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There are many types of gate valves, and knife gate valve is one of them, also called knife style gate valve. Depending on the type of structure, gate valves can be divided into flat gate valves and knife gate valves. According to the different connection methods, the knife gate valve can be divided into flange type, lug type and wafer type.   Compared with ordinary gate valve, the structure of knife gate valve is simple. It is small in size, flexible in operation and easy to install. It is more suitable for medium with high consistency and solid particles. As can be seen from the name, the knife gate valve mainly relies on the blade-shaped gate to cut off the medium. The gate has two sealing surfaces forming a wedge shape. The gate can be made into an integral rigid gate; it can also be made into an elastic gate that can produce a small amount of deformation and improve the sealing performance from the process. To sum up, the knife gate valve mainly highlights the following product advantages compared with ordinary gate valves:   The U-shaped gasket has a good sealing effect. The full diameter design makes the medium passing ability strong. At the same time, under the condition of dirty medium, it is easy to install, disassemble and maintain, and the sealing part of the valve can be replaced without removing the valve, which makes the maintenance of the valve easier. The gate with gate knife function has good gate breaking effect, can effectively cut off all kinds of sundries in the medium, and solve the leakage phenomenon after gate breaking of media containing blocks, particles and fibers. The ultra-short structure length of the knife gate valve, small size, small flow resistance, light weight, material saving and small effective space occupation.   Although the price of bonneted knife gate valve is higher than that of ordinary gate valve, its good performance has been generally recognized by the market.   The Scope Of Use Of The Knife Gate Valve: Mining, coal washing, iron and steel industry -- used for coal washing and washing pipelines, slag filtering pipelines, etc., ash discharge pipelines; Purification device - used for waste water, mud, dirt and clarified water with suspended solids; Paper industry - used for any concentration of pulp, material-water mixture; Power station ash removal - used for ash slurry.   Knife Gate Valve Installation Precautions Before installing the knife gate valve, check the valve cavity and sealing surface and other parts, and no dirt or sand is allowed to adhere. The bolts of each connecting part should be tightened evenly. Check that the packing parts are required to be pressed tightly, not only to ensure the sealing performance of the packing, but also to ensure the flexible opening of the gate; Before installing the valve, the user must check the valve model, connection size and pay attention to the flow direction of the medium to ensure the consistency with the valve requirements; When installing the valve, the user must reserve the necessary space for the valve drive; The wiring of the drive device must be carried out according to the circuit diagram; The knife gate valve must be maintained regularly, and must not be collided and squeezed at will, so as not to affect the sealing.

Butterfly valve, also known as flap valve, is often used in pipelines for conveying various corrosive and non-corrosive fluid media in engineering systems such as generators, coal gas, natural gas, liquefied petroleum gas, hot and cold air, chemical smelting, etc., for regulating and cutting off flow of the medium.   1. The working principle of butterfly valve   A butterfly valve is a valve that uses a circular butterfly plate as an opening and closing member and rotates with the valve stem to open, close and adjust the fluid channel. The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When it rotates to 90°, the valve is in a fully open state. By changing the deflection angle of the disc, the flow of the medium can be controlled.   2. Four types of butterfly valves   (1) Concentric butterfly valve   The structural feature of this kind of butterfly valve is that the shaft center of the valve stem, the center of the butterfly plate and the center of the body are in the same position. The structure is simple and the manufacture is convenient. Common rubber-lined butterfly valves belong to this category. The disadvantage is that due to the fact that the butterfly plate and the valve seat are always in a state of extrusion and scraping, the resistance distance is large and the wear is fast.   (2) Single eccentric butterfly valve   In order to solve the extrusion problem of the disc and the valve seat of the concentric butterfly valve, the single eccentric butterfly valve was produced. Its structural feature is that the shaft center of the valve stem deviates from the center of the butterfly plate, so that the upper and lower ends of the butterfly plate no longer become the rotation axis, which disperses and reduces the excessive extrusion between the upper and lower ends of the butterfly plate and the valve seat.   (3) Double offset butterfly valve   On the basis of the single eccentric butterfly valve, the most widely used double offset butterfly valve is further improved and formed. Its structural feature is that the shaft center of the valve stem deviates from the center of the disc and the center of the body. The effect of double eccentricity enables the disc to break away from the valve seat immediately after the valve is opened, which greatly eliminates unnecessary excessive extrusion and scratching of the disc and the valve seat, reduces the opening resistance, reduces wear, and improves the performance of the valve. Seat life.   (4) Triple offset butterfly valve   To withstand high temperature, a hard seal must be used, but the amount of leakage is large; to zero leakage, a soft seal must be used, but it is not resistant to high temperature. In order to overcome the contradiction of the double offset butterfly valve, the butterfly valve has been eccentric for the third time (deviation from the center line of the metal sealing surface). The structure is characterized in that the conical axis of the sealing surface of the butterfly plate is deviated from the cylinder axis of the body while the position of the double eccentric valve stem is eccentric. That is to say, after the third eccentricity, the sealing section of the disc is no longer a true circle, but an ellipse. The biggest feature of the triple offset butterfly valve is that the sealing structure is fundamentally changed. It is no longer a position seal, but a torsion seal; it does not rely on the elastic deformation of the valve seat, but completely relies on the contact surface pressure of the valve seat to achieve the sealing effect.

The butterfly valve opening and closing part is a disc-shaped butterfly plate, which rotates around its own axis in the valve body, so that the valve that can open, close or adjust is called a butterfly valve. The butterfly valve is usually less than 90 degrees from fully open to fully closed. The butterfly valve and the butterfly stem have no self-locking ability. In order to locate the butterfly plate, a worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate have self-locking ability, so that the butterfly plate can stop at any position, but also improve the operation performance of the valve.   1. Features of high performance triple eccentric bidirectional hard sealing butterfly valve   The valve body and valve seat of the triple offset butterfly valve are connected components, and the sealing surface layer of the valve seat is surfacing with temperature-resistant and corrosion-resistant alloy materials. The multi-layer soft stacked sealing ring is fixed on the valve plate. Compared with the traditional butterfly valve, this butterfly valve has high temperature resistance, easy operation, and no friction when opening and closing. When closing, the torque of the transmission mechanism increases to compensate the sealing, which improves the butterfly valve. The advantages of excellent sealing performance and extended service life.   The valve seat sealing ring is composed of multi-layer stainless steel sheets on both sides of the soft T-shaped sealing ring. The sealing surface of the valve plate and the valve seat is an inclined conical structure, and the temperature and corrosion resistant alloy material is surfacing on the inclined conical surface of the valve plate; the spring fixed between the adjusting ring pressure plates and the adjusting bolts on the pressure plate are assembled together. This structure effectively compensates the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under medium pressure, and solves the sealing problem of the valve during the two-way exchange of medium conveying. The sealing ring is composed of multi-layer stainless steel sheets on both sides of the soft T-shaped, which has the dual advantages of metal hard sealing and soft sealing, and has zero leakage sealing performance under low temperature and high temperature conditions.   2. Classification of butterfly valves   The types of butterfly valves can be divided into offset plate type butterfly valve, vertical plate type butterfly valve, inclined plate type butterfly valve and lever type butterfly valve according to the structure. According to the sealing form, it can be divided into two types: soft sealing butterfly valve and hard sealing butterfly valve. Soft-sealed butterfly valves are generally sealed with rubber rings, and hard-sealed butterfly valves are usually sealed with metal rings. According to the connection type, it can be divided into flange connection butterfly valve and wafer connection butterfly valve. According to the transmission mode, it can be divided into manual butterfly valve, gear transmission butterfly valve, pneumatic butterfly valve, hydraulic butterfly valve and electric butterfly valve.   3. Precautions for installation and maintenance of butterfly valves   (1) During installation, the valve disc should stop in the closed position.   (2) The opening position should be determined according to the rotation angle of the butterfly plate.   (3) For butterfly valves with bypass valves, the bypass valve should be opened before opening.   (4) It should be installed according to the manufacturer's installation instructions, and a firm foundation should be set for heavy butterfly valves.

The control valve consists of two main assemblies: valve body assembly and actuator assembly (or actuator system), which are divided into four series: single-seat series control valve, double-seat series control valve, sleeve series control valve and self-operated series control valve. Variations of the four types of valves can lead to many different applicable configurations, each with its own specific applications, features, advantages and disadvantages. While some control valves are used in a wider range of applications than others, control valves are not suitable for all applications to work together to create the best solution for enhanced performance and reduced cost.   1. Characteristics of control valve   (1) There are various types of control valves, and their applicable occasions are different. Therefore, the type of control valve should be reasonably selected according to the requirements of the technological production process.   (2) Pneumatic control valves are divided into two types: air-on and air-off. The air-to-open control valve is closed in a fault state, and the air-to-close control valve is opened in a fault state. Some auxiliary equipment can be used to form a retaining valve or make the control valve self-locking, that is, the control valve maintains the valve opening before the failure when the fault occurs.   (3) The way of air opening and air closing can be realized by the combination of positive and negative actuator types and positive and negative valves. When using a valve positioner, it can also be realized by a valve positioner.   (4) Various control valves have different structures and have their own characteristics.   2. Type of control valve   There are many types of valve bodies for control valves. Common control valve types include straight-through single-seat, straight-through double-seat, angle, diaphragm, small flow, three-way, eccentric rotation, butterfly, sleeve, spherical, etc. When making specific choices, consider the following:   (1) It is mainly considered according to the selected flow characteristics and unbalanced force.   (2) When the fluid medium is a suspension containing a high concentration of abrasive particles, the internal material of the valve should be hard.   (3) Since the medium is corrosive, try to choose a valve with a simple structure.   (4) When the temperature and pressure of the medium are high and the change is large, the material of the valve core and the valve seat should be selected with a small change in temperature and pressure.   (5) Flash evaporation and cavitation only occur in liquid media. In the actual production process, flashing and cavitation will form vibration and noise, which will shorten the service life of the valve. Therefore, the valve should be prevented from flashing and cavitation when selecting the valve.   3. Application of control valve   The hydraulic water level control valve has the function of automatically opening and closing the valve pipeline to control the water level. It is suitable for the automatic water supply system of various water towers (pools) in industrial and mining enterprises and civil buildings, and can be used as a circulating water supply control valve for atmospheric boilers. The valve is small in size, easy installation, high activation sensitivity, small head loss, no water hammer phenomenon, controlled by small floating balls can greatly improve the utilization rate of the water tower, for the newly built water tower, due to the reduction in the volume of the floating ball, the upper part of the water tower is left for the floating ball to float freely, and the required height is reduced to reduce the cost of the water tower to overcome the disadvantages of the old screw float valve, such as large size, easy damage, low working pressure, and a large amount of overflow.

Chemical valves are an important accessory for fluid control on industrial pipelines. Faced with various working conditions of complex industrial systems and a wide variety of valves, if you want to choose a suitable valve for the pipeline system, you should firstly understand the performance of the valve, and secondly, the steps and basis for selecting valves should be mastered. Third, the principles of selecting valves for petroleum and chemical industries should be followed.   Chemical valves not only have a wide range of applications, but also have a large amount of use. Of course, chemical valves have higher requirements than ordinary valves. The media generally used in chemical valves are relatively easy to corrode. From simple chlor-alkali industry to large petrochemical enterprises, there are high temperature, high pressure, corrosion resistance, wear resistance, and large temperature and pressure difference. For this kind of valve used in a more dangerous environment, it should be strictly implemented in accordance with chemical standards in the selection and use process. Geko flow control technology is a professional chemical valve manufacturer, and its products are manufactured in strict accordance with chemical standards.   1. How to choose chemical valve?   The chemical industry generally chooses a straight-through valve with a small flow resistance. It is usually used as a valve for closing and opening the medium. The valve that is easy to adjust the flow is used for controlling the flow. The plug valve and ball valve are more suitable for reversing and shunting. , the sliding of the closing member along the sealing surface with a wiping effect is most suitable for the medium with suspended particles. Common chemical valves include ball valves, gate valves, globe valves, safety valves, plug valves, check valves, etc. The mainstream of chemical valve media contains chemical substances, and there are many acid-base corrosive media. The manufacturers of chemical valve materials are mainly 304L and 316. For ordinary media, 304 is selected as the main material, and the corrosive fluids combined with various chemical substances are made of alloy steel or fluorine-lined.   2. The role of chemical valve types   (1) Open and close type: cut off or dredge the flow of fluid in the pipe.   (2) Adjustment type: adjust the flow and flow rate in the pipe.   (3) Throttling type: a large pressure drop occurs after the fluid passes through the valve.   (4) Other types: automatic opening and closing; maintaining a certain pressure; blocking steam and drainage.   3. Precautions before using chemical valves   (1) Whether there are blisters, cracks and other defects on the inner and outer surfaces of the chemical valve.   (2) Whether the connection between the valve seat and the valve body of the chemical valve is firm, whether the valve core and the valve seat match, and whether the sealing surface is defective.   (3) Whether the connection between the valve stem and the valve core of the chemical valve is flexible and reliable, whether the valve stem is bent, and whether the thread is damaged.

1. The function of the check valve is to ensure that the fluid flows in one direction   The moving parts usually press against the valve seat to form a seal. A small pressure must be applied to the moving parts to open the valve. Once opened, fluid power is generated to open or increase the valve opening. Fluid flow must stop before the valve will close. The fluid dynamics created by the fluid flow prevent all valves from closing. A spring may or may not be used to control the opening and assist in closing. Some check valves rely on gravity alone to provide the closing force. Valves that rely on gravity must be installed according to valve manufacturers' instructions. If horizontal pipes are specified, then the slope of a short distance local pipe must be changed.   Swing check valves are powered by gravity. As the valve opens, the force required to control the opening of the valve increases. If the balance between disc weight and fluid dynamic forces is incorrect, the valve will not fully open. Increasing the flow rate may cause unexpected corrosion or erosion damage, so gravity-driven valves must meet operating conditions.   When the valve is fully open, the disc or piston travel must be limited by a stop. A valve that is fully open, but not restrained, is susceptible to vibration. Vibration can cause rapid wear of the ammonium chain pins or piston. Valves using springs may experience early spring failure (caused by fatigue). Vibration may be caused by eddies or disturbances. When the fluid has some viscosity, fluid damping can restrain vibration. Valves using springs may be configured with springs of varying stiffness. This can be an effective vibration damper if the full travel stop includes squeezing to prevent rebound after a quick start.   2. The different designs of the check valve are to better play its role   Squeeze includes a seat and plate or piston design that prevents the check valve valve from slamming shut. The addition of extra material on the seat creates two squeeze areas. Try to squeeze fluid out of these areas, slowing down the valve during the snap shut. But there is a price to be paid for this. The increased area of limited clearance is an ideal site for collecting small solid particles. Controlled shut-off squeezing force protection can cause further problems due to collected solids unless there is a sufficient squeezing gap to eject the solids. Fragile solids such as coal may be crushed with a narrow seal. The squeeze area tends to expand the effective seat width and reduce the valve's ability to crush solids. This effect must be taken into account, taking into account all relevant solid properties. Ball valves often have very narrow seats and may scavenge solids for more efficient seating.   Vibration problems may be limited to small valves. When the valve is larger, the inertia of the moving parts increases. The increased inertia may effectively damp vibrations and result in a delayed shutdown after reverse flow has begun. Damping of the valve seat becomes very important. For all valves, the flow path area must be checked and flow rates calculated for design operating conditions. Disc and piston area are as important as primary orifice area. Smaller runner areas are susceptible to corrosion and cavitation wear can occur. For specific functions, the valve body of the check valve may include auxiliary connections, such as vents and drains. Valves for thermal applications may sometimes have a bypass valve to allow the system to warm up at low flow rates.

Ball valve and gate valve are the same type of valve, the difference is that its closing part is a sphere, and the sphere rotates around the center line of the valve body to achieve opening and closing. Ball valves are mainly used to cut off, distribute and change the flow direction of the medium in the pipeline.   Ⅰ. Flange ball valve, new type of valve that is widely used, has the following advantages:   1. The fluid resistance is small, and its resistance coefficient is equal to the pipe section of the same length.   2. Simple structure, small size and light weight.   3. Tight and reliable, the sealing surface material of the ball valve is widely used in plastic, and the sealing performance is good, and it has also been widely used in vacuum systems.   4. The Flange ball valve is easy to operate, opens and closes quickly, and only needs to rotate 90° from fully open to fully closed, which is convenient for long-distance control.   5. The maintenance is convenient, the ball valve has a simple structure, the sealing ring is generally movable, and it is more convenient to disassemble and replace.   6. When fully open or fully closed, the sealing surfaces of the ball and the valve seat are isolated from the medium, and when the medium passes through, it will not cause erosion of the valve sealing surface.   7. It has a wide range of applications, with a diameter ranging from a few millimeters to a few meters, and can be applied from high vacuum to high pressure. This type of valve should generally be installed horizontally in the pipeline.   Ⅱ. The working principle of flange ball valve   1. The opening process   (1) In the closed position, the ball is pressed against the valve seat by the mechanical pressure of the valve stem.   (2) When the handwheel is turned counterclockwise, the valve stem moves in the opposite direction, and the angular plane at the bottom makes the ball disengage from the valve seat.   (3) The valve stem continues to lift and interacts with the guide pin in the helical groove of the valve stem, so that the ball begins to rotate without friction.   (4) Until it reaches the fully open position, the flange ball valve stem is lifted to the limit position, and the ball rotates to the fully open position.   2. The closing process   (1) When closing, rotate the handwheel clockwise, the valve stem starts to descend and the ball leaves the valve seat and starts to rotate.   (2) Continue to rotate the handwheel, the valve stem is acted by the guide pin embedded in the upper spiral groove, so that the valve stem and the ball rotate 90° at the same time.   (3) When it is about to close, the ball has rotated 90° without contacting the valve seat.   (4) During the last few turns of the handwheel, the angular plane at the bottom of the valve stem is mechanically wedged to compress the ball, so that it is tightly pressed on the valve seat to achieve complete sealing.   The ball valve can be closed tightly with only a 90-degree rotation operation and a small torque. The completely equal valve body cavity provides a low resistance, straight-through flow path for the medium. It is generally believed that ball valves are most suitable for direct opening and closing, but recent developments have designed ball valves so that they can be used for throttling and flow control. The main feature of the flange ball valve is its compact structure, easy operation and maintenance, suitable for general working media such as water, solvent, acid and natural gas, but also suitable for media with harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body can be integral or combined.

According to different use requirements, there are many types of control valves, which can be divided into straight stroke and angular stroke according to the way the valve core moves; Diverter three-way control valve, confluence three-way control valve, diaphragm valve, etc.; can be divided into on-off type, integral type and proportional type according to the action law; Close the valve. Only a few commonly used control valves are briefly introduced here.   1. Straight-through single-seat control valve   The straight-through single-seat control valve type has only one valve core and one valve seat in the valve body, simple structure, small leakage (even completely cut off), small allowable pressure difference, suitable for clean media requiring small leakage and small working pressure difference the occasion. In the application, special attention should be paid to the allowable pressure difference to prevent the valve from closing.   2. Straight-through double-seat control valve   The straight-through double-seat control valve has two valve cores and valve seats in the valve body. Because the force of the fluid on the upper and lower spools can cancel each other, the straight-through double-seat control valve has the characteristics of large allowable pressure difference, and the upper and lower spools are not easy to close at the same time, so the leakage is large. It is suitable for clean medium occasions with large pressure difference between both ends of the valve and low leakage requirements, but not suitable for high viscosity and fiber-containing occasions.   3. Angle control valve   The valve body of the angle control valve is a right angle, with a simple flow path and low resistance. It is suitable for the control of high pressure difference, high viscosity, suspended solids and granular substances. Angle control valve is generally suitable for bottom in and side out. At this time, the control valve has good stability. In the case of high pressure difference, in order to prolong the service life of the valve core, side in and bottom out can also be used. However, the side in and the bottom out are prone to shock when the opening is made. Angle valves are also suitable for applications where process piping is right-angle piping.   4. Three-way control valve   The valve body of the three-way control valve has three connecting ports, which are suitable for the pipeline control system of the fluid in three directions, and are mostly used for temperature adjustment, ratio adjustment and bypass adjustment of heat exchangers. In use, it should be noted that the fluid temperature difference should not be too large, usually less than 150 °C, otherwise the three-way control valve will be deformed due to large stress, resulting in leakage or damage to the connection. There are two types of three-way control valve: confluence three-way valve and split three-way control valve. The confluent three-way control valve has two input ports for the medium. After flowing in and mixing, it flows out through an outlet; the split three-way control valve is for the medium to flow in from an inlet, and it is divided into two outlets to flow out.

The control valve is the actuator in the automatic control system, and its application quality is directly reflected in the adjustment quality of the system. As a terminal element in process control, people have a newer understanding of its importance than in the past. The quality of the control valve application, in addition to the quality of the product itself, whether the user is correctly installed, used, and maintained, it is very important to calculate and select correctly. Due to the error of calculation and selection, the system starts and stops, and some even cannot be used. Therefore, users and system designers should recognize the importance of valves on site, and must pay enough attention to the selection of control valves.   The control valve has the characteristics of simple structure and reliable action, but because it is in direct contact with the process medium, its performance directly affects the quality of the system and environmental pollution, so the control valve must be regularly maintained and repaired, especially for harsh and important operating conditions. On occasion, more attention should be paid to maintenance work of inspection sites.   1. Maintenance of the inner wall of the control valve   For control valves used in high pressure difference and corrosive media, the valve body wall and the diaphragm of the diaphragm valve are often impacted and corroded by the medium, and the pressure and corrosion resistance must be checked.   2. Maintenance of control valve seat   When the control valve is working, due to the infiltration of the medium, the inner surface of the thread used for fixing the valve seat is easily corroded and the valve seat is loosened, so attention should be paid during inspection. For valves that work under high pressure difference, it is also necessary to check whether the sealing surface of the valve seat is damaged.   3. Maintenance of control valve spool   The valve core is a movable part during adjustment work, and it is most seriously eroded and corroded by the medium. During maintenance, it is necessary to carefully check whether the various parts of the valve core are corroded and worn, especially in the case of high pressure difference. The wear of the valve core is more serious. (Due to cavitation), attention should be paid. When the valve core is seriously damaged, it should be replaced. In addition, attention should be paid to whether the valve stem also has a similar phenomenon, or the connection with the valve core is loose.   4. Maintenance of control valve diaphragm   "O" rings and other gaskets. Check whether the diaphragm and "O"-shaped gasket in the control valve are aging and cracked.   5. Maintenance of control valve sealing packing   Pay attention to whether the PTFE packing and sealing grease are aging, and whether the mating surface is damaged, and should be replaced when necessary.   The control valve is the main type of actuator, which changes the fluid flow by power operation by receiving the control signal output by the regulating control unit. Control valves generally consist of actuators and valves. According to the power used by its equipped actuator, the control valve can be divided into three types: pneumatic, electric and hydraulic, namely the pneumatic control valve using compressed air as the power source, the electric control valve using electricity as the power source, and the liquid medium (such as oil) pressure-driven hydraulic control valve, in addition, according to its function and characteristics, there are solenoid valve, electronic, intelligent, fieldbus control valve and so on.

Stainless steel manual ball valve and gate valve are the same type of valve, the difference is that the closure is a sphere, and the sphere rotates around the center line of the valve body to reach an open and closed valve. Ball valves are mainly used for blocking, distributing and changing the moving direction of the medium in the pipeline. Stainless steel manual ball valve is a relatively new type of ball valve. It has some advantages unique to its own structure, such as no friction in the switch, not easy to wear the seal, and small opening and closing torque. This reduces the size of the fitted actuator. Equipped with multi-reversal electric actuators, it can realize the adjustment and tight interception of the medium. It is widely used in petroleum, chemical, urban water supply and drainage and other working conditions that require strict blocking.   1. Structural characteristics of stainless steel manual ball valve   (1) Friction-free opening and closing: completely solve the problem that the traditional valve affects the sealing due to the friction between the sealing surfaces.   (2) Top-loading structure: The valves installed on the pipeline can be directly inspected and repaired online, which can effectively reduce installation and parking and reduce costs. Manual ball valves should generally be installed horizontally in the pipeline.   (3) Single valve seat design: eliminates the problem that the medium in the cavity of the valve affects the safety of operation due to abnormal pressure increase.   (4) Low torque design: The valve stem with special structure design can easily open and close the valve with only a small handle.   (5) Wedge-shaped sealing structure: the valve is sealed by the mechanical force supplied by the valve stem, which presses the ball wedge onto the valve seat to seal, so that the sealing performance of the valve is not affected by the change of the pressure difference of the pipeline, and the sealing function is under various working conditions. All are guaranteed.   (6) The self-cleaning structure of the sealing surface, when the sphere tilts away from the valve seat, the fluid in the pipeline passes evenly along the sphere sealing surface at 360°, which not only eliminates the local scouring of the valve seat by the high-speed fluid, but also washes away the sealing surface. On the accumulation, to achieve the purpose of self-cleaning.   2. Principle and usage of manual ball valve   The working principle of stainless steel manual ball valve: stainless ball valve relies on rotating the valve core to dredge or block the valve. The ball valve is easy to switch, small in size, can be made into a large diameter, reliable in sealing, simple in structure, and convenient in repair.   (1) Open process   In the closed position, the ball is pressed on the valve seat by the mechanical pressure effect of the valve stem. When the handwheel is rolled counterclockwise, the valve stem moves in the opposite direction. Lift, and interact with the guide pin in the spiral groove of the valve stem, so that the ball starts to rotate without friction until it reaches the full open position, the valve stem is lifted to the limit position, and the ball rotates to the full open position.   (2) closed process   When closed, rotate the handwheel clockwise, the stem of the manual ball valve begins to descend and the ball is separated from the valve seat and begins to rotate; if the handwheel is continuously rotated, the stem is affected by the guide pin embedded in the upper spiral groove, so that the stem and the ball At the same time, it rotates 90°. When it is about to close, the ball has rotated 90° without contacting the valve seat. During the last few turns of the handwheel, the angular flat at the bottom of the valve stem mechanically wedges the ball to press it tightly against the valve seat to achieve a complete seal.

There are many different ways to classify the gate valve structure, the main difference is the different structural forms of the sealing elements used. According to the structure of the sealing element, the gate valve is often divided into several different types, and the most common gate valve types are parallel gate valve and wedge gate valve. According to the structure of the valve stem, it can also be divided into rising stem gate valve and dark stem gate valve.   1. Parallel gate valves   The two sealing surfaces of the parallel gate valve are perpendicular to the axis of the pipeline, that is, the gate valve with the two sealing surfaces parallel to each other. Among the parallel gate valves, the structure with a thrust wedge is the most common, and the parallel gate valve is suitable for low pressure, medium and small diameter valves. The spring can generate the necessary pre-compression force, which is beneficial to the sealing of the gate. In addition, there are parallel gate valves with mechanical devices (such as levers, screw mechanisms, etc.) to push the gate open, and one-way parallel gate valves with only one sealing pair. These structures are currently only used under special working conditions.   2. Wedge gate valves   The two sealing surfaces of the wedge gate valve form a certain angle with the axis of the pipeline, that is, the gate valve in which the two sealing surfaces are wedge-shaped. The size of the inclination angle mainly depends on the temperature of the medium. Generally, the higher the working temperature, the larger the angle should be to reduce the possibility of wedging of the gate when the temperature changes. In the wedge gate valve, it can be divided into double gate, single gate and elastic gate.   3. Rising stem gate valves   The valve stem nut of this kind of gate valve is set on the valve cover or bracket. When opening and closing the valve, the valve stem nut is rotated to realize the lifting and lowering of the valve stem. In this structure, the threaded part of the valve stem is not in contact with the medium, and is not easily corroded by the medium, and at the same time is beneficial to the lubrication of the threaded part of the valve stem, so it is widely used. Contact GEKO, a professional gate valve supplier, for the gate valve price.   4. Dark stem gate valves   The valve stem nut of this kind of gate valve is in direct contact with the medium in the valve body. When opening and closing the valve, it is realized by rotating the valve stem. The only advantage of this structure is that the height of the gate valve does not change when opening and closing, so the gate valve installation space is small. However, this type of valve must be equipped with an opening and closing indicator to display the opening of the valve.   At present, in petroleum and chemical systems, especially in long-distance oil and natural gas pipelines, flat gate valves with floating valve seats are widely used. This kind of flat gate valve has low fluid resistance, reliable sealing performance and long service life. This type of gate valve is divided into guide holes and without guide holes. The flat gate valve with diversion hole is mainly used in oil and natural gas pipelines to clean the pipeline, and the flat gate valve without diversion hole is suitable for opening and closing devices on various pipelines. The manufacturing process of this gate valve is relatively simple, and it is easy to realize automatic production.

The handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited. Double-gate gate valves should be installed vertically (i.e. the stem is in the vertical position and the handwheel is on top). The gate valve with the bypass valve should open the bypass valve before opening (to balance the pressure difference between the inlet and the outlet and reduce the opening force). The gate valve with transmission mechanism shall be installed according to the provisions of the product instruction manual. If the valve is used frequently, lubricate it at least once a month. The gate valve is used as a cut-off medium. When fully open, the entire flow is straight, and the pressure loss of the medium is minimal at this time. Gate valves are usually suitable for conditions that do not require frequent opening and closing, and keep the gate fully open or fully closed.   1. The gate valve is not suitable for use as regulation or throttling   For high-speed flowing media, the gate can cause vibration of the gate when it is partially opened, and the vibration may damage the sealing surface of the gate and the valve seat, and the throttling will cause the gate to be eroded by the medium. From the structural form, the main difference is the form of the sealing element used. According to the form of the sealing element, the gate valve is often divided into several globe valves types , such as: wedge gate valve, parallel gate valve, parallel double gate valve, wedge double gate gate valve, etc. The most common forms are the wedge gate valve and the parallel gate valve.   2. Matters needing attention when using the gate valve disc   The function of this type of valve is to allow the medium to flow in only one direction, and to prevent flow in one direction. Usually this kind of valve works automatically. Under the action of fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincident valve flap of the valve flap act on the valve seat, thereby cutting off the flow. Among them, the check valve belongs to this type of valve, which includes swing check valve and lift check valve. Swing check valves have a hinge mechanism and a door-like disc that rests freely against the sloping seat surface. In order to ensure that the valve disc can reach the proper position of the valve seat surface every time, the valve disc is designed in the hinge mechanism, so that the valve disc has enough swing space and makes the valve disc truly and comprehensively contact the valve seat. Discs can be made entirely of metal, or inlaid with leather, rubber, or synthetic overlays, depending on the performance requirements.   According to the conditions of use, the disc can be of all-metal structure, or it can be in the form of a rubber pad or rubber ring embedded on the disc holder. Like the globe valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow of the swing check valve is limited rare.   In the production process, in order to make the pressure, flow and other parameters of the medium meet the requirements of the technological process, it is necessary to install an adjustment mechanism to adjust the above parameters. The main working principle of the adjustment mechanism is to achieve the purpose of adjusting the above parameters by changing the flow area between the valve disc and the valve seat. These valves are collectively referred to as control valves, which are divided into self-propelled control valves that rely on the power of the medium itself, such as pressure reducing valves, pressure-stabilizing valves, etc.) is called other-driven control valve, such as electric control valve, pneumatic control valve and hydraulic control valve, etc.