The correct installation of the control valve is just as important as the correct selection. The installation quality concerns the control system's operating performance, control quality, safety, and cost, and should be taken seriously.
The control valve is installed on the site and puts forward higher requirements for fire protection, explosion-proof, anti-leakage, etc. The noise pollution of the control valve is also increasingly concerned by relevant departments.
First, the provisions of the control valve installation and construction:
General requirements for installation and construction:
1. Control valve installation shall be in accordance with the design drawings and design documents.
2. The installation of control valves shall comply with the provisions of the relevant national standards, for example, the inspection and evaluation standards for the quality of construction and installation projects, the specifications for the construction and acceptance of industrial automation instruments, and the specifications for the construction and acceptance of electrical equipment installation projects.
3. The equipment, auxiliary equipment and main materials required for the installation of the control valve shall comply with the relevant provisions of the current national or ministerial standards.
II. Precautions for installation and construction:
Control valve installation considerations should be considered from the ease of operation, safety and standardization. The details are as follows.
(a), control valve installation position and orientation:
1. According to the design drawings and design documents, the installation location should have enough operating space for installation, operation and maintenance; its location should be avoided in the vibration, moisture, mechanical damage, strong electromagnetic interference, high temperature Sites with severe temperature changes and corrosive gases; the installation should be firm and flat; the installation position should be such that the actuator of the control valve is in the upper part of the adjustment mechanism, and Figure 6-8 shows the various installation orientations of the linear stroke control valve. Among them, the location is the preferred location and the second-selected location.
2. Flow of fluid in the control valve The flow of fluid in the control valve should be consistent with the arrow marked on the control valve body. Under special circumstances, this regulation may not be limited.
3, control valve connection Control valve connection has a threaded connection, flange connection and welding connection. Threaded connections are used for small-diameter control valves. When installing a screw-connected control valve, removable removable connections must be installed at the same time. There are two types of flange connection: flange connection and clamp connection. The nominal diameter of the connection flange should be the same as the diameter of the connection of the control valve. Flange also has different pressure rating, flange pressure rating should be consistent with the control valve pressure rating. The inner diameter of the flange should be equal to the inner diameter of the pipe. The allowable deviation of the perpendicularity between the flange surface and the pipe axis is l°. The flange sealing surface should be flush. Concentricity of flange and pipe allowable deviation t should be
Satisfy:
t ≤ 0.015D (1/β) (6-27)
In the formula, D is the inner diameter of the pipe; on the evening is the ratio of the inner diameter of the throttle piece to the inner diameter of the pipe under working conditions. When connecting flanges, the force should be even and suitable to avoid excessive pressure on the part. Avoid welding connections as much as possible. When welding connections must be installed removable removable connectors. When the control valve is connected, no new projections should be introduced inside the connecting pipe. For example, gaskets, welds, etc. should not protrude within the pipe.
4. Connection of control valve and upstream and downstream shut-off valve and bypass valve The upstream and downstream shut-off valves and bypass valve should be installed at the same time with the control valve. The pipe length between the upper and lower shut-off valves and the control valve should take into account the pipe resistance and the effect on the fluid flow state. The long length of the straight section is beneficial to the stability of the fluid passing through the shut-off valve, which can make the fluid flow smooth, reduce the influence of turbulence, and reduce the noise; the length of the straight section is short, and the fluid enters the control valve after the shutoff valve is not stable, making the noise stronger. However, the short pipe length is beneficial to reduce the pipeline resistance, increase the pressure drop at both ends of the control valve, and reduce the distortion of the flow characteristics, which is conducive to the stable operation of the control system. Therefore, it should be weighed and considered comprehensively. Generally, there should be a straight pipe section of 10D to 20D on the upstream side and a straight pipe section of 3D to 7D on the downstream side. D is the nominal diameter of the pipe, and if necessary, a rectifying device should be provided.
(B), the choice of connection options.
1. There are several ways to connect the control valve with the upper and lower shut-off valves. Several commonly used connection solutions are available. In the figure, the layout of the plan A is compact, the floor space is small, it is easy to maintain and operate, and the system is easy to vent or drain. However, it is often not possible to satisfy enough straight pipe lengths and cause noise enhancement. The area of ​​the structure of Plan B is large, and the position of the control valve can be installed on the lower part or the upper part, which is easy to adapt to the operation requirements, but the length of the straight pipe section is not easy to guarantee. The structure of scheme C is suitable for angle control valves, which can reduce the number of elbows and occupy a small area. The flow direction of the bottom-entry side may have a longer upstream straight section length. The structure of scheme D is similar to scheme B and covers a large area. The structure of scheme E is applicable to the angle valve. Compared with scheme C, the length of the straight section on the upstream side is shortened, which is not conducive to the stability of the fluid. The structure of scheme F is the most common connection structure. It occupies a large area and has a small pipeline resistance, but it has less space for operation and maintenance.
2. Connection of relief valve, vent valve, and drain valve, in order to facilitate the removal of the control valve, pressure relief should be performed before and after the valve is disassembled. The relief valve should be installed in the control valve and the upstream and downstream shut-off valves. between.
3. The vent valve and drain valve are used to discharge the non-condensable gas and condensate entrained in the fluid. When installing the controlled fluid, which is gas or steam, the drain valve should be installed at the lowest position of the control valve group in order to facilitate the discharge of condensate. When the fluid to be controlled is a liquid, the vent valve should be installed at the highest position of the control valve group in order to facilitate the venting of the non-condensable gas.
4, bypass valve. When the control valve is dismantled and repaired, the bypass valve can be used to operate the production process. When the traffic is controlled too large. When the control valve cannot be normally adjusted, as a contingency measure, a bypass valve can also be used as a parallel connection scheme of the control valve to control the process. To reduce costs, large-diameter control valves are equipped with handwheel actuators that can be used instead of bypass valves. The installation of the bypass valve should be easy to operate. It forms a control valve group together with the upstream and downstream shut-off valves of the control valve. Therefore, the installation should be matched with them and the construction and installation should be completed at the same time. The nominal diameter of the bypass valve is the same as the nominal diameter of the pipeline, and the withstand voltage level is also consistent with the process withstand voltage level.
5. Installation of actuators Usually, the actuator is directly connected to the valve body of the control valve. However, when the actuators such as the hydraulic actuator and the long-stroke actuator are separated from the valve body of the control valve, attention should be paid when installing the actuator to the actuator. Rods and mechanical moving parts should be flexible without loosening or twisting. The length of the connecting rod should be stable, flexible and reliable in the full stroke range. When connecting with the valve body of the control valve with thermal displacement of the process pipe, the relative position between the actuator and the valve body of the control valve should be kept constant. There are two types of side-mounted and top-mounted actuators, and there should be room for operation during installation. The handwheel operation should be flexible and there is no stuck or twisted phenomenon. There should be an indication of the relationship between the direction of rotation of the hand wheel and the valve opening. Limit devices should be adjusted properly to provide protection. The hydraulic actuator should be installed below the controller. If it must be higher than the controller, the height difference should not exceed 1.0m, and the exhaust valve should be installed at the pipeline gathering place, and the non-return valve should be installed near the controller. Automatic shut-off valve.
6. Installation of the valve positioner The valve position detection device of the valve positioner is directly connected to the valve stem or valve shaft of the control valve. Therefore, it is necessary to ensure that the feedback signal can correctly and timely reflect the valve position signal and change during installation. Usually, the valve positioner is supplied with the control valve, and the manufacturer completes the connection between the two. When the control of the production process requires the addition of a valve positioner, the correctness, reliability, and flexibility of the valve positioner position detection device should be ensured. The mechanical clearance of the feedback lever fulcrum should be as small as possible. The signal line of the valve positioner should be properly connected. The gas source line, output line, and input line should be marked on the nameplate. The valve position indicator of the valve positioner should be suitable for operation and maintenance personnel observation.
7. Installation of other accessories Other accessories include valve position sensors, solenoid valves, limit switches, relays, electrical converters, etc. The installation shall comply with the relevant provisions of the product specification. Small flow control valves should be installed upstream of the filter. When the turbulence is serious, install the rectifier on the upstream side.
8. Installation of connecting pipelines The installation of connecting pipelines should pay attention to the following matters.
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The control valve is installed on the site and puts forward higher requirements for fire protection, explosion-proof, anti-leakage, etc. The noise pollution of the control valve is also increasingly concerned by relevant departments.
First, the provisions of the control valve installation and construction:
General requirements for installation and construction:
1. Control valve installation shall be in accordance with the design drawings and design documents.
2. The installation of control valves shall comply with the provisions of the relevant national standards, for example, the inspection and evaluation standards for the quality of construction and installation projects, the specifications for the construction and acceptance of industrial automation instruments, and the specifications for the construction and acceptance of electrical equipment installation projects.
3. The equipment, auxiliary equipment and main materials required for the installation of the control valve shall comply with the relevant provisions of the current national or ministerial standards.
II. Precautions for installation and construction:
Control valve installation considerations should be considered from the ease of operation, safety and standardization. The details are as follows.
(a), control valve installation position and orientation:
1. According to the design drawings and design documents, the installation location should have enough operating space for installation, operation and maintenance; its location should be avoided in the vibration, moisture, mechanical damage, strong electromagnetic interference, high temperature Sites with severe temperature changes and corrosive gases; the installation should be firm and flat; the installation position should be such that the actuator of the control valve is in the upper part of the adjustment mechanism, and Figure 6-8 shows the various installation orientations of the linear stroke control valve. Among them, the location is the preferred location and the second-selected location.
2. Flow of fluid in the control valve The flow of fluid in the control valve should be consistent with the arrow marked on the control valve body. Under special circumstances, this regulation may not be limited.
3, control valve connection Control valve connection has a threaded connection, flange connection and welding connection. Threaded connections are used for small-diameter control valves. When installing a screw-connected control valve, removable removable connections must be installed at the same time. There are two types of flange connection: flange connection and clamp connection. The nominal diameter of the connection flange should be the same as the diameter of the connection of the control valve. Flange also has different pressure rating, flange pressure rating should be consistent with the control valve pressure rating. The inner diameter of the flange should be equal to the inner diameter of the pipe. The allowable deviation of the perpendicularity between the flange surface and the pipe axis is l°. The flange sealing surface should be flush. Concentricity of flange and pipe allowable deviation t should be
Satisfy:
t ≤ 0.015D (1/β) (6-27)
In the formula, D is the inner diameter of the pipe; on the evening is the ratio of the inner diameter of the throttle piece to the inner diameter of the pipe under working conditions. When connecting flanges, the force should be even and suitable to avoid excessive pressure on the part. Avoid welding connections as much as possible. When welding connections must be installed removable removable connectors. When the control valve is connected, no new projections should be introduced inside the connecting pipe. For example, gaskets, welds, etc. should not protrude within the pipe.
4. Connection of control valve and upstream and downstream shut-off valve and bypass valve The upstream and downstream shut-off valves and bypass valve should be installed at the same time with the control valve. The pipe length between the upper and lower shut-off valves and the control valve should take into account the pipe resistance and the effect on the fluid flow state. The long length of the straight section is beneficial to the stability of the fluid passing through the shut-off valve, which can make the fluid flow smooth, reduce the influence of turbulence, and reduce the noise; the length of the straight section is short, and the fluid enters the control valve after the shutoff valve is not stable, making the noise stronger. However, the short pipe length is beneficial to reduce the pipeline resistance, increase the pressure drop at both ends of the control valve, and reduce the distortion of the flow characteristics, which is conducive to the stable operation of the control system. Therefore, it should be weighed and considered comprehensively. Generally, there should be a straight pipe section of 10D to 20D on the upstream side and a straight pipe section of 3D to 7D on the downstream side. D is the nominal diameter of the pipe, and if necessary, a rectifying device should be provided.
(B), the choice of connection options.
1. There are several ways to connect the control valve with the upper and lower shut-off valves. Several commonly used connection solutions are available. In the figure, the layout of the plan A is compact, the floor space is small, it is easy to maintain and operate, and the system is easy to vent or drain. However, it is often not possible to satisfy enough straight pipe lengths and cause noise enhancement. The area of ​​the structure of Plan B is large, and the position of the control valve can be installed on the lower part or the upper part, which is easy to adapt to the operation requirements, but the length of the straight pipe section is not easy to guarantee. The structure of scheme C is suitable for angle control valves, which can reduce the number of elbows and occupy a small area. The flow direction of the bottom-entry side may have a longer upstream straight section length. The structure of scheme D is similar to scheme B and covers a large area. The structure of scheme E is applicable to the angle valve. Compared with scheme C, the length of the straight section on the upstream side is shortened, which is not conducive to the stability of the fluid. The structure of scheme F is the most common connection structure. It occupies a large area and has a small pipeline resistance, but it has less space for operation and maintenance.
2. Connection of relief valve, vent valve, and drain valve, in order to facilitate the removal of the control valve, pressure relief should be performed before and after the valve is disassembled. The relief valve should be installed in the control valve and the upstream and downstream shut-off valves. between.
3. The vent valve and drain valve are used to discharge the non-condensable gas and condensate entrained in the fluid. When installing the controlled fluid, which is gas or steam, the drain valve should be installed at the lowest position of the control valve group in order to facilitate the discharge of condensate. When the fluid to be controlled is a liquid, the vent valve should be installed at the highest position of the control valve group in order to facilitate the venting of the non-condensable gas.
4, bypass valve. When the control valve is dismantled and repaired, the bypass valve can be used to operate the production process. When the traffic is controlled too large. When the control valve cannot be normally adjusted, as a contingency measure, a bypass valve can also be used as a parallel connection scheme of the control valve to control the process. To reduce costs, large-diameter control valves are equipped with handwheel actuators that can be used instead of bypass valves. The installation of the bypass valve should be easy to operate. It forms a control valve group together with the upstream and downstream shut-off valves of the control valve. Therefore, the installation should be matched with them and the construction and installation should be completed at the same time. The nominal diameter of the bypass valve is the same as the nominal diameter of the pipeline, and the withstand voltage level is also consistent with the process withstand voltage level.
5. Installation of actuators Usually, the actuator is directly connected to the valve body of the control valve. However, when the actuators such as the hydraulic actuator and the long-stroke actuator are separated from the valve body of the control valve, attention should be paid when installing the actuator to the actuator. Rods and mechanical moving parts should be flexible without loosening or twisting. The length of the connecting rod should be stable, flexible and reliable in the full stroke range. When connecting with the valve body of the control valve with thermal displacement of the process pipe, the relative position between the actuator and the valve body of the control valve should be kept constant. There are two types of side-mounted and top-mounted actuators, and there should be room for operation during installation. The handwheel operation should be flexible and there is no stuck or twisted phenomenon. There should be an indication of the relationship between the direction of rotation of the hand wheel and the valve opening. Limit devices should be adjusted properly to provide protection. The hydraulic actuator should be installed below the controller. If it must be higher than the controller, the height difference should not exceed 1.0m, and the exhaust valve should be installed at the pipeline gathering place, and the non-return valve should be installed near the controller. Automatic shut-off valve.
6. Installation of the valve positioner The valve position detection device of the valve positioner is directly connected to the valve stem or valve shaft of the control valve. Therefore, it is necessary to ensure that the feedback signal can correctly and timely reflect the valve position signal and change during installation. Usually, the valve positioner is supplied with the control valve, and the manufacturer completes the connection between the two. When the control of the production process requires the addition of a valve positioner, the correctness, reliability, and flexibility of the valve positioner position detection device should be ensured. The mechanical clearance of the feedback lever fulcrum should be as small as possible. The signal line of the valve positioner should be properly connected. The gas source line, output line, and input line should be marked on the nameplate. The valve position indicator of the valve positioner should be suitable for operation and maintenance personnel observation.
7. Installation of other accessories Other accessories include valve position sensors, solenoid valves, limit switches, relays, electrical converters, etc. The installation shall comply with the relevant provisions of the product specification. Small flow control valves should be installed upstream of the filter. When the turbulence is serious, install the rectifier on the upstream side.
8. Installation of connecting pipelines The installation of connecting pipelines should pay attention to the following matters.