As an effective filtration medium, filter paper has been widely used in various fields. According to the types of fibers that make up the filter paper, the performance and use of the filter paper are also different. It can be used for common filter paper for general occasions, glass fiber filter paper for high temperature, and polypropylene filter paper for ultra-clean.
The structure of filter paper is a labyrinth structure composed of fibers and channels, which together with the physical forces associated with the fluid constitute the filtering function of filter paper. The filtration mechanism is as follows:
1. Direct capture or interception
In this process, some people mistakenly believe that it is the only factor forming filtration, and that the dirt particles are blocked in the inflow surface or labyrinth only because they are larger than the aperture. In fact, there are:
2. Adsorption
When the filtered fluid passes through the labyrinth, some particles are adsorbed to the filter paper under the action of electrostatic attraction, although the diameter of some particles is much smaller than the aperture. Therefore, some filter materials are specially made with static electricity during the manufacturing process.
3. Hit and fall
In this process, due to the relationship between flow rate, the particles are trapped directly on the surface of the filter paper fiber rather than in the pore of the filter paper, and the adsorptive force and fluid flow force are maintained on it, thus blocking some smaller particles.
4. Filtration and agglomeration
With the continuous accumulation of dirt particles on the surface of filter paper, it forms a filter layer itself, which traps smaller particles in the pores between large particles. With the increase of particles, the resistance increases continuously, until finally completely blocked or reached the differential pressure.
The production of filter paper is very simple. It is just that a variety of fibers are soaked in water-based binders to disperse them completely, and then form a tightly bonded connection paper roll on the silk screen. Through drying, dipping and drying, the acceptable humidity level is achieved. But in fact, the production of efficient filter paper, keeping the same performance between batch and batch, roll and roll, even between years and years, will require its weight, porosity, permeability, strength and other changes in a narrow range.
The filter material in the filter must prevent the filter system from being damaged by harmful particles, and at the same time allow enough fluid to pass through, so as to avoid cavitation in the pump, work cylinder and combustion chamber. In theory, a perfect filter should remove 100% of the contaminated particles and provide consistent air permeability. But in fact, this is impossible.
The design of filter paper must make every effort to balance the various indicators in order to effectively protect the system to be filtered. Oil filters have higher requirements for filter paper than air filters, mainly because the concentration of oil changes correspondingly under drastic temperature changes, which will affect the filtration flow of oil.
Post time: Nov-21-2018