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The role of check valve and installation matters

The check valve is an automatic valve that relies on the pressure of the flow of the medium to achieve the opening and closing of the valve flap. The check valve is mainly used to prevent the medium from flowing back and backflow, so it is also called a check valve, a one-way valve and so on. Check valve is a kind of automatic valve, its function is to prevent the back flow of the medium, prevent the pump and drive motor from reversing, as well as the release of the container medium. This article will explain the function of the check valve and the precautions for installation.

The role of the check valve

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

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

The check valve is mainly used in the pump water supply system to prevent the impact of the high-pressure water backflow on the pump impeller. When the water pump in the water supply system of the water pump suddenly stops running, the pressure in the pump disappears instantly, and the high-pressure water connected to the outlet of the water pump will flow back to the water pump in the reverse direction. After the non-return valve installed at the outlet of the water pump has no medium pressure, it will be closed immediately to prevent the high-pressure water from flowing back to the pump in the reverse direction.
Imagine if there is no check valve installed at the outlet of the water pump, high-pressure water flows back to the water pump in the reverse direction, and the impeller of the water pump reverses under the impact of the high-pressure water. Under the impact of high-pressure water, the impeller may loosen or damage the impeller or other parts in a serious situation. When the pump runs again, the loose or damaged impeller can also fly out, bringing huge safety hazards to the production work.
The check valve in the hot water system is used to prevent hot water from flowing back into the pipeline. If the check valve is not installed, the hot water will flow back, which may scald the pipeline and even hurt people.

Precautions for check valve installation
1. The check valve is a one-way valve, so the installation position, height, and direction of inlet and outlet must meet the design requirements, and the direction of medium flow should be consistent with the direction of the arrow marked on the valve body.
2. Check the appearance before installing the check valve. The nameplate of the valve should meet the requirements of the current national standard “General Valve Marking” GB 12220. It can be used after all standards are qualified.
3. Do not allow the check valve in the pipeline to bear weight, especially the large check valve, which should have an independent support and not be affected by the pressure generated by 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

Related news/knowledge:
What is a single plate check valve;
The role and classification of valves;
The difference between globe valve and check valve;
The role and use of the ball valve

All types of check valve and its structures

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 known as one-way valve, non-return valve(NSV) or isolation valve. The movement of the disc is divided into lift type and swing type. The lift check valve is similar in structure to the shut-off valve, but lacks the valve stem that drives the 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 inclined and can rotate around the axis, and the 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.

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

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

The working principle of the check valve:
Check valves can also be used to supply pipelines for auxiliary systems where the 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 check 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, the check valve belongs to this type of valve, which includes swing check valve and lift check valve. The swing check valve has a hinge mechanism and a valve disc 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, leather, rubber, or synthetic covering can be inlaid on the metal, 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 valve 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 onto the seat and cut off the flow. According to the conditions of use, the valve clack can be an all-metal structure, or it can be in the form of a rubber pad or a rubber ring inlaid on the valve clack frame. 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 that of the swing check valve, and the flow rate of the swing check valve is restricted. Rarely.
Classification of check valves:
The valve that opens or closes on its own by the force of the flow of the medium to prevent the medium from flowing back is 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 a straight-through type.

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

The selection criteria of the check valve are as follows:

1. In order to prevent the medium from flowing back, check valves should be installed on the 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 inlet of the pump, 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 flow direction of the medium 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. According to the different materials of the shell and the sealing parts, it can be applied to any working medium and any working temperature range. The medium is water, steam, gas, corrosive medium, oil, medicine, etc. The working temperature range of the medium is between -196–800℃;

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 eliminate the water hammer caused by the reverse flow 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 plastic, so it can also be applied to the pipeline of general corrosive media, and the working temperature is -101–150 Between ℃, its nominal pressure is ≤4.0MPa, and the nominal passage range is between DN200-DN1200;

14. When selecting check valves 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 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-closing swing check valves and slow-closing butterfly check valves should be selected.

Types of check valves we produce:

We have other types of check valves: single-disc swing check valvedual plate check valve, tilting disc swing check valvelift swing check valvesilent check valve and ball check vlave 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,

Working principle diagram of swing check valve

Working principle diagram of swing check valve
Swing check valve, also known as check (flow) valve, is an automatic valve used on one-way flow pipelines to prevent the medium from flowing back. It depends on the pressure of the pipeline medium to open or close the valve. It can be divided into single valve type , Double valve type and multi valve type, are one of the more commonly used valves. Swing check valves are generally suitable for pipelines with relatively clean fluid media. They are not suitable for

swing-check-valve-working-principle-diagram

swing-check-valve-working-principle-diagram

working conditions with high viscosity or solid particles. Otherwise, the check valve will be insensitive to opening and cannot achieve a complete seal. The answer is not reliable enough. The swing check valve only allows the medium to flow in one direction, which can effectively prevent the medium from flowing back to prevent accidents.

The working principle of the swing check valve:
The disc of the swing check valve and the rocker are connected together, and can rotate a certain angle around the pin shaft. When the pipeline fluid flows in the specified direction (from left to right), the inlet pressure of the disc is higher than the outlet pressure. At this time, the disc is pushed away from the valve seat and rotates around the pin to a certain position, and the valve is in the open state. When the pressure difference between the two sides of the valve flap decreases to a certain level, the valve flap falls and returns to the closed state. When the fluid flows from right to left, that is, reverse flow, the pressure on the right side of the valve disc is higher than the pressure on the left side, and the force generated by the pressure difference on both sides presses the valve disc on the valve seat, and the fluid cannot pass through, the medium Can not flow back; and the greater the fluid pressure, the tighter the sealing surface is, and the better the sealing effect. To

The installation position of the swing check valve is not restricted. It can be installed horizontally in the pipeline, or on a vertical or inclined pipeline, but if it is installed on a vertical pipeline, the flow direction of the medium should be from bottom to top.

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:
Basic knowledge of valve;
What is double plate swing check valve;
Butterfly valve use principle and installation instructions;
Wafer type double disc swing check valve introduction

Working principle diagram of lift check valve

Lifting check valve structure:

Lifting check valve is a kind of valve that prevents pipeline media from flowing back, mainly composed of valve body, valve seat, valve flap, valve cover and other related parts. The lift check valve is equipped with a spring to ensure that the disc is always in a dynamic equilibrium state under the action of the spring. Regardless of the medium pressure at the inlet of the valve, the valve can maintain a balanced operation.

lift check valve Working principle diagram

lift check valve Working principle diagram

The working principle of the lift check valve:

The lift check valve has a guide rod on the disc, which can move up and down freely in the guide hole of the valve cover. When the pipeline medium flows in in the specified direction (from left to right), and the pressure below the valve flap exceeds the pressure above it, push the valve flap to rise along the center line of the guide hole of the valve cover, and the valve will automatically open to allow the medium to flow; if the fluid flows from the right to the right Left flow, that is, when it flows backward, the pressure above the valve flap is greater than the pressure below it. The pressure difference between the upper and lower pressures and the weight of the valve flap press the valve flap on the valve seat, so that the medium cannot pass through, that is, the fluid cannot flow back; and pipeline fluid The greater the pressure, the tighter the sealing surface is, and the better the sealing effect.

The seat sealing surface of the lift check valve can be welded, or it can be made into a seat sealing ring and then expanded or threaded on the valve body; when the valve body is made of stainless steel, the sealing surface can also be on the valve body It is directly processed from above. The sealing surface of the disc can be directly processed on the disc, or can be processed after surfacing or welded on the disc with the inner and outer periphery of the sealing ring. The straight-through lift check valve can only be installed on the pipeline in a balanced way, and the center line of the valve flap is vertical to the horizontal plane, while the vertical lift check valve is not subject to this restriction.

Installation attentions for valves

Precautions for valve installation:

Globe valves, throttle valves, pressure reducing valves, check valves and other valves are all directional. If the throttle valve is installed upside down, it will affect the use effect and life. If the pressure reducing valve does not work at all, if it is stopped The return valve can even cause danger.

lift-swing-check-valve-2

lift-swing-check-valve-2

Generally, the valve has a direction mark on the valve body; if not, it should be correctly identified according to the working principle of the valve.

The valve cavity of the shut-off valve is asymmetrical left and right, and the fluid must pass through the valve port from bottom to top, so that the fluid resistance is small (determined by the shape), and the opening is labor-saving (due to the upward pressure of the medium), and the medium does not press the packing after closing, which is convenient for maintenance . This is the reason why the globe valve cannot be reversed. Other valves also have their own characteristics.

The valve installation location must be convenient for operation; even if the installation is temporarily difficult, it is necessary to consider the long-term work of the operator.

It is best to keep the valve hand wheel flush with the chest (usually 1.2 meters away from the operating floor), so that opening and closing the valve is easier. The hand wheel of the floor valve should be upward, do not tilt, to avoid

Globe valve (9)

Globe valve (9)

awkward operation. The valve of the wall machine and the equipment should also leave room for the operator to stand. It is necessary to avoid operating from the sky, especially acid and alkali, toxic media, etc., otherwise it is very unsafe.

Do not install the gate valve upside down (that is, the handwheel is down), otherwise the medium will remain in the valve cover space for a long time, which will easily corrode the valve stem, and it is taboo for certain process requirements. At the same time, it is extremely inconvenient to replace the packing.

1. The pressure reducing valve should be installed upright on the horizontal pipeline, and not inclined in all directions.

2. As for the lift check valve, make sure its valve flap is vertical when installing it so that it can be lifted flexibly.

3. Swing check valve, ensure that its pin shaft is level when installing, so that it can swing flexibly.

4. Do not install the rising stem gate valve underground, otherwise the exposed stem will be corroded due to moisture.

Tianjin Tanghai Valve Manufacturing Co., Ltd. is one of the largest butterfly valve manufacturers in China, main products are butterfly valves, check valves, gate valve and globe valves. Key words:  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…)

Ball check valve introduction

Check valves are also known as counterflow valves, check valves, back pressure valves, and one-way valves. This kind of valve is automatically opened and closed by the force generated by the flow of the medium itself in the pipeline, and belongs to an automatic valve.

Uses and characteristics of ball check valve:

ball check valve (9)

ball check valve (9)

HQ44X single-ball micro-resistance ball check valve and HQ45X double-ball micro-resistance ball check valve all use rubber covered balls as the disc. Their principle is that under the action of the medium, they can roll back and forth on the slide in the valve body, thereby Play to open or close the valve. The main features of HQ44X single-ball micro-resistance ball check valve and HQ45X double-ball micro-resistance ball check valve are large flow, small flow resistance pressure loss, good sealing performance, silencing closure, and reduction of water hammer waves. It can be installed horizontally or vertically. The micro-resistance ball check valve can be used at the pump outlets of cold water, hot water, industrial and domestic sewage pipe networks to prevent the medium from flowing back. In order to prevent the medium from flowing back, check valves should be installed on equipment, devices and pipelines

Ball check valve is also called reverse valve, check valve, back pressure valve, one-way valve. This kind of valve is automatically opened and closed by the force generated by the flow of the medium itself in the pipeline, and belongs to an automatic valve. The check valve is used in the piping system, and its main function is to prevent the medium from flowing back, preventing the pump and its driving motor from reversing, and to discharge the medium in the container. Check valves can also be used to supply pipelines for auxiliary systems whose pressure may rise above the pressure of the main system.

Product advantages of ball check valve:
1. The fluid resistance is small. The ball check valve is the smallest fluid resistance of all valves. Even the reduced diameter ball valve has relatively small fluid resistance.

2. The check valve is opened and closed quickly and conveniently. As long as the valve stem rotates 90°, the ball valve completes the fully open or fully closed action, which is easy to achieve rapid opening and closing.

3. Good sealing performance. Spherical check valve seat sealing ring is generally made of elastic materials such as polytetrafluoroethylene, which is easy to ensure sealing, and the sealing force of the ball valve increases with the increase of medium pressure.

4. The valve stem is sealed reliably. The valve stem only rotates when the ball valve is opened and closed, so the packing seal of the valve stem is not easily damaged, and the sealing force of the reverse seal of the valve stem increases with the increase of medium pressure.

5. The opening and closing of the ball valve can only be rotated by 90°, so it is easy to realize automatic control and remote control. The ball valve can be equipped with pneumatic device, electric device, hydraulic device, gas-liquid linkage device or electro-hydraulic linkage device.

6. The spherical check valve channel is flat and smooth, and it is not easy to deposit media, and the pipeline can be ball-passed.

Related news /knowledge:
The difference between globe valve and check valve;
Installation instructions for ball valves;
Stainless steel valve material parameters and specific applications;

Introduction of Carbon steel lift check valve H41H-16C

H41H-16C carbon steel lift check valve (check valve) is also known as one-way valve or check valve. Its opening and

lift-swing-check-valve-2

lift-swing-check-valve-2

closing parts are opened or closed by the flow and force of the medium, and its function is to prevent the medium in the pipeline from flowing back .
check valve can be divided into three types according to the structure: lift check valve, swing check valve and butterfly check valve. Lift check valves can be divided into two types: vertical and horizontal; swing check valves are divided into three types: single, double and multiple; butterfly check valves are straight-through. The above-mentioned check valves can be divided into threaded connection, flange connection, wafer type and welding in connection form.
Attention to the installation of H41H-16C carbon steel lift check valve:
1. Do not allow the check valve to bear weight in the pipeline, and the large check valve should be independently supported so that it is not affected by the pressure generated by the pipeline 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.

The products of Tianjin Tanghai Valve Manufacturing Co., Ltd. are:
1. Lift check valve: materials include cast iron, cast steel, stainless steel, chromium molybdenum steel; pressure: 1.0-16Mpa; connection methods include threaded connection, flange connection, welding; nominal pass: DN25-1200
Such as: cast steel lift check valve H41H-16C; stainless steel lift check valve H41W-16P; water pump bottom valve H42W-10/H42H-16C/H42W-16P.
Silence check valve HC41T-10; Silent check valve H42T-10; Spherical check valve HQ41X-10; Vertical fluorine-lined check valve H42F-10; Fluorine-lined lift check valve H41F46-16C; Wafer Muffler check valve H71T-10; Welded check valve H61H/Y-160
2. Swing check valve: the materials are cast iron, cast steel, stainless steel, chromium molybdenum steel; pressure: 1.0-16Mpa; connection methods include threaded connection, flange connection, welding; nominal passage: DN25-1200
Such as: cast steel swing check valve H44H-16C; stainless steel swing check valve H44W-16P; cast iron swing check valve H44T-10; rubber flap swing check valve HC44X-10; threaded connection Swing check valve H14H-16C/H14W-16P/H14T-10, H74W/F-16P.
3. Butterfly check valve: the materials are cast iron, cast steel, stainless steel, chromium molybdenum steel; pressure: 1.0-16Mpa; connection methods include threaded connection, flange connection, welding; nominal diameter: DN25-1200
Such as: double disc butterfly check valve H76H-16C/H76W-16P; micro resistance slow closing check valve HH47H-16C/HH48H-16C/HH49H-16C

To ensure your requirements, please specify when ordering:
1. For new project users, please provide the model designed by the design institute, and for replacement parts users, please provide the product model used before
2. If there is no specific model, please provide: 1. Use medium and temperature; 2. Working pressure; 3. Transmission method; 4. Connection method; 5. Structure form;
6. Nominal diameter, etc.
To
H41H-16C carbon steel lift check valve model, performance parameters, structure size parameters, price and other details. (Note: All text, data, and pictures in this article are for reference only. If you need detailed parameters, please call Senpin Company. With professional technology, professional manufacturing, and professional services, Tanghai Valve is committed to meeting user expectations , Constantly improve service quality, keep improving, “Sincere Service” is the eternal theme of Senpin. If you need help, please contact our sales Harry Li.)

TH VALVE is one of the largest butterfly valve manufacturers in China, main products are butterfly valves, check valves. Our products use advanced manufacturing technology, and strictly conform to API, DIN, BS, EN, ISO, GB and other international standards. The main products are butterfly valves, gate valves, check valves, globe valves, valve parts (Valve body, Valve disc, Valve shaft, Valve seat…), etc. Our products are widely used in various fields such as marine industry, shipbuilding, petrochemical, metallurgy, water treatment, fire fighting, water supply and drainage, etc. The company has won unanimous recognition and praise from customers with high quality and good reputation.

Related news /products:
Introduction of cast steel lift swing check valve;
The difference between carbon steel and cast steel;
Working principle diagram of lift check valve;
Classification of check valves;

Wafer type double disc swing check valve introduction

Introduction of wafer type double wing check valve:

1. Product appication of wafer type double swing check valve:

double plate check valve body

double plate check valve body

H76H/, H77H wafer butterfly double flap check valve is used for pure pipelines and industrial, environmental protection, water treatment, high-rise building water supply and drainage pipelines to prevent the reverse flow of media.

2. Product Features of wafer type double swing check valve:

  • Small size, light weight, compact structure and convenient maintenance
  • The valve plate adopts a dual type, which can be quickly closed under the elastic force of the spring.
  • Due to the quick closing effect, the medium can be prevented from flowing back
  • The length of the valve body structure is small and the rigidity is good
  • Safe and convenient, can be used for horizontal and vertical installation

3. Implementation standards

  • Flange connection size: GB/T1724.1-98
  • Structure length: GB/T12221-1989, ISO5752-82

4. Performance parameters:

  • Working pressure: 0-4 Mpa
  • Temperature: -29-425°C
  • Applicable medium: Water, Oil, Steam, Nitric acid.

5. Material of Dual Plate Swing check valve Parts

PART NAME Material
BODY Cast Iron; Ductile Iron; Stainless Steel; Carbon steel
DISC / PLATE Stainless Steel; Carbon steel; Bronze
SHAFT / STEM Stainless Steel Monel; Stainless Steel Inconel
SEAT / LINING NBR/EPDM/VITON
BOLTS Carbon steel
NUTS Stainless steel
SPRING SS304/SS306

Tanghai Valve is the best manufacturer of wafer type double swing 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…)

The principles and difference between one-way valve and check valve

One-way valve is sometimes called a check valve. One-way valve is a device in which fluid can only flow along the

double-wing-check-valve-3

double-wing-check-valve-3

water inlet, but the medium at the outlet cannot flow back. The function of the check valve is to prevent the medium in the pipeline from flowing back. So what is the difference between the two? What is their working principle? Now, Mr. Harry Li from Tanghai Valve will give you a detailed introduction.

The difference between one-way valve and check valve:

One-way valve is a control type One-way valve, and check valve is a non-control type One-way valve. That is: One-way valve is used to provide pressure, and its main function is to maintain pipeline pressure. Although the check valve can also provide this function, it is mainly used to control the return of the medium and does not require pressure. That is: One-way valve has a tendency to control, and check valve is purely natural.

One-way valve means that the fluid can only flow along the water inlet, but the medium at the outlet cannot flow back, commonly known as the One-way valve. One-way valve is a check valve. The installation position of a swing check valve is not restricted. It is usually installed in a horizontal pipeline, but it can also be installed in a vertical pipeline or a dumping pipeline. When installing a check valve, pay special attention to the flow direction of the medium. The normal flow direction of the medium should be consistent with the arrow direction indicated on the valve body, otherwise the normal flow of the medium will be blocked. The bottom valve should be installed at the bottom of the pump suction line. When the check valve is closed, water hammer pressure will be generated in the pipeline. In severe cases, it will cause damage to the valve, pipeline or equipment, especially for large-mouth pipelines or high-pressure pipelines. Therefore, it should cause high attention of the check valve selection. . The check valve is only a one-way opening and closing valve that prevents the backflow of fluid media on various pipelines or equipment.

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

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

1. One-way valve: It is a typical seat valve, One-way valve, also known as check valve or check valve. Used in hydraulic systems to prevent reverse flow of oil flow.

One-way valve has two types: straight type and right angle type. The straight-through One-way valve is installed on the pipeline with a threaded connection. Right-angle One-way valve has three forms: thread connection, plate connection and flange connection. The hydraulically controlled One-way valve is also called a lock valve or a pressure holding valve. It is the same as the One-way valve to prevent the reverse flow of oil. However, when the oil flow is required to flow in the reverse direction in the hydraulic circuit, the oil pressure can be controlled and the One-way valve can be opened so that the oil flow can flow in both directions. The hydraulically controlled One-way valve uses a tapered valve core, so the sealing performance is good. When the oil circuit is required to be closed, this valve can be used as a one-way locking of the oil circuit to maintain pressure. There are two types of hydraulically controlled One-way valve to control oil leakage: internal leakage and external leakage. The internal drain type can be used in the oil circuit with no back pressure at the oil flow reverse outlet; otherwise, the external drain type is required to reduce the control oil pressure.

2. Check valve is only one type of valve, it can be said that One-way valve is a kind of check valve. The check valve is only a one-way opening and closing valve that prevents the backflow of fluid media on various pipelines or equipment.

There are many types of check valves:

(1) Spring type: the liquid is from bottom to top, relying on the pressure to push up the valve flap controlled by the spring. After the pressure disappears, the spring force will press down the valve flap to seal the liquid back flow. Often used for check valves with small diameters.

(2) Gravity type: similar to the spring type, it relies on the self-gravity of the valve flap to close it to prevent backflow.

(3) Swing type: The liquid flows directly through the valve body, and the rotating disc on one side is opened by the pressure. After the pressure is lost, the disc relies on its own weight to return to the position, and the reverse liquid pressure closes the disc.

(4) Other One-way valve (check valve), such as sewage check valve.

The working principle of one-way valve:

The one-way valve only allows airflow to pass in one direction, and is completely closed in the opposite direction. After the air pressure is added to the left side, the air pressure acting on the valve core overcomes the spring force and friction force to open the valve core, and the air inlet and outlet are connected. The flow of airflow from left to right is called forward flow. In order to ensure a stable flow of air from the air inlet to the air outlet, a certain pressure difference should be maintained between the air inlet and outlet to keep the valve in the open position. If air pressure is added to the air outlet, the air cannot flow in and out, that is, the air flow cannot flow in the reverse direction.

The working principle of the check valve;

Check valve refers to the valve that automatically opens and closes the valve flap depending on the flow of the medium itself to prevent the medium from flowing back. It is also called check valve, one-way 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).

The function of this type of valve is to only allow the medium to flow in one direction, and to prevent the flow of 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.

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Materials, installation and features of vertical check valve

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)

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.

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