I. Material aspects In order to enhance the corrosion r […]
I. Material aspects
In order to enhance the corrosion resistance of all-metal roof fans, hot-dip galvanizing can be used as a whole machine, and aluminum alloy can also be used as rain caps. In order to deal with the aging problem of roof fans made of all fiberglass reinforced plastics, the method of increasing the thickness of fiberglass reinforced plastics is usually used to strengthen the treatment, which will certainly increase the production cost. Therefore, the material cost of roof fans made of all fiberglass reinforced plastics is higher than that of all metal roof fans. According to the calculation, the structural cost of two fans is about 30% lower; the most effective method is roof fans. The rainproof cap and check valve are made of FRP with the composite structure of FRP and FRP. The FRP has excellent rust resistance and is easy to shape. It can be made into various kinds of roof fans with different functions according to the air distribution and aesthetic requirements, so that the resistance of the fans can be minimized and the appearance of the fans can be more beautiful. The steel structure is used for the air ducts and the basic parts and the hot-dip galvanizing method is used to deal with them, which can ensure the strength and anticorrosion requirements of the structure. The fittings are welded directly to the air cylinder to simplify the production process.
II. Remaining Pressure
On the premise of guaranteeing the rated air volume of roof fans, it is necessary to ensure that the residual pressure greater than 50 Pa is provided for users to use.
III. Ending Adversity and Safety Aspects
Roof fans are equipped with backstop devices that can be safely closed when the machine stops operating. It can be equipped with loose-leaf dampers. There are three types of loose-leaf dampers: gravity type, electric type and manual type. They can be selected according to engineering requirements. In the design, if the roof fan is non-stop, it is necessary to fully consider the loss of hot air in the house and the loss of some heat caused by the invasion of cold air outside the house when calculating the heating heat load. In the cold area, it is necessary to consider its interference to the on-duty heating. A solid, firm and reliable safety net should be installed under the fan to ensure safety.
IV. Dew Prevention
In the design of roof fans, it is necessary to minimize the area of the air contact part inside and outside the house and reduce the amount of condensation.In the engineering design, considering the safety factor, the fitting position of the roof fan should avoid the direct upper part of the process equipment and the working position as far as possible, so as to reduce the interference of water dripping to the production.
V. Strong Wind Protection
In places where typhoons and strong winds occur frequently, it is necessary to choose roof fans with good typhoon resistance. The center of gravity of roof fans should be kept as low as possible. Streamlined structure can be used to reduce wind resistance. The wind resistance of umbrella-shaped rain caps is very unsatisfactory. It is better not to use this structure. The arrival of strong winds is attributed to abnormal conditions, and the design of rain caps can be considered according to downtime conditions. Roof fans used in typhoons and strong winds can also consider additional automatic ailerons, although in extremely windy weather conditions, the installation of automatic ailerons will reduce the influx of wind and rain. The aileron will be restored to its original position through the spring, and the aileron can also play the role of reducing the air drag and enhancing the air flow.
Roof fans should have good acoustic indicators. In order to control noise, the rotating speed of fans should not be greater than 1500 r/min, and 960 r/min fan is the best one. The noise of roof fans less than 5000 m3/h should be controlled below 50 dB, the noise above 5000 m3/h should be controlled below 60 dB, and the problem of high frequency noise should be prevented.
VII. Operational Maintenance
Roof fans are not suitable for installing air filters that need manual cleaning. If there is a requirement for cleanliness of air supply, other air treatment schemes should be used.