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Types of Sealing Material of Electric Wafer Butterfly Valve

Electric wafer butterfly valves can be divided into soft-sealed butterfly valves and hard-sealed butterfly valves, which are distinguished according to the sealing materials of electric butterfly valves.

triple eccentric butterfly valve-wafer-lug-double flange-welded (5)

triple eccentric butterfly valve-wafer-lug-double flange-welded (5)

The soft sealing butterfly valve’s sealing feature is that one side of the two sides is made of metal material, and the

other side is made of elastic non-metal material, that is, one of the valve seat and the valve plate is made of elastic material, which is called “soft seal” . The hard seal butterfly valve means that both sides of the seal pair are made of metal materials or other harder materials, that is, the valve seat and the valve plate are both hard materials, which is called “hard seal”.

The difference between soft seal and hard seal of electric wafer butterfly valve
Although the soft-sealed electric wafer butterfly valve has certain strength, hardness and temperature resistance, it has good sealing performance and can achieve zero leakage. But it is not resistant to high temperature, easy to wear, and has poor mechanical properties. Our common ones are steel + rubber, steel + PTFE and so on. The hard seal of the butterfly valve has poor sealing performance, but it is resistant to high temperature, abrasion and mechanical properties. Such as steel + steel, steel + copper, steel + graphite, steel + alloy steel. The steel here can be cast iron, cast steel, alloy steel or surfacing, sprayed alloy.

The advantages and disadvantages of the soft and hard seals of the electric wafer butterfly valve

In terms of sealing performance, the soft-seal electric wafer butterfly valve is relatively good, but compared with the hard-seal butterfly valve’s corrosion resistance, the soft-seal electric butterfly valve cannot meet the process requirements for corrosive materials. The advantage of the soft sealing butterfly valve is that it has good sealing performance, but the disadvantage is that it is easy to age, wear, and has a short service

Double offset-butterfly valve-D972F-150lbC (1)

Double offset-butterfly valve-D972F-150lbC (1)

life. The hard-sealed butterfly valve has a long service life, but the sealing performance is relatively worse than that of the soft-sealed butterfly valve. Now there is a kind of multi-level sealing electric wafer butterfly valve that combines the advantages and disadvantages of soft sealing and hard sealing to form a complement to each other, which is a major upgrade of the product.

Different working conditions of soft and hard sealing of electric wafer butterfly valve
Let’s take a look at the different working conditions of the soft seal and the hard seal of the electric wafer butterfly valve from four aspects. The details are as follows:
1. Structure: soft-sealed electric wafer butterfly valves are mostly centerline butterfly valves, and hard-sealed electric wafer butterfly valves are mostly single eccentric butterfly valves, double eccentric butterfly valves, and triple eccentric butterfly valves.
2. Temperature resistance: soft-sealed electric butterfly valve is used in normal temperature environment. The hard-sealed electric butterfly valve can be used in low temperature, normal temperature, high temperature and other environments.
3. Pressure: The soft-sealed electric wafer butterfly valve can be used in low and normal pressure, and the hard-sealed electric butterfly valve can also be used in medium and high pressure conditions.
4. Sealing performance: The soft sealing electric butterfly valve and the triple eccentric hard sealing electric butterfly valve have better sealing performance. The triple eccentric butterfly valve can maintain a good seal under high pressure and high temperature environment.

Based on the above characteristics, the soft-sealed electric wafer butterfly valve is suitable for the two-way opening and closing and adjustment of ventilation and dust removal pipelines, water treatment, light industry, petroleum, chemical and other industries. Hard-sealed electric butterfly valves are mostly used in heating, gas, gas, oil, acid and alkali environments.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Video of center-lined butterfly valve:

Video of double eccentric butterfly valve:

Related news/knowledge:
What are the characteristics of the soft sealing butterfly valve
Fluorine-lined butterfly valve vs metal seated butterfly valve
What are the characteristics of the hard seal butterfly valve
pneumatic fluorine-lined butterfly valve vs pneumatic hard-sealed butterfly valve

How to choose the material of flanged gate valve seat

The sealing surface of flanged gate valve is an important working surface for the valve to block the medium and control the fluid. The quality of the sealing surface determines whether the valve is guaranteed to have no internal leakage, impermeability and other direct influence factors, which can be said to determine the service life of the valve. If the sealing surface is damaged, the valve will not work properly. Among them, the material selection of the sealing surface is a very important factor, and it is very important to guarantee the quality of the sealing surface. Therefore, the following factors should be considered when selecting the valve sealing surface material:

AWWA C509-C515-resilient seated gate valve-DN600-150lb (2)

AWWA C509-C515-resilient seated gate valve-DN600-150lb (2)

1. Corrosion resistance
Whether the medium is pure water or other, it will cause certain corrosion to the flanged gate valve. The surface of the sealing surface will inevitably be damaged under the action of the high-speed passage of the medium. Delaying this process is our primary consideration when selecting sealing surface materials. Once the surface of the sealing surface is damaged, the sealing performance of the valve cannot be guaranteed, and the medium will easily leak from the damaged part of the sealing surface. Therefore, the sealing surface material must be corrosion resistant. The corrosion resistance of a material mainly depends on the chemical stability of the material. But secondly, we must consider the medium conditions to see if it matches the sealing material.
2. Friction resistance
Because the medium and the sealing surface move relative to each other, and it is a high-speed process, damage to the material due to friction is inevitable. Such damage will eventually inevitably cause damage to the sealing surface. Therefore, the sealing surface material must have good friction resistance, especially for flanged gate valves. The wear resistance of the sealing material is often determined by the internal properties of the material. At the same time, pay attention to the valve installation location to meet the needs.
3. Erosion resistance
The image of the erosion phenomenon is a process in which the sealing surface is destroyed when the medium flows through the sealing surface at a high speed. This kind of damage is more obvious in the throttle valve used in high temperature and high pressure steam medium, because it needs to be opened and closed frequently, which has a great impact on the damage of sealing. Therefore, erosion resistance is also one of the important requirements of the sealing surface material.
4. The sealing surface of flanged gate valves should have a certain degree of hardness, and the hardness will drop greatly under the specified working temperature.
5. The linear expansion coefficient of the sealing surface of the gate valve and the body material should be similar, which is more important for the structure of the inlaid sealing ring, so as to avoid excessive stress and loosening at high temperatures.
6. When used under high temperature conditions, it must have sufficient anti-oxidation, thermal fatigue resistance and thermal cycling.
When faced with real working conditions, it is difficult to find a sealing surface material that fully meets the above requirements. It is appropriate to match and choose according to different valve types and uses. There are several key points such as: often need to open and close, or in high-speed medium, the sealing material of flanged gate valve used here should be specially marked with erosion resistance requirements, and if it contains solid impurities, the hardness should be selected The higher the sealing surface material, the better the durability.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Video of resilient seated gate valve: https://youtu.be/AI-LT1dy2sU

Related news/knowledge:
How to choose gate valve products
What is the material of the main parts of the butterfly valve?-(2)
Types and selection of electric valves
Prevention and treatment of valve corrosion

Commonly Used Seat Materials for Butterfly Valve

The valve seat is a detachable part inside the valve. Its main function is to support the valve core to be fully closed or fully closed, and to form a sealing pair. Under normal circumstances, the diameter of the valve seat is the size of the valve. The butterfly valve seat is made of a wide range of materials, but the commonly used materials include soft-seal EPDM, nitrile rubber (NBR), polytetrafluoroethylene (PTFE), and metal hard-seal hard alloy materials. kind. Let’s introduce them one by one below.

wafer type butterfly valve, EPDM seat (10)

wafer type butterfly valve, EPDM seat (10)

1. EPDM: Compared with other general-purpose rubbers, EPDM has great advantages.
①The cost performance is very high. Among the commonly used rubbers, EPDM has the lightest raw rubber density and can be filled in a large amount, reducing the cost of the rubber.
②EPDM material is resistant to aging, sun exposure, heat resistance, moisture resistance, and radiation resistance, and is suitable for weak acid and weak alkali media. Good insulation properties.
③The applicable temperature range can be as low as -40℃–60℃, and it can be used for a long time under the temperature condition of 130℃.
2. Nitrile rubber (NBR): oil resistance, heat resistance, abrasion resistance and good water resistance, air tightness and excellent bonding properties. It is widely used in petroleum pipelines. The disadvantage is that it is not resistant to low temperature, ozone, poor insulation performance, and general elasticity.
3. Polytetrafluoroethylene (PTFE): A fluoroplastic, this material has strong resistance to acids, alkalis, and various organic solvents. At the same time, the material is resistant to high temperatures and can be used continuously at 260°C, and the maximum use temperature can reach 290-320°C. The emergence of PTFE has successfully solved many problems in the chemical, petroleum, pharmaceutical and other industries.

Fluorine lined butterfly valve-PTFE-WAFER (8)

Fluorine lined butterfly valve-PTFE-WAFER (8)

4. Metal hard seal (hard alloy): The material of the metal hard seal valve seat has very good high temperature and high pressure resistance, corrosion resistance, wear resistance and other characteristics, which makes up for the defects of soft seal material that is not resistant to high temperature and high pressure. However, the hard seal material has high requirements on the processing technology. The only disadvantage of the metal hard seal valve seat is that the sealing performance is poor, and leakage will occur after a long time of operation.

TH Valve is a professional manufacturer of butterfly valvegate valvecheck valveglobe valveknife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Related news/knowledge:
Valve seat sealing (TH-VSE)
What is the difference between lining and vulcanized valve seat?
What is the material of the main parts of the butterfly valve?-(2)
The chemical composition, characteristics and applications of rubbers