Clean Room FFU
Clean room FFU refers to fan filter unit and can be modularized, which makes it widely used in clean rooms, clean benches, clean production lines and assembling clean rooms, local class 100 environment, etc.
Clean room FFU is equipped with primary and high efficiency filters. Air is sucked into the fan from the top of the FFU, filtered by the primary and high efficiency filters and then sent out from the fan outlet at a uniform velocity of 0.45M/S±20%. FFU is suitable for high-level clean environments and serves as an ideal facility for purifying environment. It can provide high-quality clean air for clean rooms and micro-environments of different sizes and different cleanliness levels, improve cleanliness level and reduce noise and vibration in newly-built clean rooms and renovated clean workshops, reduce costs greatly and facilitate installation and maintenance.
Application, classification and structure of the FFU
Application
Generally speaking, the clean room system contains an air duct system, an FFU system and an axial flow fan system;
Compared with the air duct system, the FFU system has six advantages:
(1) flexible
(2) recyclable
(3) capable of negative pressure ventilation
(4) shortening construction period
(5) cutting down on operating cost
(6) saving space.
In clean rooms with their cleanliness level being 1,000-grade (FS209E standard) or Level ISO6 above, as well as in locally clean environment, clean cabinets and clean benches, the FFU system is usually used.
Structure
1. Appearance
Split-type: Facilitating replacement and reducing workload during the process of installation.
Integrated type: Increasing air-tightness of FFU and thus preventing leakage effectively; conducive to reducing noise and vibration.
2. Basic structure
Main constitutive elements
1) Frame: clean room FFU's material is usually galvanized and aluminum alloy coated steel sheet, aluminum alloy or stainless steel. Its first function is to support the fan and the baffle loop, and the second is to support the air deflector.
2) Fan
3) Brushless motor
In terms of structure, the brushless motor shares similarities with the brush motor. Both of them have rotors and stators but with the opposite structure. The rotor of the latter is coil winding and connected to the power take-off shaft, while that of the former is permanent magnet and connected to the power take-off shaft together with its cover. The stator of the latter is permanent magnet, while that of the former is coil winding. The commutating brush used to alternating electromagnetic field in the brush motor is removed, so the former is called brushless motor. It is usually used in equipment with relatively high control requirements and high speed, such as model airplanes, precision instruments, etc.
4) Filter
Prefilter: Primary filter screen made of nonwoven fabric with frame and used to filter large dust particles;
High efficiency filter: HEPA/ULPA (high-efficiency/ultra-high-efficiency); eg. H14, efficiency being 99.999%@0.3um;
Chemical filter: Used to filter ammonia, boron, organic gas, etc., and installed at the air inlet in the same way as the prefilter.
Basic Parameters
1. Face velocity
Generally between 0-0.6m/s. For five-speed regulation, the corresponding velocity of each gear is roughly 0.3-0.35-0.4-0.45-0.5m/s, and for stepless speed regulation, the velocity is roughly within 0-0.6m/s.
2. Power consumption
The power of the AC system is generally within 100-300w, while that of the DC system is 50-220w. The DC system reduces power consumption by 30-50% in comparison with the AC system.
3. Uniformity of velocity
Uniformity of velocity refers to the uniformity of the face velocity of the FFU, for which high-level clean rooms bring forward especially high request, otherwise turbulence may be easily caused. It depends on the performance of the fan, the design of the filter and the air deflector, as well as the technological level. When testing this parameter, evenly select 6-12 points to test face velocity according to the size of the air outlet of FFU. The maximum value and the minimum value tested should be no more than 20% of the average value.
4. External static pressure
External static pressure (ESP) is also known as excess pressure. It concerns the service life of the FFU, especially the fan. In general, when the face velocity is 0.45m/s, the external static pressure should be no less than 90Pa.
5. Total static pressure
Total static pressure (TSP) is also called total pressure. It refers to the static pressure value provided (around 300Pa in AC FFU and 500-800Pa in DC FFU generally) when the FFU is at its maximum power and the velocity is zero. At a certain velocity, it can be calculated as: TSP = ESP (static pressure FFU provides to offset resistance in external duct and return air duct) + pressure loss of the filter (referring to the resistance value of the filter at that velocity).
6. Noise
Noise produced is generally between 42-56 dBA and more frequently measured when the face velocity of the FFU is 0.45m/s and the external static pressure is 100Pa. For FFU of the same size, the DC FFU is 1-2 decibels smaller than the AC one.
7. Vibration speed: Generally less than 1.0mm/s.
8. Basic dimensions of FFU: Customized
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