it is the piping system through which the material to be filtered enters the filter press.

Intermediate plate:
in the chambers of the intermediate plates form the filter cakes, and these plates ensure the discharging of the filtrate.

Manual plate shifting:
the plates are separated manually by handles that are situated on the plates.

Marks on filter presses:
in our company the marks are always built up in the same way. Example: MFP 800/40, where the first three letters stand for: membran filterpresse or membrane filter press. The letters can be also KFP (Kammerfilterpresse) or chamber filter press. In the first case the filter pack is formed by membrane filter plates or by mixed filter plates. In the second case the filter pack is made up by chamber filter plates. The numbers stand for: 800 is the measure of filter plates in mm (in the case if the most frequently used square shaped filter plates this is also the length of the edge). 40 stands for the number of chambers in the filter press. The number of chambers is always one less than the number of filter plates.

Membrane filter plate:
it is a special chamber filter plate with all of its characteristics. The difference is that the membrane filter plate is delimitated by a flexible plastic element on both chamber sides, and it is hollow inside. When it is filled with a substance at high pressure the membrane filter plate’s volume grows laterally and presses the filter cake. This is the so-called post dewatering process. Obviously, it is available in head plate and tail plate versions as well.

Piping for squeezing:
the squeezing medium enters and leaves the filter press through this piping.

Plate shifting:
after opening the filter press the plates are separated. This can happen automatically or manually.

Pump for squeezing:
it forces the squeezing water into the membrane plates and gives the right pressure for squeezing.

Slurry container:
tank designed to hold the material to be filtered.

Squeezing container:
it holds the water used for squeezing. This is where the pump for squeezing sucks up and pumps back the water used for squeezing.

Squeezing valve:
in systems where the squeezing medium is water the pressing water enters and leaves the filter press through the same piping. The difference is that the first process is carried out by the pump for squeezing while the second one is carried out by the discharging pump. It is the position of the sqeezing valve to decide which pump the piping is in connection with.

Squeezing:
we force water or air at high pressure into the membranes of the filter press. In this way the membrane plates dilate (squeezing is possible only in case of filter press with membrane filter plates) and presses the filter cakes formed by the end of the feeding process. The max. pressure of squeezing is usually 16 bar, but filter presses or membrane plates that can withhold up to 30 bar pressure are also available. The advantage of this process is that the cake is dryer than in a process where this pressure is made by the feeding pump, and it speeds up the filtration process. (diagram)

The most important parameters of chamber filter press:
- type of filter plates used
- number of filter plates
- total volume of chambers
- total filtering surface
- pressure and flow of feed pump
- pressure of the filter press closing hydraulic cylinder
- geometric measures

Washing plate:
is a special intermediate plate, which due to its channels allows us to make water circulate through the filter cake, which has been already formed. In this way we are able to eliminate the non desired elements from the cake. There are chamber washing plates and membrane washing plates.