The sealing technology of high efficiency filter is generally divided into three categories, including contact packing seal, liquid tank knife edge seal and negative pressure leakage seal. The sealing of clean room and high efficiency air filter is one of the key factors to ensure the cleanliness of clean room. Therefore, advanced sealing technology and reliable sealing method should be selected when designing clean room, Next, Guangzhou Zijing will explain the three categories of sealing technology of high efficiency air filter:
1. Contact packing seal
The packing for sealing includes solid gasket (such as neoprene plate, closed cell sponge rubber plate, etc.) and liquid sealant (such as silicone rubber, neoprene, natural rubber). The solid sealing gasket is generally mechanically compressed by bolts, and the compression amount of rubber plate is 30% ~ 50%. When liquid sealant is used, it is sealed by filling and adhesion methods.
2. Liquid groove knife edge seal
A certain height of sealing liquid is injected into the grooved frame, and the knife edge of the high-efficiency air filter is inserted into the sealing liquid to block the air passages on both sides to achieve the purpose of sealing. This method is generally used for the sealing of clean rooms with cleanliness levels of 100, 10 and higher.
3. Negative pressure leakage seal
This "sealing" method uses the air leaked from the positive pressure space to artificially dredge the negative pressure space outside the work area to ensure that the work area is not polluted. It is generally used for sealing small-scale clean rooms, such as negative pressure ceiling, etc.
The high-efficiency filter is the key component of the air cleaning system. At present, the filter materials used in China are ultra-fine glass fiber paper and ultra-fine asbestos fiber paper, which are used to filter those that cannot be filtered by the coarse and medium efficiency filters, and the content is up to 1 μ Micron particles below m ensure the cleanliness requirements of clean rooms.
In order to ensure the filtration efficiency of the filter and the cleaning effect of the cleaning system, the installation of high-efficiency filter must comply with the requirements of code for construction and acceptance of clean room or design drawing.
1. Preparation before installation: in order to prevent the high-efficiency filter from being polluted, the unpacking inspection and installation must be carried out after the installation of the air cleaning system, the cleaning of the air conditioner, high-efficiency filter box, air duct and clean room, the test run of each single equipment of the air conditioning system and the stabilization of the amount of dust blown out from the air duct.
Before installation, check the straightness of the end face of the filter frame or edge, and the allowable deviation of the end face flatness shall not be greater than 1mm.
If the flatness of the end face exceeds the allowable deviation, only the frame end face of the filter installation can be modified or adjusted, and the outer frame of the filter itself is not allowed to be modified, otherwise the filter material or sealing part in the filter will be damaged and the filtering effect will be reduced.
2. Installation requirements when installing the high-efficiency filter, ensure that the air flow direction is consistent with the direction of the arrow mark on the outer frame. When the high-efficiency filter assembled with corrugated plate is installed vertically, the corrugated plate must be vertical to the ground and shall not be reversed. The sealing of high-efficiency filter and the frame for assembling high-efficiency filter generally adopts top tightening method and pressing method. For the cleaning systems with strict cleanliness requirements above grade 5, some use the knife rest type high-efficiency filter liquid tank sealing device.
(1) Installation of top tightening method and pressing method. The characteristics of top tightening method can install and replace high-efficiency filters in the clean room. The installation method is shown in Figure 10-35. Due to the characteristics of compression method, high efficiency filters can only be installed and replaced in the ceiling or technical interlayer
During installation, the filter shall be handled with care. It is too small to be polluted. It shall not be knocked or impacted with tools. It is strictly prohibited to touch the filter paper with hands or tools to prevent damage to the filter material and sealant. The sealing of high-efficiency filter and frame generally adopts closed cell sponge rubber plate or neoprene plate, and silicone rubber is also used for coating and sealing. The thickness of sealing gasket is usually 6 ~ 8mm, which is positioned and pasted on the filter frame, and the compression rate after installation shall be 25% ~ 30%. The splicing method of sealing gasket is alternate with the splicing method of flange connection gasket of air duct of air cleaning system, that is, trapezoidal or tenon splicing is adopted.
When the double ring seal is adopted for the seal between the filter and the frame, do not block the hole on the ring cavity. Both double ring seal and negative pressure seal must keep the negative pressure pipeline unblocked. In order to improve the sealing effect of the combination of "seal and guide", if there is no design requirement, the filter with side length less than 484mm shall be provided with one hole on one side and one to two holes on one side; For the filter with side length less than 630mm, one hole shall be opened on one side and two holes shall be opened on both sides; For filters with a side length of more than 630mm, two holes shall be opened on one side, and holes shall be opened on both sides.
For the sealing of filter and frame, if silicone rubber is used as sealing material, in order to ensure good sealing, the sundries and oil stains on the filter and frame shall be cleaned before applying silicone rubber, and then the chain rubber shall be fully and evenly applied.
(2) Installation of liquid tank seal the method of liquid tank seal is a sealing method developed to improve the cleanliness of the clean room. It overcomes the shortcomings of the pressing method, such as loose filter seal, aging and leakage of sealing cushion, long replacement and disassembly cycle, etc. due to the poor flatness of the frame end face.
The sealing device of liquid tank is made of two-way, three-way and four-way groove connectors pressed with aluminum alloy plate, which are connected and assembled with screws.