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Knife gate valve introduction and its characteristics

August 14, 2020

Knife gate valve entered China in the 1980s. In less than two decades, its use has expanded from ordinary fields to a

Knife gate valve (1)

wider range of industries, from coal preparation, gangue discharge, and slag discharge in mines and power plants to Urban sewage treatment has evolved from general industrial pipelines to specialized pipeline systems for food, sanitation, and medicine.

What is a knife gate valve:
Knife gate valve-also known as knife door valve, knife-type slurry valve, entered my country in the 1980s. In less than two decades, its scope of use has expanded from the general field to a wider range of industries. Coal preparation, gangue discharge and slag discharge from mines and power plants. It has developed into urban sewage treatment, from general industrial pipelines to professional pipeline systems such as food, sanitation, and medicine. The ultra-thin knife gate valve completely solves the large flow resistance of ordinary gate valves, flat gate valves, ball valves, globe valves, regulating valves, butterfly valves and other valves with its advantages of small size, small flow resistance, light weight, easy installation, and easy disassembly. , Heavy weight, difficult installation, large area and other difficult problems. After the emergence of knife gate valves, a large number of general shut-off valves and regulating valves have been replaced. To date, the world’s largest consumption of knife gate valves is the United States and Japan.

Characteristics of knife gate valve:

Knife gate valve-

1. Valve control can be used for local and remote control, and can also realize remote position display and remote centralized control according to user requirements.

2. Light weight: The body is made of carbon steel, and the weight is about 20%-30% lighter than the traditional gate valve. It is easy to install and maintain.

3. The use of this valve can improve the closing and sealing performance of the conveying pipeline system, prevent leakage to the maximum extent, and play a positive role in improving production efficiency and protecting the environment.

4. The sealing surface is made of highly wear-resistant and corrosion-resistant ceramic materials, and the use of inlay technology has high corrosion resistance and good wear resistance, so that the valve has a long life and the cost performance is 10 times higher than that of ordinary valves.

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

Working principle and movement mode of gate valve

August 13, 2020

The gate valve is a gate for opening and closing. The movement direction of the gate is perpendicular to the direction

13 gate-valve-5

of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate valve is sealed through the contact between the valve seat and the gate plate. Usually, the sealing surface will be welded with metal materials to increase wear resistance, such as 1Cr13, STL6, stainless steel, etc. The gate has a rigid gate and an elastic gate. According to the difference of the gate, the gate valve is divided into a rigid gate valve and an elastic gate valve.

Working principle of gate valve:
The opening and closing part of the gate valve is a gate. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate has two sealing surfaces. The two sealing surfaces of the most commonly used model gate valve form a wedge. The wedge angle varies with valve parameters, usually 5°, and 2°52′ when the medium temperature is not high. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce slight deformation to improve its manufacturability and compensate for the deviation of the sealing surface angle during the processing. The plate is called an elastic gate. When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, relying on the medium pressure to press the sealing surface of the gate to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate must be forced against the seat by external force to ensure the sealing performance of the sealing surface. The gate valve of the gate valve moves linearly with the valve stem, which is called the lifting stem gate valve, also called the rising stem gate valve. Usually there is a trapezoidal thread on the lifting rod, through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is turned into operating thrust. When the valve is opened, when the lift height of the gate is equal to 1:1 times the valve diameter, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as the mark, that is, the position where it cannot be opened, as its fully open position. In order to take into account the locking phenomenon of temperature changes, it is usually opened to the top position, and then back 1/2-1 circle, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate, that is, the stroke. In some gate valves, the stem nut is set on the gate, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate. This kind of valve is called a rotating stem gate valve, or a dark stem gate valve.

Movement mode of gate valve:
When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, only rely on the medium pressure to press the sealing surface of the gate to the valve seat on the other side to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves adopt forced sealing, that is, when the valve is closed, the gate must be forced against the seat by external force to ensure the sealing performance of the sealing surface.

Movement mode: The gate of the gate valve moves linearly with the valve stem, which is also called the rising stem gate valve. Usually there is a trapezoidal thread on the lifting rod, through the nut on the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, when the lift height of the gate is equal to 1:1 times the valve diameter, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as the mark, that is, the position where it cannot be opened, as its fully open position. In order to take into account the locking phenomenon due to temperature changes, it is usually opened to the top position, and then rewind 1/2-1 turn, as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (i.e. stroke). Some gate valve stem nuts are set on the gate, and the rotation of the handwheel drives the rotation of the valve stem to lift the gate. This kind of valve is called Rotating stem gate valve or dark stem gate valve.

The difference between globe valve and check valve

August 13, 2020

With the development of high-tech industry, various valves are often used in daily life. Today we will understand the difference between globe valves and check valves.

The difference between globe valve and check valve:
1. Check valve and stop valve are not the same thing, the difference between the two is mainly that the structure is

Globe valve (6)

very different.

2. The check valve is a one-way valve, which automatically prevents the fluid from flowing in the reverse direction, without a knob, and cannot artificially block the forward flow.

3. The stop valve has a knob, which can artificially control the forward flow. Due to its special structure, even if there is no artificial pipe valve, the fluid cannot flow in the reverse direction.

Globe valve:

The globe valve, also known as the shut-off valve, is a forced sealing valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to not leak. When the medium enters the valve from below the valve

lift-swing-check-valve-2

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

Check valve:

Check valve refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing back, also known as 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 the discharge of the container medium.

working principle of check valve:
Check valve refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing back. It is also called check valve, one-way valve, 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 the discharge of the container medium. The check valve can also be used to supply the auxiliary system 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).

Valve manufacturers recommend:
Tanghai Valve Factory is a technological enterprise that produces globe valves and check valves. It designs and produces according to your needs, and provides you with professional, high-quality, low-priced valve products. Welcome to call us for quotations.

Electric globe valves’ structural features and installation attention

August 12, 2020

Structural features of electric globe valve:

1. Open and close without friction. This function completely solves the problem of traditional valves affecting the

Globe valve (6)

sealing due to mutual friction between the sealing surfaces.

2. Top-mounted structure. The valves installed on the pipeline can be directly inspected and repaired online, which can effectively reduce device shutdown and reduce costs.

3. Single valve seat design. Eliminates the problem that the medium in the valve cavity affects the safety of use due to abnormal pressure increase.

4. Low torque design. The valve stem with special structure design can be opened and closed easily with only a small handle.

5. Wedge-shaped sealing structure. The valve relies on the mechanical force provided by the valve stem to press the ball wedge onto the valve seat to seal, so that the sealing performance of the valve is not affected by changes in pipeline pressure, and the sealing performance is reliably guaranteed under various working conditions.

6. Self-cleaning structure of the sealing surface. When the ball is tilted away from the valve seat, the fluid in the pipeline passes through the sealing surface of the ball evenly at 360°, which not only eliminates the local erosion of the valve seat by the high-speed fluid, but also washes away the accumulation on the sealing surface to achieve the purpose of self-cleaning .

7. The valve body and bonnet with valve diameter below DN50 are die forgings, and the valve body and bonnet above DN65 are steel castings.

8. The connection forms of the valve body and the bonnet are different, clamp pin shaft connection, flange gasket connection and self-sealing thread connection.

9. The sealing surfaces of the valve seat and the valve disc are all made of plasma spray welding or surfacing welding of cobalt-chromium-tungsten cemented carbide. The sealing surface has high hardness, wear resistance, scratch resistance and long service life.

10. The valve stem material is nitrided steel. After nitriding, the surface of the stem has high hardness, wear resistance, scratch resistance, corrosion resistance and long service life.

Electric shut-off valve installation attention:

1. Pay attention to the flow direction of the medium when installing the valve, and install it strictly in the direction indicated by the valve flow direction arrow.

2. The valve can be installed at any position of the pipeline, and at the same time, choose a carbon steel or alloy steel valve according to the temperature of the medium and the medium.

3. The electric globe valve should be installed vertically as far as possible, with the valve stem upward.

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

Characteristics and working principle of electric globe valve

August 12, 2020

Features of electric globe valve:

The fluid resistance is small, and its resistance coefficient is equal to that of a pipe section of the same length.
Globe valve (9)
Simple structure, small size and light weight. Electric globe valve
It is tight and reliable. The sealing surface material of the gate valve is widely used plastic, and it has good sealing performance. It has also been widely used in vacuum systems.
It is easy to operate and open and close quickly. It only needs to rotate 90° from fully open to fully closed, which is convenient for remote control.
The maintenance is convenient, the gate valve has a simple structure, the sealing ring is generally movable, and it is convenient to disassemble and replace.
When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium will not cause erosion of the valve sealing surface when the medium passes.
It has a wide range of applications, with a diameter ranging from a few millimeters to a few meters, and can be applied from high vacuum to high pressure.

Electric globe valve classification:

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

Working principle of electric globe valve:

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

A. Opening process of globe check valve:

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

B. Closing process of electric globe valve:

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

TH Valve is a professional manufacturer of butterfly 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

Comparison of bellows globe valve and ordinary globe valve

August 12, 2020

Comparison of bellows globe valve and ordinary globe valve:

Globe valve (3)

1. Double sealing design (bellows + packing) If the bellows fails, the stem packing will also avoid leakage and meet international sealing standards.
2. There is no fluid loss, reducing energy loss and improving plant equipment safety.
3. Long service life, reduce maintenance times and lower operating costs.
4. The sturdy and durable bellows seal design ensures zero leakage of the valve stem and provides maintenance-free conditions.
5. The gas medium valve seat adopts PTFE soft sealing material to improve the sealing performance of this valve.
6. High temperature resistance≤425℃The valve seat adopts conical hard seal. Achieve airtight performance and zero leakage.

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

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.

Classification of the globe valves-(1)

August 12, 2020

According to the channel direction, the globe valve is devided into 4 types:

Globe valve (6)

1) Straight-through globe valve.
2) Direct flow stop valve: In direct flow or Y-shaped stop valve, the flow passage of the valve body is in a diagonal line with the main flow passage, so that the damage degree of the flow state is less than that of the conventional stop valve, so the pressure loss through the valve is also corresponding Is too small.
3) Angle type stop valve: In the angle type stop valve, the fluid only needs to change its direction once, so that the pressure drop through this valve is smaller than that of the conventional structure.
4) Plunger type globe valve: This type of globe valve is a variation of the conventional globe valve. In this valve, the disc and valve seat are usually designed based on the plunger principle. The valve clack is polished so that the plunger is connected to the valve stem, and the sealing is achieved by two elastic sealing rings sleeved on the plunger. The two elastic sealing rings are separated by a collar, and the sealing ring around the plunger is pressed firmly by the load exerted on the bonnet by the bonnet nut. The elastic sealing ring can be replaced and can be made of various materials. The valve is mainly used for “open” or “close”, but it is equipped with a special form of plunger or a special collar, which can also be used to adjust the flow .

The position of the thread on the valve stem:

1) Upper threaded stem stop valve: The thread of the stem of the stop valve is on the outside of the valve body. The advantage is that the valve stem is not corroded by the medium and is convenient for lubrication. This structure is more common.

2) Bottom thread stem stop valve: The thread of the stem of the stop valve is in the valve body. The stem thread of this structure is in direct contact with the medium, which is susceptible to corrosion and cannot be lubricated. This structure is used in places with small diameters and low temperatures.

There are many domestic manufacturers of globe valves, and most of the connection sizes are not uniform. It is mainly divided into the following categories: General category based on JB/T2203-1999 “Structural Length of Stop Valves”. At present, most domestic shut-off valve manufacturers design and produce according to this standard. However, this standard is not perfect, and the specifications are not complete. The maximum nominal diameter of a single gate valve is DN1200, and the maximum nominal diameter of a double gate valve is DN1500. According to the specifications of the shut-off valve produced by the manufacturer and the information available, the smallest nominal diameter of the angle-type shut-off valve is DN15, and the nominal diameter of the Z-type straight-through shut-off valve reaches DN2000. After research, the connection size of each manufacturer is not uniform. In order to have a unified standard, users can interchange the same specifications when selecting and installing, it is recommended that China General Machinery Research Institute revise JB/T2203-1999 “Structural Length of Stop Valves”. It is recommended that the design institute and users choose according to the standard, and the stop valve manufacturer should design and manufacture according to the standard.

Introduction of cast steel lift swing check valve

August 5, 2020

1. Overview of Cast steel lift check valve:

The lift check valve is selected for the pipelines of various working conditions such as petroleum, chemical industry

lift swing check valve (2)

and thermal power plants with a nominal pressure of PN1.6～6.4MPa and a working temperature of -29～550℃. Applicable media are: water, oil, steam, etc.

2. Structural features of Cast steel lift check valve:

1. Exquisite selection of materials, in line with domestic and foreign standards, the highest quality of materials.

2. The sealing pair is advanced and reasonable. The sealing surface of the valve disc and the valve seat is made of iron-based alloy or Stellite cobalt-based cemented carbide. It has good wear resistance, high temperature resistance, corrosion resistance and scratch resistance. ,long lasting.

3. The products are designed and manufactured according to the national standard GB/T12235.

4. Various piping flange standards and flange sealing types can be used to meet various engineering needs and user requirements.

5. The valve body has a complete range of materials, and the gasket can be reasonably selected according to actual working conditions or user requirements, and can be suitable for various pressure, temperature and medium working conditions.

According to user requirements, check valves with different structures and connections can be designed and manufactured for use with various equipment.

H41H lift check valve: Do not allow the check valve to bear weight in the pipeline. Large-scale check valves should be independently supported to prevent them from being affected by the pressure produced by the pipeline system. When installing, pay attention to the direction of medium flow should be consistent with the arrow direction indicated by the valve body. Suitable for water, steam, oil, nitric acid, acetic acid, oxidizing medium, urea and other media.

H41H, H41Y type PN16~PN100 lifting steel check valve is one of the important links in the production process regulation system. It is a valve that controls the one-way flow of the medium in the pipeline to prevent the medium from flowing back. It is widely used in purification equipment, petroleum, chemical industry, metallurgy, electric power, textile and other production processes.

Product features of lift check valve:

1. H41H and H41Y lift-type steel check valves have the advantages of simple structure, reliable action and convenient maintenance.

2. When the medium flows into the valve body from the direction indicated by the arrow of the valve body, the pressure of the medium acts on the valve flap to produce an upward thrust. When the medium thrust is greater than the weight of the valve flap, the valve opens. When the force of the medium pressure acting on the disc after the valve plus the weight of the disc itself is greater than the force of the pressure acting on the disc before the valve, the valve is closed to prevent the medium from flowing back.

Lift 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, also known as 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).

Check valves are also called check valves, check valves, reverse flow valves, and back pressure valves.

The function of the check valve is to only allow the medium to flow in one direction and prevent the reverse flow. 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 internal thread check valve and the butterfly check valve belong to this type of valve.

It includes swing check valve and lift check valve. 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 really contact the valve seat. The valve disc 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 valve disc of the lift check valve is seated on the sealing surface of the valve seat on the valve body. Except that the disc can be lifted and lowered freely, the rest of this valve is like a shut-off valve. The fluid pressure lifts the disc from the sealing surface of the valve seat, 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 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 that of the swing check valve, and the flow rate of the swing check valve is restricted Rarely.

Wafer type double disc swing check valve introduction

August 4, 2020

Introduction of wafer type double wing check valve:

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

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

August 4, 2020

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

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

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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