Valve electric device (referred to as electric actuator, the same below) is a special transmission device used to drive the valve to open and close. It is composed of a special motor, worm gear, stroke, and torque detection mechanism, and control part. The device has a large starting torque and accurate valve stroke control. It is widely used in valves in petroleum, chemical, hydropower, metallurgy, shipbuilding, light industry, and food industries. Different industries and different working conditions have different requirements for valve electric actuators.
The commonly used valve electric actuators in our factory are imported with original packaging, imported technology or joint ventures, and produced by wholly-owned and assembled factories established by China Electric Actuator Company and foreign electric actuator manufacturers in my country. Valve electric actuators are generally classified according to structure type, working mode, rotation mode and working environment.
2.1 Structure type
The structure types of electric actuators can be divided into two types: one-piece type and split type. The integrated electric actuator is that all the control devices that control the operation of the electric actuator are installed inside the electric actuator and are integrated with the electric actuator. The integrated electric actuator is divided into ordinary type and intelligent type. Split type electric actuator is that all the control devices that control the operation of the electric actuator are installed in a separate electric control cabinet. Currently, there are ROTOCK, AUMA, EMG, etc. that can provide split-type electric actuators.
2.2 Working method
The working model of electric actuator is divided into switch type and regulating type. The switch type mainly refers to the motor start times of the electric actuator generally <600 times/min. The on-off electric actuator is only suitable for opening or closing the valve at one time. Regulating type mainly refers to the more frequent commutation of the electric actuator, and the number of motor starts generally reaches 1200 min. Regulating electric actuators can accept 4-20mA analog signals and feedback valve position 4-20mA analog signals to meet the needs of closed-loop control.
2.3 Rotation method
The rotation mode of the electric actuator is divided into multi-turn and partial-turn. Multi-turn transformation mainly means that the electric actuator needs to rotate multiple times to open or close the valve. There must be a second transmission mechanism between this type of electric actuator and the valve. Partial rotation mainly refers to the electric actuator rotating 90° to open or close the valve, and this type of electric actuator is directly connected to the valve.
2.4 Working environment
The working environment of electric actuators is divided into flameproof type and ordinary type. Explosion-proof type means that in a flammable and explosive environment, electric actuators are required to have explosion-proof functions. Ordinary type refers to any environment except inflammable and explosive environment.
3 performance characteristics
The performance characteristics of some electric actuators in various countries are shown in Table 1.
Table 1 Part of the performance characteristics of electric actuators
|Part of electric|
|Performance and characteristics|
|1||ZB/ZC||①Ambient temperature -20~40℃.|
②Outdoor type protection grade IP55 can reach IP67 insulation grade F when special requirements are required.
③Short-time work system, time quota is 10min
④There are integrated and split types. The integrated type can output 4-20mA analog valve position signal
|2||DZ(W)||①Ambient temperature -20-60℃.|
②Protection grade IP55, insulation grade can reach F grade, rated continuous working time 10min.
③There are one-piece and split-type. The integrated type can output 4-20mA analog valve position signal.
|3||D.DM||①Ambient temperature -25~70℃.|
②The protection grade is IP68, the insulation grade can reach F grade, and the time limit is 10min.
③Intelligent type made in China, with remote setting function, display function and alarm function, 4-20mA valve position feedback.
|4||M||① Made in China, it is a smart integrated type, and the protection level can reach IP65, IP67, and IP68.|
|①Ambient temperature -30~70℃.|
②The protection level can reach IP68 and the rated continuous working time is 15min.
③There are integrated type and split type, integrated type can output 4-20mA analog valve position signal (option).
|①Ambient temperature -30~70℃.|
②The protection level can reach IP68, and the rated continuous working time is 15min.
|6||SMC||①Ambient temperature -20~55℃.|
②The protection level is IP67, and it can reach IP68 when needed, and the rated continuous working time is 10min.
③Integral switch type and adjustable type can be provided, which can output 4-20mA analog valve position signal (option).
④A smart integrated type can be provided.
|7||2SA 30||①Ambient temperature -20~80℃.|
②The introduction of Siemens technology, the protection level is IP67, and the rated continuous working time is 15min.
③Can provide overall control type, can output 4~20mA analog valve position signal
④The adjustment function can also be realized with the power intelligent module
|2SA 35||①Ambient temperature -20~60℃.|
②The protection level is IP67.
③ Equipped with LU intelligent power module, it is intelligent.
|8||2SA 80B||①Ambient temperature -25~70℃.|
②The protection level is IP68.
③Intelligent integrated type, with frequency conversion speed regulation function.
④Can receive and output 4-20mA analog signals.
|9||SND-ZC||①Ambient temperature -20~60℃, optional temperature -40~70℃.|
②The protection level reaches IP68. The rated continuous working time is 15min. Class F insulation.
③Intelligent integrated type.
|①Ambient temperature -30~70℃.|
②Protection grade IP68. Class F insulation.
③The continuous working time is not more than 15nin.
|11||SR 、SJ seriesE||①Intelligent integrated type.|
|①Ambient temperature -30~70℃, the highest can reach 150℃.|
②The protection grade is IP67, and the rated continuous working time is 15min. Only the integral control type is provided.
③ Economical and professional models are available. The economical type is mainly used for switch control and simple adjustment control and can output 4-20mA analog valve position signal. Professional type is mainly used for regulating control with more complicated control functions. It can receive and feedback 420mA analog signal.
④Intelligent integrated type.
|13||AUMAC||①Ambient temperature -25~70℃, high-temperature type can reach 0~120С.|
②Protection level is IP67, up to IP68 when needed, short-time working system, rated continuous working time 15min.
③It is divided into switch type and regulating type, among which switch type is divided into integrated control unit (integral type) and non-controller unit.
④ Output 4-20mA analog valve position signal (option).
|①Ambient temperature -30~70℃.|
②Protection level P68, continuous working time is less than 15min.
③Intelligent integrated type can output 4-20mA analog valve position signal.
②Continuous work, 1200 times/h.
③Receive and output 4-20mA analog valve position signal.
|15||ROTORK||①Ambient temperature -30~70℃.|
②The protection level reaches IP68, and the continuous working time is less than 15min.
③Two types, one-piece and split type.
|16||EMG||①Ambient temperature -25~ 70℃.|
②It is divided into three series, namely Standand series, Matic C (DMC) series, and i-Matic (DM) series. Standard series are split type, Matic C series, and i-Matic series. All-in-one.
③Matic C series can output 4-20mA analog valve position signal (option). In addition, the DMC series is also called intelligent all-in-one, and a simple display device can be added to the basic DMC model.
④The i-Matic series is an intelligent integrated type.
|A integrated type, suitable for valve position switch adjustment (referring to non-continuous or infrequent adjustment).|
B 15min short-time duty system and adjustable 1200 times/h two working modes.
C French Schneider technology.
D American technology.
E American technology.
F power supply frequency range 47~63Hz, variable frequency speed regulation electric actuator, output shaft speed 7 gears, which can be set by the user. When selecting the type, please pay attention to the torque and speed corresponding to the default motor power of the electric actuator.
G AC01. 1 is an intelligent integrated type, and AM 01.1 is an ordinary integrated type.
H has only one-piece structure.
I The corresponding model of the maximum torque of this series is IQM 35.
J 40A and above (including 40A) are produced in the UK, and 35A (including 35A) and below are produced in Malaysia.
Table 2 Meaning of motor protection grade code
|1ST DIGIT||INDICATE||2ST DIGIT||INDICATE|
|0||No protection||0||No protection|
|1||Protect objects above 50mm||1||Protection against vertical falling water droplets|
|2||Protect objects above 12mm||2||Protection against water spray at 15° from the vertical|
|3||Protect objects above 2.5mm||3||Protection against water spray at 60° from the vertical|
|4||Protect objects above 1mm||4||Protection against water sprays from all directions, allowing limited immersion|
|5||Protects against dust and allows limited immersion||5||Protection against low-pressure water jets in all directions, allowing limited immersion|
|6||Complete protection from dust||6||Strong protection against water spray, allowing limited immersion|
|7||Protection from 15cm~1m deep immersion|
|8||Protection against long-term immersion under pressure|
4. How to select the electric actuator
The selected electric actuator must meet the working conditions, valve switching torque, time (speed), and control requirements.
4.1 Ambient temperature
The motor of the electric actuator is enclosed inside the electric actuator, and its heat dissipation performance is poor. If the electric actuator is used outside the adapted ambient temperature range, it will directly affect the insulation performance, output torque, and service life of the electric actuator. Therefore, be sure to pay attention to the applicable temperature range of the electric actuator in a high-temperature environment.
4.2 Degree of protection
The protection level of an electric actuator is a measure of its degree of protection against dust and water. It is represented by IP + two digits (Table 2). The first digit indicates the dustproof level, and the second digit indicates the waterproof level. Choose IP54 or IP55 for the indoor general environment, and choose IP55 or IP65 for the outdoor general environment. If the dust is large and the dust particles are small in the working condition, there may be water splashing on the electric actuator from all directions, and a higher protection level should be selected. IP65 or IP67. If the electric actuator may be submerged in water, a higher degree of protection such as P67 or IP68 should be selected. The IP68 protection level means that it can be submerged for 72 hours without water entering 3m underwater.
4.3 Control form
The control mode mainly refers to whether the electric actuator is integrated or split. According to the use of electric actuators in some projects in recent years, the intelligent integrated type is generally used. The intelligent electric actuator has LCD panel display and setting function (no open cover debugging), electronic position sensor and torque sensor, position feedback (4-20mA analog signal), automatic phase sequence correction, instantaneous reverse protection, locked-rotor protection, Data recording, automatic diagnosis, and support field bus communication (optional) and other functions. Different working conditions have different requirements for the control form of electric actuators. From the perspective of price, in normal working conditions or occasions where the requirements for electric actuators are not high, intelligent integrated electric actuators are generally not used. In high temperature or cold conditions, because the performance of the control circuit board inside the integrated electric actuator is greatly affected by temperature, the intelligent integrated type is generally not used.
The electric actuator torque is one of the important parameters. The maximum torque required during the valve opening and closing process must be calculated before the selection, and then the required output torque of the electric actuator must be calculated. The torque selection of the valve electric actuator should be based on the rated output torque provided by the electric actuator manufacturer. When calculating and rechecking the torque of the valve, the torque margin should not be too large. Because the electric actuator has a torque protection function, if the valve’s switching torque margin is too large, the selected electric actuator output torque will be selected to be larger. When the valve encounters a jam during the opening and closing process, the torque of the electric actuator Before the protection switch is activated, the weak part of the valve may be damaged.
The output speed of the electric actuator affects the opening and closing time of the valve. Some operating conditions stipulate the valve opening and closing time, and the output speed of the electric actuator must be selected according to the requirements. Some working conditions do not require the valve switching time, but the electric actuator motors are all short-time working systems, and their continuous operation time does not exceed 10 minutes, and some do not exceed 15 minutes. Therefore, even if the working conditions do not require time, the valve opening and closing time must not exceed the maximum time required for continuous operation of the electric actuator. The output speed of an electric actuator is related to the output torque. For the same motor power, the faster the output speed, the smaller the output torque. Therefore, when selecting an electric actuator, the torque and speed must match.
4.6 Control requirements
Control requirements are the requirements of the user monitoring system for the valve electric actuator, such as whether the electric actuator is a regulating type or a switch type. The motors of general regulating electric actuators can be started frequently, up to 1200 times/h, can receive and feedback 4-20mA analog signals, closed-loop control, and automatically adjust the valve opening to meet the requirements of the working conditions. The on-off electric actuator only controls the opening or closing of the valve. The motor cannot be started frequently. The continuous working time of the motor is generally 10min and some 15min. In addition, there are other requirements, such as feedback to the valve status of the central control room (fully open, fully closed) The number, type and capacity of the contact points) and the control method of the electric actuator.
In order to ensure the reliability and durability of the valve drive device, the valve electric actuator should be selected according to the installation position, use requirements, pressure, caliber, cost performance and protection level.
Author: Wu Youlin