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Selection criteria for check valves

July 30, 2020

Selection criteria for check valve:

The selection criteria for check valves are as follows:

double-wing-check-valve-3

1. In order to prevent the medium from flowing back, check valves should be installed on equipment, devices and pipelines;

2. Check valves are generally suitable for clean media, not for media containing solid particles and high viscosity;

3. Generally, horizontal lift check valves should be used on horizontal pipes with a nominal diameter of 50mm;

4. The straight-through lift check valve can only be installed in horizontal pipelines;

5. For the inlet pipeline of the water pump, a bottom valve should be used. The bottom valve is generally only installed on the vertical pipeline at the pump inlet, and the medium flows from bottom to top;

6. Compared with the swing type, the lifting type has better sealing performance and greater fluid resistance. The horizontal type should be installed on the horizontal pipeline, and the vertical type on the vertical pipeline;

7. The installation position of the swing check valve is not restricted. It can be installed on a horizontal, vertical or inclined pipeline. If installed on a vertical pipeline, the medium flow direction should be from bottom to top;

8. The swing check valve should not be made into a small-diameter valve, it can be made into a high working pressure, the nominal pressure can reach 42MPa, and the nominal diameter can also be large, the maximum can reach more than 2000mm. It can be applied to any working medium and any working temperature range according to the different materials of the shell and the seal. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature range of the medium is between -196–800℃;

all types of check valve and structures -code names-photos

9. The applicable occasion for swing check valve is low pressure and large diameter, and the installation occasion is restricted;

10. The installation position of the butterfly check valve is not restricted. It can be installed on a horizontal pipeline or on a vertical or inclined pipeline;

11. Diaphragm check valve is suitable for pipelines that are prone to water hammer. The diaphragm can well eliminate the water hammer caused by the backflow of the medium. It is generally used on low-pressure and normal temperature pipelines, and is especially suitable for tap water pipelines. Normal media work The temperature is between -12-120℃, and the working pressure is less than 1.6MPa, but the diaphragm check valve can achieve a larger diameter, and the maximum DN can reach more than 2000mm;

12. The spherical check valve is suitable for medium and low pressure pipelines and can be made into a large diameter;

13. The shell material of the spherical check valve can be made of stainless steel, and the hollow sphere of the seal can be wrapped with polytetrafluoroethylene engineering plastics, so it can also be applied to the pipeline of general corrosive media, and the working temperature is -101–150 ℃, its nominal pressure is ≤4.0MPa, and the nominal passage range is between DN200-DN1200;

14. When selecting a check valve for incompressible fluids, the required closing speed must be evaluated first, and the second step is to select the type of check valve that may meet the required closing speed;

15. The check valve for compressible fluid can be selected according to the similar method of check valve for incompressible fluid. If the medium flow range is large, the check valve for compressible fluid can be used A deceleration device, if the medium flow is stopped and started quickly and continuously, such as the outlet of the compressor, a lift check valve is used;

16. The corresponding size of the check valve should be determined, and the valve supplier must provide the data of the selected size, so that the valve size when the valve is fully opened at a given flow rate can be found;

17. For high and medium pressure check valves below DN50mm, vertical lift check valves and straight-through lift check valves should be used;

18. For low-pressure check valves below DN50mm, butterfly check valves, vertical lift check valves and diaphragm check valves should be used;

19. For high and medium pressure check valves with DN greater than 50mm and less than 600mm, swing check valves should be used;

20. For medium and low pressure check valves with DN greater than 200mm and less than 1200mm, wear-free spherical check valves should be used;

21. For low-pressure check valves with a DN greater than 50mm and less than 2000mm, butterfly check valves and diaphragm check valves should be used;

22. For pipelines that require relatively small water hammer impact or no water hammer when closed, slow-close swing check valves and slow-close butterfly check valves should be selected.

Process design of check valve

July 30, 2020

Process design of check valve:
(1) The quality control of the main body blank. All parts of this valve are forgings. The forging process is carried out

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in strict accordance with the forging process regulations and process cards. The initial forging temperature, final forging temperature, deformation degree and deformation speed are strictly controlled, and the process regulations stipulate The cooling method performs cooling. Chemical composition analysis, mechanical property test, intergranular corrosion test, metallographic analysis of the forged product are carried out. After analysis, test and determination, they all meet the corresponding standards.

The quality of the forgings is guaranteed by ultrasonic inspection and liquid penetration inspection. The forgings are 100% ultrasonically inspected and evaluated in accordance with RCC-M requirements, and liquid penetration inspections and evaluations are performed on all surfaces of the forgings.

(2) Welding In order to improve the quality of surfacing welding, plasma argon arc welding is used for surfacing welding of the sealing surface of the valve disc and the valve seat. At the same time, in order to ensure the welding quality, the welding process used in production was re-qualified.

(3) Assemble test High-quality products not only require high-precision components, but also how to assemble these high-precision components into high-performance products. China Nuclear Su Valve has organized an assembly and commissioning team composed of multiple technicians and senior technicians with rich experience and excellent technology. It is responsible for valve assembly, commissioning and testing. It has formulated the cleaning process and assembly process of parts and components. Strictly check and keep improving during the commissioning to ensure the successful assembly and commissioning of the valve. Various performance tests have been carried out, and all indicators meet the requirements of the design task book.

(4) Process inspection has prepared a quality plan for the valve to ensure that the valve has been quality controlled from raw materials, blank input, machining, welding, heat treatment, non-destructive testing, cleaning, assembly, factory testing and various type tests, and has been verified Recognition and on-site witness by the Second Industrial Research and Design Institute.

Butterfly double flap check valve is suitable for high-rise building water supply pipe network, pipe network with

double-wing-check-valve-3

certain chemical corrosive medium, pipe network with limited installation space, and also suitable for sewage pipe network.

The lift-type silent check valve is suitable for pipe networks with high quality requirements for water supply and drainage projects; pipe networks with relatively high pressure requirements (PN2.5Mpa); it can be installed at the outlet of the pump and is an economical and practical waterproof hammer check valve.

The lift-type silencing check valve is suitable for water supply and drainage systems and high-rise building pipe networks. It can be installed at the outlet of the pump. With a slight structural change, it can be used as a suction bottom valve, but it is not suitable for sewage pipe networks.

The horizontal check valve is suitable for diving, drainage and sewage pumps, especially for sewage and sludge

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systems.

Swing rubber check valve is suitable for domestic water pipe network; but not suitable for sewage with a lot of sediment

Swing single check valve is suitable for water supply system, petroleum, chemical industry, metallurgy and other industrial sectors. It is most suitable for places with installation space restrictions.

Installation method and precautions of check valve

July 30, 2020

Check valve installation method:
1. Swing check valve: The disc of the swing check valve is disc-shaped and rotates around the shaft of the valve seat

double-wing-check-valve-3

passage. Because the inner passage of the valve is streamlined, the flow resistance is smaller than that of the lift check valve. It is suitable for large-caliber occasions where the flow rate is low and the flow does not change frequently, but it is not suitable for pulsating flow, and its sealing performance is not as good as the lifting type. Swing check valves are divided into three types: single, double and multiple valves. These three types are mainly classified according to the valve diameter. The purpose is to prevent the medium from stopping or flowing backwards and weaken the hydraulic shock.

Silent check valve

2. Lifting check valve: a check valve whose disc slides along the vertical centerline of the valve body. The lifting check valve can only be installed on a horizontal pipeline. The disc can be used on a high-pressure small-diameter check valve. . The valve body shape of the lift check valve is the same as the stop valve (can be used in common with the stop valve), so its fluid resistance coefficient is relatively large. Its structure is similar to the stop valve, and the valve body and disc are the same as the stop valve. The upper part of the valve disc and the lower part of the valve cover are processed with guide sleeves. The disc guide can be lifted and lowered freely in the valve guide sleeve. When the medium flows downstream, the disc opens by the thrust of the medium. When the medium stops flowing, the disc depends on its own It falls on the valve seat to prevent the medium from flowing backward. The direction of the medium inlet and outlet channel of the straight-through lift check valve is perpendicular to the direction of the valve seat channel; the vertical lift check valve has the same direction of the medium inlet and outlet channels as the valve seat channel, and its flow resistance is smaller than that of the straight-through type.

3. Disc check valve: a check valve with the disc rotating around the pin shaft in the valve seat. The disc check valve has a simple structure and can only be installed on a horizontal pipeline, with poor sealing performance.

4. In-line check valve: a valve with the valve flap sliding along the centerline of the valve body. In-line check valve is a new type of valve. It is small in size, light in weight, and good in processing technology. It is one of the development directions of check valves. However, the fluid resistance coefficient is slightly larger than that of the swing check valve.

5. Compression check valve: This valve is used as a boiler feed water and steam shut-off valve. It has a comprehensive function of lift check valve and stop valve or angle valve.

In addition, there are some check valves that are not suitable for pump outlet installation, such as bottom valve, spring type, Y type, etc.

Precautions
1. Do not allow the check valve to bear weight in the piping system. Large check valves should be independently supported so that they are not affected by the pressure generated by the piping system.

2. When installing, pay attention to the direction of medium flow should be consistent with the direction of the arrow marked on the valve body.

3. Lifting vertical flap check valve should be installed on the vertical pipeline.

4. Lifting horizontal flap check valve should be installed on the horizontal pipeline.

Classification of check valves

July 30, 2020

Classification of check valves:
The check valve that opens or closes by the force of the medium flow to prevent the medium from flowing back is

tilting disc swing check valve (6)

called a check valve. Check valves belong to the category of automatic valves, which are mainly used in pipelines where the medium flows in one direction, and only allow the medium to flow in one direction to prevent accidents.

Classified by structure:
According to the structure, it can be divided into three types: lift check valve, swing check valve and butterfly check valve:

1. Lift check valves are divided into two types: vertical and horizontal.

2. The swing check valve is divided into three types: single, double and multiple.

3. The butterfly check valve is straight-through.

The above-mentioned check valves can be divided into four types in connection form: threaded connection, flange connection, welding connection and wafer connection.

Classified by material:
1. Cast iron check valve

2. Brass check valve

3. Stainless steel check valve

4. Carbon steel check valve

5. Forged steel check valve

Classified by function:
1. DRVZ silent check valve

Stainless steel check valve
Stainless steel check valve
2. DRVG silent check valve

3.NRVR silent check valve

4. SFCV rubber flap check valve

5.DDCV double disc check valve

Tanghai Valve is the best manufacturer of check valve in China. We produce the best quality products with competitive low prices. Main products: butterfly valve, lug type butterfly valve, wafer type butterfly valve, U-type butterfly valve, double flange butterfly valve, gate valves, check valves, globe valves, valve parts (Valve body, Valve disc, Valve shaft, Valve seat…)

Check valve and its working principle

July 30, 2020

What is check valve?

Check valve refers to a valve whose opening and closing parts are circular discs and rely on its own weight and medium pressure to generate actions to block the back flow of the medium. It is an automatic valve, also called check valve, one-way valve, return valve or isolation valve. The movement of the disc is divided into lift check valve and swing check valve. The lift check valve is similar in structure to the stop valve, but lacks the valve stem to drive the valve disc. The medium flows in from the inlet end (lower side) and flows out from the outlet end (upper side). When the inlet pressure is greater than the sum of the weight of the disc and its flow resistance, the valve is opened. On the contrary, the valve is closed when the medium flows back. The swing check valve has a disc that is incline

tilting disc check valve body (2)

d and can rotate around the axis, and its working principle is similar to that of the lift check valve. The check valve is often used as the bottom valve of the pumping device to prevent the backflow of water. The combination of check valve and stop valve can play a role of safety isolation. The disadvantage is that the resistance is large and the sealing performance is poor when closed.

Working principle of check valve:
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).

The function of this type of valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of the fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve flap act on the valve seat, thereby cutting off the flow.

Among them, check valves belong to this type of valve, which includes swing check valves and lift check valves. The swing check valve has a hinge mechanism and a valve flap like a door that rests freely on the inclined valve seat surface. In order to ensure that the valve clack can reach the proper position of the valve seat surface every time, the valve clack is designed in a hinge mechanism so that the valve clack has enough space for rotation and makes the valve clack truly and comprehensively contact the valve seat. The valve clack can be made of metal, or inlaid with leather, rubber, or synthetic covering, depending on the performance requirements. When the swing check valve is fully opened, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except that the disc can be raised and lowered freely, the rest of the valve is like a shut-off valve. The fluid pressure lifts the disc from the seat sealing surface, and the backflow of the medium causes the disc to fall back to the seat and cut off the flow. According to the conditions of use, the valve disc can be an all-metal structure, or it can be in the form of a rubber pad or a rubber ring inlaid on the disc holder. Like a shut-off 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 the swing check valve, and the flow rate of the swing check valve is restricted.

Detailed introduction of soft sealing butterfly valve-(3)

July 28, 2020

Features of soft sealing butterfly valve:

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

1. Small and light, easy to disassemble and repair, and can be installed in any position.

2. The structure is simple and compact, the operating torque is small, and the 90-degree rotation opens quickly.

3. The flow characteristics tend to be straight, and the regulation performance is good.

4. The connection between the butterfly plate and the valve stem adopts a pinless structure, which overcomes possible internal leakage points.

5. The seal can be replaced, and the seal is reliable to achieve two-way sealing.

6. The butterfly plate can be sprayed with a coating layer, such as nylon or PTFE, according to user requirements.

7. The valve can be designed as flange connection and wafer connection.

8. The driving mode can be manual, electric or pneumatic.

Problems in the use of soft sealing butterfly valves:

1. Due to the principle of the triple eccentric structure, the sealing between the sealing surface of the valve plate and the valve seat is to press the valve plate against the valve seat by the torque of the transmission device. In the state of positive flow, the higher the medium pressure, the tighter the sealing extrusion. When the flow channel medium flows back, as the medium pressure increases, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal begins to leak.

2. Due to structural conditions, this structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.

3. Since the multilayer soft and hard stacked sealing ring is fixed on the valve plate, when the valve plate is normally open, the medium will wash its sealing surface positively, and the soft sealing tape in the metal sheet sandwich will directly affect the sealing performance after being washed.

high-performance soft sealing butterfly valve, characterized in that: the valve seat sealing ring is composed of multiple layers of 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 of an oblique cone structure, and the oblique cone surface of the valve plate is welded with temperature-resistant and corrosion-resistant alloy materials; the spring fixed between the adjusting ring pressure plate and the adjusting bolt of the pressure plate are assembled together. This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the two-way interchangeable medium conveying process.

The sealing ring is composed of a soft T-shaped multi-layer stainless steel sheet on both sides, which has the dual advantages of metal hard and soft sealing. It has zero leakage sealing performance regardless of low temperature and high temperature. The test proves that in the positive flow state of the pool (the flow direction of the medium is the same as the rotation direction of the butterfly plate), the pressure of the sealing surface is produced by the torque of the transmission device and the action of the medium pressure on the valve plate. When the positive medium pressure increases, the tighter the oblique cone surface of the valve plate and the sealing surface of the valve seat are pressed, the better the sealing effect.

Therefore, unlike the prior art, the utility model does not install a soft and hard multilayer sealing ring on the valve plate, but directly installs it on the valve body. Adding an adjustment ring between the pressure plate and the valve seat is a very ideal two-way hard sealing method. . It can replace gate valves and ball valves.

In the reverse flow state, the seal between the valve plate and the valve seat is pressed against the valve seat by the torque of the driving device. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the adjusting ring after being loaded compensates for the tight pressure of the sealing surface of the valve plate and the valve seat Play the role of automatic compensation.

Detailed introduction of soft sealing butterfly valve-(2)

July 28, 2020

There are many types of soft-sealed butterfly valves, which can be divided into the following categories according to different forms:
Classified by structure
Classified by structure

(1) Center sealing butterfly valve

(2) Single eccentric sealed coal valve

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

(3) Double eccentric sealing butterfly valve

(4) Triple eccentric seal valve

Classified according to the sealing surface material:

(1) Soft sealing butterfly valve.

1) The sealing pair is composed of non-metallic soft material to non-metallic soft material.

2) The sealing pair is composed of a metal hard material and a non-metal soft material.

(2) Metal hard seal butterfly valve. The sealing pair is composed of a metal hard material to a metal hard material.

Classified according to the sealing form:

(1) Forced sealing butterfly valve

1) Elastic sealing butterfly valve. The specific pressure of the seal is generated by the valve plate squeezing the valve seat when the valve is closed, and the elasticity of the valve seat or valve plate

2) External torque sealing butterfly valve. The seal specific pressure is generated by the torque applied to the valve shaft

(2) Pressurized sealing butterfly valve. The specific sealing pressure is generated by the pressure of the elastic sealing element on the valve seat or valve plate

(3) Automatic sealing butterfly valve. The sealing specific pressure is automatically generated by the medium pressure.

Classified by work pressure:

(1) Vacuum butterfly valve. Butterfly valves whose working pressure is lower than the atmospheric pressure of the standard reactor.

(2) Low pressure butterfly valve. Butterfly valve with nominal pressure PN<1.6MPa.

(3) Medium pressure butterfly valve. Butterfly valve with nominal pressure PN of 2.5-6. 4MPa.

(4) High pressure butterfly valve. A butterfly valve with a nominal pressure PN of 10.0-80.0MPa.

(5) Ultra-high pressure butterfly valve. Butterfly valve with nominal pressure PN>100MPa.

Classified by working temperature:

(1) High temperature butterfly valve. t>450 C butterfly valve

(2) Medium temperature butterfly valve. 120 C＜t＜450 C butterfly valve

(3) Normal temperature butterfly valve. One 40C<t<; 120 C butterfly valve

(4) Cryogenic butterfly valve. One 100＜t＜一40 C butterfly valve

(E) Ultra-low temperature butterfly valve. t＜一100 C butterfly valve

Classified according to the connection method:

(1) Wafer butterfly valve

(2) flange butterfly valve

(3) lug butterfly valve

(4) Welded butterfly valve

Detailed introduction of soft sealing butterfly valve-(1)

July 28, 2020

The butterfly plate of the soft sealing butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical passage of the butterfly valve body, the

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When the rotation reaches 90°, the valve is fully opened. The characteristics of the new type of high-life stainless steel butterfly valve and the problem of the butterfly valve during use, this type of valve should generally be installed horizontally in the pipeline.

Problems in use of soft sealing butterfly valve:
1. Since the multi-layer soft and hard stacked sealing ring is fixed on the valve plate, when the valve plate is normally open, the medium will wash its sealing surface positively, and the soft sealing tape in the metal sheet sandwich will directly affect the sealing performance after being washed.

2. Due to structural conditions, this structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate is too thick and the flow resistance is large.

3. Due to the principle of the triple eccentric structure, the seal between the sealing surface of the valve plate and the valve seat depends on the torque of the transmission device to press the valve plate against the valve seat. In the state of positive flow, the higher the medium pressure, the tighter the sealing extrusion. When the flow channel medium flows back, as the medium pressure increases, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal begins to leak.

high-performance soft sealing butterfly valve, characterized in that: the valve seat sealing ring is composed of multiple layers of 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 of oblique cone structure, and the temperature and corrosion resistant alloy material is built up on the oblique cone surface of the valve plate; the spring fixed between the pressure plate of the adjusting ring and the adjusting bolt of the pressure plate are assembled together. This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the two-way interchangeable medium conveying process.

The sealing ring is composed of a soft T-shaped multi-layer stainless steel sheet on both sides, which has the dual advantages of metal hard and soft sealing. It has zero leakage sealing performance regardless of low temperature and high temperature. The test proves that in the positive flow state of the pool (the flow direction of the medium is the same as the rotation direction of the butterfly plate), the pressure of the sealing surface is produced by the torque of the transmission device and the action of the medium pressure on the valve plate. When the positive medium pressure increases, the tighter the oblique cone surface of the valve plate and the sealing surface of the valve seat are pressed, the better the sealing effect.

In the reverse flow state, the seal between the valve plate and the valve seat is pressed against the valve seat by the torque of the driving device. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the adjusting ring after being loaded compensates for the tight pressure of the sealing surface of the valve plate and the valve seat Play the role of automatic compensation.

Therefore, unlike the prior art, the utility model does not install a soft and hard multilayer sealing ring on the valve plate, but directly installs it on the valve body. Adding an adjustment ring between the pressure plate and the valve seat is a very ideal two-way hard sealing method. . It can replace gate valves and globe valves

Difference between Soft seal gate valve and hard seal gate valve

July 28, 2020

Soft seal gate valve and hard seal gate valve are two major categories in the gate valve series. Hard seal and soft seal can sometimes compensate for each other, and

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sometimes they are independent of each other. So what is the relationship between soft seal gate valve and hard seal gate valve? What are the main differences? Next, the editor of Tanghai Valve will solve these mysteries for everyone.

1. Sealing material

Soft seal gate valve: the seal pair is made of metal materials on one side and elastic non-metallic materials on the other side, which is called “soft seal”. This kind of seal has good sealing performance, but it is not resistant to high temperature, easy to wear, and has poor mechanical properties.

Hard seal gate valve: The two sides of the seal pair are made of metal materials or other harder materials are called “hard seals”. This kind of seal has poor sealing performance, but has high temperature resistance, abrasion resistance and good mechanical properties.

2. Structure mechanism

The hard seal gate valve is a seal between metal and metal, and the sealing ball and valve seat are both metal. Machining accuracy and craftsmanship are more difficult, and are generally used in high pressure, usually above 35MPa. The soft seal gate valve is a seal between metal and non-metal, such as nylon\tetrafluoroethylene, and the manufacturing standards are the same.

3. Equipment selection

The selection of soft and hard seal gate valves is mainly based on the process medium, temperature and pressure. Generally, the medium contains solid particles or wears or the temperature is higher than 200 degrees. It is best to use hard seals. Valves with a diameter greater than 50 have a larger pressure difference and consider opening the valve torque. , When the torque is large, the fixed hard-seal ball valve should be selected, and its sealing level can reach 6 regardless of the soft or hard seal.

3. Conditions of use

The soft seal gate valve generally has a very high seal, while the hard seal can be high or low according to the requirements; the soft seal needs to be fireproof, because the material of the soft seal will leak at high temperatures, while the hard seal does not have this problem; Seals can generally be made at very high pressures, but soft seals cannot; soft seals cannot be used in some situations due to the problem of the flowing medium. Finally, hard seal valves are generally more expensive than soft seals. As for manufacturing, there is little difference between the two, mainly the difference between the valve seat, the soft seal is non-metallic, and the hard seal is metallic.

Through the above introduction, I believe everyone can understand the difference between soft seal gate valve and hard seal gate valve. With the continuous development of China’s industrial market, it is necessary to understand the difference between soft seal gate valve and hard seal gate valve, which may not only affect Production efficiency may also greatly affect economic efficiency

Difference between soft seal butterfly valve and hard seal butterfly valve

July 28, 2020

The difference between soft seal butterfly valve and hard seal butterfly valve:

A butterfly valve hard seal refers to a “hard seal” in which both sides of the seal pair are made of metal materials or other harder materials. This kind of seal has poor

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

sealing performance, but high temperature resistance, wear resistance, and good mechanical properties. For example, : Steel + Steel; Steel + Copper; Steel + Graphite; Steel + Alloy Steel; (The steel here may also be cast iron, cast steel, alloy steel or surfacing, sprayed alloy).

The soft seal seal pair is made of metal materials on one side and elastic non-metallic materials on the other side. It is called “soft seal”. This kind of seal has better sealing performance, but it is not resistant to high temperatures, easy to wear, and mechanical Poor performance. Such as: steel + rubber; steel + tetrafluoropolyethylene; etc. The soft sealing seat is made of non-metallic materials with certain strength, hardness and temperature resistance, with good sealing performance, zero leakage, but life And the adaptability to temperature is relatively poor. The hard seal is made of metal, and the sealing performance is relatively poor, although some manufacturers claim that it can achieve zero leakage. The soft seal cannot meet the process requirements for some corrosive materials, and the hard seal can solve it! These two types of seals can complement each other. In terms of tightness, the soft seal is relatively good, but now the tightness of the hard seal can also meet the corresponding requirements! The advantage of the soft seal is good sealing performance, but the disadvantage is that it is easy to age, wear, and has a short service life. The hard seal has a long service life, but the tightness is relatively worse than that of the soft seal.

The main differences in its structure are as follows
1. The difference in structure

Soft seal butterfly valves are mostly centerline type, and hard seals are mostly single eccentric, double eccentric, and triple eccentric butterfly valves.

2. Temperature resistance

The soft seal is used in normal temperature environment. Hard seal can be used in low temperature, normal temperature, high temperature and other environments

3. Pressure

Soft seal low pressure-normal pressure, hard seal can also be used in medium and high pressure conditions

4. Sealing performance: The soft sealing and triple eccentric hard sealing butterfly valves have better sealing performance. The triple eccentric butterfly valve can maintain good sealing under high pressure and high temperature environment.

In view of the above characteristics, the soft sealing butterfly valve is suitable for the two-way opening and closing and adjustment of ventilation and dust removal pipelines, water treatment, light industry, petroleum, chemical and other industries. Hard-sealed butterfly valves are mostly used in heating, gas, gas, oil, acid and alkali environments.

With the widespread use of butterfly valves, its features of convenient installation, convenient maintenance and simple structure become more and more obvious. Electric soft-sealed butterfly valves, pneumatic soft-sealed butterfly valves, hard-sealed butterfly valves, etc. have begun to replace electric gate valves and globe valves in more and more occasions.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife 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

Selection criteria for check valves

Process design of check valve

Installation method and precautions of check valve

Classification of check valves

Check valve and its working principle

Detailed introduction of soft sealing butterfly valve-(3)

Detailed introduction of soft sealing butterfly valve-(2)

Detailed introduction of soft sealing butterfly valve-(1)

Difference between Soft seal gate valve and hard seal gate valve

Difference between soft seal butterfly valve and hard seal butterfly valve

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