Difference between surface filtration and deep filtration

Screen material is mainly used for surface filtration and felt material is used for deep filtration. The differences are as follows:

1. The screen material (nylon monofilament, metal monofilament) directly intercepts the impurities in the filtration on the surface of the material. The advantages are that the monofilament structure can be cleaned repeatedly and the consumption cost is low; But the disadvantage is the surface filtration mode, which is easy to cause the surface blockage of the filter bag. This type of product is most suitable for the coarse filtration occasions with low precision, and the filtration precision is 25-1200 μ m 。

2. Felt material (needle punched cloth, solution blown non-woven fabric) is a common deep three-dimensional filter material, which is characterized by loose fiber structure and high porosity, which increases the capacity of impurities. This kind of fiber material belongs to the compound interception mode, that is, the larger particles of impurities are intercepted on the surface of the fiber, while the fine particles are trapped in the deep layer of the filter material, so the filtration has higher filtration efficiency, In addition, the high temperature surface heat treatment, that is, the application of instant sintering technology, can effectively prevent the fiber from losing due to the high-speed impact of fluid during filtration; The felt material is disposable and the filtration accuracy is 1-200 μ m 。

The main material properties of filter felt are as follows:

Polyester – the most commonly used filter fiber, good chemical resistance, working temperature less than 170-190 ℃

Polypropylene is used for liquid filtration in chemical industry. It has excellent acid and alkali resistance. Its working temperature is less than 100-110 ℃

Wool – good anti solvent function, but not suitable for anti acid, alkali filtration

Nilong has good chemical resistance (except acid resistance), and its working temperature is less than 170-190 ℃

Fluoride has the best function of temperature resistance and chemical resistance, and the working temperature is less than 250-270 ℃

Comparison of advantages and disadvantages between surface filter material and deep filter material

There are many kinds of filter materials for filters. Such as woven wire mesh, filter paper, metal sheet, sintered filter element and felt, etc. However, according to its filtering methods, it can be divided into two types, namely surface type and depth type.

1. Surface filter material
Surface type filter material is also called absolute filter material. Its surface has a certain geometry, uniform micropores or channels. It is used to catch the dirt in the blocking oil. The filter material is usually plain or twill filter made of metal wire, fabric fiber or other materials. Its filtering principle is similar to the use of precision screen. Its filtering accuracy depends on the geometric dimensions of micropores and channels.

Advantages of surface type filter material: accurate expression of precision, wide range of application. Easy to clean, reusable, long service life.

The disadvantages of surface type filter material are as follows: small amount of contaminant; Due to the limitation of manufacturing technology, the precision is less than 10um

2. Deep filter material
Depth type filter material is also called deep type filter material or internal type filter material. The filter material has a certain thickness, which can be understood as the superposition of many surface type filters. The internal channel is composed of no regular and no specific size of deep gap. When the oil passes through the filter material, the dirt in the oil is caught or adsorbed at different depths of the filter material. So as to play the role of filtration. Filter paper is a typical deep filter material used in hydraulic system. The accuracy is generally between 3 and 20um.

The advantages of deep type filter material: large amount of dirt, long service life, able to remove many particles smaller than the precision and strip, high filtering precision.

Disadvantages of depth type filter material: there is no uniform size of filter material gap. The size of the impurity particles can not be controlled accurately; It’s almost impossible to clean. Most of them are disposable. The consumption is large.

Post time: Jun-08-2021