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Materials, installation and features of vertical check valve

July 31, 2020

Part materials of vertical check valve:
Construction and installation points for vertical check valve:

1) The installation position, height, and direction of inlet and outlet must meet the design requirements. Note that

silent check valve (9)

the direction of medium flow should be consistent with the direction of the arrow marked on the valve body, and the connection should be firm and tight.

2) Visual inspection must be carried out before the valve is installed. The nameplate of the valve should comply with the current national standard “General Valve Marking” GB 12220. For valves with a working pressure greater than 1.0 MPa and a cut-off function on the main pipe, the strength and tightness performance test should be carried out before installation, and the valve can be used only after it is qualified. During the strength test, the test pressure is 1.5 times the nominal pressure and the duration is not less than 5 minutes. The valve housing and packing should be qualified without leakage. During the tightness test, the test pressure is 1.1 times the nominal pressure; the duration of the test meets the requirements of GB 50243

Part name: material

Valve body, bonnet, valve clap with Part Material: Carbon Steel

Valve surface Sealing: with Part Material: Weld overlay hard alloy.

Valve shaft: Carbon steel

Shaft Pins: Chrome stainless steel

Gasket: flexible graphite + SS304

Install and use of vertical check valve:
1. Both ends of the valve passage must be blocked and there is a dry and ventilated room. If it is stored for a long time, it should be checked frequently to prevent corrosion.

2. The valve should be cleaned before installation and the defects caused during transportation should be eliminated.

3. When installing, you must carefully check whether the signs and nameplates on the valve meet the requirements for use.

4. The valve is installed on the vertical pipeline.

main feature of vertical check valve:
Vertical check valve has the following two advantages:

1. The three-dimensional check valve is divided into flange and wafer, which has the characteristics of simple structure, few parts and light weight. Vertical check valves are mainly used in various working conditions that need to prevent medium backflow.

2. When the vertical check valve is used for vertical installation, no spring is required, and the weight of the valve flap and the pressure of the fluid return flow are used for check.

Use performance and working principle of vertical check valve

July 31, 2020

Use performance of vertical check valve:

silent check valve (3)

This valve is used as a device to prevent the backflow of the medium on industrial pipelines.

Performance specifications:

Test pressure: nominal pressure (MPa) 1.6 / 2.5 / 4.0; 150Lb-900Lb

Shell test: 2.4/ 3.8 / 6.0; psig425-psig3250

Seal test: 1.8 /2.8/ 4.4; psig300-psig2400

Body material: WCB(C) /CF8(P) /CF 8M (R) /WC6 /WC9; 20#,A105

Working temperature: ≤ 425 / ≤ 100 /≤ 100/ ≤ 550 /≤ 550;

Applicable medium: water, steam, oil, nitric acid, acetic acid,

Executive standard: Design and manufacture: GB12235, AP!6D, BS “Structural length: GB12221, ASME/ANSI16.10, API6D” connection flange: JB/T79-1994, GB/9113, ASME/ANSI16.5, API605

Test and inspection: JB/T9092-1999, API598, API6D

lifting check valve (4)

Principle of action of vertical check valve:
During the use of this valve, the medium flows in the direction of the arrow shown in the figure.

1. 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 sealing surface of the valve flap and the valve seat is sealed due to the weight of the valve flap and the action of the reverse force of the medium. Close together to achieve the purpose of preventing the medium from flowing backward.

2. The sealing surface of the valve body and valve clack adopts stainless steel surfacing welding.

3. The structural length of this valve is in accordance with the regulations of GB12221-1989, and the flange connection dimensions are in accordance with the regulations of JB/T79-1994.

Stainless steel vertical check valve

July 31, 2020

Overview of Stainless steel vertical check valve:

H42W stainless steel flanged vertical check valve is a valve whose disc slides along the center line of the valve body. Pipeline vertical check valve is a new type of valve. It has the characteristics of simple structure, few parts, light weight, and good manufacturability. It is one of the development direc

lifting check valve (4)

tions of check valves. However, the fluid resistance coefficient is slightly larger than that of the swing check valve. Vertical check valves are widely used in various pipelines that need to prevent the medium from flowing back in the petroleum, chemical, pharmaceutical, and power industries. H42H can be equipped with spring or no spring according to vertical installation or horizontal installation.

Stainless steel vertical check valve H42W flange vertical check valve working principle:

H42W series vertical check valve can prevent the medium from flowing back and play the role of medium check. H42W stainless steel vertical check valve is open when the medium pressure at the inlet end is higher than the outlet end. Because under the pressure of the medium at the inlet end of the pipeline, the valve clack in the vertical check valve is pushed up to automatically open the valve. When the medium pressure at the inlet end is lower than the outlet end, the spring pushes the disc toward the valve seat to close the valve. Under the pressure, it will automatically close.

Industry development prospects of check valve

July 30, 2020

China’s check valve industry chain is numerous, but it is not a powerful valve country. Generally speaking, my

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country has entered the ranks of the world’s valve powers, but in terms of product quality, there is still a long gap between my country and the valve powers. The industry’s low concentration of production, low R&D capabilities for high-end products, and low manufacturing technology in the valve industry still exist, and the import and export trade deficit continues to expand.

The next few years will be a period of high-speed shock in the valve industry. The direct consequence of this high-speed shock is the expansion of the polarization trend in the valve cabinet brand camp. It is expected that there will not be so many valve companies that can really survive on the market in the next few years. But this kind of high-speed shock in the valve industry will bring huge opportunities, and the result of the shock will make the market operation more rational.

The road to localization of high-end valves is extremely bumpy. Basic parts have become a shortcoming restricting the development of my country’s manufacturing industry towards high-end. During the 12th Five-Year Plan period, the government will continue to increase the localization of high-end equipment parts. Here we select several representative valves in key development industries mentioned in the “Implementation Plan” for the feasibility

double-wing-check-valve-3

analysis of import substitution. From the analysis, we can see that the feasibility of valve import substitution in various sub-sectors is very different, and high-end valves urgently need more policy guidance and scientific research support.

The valve industry plays a very important role in the development of the national economy as an important part of preparing for the manufacturing industry. As there is still a certain gap between the level of China’s domestic valve manufacturing industry and the international advanced level, many key valves with high parameters, high temperature and pressure, and high pounds have been dependent on imports. In order to promote the localization of valves, the State Council issued the “About Accelerating Revitalization After the “Several Opinions on the Equipment Manufacturing Industry”, the relevant state departments have made a series of major deployments in accordance with the country’s requirements for the localization of major equipment. The National Development and Reform Commission led the China Machinery Industry Federation and the China General Machinery Industry Association. Deployed and formulated valve localization plans for major equipment in related fields, and coordinated with relevant departments many times. Nowadays, valve localization has reached a consensus in the domestic valve industry.

Actively adopt international standards for product design; absorb foreign excellent design structures; product testing and performance inspection are carried out in strict accordance with international standards; absorb foreign production process experience and focus on the research and promotion of new materials; understand the technology of imported high-parameter valve products Parameters and working conditions are the ways to speed up the process of localization, promote the continuous update of valve products, and fully realize the localization of valves.

With the acceleration of the restructuring of the valve industry, the future industry will be a competition between valve product quality and safety and product brands. Products will develop in the direction of high technology, high parameters, strong corrosion resistance, and long life. Only through continuous technological innovation, development New products and technological transformation can gradually improve the technical level of products, meet the needs of domestic equipment, and fully realize the localization of valves. Under the huge demand environment, my country’s valve manufacturing industry is bound to present a better development prospect.

Troubleshooting of check valve

July 30, 2020

Troubleshooting of check valve:

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1. The disc is broken
The reasons that cause the valve disc to break are:

The pressure of the medium before and after the check valve is close to balance and they are “see-saw” each other. The valve disc often beats against the valve seat, and the disc made of some brittle materials (such as cast iron, brass, etc.) is broken.

The preventive method is to use a check valve whose disc is a flexible material.

2. Medium backflow
The reasons for the backflow of the medium are:

①The sealing surface is damaged; ②Insert impurities.

Repairing the sealing surface and cleaning impurities can prevent backflow.

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

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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

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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.

Posts

Materials, installation and features of vertical check valve

Use performance and working principle of vertical check valve

Stainless steel vertical check valve

Industry development prospects of check valve

Troubleshooting of check valve

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

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