文章來源： 作者：羅茨機電 發布時間：2021-12-17 瀏覽次數：612
1、 The problem of water velocity
The pipeline flow rate shall be controlled below 16m / s. The faster the flow rate, the greater the resistance of the pipe network, which may lead to surge of the blower and increase the load of the rotary fan.
2、 Quality control of aeration rotary fan
In the domestic market, aerators have a wide variety, uneven quality and large price span. Due to the lack of relevant industry standards, workshop production mode is common. For example, for rubber aerators, the raw materials and ingredients used each time are different, resulting in unstable product quality. For example, if carbon black is added excessively, the rubber plate will harden and the resistance will increase; If the carbon black is not added enough and the rubber plate is too soft, it is easy to crack; There are even situations such as the use of recycled rubber. Therefore, the quality of non industrialized products is difficult to control. If the release amount of the aerator (the release amount is related to the water depth, pressure, flow rate and the quality of the rubber film of the aerator) cannot meet the process requirements, resulting in 70% release rate of the rotary blast flow, surge will occur and the fan pressure will be increased.
3、 Check valves are used differently
The hardness of the tension spring in the check valve of each manufacturer is different, and the local resistance loss is also different. Surge will also occur if the overall pipe resistance loss is greater than the outlet pressure of the rotary fan. When the rotary fan is shut down, it is necessary to close the inlet butterfly valve first and then the outlet butterfly valve, which can completely avoid the problem of water pouring, and there is no need to install the check valve at the outlet end. Increasing the check valve will increase the resistance loss and increase the equipment cost and operation cost.
4、 Changes in ambient temperature
According to the fan industry standard, the design temperature of the rotary fan is 20 ℃, and the outlet pressure will drop by about 20mmh2o every 1 ℃. For example, when the temperature is 38 ℃ in summer, the outlet pressure will drop by 360mmh2o. According to the climate characteristics of high temperature in most parts of China in summer, the company increases the design temperature at the inlet end of the rotary fan to 37 ℃, that is, under the phase coaxial power, the pressure at the outlet end is 340mmh2o higher than the national standard. According to the specific conditions of the use site, the influence of temperature change on the outlet pressure of the fan should also be considered when selecting the rotary fan. When the daily limit temperature of the fan is 37 ℃, the pressure at the inlet end shall be compensated according to 20mmh2o / 1 ℃.
5、 Changes in altitude
The design pressure of the rotary fan is 98kpa (150m above sea level, 1atm). Altitude HGT of the place where the fan is used; At 150m, appropriate compensation shall be made for the outlet pressure and inlet flow to ensure the normal operation of the equipment.
6、 Problems of grid connection:
When two or more rotary fans are connected to the grid, the increased resistance of grid connection must be considered. In the past, some users operated normally when using a single fan, but when two or more rotary fans were connected to the grid, the air flow was insufficient and the motor current could not go up, which was related to the overall gas supply capacity, whether the layout and release capacity of aerators were synchronized, and whether the configuration of gas transmission pipelines was reasonable.
7、 Parallel problem:
For the vent valve of sewage treatment fan, multiple fans are connected in parallel, and only one vent valve needs to be installed. When the blower is started, if the aeration head has not been opened, open the vent valve to vent some gas to make the blower reach a certain flow, and then close the vent valve after the pressure rise is stable. This can solve the surge problem caused by low flow.
8、 Pipe network resistance:
If the resistance of the pipe network behind the outlet of the blower is too high, when the inlet valve is opened, the motor current will exceed the rated current, because the part of the work pressure of the rotary fan exceeding the overall resistance of the pipe network will be converted into air flow. When the outlet valve is fully open, the pressure shown on the pressure gauge is not the work pressure of the fan, but the overall resistance of the pipe network. According to the performance curve, if the overall resistance decreases, the flow will increase accordingly and the current will increase. At this time, as long as the outlet valve is turned down, the artificial resistance is increased, and the pressure at the outlet end is expressed to the rated pressure, the current will be normal. The purpose of closing the outlet valve is to stop the overload flow. The rated flow of the rotary fan will not decrease, but increase the flow rate.
9、 Efficiency issues:
No matter what type of aeration rotary fan, its efficiency is relative. It is impossible to always maintain the highest efficiency in actual operation. Any increased resistance (such as valve, pipe elbow and aerator resistance) will reduce the efficiency. Therefore, maintaining high-efficiency operation of the rotary fan is inseparable from process design.