FFU fan filter unit, referred to as "FFU", is a high-efficiency filter air outlet with its own blower (shellless fan), which together with its special keel system, pressurized fan, cooling coil, fresh air system and special lamps to form the FFU system. It is the combination of a fan and a filter (HEPA or UHPA filter) to form an end-of-line purification device that can be powered on its own. In the past, the air supply port of the high-efficiency filter with a fan, the self-purifier, and the laminar flow hood were all commonly used in the clean process.
Because FFU uses self-circulating filtration and air supply, the clean air in the static pressure chamber is sent to the purification workshop through efficient filtration, deodorization and sterilization treatment, and the air dust particles in the purification room are controlled within a certain range according to the amount of air supply. It has an advanced and scientific structure, and adopts a special diversion air duct and air sharing system design to reduce vortex, eliminate noise, and guide the air flow to pass through the filter screen evenly, with the characteristics of uniform wind speed and low noise. It is widely used in the end air outlet system of the central air conditioning of the 100-level and 1,000-level purification plant in the electronic semiconductor, pharmaceutical, medical operating room, precision manufacturing industry and other industries, and is also suitable for the air supply unit of the clean workbench and dust-free workbench.
In addition, the following issues should be paid attention to when choosing to install FFU.
1. Noise control
The fans of the FFU fan filtration unit are generally used in parallel for several or even dozens of units, and the superposition of FFU noise should be considered when designing, so as to ensure that the "Clean Room Plant Design Code GB50073-2001" clearly stipulates that "the noise level (empty state) in the clean room, the non-unidirectional flow clean room should not be greater than 60dB, and the unidirectional flow and mixed flow clean room should not be greater than 65dB". Therefore, when choosing a fan, choose a high-performance, extruded, direct-drive rear radial blade fan, which can reduce the overall noise.
2. Selection of fan housing
When choosing the structure of the FFU fan shell, it is not only necessary to consider avoiding fan leakage and eliminating the damage caused by transportation and handling, but also to consider the environment that can be disinfected with disinfectant and the FFU is used, so stainless steel or aluminum alloy materials are selected as the shell.
3. The selection of the keel
Since the FFU fan filter unit is directly installed between the ceiling skeletons, in order to make the filter easy and quick to replace, but also to keep the FFU fan operation balanced, and reduce the probability of installation imbalance. Therefore, the professional supporting keel is generally considered. This kind of keel frame is a section steel with a special geometric shape (U-shaped) that is mechanically cold-rolled, and the metal surface is treated with anti-corrosion treatment (such as electrostatic spraying, hot and cold galvanizing, epoxy, etc.) according to its different environments, which can not only ensure the strength of similar channel steel, but also meet the needs of FFU operation.
4. Selection of control mode
At present, FFU generally uses single-phase multi-speed AC motors, three-phase multi-speed AC motors and DC motors. There are four types of power supply voltages for motors: 110V, 220V, 270V, and 380V.
Its control methods are mainly divided into the following types:
(1) Multi-gear switch control system: This system only includes a speed switch and a power switch that comes with FFU. Because the control elements are FFU and are distributed in various positions in the clean room ceiling, the staff must adjust the FFU through the toggle switch on the spot, which is extremely inconvenient to control, and the wind speed adjustable range of the FFU is limited, limited to a few gears. The advantages of using multi-gear switch control mode are simple control and low cost, but there are many defects: such as: high energy consumption, can not smooth speed regulation, no feedback signal, can not achieve flexible group control, etc.
(2) Continuous speed adjustment control: Compared with the multi-gear switch control mode, the continuous speed adjustment control of this system has an additional continuous speed regulator, which makes the speed of the FFU fan continuously adjustable, but at the same time, it also sacrifices the efficiency of the motor, so that its energy consumption is higher than that of the multi-gear switch control mode.
(3) Computer control: Compared with the previous two methods, this system has advanced functions of computer control mode: not only can the distributed control mode be adopted, which can easily realize the centralized monitoring and control of FFU, but also can easily realize the single, multiple and partition control of FFU. In addition, the control system can be set up to reserve the communication interface, which can communicate with the host computer or the network, so as to realize the remote communication and management function.
(4) Remote control: As a supplement to the computer control mode, the remote control mode of this system can use the remote control to control each FFU, which complements the computer control mode. These control methods should be selected according to the actual situation when selecting.
5. Maintenance and management of FFU
When the FFU air supply mode is adopted, it is often not a single equipment but dozens or hundreds of FFUs arranged on the ceiling, so it brings certain difficulties to maintenance and management. Generally, the high-efficiency filter is replaced from the clean room, and most of the fans need to be maintained at the top of the keel (inside the hydrostatic pressure box), but if the static pressure box is not high enough to maintain the fan from the inside, then the feasibility of maintaining the fan from the inside of the clean room should be considered. In short, the application of FFU should be considered according to the actual situation, so as to achieve the purpose of retaining its characteristics and reducing costs.
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