Valve electric and pneumatic actuators Introduction Lightweight valve pneumatic actuators

Valve electric and pneumatic actuators Introduction Lightweight valve pneumatic actuators

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The electric actuator is generally composed of motor, reducer, hand operating mechanism, mechanical position indicating mechanism and other parts. Compared with other valve drive device, electric drive device has the characteristics of power source, rapid operation, convenient, and easy to meet various control requirements. Therefore, in the valve actuation device, the electric device is dominant. Make the convex table on the rotating column and the direction of the arrows on both sides basically consistent until the rotation back to the top shaft reset. Then give the open and close signal, see whether the valve meets the requirements…
Valve actuating mechanism
Introduction of electric and pneumatic actuators
1.1 Pneumatic actuator
Valve pneumatic drive device is safe, reliable, low cost, easy to use and maintenance, is a branch of the valve drive mechanism. Pneumatic devices are widely used in explosion-proof applications. The valve pneumatic drive device uses the air source working pressure is low, the structure size is not large, the total thrust of the valve pneumatic drive device is not very large.
Pneumatic thin film actuator
Single spring, positive action
Multiple springs, reaction
Cylinder horizontal actuator
Double acting (no spring)
Single action (spring return)
Electric actuator
The electric actuator is generally composed of motor, reducer, hand operating mechanism, mechanical position indicating mechanism and other parts. Compared with other valve drive device, electric drive device has the characteristics of power source, rapid operation, convenient, and easy to meet various control requirements. Therefore, in the valve actuation device, the electric device is dominant.
2. Commissioning of actuator
2.1 Commissioning of electric head
When debugging the electric actuator, use the hand wheel to open the valve to the middle position, and then give the open or close signal, to see whether the valve is moving in the right direction, if the opposite, the motor is reversed, only need to exchange the two phases of the motor three-phase power supply. The torque switch has been set after leaving the factory, and generally does not need to be adjusted. If adjustment is needed, find the scale value on the torque switch in the instruction manual to adjust. Adjusted score of stroke switches close to and open, close to the adjustment, manual “seated”, the valve shaft with a screwdriver down. And rotate 90 ° can get stuck, press close to the arrow spin off to adjusting nut, until close to rotate the column action, rotate the column on the convex platform is consistent with the direction arrow on the basic of (non action status, convex direction and vertical direction arrow). When adjusting the opening direction, manually turn the valve to “fully open”, press the top shaft with the driver, and rotate 90° to get stuck, press the open arrow to rotate the open adjustment nut, until the open rotating column action, so that the convex head on the rotating column and the direction of the arrows on both sides are basically the same, rotate the top shaft to reset. Then give the open, close signal, see whether the valve meets the requirements.
2.2 Pneumatic head debugging
Pneumatic actuator debugging, mainly on the positioner debugging. First put to close the valve position, in order to guarantee the valve closed tight, turn coupling nut to screw on the valve stem so far, the valve core and valve seat must contact closely, the adjusting stem stroke scale to zero, and then turn on the air, the air supply pressure to the required pressure with pressure reducing valve, and then use 4 ma current signal generator to the locator input, Adjust the zero point adjusting handwheel on the positioner until the valve just starts to operate, then input 20mA current, adjust the zero point adjusting handwheel and range adjusting device according to the stroke scale to make the stem stroke fully open, and then repeat the input steps of 4mA and 20mA, until the valve meets the requirements of 4mA fully closed and 20mA fully open. In order to ensure that the valve is closed at 4mA, 4.10~4.15mA current can be input as the signal of full closure during debugging, so that 4mA current can definitely close the valve in the actual working state.
All lightweight pneumatic multi-spring film actuators are composed of diaphragm, compression spring, tray, push rod, bracket, bushing film cover and other main parts. The diaphragm is of deep basin shape, coated with butadiene rubber to enhance the strength of the polyester fabric and ensure tightness, and can be used at a temperature of 30~85℃. The compression spring uses a combination of multiple springs instead of a large spring in the conventional structure, thus reducing the height. The number of springs can be divided into 4, 6, or 8. The guide surface of the push rod is finished and surface treated…
Light pneumatic actuators are also known as fine small pneumatic actuators.
This product has the characteristics of light weight, small height, compact structure, easy installation, reliable action, large output force, energy saving and so on. When INSTALLED ON the valve, compared with the traditional pneumatic control valve, the height is reduced by 30%, the weight is reduced by 30%, but the flow capacity is increased by 30%, and the adjustable range is extended to 50:1. Its structure and working principle are shown in Figure 2-20
FIG. 2-20 light duty pneumatic actuator
A) direct stroke (reaction type) b) angular stroke (positive action type)
Light pneumatic multi-spring film actuator can be divided into positive acting type (Figure 2-20B) and negative acting type (Figure 2-20A) according to the mode of action. After the composition of the regulating valve, according to the opening and closing mode is divided into two types of gas off and gas open.
Figure 2-20A is a straight stroke pneumatic actuator. It accepts the air pressure signal from the regulating instrument, or the electric signal is converted into the air pressure through the electrical converter, input to the air chamber, acting on the film after the thrust, so that the output rod movement. This thrust compresses the spring at the same time, until it is balanced with the spring reaction force, so that the output rod reaches the predetermined position.
Figure 2-20B is an angular stroke pneumatic actuator. Its working principle is: the signal pressure or electrical signal from the regulating instrument, through the electrical conversion into air pressure input to the air chamber, acting on the film to produce thrust, so that the push rod movement, and then by a linear rotation mechanism converted into torque, output angular displacement. When the output rod reaches the predetermined position, the output of the angular stroke is also certain. When the actuator and the positioner are combined, the rotation Angle of the output shaft is fed back to the positioner, which can achieve the purpose of accurate positioning of the rotation Angle.
All lightweight pneumatic multi-spring film actuators are composed of diaphragm, compression spring, tray, push rod, bracket, bushing film cover and other main parts. The diaphragm is of deep basin shape, coated with butadiene rubber to enhance the strength of the polyester fabric and ensure tightness, and can be used at a temperature of 30~85℃. The compression spring uses a combination of multiple springs instead of a large spring in the conventional structure, thus reducing the height. The number of springs can be divided into 4, 6, or 8. The guide surface of the push rod is finished and surface treated to improve the hardness, reduce the surface roughness, reduce the return error and increase the sealing effect. Reaction type actuator generally adopts 0 shape sealing ring and push rod, shaft sleeve, simple structure, reliable sealing, design without compression spring adjustment mechanism, can be assembled at a time, do not need to adjust. The connection of the push rod and the valve stem can be generally used to open the seam nut, easy to disassemble and assemble.
In light duty pneumatic actuators, double spring pneumatic actuators as shown in Figure 2-21 can also be used. It puts the little spring inside the big spring. The two springs work at the same height but have different stiffness, but the total stiffness is the sum of the stiffness of the two springs. In this way, the total height of the whole actuator can be reduced, so that the structure is more compact.
FIG. 2-21 double spring pneumatic actuator
A) Air open b) air closed
Since LIGHTWEIGHT pneumatic ACTUATORS are CONSTRUCTED WITH multiple SPRINGS HOUSED in THIN FILM CHAMBERS, THE BULKY SUPPORT OF CONVENTIONAL STRUCTURES CAN be REPLACED BY two steel CYLINDERS. This structure is lighter in weight and reliable enough in strength; The disadvantage is that the adjustment stroke must be removed and adjusted before installing the diaphragm chamber upper cover.
If the spring is required to be used for high pressure or large caliber, require a large force, and want a compact structure, you can use a double-layer membrane head structure, see Figure 2-22. Although the structure is more complex, it is lightweight. Its two membrane heads have two diaphragm working together to accept the same air pressure signal, the resultant force to push the stem action, the resulting force can reach 3000-60000N.


Post time: Sep-27-2022

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