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In industrial production, the electric valve actuator, as an essential component of the automated control system, plays a significant role. It can precisely control the opening and closing of valves, ensuring the smooth operation of the entire production process. However, selecting the right electric valve actuator is not an easy task, and the most critical factor is to determine whether its rated output torque meets the actual requirements. This article will provide a detailed interpretation of this issue to help you make wise decisions when choosing an electric valve actuator.

Basic Factors for Valve Operating Torque

The torque required to overcome the resistance during the opening and closing of valves is the fundamental basis for selecting an electric actuator. The magnitude of the valve operating torque is influenced by a combination of factors, including the type, size, and working pressure of the valve.

Take the commonly used gate valve as an example. Its operating torque is closely related to the diameter of the valve stem, the medium pressure, and the friction force of the sealing surface. A specific formula, T=K×D×P (where T represents the operating torque, K is a coefficient, D is the diameter of the valve stem, and P is the medium pressure), can be used to estimate it more accurately. In addition to gate valves, other types of valves, such as ball valves and butterfly valves, also have their own corresponding torque calculation formulas. These formulas provide important references for us when selecting an electric actuator. Of course, we can also refer to the technical manuals or catalogs provided by valve manufacturers, which will list the approximate operating torque values for different models of valves, making it convenient for us to quickly obtain the required information.

The Importance of Considering a Safety Factor

After determining the basic operating torque of the valve, to ensure that the electric valve actuator can reliably operate the valve and prevent torque insufficiency due to unexpected factors, we must consider a certain safety factor. Under normal circumstances, the range of the safety factor is between 1.2 and 1.5. For example, if the calculated operating torque of the valve is 100 N・m, and the safety factor is taken as 1.3, then the rated output torque of the required electric actuator should be at least 100×1.3=130 N・m. The setting of this safety factor fully takes into account various uncertainties that may occur in actual working conditions, providing additional assurance for the stable operation of the valve.

The Impact of Special Working Conditions on Torque

The working conditions of the valve have a significant impact on its operating torque. In some special working conditions, such as high-temperature, low-temperature, or high-viscosity media environments, the operating torque of the valve will increase accordingly. For example, in high-temperature conditions, the sealing material of the valve will increase the friction force due to thermal expansion, thereby increasing the operating torque. In such cases, we need to appropriately increase the rated output torque value of the electric actuator to ensure that the valve can operate normally under special working conditions. In addition, if the valve is frequently opened and closed, it is also necessary to consider the torque reserve of the electric actuator to cope with possible torque attenuation during long-term operation. Frequent opening and closing actions will subject the electric actuator to a greater load, and the torque reserve can effectively extend the service life of the electric actuator and ensure its stability and reliability during long-term operation.

Referring to the Technical Parameters of Electric Actuator

After determining the required torque value, we need to refer to the technical parameter tables provided by electric actuator manufacturers. These tables list the rated output torque of different models of electric actuators in detail, providing a clear basis for us to select the appropriate electric actuator. When selecting, it is necessary to ensure that the rated output torque of the chosen electric actuator is greater than the torque value we calculated earlier (taking into account the safety factor and working conditions), so as to ensure that the valve can open and close normally and reliably. For example, if we determine that the required torque is 150 N・m after comprehensive consideration, then in the technical parameter table, we should choose an electric actuator model with a rated output torque greater than 150 N・m.

Torque Characteristics of Different Types of Valves

There are significant differences in the torque required to open and close different types of valves. For example, ball valves have relatively low torque, while gate valves, due to their sealing structure and greater friction force, usually require higher torque. When selecting an actuator, we need to fully understand the type of valve and refer to the torque data provided by the valve manufacturer in order to choose the appropriate electric actuator for different types of valves. The size of the valve and its pressure rating are also important factors affecting the torque. Generally speaking, the larger the valve size and the higher the pressure rating, the greater the resistance that needs to be overcome during opening and closing, and the greater the required torque. We can accurately calculate or estimate the torque demand of the valve in its working state by combining the valve's specification parameters with relevant calculation formulas or empirical data.

Other Factors Affecting Torque and Testing Methods

In addition to the factors mentioned above, there are other factors that can also affect the torque of the electric valve actuator. For example, if the medium controlled by the valve has high viscosity, density, or contains particulate impurities, it will increase the friction and resistance of the valve, thereby requiring a greater torque to drive it. In such cases, we need to consider the impact of the medium's characteristics on the torque and select an actuator with a larger torque accordingly. Changes in ambient temperature should also not be overlooked, as they may affect the material properties of the valve and actuator, thereby affecting the torque demand. For example, in low-temperature environments, materials may become brittle, increasing friction and requiring greater torque to open and close the valve.

During the actual installation and use process, we can also use some testing methods to further verify whether the torque of the electric actuator meets the requirements. First, after installing the valve and actuator, a no-load test can be conducted. That is, start the actuator when the valve is not under medium pressure, and observe whether the opening and closing process of the valve is smooth and whether the actuator can easily drive the valve to the fully open and fully closed positions. If the actuator experiences sticking, abnormal noise, or fails to fully open or close the valve even under no-load conditions, this indicates that the actuator's torque may be insufficient. Secondly, a loaded test can be performed when the valve is in its working state, that is, under medium pressure. By monitoring parameters such as the actuator's current, voltage, or power, we can determine whether the actuator is operating within its rated range. If the actuator has excessive current, significant voltage drop, or power exceeding the rated value during loading, and the valve's movement is not smooth, this may mean that the actuator's torque is not sufficient.

Case Analysis: Electric Ball Valves

In industrial automated control systems, electric ball valves, as a commonly used type of actuator, are widely applied in liquid and gas control systems. Many users are very concerned about the torque size of electric ball valves when selecting them, as torque directly relates to the control capability and application scope of electric ball valves.

The torque of an electric ball valve refers to the magnitude of the torque required by the electric ball valve when controlling the flow of the medium, that is, the magnitude of the torque required by the electric ball valve as an actuator to open or close in the fluid pipeline. The size of the torque not only directly affects the control capability of the electric ball valve but also has a close relationship with the service life and stability of the electric ball valve. The main factors affecting the size of the electric ball valve torque are as follows: the torque of the electric ball valve is directly proportional to the valve diameter, the larger the valve diameter, the greater the required torque; the higher the medium pressure, the greater the torque required to close the valve; the larger the sealing area between the valve stem and the valve seat, the greater the required torque; the friction force between the valve stem and the sealing surface will also affect the size of the torque.

The calculation method of the electric ball valve torque is relatively clear and can be calculated by the following formula: T=P×D÷2×μ. Here, T represents the required torque size, P is the medium pressure, D is the valve diameter, and μ is the friction coefficient. In practical applications, we need to fully consider the characteristics of the medium, working conditions, and the parameters of the entire pipeline system in order to select the appropriate model and specification of the electric ball valve. Under normal circumstances, suppliers will provide the torque data of the electric ball valve, and users can select the appropriate electric ball valve according to the actual situation.

When selecting an electric ball valve, it is necessary to fully consider the required torque size. First, a thorough understanding of the nature of the medium is required, including its fluid state, temperature, pressure, and other parameters; second, the working conditions of the pipeline system should be considered, including pipe diameter, pipeline length, medium flow velocity, and other factors; finally, the appropriate model and specification of the electric ball valve should be selected based on the actual control requirements and environmental conditions. The size of the electric ball valve torque directly affects its control capability and stability in practical applications, and selecting an electric ball valve with the appropriate torque is crucial for the normal operation of the system.

Conclusion

In summary, determining whether the rated output torque of an electric valve actuator meets the requirements is a complex and important process when selecting an electric valve actuator. We need to take into account a comprehensive range of factors, including the basic factors for valve operating torque, safety factors, the impact of special working conditions, the torque characteristics of different types of valves, and other related factors. Only through scientific calculations, rational selection, and necessary testing and verification can we ensure that the selected electric valve actuator can operate stably and reliably in actual working conditions, providing strong support for the smooth progress of industrial production. We hope that the introduction in this article can provide you with valuable references and guidance when selecting an electric valve actuator.