Eight principles and methods for fan selection

Summary:Fan selection is a very technical task, and there are many specific selection methods, such as: selection according to d...

Fan selection is a very technical task, and there are many specific selection methods, such as: selection according to dimensionless characteristic curve, selection according to logarithmic coordinate curve, selection according to dimensioned characteristic curve or performance table, Variant selection, selection according to pipe network resistance, etc. The fan selection methods are complicated, and some methods require certain professional knowledge.
For general business personnel, it is enough to be familiar with and master the two methods of dimensional performance table selection and fan-specific selection software. These two methods are simple and easy to operate. When selecting a fan, first of all, according to the two basic parameters of the required fan's air volume and total pressure, the fan's model and number can be determined through the fan's dimensional performance table (each fan product manual has relevant data). At this time, more than one product may meet the requirements; at this time, combined with the fan's purpose, process requirements, use occasions, etc., select the type, model, and structural material of the fan to meet the required working conditions, and strive to achieve the rated flow and rated pressure of the fan , As close as possible to the flow and pressure required by the process, so that the operating point of the fan is close to the high-efficiency area of ​​the fan characteristics when the fan is running.
The specific principles are as follows:
1) Before choosing a ventilator, you should understand the production and product quality of domestic ventilator, such as the types and specifications of the ventilator produced, the special purpose of various products, the development and promotion of new products, etc., and the environmental protection should be fully considered In order to choose the best use of fans.
2) According to the different physical and chemical properties of the gas conveyed by the ventilator, choose the ventilator for different purposes. If transporting explosive and flammable gas, choose explosion-proof ventilator; choose dust exhaust or pulverized coal ventilator when transporting dust or pulverized coal; choose anti-corrosion ventilator for transporting corrosive gas; work in high temperature environment or High-temperature ventilator should be selected for conveying high temperature gas.
3) When there are more than two types of fans to choose from on the fan selection performance chart, the one with higher efficiency and smaller number should be selected first: the one with larger adjustment range, of course, should be compared and weighed. Pros and cons are decided.
4) If the selected fan impeller diameter is much larger than that of the original fan, in order to use the original motor shaft, bearing and support, etc., the motor start time, the strength of the original fan components and the criticality of the shaft must be Rotation speed, etc. are calculated.
5) When choosing a centrifugal fan, when the motor power is less than or equal to 75KW, it is not necessary to install a valve only for starting. When a centrifugal boiler induced draft fan is selected for discharging high-temperature flue gas or air, a valve for starting should be installed to prevent overload during cold operation.
6) For the ventilation system with noise reduction requirements, the fan with high efficiency and low impeller circumferential speed should be selected first, and make it work at the highest efficiency point; should also be based on the noise and vibration transmission mode generated by the ventilation system, take corresponding measures Noise reduction and vibration reduction measures. Vibration reduction measures for fans and motors generally can be based on vibration reduction, such as spring shock absorbers or rubber shock absorbers.
7) When choosing a fan, try to avoid using the fan to work in parallel or in series. When it is unavoidable, ventilators of the same model and performance should be selected for joint work. When using series connection, there should be a certain pipeline connection between the first-stage fan and the second-stage fan.
8) The new fan selected should be considered to make full use of the original equipment, suitable for on-site production and installation, and safe operation.