There are many types of valves and they are used in a wide range of applications. Sometimes it is the main equipment in the pipeline, it plays a controlling role; sometimes it is a secondary equipment, which plays a supporting role. If used improperly, there will be "run, run, drip, leak" phenomenon, lighter affects production, and serious people cause accidents. So understanding and using the valve correctly is a very important issue.
1 valve classification
There are many types of valves used in heating systems. Such as gate valves, globe valves, ball valves, butterfly valves, check valves, safety valves, regulating valves, balancing valves, self-operating balancing valves, etc. Introduce one by one below.
1.1 Gate valve
Also called gate valve, gate valve, is a widely used valve.
Working principle: The sealing surface of the ram and the sealing surface of the valve seat are smooth, flat and consistent, and processed into a very close and tight sealing pair. The gate is turned on and off by the lifting and lowering of the valve stem to form a turn-on and turn-off of the medium. It acts as a shut-off in the pipeline.
Advantages: the fluid resistance is small; the sealing surface is not eroded when fully open; it can be used in the case of two-way flow of the medium, no directionality; strong and durable; not only suitable for small valves, but also for large valves.
Disadvantages: high height; long opening and closing time; cumbersome; difficult to repair; if it is a large diameter gate valve, manual operation is more laborious.
The gate valve is divided into the rod type and the dark rod type according to the different stems; the parallel structure and the wedge type according to the structure of the gate; and the division of the single gate and the double gate. In the heating project, the common-wing wedge type single gate valve (Z41H-16C) and the dark-rod wedge type single gate valve (Z45T-10) are used. The former is installed on the primary side of the heat station, and the latter is installed in the heat station. Secondary side. It generally serves two purposes: as a master device to act as a switch; as an auxiliary device for maintenance before and after the master device.
When installing the gate valve, do not place the handwheel below the horizontal line (flip), otherwise the medium will remain in the valve cover for a long time, which will easily corrode the valve stem. In the heating project, the gate valve used to be the main force in the valve. Now with the widespread adoption of butterfly valves, gate valves have been replaced by butterfly valves.
1.2 Globe valve
It is also a widely used valve. The general diameter is below 100 mm. It works like a gate valve, except that the closing member (valve) moves along the centerline of the seat. It acts as a shut-off in the pipeline and also allows a rough adjustment of the flow.
Advantages: easy to manufacture, easy to maintain, durable.
Disadvantages: Only allow the medium to flow in one direction, and have directionality during installation. Large flow resistance and poor sealing.
According to the structure, it is divided into straight-through type, right-angle type, direct current type and balanced type. Flange straight-through (J41H) and internally threaded straight-through (J11H) are generally used in engineering. The shut-off valve is directional and cannot be reversed. It is not advisable to fall down.
In our production and life, in the past, straight-through, small-diameter globe valves were used, and now they have gradually been replaced by ball valves.
1.3 Ball valve
Compared with gate valves and globe valves, ball valves are a new type of valve that is gradually being widely used. Its working principle is: the valve core is a sphere with a through cavity, and the valve core is controlled by the valve stem to rotate 90° to make the valve unblocked or blocked. It acts as a shut-off in the pipeline.
Advantages: In addition to the advantages of gate valve and globe valve, it has the advantages of small volume, good sealing (zero leakage) and easy operation. Currently widely used in petrochemical, electric power, nuclear energy, aviation, aerospace and other departments.
Disadvantages: Maintenance is difficult.
Ball valves come in two forms: floating ball and fixed ball. In the heating project, some key locations, such as important branches, the population of the heat station, below DN250, often use imported ball valves. It is different from the structure of the domestic ball valve: the valve body of the domestic ball valve is generally two-piece, three-piece, flange connection; and the valve body of the imported ball valve is one-piece, welded connection, and there are fewer failure points. Its origin is in the Nordic countries such as Finland, Denmark and other countries with more developed heating technology. Such as Finland's NAVAL, VEXVE, Denmark's DAFOSS and so on. Due to its excellent sealing performance and reliable operation, it has long been favored by users. The ball valve has no directionality and can be installed at any angle. When the welding ball valve is installed horizontally, the valve must be opened to avoid the sparking injury and the surface of the ball when welding. When installing on the vertical pipe, if the interface is welded, the valve must be opened. If the interface is welded, the valve must be closed to avoid the internal valve. Burnt by high heat.
1.4 butterfly valve
In the heating system, it is currently the most widely used and the most widely used type of valve.
Working principle: The valve disc is a disc that rotates through the valve stem, and the valve flap rotates at 90 °C within the valve seat to realize the switch of the valve. It acts as a shut-off in the pipeline.
The flow can also be adjusted.
Advantages: simple structure, light weight, convenient operation and good sealing.
Disadvantages: When fully open, the valve plate (seal) is subject to media erosion.
In the heating project, the butterfly valve used has three eccentric metal sealing butterfly valves and rubber soft sealing butterfly valves.
1.4.1 Three eccentric metal sealing butterfly valve
The so-called "three eccentricity" refers to the displacement of the valve shaft and the valve plate in the relative position within the valve. The ordinary butterfly valve is an eccentricity, that is, the center line of the valve shaft deviates from the center line of the sealing surface (the center line of the valve plate); the high performance adds an eccentricity, that is, the center line of the valve shaft deviates from the center line of the valve (the center line of the pipe); The purpose of the double eccentricity is to separate the seal pairs from each other after the valve plate is opened to 20°, thereby reducing friction (cam effect). The triple eccentric butterfly valve adds a unique eccentricity to the above-mentioned double eccentricity - the inclined cone, which is the offset of the valve plate (the sealing surface is inclined at an angle to the vertical plane of the pipe). This makes the valve completely detached between the sealing pairs within the 90° stroke range, which not only enhances the cam effect, but also completely eliminates the friction; at the same time, when the valve is closed, when the sealing pair is gradually closed, a “wedge effect†is generated, with a minimum Torque achieves the most rigorous shutoff.
The so-called "metal seal" means that the valve seat and the seal ring are made of high-quality alloy with wear resistance, corrosion resistance and high temperature resistance. At the same time, in order to avoid the hard contact between the seal ring and the valve seat, the seal pair is designed to be in flexible contact, that is, to form "elasticity". Metal seal" to ensure tight shut-off, no friction. With a "three eccentric" structure and a "elastic metal seal", the valve is light, durable and well sealed.
Three eccentric metal sealing butterfly valves are generally used on the main line of the heating system and on the main branch. The caliber is DN300 or more.
The imported three eccentric metal sealing butterfly valve has no directionality, but generally has a recommended installation direction, and should not be reversed; the domestically produced directionality generally has a leakage level or a difference of one to two pressure levels, which cannot be reversed. If welding on a horizontal pipe, the valve should be closed to protect the seal; if welding on a vertical pipe, the valve should be closed, and water should be injected on the valve plate to extinguish the weld slag when welding the upper port. When installing on a horizontal pipe, it is recommended that the orientation be the valve stem horizontal or inclined with the vertical direction to ensure the bottom bearing is clean.
1.4.2 Rubber soft sealing butterfly valve
The disc is generally electroplated with ductile iron and the sealing ring is made of rubber. The sealing materials used are different and the properties are different. Commonly used are:
Dingqing rubber, applicable temperature is 12 °C +82 °C; ethylene propylene rubber, applicable temperature is 45 ° C - 135 ° C; heat resistant ethylene propylene rubber, suitable temperature is 20 ° C -150 ° C.
Commonly used in heating engineering are Clip-on (D371X) and flanged (D341X). The handle can be driven below the DN125 (D71, D41X). The clip-on butterfly valve is small and light, quick to open and close, easy to operate, easy to install, easy to maintain, excellent sealing and regulating performance, and cost-effective, so it should be vigorously adopted. The soft sealing butterfly valve has no directionality and can be installed at will.
When the butterfly valve is in storage, the valve plate should be opened 4° to 5°. In order to prevent the seal ring from being deformed for a long time, it will affect the seal.
1.5 check valve
Also called check valve, single flow door. A commonly used auxiliary valve.
Working principle: relying on the force of the fluid itself and the weight of the valve flap, the valve is automatically opened and closed. As its name suggests, its role is to prevent media from flowing backwards. Generally installed at the pump outlet to prevent water hammer from damaging the pump.
Commonly used in heating projects are horizontal lifting (H41H), single-lobed swing (H44H), double-lobed butterfly (H77H).
The check valve is directional and must not be reversed. Different types of check valves, according to their structure, have a fixed installation method, and must not be misplaced. The horizontal lifting type can only be installed on the horizontal pipe, and the valve flap is in the vertical state; the single-valve swing type can only be installed on the horizontal pipe, and the valve shaft is ensured to be horizontal; the double-lobed butterfly can be installed at will.
1.6 regulating valve
Also called the throttle valve. It is a common valve for the secondary network of the heating system.
Working principle: The shape and structure are similar to the stop valve. Only the sealing pair is different. The valve flap and the valve seat of the regulating valve are similar to the stopper and the bottle mouth of the thermos bottle, and the flow area is adjusted by changing the flow area by the movement of the valve flap. A scale on the valve shaft indicates the corresponding flow.
Function: Adjust the medium flow distribution between pipelines to achieve thermal balance.
Straight-through (T41H) has been used in heating engineering, but it has some disadvantages: it has a large flow resistance and should not be installed vertically. Thus, as technology advances, the balancing valve (PH45F) replaces the regulating valve.
1.7 balancing valve
Improved regulator valve. The flow channel adopts a direct current type, and the valve seat is changed to polytetrafluoroethylene;
Overcome the shortcomings of large flow resistance, and at the same time add two advantages: the seal is more reasonable, and has a cut-off function.
It is used on the secondary network of the heat station in the heating project and has excellent flow regulation characteristics, especially suitable for variable flow systems.
Directional, can be installed horizontally or vertically.
1.8 Self-balancing balancing valve
Also called flow control valve. It works by having a mechanism consisting of a Spring and a rubber membrane inside the valve that is connected to the valve stem. If the flow rate increases, an imbalance force is generated on it, causing the flap to move in the closing direction to reduce the flow area, reduce the flow rate, and return the flow to the set value. vice versa. Therefore, the flow rate after the valve is always kept constant, and the flow rate is controlled.
The hot population installed at the heating system, the branch point. Automatically eliminate hydraulic imbalance, improve system efficiency and achieve economic operation. Self-operated balancing valves are directional and must not be reversed.
1.9 safety valve
When the medium pressure exceeds the specified value, the valve can automatically open and release pressure. When the pressure is normal, it can automatically close to ensure the normal operation of the system. The valve functioning as this function is called a safety valve.
According to the structure: spring type, lever type, pulse type.
According to the amount of action: 10% of the ratio of the valve opening height to the valve seat diameter is called micro-open type, 20% to 30% is called full-open type.
According to the way of excretion: the medium is discharged through the pipeline and is called closed type, and is directly discharged into the air and called open type.
Taking the spring type as an example, the spring force is balanced with the normal pressure of the medium acting on the valve flap to close the sealing surface; when the medium pressure is too high, the spring is compressed, the valve plate is opened, and the medium is discharged from the medium; When the pressure drops back to normal, the spring force closes the valve again.
Safety valves are used in large quantities in pressure vessels.
2 Common problems in the use of valves
a) Keep the inside of the valve clean.
b) When lifting, do not attach the rope to the handwheel or valve stem.
c) Make sure the valve is working properly before installation.
d) When welding, the welder ground wire must be placed on the steel pipe of the same side weld to prevent the current from damaging the valve.
e) Cooling measures should be taken for the valve during the welding process of medium and small diameter valves.
f) Valves that do not open and close frequently in the pipeline should be rotated periodically.
In addition, there are environmental corrosion and protection problems to the valve, corrosion and protection of the inside of the valve, temperature and pressure problems, and sealing and leakage problems. In short, the valve is small, the learning is very big, and we have to continue to learn and summarize.
1 valve classification
There are many types of valves used in heating systems. Such as gate valves, globe valves, ball valves, butterfly valves, check valves, safety valves, regulating valves, balancing valves, self-operating balancing valves, etc. Introduce one by one below.
1.1 Gate valve
Also called gate valve, gate valve, is a widely used valve.
Working principle: The sealing surface of the ram and the sealing surface of the valve seat are smooth, flat and consistent, and processed into a very close and tight sealing pair. The gate is turned on and off by the lifting and lowering of the valve stem to form a turn-on and turn-off of the medium. It acts as a shut-off in the pipeline.
Advantages: the fluid resistance is small; the sealing surface is not eroded when fully open; it can be used in the case of two-way flow of the medium, no directionality; strong and durable; not only suitable for small valves, but also for large valves.
Disadvantages: high height; long opening and closing time; cumbersome; difficult to repair; if it is a large diameter gate valve, manual operation is more laborious.
The gate valve is divided into the rod type and the dark rod type according to the different stems; the parallel structure and the wedge type according to the structure of the gate; and the division of the single gate and the double gate. In the heating project, the common-wing wedge type single gate valve (Z41H-16C) and the dark-rod wedge type single gate valve (Z45T-10) are used. The former is installed on the primary side of the heat station, and the latter is installed in the heat station. Secondary side. It generally serves two purposes: as a master device to act as a switch; as an auxiliary device for maintenance before and after the master device.
When installing the gate valve, do not place the handwheel below the horizontal line (flip), otherwise the medium will remain in the valve cover for a long time, which will easily corrode the valve stem. In the heating project, the gate valve used to be the main force in the valve. Now with the widespread adoption of butterfly valves, gate valves have been replaced by butterfly valves.
1.2 Globe valve
It is also a widely used valve. The general diameter is below 100 mm. It works like a gate valve, except that the closing member (valve) moves along the centerline of the seat. It acts as a shut-off in the pipeline and also allows a rough adjustment of the flow.
Advantages: easy to manufacture, easy to maintain, durable.
Disadvantages: Only allow the medium to flow in one direction, and have directionality during installation. Large flow resistance and poor sealing.
According to the structure, it is divided into straight-through type, right-angle type, direct current type and balanced type. Flange straight-through (J41H) and internally threaded straight-through (J11H) are generally used in engineering. The shut-off valve is directional and cannot be reversed. It is not advisable to fall down.
In our production and life, in the past, straight-through, small-diameter globe valves were used, and now they have gradually been replaced by ball valves.
1.3 Ball valve
Compared with gate valves and globe valves, ball valves are a new type of valve that is gradually being widely used. Its working principle is: the valve core is a sphere with a through cavity, and the valve core is controlled by the valve stem to rotate 90° to make the valve unblocked or blocked. It acts as a shut-off in the pipeline.
Advantages: In addition to the advantages of gate valve and globe valve, it has the advantages of small volume, good sealing (zero leakage) and easy operation. Currently widely used in petrochemical, electric power, nuclear energy, aviation, aerospace and other departments.
Disadvantages: Maintenance is difficult.
Ball valves come in two forms: floating ball and fixed ball. In the heating project, some key locations, such as important branches, the population of the heat station, below DN250, often use imported ball valves. It is different from the structure of the domestic ball valve: the valve body of the domestic ball valve is generally two-piece, three-piece, flange connection; and the valve body of the imported ball valve is one-piece, welded connection, and there are fewer failure points. Its origin is in the Nordic countries such as Finland, Denmark and other countries with more developed heating technology. Such as Finland's NAVAL, VEXVE, Denmark's DAFOSS and so on. Due to its excellent sealing performance and reliable operation, it has long been favored by users. The ball valve has no directionality and can be installed at any angle. When the welding ball valve is installed horizontally, the valve must be opened to avoid the sparking injury and the surface of the ball when welding. When installing on the vertical pipe, if the interface is welded, the valve must be opened. If the interface is welded, the valve must be closed to avoid the internal valve. Burnt by high heat.
1.4 butterfly valve
In the heating system, it is currently the most widely used and the most widely used type of valve.
Working principle: The valve disc is a disc that rotates through the valve stem, and the valve flap rotates at 90 °C within the valve seat to realize the switch of the valve. It acts as a shut-off in the pipeline.
The flow can also be adjusted.
Advantages: simple structure, light weight, convenient operation and good sealing.
Disadvantages: When fully open, the valve plate (seal) is subject to media erosion.
In the heating project, the butterfly valve used has three eccentric metal sealing butterfly valves and rubber soft sealing butterfly valves.
1.4.1 Three eccentric metal sealing butterfly valve
The so-called "three eccentricity" refers to the displacement of the valve shaft and the valve plate in the relative position within the valve. The ordinary butterfly valve is an eccentricity, that is, the center line of the valve shaft deviates from the center line of the sealing surface (the center line of the valve plate); the high performance adds an eccentricity, that is, the center line of the valve shaft deviates from the center line of the valve (the center line of the pipe); The purpose of the double eccentricity is to separate the seal pairs from each other after the valve plate is opened to 20°, thereby reducing friction (cam effect). The triple eccentric butterfly valve adds a unique eccentricity to the above-mentioned double eccentricity - the inclined cone, which is the offset of the valve plate (the sealing surface is inclined at an angle to the vertical plane of the pipe). This makes the valve completely detached between the sealing pairs within the 90° stroke range, which not only enhances the cam effect, but also completely eliminates the friction; at the same time, when the valve is closed, when the sealing pair is gradually closed, a “wedge effect†is generated, with a minimum Torque achieves the most rigorous shutoff.
The so-called "metal seal" means that the valve seat and the seal ring are made of high-quality alloy with wear resistance, corrosion resistance and high temperature resistance. At the same time, in order to avoid the hard contact between the seal ring and the valve seat, the seal pair is designed to be in flexible contact, that is, to form "elasticity". Metal seal" to ensure tight shut-off, no friction. With a "three eccentric" structure and a "elastic metal seal", the valve is light, durable and well sealed.
Three eccentric metal sealing butterfly valves are generally used on the main line of the heating system and on the main branch. The caliber is DN300 or more.
The imported three eccentric metal sealing butterfly valve has no directionality, but generally has a recommended installation direction, and should not be reversed; the domestically produced directionality generally has a leakage level or a difference of one to two pressure levels, which cannot be reversed. If welding on a horizontal pipe, the valve should be closed to protect the seal; if welding on a vertical pipe, the valve should be closed, and water should be injected on the valve plate to extinguish the weld slag when welding the upper port. When installing on a horizontal pipe, it is recommended that the orientation be the valve stem horizontal or inclined with the vertical direction to ensure the bottom bearing is clean.
1.4.2 Rubber soft sealing butterfly valve
The disc is generally electroplated with ductile iron and the sealing ring is made of rubber. The sealing materials used are different and the properties are different. Commonly used are:
Dingqing rubber, applicable temperature is 12 °C +82 °C; ethylene propylene rubber, applicable temperature is 45 ° C - 135 ° C; heat resistant ethylene propylene rubber, suitable temperature is 20 ° C -150 ° C.
Commonly used in heating engineering are Clip-on (D371X) and flanged (D341X). The handle can be driven below the DN125 (D71, D41X). The clip-on butterfly valve is small and light, quick to open and close, easy to operate, easy to install, easy to maintain, excellent sealing and regulating performance, and cost-effective, so it should be vigorously adopted. The soft sealing butterfly valve has no directionality and can be installed at will.
When the butterfly valve is in storage, the valve plate should be opened 4° to 5°. In order to prevent the seal ring from being deformed for a long time, it will affect the seal.
1.5 check valve
Also called check valve, single flow door. A commonly used auxiliary valve.
Working principle: relying on the force of the fluid itself and the weight of the valve flap, the valve is automatically opened and closed. As its name suggests, its role is to prevent media from flowing backwards. Generally installed at the pump outlet to prevent water hammer from damaging the pump.
Commonly used in heating projects are horizontal lifting (H41H), single-lobed swing (H44H), double-lobed butterfly (H77H).
The check valve is directional and must not be reversed. Different types of check valves, according to their structure, have a fixed installation method, and must not be misplaced. The horizontal lifting type can only be installed on the horizontal pipe, and the valve flap is in the vertical state; the single-valve swing type can only be installed on the horizontal pipe, and the valve shaft is ensured to be horizontal; the double-lobed butterfly can be installed at will.
1.6 regulating valve
Also called the throttle valve. It is a common valve for the secondary network of the heating system.
Working principle: The shape and structure are similar to the stop valve. Only the sealing pair is different. The valve flap and the valve seat of the regulating valve are similar to the stopper and the bottle mouth of the thermos bottle, and the flow area is adjusted by changing the flow area by the movement of the valve flap. A scale on the valve shaft indicates the corresponding flow.
Function: Adjust the medium flow distribution between pipelines to achieve thermal balance.
Straight-through (T41H) has been used in heating engineering, but it has some disadvantages: it has a large flow resistance and should not be installed vertically. Thus, as technology advances, the balancing valve (PH45F) replaces the regulating valve.
1.7 balancing valve
Improved regulator valve. The flow channel adopts a direct current type, and the valve seat is changed to polytetrafluoroethylene;
Overcome the shortcomings of large flow resistance, and at the same time add two advantages: the seal is more reasonable, and has a cut-off function.
It is used on the secondary network of the heat station in the heating project and has excellent flow regulation characteristics, especially suitable for variable flow systems.
Directional, can be installed horizontally or vertically.
1.8 Self-balancing balancing valve
Also called flow control valve. It works by having a mechanism consisting of a Spring and a rubber membrane inside the valve that is connected to the valve stem. If the flow rate increases, an imbalance force is generated on it, causing the flap to move in the closing direction to reduce the flow area, reduce the flow rate, and return the flow to the set value. vice versa. Therefore, the flow rate after the valve is always kept constant, and the flow rate is controlled.
The hot population installed at the heating system, the branch point. Automatically eliminate hydraulic imbalance, improve system efficiency and achieve economic operation. Self-operated balancing valves are directional and must not be reversed.
1.9 safety valve
When the medium pressure exceeds the specified value, the valve can automatically open and release pressure. When the pressure is normal, it can automatically close to ensure the normal operation of the system. The valve functioning as this function is called a safety valve.
According to the structure: spring type, lever type, pulse type.
According to the amount of action: 10% of the ratio of the valve opening height to the valve seat diameter is called micro-open type, 20% to 30% is called full-open type.
According to the way of excretion: the medium is discharged through the pipeline and is called closed type, and is directly discharged into the air and called open type.
Taking the spring type as an example, the spring force is balanced with the normal pressure of the medium acting on the valve flap to close the sealing surface; when the medium pressure is too high, the spring is compressed, the valve plate is opened, and the medium is discharged from the medium; When the pressure drops back to normal, the spring force closes the valve again.
Safety valves are used in large quantities in pressure vessels.
2 Common problems in the use of valves
a) Keep the inside of the valve clean.
b) When lifting, do not attach the rope to the handwheel or valve stem.
c) Make sure the valve is working properly before installation.
d) When welding, the welder ground wire must be placed on the steel pipe of the same side weld to prevent the current from damaging the valve.
e) Cooling measures should be taken for the valve during the welding process of medium and small diameter valves.
f) Valves that do not open and close frequently in the pipeline should be rotated periodically.
In addition, there are environmental corrosion and protection problems to the valve, corrosion and protection of the inside of the valve, temperature and pressure problems, and sealing and leakage problems. In short, the valve is small, the learning is very big, and we have to continue to learn and summarize.
Other Manufacturing & Processing Machinery
Maanshan Hellen CNC Machine Tool Co., Ltd. , http://www.powder-compacting-press.com