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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.

The difference between one-way valve and check valve

August 4, 2020

One-way valve means that the fluid can only flow along the water inlet, and the medium at the water outlet

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cannot return. Used in hydraulic systems to prevent reverse flow of oil or pneumatic systems to prevent reverse flow of air. 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.

There are two types of check valves: straight-through and right-angle. The straight-through check valve is installed on the pipeline with a threaded connection. Right-angle check valves have three forms: threaded connection, plate connection and flange connection. Hydraulic control check valve is also called lock valve or pressure maintaining valve. It is the same as check valve to prevent 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 to open the one-way valve so that the oil flow can flow in both directions. The hydraulic control check valve adopts a conical 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 check valve to control oil leakage: internal leakage and external leakage. The internal drain type can be used in the oil circuit where the oil flow reverse outlet has no back pressure; otherwise, the external drain type is required to reduce the control oil pressure.

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). 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.

One-way valve is a directional control valve in which air flow can only flow in one direction but not in the reverse direction. Its working principle is the same as the hydraulic one-way valve. Compressed air enters from port P, overcomes the spring force and friction force to open the one-way valve port, and the compressed air flows from P to A; when there is no compressed air at port P, it will be under the action of spring force and remaining force of port A (cavity) ; The valve port is in the closed state, so that the air flow from A to P is blocked. The one-way valve is used in occasions where the air flow is not allowed to flow in the opposite direction. For example, when the air compressor is inflating the air tank, a one-way valve is set between the air compressor and the air tank to prevent the air tank when the air compressor stops working. The compressed air in the air flow is returned to the air compressor. One-way valves are often combined with throttle valves and sequence valves to form one-way throttle valves and one-way sequence valves.

Check valves have a wide range of uses, and there are many types. The following are the check valves commonly used in water supply and heating:

1. Spring type: the liquid is from bottom to top, and the valve clack controlled by the spring is pushed up by the pressure. After the pressure disappears, the spring force pushes down the valve clack to seal the liquid back flow. Often used for check valves with small diameters.

2. Gravity type: Similar to spring type, it is closed by the gravity of the valve disc 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. Plastic diaphragm type: Both the shell and the diaphragm are plastic. The general shell is ABS, PE, PP, NYLON, PC. The diaphragm includes silicone resin, fluororesin, etc.

In general, the check valve and the check valve are basically the same thing, but there are some differences. The check valve is a controlled check valve, and the check valve is a non-controlled check valve. That is to say, the 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.

The above is about the difference between check valve and check valve. In fact, a check valve is only one type of valve, and a oneway valve is only a type of check valve. It is only a one-way open-close valve that prevents backflow of fluid in various pipelines or equipment. Check valves have a wide range of uses.

What is double plate swing check valve

August 3, 2020

Main features of Double plate swing check valve:

double wing check valve (5)

Two valve plates are fixed on the valve body along a pivot axis, and two springs are installed on the butterfly plate above the sealing surface. Driven by the pressure of the medium flow, the spring is compressed to force the butterfly plate to open. When the medium flows back , The spring forces the valve to close. This kind of valve can be assembled on horizontal and vertical pipelines.

Design Features of Double plate check valve:
Design standard: API 594, API 6D, ASME B16.34, GB/T 12236
Good sealing performance
Small size and light weight
Wide application, flexible disc, fast closing
Valve plate closes quickly
Small closing impact

Product Range:
Body material: carbon steel, stainless steel, alloy steel
Caliber: 1/2″~60″(DN15~DN1500)
Pressure range: Class150~2500 (PN10~PN420)
Connection method: RF, RTJ, BW
Working temperature: -196℃~+560℃

TH VALVE is one of the largest double plate check valve manufacturers in China, main products are butterfly valves, check valves: 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…)

What is a Single-disc swing check valve

August 3, 2020

Product details of Single-disc swing check valve:
Brand: THV

single disc swing check valve body

Type: TH-CKV-SDS
Material: Stainless steel, cast iron, etc.
Connection form: Wafer structure Butterfly type
Nominal diameter DN15-DN400 (mm)
Applicable medium: fresh water, sea water, steam, food, medicine —-
Form Butterfly Pressure Environment Normal Pressure Standard British Standard American Standard National Standard Flow Direction Two-way Drive Mode Manual Operating Temperature Normal Temperature Type (Channel Position) Straight-through

Applicable medium:
Fresh water, sea water, air, steam, food, medicine, and various oils, acids, alkalis, salts, etc.

Features of single disc swing check valve:
Long service life, reliable sealing performance and no frequent maintenance. The flow characteristic of the butterfly valve is 3 times that of the globe valve and 75% of the gate valve of the same specification. The butterfly valve can realize the switching and regulating function of the fluid in the pipeline. Compared with the gate valve and the stop valve, it has a better multifunctional type. The various choices of internal parts and elastic materials make butterfly valves widely used in the chemical industry.

The butterfly valve is light in weight and small in size. For example: the weight and volume of a 10″ butterfly valve are respectively 1/9 and 1/6 of a 10″ gate valve. Therefore, the butterfly valve is easy to install and can save the cost of the piping system. Compared with metal-sealed gate valves and globe valves, soft-sealed butterfly valves can achieve complete air tightness. The butterfly valve is easy to operate and can realize the opening and closing function within a 90° rotation range. The price of the butterfly valve of the same specification is about 35-40% of the price of the gate valve, and the installation cost of the butterfly valve is relatively low. The correctly installed butterfly valve has a certain degree of self-cleaning, and it is not easy to fail due to the stolen goods in the pipeline.

Note: The valve connecting flange size in this table conforms to BS4504 PN10, and the transmission connecting flange size conforms to ISO5211. In addition, it also meets the flange connection standards of other countries and the special connection sizes required by customers.

TH valve is one of the largest butterfly valve manufacturers in China, main products are butterfly valves, check valves.., 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…)

What is a single plate check valve

August 3, 2020

Single-plate check valve is also called single-disc check valve, wafer check valve: it is a valve that can automatically

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prevent fluid backflow. The disc of the check valve is opened under the action of fluid pressure, and the fluid flows from the inlet side to the outlet side. When the pressure on the inlet side is lower than that on the outlet side, the valve flap is automatically closed under the action of the fluid pressure difference, gravity and other factors to prevent the fluid from flowing back. It can be installed horizontally or vertically. For vertical installation, pay attention to the water flow from bottom to top, and pay attention to whether the installation direction is correct.

There are two types of check valves. One is installed at the end of the vertical suction pipe in front of the water pump bai. The purpose is to fill the water pump without pumping water once, because the water pump can only be used when there is no water in the pump and the suction pipe in front of the pump. Idling cannot pump water, so the pump must be filled with water to pump out water. The installation of this pump is a method when it is above the liquid level. It is also called a negative pressure method such as pumping water up from a well. Another way to install the pump is that the liquid level is higher than the pump. This method is generally used for secondary water supply. Because the liquid level is higher than the pump, it is not necessary to close the pump outlet valve when starting and stopping the pump, so the check valve should be installed in the The rear of the water pump.
Whether the check valve is installed before or after the valve does not affect its function.

Precautions for installation of single plate check valve

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 comply with the current national standard “General Valve Marking” GB 12220. It can be used after all standards are qualified.

1. 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.

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.

What is vertical check valve

July 31, 2020

Vertical check valve: Due to the pressure of the medium at the inlet end of the pipeline, the valve can be opened or

silent check valve (3)

closed by overcoming the spring resistance. When the medium pressure at the inlet end is lower than that at the outlet end, the spring pushes the valve core to the valve seat to close the valve, preventing the medium from flowing back, so it plays a role of check. Vertical check valves are widely used in chemical, liquefied petroleum gas, fluid and other industries. According to the structure of the check valve, it can be divided into three types: lift check valve, swing check valve and butterfly check valve.

Introduction of vertical check valve:
Vertical 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 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).

lift check valve Working principle diagram

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.

Among them, internal thread check valve and butterfly check valve belong 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 disc can reach the proper position of the valve seat surface every time, the valve disc is designed in a hinge mechanism so that the valve disc has enough space for turning and makes the valve disc come into contact with the valve seat truly and comprehensively. 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 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 embedded in 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.

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.

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

The difference between one-way valve and check valve

What is double plate swing check valve

What is a Single-disc swing check valve

What is a single plate check valve

Materials, installation and features of vertical check valve

Use performance and working principle of vertical check valve

What is vertical check valve

Stainless steel vertical check valve

Industry development prospects of check valve

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