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What is the reason for the poor sealing of the valve

February 17, 2022

Where there is a pipeline, the valve is inseparable. The valve is installed on the pipeline and controls the flow of the fluid medium in the pipeline. It is an important control component. But the valve is also a wearable part. A common valve loss in our life is that the valve is not tightly sealed, resulting in leakage. So what is the reason for the poor

marine valve seat

sealing of the valve?
The leakage at the packing of the valve is a part of the valve that is prone to leakage failures. The valve is not tightly sealed, and the reasons are probably as follows.
1. Sealing auxiliary structure
Under the change of temperature or sealing force, the structure of the sealing pair will change. And this change will affect and change the force between the sealing pair, so that the performance of the valve sealing is reduced. Therefore, when choosing a seal, be sure to choose a seal with elastic deformation. At the same time, pay attention to the width of the sealing surface. The reason is that the contact surfaces of the sealing pair cannot be completely matched. When the width of the sealing surface increases, the force required for sealing is increased.
2. Specific pressure of sealing surface
The specific pressure of the sealing surface affects the sealing performance of the valve and the service life of the valve. Therefore, the specific pressure of the sealing surface is also a very important factor. Under the same conditions, too high specific pressure will cause valve damage, but too low specific pressure will cause valve leakage. Therefore, we need to fully consider the appropriateness of the specific pressure when designing
3. Physical properties of the medium
The physical properties of the medium also affect the valve sealing performance. These physical properties include temperature, viscosity, and hydrophilicity of the surface, among others. The temperature change not only affects the slackness of the sealing pair and the change of the size of the parts, but also has an inseparable relationship with the viscosity of the gas. Gas viscosity increases or decreases with increasing or decreasing temperature. Therefore, in order to reduce the influence of temperature on the sealing performance of the valve, when designing the sealing pair, we should design it as a valve with thermal compensation such as an elastic valve seat. Viscosity is related to the permeability of the fluid. When under the same conditions, the higher the viscosity, the lower the permeability of the fluid. The hydrophilicity of the surface means that when there is a film on the metal surface, the film should be removed. Because of this very thin oil film, it will destroy the hydrophilicity of the surface, resulting in blockage of fluid channels.
4. The quality of the sealing pair
The quality of the sealing pair mainly means that we must check the selection, matching and manufacturing accuracy of materials. For example, the valve disc fits well with the valve seat sealing surface, which can improve the sealing performance. The characteristic of many circumferential waviness is that its labyrinth sealing performance is good.

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

Video of center-lined butterfly valve:

factors affecting the sealing performance of resilient butterfly valve seat

October 21, 2021

Rubber butterfly valve is an important part of regulating flow medium, and tight sealing is the most important quality of the product. The sealing performance of rubber butterfly valves is affected by many factors, and the most important influence is still closely related to the sealing surface. Today we will focus on three factors. Let’s take a

Wafer type butterfly valve with worm gear

look at the main factors that affect the sealing performance of rubber butterfly valves:

1. Quality of the sealing surface/valve seat
First of all, we must make it clear that the sealing surface refers to the part where the valve seat and the disc are in contact with each other for medium opening and closing control, and only which part of the valve seat and the disc are in contact instead of the entire sealing pair. The quality of the sealing surface is mainly related to the quality of the sealing material. The quality of the sealing material should be produced by the brand manufacturer and qualified in process. In addition, the choice of sealing material should be in line with the medium. For example, rubber butterfly valves cannot be used for highly corrosive media.

2. Width of sealing surface/valve seat
The width of the sealing surface mainly affects the movement resistance of the fluid. The larger the sealing surface, the lower the resistance, and the narrower the resistance is relatively large. Therefore, the increase in the width of the sealing surface can reduce the erosion and wear of the sealing surface by the fluid. At the same time, because the increase in the width of the sealing surface increases the length of the leakage stroke proportionally, the leakage can be reduced proportionally. However, the width of the sealing surface must not be excessively increased, because an increase in the width of the sealing surface, under the same sealing force, the reduction of the specific pressure of the seal will increase the possibility of leakage.

3. The pressure difference between before and after the valve
The specific pressure on the sealing surface is caused by the pressure difference between the front and rear of the valve and the applied sealing force, which refers to the pressure acting on a unit area of the sealing surface. The specific pressure directly affects the sealing performance, reliability and service life of the rubber butterfly valve. When the specific pressure on the sealing surface is small and the surface roughness is low, the leakage increases rapidly. When the specific pressure on the sealing surface is large, the effect of surface roughness on the leakage is significantly reduced.

In addition, the sealing performance of the rubber butterfly valve is related to the sealing surface material of the butterfly valve and its processing state, the nature of the medium, the existence of the sealing oil film, the rigidity and structural characteristics of the closing part, and so on. For more information, please call Tanghai for inquiries, and we will have professionals to answer your questions about butterfly 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

What are the main factors affecting valve sealing?

September 11, 2020

Valve leakage is very common in daily life and industrial production, and the impact is very large. It will cause waste or bring danger to life. For example, the leakage of tap water valve will lead to serious consequences, such as the

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

chemical industry. Toxic, harmful, flammable, explosive and corrosive media leakage, etc., serious threats to personal safety, property safety and environmental pollution accidents. A valve that relies on external force to rotate and drive to open and close is designed with a sealing device. It is used to install a certain number of packing seals in the packing culvert to achieve a sealing effect, but how about the sealing? Leakage at the packing of the valve is one of the most prone to leakage failure in the valve, but the reasons are largely the following reasons.

1. The structure of the sealing pair

The structure of the sealing pair will change when the temperature or sealing force changes. Moreover, this change will affect and change the mutual force between the sealing pairs, thereby reducing the performance of the valve sealing. Therefore, when choosing a seal, be sure to choose a seal with elastic deformation. At the same time, pay attention to the width of the sealing surface. The reason is that the contact surfaces of the sealing pair cannot be completely matched. When the width of the sealing surface increases, the force required for sealing must be increased.

2. The specific pressure of the sealing surface

The specific pressure of the sealing surface affects the sealing performance of the valve and the service life of the valve. Therefore, the specific pressure of the sealing surface is also a very important factor. Under the same conditions, too much specific pressure will cause damage to the valve, but too little wine will cause valve leakage. Therefore, we need to fully consider the appropriateness of the specific pressure when designing.

3. The physical properties of the medium

The physical properties of the medium also affect the sealing performance of the valve. These physical properties include temperature, viscosity and surface hydrophilicity. The temperature change not only affects the slackness of the sealing pair and changes in the size of the parts, but also has an inseparable relationship with the viscosity of the gas. The gas viscosity increases or decreases as the temperature increases or decreases. Therefore, in order to reduce the influence of temperature on the sealing performance of the valve, when we design the sealing pair, we must design it into a valve with thermal compensation such as an elastic valve seat. Viscosity is related to the permeability of the fluid. When under the same conditions, the greater the viscosity, the smaller the permeability of the fluid. The hydrophilicity of the surface means that when there is a thin film on the metal surface, the thin film should be removed. Because this thin oil film will destroy the hydrophilicity of the surface and block the fluid channel.

4. The quality of the sealing pair

The quality of the sealing pair mainly refers to the selection, matching, and manufacturing accuracy of materials. For example, the valve disc and the sealing surface of the valve seat are very consistent, which can improve the sealing performance. The characteristic of many hoop waviness is its good labyrinth sealing performance.

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

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What is the reason for the poor sealing of the valve

factors affecting the sealing performance of resilient butterfly valve seat

What are the main factors affecting valve sealing?

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