Description
Product introduction:
Shang Yi Electric Actuator/ shangyi mov valve/SHANGYI ROTORK actuator valve
The broadest definition of an actuator is a drive that provides linear or rotational motion that uses some kind of drive energy and works with some kind of control signal. The actuator uses liquid, gas, electricity or other energy sources and converts it into a drive through a motor, cylinder or other device. The basic types are partial rotation (Part-Turn), multi-turn (Multi-Turn) and linear (Linear).
The basic actuator is used to drive the valve to a fully open or fully closed position. The actuator used to control the valve is able to accurately move the valve to any position. The design of the actuator far exceeds the simple switching function. They include position sensing devices, asynchronous sensing devices, electrode protection devices, logic control devices, digital communication modules and PID control modules, all of which are mounted in one volume. Inside the enclosure.
Because more and more factories use automatic control, manual operation is replaced by mechanical or automation equipment, people are required to control the interface between the system and the mechanical movement of the valve, and the actuator is required to enhance work safety and environmental protection. performance. In some dangerous situations, automated actuators can reduce the risk of personal injury.
Some special valves require emergency opening or closing under special conditions, and the valve actuator prevents further spread of the hazard while minimizing plant losses. For some high pressure and large diameter valves, the required actuator output current is very large. In this case, the actuator must be mechanically efficient and use a high output motor in order to operate the large diameter valve stably. For some small valve valves, small and small electric valves are also used. Some common models have the advantages of light weight, exquisite structure and complete functions.
Advantages:
The main advantages of the electric actuator are the high stability and the constant thrust that the user can apply. The maximum actuator can generate up to 225,000 kgf of thrust. Only the hydraulic actuator can achieve such a large thrust, but the hydraulic actuator is more expensive than the electric actuator. A lot higher.
The anti-deviation ability of the electric actuator is very good. The thrust or torque of the output is basically constant, which can overcome the imbalance force of the medium and achieve accurate control of the process parameters. Therefore, the control accuracy is better than that of the pneumatic actuator. high. If a servo amplifier is used, it is easy to achieve the exchange of positive and negative effects, and it is also easy to set the state of the off-signal valve position (hold/full-open/full-off), and when it is faulty, it must stay in place, this is Pneumatic actuators do not work, pneumatic actuators must be secured by means of a combined protection system [1].
There are two types of electric actuators, which are generally divided into a Part-Turn Electric Valve Actuator and a Multi-Turn Electric Valve Actuator. The former mainly controls valves that require partial rotation, for example: Ball valves, butterfly valves, etc., the latter requires multiple turns of the valve, such as gate valves.
Electric-powered multi-turn actuators are one of the most common and reliable actuator types. Use a single-phase or three-phase motor to drive the gear or worm gear and finally drive the stem nut. The stem nut moves the stem to open or close the valve. Multi-turn electric actuators can quickly drive large size valves. In order to protect the valve from damage, the limit switch installed at the end of the valve stroke will cut off the motor power. At the same time, when the safety torque is exceeded, the torque sensor will also cut off the motor power. The position switch is used to indicate the valve's switching state. The handwheel mechanism that mounts the clutch device can manually operate the valve in the event of a power failure.
The main advantage of this type of actuator is that all components are housed in a single housing that integrates all basic and advanced functions in this waterproof, dust-proof, explosion-proof enclosure. The main disadvantage is that when the power fails, the valve can only remain in place, and only with the backup power system, the valve can achieve a fail-safe position (fault open or fault closed).
This type of actuator is similar to an electric multi-turn actuator. The main difference is that the final output of the actuator is a 1/4 turn 90 degree motion. The new generation of electric single-turn actuators combines the complex functions of most multi-turn actuators, such as parameter setting and diagnostics using a non-entry user-friendly operator interface. The single-turn actuators are compact and can be mounted on small-sized valves, typically with output torques up to 800 kg. In addition, the required power supply is small and they can be fitted with batteries for fail-safe operation.
Driving energy:
When selecting the actuator for the valve, it is necessary to know the type of valve so that the correct actuator type can be selected. Some valves require multi-turn drive, some require single-turn drive, and some require reciprocating drive, which affects the choice of actuator type. Generally, a multi-turn pneumatic actuator is more expensive than an electric multi-turn actuator, but a reciprocating straight-stroke pneumatic actuator is less expensive than an electric multi-turn actuator.
Valve type:
When selecting the actuator for the valve, it is necessary to know the type of valve so that the correct actuator type can be selected. Some valves require multi-turn drive, some require single-turn drive, and some require reciprocating drive, which affects the choice of actuator type. Generally, a multi-turn pneumatic actuator is more expensive than an electric multi-turn actuator, but a reciprocating straight-stroke pneumatic actuator is less expensive than an electric multi-turn actuator.
Torque size:
For 90 degree swing valves such as: ball valves, disc valves, plug valves, it is best to obtain the corresponding valve torque by the valve manufacturer. Most valve manufacturers are testing the valve to operate the torque required at the rated pressure. Torque is provided to the customer.
For multi-turn valves, these valves can be divided into: reciprocating (lifting) motion - valve stem does not rotate, reciprocating motion - stem rotation, non-reciprocating - stem rotation, valve stem must be measured The diameter, stem connection thread size has been determined by the actuator specifications.
Executive agency selection:
Once the type of actuator and the required drive torque for the valve are determined, it can be selected using the data sheet or selection software provided by the actuator manufacturer. Sometimes the speed and frequency of valve operation need to be considered.
The fluid-driven actuator adjusts the stroke speed, but the electric actuator of the three-phase power supply has a fixed travel time.
Some small-size DC electric single-turn actuators adjust the stroke speed.
Institutional principle:
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Component:
The angular travel adjustment electric actuator consists of two parts: the power unit and the position locator (PM-2 control board). The power components are mainly composed of electric motor, reducer, torque stroke limiter, switch control box, hand wheel and mechanical limit device and position transmitter. The functions of each part are as follows:
1, the motor
The motor is a special single-phase or three-phase AC asynchronous motor with high starting torque, low starting current and small moment of inertia, so it has better servo characteristics. A thermal switch (shown in Figure 3) is installed inside the motor stator for overheat protection. When the motor is abnormally overheated (internal temperature exceeds 130 °C), the switch will open the circuit of the control motor to protect the motor and actuator. When the motor is cooled, the switch is turned back on and the circuit resumes operation. In order to overcome the inertia idling, the motor control circuit of the regulating electric actuator has an electric braking function.
2, reducer
The angular travel actuator adopts planetary deceleration plus worm gear transmission mechanism, which has high mechanical efficiency and mechanical self-locking characteristics. The speed reducer of the linear actuator consists of a multi-turn actuator gearbox with a screw nut transmission.
3, torque stroke limiter
It is a standard unit set in the reducer, which consists of an over-torque protection mechanism, a stroke control mechanism (electrical limit), a position sensor and a terminal block.
4, over torque protection mechanism
The deflection of the inner planetary gear generated when the torque is transmitted is inserted into the swinging rod of the outer ring of the gear. The two ends of the swinging rod are respectively equipped with a force-compressing elastic force as a sensing element for positive and negative moments, when the output torque When the set limit torque is exceeded, the deflection of the internal gear causes the swing lever to touch the power torch switch, and the control circuit is cut off to stop the motor. The adjustment torch limits the amount of compression of the bomb to adjust the limit value of the torch. This protection has a memory function, and the electrical equipment corresponding to the wiring diagram is the torque switch LEF, LEO. After the protection action, after the mechanical torque fault is eliminated, the actuator can be restored (ie, the memory is released) to resume normal operation after the power is turned off or the signal is reversed.
(1) Stroke control mechanism: consists of a cam set and a micro switch. The cam group is coupled to the transmission shaft of the reducer by gear reduction, and the stroke of the actuator can be limited by adjusting the position of the cam plate respectively acting on the positive and negative microswitches (ie, the travel limit switch) (stroke switch FCO) , FCF). The range of the electrical limit has been adjusted at the factory. Under normal circumstances, please do not adjust it to avoid damage to the mechanism.
(2) Position sensor: a high-precision, long-life conductive plastic potentiometer is used as the position sensing element, which is coaxially connected with the cam group. The integral proportional adjustment type electric actuator position indication signal is the potentiometer with the output shaft. The resistance value of the stroke change is sent to the comparison amplifier circuit of the PM-2 control board, and it sends a 4-20 mA DC current signal for indication.
5, switch control box
A PM electronic position locator is installed in the switch control box.
6, hand wheel
In the fault state and during commissioning, manual local operation can be achieved by turning the handwheel.
7, mechanical limit device
Mainly used for faults and to prevent extreme position protection during manual operation. The mechanical limit of the angular stroke electric actuator adopts the built-in fan-shaped turbine limit structure, which is small in size and reliable in position. The mechanical limit of the linear actuator is built-in block type limit structure, which can effectively protect the seat. , valve stem, valve core.
The position locator is essentially a multi-function high-power amplifier board that compares and amplifies the control signal with the position feedback signal to control the opening and closing direction of the motor, and is connected to the power component of the actuator to control the actuator according to the system. State work. The position locator is mainly composed of circuits such as comparison, logic protection, amplification drive and power amplification. The power amplifying part of the position locator for controlling the single-phase motor is mainly composed of a solid-state relay (contactless electronic switch) that triggers the zero-crossing of the photoelectric fault. The main part is schematically shown in Figure 4. It should be noted that the "manual-automatic" transfer switch functions to cooperate with the manual adjustment potentiometer P1 in the absence of an external signal to observe or debug the actuator. After use, it must be dialed back to "automatic", so as not to affect the automatic control of the investment system.
Switch control:
Automatic control valve
The biggest advantage of the automatic control valve is that it can operate the valve from a distance, which means that the operator can sit in the control room to control the production process without having to go to the site to manually open and close the valve. People only need to lay some pipelines to connect the control room and the actuator. The driving energy directly stimulates the electric or pneumatic actuator through the pipeline. The 4-20 mA signal is usually used to feedback the position of the valve.
Continuous control:
If the actuator is required to control the parameters of the process system such as level, flow or pressure, this is the work that requires the actuator to operate frequently. The 4-20 mA signal can be used as the control signal. However, this signal may be as frequent as the process. change. If an actuator with very high frequency action is required, only special actuators that can start and stop frequently can be selected. When multiple actuators are required in one process, the various actuators can be connected by using a digital communication system, which greatly reduces installation costs. Digital communication loops can deliver commands and collect information quickly and efficiently. There are a variety of communication methods such as: FOUNDATIONFIELDBUS, PROFIBUS, DEVICENET, HART and PAKSCAN designed for valve actuators. Digital communication systems not only reduce investment costs, they also collect a large amount of valve information that is valuable for predictive maintenance procedures for valves.
Predictive maintenance:
The operator can use the built-in data memory to record the data measured by the torque sensing device each time the valve is operated. This data can be used to monitor the status of the valve operation, to indicate whether the valve needs repair, or to use this data to diagnose the valve.
The following data can be diagnosed for the valve:
1. Valve seal or packing friction
2. Friction torque of valve stem and valve bearing
3. Seat friction
4. Friction in valve operation
5. The dynamic force of the spool
6. Stem thread friction
7. Stem position
Most of the above data exists in all types of valves, but the focus is different. For example, for butterfly valves, the friction in the operation of the valve is negligible, but the value of the force for the plug valve is large. Different valves have different torque running curves. For example, for wedge gates, the opening and closing torques are very large. In other strokes, only the friction of the packing and the friction of the threads are used. When closed, the hydrostatic pressure acts on the gate. The seat friction, the final wedge effect causes the torque to increase rapidly until it is closed. Therefore, according to the change of the torque curve, it is possible to predict the failure that will occur, and can provide valuable information for predictive maintenance.
Precautions:
Take the integral proportional adjustment type of the electric actuator as an example.
Before power-on, visual inspection and insulation inspection must be carried out. The insulation of the power circuit (arc circuit) and the signal contact to the outer casing should be no less than 20MΩ with a 500V megger: signal input, output circuit and their power The insulation between the circuits, except for special requirements, should not be lower than l0mΩ before being energized. After power-on, check whether the transformer, motor and electronic circuit components are overheated. If there is any noise in the rotating parts, immediately find the abnormality and cut off the power supply to find out the cause. Do not easily solder the components until the cause is identified. When replacing electronic components, prevent excessive temperature and damage components. When replacing the FET and the integrated circuit, be sure to ground the soldering iron or use the residual heat to solder out. When disassembling parts, components or welding leads, mark them and mark them accordingly. The output circuit of the device to be inspected should be avoided as far as possible to avoid power failure when the device under test has an input signal. The repaired equipment must be verified. For the dry motor, check the insulation resistance between the coil and the outer casing and the coil, measure the DC coil of the coil, clean the bearing and add high-quality lubricating oil, check the rotor, stator coil and brake assembly; for the reducer, disassemble and clean the parts, check In the case of the planetary gear portion, check the condition of the helical gear portion, check the meshing condition of the turbine worm or the screw nut, and finally assemble, adjust and lengthen the effect 铿 base grease. For the position sensor part to be visually inspected, check the coaxial connection between the potentiometer and the stroke control mechanism, check the basic condition of the potentiometer, and check the connection between the potentiometer and the amplifier board.
Take the production safety in various emergencies as an example.
In large pipe network systems, the valve is widely distributed or far away. In order to ensure production safety under various emergencies, the valve needs to manually close the door after the local power failure, and can also display and remotely in the field. The function of monitoring the opening degree of the valve requires the electric actuator to have a self-contained battery low-power manual mode, and enters the manual mode in the case of the local power failure, and the self-provided battery can display the valve opening not only locally, but also The ability to provide remote valve opening display for remote monitoring.
Low-power manual mode, involving low-power LCD technology, low-power CPU technology, low-power data acquisition, calculation, processing and transmission and low-power battery-powered technology, the key is the valve opening sensor needs to be selected Absolute multi-turn encoder for full stroke. In fact, in the manual mode, due to the low response response requirements, the MCU (microprocessor) can adopt a low-power gap mode, that is, a half-sleep mode, which ensures that the power consumption is extremely low, and the battery is self-contained. Capacity can be used for a long time.
When the low-power half-sleep mode function is selected, the valve opening sensor should use a sensor that does not affect the position memory under power failure conditions, such as a potentiometer or a full-stroke multi-turn absolute encoder. The accuracy and measurement stroke of the potentiometer are limited. There are two methods for using the electric actuator. One is to use the potentiometer stroke (by shifting) for the full stroke, the power-off position will not be lost, but the accuracy is very low; One is to use multiple potentiometer strokes, the positional accuracy is improved, but each time the stroke is exceeded, it depends on the electronic memory. When the power is off, there is no electronic memory position. If the battery is used for memory, it will consume more battery energy. . If the Hall pulse counting method is used, the counting is uninterrupted in real time. After the power is turned off, the battery is consumed and the battery capacity is insufficient. The full-stroke multi-turn absolute encoder is the most likely valve opening sensor in this mode. Of course, due to the extremely short data reading time, the accuracy of the data is required, and the data reliability requirement of the encoder is required. Very high. Some selected absolute encoders are single-turn function. If you need to use the electronic meter memory beyond the single turn, the power consumption after the power-off is large, it is not suitable for this half-sleep low-power mode. .
The full-stroke multi-turn absolute encoder uses RS485 active mode to transmit data, and it is sent once every 8mS. The encoder's power-on start-up time is extremely short, and the data includes two verification methods. The reliability is high, because it is a full-stroke multi-turn absolute. The value encoder is uniquely coded at each position in the total stroke. It is independent of the previous reading and does not require counting, counting and memory. Therefore, it is possible to use a gap-type power-on, reading mode, such as every 1-5 seconds. The MCU motherboard works intermittently (or twice), each working time is only tens of milliseconds, and the startup, data reading, processing, and sending work are quickly realized, and the rest of the time is in a sleep state, which is "half sleep low power consumption". mode".
Failure analysis:
Take the integral proportional adjustment type of the electric actuator as an example.
1, position sensor part
(1) After the electric actuator receives the opening and closing signals from the control system, the motor can rotate normally, but there is no valve position feedback. The possible reasons are:
1) The potentiometer of the position sensor and the stroke control mechanism cannot rotate coaxially, and it is necessary to check whether the connection part is damaged;
2) The potentiometer is damaged or the performance is deteriorated, and the resistance does not change with the rotation;
3) Whether the connection wires between the potentiometer and the magnifying plate of the position sensor are normal;
4) Whether the PM amplifier board is damaged, and whether there is a feedback signal.
(2) After the electric actuator receives the opening and closing signals from the control system, the motor can rotate normally, but the valve position feedback is always a fixed value, which does not change with the opening and closing of the valve. The possible reasons are:
1) The resistance of the conductive plastic potentiometer is a constant value, which does not change with the rotation, and the potentiometer is replaced.
2) Amplify the relevant part of the board and check the processing.
2, the actuator
After the actuator receives the switching signal from the control system, the motor does not turn and clicks. The reason may be:
1) the planetary gear portion of the reducer is stuck, damaged or deformed;
2) The helical gear transmission of the reducer is deformed or excessively worn or damaged;
3) Deformation damage, jamming, etc. of the turbine vortex or screw nut transmission part of the reducer;
4) The overall mechanical part is not well matched, not flexible, and needs to be adjusted for refueling.
3, electrical part failure
1) After the electric actuator receives the opening and closing signals from the control system, the motor does not turn and there is no click. The possible reason is: no AC power or power can not be added to the motor part or position locator part of the actuator; the PM amplifier board is not working properly, and the corresponding control signal cannot be issued; the solid state relay is partially damaged, and the amplifier board cannot be sent weakly. The signal is converted into a strong electric signal required by the motor; the motor thermal protection switch is damaged; the torque limit switch is damaged; the stroke limit switch is damaged; the manual/automatic switch position is incorrectly selected or the switch is damaged; the motor is damaged.
2) After the electric actuator receives the opening and closing signals from the control system, the motor does not turn and there is a click. The possible causes are: the starting capacitor of the motor is damaged; the motor coil is slightly short-circuited; the power supply voltage is not enough.
3) After the electric actuator receives the opening and closing signals from the control system, the motor shakes and is accompanied by a rattle. The reason may be: the output signal of the PM amplifier board is insufficient, the solid state relay is completely turned on, and the load voltage of the motor is caused. Insufficient; the performance of the solid state relay is deteriorated, causing its output to not be fully turned on.
