Key Technologies Of Cleanroom Design
- View 7
The whirlwind speed / ventilation of the clean room is a difficult problem in the cleanroom design. With the improvement of the operating performance of the pollutants in the clean room and the high efficiency of the final stage filtration device, the strong recommendations and standard values clearly put forward in the relevant standards and technical specifications are biased to the transmission.
Many studies show that the noise, damage detection and other problems existing in the operation of FFU have been practically solved Therefore, with the improvement of FFU, whether to choose FFU air supply system software is a hot spot on the network: the operation of floating molecular structure environmental pollution (AMC) has been scheduled in the production of electronic optics and IC industry to sort out and analyze the following situations of this problem.
Design concept of clean room
1、 Key elements of cyclonic velocity endangering clean room
According to a certain cleanliness level of the clean room, the cyclone speed is clear. According to the details of the main uses of the clean room, it is not only affected by the amount of dust in the room and the efficiency of the filter device, but also by other factors. For the clean room of industrial production, the important factors for the selection of cleanliness level and air rotation speed are.
(1) Indoor pollutants: the actual operation, technology, processing technology raw materials and processing technology of building components, total number of staff and theme activities are the sources of fine particulate matter release, and the specific situation is different.
(2) Indoor air flow pattern and diffusion: the single side flow provides a uniform and fair streamline, but due to the influence of technical configuration and part changes and the subject activity of the staff, the single side flow regulations that generate part of the eddy current are mixed together, unable to prevent dead angle and temperature level.
(3) Operation regulations of self-cleaning working time (repair time): operation regulations of self-cleaning working time to repair the original cleaning working time and determine the self-cleaning working time of cyclone speed During this time (varying cleanliness level).
(4) High efficiency of the final stage filter: under the dust emission in a certain room, select the high efficiency filter. In order to reduce the environmental protection and energy saving of the cyclone speed, select the high efficiency filter, reduce the cyclone speed, or select the uneconomical scale filter, select the high cyclone speed.
(5) Rationality consideration: the excessive cyclone speed leads to the increase of project investment and operation cost, and the suitable cyclone speed is the effective synthesis of the above factors, which is usually redundant and does not necessarily have practical effect.
(6) For clean rooms with low cleanliness level, ventilation sometimes decides to reduce the indoor temperature.
On top of these elements, there is no method for quantitative analysis, only and estimation. According to the application of the project, the cyclone velocity in the clean room usually refers to the strongly recommended and standard values such as relevant standards and technical standards, and estimates the hazard elements according to the detailed situation
2、 Calculation method of cyclone velocity in clean room
The cyclone velocity is used for the ventilation of the non single side flow cleanroom. Its cyclone velocity is represented by the over filling rate of the effective final stage which is difficult to measure. It is a cleanroom with various cyclone flow patterns. Generally, the filling rate is 100% water flow 0.5m/s (100fpm), 25% water flow 0.15%.
(1) The horizontal diffusion of the indoor cyclone separator can only be carried out at a very low speed. The unidirectional speed is an effective natural ventilation, and the removal rate of air pollutants is 0.050.1m/s. Therefore, the ideal self purification time tr volume / flux of the clean room reaches a certain value. By re entering the air pollutants, expanding the cyclone separation speed, the TR value is not significantly reduced.
(2) Attention should be paid to the harm of high efficiency of the final stage filter to the cleanliness level. Adhere to the highly recommended or standard values of rotation speed / air exchange, and generally do not consider the factors of efficient lifting of terminal filter screen. The efficiency of using today's HEPA / ULPA can be selected from 99.67%, 99.99%, 999%, 99.995% to 89%. According to the damage of high efficiency to the speed of cyclone separator, the next stage should pay more attention to the stable calculation of dust concentration in the clean room under the condition of non one side flow: (a) when the dust is high, The high efficiency conversion of terminal filter is very harmful to the cleanliness level. (b) under the condition of low dust generation in the room, the high efficiency gearbox conversion of the final stage filter device under the low cyclone rate is selected, which will increase the harm to the cleanliness level.
3、 Application of FFU system software in clean room cleaning
There should be no concern about using and maintaining early practical experience. The key to the improvement of tea is: (1) using average current and noise reduction measures, the noise is less than 50 dB; (2) using motor or DC / motor (rectifier motor of electronic components), compared with the original AC motor, it saves about 50%. Small volume (output > 1 / 2 horsepower) AC motor is usually used along the small blower, and the capacity comparison and pole type are generally used. Its efficiency is only about 40%, and DC / AC motor reaches 75-80%. In the variable-speed operation, the filter device can save energy by self crushing operation, but in this stage, the internal rate of return is still very long, there is no universal choice, and it is generally listed in the group control system.