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Requirements of various sealing materials for pneumatic gate valves

November 17, 2021

This article would like to discuss with you some of the material requirements of pneumatic gate valves, including the

pneumatic gate valve (3)

material of the valve body, stem, stem bushing, nut, sealing surface and packing of the pneumatic gate valve. Each of them is an important component to ensure the good sealing performance of the valve. The quality of the sealing is the main criterion for evaluating the quality of the valve. Let’s share the standard requirements of various materials for pneumatic valves.
Let’s take a look at the valve body, valve stem, nut and other requirements. The material of the valve body should be mainly ductile iron, and the grade and actual physical and chemical test data of the cast iron should be indicated. The stem material strives to be stainless steel, and large-diameter gate valves should also be stainless steel embedded valve stems. The material of the stem bushing should not be greater in hardness and strength than the stem, and will not form electrochemical corrosion with the stem and valve body under water immersion. The nut material is made of cast lead brass or cast aluminum bronze, and the hardness and strength should be greater than that of the valve stem.
Let’s look at the material of the sealing surface of the pneumatic gate valve. We know that different types of pneumatic valves will require different sealing methods and materials because they are applicable to different working conditions. The sealing material is mainly divided into soft seal and hard seal. The soft seal is mainly an elastic seal based on rubber and plastic, and the hard seal is a rigid metal-to-metal seal. Take the ordinary wedge-type soft-seal gate valve as an example. The manufacturer’s fixing method, grinding method, physical chemistry and sanitary inspection data of the valve plate lining material should be clearly explained. And mark the valve body, the sealing surface material and the valve plate sealing surface material. Their physical and chemical testing data, especially the hygienic requirements, anti-aging performance, and wear resistance of rubber. Take the rubber soft sealing gate valve as an example, usually use nitrile butadiene rubber and EPDM rubber, etc. It is strictly forbidden to mix with reclaimed rubber.
Finally, the valve shaft packing has a great relationship with the sealing performance of the gate valve. Many leaks are caused by improper use of fillers. Since the pneumatic valves in the pipe network are usually opened and closed infrequently, the packing is required to be inactive for several years, the packing does not age, and the sealing effect is maintained for a long time. Therefore, the packing cannot be too tight or too loose. The valve shaft packing should also have a good sealing effect when it is subjected to frequent opening and closing. If the packing needs to be replaced, the pneumatic valve design should consider measures that can be replaced under water pressure. Therefore, the valve shaft packing is not to be replaced or not replaced for more than ten years.

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

Precautions for the use of triple eccentric metal seated butterfly valve

November 16, 2021

Triple eccentric hard-sealed butterfly valves are generally metal seated butterfly valves, which have an eccentric metal sealing structure. Sealing forms include metal-to-metal sealing, stainless steel plate and graphite composite plate sealing ring to metal sealing, etc. The driving methods are mainly electric, manual, turbo rod transmission,

D673H-16C-stainless steel pneumatic triple eccentric butterfly valve

pneumatic and so on. The triple eccentric hard-seal butterfly valve is very popular in the market. It maintains the advantages of the centerline butterfly valve and discards the disadvantage of the poor sealing performance of the metal seal. It is a more promising product in the market. Let’s take a look at the problems we need to pay attention to in use:
1. The triple eccentric hard sealing butterfly valve is a multi-layer soft and hard stacked sealing ring, which is also a very significant feature of the triple eccentric hard sealing butterfly valve. The seat sealing ring is composed of multiple layers of stainless steel sheets on both sides of the soft T-shaped sealing ring. When the valve plate is in the normally open state, the medium will form a positive scouring on its sealing surface, and the soft sealing tape in the metal sheet sandwich will directly affect the sealing performance after being scoured.
2. The valve will be restricted by the structural conditions, so the structure is not suitable for valves with a diameter below DN200, because the overall structure of the valve plate will be too thick and the flow resistance will be large.
3. The principle of the valve’s triple eccentric structure. The sealing between the sealing surface of the valve plate and the valve seat is to press the valve plate against the valve seat by the torque of the transmission device. It is a self-sealing property. That is, when the medium is flowing in the forward direction, the higher the medium pressure, the tighter the sealing and squeezing. However, in general, when the flow channel medium flows back, as the medium pressure increases, the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the seal will begin to leak.
Is there a solution to the inability to achieve two-way sealing? Butterfly valve manufacturers add an adjustment ring between the pressure plate and the valve seat to achieve a very ideal two-way hard seal. The sealing surface of the valve plate and the valve seat of the triple eccentric sealing butterfly valve is an oblique cone structure, and temperature-resistant and corrosion-resistant alloy materials are surfacing welded on the oblique cone surface of the valve plate. A structure in which the spring fixed between the pressure plate of the adjusting ring and the adjusting bolt of the pressure plate are assembled together. This structure effectively compensates for the tolerance zone between the shaft sleeve and the valve body and the elastic deformation of the valve stem under the medium pressure, and solves the sealing problem of the valve in the two-way interchangeable medium conveying process.
When the medium flows backward, the seal between the valve plate and the valve seat depends on the torque of the driving device to press the valve plate against the valve seat. With the increase of the reverse medium pressure, when the unit positive pressure between the valve plate and the valve seat is less than the medium pressure, the deformation energy stored by the spring of the adjusting ring after being loaded compensates for the tight pressure of the sealing surface of the valve plate and the valve seat Play the role of automatic compensation.
The triple eccentric hard seal butterfly valve adopts a soft T-shaped multi-layer stainless steel sheet on both sides to form a sealing ring. It has the dual advantages of metal hard and soft sealing, and has zero leakage sealing performance regardless of low temperature and high temperature. In the future, it may also replace gate valves and ball 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

Correct installation method of pneumatic gate valve

November 15, 2021

Good valve products also need correct use and maintenance to ensure a good working condition and service life of the product, and pneumatic gate valves are no exception. The working state of the pneumatic gate valve directly affects the operation of the engineering system. Pneumatic gate valves have been widely used in metallurgy,

pneumatic gate valve (3)

petrochemical and other fields. What we want to share today is how to properly use and maintain pneumatic gate valves to maintain their stability and reliability advantages in work. The details are as follows:
First of all, in order to ensure the normal operation of the pneumatic gate valve in the pipeline system and the safe operation of the system, we first need to do some work before the installation. For example, before installing a new valve, check whether the markings on the valve conform to the design requirements. At the same time, the basic error limit, full stroke deviation, return difference, dead zone, leakage rate, etc. are debugged. This is a new valve for pneumatic gate valves. If the pneumatic gate valve in the original system has been overhauled, in addition to completing the above work, the stuffing box and connections of the old gate valve should be checked for tightness. From the on-site use point of view, many problems in the operation of the system are often not caused by the quality of the valve itself, but because of the improper installation of the valve. This also includes factors such as the device environment, improper location and orientation of the device, or unclean piping.

Therefore, the following aspects should be paid attention to when installing the pneumatic gate valve:
1. Waterproof and cooling measures should be taken in the open air or high temperature places with strong sunlight. Where there is an earthquake source, stay away from the earthquake source or increase earthquake-proof measures.
2. Pneumatic gate valve can be installed tilted under special circumstances, but if the tilt angle is large or the weight of the valve itself is too large, it must be reinforced and supported.
3. The pipeline for installing the gate valve should not be too high from the ground. If the pipeline height exceeds 2m, a platform should be set up as far as possible to facilitate the operation of the handwheel and maintenance.
4. Before starting the valve for the first time, the pipeline must be cleaned to remove dirt and welding slag. Because if impurities in the pipeline pass through the valve with the medium at high speed, it is easy to cause damage to the sealing surface and cause leakage. After installation, the valve should also be cleaned to prevent impurities from getting stuck in the valve body. Remember to restore the original neutral position after using the handwheel mechanism.
5. The installation position of the pneumatic gate valve must meet the process requirements. In order to facilitate the later maintenance, it is better to add a bypass line to the valve, which is to continue the production during the maintenance process.
6. The electrical part of the pneumatic gate valve should be implemented in accordance with the construction requirements of the relevant electrical equipment. This should be communicated more with the manufacturer, strictly in accordance with the manufacturer’s technical requirements.
7. The reducer of the actuator of the pneumatic gate valve should be lubricated after disassembly and repair. Generally, low-speed motors should not be disassembled, washed and refueled. After the motor is assembled, check whether the valve position conforms to the valve position opening indication.
The above are some precautions before, during, and after installation of electrical gate valves, which have a very important impact on the service life and use effect of the gate valve, and we need to pay attention to it. For more information about gate valves, please contact Tanghai online customer service for professional answers.

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

How to extend the service life of stainless steel metal seated butterfly valve

November 12, 2021

In general, we are most worried about the problem of stainless steel metal seated butterfly valves is rust. This is the common concern of the majority of users for metal products. In fact, stainless steel material itself is not easy to rust, but stainless steel materials are also divided into five categories, such as ferritic stainless steel, martensitic stainless steel, austenitic stainless steel, austenitic-ferritic stainless steel and precipitated carbide stainless steel. The

D673H-16C-stainless steel pneumatic triple eccentric butterfly valve

austenitic stainless steel has good corrosion resistance after normal heat treatment and will not rust easily. If the stainless steel butterfly valve rusts in normal use, it is mostly due to the precipitation of carbides along the grain boundary in the material to form a chromium-depleted zone, which causes the stainless steel hard-seal butterfly valve to rust.
Let’s take a look at what specific maintenance methods we should maintain during use in order to effectively avoid corrosion of the stainless steel metal seated butterfly valve and prolong its service life:
1. The stainless steel metal seated butterfly valve should be cleaned frequently during use, and the transmission device should be maintained and lubricated. Frequently troubleshoot faults in order to find faults and clear them in time.
2. The packing should be evenly packed and the cover should be tightened to prevent the medium from leaking from the packing for a long time and rust.
3. Pay attention to the connection method and direction of the valve to prevent leakage and erosion caused by misalignment.
4. The stainless steel metal seated butterfly valve is only used for adjustment, not fully open or fully closed, because the structural characteristics of the butterfly valve are not suitable for truncation, which will cause accelerated wear of the sealing surface.
5. Valves that have not been put into use for a long time should also be checked regularly to clean up dirt in time. Both ends of the butterfly valve channel should be closed to prevent long-term air oxidation. The product should be placed in a ventilated and dry place, not stacked or stored in the open air.
6. Eliminate the dirt on the valve parts before installation, carefully check the pressure of the valve mark to see if the diameter meets the requirements for use, and eliminate the defects caused by the transportation process.
7. The product switch must use the equipped hand wheel or electric or pneumatic device. Do not use external tools to cause damage to the valve. The handwheel butterfly valve is turned clockwise to close, otherwise it is open.
For stainless steel metal seated butterfly valves to be used for a long time, it is important from product selection to post-maintenance. Choosing a trustworthy brand is the first step, and maintenance is the continuation of quality. Of course, good manufacturers will also have more guarantees after sales. If users do not understand maintenance or have any questions or questions, they can directly contact the manufacturer for professional assistance. Tanghai Valve solemnly promises to pay two for each failure within two years. Is your trustworthy butterfly valve manufacturer.

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

Structure and applicable working conditions of electric butterfly valve

November 10, 2021

Electric butterfly valve is one of electric valve and electric regulating valve. There are mainly flange type electric butterfly valve and wafer type electric butterfly valve, which are classified according to the connection method of electric butterfly valve. The electric butterfly valve is usually composed of a quarter-stroke electric actuator and a butterfly valve through a mechanical connection, after installation and debugging.

D943H-16C-metal seated stainless steel electric triple offset butterfly valve

According to the action mode, electric butterfly valves are classified into on-off type and regulating type. The switch type is to directly switch on the power supply to complete the switching action by switching the positive and negative directions. Regulating type uses AC220V power supply as power and receives 4-20mA signal preset by the industrial automation control system to complete the adjustment action. In various industrial automation production pipeline flow, pressure, temperature control, such as electric power, metallurgy, petrochemical, environmental protection, energy management, fire protection systems, etc., there are electric butterfly valves. Below we are going to take a look at the different working conditions applicable to different types of electric butterfly valves:
1. Wafer type electric butterfly valve, suitable for medium temperature ≤80～120℃, such as food, chemical, petroleum, electric power, textile, paper and other water supply and drainage, gas pipelines, used as flow adjustment and interception medium.
2. The soft-sealed electric butterfly valve has very good sealing performance. It can be made as a sanitary valve to achieve the effect of not polluting the medium.
3. The hard-sealed electric butterfly valve is made of hard alloy or stainless steel, which makes the sealing surface high in strength, hardness and wear resistance. Tanghai’s hard-sealed electric butterfly valve can be opened and closed continuously for more than 10,000 times without damage.
4. Flange electric butterfly valve, tightness, corrosion resistance, high temperature resistance and wear resistance have been firmly ensured, and it is suitable for high temperature and high pressure working conditions.
5. The rubber-lined electric butterfly valve is suitable for use in fresh water, sea water, salt, weak alkali, weak acid, natural gas, air, steam, oil, food and other media because of its good sealing performance.
6. The ventilation electric butterfly valve is made of the same material as the valve body and processed into a sealing ring. Its applicable temperature depends on the material selection of the valve body. The nominal pressure is ≤ 0.6MPa. It is usually used in industrial, metallurgical, environmental protection and other pipelines for ventilation and adjustment of medium flow.
There are still many uses for electric butterfly valves. For the selection of electric butterfly valves, you can also listen to the manufacturer’s suggestions. If you have the intention to purchase electric butterfly valves, you can contact us at any time. Tanghai will have professionals to give you reasonable suggestions according to your working conditions and assist you in purchasing practical electric butterfly valve products.

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 to consider when choosing a suitable resilient seated gate valve

November 9, 2021

The soft-seal /resilient seated gate valve is widely used. It is favored by users because it overcomes the product defects such as poor sealing and rust of ordinary gate valves. The soft sealing gate valve has a unique elastic seat seal to achieve a good sealing effect. The soft sealing gate valve is easy to open and close, reliable in sealing, good elastic

DIN-F4-BB-NRS-soft seated-wedge gate valve-DN100-PN16-copper holding ring-handwheel (3)

memory and long service life. It can be widely used as a regulating and intercepting device on the pipelines of tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, shipbuilding, metallurgy, energy system, etc.
To choose a resilient seated gate valve, you must first select the corresponding product according to the use environment, that is, the difference in the medium. Followed by some other technical parameters such as specifications, models and pressures. The correct selection can ensure the performance characteristics of the soft seal gate valve to the extreme, as well as the good operation of the pipeline, extend the service life of the pipeline, pump, and valve, and achieve the expected use effect of production. There are many types of rubber, but the best and economical ones are nitrile rubber and natural rubber. As an elastic sealing pair, they have high elasticity, high tensile strength, good abrasion resistance and drought resistance. Operating temperature range: about -60℃～80 ℃ Non-corrosive or general corrosive medium, can be water, gas, etc.
Soft seal gate valve, the inner cavity surface of the valve is not lined or covered with various rubbers, suitable for various working temperatures and fluid pipelines. Relatively speaking, as a resilient seated gate valve, rubber gate valves are not as resistant to high temperature and corrosion as fluorine-lined gate valves, which is a disadvantage of rubber seals. Fluorine-lined gate valve, also known as fluoroplastic-lined corrosion-resistant valve, is to place PTFE resin on the inner wall of steel or iron valve pressure-bearing parts or the outer surface of valve inner parts by moulding or inlaying, and use it in The unique performance of anti-corrosive medium is made into various valves.
When choosing a resilient seated gate valve, you must fully consider the main issues of medium, temperature, pressure, caliber, etc., to ensure that the use of the valve conforms to the working conditions and the characteristics of the product itself, and to maintain the service life.

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

Reasons and fixing for Leakage of the seat of the metal seated Gate Valve

November 8, 2021

The metal seated gate valve is well used in high temperature and high pressure media, but it also requires high quality due to the particularity of the working conditions, and the sealing problem that makes users most concerned about. What are the main reasons for leakage on the sealing surface? What measures can we take? The sealing

PN40-DN100 cast steel WCB gate valve photo

surface of the gate valve is the core part of the valve. There are four ways of leaking, namely, leakage of the sealing surface, leakage of the joint of the sealing ring, leakage caused by the falling of the closure and leakage of foreign objects embedded between the sealing surfaces. Today we mainly take a look at the leakage causes and solutions of the sealing surface.
1. The sealing surface of the metal sealing gate valve is unevenly ground and cannot form a tight line. Therefore, when the manufacturer grinds the sealing surface, grinding tools, abrasives, emery cloth, sandpaper and other objects should use reasonable grinding methods to be accurate. After grinding, they should be colored and checked. The sealing surface should be free of defects such as indentation, cracks, and scratches.
2. The top center of the connection between the valve stem and the closing part is suspended, incorrect or worn. In production, it is necessary to pay attention to the connection between the valve stem and the closure piece to meet the requirements. The top center should have a certain movable clearance, especially the axial clearance between the valve stem table and the closing part is not less than 2mm.
3. The valve stem is tortuous or the equipment is not right, which makes the closing part tilted or misaligned. If it is because of this situation, it is necessary to straighten and adjust in time to ensure that the valve stem, valve stem nut, closing parts, and valve seat are on a common axis after adjustment.
4. Unscientific selection of raw materials for the sealing surface or unsuitable working conditions of valve selection, resulting in corrosion, erosion and abrasion of the sealing surface. When selecting a valve or replacing the sealing surface, it should meet the working conditions.
5. Surfacing and heat treatment are not operated in accordance with the regulations. The defects such as wear due to low hardness, corrosion due to burning of alloy elements, and cracks due to excessive internal stress will also cause leakage of the sealing surface of the metal sealing gate valve. During the production process of the manufacturer, pay attention to the surfacing welding and heat treatment skills to meet the technical requirements of the compliance procedures and standards. After the sealing surface is processed, the inspection should be carried out to eliminate any shortcomings that affect the use.
6. The sealing surface is not tightly closed or the crevices appearing due to cold shrinkage after sealing, causing a phenomenon of eclipse. For high-temperature valves, some of the slits that show cold shrinkage after being closed should be closed again at a certain time after being closed to be used as a shut-off valve.
7. The metal sealing gate valve has reached the fully enclosed position and continues to exert excessive sealing force, including inaccurate use of long lever operation, and the sealing surface is crushed and squeezed. Therefore, whether it is a metal-sealed gate valve or not, all valves must be opened and closed in accordance with the operating specifications and signs given by the manufacturer. Strictly implement one-person operation or two-person operation according to the size of the valve handwheel, and whether levers within 500mm are allowed.
8. Excessive wear of the sealing surface causes the sealing pair to fail to fit perfectly. To prevent this situation, it should be adjusted in time, and the sealing surface that cannot be adjusted should be replaced.
The quality assurance of the metal seated gate valve is deeply related to the unevenness of the valve manufacturing quality, the quality of the working conditions, the quality of the operation, and the quality of maintenance. Only strict design and production of each link can ensure the safe operation of the valve without problems.

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 kind of centerline wafer butterfly valve is a high-quality butterfly valve

November 5, 2021

There are many types of butterfly valves. Today we mainly want to discuss the centerline wafer butterfly valve, which is our more common type of butterfly valve. It has a wide range of applications, and currently there are many

Wafer type butterfly valve with worm gear

manufacturers of soft-seal wafer type butterfly valves. However, the quality and appearance of these butterfly valve products are still very different. How do we judge the quality of butterfly valves when we purchase butterfly valves? What are the characteristics and elements of a good centerline wafer butterfly valve? Tanghai Valve also summarized some of the feedback from many customers on-site and shared it with all users and friends.

1. Many of the centerline wafer butterfly valves are soft-sealed butterfly valves, lined with fluorine or rubber. Therefore, the quality of the material of the sealing pair requires high standards. Such as rubber, high-quality rubber can be long-lasting and elastic to play a good sealing role. However, the low-quality rubber hardened in a short time, and the valve naturally stuck or leaked internally. Therefore, in many cases, the final quality of the product is determined by details that are easily overlooked. For another example, the shaft hole on the valve stem and the valve body must have bushings, and the function of the bushing is to limit the bending deformation of the valve stem under pressure. The sealing ring between the valve stem and the valve stem shaft hole should be designed reasonably to ensure that the medium will not penetrate between the valve stem and the valve stem shaft hole. The bushing and sealing ring on the valve stem should not increase the torque too much.
2. Small torque, long service life, and good adjustment performance are all evaluation criteria.
3. Good airtightness and guaranteed leakage level!

To achieve good quality of the centerline wafer butterfly valve, butterfly valve manufacturers need to strictly control from several aspects. One is from the structure, such as bearings, valve stems, actuator connections, etc. are well-made. The design between the valve seat and the valve body can be more rationalized. Second, the processing technology is brave to innovate on the basis of maturity and adapt to more working conditions. Material selection should be scientifically optimized to ensure that the performance of the material meets the characteristics of the medium. In the selection, professional manufacturers should also provide customers with mature application experience to assist in purchasing. Actively collect feedback from users on product quality and respond to market demand in a timely manner.
The centerline wafer butterfly valve is very popular in the market, but any product has its own weaknesses. The weak point of the centerline pair clip-on butterfly valve is that when it is opened and closed, the unavoidable valve plate and valve wall are scratched and worn, which affects the service life. Therefore, Tanghai Valve is also actively launching a new double eccentric soft sealing butterfly valve. Due to the ingenious design of eccentricity, the valve plate can quickly leave the valve wall when it is opened, the sealing surface is protected, and the service life is longer. Coupled with a soft seal, the sealing performance is better. Tanghai’s double eccentric soft-seal butterfly valve also received very good market response soon after its launch. You are welcome to inquire.

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 the characteristics of wafer butterfly valves and flanged butterfly valves

November 4, 2021

To find out what is the difference between the wafer butterfly valve and the flange butterfly valve, let’s take a look at the comparison of some characteristics of the wafer butterfly valve and the flange butterfly valve.

Wafer type butterfly valve with worm gear

The biggest difference is of course that the flanged butterfly valve has two more flanges, and the wafer type has two fewer flanges. Of course, the price is cheaper, and the price is about 2/3 of the flange. Flange butterfly valves are more reliable than wafer butterfly valves. Wafer butterfly valves are not as convenient as flanged butterfly valves in installation, because they need to be equipped with flanges, which can easily leak if they are not installed well.

From the perspective of specific working conditions, when selecting imported valves, use wafer-type butterfly valves as much as possible, which are light in weight and easy to replace. However, the length of the bolts of the wafer butterfly valve is longer, and the construction accuracy is higher. If the flanges on both sides are not aligned, the bolts will be subjected to greater pressure and the valve is prone to leakage. Under high temperature conditions, the bolts of the wafer butterfly valve may cause leakage after expansion, so if it is under high temperature conditions, the wafer butterfly valve is not suitable for large pipe diameters. In addition, wafer butterfly valves generally cannot be used at the end of the pipeline and downstream where it needs to be disassembled, because when the downstream flange is disassembled, the wafer valve will fall off. In this case, a short section must be made separately. For disassembly. The wafer butterfly valve has no flanges at both ends of the valve body, only a few guide bolt holes, and the valve is

Double flange butterfly valve (17)

connected with the flanges at both ends by a set of bolts/nuts. Compared with flanged butterfly valves, it is easier to disassemble. The cost of the valve is lower, but the disadvantage is that one sealing surface has a problem, and both sealing surfaces have to be disassembled. Regarding the blue butterfly valve, the above problem does not exist, and of course it has to pay a higher cost. But the cost will be higher.

The flange type butterfly valve has flanges at both ends of the valve body, which are connected with pipe flanges. The seal is relatively more reliable.
In addition to selecting the appropriate wafer butterfly valve or flange butterfly valve, attention should also be paid to the installation and maintenance of the butterfly valve. Because this is actually a place that can affect the selection of the valve outside of the specific purpose. Let’s take a look at the specific requirements below:
1. The valve disc stops at the closed position during installation.
2. Determine the opening position according to the rotation angle of the butterfly plate.
3. For the butterfly valve with bypass valve, the bypass valve should be opened before opening.
4. Ask professionals to install according to the manufacturer’s instructions, especially the heavy butterfly valve should be fixed.
5. The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, and the rotation angle is between 0° and 90°. When rotated to 90°, the butterfly valve is fully open.
The butterfly valve is used as a flow control, the main thing is to choose the size and type of the valve when purchasing. Butterfly valves are not only widely used in general industries such as petroleum, gas, chemical, and water treatment, but also used in cooling water systems of thermal power stations.

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

Can a gate valve be used for oxygen as the medium?

November 3, 2021

If the soft-sealed gate valve you purchase will be used for oxygen media, the manufacturer will usually advise you not to do so, and inform you that it is prohibited to use gate valves in oxygen media pipelines in the specification. What

Grooved resilient seated BB NRS wedge gate valve (4)

is the reason for this requirement? In fact, this is mainly related to the movement of the gate valve. The opening and closing method of the gate valve is the vertical movement of the gate. The gate and the valve seat will have strong friction and sparks may be generated. Since the contact between the valve plate and the valve seat is not continuous, it is also Static electricity may occur, which is very dangerous when used in flammable and explosive oxygen media pipelines. Let’s analyze it in detail below.

According to the characteristics of the gate valve: the gate valve should not be used to adjust the flow and pressure, otherwise, the sealing surface will wear out quickly and the tightness will decrease.

Moreover, the gate valve cannot be slowly opened for pressure adjustment, so the gate valve is not suitable for oxygen pipelines. One of the reasons why gate valves are forbidden in peroxygen pipelines is that the sealing surface of the gate valve will fall off from the sealing surface due to friction due to relative movement. Although this seems so trivial to us in normal times, in an environment of high-pressure pure oxygen, these small particles of iron powder are very easy to reach the ignition point and burn, and bury potential safety hazards.

Here, there is one more thing to pay attention to, that is, the safety hazards of the oxygen pipeline are not all to blame on the gate valve. When the pressure difference between the two sides of the valve is large, an explosion accident will also occur. Judging from the lessons learned from the accident, banning the gate valve is actually prohibiting the production of combustibles, and the purpose is the same as the regular removal of rust, degreasing, and banning oil. The need to further control the flow rate, do a good job of static grounding and other measures to eliminate the source of ignition, it has a great relationship with the valve material. Although copper-based alloy gate valves are more effective than cast iron and cast steel gate valves in preventing the production of combustibles, this does not mean that there are no hidden safety hazards. The reason is that there is no control of the fire source, and it is impossible to focus on the safety of the gate valve without controlling the source. The attention to operating pressure and the meticulous maintenance of the entire pipeline at all stages must tighten the nerve of safety, not just considering whether a gate valve is used.

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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