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What is butt welding? (4)- flash butt welding

2. Resistance and heating of flash butt welding

The contact resistance Rc during flash butt welding is the total resistance of the liquid metal lintel between the end faces of the two workpieces, and its size depends on the number of lintels and their cross-sectional area at the same time. The latter two are related to the cross-sectional area of ​​the workpiece, the current density and the

flash butt welding-schematic diagram

flash butt welding-schematic diagram

approach speed of the two workpieces. With the increase of these three, the number of lintels and their cross-sectional area simultaneously existing increases, and Rc will decrease.

The Rc of flash butt welding is much larger than that of resistance butt welding, and it exists throughout the flashing stage. Although its resistance value gradually decreases, it is always greater than the internal resistance of the workpiece. Rc does not disappear completely until the upsetting starts. Figure 14-5 shows the general law of Rc, 2Rω and R changes during flash butt welding. The gradual decrease in Rc is due to the increase in the approach speed of the workpiece as the end surface temperature increases during the flashing process, and the number and size of the lintels increase accordingly.

Because Rc is large and there is the entire flashing stage, the heating of the joint during flash butt welding mainly depends on Rc.

Three, flash butt welding welding cycle, process parameters and workpiece preparation

1, welding cycle

The welding cycle of flash butt welding is shown in 14-7, and the reset time in the figure refers to the time from loosening the workpiece to returning to the original position. There are two preheating methods: resistance preheating and flashing preheating. The figure (b) uses resistance preheating.

2, process parameters

The main parameters of flash butt welding are: extension length, flash current, flash flow, flash speed, upsetting flow, upsetting speed, upsetting pressure, upsetting current, clamping force, etc. Figure 14-8 is a schematic diagram of each flow rate and extension length of continuous flash butt welding. The following describes the influence of various process parameters on welding quality and the principles of selection:

(1) Elongation length l0 is the same as resistance butt welding, l0 affects the temperature distribution along the axial direction of the workpiece and the plastic deformation of the joint. In addition, with the increase of l0, the impedance of the welding circuit increases, and the required power also increases. Under normal circumstances, bar and thick arm tube l0=(0.7-1.0)d, d is the diameter of the round bar or the side length of the square bar.

For thin plates (δ=1-4mm), in order not to lose stability during upsetting, generally l0=(4-5)δ.

When different metals are butt welded, in order to make the temperature distribution on the two workpieces consistent, usually the metal with poor electrical and thermal conductivity should be smaller. Table 1 is the l0 reference value for flash butt welding of different metals.

(2) The flash current If and the upsetting current Iu If depend on the cross-sectional area of ​​the workpiece and the current density jf required for the flash. The size of jf is related to the physical properties of the welded metal, flashing speed, the area and shape of the workpiece section, and the heating state of the end surface. In the flashing process, as vf gradually increases and contact resistance Rc gradually decreases, jf will increase. During the upsetting, Rc disappears quickly, and the current will increase sharply to the upsetting current Iu. When welding large-section steel parts, in order to increase the heating depth of the workpiece, a smaller flash speed should be used, and the average jf used generally does not exceed 5A/mm2. Table 2 shows the reference values ​​of jf and ju for flash butt welding of workpieces with a cross-sectional area of ​​200-1000mm2.

The magnitude of the current depends on the no-load voltage U20 of the welding transformer. Therefore, in actual production, the secondary no-load voltage is generally given. When selecting U20, in addition to considering the impedance of the welder circuit, when the impedance is large, U20 should be increased accordingly. When welding large-section workpieces, the method of adjusting the secondary voltage in stages is sometimes used. At the beginning, a higher U20 is used to excite the flash, and then it is reduced to an adaptive value.

(3) Flash flow rate δf The flash flow rate should be selected so that there is a molten metal layer on the end of the workpiece at the end of the flash, and the plastic deformation temperature is reached at a certain depth. If δf is too small, the above requirements cannot be met, which will affect the welding quality. If δf is too large, it will waste metal materials and reduce productivity. When choosing δf, you should also consider whether there is preheating, because the δf of preheating flash butt welding can be 30-50% smaller than continuous flash butt welding.

What is butt welding? (1)

Butt resistance welding (hereinafter referred to as butt welding) is a type of resistance welding method that uses resistance heat to weld two workpieces along the entire end surface at the same time. Butt welding has high

welding

welding

productivity and easy automation, so it is widely used.
Application of butt welding:
Butt welding has high productivity and easy automation, so it is widely used. Its application range can be summarized as follows:
(1) The length of the work piece, such as the butt welding of strip steel, profile, wire, steel bar, rail, boiler steel pipe, oil and natural gas transportation pipeline.
(2) Butt welding of annular workpieces, such as car rims and bicycles, motorcycle rims, butt welding of various chain links, etc.
(3) Assembling welding of components The simple rolling, forging, stamping or machining parts are butt-welded into complex parts to reduce costs. For example, butt welding of automobile steering shaft shell and rear axle housing, butt welding of various connecting rods and tie rods, and butt welding of special parts.
(4) Butt welding of dissimilar metals can save precious metals and improve product performance. For example, the butt welding of the working part of the tool (high-speed steel) and the tail (medium carbon steel), the butt welding of the head (heat-resistant steel) and the tail (structural steel) of the exhaust valve of an internal combustion engine, the butt welding of aluminum and copper conductive joints, etc. .
Classification of butt welding:
Butt welding is divided into resistance butt welding and flash butt welding.
Resistance butt welding
Resistance butt welding is a method in which the end faces of the two workpieces are always pressed tightly, heated to a plastic state by resistance heat, and then upset pressure is quickly applied (or no upset pressure is applied and only the pressure during welding is maintained) to complete the welding.
One, resistance and heating of resistance butt welding
The resistance distribution during butt welding is shown in the figure. The total resistance can be expressed by the following formula:
R=2Rω+RC+2Reω
where Rω-the internal resistance of the conductive part of a workpiece (Ω);
Rc–the contact resistance between two workpieces (Ω);
Rω–The contact resistance between the workpiece and the electrode (Ω);
The contact resistance between the workpiece and the electrode is usually ignored due to its small resistance and far from the joint surface.
The internal resistance of the workpiece is proportional to the resistivity ρ of the welded metal and the length l0 of the workpiece extending from the electrode, and inversely proportional to the cross-sectional area s of the workpiece.
Same as spot welding, the contact resistance of resistance butt welding depends on the surface condition, temperature and pressure of the contact surface. When the contact resistance has obvious oxides or other stolen goods, the contact resistance is large. The increase in temperature or pressure will reduce the contact resistance due to the increase in the actual contact area. At the beginning of welding, the current density at the contact point is very large; after the end surface temperature rises rapidly, the contact resistance decreases sharply. When heated to a certain temperature (steel 600 degrees, aluminum alloy 350 degrees), the contact resistance disappears completely.
Like spot welding, the heat source during butt welding is also the resistance heat generated by the resistance of the welding zone. In resistance butt welding, the contact resistance exists for a very short time, and the heat generated is less than 10-15% of the total heat. But because this part of the heat is generated in a very narrow area near the contact surface. Therefore, the temperature in this area will increase rapidly, and the internal resistance will increase rapidly. Even if the contact resistance disappears completely, the heat generation intensity in this area is still higher than other places.
The harder the welding rod used (that is, the larger the current and the shorter the energization time), the smaller the pressing force of the workpiece, and the more obvious the influence of contact resistance on heating.

Product features and advantages of ball valve

Product features of ball valve:
1. The three-way ball valve adopts an integrated structure in structure, with a four-sided valve seat sealing type, fewer flange connections, high reliability, and a lightweight design.

ball valve (8)

ball valve (8)

2. The three-way ball core is divided into T type and L type, with long service life, large circulation capacity and low resistance.

3. The ball valve is divided into two types: single-acting and double-acting according to the action type. The single-acting type is characterized in that once the power source fails, the ball valve will be in the state required by the control system.

Advantages of ball valve:

1. The fluid resistance is small, and its resistance coefficient is equal to that of a pipe section of the same length.

2. Simple structure, small size and light weight.

3. It is tight and reliable, and the sealing surface material of the ball valve is widely used in plastics and has good sealing performance. It has also been widely used in vacuum systems.

4. It is easy to operate and open and close quickly. It only needs to rotate 90° from fully open to fully closed, which is convenient for remote control.

5. The maintenance is convenient, the structure of the ball valve is simple, the sealing ring is generally movable, and it is convenient to disassemble and replace.

6. It has a wide range of applications, with a diameter ranging from a few millimeters to a few meters, and can be applied in high vacuum or high pressure.

This type of valve is a high-pressure ball valve commonly used in existing mines. It bears high pressure and adopts a U-shaped card quick connection method. It can be quickly installed and disassembled in the daily production and use of the mine, and is convenient to use.

The ash unloading ball valve is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. The ash unloading ball valve can be divided into floating ball type, fixed ball type, and elastic ball type. The ash unloading ball valve is mainly used to cut off or connect the medium in the pipeline. It can also be used for fluid adjustment and control. The ash unloading ball valve Compared with other valve types, it has angular stroke output torque, opens quickly, is stable and reliable, and is widely applicable. The working principle of the ash unloading ball valve is to make the valve unblocked or blocked by rotating the valve.

Electric ball valve structure is composed of only a few parts, saving data; small size, light weight, small installation size, electric ball valve structure diagram, small driving torque, pressure regulating valve, easy and agile operation, only need to rotate 90° Fast opening and closing; and also has a good flow regulation effect and sealing characteristics at the same time, in the application of large and medium caliber, medium and low pressure, electric ball valve is the dominant valve form. When the electric ball valve is in the fully open position, the thickness of the butterfly plate is the resistance when the medium flows through the valve body, so the pressure drop that occurs through the valve is small, so it has better flow control characteristics. Electric ball valves have two sealing types: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be embedded in the valve body or attached to the periphery of the butterfly plate. Valves with metal seals generally have a longer life than valves with elastic seals, but it is difficult to achieve a complete seal. Metal seals can adapt to higher operating temperatures, while elastic seals have the disadvantage of being limited by temperature. If the electric ball valve is requested to be used as a flow control, it is important to accurately select the size and type of the valve. The construction principle of the electric ball valve is particularly suitable for manufacturing large diameter valves. Electric ball valves are not only widely used in general industries such as petroleum, gas, chemical, and water disposal, but also used in cooling water systems of thermal power stations. Commonly used electric ball valves include wafer type electric ball valves and flange type electric ball valves. Wafer type electric ball valve uses double-head bolts to connect the valve between two pipe flanges. Flange type electric ball valve is equipped with flanges on the valve. The two flanges on the valve are connected to the pipe flanges with bolts. The strength performance of the valve refers to the ability of the valve to withstand medium pressure. The valve is a mechanical product that is subjected to internal pressure, so it must have sufficient strength and rigidity to ensure long-term use without cracking or deformation. Pneumatic ball valve is composed of ball valve and pneumatic actuator. Pneumatic actuator is divided into double-acting pneumatic actuator and single-acting pneumatic actuator. Through solenoid valve control, ball valve switching action is realized. The pneumatic ball valve can realize intelligent control, quickly open or close the pipeline, and can effectively control and manage the pipe network.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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What is a ball valve?;
Electric ball valve principle | Electric ball valve working principle;
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Advantages and disadvantages of butterfly valve and structure diagram;

Classification and characteristics of ball valve

There are different ways of classification of ball valves.

Function classification:
1. Bypass valve: The ball valve is generally opened by static water, so the bypass valve is set to be pressed first, that is, both sides are filled with water;

ball valve (6)

ball valve (6)

2. Air valve: when filling with water, the buoy will automatically close the valve when the air is removed; when draining, the buoy will drop by itself when it is used for replenishing air;

3. Pressure relief valve: When opening and closing the valve, remove the pressure water between the valve and the sealing cover to avoid wearing the sealing cover;

4. Drain valve: drain the sewage in the lower part of the ball shell.

Transmission classification:
1. Pneumatic ball valve

2. Electric ball valve

3. Hydraulic ball valve

4. Pneumatic hydraulic ball valve

5. Electro-hydraulic ball valve

6. Turbine drive ball valve

Classification characteristics of ball valve:

Ball valves are divided into: floating ball valve, fixed ball valve, orbital ball valve, V-shaped ball valve, three-way ball valve, stainless steel ball valve, cast steel ball valve, forged steel ball valve, ash unloading ball valve, anti-sulfur ball valve, pneumatic ball valve, electric ball valve, card sleeve Ball valves, welded ball valves.

Classified by shell/body material, ball valves can be divided into:

1. Metal material valves: such as carbon steel valves, alloy steel valves, stainless steel valves, cast iron valves, titanium alloy valves, Monel valves, copper alloy valves, aluminum alloy valves, lead alloy valves, etc.

2. Metal valve body lining valves: such as rubber-lined valves, fluorine-lined valves, lead-lined valves, plastic-lined valves, and enamel-lined valves.

3. Valves of non-metallic materials: such as ceramic valves, glass valves, and plastic valves.

There are many domestic manufacturers of ball valves, and most of the connection sizes are not uniform. Mainly divided into the following categories:

The ball of the ball valve is floating. Under the action of the medium pressure, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure that the outlet end is sealed.

Structural features of ball valve:
The sealing performance is good, but all the load of the sphere bearing the working medium is transmitted to the outlet sealing ring. Therefore, it is necessary to consider whether the sealing ring material can withstand the working load of the sphere medium. When subjected to higher pressure impact, the sphere may deviate . This structure is generally used for medium and low pressure ball valves.

The ball of the ball valve is fixed and does not move when pressed. The fixed ball valve is equipped with a floating valve seat. After receiving the pressure of the medium, the valve seat will move, so that the sealing ring is pressed tightly on the ball to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, and the operating torque is small, which is suitable for high pressure and large diameter valves.

In order to reduce the operating torque of the ball valve and increase the reliability of the seal, an oil-sealed ball valve has appeared, which not only injects a special lubricant between the sealing surfaces to form a layer of oil film, which enhances the sealing performance and reduces the operating torque. Suitable for high pressure and large diameter ball valves.

Flexible features of ball valve:

The ball of the ball valve is elastic. Both the ball and the valve seat sealing ring are made of metal materials, and the sealing specific pressure is very large. The pressure of the medium itself cannot meet the sealing requirements, and external force must be applied. This valve is suitable for high temperature and high pressure media.

The elastic sphere is made by opening an elastic groove on the lower end of the inner wall of the sphere to obtain elasticity. When closing the passage, use the wedge-shaped head of the valve stem to expand the ball and press the valve seat to seal. Loosen the wedge-shaped head before rotating the sphere, and the sphere will return to its original shape, so that there is a small gap between the sphere and the valve seat, which can reduce the friction and operating torque of the sealing surface.

Qv347, Qv647, Qv947 V-type regulating ball valve

The Qv347, Qv647, and Qv947 V-type regulating ball valves have a shearing effect on the valve seat because the ball core has a V-shaped structure. Therefore, it is suitable for the control of relevant process parameters in the suspension medium containing fibers or small solid particles in papermaking, chemical, metallurgical and other industrial enterprises. It is especially suitable for the pulp, white water, black liquor and white water in the pulp and paper production process. Automatic adjustment of the fluid of suspended particles such as liquid and thick and turbid slurry fluid medium.

This V-shaped ball valve is a fixed ball valve and also a single-seat sealed ball valve. The adjustment performance is the best among ball valves, the flow characteristics are equal percentages, and the adjustable ratio is 100:1. It has a shearing effect between the V-shaped incision and the metal valve seat, which is especially suitable for media containing fibers, small solid particles, slurry, etc.

Three-way ball valve has T type and L type. The T type can connect three orthogonal pipelines with each other and cut off the third channel, which can split and merge. The L-shape can only connect two orthogonal pipelines, and cannot maintain the third pipeline to communicate with each other at the same time. It only plays a role of distribution.

Characteristics of ball valve

Features of ball valve:
1. Wear resistance; because the valve core of the hard-sealed ball valve is spray-welded alloy steel,

ball valve (2)

ball valve (2)

The sealing ring is made of alloy steel surfacing, so the hard sealing ball valve will not produce too much wear when opening and closing. (Its hardness coefficient is 65-70):

Second, the sealing performance is good; because the sealing of the hard-seal ball valve is manually ground, it can be used until the valve core and the sealing ring are completely matched. So his sealing performance is reliable.

3. The switch is light; since the bottom of the sealing ring of the hard-sealed ball valve adopts a spring to make the sealing ring and the valve core tightly hug together, the switch is very light when the external force exceeds the preload of the spring.

4. Long service life: It has been widely used in petroleum, chemical industry, power generation, papermaking, atomic energy, aviation, rockets and other departments, as well as people’s daily life.

The pneumatic ball valve has a simple and compact structure, reliable sealing, and convenient maintenance. The sealing surface and the spherical surface are always in a closed state, which is not easy to be eroded by the medium. It is easy to operate and maintain. It is suitable for general working media such as water, solvent, acid and natural gas. It is mainly used for cutting off. Or connect the medium in the pipeline, and can also be used for fluid adjustment and control.

Compared with other types of valves, pneumatic ball valves have angular stroke output torque, quick opening, stable and reliable, wide application, and the following advantages:

1. The thrust bearing reduces the friction torque of the valve stem, which can make the valve stem operate smoothly and flexibly for a long time.

2. Anti-static function: a spring is set between the ball, valve stem and valve body, which can lead out the static electricity generated during the switching process.

3. Since materials such as polytetrafluoroethylene have good self-lubricating properties and small friction loss with the ball, the pneumatic ball valve has a long service life.

4. Small fluid resistance: Pneumatic ball valves have the smallest fluid resistance among all valve categories. Even the reduced diameter pneumatic ball valves have relatively small fluid resistance.

5. Reliable valve stem sealing: Since the valve stem only rotates and does not move up and down, the packing seal of the valve stem is not easy to be damaged, and the sealing ability increases with the increase of the medium pressure.

6. Good sealing performance of the valve seat: The sealing ring made of elastic materials such as polytetrafluoroethylene is easy to seal in structure, and the valve sealing capacity of the pneumatic ball valve increases with the increase of the medium pressure.

7. The fluid resistance is small, and the full-bore ball valve basically has no flow resistance.

8. Simple structure, small size and light weight.

9. Close and reliable. It has two sealing surfaces, and the sealing surface materials of the ball valve are widely used in various plastics, which have good sealing performance and can achieve complete sealing. It has also been widely used in vacuum systems.

10. Convenient operation, rapid opening and closing, only need to rotate 90° from fully open to fully closed, which is convenient for remote control.

11. Convenient maintenance, simple structure of the ball valve, generally movable sealing ring, easy to disassemble and replace.

12. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium. When the medium passes, it will not cause erosion of the valve sealing surface.

13. 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.

14. Because the ball valve has wiping properties during opening and closing, it can be used in media with suspended solid particles.

15. The processing precision is high, the cost is expensive, and it is not suitable for use in high temperature. If there are impurities in the pipeline, it is easy to be blocked by the impurities, causing the valve to fail to open.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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Characteristics and working principle of electric globe valve;
What is a ball valve?
Electric ball valve principle | Electric ball valve working principle;
The advantages and disadvantages of butterfly valves;

Characteristics and working principle of electric globe valve

Features of electric globe valve:

  • The fluid resistance is small, and its resistance coefficient is equal to that of a pipe section of the same length.

    Globe valve (9)

    Globe valve (9)

  • Simple structure, small size and light weight. Electric globe valve
  • It is tight and reliable. The sealing surface material of the gate valve is widely used plastic, and it has good sealing performance. It has also been widely used in vacuum systems.
  • It is easy to operate and open and close quickly. It only needs to rotate 90° from fully open to fully closed, which is convenient for remote control.
  • The maintenance is convenient, the gate valve has a simple structure, the sealing ring is generally movable, and it is convenient to disassemble and replace.
  • When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium will not cause erosion of the valve sealing surface when the medium passes.
  • 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.

Electric globe valve classification:

According to its channel position, it can be divided into straight-through type and right-angle type.

Working principle of electric globe valve:

The working principle of the electric shut-off valve is to make the valve unblocked or blocked by rotating the valve. The gate valve switch is light, small in size, can be made into a large diameter, reliable in sealing, simple in structure, convenient in maintenance, the sealing surface and the spherical surface are often closed, and it is not easy to be eroded by the medium. It is widely used in various industries.

A. Opening process of globe check valve:

  • In the closed position, the valve body is pressed against the valve seat by the mechanical pressure of the valve stem.
  • When the hand wheel is turned counterclockwise, the valve stem moves in the opposite direction, and the angular plane at the bottom causes the ball to separate from the valve seat.
  • The valve stem continues to lift and interacts with the guide pin in the spiral groove of the valve stem, so that the ball begins to rotate without friction.
  • Until it reaches the fully open position, the valve stem is raised to the limit position, and the ball rotates to the fully open position.

B. Closing process of electric globe valve:

  • When closing, turn the handwheel clockwise, the valve stem begins to drop and the ball leaves the valve seat to start rotating.
  • Continue to rotate the hand wheel, and the valve stem will be acted on by the guide pin embedded in the upper spiral groove to make the valve stem and the gate rotate 90° at the same time.
  • When it is about to close, the gate body has rotated 90° without contact with the valve seat.
  • In the last few turns of the handwheel, the angular plane at the bottom of the valve stem mechanically wedges and presses the sphere to make it tightly press on the valve seat to achieve a complete seal.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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The working principle and characteristics of the globe valve

The globe valve is a tool that relies on the pressure of the valve stem to make the sealing surface of the disc and the sealing surface of the valve seat tightly fit to prevent the flow of the medium. It is a forced sealing valve and is one of the most widely used valves.

According to the direction of the passage, the globe valve is divided into four types: straight-through globe valve, direct-flow globe valve, angle globe valve and plunger globe valve.
1. Working principle of globe valve:

Globe valve (9)

Globe valve (9)

The stop valve, also called the cut-off valve, is one of the most widely used valves. The reason why it is popular is that the friction between the sealing surfaces is small during the opening and closing process, which is relatively durable, has a small opening height, and is easy to manufacture. , Easy maintenance, not only suitable for medium and low pressure, but also suitable for high pressure. The closing principle of the shut-off valve is to rely on the pressure of the valve stem to make the sealing surface of the disc and the sealing surface of the valve seat closely fit, preventing the flow of the medium. Our country’s valve “Sanhua” once stipulated that the flow direction of the stop valve should be from top to bottom, so there is directionality when installing. The structural length of the shut-off valve is longer than that of the gate valve, and the fluid resistance is large, and the sealing reliability is not strong during long-term operation.

As one of the most important cut-off valves, the globe valve plays an important role in the aerospace field. As an important component of aerospace equipment, the shut-off valve realizes the functions of medium transportation, cut-off, and adjustment, and its sealing performance directly affects the safe and reliable operation of aerospace equipment. Studying the influencing factors and influencing rules of the sealing characteristics of typical globe valves has guiding significance for the structural design of the valve sealing pair, thereby improving the sealing performance and reliability of the valve.

2. Globe valve characteristics:

The valve plays an important role in cutting off and throttling the medium in the pipeline. As an extremely important cut-off valve, the valve is sealed by applying a torque to the valve stem, and the valve stem is in the axial direction. The valve clack applies pressure to make the sealing surface of the valve clack closely fit the sealing surface of the valve seat, and prevent the medium from leaking along the gap between the sealing surfaces.

The sealing pair of the globe valve is composed of a valve flap sealing surface and a valve seat sealing surface, and the valve stem drives the valve flap to move vertically along the center line of the valve seat. During the opening and closing process of the globe valve, the opening height is small, the flow is easy to adjust, and the manufacturing and maintenance are convenient, and the pressure application range is wide.

Compared with another commonly used shut-off valve in industrial production, an alarm valve, the shut-off valve is simpler than the former in terms of structure, and is easy to manufacture and maintain. In terms of service life, the sealing surface of the globe valve is not easy to wear and scratch. During the opening and closing process of the valve, there is no relative sliding between the valve disc and the sealing surface of the seat, so the wear and abrasion of the sealing surface are small, so the sealing is improved. During the full closing process of the auxiliary service life stop valve, the disc stroke is small, and its height is relatively small compared to the alarm valve. The shortcoming of the globe valve is that the opening and closing torque is large and it is difficult to achieve rapid opening and closing. Because the flow passage in the valve body is relatively tortuous, the fluid flow resistance is large, and the fluid power is lost in the pipeline.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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Features and working principle of silent check valve

Silent check valve refers to a valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing back. It is also called check valve, one-way valve, silence check valve, reverse flow valve, and back pressure valve. Check valve is a kind of automatic valve, its main function is to prevent the back flow of the medium, prevent the pump and drive motor from reversing, and discharge the container medium. Check valves can also be used to supply pipelines for auxiliary systems whose pressure may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).
Features of silent check valve:
1. The valve clack adopts a “bullet” shape design, and the valve body adopts a “waist drum” shape design to improve the flow direction of the medium and reduce the flow resistance coefficient.

2. The valve adopts a short structure. Although the head loss is slightly larger than that of the lift-type silent check valve, it is small in size and inexpensive.

3. Compact structure, non-metallic lubrication sleeve is installed between the guide shaft and the guide frame, and the valve flap can be raised and lowered flexibly without locking phenomenon.

4. The skeleton type rubber sealing ring is directly embedded in the valve body, which avoids the direct erosion of the sealing ring by the medium for a long time, and the service life is si

silent check valve (11)

silent check valve (11)

gnificantly prolonged, and it is strong and durable.

5. The valve flap has a short opening and closing stroke, which can effectively prevent water hammer

6. It is suitable for water supply and drainage system and high-rise building pipe network. It can be installed at the outlet of the pump. The structure is slightly modified, and it can be used as a suction bottom valve, but it is not suitable for sewage pipe network.

7. It has small size, light weight, low fluid resistance, fatigue resistance and long life
working principle of silent check valve:
When the medium flows in the specified direction, the valve flap is opened by the force of the medium; when the medium flows backward, the valve flap is tightly closed with the sealing surface of the valve seat due to the weight of the valve flap and the opposing force of the medium. Closed to achieve the purpose of preventing the backflow of the medium.

Check valve is an automatic valve, its main function is to prevent the back flow of the medium, prevent the pump and drive motor from reversing, and the release of the container medium. Check valves can also be used to supply pipelines for auxiliary systems whose pressure may rise above the system pressure.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Related news /knowledge:
Introduction of cast steel lift swing check valve;
The difference between globe valve and check valve;
Working principle diagram of lift check valve;

structure and characteristics of U type flange butterfly valve

Introduction of U type flange butterfly valve:
The face-to-face structure of U type flange butterfly valve is shorter than that of double flanged butterfly valve. U-shaped flange butterfly valve is widely used in

U-type flange butterfly valve, ductile iron, DI, center line,

U-type flange butterfly valve, ductile iron, DI, center line,

petroleum, chemical, electric power, metallurgy, food, medicine, textile, papermaking and other industries. It can be installed at a temperature of ≤425℃, and the medium is gas, air, steam, water, sea water, Industrial pipe networks such as oil products are used to adjust flow and cut off media.

U-shaped flange butterfly valve drive forms include manual, worm gear, pneumatic, hydraulic, electric, electro-hydraulic linkage and other actuators, which can realize remote control and automatic operation. The structure of the U-shaped flange butterfly valve adopts the principle of three-dimensional knitting design, and the valve seat adopts a multi-level structure compatible with hard and soft sealing, exquisite processing and advanced technology.

Composition and design principle of U type flange butterfly valve:
This product is composed of main components such as valve body, butterfly plate, multi-level valve seat, valve stem and transmission mechanism. Therefore, it is widely used in metallurgy, electric power, petroleum, chemical industry, air, gas, combustible gas, water supply and drainage and other corrosive media pipelines.

Because the U-shaped flange butterfly valve adopts the three-dimensional eccentric principle design, the space motion trajectory of the sealing surface is idealized. There is no friction and interference between the sealing surfaces, and the sealing material is selected properly, so that the sealing performance of the butterfly valve can be improved. Corrosion resistance, high temperature resistance and wear resistance are reliably guaranteed.

Features of U type flange butterfly valve:
The main features of U-shaped flange butterfly valve are:

1. The opening torque is small, flexible and convenient, labor-saving and energy-saving.

2. The three-dimensional knitting core structure makes the butterfly plate tighter and tighter, and its sealing performance is reliable and leak-free.

3. High pressure resistance, corrosion resistance, wear resistance, long service life, etc.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Related news /knowledge: Introduction of U-shaped flange butterfly valve; Pneumatic U-shaped flange butterfly valve.

Uses and characteristics of manual butterfly valve (4)

Installation and maintenance of manual butterfly valve:
During installation, the disc should stop in the closed position. The opening position should be determined according to the rotation angle of the butterfly plate. For

wafer type butterfly valve, with handle (13)

wafer type butterfly valve, with handle (13)

the butterfly valve with bypass valve, the bypass valve should be opened before opening, and the installation should be carried out according to the manufacturer’s installation instructions. The heavy butterfly valve should be set with a firm foundation.

Comparison of ordinary butterfly valve and gate valve:

Which of the ordinary butterfly valve or gate valve with the same nominal pressure and nominal diameter has better tightness and is not easy to leak?

The airtightness of the gate valve is better than that of the butterfly valve, but there are also manufacturers’ butterfly valves that have better airtightness. This type of valve should generally be installed horizontally in the pipeline.

The gate valve is large in size and takes up a lot of space.

The butterfly valve is small in size and takes up little space.

When selecting, the temperature of the medium, the sealing of the valve and the packing must also be considered.

The specification stipulates that butterfly valves with a nominal diameter greater than 50 are used.

The elastic metal sealing butterfly valve is a national key new product. The high-performance manual butterfly valve adopts a double eccentric and a special oblique cone oval sealing structure. It solves the shortcoming of the traditional eccentric butterfly valve that the sealing surface is still in sliding contact friction at the moment of opening and closing 0°~10°, and the sealing surface of the butterfly plate is separated at the moment of opening, and the effect of sealing when the contact is closed is achieved. Good purpose.

Material of manual butterfly valve:
1. Valve body material: gray cast iron, ductile iron, cast steel, aluminum alloy, stainless steel, etc.;

2. Valve plate material: duplex stainless steel, nylon 11 plate, galvanized plate, aluminum bronze;

3. Valve seat material: nitrile rubber, EPDM, fluorine rubber, silicone rubber, PTFE.

Ranges of application for manual butterfly valve:
It is widely used in the pipelines of petroleum, chemical, food, medicine, papermaking, hydropower, shipbuilding, water supply and drainage, metallurgy, oil, energy and other systems. It is suitable for a variety of corrosive gases, liquids, semi-liquid and solid powder media.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

related news /knowledge: Uses and characteristics of manual butterfly valve (3); Uses and characteristics of manual butterfly valve (2); Uses and characteristics of manual butterfly valve (1); Installation requirements for manual butterfly valves.