Introduction to electric valves, 304 stainless steel valves, 321 stainless steel valves, electric valve introduction, 304 stainless steel valves, electric valves have a larger operating force than ordinary valves, the electric valve switching speed can be adjusted, the structure is simple, easy to maintain, and the valve can be used It is used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. During the action process, due to the buffering characteristics of the gas itself, it is not easily damaged by getting stuck, but it must have a gas source, and its control system is more complicated than an electric valve. This type of valve should generally be installed horizontally in pipelines.
1. Introduction
To put it simply, an electric valve uses an electric actuator to control the valve to open and close the valve. It can be divided into upper and lower parts, the upper part is the electric actuator, and the lower part is the valve.
Advantages: Good effect on liquid medium and large diameter gas, not affected by climate. Not affected by air pressure.
Disadvantages: high cost, not good in humid environment.
2. Operating principle
Electric valves usually consist of electric actuators and valves. Electric valves use electrical energy as power to drive the valve through an electric actuator to achieve the valve's switching action. In order to achieve the purpose of switching the pipeline medium.
The solenoid valve is a type of electric valve; it uses the magnetic field generated by the solenoid coil to pull the valve core, thereby changing the on-off state of the valve body. When the coil is powered off, the valve core relies on the pressure of the spring to return.
3. Purpose
Electric valve: used for analog regulation of pipeline medium flow in liquid, gas and air systems, and is AO control. In the control of large valves and air systems, electric valves can also be used for two-position switch control.
4. Operation method
A Preparation before operation
A.1 Before operating the valve, the operating instructions should be read carefully.
A.2 Be sure to know the flow direction of the gas before operation, and pay attention to check the valve opening and closing marks.
A.3 Check the appearance of the electric valve to see if it is damp. If it is damp, it must be dried. If other problems are found, they must be dealt with in time and must not be operated without faults.
A.4 For electric devices that have been out of use for more than 3 months, the clutch should be checked before starting. After confirming that the handle is in the manual position, check the insulation, steering and electrical circuits of the motor.
B Precautions for electric valve operation
B.1 When starting, confirm that the clutch handle is in the corresponding position
B.2 If the electric valve is controlled in the control room , turn the transfer switch to the REMOTE position, and then control the switch of the electric valve through the SCADA system.
B.3 If controlled manually, turn the transfer switch to the LOCAL position and operate the switch of the electric valve locally. When the electric valve is opened or closed in place, it will automatically stop working. Finally, turn the operation switch Hit to the middle position.
B.4 When using on-site operation of valves, the valve opening and closing instructions and valve stem operation should be monitored, and the valve opening and closing degree must meet the requirements.
B.5 When using on-site operation to fully close the valve, before the valve is closed in place, the electric valve closing should be stopped and micro-movement should be used to close the valve in place.
B.6 For valves whose stroke and super-torque controllers have been adjusted, when the valve is fully opened or fully closed for the first time, attention should be paid to monitoring its control of the stroke. If the valve does not stop when it reaches the switch position, A manual emergency stop should be initiated immediately.
B.7 During the process of opening and closing the valve, if it is found that the signal indicator light indicates incorrectly or the valve makes abnormal noise, the machine should be stopped in time for inspection.
B.8 The power supply to the electric valve should be turned off after successful operation.
B.9 When operating multiple valves at the same time, the operating sequence should be paid attention to and the production process requirements should be met.
B.10 When opening a larger diameter valve with a bypass valve, if the pressure difference between the two ends is large, the bypass valve should be opened first to regulate the pressure, and then the main valve should be opened: After the main valve is opened, the Close the bypass valve immediately.
B.11 When sending and receiving pigging balls (devices), the ball valves they pass must be fully open.
B.12 Ball valves, gate valves, stop valves, and butterfly valves can only be fully opened or fully closed, and adjustment is strictly prohibited.
B.13 During the operation of gate valves, stop valves and flat valves, when closing or opening to the top dead center or bottom dead center, they should rotate 1/2 to 1 turn.
5. Maintenance
Daily maintenance of electric valves
1. Electric valves should be stored in a dry and ventilated room, and both ends of the passage must be blocked.
2. Electric valves stored for a long time should be inspected regularly, dirt should be removed, and anti-rust oil should be applied to the processing surface.
3. After installation, regular inspections should be carried out. The main inspection items are:
(1) Wear of the sealing surface.
(2) Wear of the trapezoidal thread of the valve stem and valve stem nut.
(3) Whether the packing is out of date and ineffective. If it is damaged, it should be replaced in time.
(4) After the electric valve is overhauled and assembled, a sealing performance test should be carried out.
For electric valves in operation, all valve parts should be complete and intact. The flange threads and bolts on the bracket are indispensable. The threads should be intact and no loosening is allowed. If the fastening nut on the handwheel is found to be loose, tighten it in time to avoid wearing the connection or losing the handwheel and nameplate. If the handwheel is lost, it is not allowed to use an adjustable wrench to replace it, and it should be replaced in time. The packing gland is not allowed to be skewed or have no preload gap. For electric valves in environments that are easily contaminated by rain, snow, dust, sand and other contaminants, a protective cover must be installed on the valve stem. The scale on the electric valve should be kept complete, accurate and clear. The electric valve's lead seal, cap, pneumatic accessories, etc. should be complete and intact. The insulation jacket should have no dents or cracks.
It is not allowed to knock, stand on or support heavy objects on the operating electric valve; especially non-metallic electric valves and cast iron electric valves, it is even more prohibited.
6. Purchase
The valve electric device is an indispensable device for realizing valve program control, automatic control and remote control. Its movement process can be controlled by the stroke, torque or axial thrust. . Since the working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specifications of the device and the position of the valve on the pipeline or equipment, therefore, the correct selection of the valve electric device is crucial to preventing overload (the operating torque is higher than the control torque) is crucial. Usually, the basis for correctly selecting a valve electric device is as follows: Operating torque: The operating torque is the most important parameter for selecting a valve electric device. The output torque of the electric device should be 1.2 to 1.5 times the maximum operating torque of the valve.
Operating thrust: There are two main structures of the valve electric device: one is not equipped with a thrust plate and directly outputs torque; the other is equipped with a thrust plate and the output torque passes through the valve stem nut in the thrust plate. Converted to output thrust.
The number of rotations of the output shaft: The number of rotations of the output shaft of the valve electric device is related to the nominal diameter of the valve, the valve stem pitch, and the number of thread heads. It should be calculated according to M=H/ZS (M is The total number of rotations that the electric device should meet, H is the valve opening height, S is the valve stem transmission thread pitch, Z is the number of valve stem thread heads).
Valve stem diameter: For multi-turn rising stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through the valve stem of the matched valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be larger than the outer diameter of the valve stem of the rising stem valve. For partial-turn valves and concealed-stem valves in multi-turn valves, although the passage of the valve stem diameter does not need to be considered, the valve stem diameter and keyway size should also be fully considered when selecting and matching, so that they can work normally after assembly.
7. Installation precautions
The electric device of the electric valve is one of the devices used to operate the valve and connected to the valve. The device is driven by electricity, and its motion process can be controlled by stroke, torque or axial thrust. The working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specifications of the device and the position of the valve on the pipeline or equipment. Therefore, it is crucial to master the correct selection of valve electric devices and consider preventing overload (working torque higher than control torque) from occurring.
The correct selection of electric devices should be based on
1. Operating torque: Operating torque is the most important parameter when selecting a valve electric device. The output torque of the electric device should be 1.2 to 1.5 times the maximum operating torque of the valve.
2. Operating thrust: There are two main structures of the valve electric device. One is without a thrust plate, in which case the torque is output directly; the other is equipped with a thrust plate, in which case the output torque passes through the valve stem nut in the thrust plate. Converted to output thrust.
3． The number of rotations of the output shaft: The number of rotations of the output shaft of the valve electric device is related to the nominal diameter of the valve, the valve stem pitch, and the number of thread heads. It is calculated according to M=H/ZS (where: M is the requirement that the electric device should meet The total number of turns; H is the opening height of the valve, mm; S is the pitch of the valve stem driving thread, mm; Z is the number of valve stem thread heads)
4. Valve stem diameter: For multi-turn rising stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through the valve stem of the matched valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be larger than the outer diameter of the valve stem of the rising stem valve. For partial-turn valves and concealed-stem valves in multi-turn valves, although the passage of the valve stem diameter does not need to be considered, the valve stem diameter and keyway size should also be fully considered when selecting and matching, so that they can work normally after assembly.
5. Output speed: The valve opens and closes very quickly and is prone to water hammer. Therefore, the appropriate opening and closing speed should be selected according to different usage conditions.
6． Installation and connection methods: The installation methods of electric devices include vertical installation, horizontal installation, and floor installation; the connection methods are: thrust plate; valve stem passing (rising stem multi-turn valve); concealed stem multi-turn; no thrust plate; valve stem does not Passed; The partial-turn electric device has a wide range of uses and is an indispensable device for realizing valve program control, automatic control and remote control. It is mainly used on closed-circuit valves. But the special requirements of the valve electric device cannot be ignored - it must be able to limit the torque or axial force. Usually valve electric devices use couplings that limit torque.
When the specifications of the electric device are determined, its control torque is also determined. Motors are generally not overloaded when they operate for a predetermined period of time. However, it can be overloaded if the following conditions occur:
1. The power supply voltage is low and the required torque cannot be obtained, causing the motor to stop rotating.
2． The torque limiting mechanism is incorrectly set so that it is greater than the stopping torque, causing excessive torque to be continuously generated and causing the motor to stop rotating.
3． If used intermittently like jogging, the heat generated accumulates and exceeds the allowable temperature rise of the motor.
4. For some reason, the circuit of the torque limiting mechanism malfunctions, resulting in excessive torque.
5. The operating environment temperature is too high, which will relatively reduce the heat capacity of the motor.
The above are some reasons for overloading. Motor overheating caused by these reasons should be considered in advance and measures should be taken to prevent overheating.
In the past, the methods to protect motors were to use fuses, overcurrent relays, thermal relays, thermostats, etc., but these methods all have their own pros and cons. For equipment with variable loads such as electric devices, they are absolutely There is no reliable method of protection. Therefore, a combination of various methods must be adopted. However, due to the different load conditions of each electric device, it is difficult to propose a unified method. But by summarizing most situations, we can also find the most common points.
The overload protection methods adopted can be summarized into two types
1. Judge the increase or decrease of the motor input current;
2. Determine the heat generated by the motor itself.
No matter which of the above two methods, the time margin given by the motor's thermal capacity must be considered. It is difficult to make it consistent with the thermal capacity characteristics of the motor using a single method. Therefore, we should choose a method that can reliably act according to the cause of overload - a combination method to achieve comprehensive overload protection.
The motor of Rotork electric device has a thermostat embedded in the winding that is consistent with the insulation level of the motor. When the rated temperature is reached, the motor control circuit will be cut off. The heat capacity of the thermostat itself is small, and its time-limiting characteristics are determined by the heat capacity characteristics of the motor, so this is a reliable method.
Basic protection methods for overload
1. A thermostat is used for overload protection of the motor in continuous operation or inching operation;
2. Thermal relay is used to protect the motor from stalling;
3. Use fuses or overcurrent relays for short circuit accidents.
The correct selection of valve electric devices and the prevention of overload are closely related and should be paid attention to.
Introduction to electric valves, 304 stainless steel valves, 321 stainless steel valves
Introduction to electric valves 304 stainless steel valves
The operating force distance of electric valves is larger than that of ordinary valves. The switching speed can be adjusted, the structure is simple, and it is easy to maintain. The valve can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal, and radioactive media. During the action process, due to the buffering characteristics of the gas itself, it is not easily damaged by getting stuck, but it must have a gas source, and its control system is more complicated than an electric valve. This type of valve should generally be installed horizontally in pipelines.
1. Introduction
To put it simply, an electric valve uses an electric actuator to control the valve to open and close the valve. It can be divided into upper and lower parts, the upper part is the electric actuator, and the lower part is the valve.
Advantages: Good effect on liquid medium and large diameter gas, not affected by climate. Not affected by air pressure.
Disadvantages: high cost, not good in humid environment.
2. Operating principle
Electric valves usually consist of electric actuators and valves. Electric valves use electrical energy as power to drive the valve through an electric actuator to achieve the valve's switching action. In order to achieve the purpose of switching the pipeline medium.
The solenoid valve is a type of electric valve; it uses the magnetic field generated by the solenoid coil to pull the valve core, thereby changing the on-off state of the valve body. When the coil is powered off, the valve core relies on the pressure of the spring to return.
3. Purpose
Electric valve: used for analog regulation of pipeline medium flow in liquid, gas and air systems, and is AO control. In the control of large valves and air systems, electric valves can also be used for two-position switch control.
4. Operation method
A Preparation before operation
A.1 Before operating the valve, the operating instructions should be read carefully.
A.2 Be sure to know the flow direction of the gas before operation, and pay attention to check the valve opening and closing marks.
A.3 Check the appearance of the electric valve to see if it is damp. If it is damp, it must be dried. If other problems are found, they must be dealt with in time and must not be operated without faults.
A.4 For electric devices that have been out of use for more than 3 months, the clutch should be checked before starting. After confirming that the handle is in the manual position, check the insulation, steering and electrical circuits of the motor.
B Precautions for electric valve operation
B.1 When starting, confirm that the clutch handle is in the corresponding position
B.2 If the electric valve is controlled in the control room , turn the transfer switch to the REMOTE position, and then control the switch of the electric valve through the SCADA system.
B.3 If controlled manually, turn the transfer switch to the LOCAL position and operate the switch of the electric valve locally. When the electric valve is opened or closed in place, it will automatically stop working. Finally, turn the operation switch Hit to the middle position.
B.4 When using on-site operation of valves, the valve opening and closing instructions and valve stem operation should be monitored, and the valve opening and closing degree must meet the requirements.
B.5 When using on-site operation to fully close the valve, before the valve is closed in place, the electric valve closing should be stopped and micro-movement should be used to close the valve in place.
B.6 For valves whose stroke and super-torque controllers have been adjusted, when the valve is fully opened or fully closed for the first time, attention should be paid to monitoring its control of the stroke. If the valve does not stop when it reaches the switch position, A manual emergency stop should be initiated immediately.
B.7 During the process of opening and closing the valve, if you find that the signal indicator light indicates incorrectly or the valve makes abnormal noise, you should stop it for inspection in time.
B.8 The power supply to the electric valve should be turned off after successful operation.
B.9 When operating multiple valves at the same time, the operating sequence should be paid attention to and the production process requirements should be met.
B.10 When opening a larger diameter valve with a bypass valve, if the pressure difference between the two ends is large, the bypass valve should be opened first to regulate the pressure, and then the main valve should be opened: After the main valve is opened, the Close the bypass valve immediately.
B.11 When sending and receiving pigging balls (devices), the ball valves they pass must be fully open.
B.12 Ball valves, gate valves, stop valves, and butterfly valves can only be fully opened or fully closed, and adjustment is strictly prohibited.
B.13 During the operation of gate valves, stop valves and flat valves, when closing or opening to the top dead center or bottom dead center, they should rotate 1/2 to 1 turn.
5. Maintenance
Daily maintenance of electric valves
1. Electric valves should be stored in a dry and ventilated room, and both ends of the passage must be blocked.
2. Electric valves stored for a long time should be inspected regularly, dirt should be removed, and anti-rust oil should be applied to the processing surface.
3. After installation, regular inspections should be carried out. The main inspection items are: (1) Wear of the sealing surface.
(2) Wear of the trapezoidal thread of the valve stem and valve stem nut.
(3) Whether the packing is out of date and ineffective. If it is damaged, it should be replaced in time.
(4) After the electric valve is overhauled and assembled, a sealing performance test should be carried out.
For electric valves in operation, all valve parts should be complete and intact. The flange threads and bolts on the bracket are indispensable. The threads should be intact and no loosening is allowed. If the fastening nut on the handwheel is found to be loose, tighten it in time to avoid wearing the connection or losing the handwheel and nameplate. If the handwheel is lost, it is not allowed to use an adjustable wrench to replace it, and it should be replaced in time. The packing gland is not allowed to be skewed or have no preload gap. For electric valves in environments that are easily contaminated by rain, snow, dust, sand and other contaminants, a protective cover must be installed on the valve stem. The scale on the electric valve should be kept complete, accurate and clear. The electric valve's lead seal, cap, pneumatic accessories, etc. should be complete and intact. The insulation jacket should have no dents or cracks.
It is not allowed to knock, stand on or support heavy objects on the operating electric valve; especially non-metallic electric valves and cast iron electric valves, it is even more prohibited.
6. Purchase
The valve electric device is an indispensable device for realizing valve program control, automatic control and remote control. Its movement process can be controlled by the stroke, torque or axial thrust. . Since the working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specifications of the device and the position of the valve on the pipeline or equipment, therefore, the correct selection of the valve electric device is crucial to preventing overload (the operating torque is higher than the control torque) is crucial. Usually, the basis for correctly selecting a valve electric device is as follows: Operating torque: The operating torque is the most important parameter for selecting a valve electric device. The output torque of the electric device should be 1.2 to 1.5 times the maximum operating torque of the valve.
Operating thrust: There are two main structures of the valve electric device: one is not equipped with a thrust plate and directly outputs torque; the other is equipped with a thrust plate and the output torque passes through the valve stem nut in the thrust plate. Converted to output thrust.
The number of rotations of the output shaft: The number of rotations of the output shaft of the valve electric device is related to the nominal diameter of the valve, the valve stem pitch, and the number of thread heads. It should be calculated according to M=H/ZS (M is The total number of rotations that the electric device should meet, H is the valve opening height, S is the valve stem transmission thread pitch, Z is the number of valve stem thread heads).
Valve stem diameter: For multi-turn rising stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through the valve stem of the matched valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be larger than the outer diameter of the valve stem of the rising stem valve. For partial-turn valves and concealed-stem valves in multi-turn valves, although the passage of the valve stem diameter does not need to be considered, the valve stem diameter and keyway size should also be fully considered when selecting and matching, so that they can work normally after assembly.
7. Installation precautions
The electric device of the electric valve is one of the devices used to operate the valve and connected to the valve. The device is driven by electricity, and its motion process can be controlled by stroke, torque or axial thrust. The working characteristics and utilization rate of the valve electric device depend on the type of valve, the working specifications of the device and the position of the valve on the pipeline or equipment. Therefore, it is crucial to master the correct selection of valve electric devices and consider preventing overload (working torque higher than control torque) from occurring.
The correct selection of electric devices should be based on
1. Operating torque: Operating torque is the most important parameter when selecting a valve electric device. The output torque of the electric device should be 1.2 to 1.5 times the maximum operating torque of the valve.
2． Operating thrust: There are two main structures of the valve electric device. One is without a thrust plate, in which case the torque is output directly; the other is equipped with a thrust plate, in which case the output torque passes through the valve stem nut in the thrust plate. Converted to output thrust.
3． The number of rotations of the output shaft: The number of rotations of the output shaft of the valve electric device is related to the nominal diameter of the valve, the valve stem pitch, and the number of thread heads. It is calculated according to M=H/ZS (where: M is the requirement that the electric device should meet The total number of turns; H is the opening height of the valve, mm; S is the pitch of the valve stem driving thread, mm; Z is the number of valve stem thread heads)
4. Valve stem diameter: For multi-turn rising stem valves, if the maximum valve stem diameter allowed by the electric device cannot pass through the valve stem of the matched valve, it cannot be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be larger than the outer diameter of the valve stem of the rising stem valve. For partial-turn valves and concealed-stem valves in multi-turn valves, although the passage of the valve stem diameter does not need to be considered, the valve stem diameter and keyway size should also be fully considered when selecting and matching, so that they can work normally after assembly.
5. Output speed: The valve opens and closes very quickly and is prone to water hammer. Therefore, the appropriate opening and closing speed should be selected according to different usage conditions.
6． Installation and connection methods: The installation methods of electric devices include vertical installation, horizontal installation, and floor installation; the connection methods are: thrust plate; valve stem passing (rising stem multi-turn valve); concealed stem multi-turn; no thrust plate; valve stem does not Passed; The partial-turn electric device has a wide range of uses and is an indispensable device for realizing valve program control, automatic control and remote control. It is mainly used on closed-circuit valves. But the special requirements of the valve electric device cannot be ignored - it must be able to limit the torque or axial force. Usually valve electric devices use couplings that limit torque.
When the specifications of the electric device are determined, its control torque is also determined. Motors are generally not overloaded when they operate for a predetermined period of time. However, it can be overloaded if the following conditions occur:
1. The power supply voltage is low and the required torque cannot be obtained, causing the motor to stop rotating.
2． The torque limiting mechanism is incorrectly set so that it is greater than the stopping torque, causing excessive torque to be continuously generated and causing the motor to stop rotating.
3． If used intermittently like jogging, the heat generated accumulates and exceeds the allowable temperature rise of the motor.
4. For some reason, the circuit of the torque limiting mechanism malfunctions, resulting in excessive torque.
5. The operating environment temperature is too high, which will relatively reduce the heat capacity of the motor.
The above are some reasons for overloading. Motor overheating caused by these reasons should be considered in advance and measures should be taken to prevent overheating.
In the past, the methods to protect motors were to use fuses, overcurrent relays, thermal relays, thermostats, etc., but these methods all have their own pros and cons. For equipment with variable loads such as electric devices, they are absolutely There is no reliable method of protection. Therefore, a combination of various methods must be adopted. However, due to the different load conditions of each electric device, it is difficult to propose a unified method. But by summarizing most situations, we can also find the most common points.
The overload protection methods adopted can be summarized into two types
1. Judge the increase or decrease of the motor input current;
2. Determine the heat generated by the motor itself.
No matter which of the above two methods, the time margin given by the motor's thermal capacity must be considered. It is difficult to make it consistent with the thermal capacity characteristics of the motor using a single method. Therefore, we should choose a method that can reliably act according to the cause of overload - a combination method to achieve comprehensive overload protection.
The motor of Rotork electric device has a thermostat embedded in the winding that is consistent with the insulation level of the motor. When the rated temperature is reached, the motor control circuit will be cut off. The heat capacity of the thermostat itself is small, and its time-limiting characteristics are determined by the heat capacity characteristics of the motor, so this is a reliable method.
Basic protection methods against overload
1. A thermostat is used for overload protection of the motor in continuous operation or inching operation;
2. Thermal relay is used to protect the motor from stalling;
3. Use fuses or overcurrent relays for short circuit accidents.
The correct selection of valve electric devices and the prevention of overload are closely related and should be paid attention to.