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Process design of check valve

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

8 tilting-disc-swing-check-valve-3

8 tilting-disc-swing-check-valve-3

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

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

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

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

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

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

double-wing-check-valve-3

double-wing-check-valve-3

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

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

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

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

6 single-plate-swing-check-valve-2

6 single-plate-swing-check-valve-2

systems.

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

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

Related news /knowledge:
Valve cleaning steps and assembly requirements;
The difference between carbon steel and cast steel;
Knife Gate valve (TH-PZV);
Valve material and valve standards-(1);

Installation method and precautions of check valve

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

double-wing-check-valve-3

double-wing-check-valve-3

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

Silent check valve

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

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

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

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

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

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

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

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

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

Related news /products:
All types of check valve and its structures;
Valve installation instructions and process precautions;
Daily maintenance and precautions of ball valves
Introduction of cast steel lift swing check valve;

Classification of check valves

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

tilting disc swing check valve (6)

tilting disc swing check valve (6)

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

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

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

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

3. The butterfly check valve is straight-through.

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

Classified by material:
1. Cast iron check valve

2. Brass check valve

3. Stainless steel check valve

4. Carbon steel check valve

5. Forged steel check valve

Classified by function:
1. DRVZ silent check valve

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

3.NRVR silent check valve

4. SFCV rubber flap check valve

5.DDCV double disc check valve

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

Check valve and its working principle

What is check valve?

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

tilting disc check valve body (2)

tilting disc check valve body (2)

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

Working principle of check valve:
Check valves can also be used to supply pipelines for auxiliary systems whose pressure may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).

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

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

Related news /products:
All types of check valve and its structures;
Introduction of cast steel lift swing check valve;
Classification of check valves;
Working principle diagram of lift check valve;

Slow-closing design of stainless steel swing check valve

1. Structural improvement of swing check valve
A slow closing auxiliary valve is added on the flap of the original swing check valve. The auxiliary valve is installed on the lower side or both sides of the main valve

double-wing-check-valve-3

double-wing-check-valve-3

flap and is connected by threads. When the medium flow valve is opened, the medium pressure opens the auxiliary valve, and the medium flows into the main valve outlet through the small valve orifice, so that the main valve inlet end When the pressure is relieved, the valve flap of the main valve opens, and the pressure before and after the main valve tends to balance; when the medium reverses flow, the valve flap of the main valve closes quickly under the action of the reverse flow medium, and the upper part of the auxiliary valve body is a buffer cylinder, and the auxiliary valve cover is screwed into the valve.

There is a small hole on the cover of the upper part of the body. There is a certain gap between the valve flap of the auxiliary valve and the piston rod. The O-ring rubber seal is used between the piston and the buffer cylinder. The flat seal between the lower part of the piston and the valve flap; When the flap is closed with the main valve flap closed, the medium gradually flows into the upper chamber of the auxiliary valve buffer cylinder through the small hole due to the small hole of the auxiliary valve cover, and part of the medium flows back through the gap between the auxiliary valve flap and the piston rod Therefore, the auxiliary valve piston is closed slowly. In this structure, the closing of the main valve is equivalent to the fast closing stage, and the slow closing of the auxiliary valve is equivalent to the slow closing stage. According to the hydraulic and mechanical transition mechanism of the pump station unit, the structure design can effectively prevent the water hammer from boosting.

2. Improvement of lift check valve structure
The lifting check valve, also known as the bottom valve, can maintain the water column required for pumping when the pump is stopped; the feature of the valve structure improvement is that a slow closing auxiliary valve is added between the main valve flap and the valve body bracket as shown.

 lift-swing-check-valve-2

lift-swing-check-valve-2

A gasket ring is added between the valve body and the bottom net to increase the height of the valve flap. The buffer piston and the buffer cylinder are sealed with rubber. The valve flap shaft and the piston are rigidly connected, and the gap between the buffer cylinder and the valve flap shaft is small. When the medium flows downstream, the pressure medium pushes the valve flap into the main valve body cavity, and at the same time pushes the buffer piston upward; when the medium flows backward, the buffer cylinder is fully filled with the medium when it is opened, and the gap between the buffer cylinder and the valve disc shaft is relatively large. It is small, so as the medium in the buffer cylinder is gradually discharged through the gap, the main valve flap closes to play a buffering role, so that the water hammer boost in the pipe network can be controlled.

3. Test results before and after the improvement of the check valve slow closing structure
A calibrated pressure gauge is used, and the pressure signal is sent to the oscilloscope for recording by the differential pressure transmitter, and the water hammer pressure change value at each moment is read on the oscillogram with the calibrated ratio R.
The test valve has a diameter of 100mm, a system pressure of 0.5MPa, and a flow rate of 5L/s. When the pump stops suddenly, it shows the pressure-time curve of the inlet side of the check valve after the power is cut off
(1) The main valve flap opens and closes smoothly, the slow-closing auxiliary valve has a compact structure and reliable performance.
(2) The valve flap of the main valve closes first and then closes slowly, which can effectively prevent destructive water hammer and expand the use range of the check valve.
(3) The improved structure is simple and easy to produce and interchange.
(4) The slow-closing auxiliary valve can be repaired or replaced without hindering the use of the check valve.

The check valve is a valve that opens when the pipeline system is downstream and closes when it is upstream. It is mainly used to prevent backflow of the medium, prevent the pump and drive motor from reversing, and release the medium in the container. The rotary check valve with the shaft rotating and the lift check valve moving along the vertical center line of the valve body, but the valves of the above two structures both have the medium backflow speed rapidly reduced from the maximum to zero when the valve is closed, causing the pipeline The internal pressure on the side of the water inlet pipe rises rapidly, resulting in a water hammer phenomenon that has a destructive effect on the pipeline system, so the general check valve production caliber is 50 to 500 mm. In order to reduce the water hammer effect of the check valve and expand the range of use of the check valve, on the basis of the original product, a slow closing auxiliary valve was added to solve the problem of pipeline water hammer boosting.

Tianjin Tanghai Valve Manufacturing Co., Ltd. is one of the largest butterfly valve, check valve manufacturers in China. After 14+ years of continuous development and innovation, the company now has a group of high-tech engineers, technicians and skilled production workers, advanced production technology, sophisticated manufacturing equipment, complete testing methods, in strict accordance with international standards and quality management system, formed A comprehensive quality control network.

Related news/knowledges: Working principle diagram of lift check valve; Introduction of cast steel lift swing check valve

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