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Johnson wedge wire screens

Jan. 07, 2019

Johnson wedge wire screens specifications and inquiry links: Wedge wire screen

                                                                                                       Wedge wire filter

Johnson wedge wire screens are widely used in the filtration industry, Today I will introduce its application in water treatment in detail.


The advantage of Johnson wedge wire screens filter


- Firm structure

- No clogging

- Low-pressure drop

- Easy to clean

- Acid-alkali corrosion resistance

- Long service life


Defects of Johnson wedge wire screens filter


- Filtration accuracy is more than 25 microns (>/=25 microns)

- Small filtration area


Comparisons of Johnson wedge wire screens filter with other types of the metal filter element (In water treatment)


- High filtration accuracy is required: Pleated filter element & Sintered filter element

- Large filtration area: Pleated filter element

- Bad filtering environment to prevent blockage: Johnson wedge wire screens filter

- Fine Particle Impurity Capture: Sintered filter element

- Low-pressure drop: Johnson wedge wire screens filter

Filtration Principle and Operation Mode of Water Treatment

The water quality of raw water is very complex, and it needs a series of filtration steps to get the required water quality, so the filtration process of water treatment is necessary.


Filtration is the separation of suspension by using a porous medium.

Two of the most common applications in water treatment are:

Johnson wedge wire screens filter

Sintered filter element


When working, under the action of external force, the liquid in the suspension flows out through the channel of the medium, and the solid particles are intercepted, thus realizing separation.

In general, the suspension to be filtered is called filter slurry; the porous medium used is called filter medium; the liquid passing through the channel of the medium is called filter fluid; the solid being intercepted is called filter cake or filter residue.


The driving force of the filtration operation is the pressure difference between the upstream and downstream sides of the filter medium. There are several ways to produce a pressure difference as follows:

- Utilizing the Pressure of the Filter Pulp

- Pressure on the surface of filter pulp

- Vacuum pumping on the downstream side of the filter medium

- Utilizing Inertial Centrifugal Force


Filtration operations can be divided into two categories according to the principle of action.


- The number of holes in the filtration medium is less than the diameter of solid particles, and solid particles are removed from suspension by sieving.

- Adsorption filtration (deep bed filtration): The number of mesh holes in the filter medium is larger than the diameter of solid particles. Solid particles are adsorbed on the surface of the media after entering the channel of the filter medium.

In actual production, sieving and adsorption act simultaneously, and the adsorption filter medium intercepts larger particles; the cake layer of sieving filter medium can adsorb smaller particles.


Filtration media and filter aids


The commonly used filter media are the following types:


- Fabric media, such as industrial filter cloth, wire mesh, etc.

(Wire mesh: Sintered wire mesh, Johnson wedge wire screens)

- Granular media, such as perlite powder, cellulose, diatomite, etc.

- Solid cardboard, such as decolorized wood cardboard, synthetic fiberboard, etc.

- Filtration membranes consisting of cellulose and other polymers


The Johnson wedge wire screens (filter) produced by ZHEHAN is mainly used in the pre-filtration process of water treatment.


The way of the filtering operation


Constant pressure filtration


Constant pressure filtration is carried out under constant pressure difference, which is called constant pressure filtration.

Constant pressure filtration is the most commonly used method of filtration. In the process of filtration, with the increasing of the cake layer, the resistance increases. Because the pressure difference remains unchanged, the filtration speed will gradually decrease.


Constant speed filtration


The filtering operation is carried out at a constant speed, which is called constant speed filtration.

With the continuous filtration time, the cake layer thickness increases, the resistance increases, and the filtration pressure difference increase linearly with the continuous time.

The pressure resistance of filter equipment is limited and the pressure cannot be too high. For compressible filter cake, excessive pressure does not increase the speed, on the contrary, it will cause the termination of filtration.


Firstly constant speed and then constant pressure filtration


This kind of filtration method is to start with constant velocity filtration at a lower speed, so as to avoid the blockage of the flow passage caused by the premature rise of pressure, and then use constant pressure filtration when the pressure rises to a given value.

The constant speed is maintained in the initial stage of filtration by using a quantitative pump, and the pressure at the outlet of the pump increases with time. If the pressure rises to a set value that can automatically open the branch valve, the branch opens, and part of the filter slurry returns to the inlet of the pump. The slurry entering the filter press decreases, and the pressure at the inlet of the filter press keeps constant, so constant pressure filtering begins.


Factors Influencing Filtration Speed and Johnson wedge wire screens


- The bigger the viscosity and viscosity of the filter pulp, the bigger the filtration resistance and the smaller the filtration speed.

- The bigger the cake thickness is, the bigger the resistance is and the smaller the filtration speed is. When the thickness reaches a certain level, the filtration will be terminated.

- The particles of the incompressible cake are hard. The channel through which the filtrate passes will not decrease with the increase of pressure. The resistance will remain basically unchanged, or it will increase slowly with the continuous resistance of filtration time. The filtration speed will increase proportionally with the increase of pressure.

Small particles will block the channel under higher pressure, so the initial pressure should not be too high to avoid premature blockage of the channel.


The theme of our article is Johnson wedge wire screens, I'm here to introduce the precautions before purchasing.


- Slot Error Detection

- Material testing

- Roundness detection


That's the end of this blog. ZHEHAN as a professional Johnson wedge wire screens manufacturer in China,  Welcome global customers to communicate on our website.


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