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Some air volume control valve manufacturers advertise that their air valve pressure drop is very low, only 20-30 Pa, while some air valves have a pressure drop of 100 Pa or even 200 Pa or more. Low resistance can save fan power consumption, but is it better for the pressure drop of the air volume control valve to be lower< The resistance of an air valve at rated air volume (maximum design air volume) is usually the pressure drop when the air valve is fully open. This resistance value is meaningful for uating shut-off valves (such as closed valves, fire valves, check valves). However, what we are more concerned about when it comes to regulating valves is the working pressure difference they can achieve during control. Because whether it is a butterfly valve or a Venturi valve, the regulating performance of the air valve when fully open is not ideal. For a Venturi valve, the conical spring must be in a compressed state to function. For butterfly valves, only when the opening is between 10% and 80% can they have ideal adjustment characteristics. So, the opening of a normally functioning regulating valve is not in the fully open position. Usually, the working pressure difference of the control valve needs to be 150 Pa or greater< The ratio of the pressure drop during the operation of the regulating valve to the pressure drop in the branch it is located in is called the valve weight. The greater the valve weight, the better the control effect of the air valve on the airflow of the branch. On the contrary, if the pressure drop during the operation of the air valve is too small, its discourse power will be very small, and the adjustment of its valve plate will have little effect on the airflow of its branch. Only when the opening of the air valve is very small can the air volume be significantly changed, and if it continues to be turned down, the air volume drops sharply. This type of air valve exhibits obvious fast opening characteristics and belongs to the shut-off valve, which is not suitable for use as a control valve. Usually, a valve weight of less than 20% is detrimental to control. For the purification air conditioning system, HEPA filters are installed on the supply and exhaust air, with an initial resistance of about 100-250 Pa and a final resistance of 500 Pa. Therefore, the regulating valve needs sufficient working pressure difference to maintain good control& Nbsp; System coupling and anti interference of air valves. Usually, an air system has multiple parallel branches, and adjusting the opening of the air valve in one branch can interfere with the air volume control of other branches. When the resistance of a branch is too small, the disturbance to its air volume will be relatively large. For example, in the ventilation system of a chemical laboratory, there are several variable air volume exhaust cabinets. When the height of the sliding door of one exhaust cabinet changes, the corresponding exhaust valve needs to be adjusted, and the static pressure of the main exhaust duct will fluctuate accordingly, thereby affecting the exhaust volume of other exhaust cabinets. This phenomenon is called coupling. Coupling poses significant challenges to the control stability of the system. If the pressure drop of the air valve is too small, it is easy for the exhaust cabinets to interfere with each other, and in severe cases, it is difficult to ensure stable control of the exhaust air volume, which may even lead to the overflow of harmful substances. We refer to the ratio of the design pressure drop of a branch where the air valve is located to the pressure drop of the nearest branch to the fan as the balance degree. The lower the balance, the more likely it is for mutual interference between branches. There are two methods to improve the balance of the branch: one is to reduce the resistance of the main pipeline, and the other is to increase the resistance of the branch. Of course, the most effective method is the latter. That is to say, appropriately increasing the working pressure difference of the regulating valve can improve the balance of the branch and enhance the system's anti-interference ability& Nbsp; Conclusion adjustment