gate valve Archives

What are the advantages of gate valves-resilient & metal seated

April 15, 2022

The gate valve has an opening and closing gate. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and cannot be adjusted or throttled. The gate

DN1000-DIN-F5-NRS gate valve-IS&Y (6)

valve is sealed by the contact between the valve seat and the gate plate. Usually, the sealing surface will be surfacing with metal materials to increase wear resistance, such as surfacing 1Cr13, STL6, stainless steel, etc. The gate has a rigid gate and an elastic gate. According to the different gates, the gate valve is divided into a rigid gate valve and an elastic gate valve.
Gate valve is a kind of valve with a large number of consultations every day. It is often used in water supply systems. The advantages of gate valves are:
1. Small flow resistance. The medium channel inside the valve body is straight, and the medium flows in a straight line. When the gate is fully opened, the internal resistance of the valve body channel is almost zero, and the flow resistance is very small.
2, opening and closing labor-saving. Whether the gate valve is open or closed, the movement direction of the gate is perpendicular to the flow direction of the medium, and the resistance of the gate to the lifting movement is also very small, and it is very labor-saving to open and close.
3. The full opening and full closing of the gate valve requires a long stroke, and the closing time is relatively long, which also makes the water hammer phenomenon less likely to occur.
4. The two sides of the gate valve channel are symmetrical, and the installation is not restricted by the flow direction of the medium, which is convenient for installation.
5. The shape is simple, the length of the structure is short, the manufacturing process is good, and the scope of application is wide.
6. Wide range of uses, gate valves are made of gray cast iron, ductile iron, cast steel, stainless steel, forged steel and other materials. Different materials can be used in different working conditions and environments, and have a wide range of applications.
Precautions for installation and use of gate valve
1. The handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited.
2. The double gate gate valve should be installed vertically (that is, the valve stem is in the vertical position and the handwheel is at the top).
3. The gate valve with bypass valve should open the bypass valve before opening (to balance the pressure difference between the inlet and outlet and reduce the opening force).
4. The gate valve with transmission mechanism shall be installed according to the provisions of the product instruction manual.
5. If the valve is frequently switched on and off, lubricate it at least once a month.
6. The gate valve is only used to fully open and fully close the medium on various pipelines or equipment, and is not allowed to be used for throttling.
7. For gate valves with handwheels or handles, auxiliary levers should not be added during operation (if the sealing is not tight, the sealing surface or other parts should be checked and repaired). Turn the handwheel and handle clockwise to close, and vice versa. The gate valve with transmission mechanism should be used in accordance with the stipulations in the product instruction manual.

gate valve (3)

The difference between a metal seated gate valve and a resilient seated gate valve:

What are the differences between hard sealing gate valves and soft sealing gate valves? This article will introduce you.

material difference:
The material of the hard sealing gate valve body is mainly cast steel, stainless steel and forged steel. The gate plate and internal flow channel seal are all made of Stellite alloy accumulation welding.
The material of the soft-sealed gate valve body is mostly cast iron, the valve plate is covered with rubber, the appearance of the soft-sealed gate valve, and the valve wall of the flow channel side are all sprayed with electrostatic powder. Not only is the appearance beautiful, but more importantly, the smoothness of the flow channel and the inner valve wall ensures that the rubber-lined gate will not be affected by the roughness of the inner valve wall when opening and closing.

difference in use:
Soft-sealed gate valve is suitable for non-corrosive gas-liquid medium at normal temperature (≤80℃). Such as water, air, oil, water treatment sewage and other pipelines. And has a good sealing effect, almost zero leakage can be achieved.
The hard-sealed gate valve is suitable for high temperature (≤425℃) with slightly corrosive gas and liquid. Such as steam, heat transfer oil, sewage, petroleum, chemical industry, metallurgy, pipeline. Can have a certain degree of wear resistance.

To sum up, the difference between a soft-sealed gate valve and a hard-sealed gate valve is that the sealing performance of the soft-sealed gate valve is better than that of the hard-sealed gate valve, but the temperature and wear resistance of the hard-sealed gate valve is better than that of the soft-sealed gate valve. Each has advantages and disadvantages.

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 resilient seated gate valve:

Structural characteristics and suitable medium of soft sealing gate valve

March 7, 2022

Structural characteristics of soft sealing gate valve:

Gate valves are mainly used in water-passing pipelines, but traditional gate valves may leak or corrode during use, which affects the performance of gate valves. As an upgraded product of traditional gate valves, the emergence of soft-sealed gate valves solves the problems of traditional gate valves that are easy to leak, easy to rust, and have poor elasticity. This article will give an introduction to the structural characteristics of soft sealing gate valves.

AWWA C509-C515-resilient seated wedge gate valve-DN80-150lb (4)

Soft sealing gate valve can be divided into dark rod soft sealing gate valve and rising rod soft sealing gate valve according to the structure. The working principle of the two structures is the same, the difference lies in the valve body structure, installation space, application range and so on. Details will be shared with you in future articles.

The structural characteristics of soft sealing gate valve are:
1. The valve body is made of ductile iron, which is lighter in weight and more conducive to installation and maintenance than traditional gate valves.
2. The valve body is coated with powder epoxy resin, which can play an anti-oxidation effect, prevent the valve body from being corroded, and is not easy to rust.
3. The traditional gate valve seat has grooves at the bottom. After the medium flows through, impurities in the medium such as stones, wood chips, iron chips and other debris will deposit and accumulate in the grooves at the bottom of the valve seat, which will cause the gate to fail to close completely over time. , causing leakage. The bottom of the valve seat of the soft-sealed gate valve is a flat-bottom design, and the medium containing impurities will not be precipitated and deposited when the valve body flows through, which ensures the sealing performance.
4. The gate of the soft-sealing gate valve is covered with high-quality rubber as a whole. The rubber and the gate are firmly attached, not easy to fall off, and have elastic memory, so that the gate and the valve seat can be tightly sealed to achieve good sealing performance. .

What medium is suitable for soft sealing butterfly valve:

In the introduction of the previous article, we learned that the sealing performance of the soft-sealed butterfly valve is superior, and it can achieve two-way sealing and zero leakage. The suitable media for soft seals are air, water, steam, various corrosive media, mud, oil, etc.
Butterfly valve can be divided into soft sealing butterfly valve and hard sealing butterfly valve according to the different sealing surface materials. The sealing surface refers to the valve seat of the butterfly valve. The sealing surface materials of the soft-seal butterfly valve we often see are EPDM, nitrile and PTFE. The three types of soft-sealed butterfly valves of different materials are also different in the applicable medium in the pipeline.

EPDM
Also called EPDM, codenamed EPDM. EPDM rubber is the most commonly used valve seat material for soft-seal butterfly valves, and it is also widely used. In the working environment of normal temperature and pressure, the use of EPDM valve seats has very good sealing performance. And EPDM rubber is resistant to ozone, aging, and has a long service life. The soft-sealed butterfly valve with EPDM as the valve seat material is suitable for fresh water, sewage, seawater and similar mud and other media containing impurities.

Nitrile
Nitrile-butadiene rubber, code-named NBR, has one of the biggest features of this material is its oil resistance is particularly good, in addition to a certain degree of wear resistance and heat resistance. The soft-sealed butterfly valve uses nitrile rubber as the sealing surface material, which can be used in oil pipelines and oily media. In addition, nitrile rubber is not suitable for medium such as fresh water, because it contains certain toxicity, which will cause harm to human health.

Teflon
PTFE is a fluoroplastic, code-named PTFE. The characteristics of PTFE are resistance to various acids and alkalis and various organic solvents; PTFE is used as the soft sealing partner of the valve seat material, which is mainly used in chemical industry, oil refining, chemical fiber, phosphate fertilizer, non-ferrous smelting, acid production, dyeing and other industries In the field, the applicable media are all corrosive strong acid and strong alkali media.
It can be seen from the above introduction that the soft sealing butterfly valve has a wide range of media and can be used in many fields. However, the soft sealing butterfly valve also has certain defects. Because of its own sealing material, it is not suitable for high temperature, high pressure and severe erosion conditions. In addition, in order to ensure the sealing performance of the soft-sealed butterfly valve, regular maintenance of its sealing surface should also be noted.

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 resilient seated gate valve:

Which valves are used for wastewater and sewage treatment

January 20, 2022

Which valves are used for wastewater and sewage treatment? The continuous increase of water pollution in my country has made the sewage treatment and regeneration industry receive unprecedented attention. In the sewage treatment pipeline system, the valve plays a very important role.

marine valve; butterfly valve; check valve; gate valve; manufacturer in China

Definition of sewage treatment
Sewage treatment: The process of purifying sewage in order to make it meet the water quality requirements for discharge into a body of water or for reuse. Sewage treatment is widely used in construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical treatment, catering and other fields, and is increasingly entering the daily life of ordinary people.

Sewage treatment classification
According to the classification of sewage sources, sewage treatment is generally divided into production sewage treatment and domestic sewage treatment. Production sewage includes industrial sewage, agricultural sewage and medical sewage, etc., while domestic sewage is sewage generated in daily life, which refers to the complex mixture of various forms of inorganic and organic substances, including: ① floating and suspended solid particles; ② glue shape and gel-like diffusion; ③ pure solution.
According to the quality of water pollution, there are two types of water pollution: one is natural pollution; the other is man-made pollution. At present, man-made pollution is the most harmful to water bodies. Water pollution can be divided into three categories: chemical pollution, physical pollution and biological pollution according to the different pollution impurities. The main pollutants are: (1) industrial wastewater discharged without treatment; (2) domestic sewage discharged without treatment; (3) farmland sewage with extensive use of chemical fertilizers, pesticides, and herbicides; (4) industrial waste and domestic garbage piled up by the river ; ⑸ soil erosion; ⑹ mine sewage.

Sewage treatment valve
Modern sewage treatment technology can be divided into primary, secondary and tertiary treatment according to the degree of treatment. Generally, the degree of sewage treatment is determined according to the water quality and the destination of the treated water. The valves used at each level are also different.
primary treatment
It mainly removes suspended solid pollutants in sewage, and most of the physical treatment methods can only complete the requirements of primary treatment. After primary treatment of sewage, BOD can generally be removed by about 30%, which does not meet the discharge standard. The primary treatment belongs to the preprocessing of the secondary treatment. Valves and their pipeline accessories are used: knife gate valve, triple eccentric butterfly valve, filter, etc.
secondary processing
It mainly removes colloidal and dissolved organic pollutants (BOD, COD substances) in the sewage, and the removal rate can reach more than 90%, so that the organic pollutants can meet the discharge standard, and the suspended solids removal rate can reach 95%, and the effluent effect is good. The valves used are soft-sealed butterfly valves, gate valves, ball valves, check valves, etc.
tertiary treatment
Further treatment of refractory organic matter, nitrogen and phosphorus and other soluble inorganic matter that can lead to eutrophication of water bodies. The main methods are biological denitrification and phosphorus removal, coagulation sedimentation, sand filtration, activated carbon adsorption, ion exchange and electrodialysis. The valves used are wafer butterfly valve, gate valve, ball valve, check valve, rubber soft joint, etc.

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: https://youtu.be/NuSZH_AJcwY
Video of triple eccentric butterfly valve: https://youtu.be/AkRwg2X1Wh0
Video of dual plate wafer check valve: https://youtu.be/XqRRI7o-LFI
Video of knife gate valve: https://youtu.be/vFSbTF_FGXM
Video of resilient seated gate valve: https://youtu.be/AI-LT1dy2sU

The role and application of gate valve

January 7, 2022

This article introduces you to the function of gate valve, and then understands the purpose of gate valve. The gate valve is a very important control component on the pipeline that transports the fluid medium. The structure of the gate valve is composed of a valve body, a valve cover, a valve stem, a gate plate, a sealing ring, and a driving device. The driving device is usually a hand wheel, and it can also be equipped with a pneumatic or electric actuator.

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

The gate of the gate valve is a disc shape, and the valve stem is driven to realize the opening and closing of the valve. The movement direction of the valve stem and the gate is perpendicular to the valve body passage and the direction of fluid flow in the pipeline. The gate valve has only two states, fully open and fully closed, so it can only be used to cut off the flow of the medium in the pipeline, and cannot adjust the flow rate. In addition, when the gate valve is opened and closed, the stroke distance of the gate is long. Although the opening and closing is labor-saving, it takes time. Therefore, the function of the gate valve is very suitable for use in pipelines that do not need to be opened and closed frequently, and used as a cut off or connected to the circulating medium in the pipeline.
The gate of the gate valve has two sealing surfaces. When the gate valve is closed, the sealing surface of the gate can be pressed against the seat on one side by the pressure of the medium to achieve sealing, which is self-sealing. The gate is basically a forced sealing type, that is, when the gate valve is closed, it needs to rely on the external force of the medium to force the gate to the valve seat to ensure the sealing performance of the sealing surface of the gate valve.
Gate valves can be divided into open-stem gate valves and concealed-stem gate valves according to their structural form. The functions of the two structural forms of gate valves are not much different, and the more difference lies in the use environment.
1. The stem of the rising stem gate valve is exposed, and the opening and closing state of the valve can be observed intuitively when the valve is opened and closed, so as to avoid misoperation. But also because the valve stem is exposed, the height of the rising stem gate valve, which is originally large in height, is even greater. Therefore, the rising stem gate valve is suitable for use in places that require a lot of operating space, and is not suitable for working conditions with narrow space.
2. The valve stem of the concealed stem gate valve is inside the valve body, so the on-off state of the valve cannot be directly observed, and another indicating device is required. However, because the valve stem is in the valve body, the volume of the dark-stem gate valve is smaller than that of the open-stem gate valve, and it is more suitable for use in occasions where the operating space is small and the location is limited and the pipeline is dense.
When the gate valve is fully opened, there is no obstruction when the medium flows through the inside of the valve body passage, and the flow resistance is almost zero. In addition, the valve body channel of the gate valve is symmetrical on both sides, the medium can flow in both directions, and it is not affected by the flow direction of the medium during installation. The gate valve has a wide range of applications due to its good manufacturing process. Gate valves have a wide range of uses, and are widely used in water conservancy systems, water supply and drainage systems, as well as petroleum, chemical, electric power, urban construction, and fire protection industries.

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 resilient seated gate valve:

How many types of gate valves? gate valve classification

January 6, 2022

How many kinds of gate valves are there? Which gate valve is suitable for which occasion? How many kinds of gate valves are there?

Commonly used gate valves are as follows:

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

1. Gray iron gate valve: including gray iron open rod gate valve and gray iron dark rod gate valve, this gate valve is suitable for municipal construction, water treatment, water supply and drainage, water conservancy engineering and other fields.

2 ductile iron gate valve: usually for soft seal gate valve, and divided into exposed rod and hidden rod. This kind of gate valve is mainly used in sewage treatment, building fire control, water supply and drainage engineering and other municipal engineering pipeline.

Gray cast iron gate valves and ball valve gate valves are cast iron gate valves. These gate valves are mostly used in normal temperature and low pressure pipelines, and the medium used is mostly water.

3 carbon steel gate valve and stainless steel gate valve: these two kinds of gate valves are used in high temperature and high pressure pipelines, the use of medium for steam, oil and so on. Applications include petroleum, chemical, metallurgy and so on.

4. Knife gate valve: suitable for all kinds of fluid media such as pulp, mud, sewage, powder, syrup, coal pulp, ash, slag-water mixture, etc.

Knife gate valve (6)

The above are just a few common gate valves. In fact, gate valves are not only the above, according to the structure of gate valves, different standards, connection, drive, etc., can be divided into many types.

According to the structure:

1. Implicit stem gate valve: stem nut is placed inside the valve body, in direct contact with the medium, often fixed on the gate. Through the rotation of the stem, the stem nut drives the lubrication plate up and down to complete the opening and closing.

2. Plain stem gate valve: the stem trapezoidal thread is placed outside the valve body, on the upper part of the stem. By rotating stem nut, stem drives gate synchronous rise and fall, realize valve opening and closing, easy to identify the valve. On and off state to avoid misoperation.

3. Flat gate valve: the sealing face is parallel to the vertical center line, so the valve body is parallel to the sealing face on the gate. This valve is the most common type of double gate.

4. Wedge valve: the sealing face is at a certain Angle with the vertical center line, that is, the two sealing faces are wedge valves.

According to different standards: gb gate valve, American standard gate valve, German standard gate valve, Japanese standard gate valve.

According to the connection mode: flange gate valve, welding gate valve, threaded gate valve.

According to the pressure grade: high pressure gate valve, medium pressure gate valve, low pressure gate valve.

According to the driving mode: electric gate valve, pneumatic gate valve, manual gate valve.

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 knife gate valve:

Video of resilient seated gate valve:

How to choose the material of flanged gate valve seat

December 10, 2021

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)

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

Common leakage problems and remedies of resilient-seated gate valves

November 26, 2021

The resilient seated flange gate valve is an updated product of the gate valve, because the gate plate is wrapped by elastic materials such as rubber or PTFE, or the valve seat is made of elastic material. In short, one of the valve seat and the valve plate can be regarded as soft seal. The combination of soft and hard sealing can achieve zero leakage. And because the connection form is flange connection, hence the name. It is widely used in fluid pipelines such as

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

tap water, sewage, construction, petroleum, chemical industry, food, medicine, textile, electric power, shipbuilding, metallurgy, energy system, etc. The soft sealing flange gate valve is characterized by low fluid resistance, wide applicable pressure and temperature range, unlimited medium flow direction, and good sealing performance.
In procurement, the leakage inspection of resilient seated flange gate valves is always the first concern. understand the product’s tightness, we first understand which components of the gate valve are prone to leaks, so that we can achieve good prevention and remedial measures. details as follows:
1. Leakage occurs at the junction of the gate valve and the gate valve
If this happens, first check whether the connecting bolts between the gate valves are tightened. This is to ensure that the inner gasket ring is fully integrated with the flange sealing groove surface. If a leak has occurred here, you can check the bolts and nuts in order and tighten them to the compression seal ring. Finally, check the size and accuracy of the gasket ring and the flange sealing groove surface, whether there is a bit of corrosion, sand holes, sand holes or impurities, and corresponding repair welding, repair or cleaning according to the situation.
2. The valve cover is leaking
Valve cover leakage is usually caused by the leakage of packing seals. If there is such a problem with the seal, you can check the selection first. If the selection of the seal and the sealing groove do not match, it is easy to leak. This problem can be solved by replacing the sealing ring or repairing the sealing groove. The appearance of burrs, fracturing, twisting, etc. of the seals may also cause leakage and need to be replaced in time. Finally, check whether the sealing surface of each sealing groove is rough or have other defects. If there are defects, remove the defects or update the damaged parts. Special attention should be paid to the packing installation situation and the matching surface of the packing seal. To check the installation of these packings, it is found that the upper and lower packings are installed upside down and need to be removed and reinstalled according to the correct method.
3. Leakage on the surface of the valve body cavity
In this case, the valve body may have sand holes, sand holes and other casting defects during the casting process, which are difficult to be found before the pressure test. But once pressure is applied, leakage will occur in these places. This kind of problem is to be repaired, repaired or updated.
4. Leakage at the valve seat gate
This is also a relatively common leakage phenomenon. There are two cases of leakage of the sealing surface and leakage of the root of the sealing ring. We can start by checking the accuracy of the sealing surface. It is too rough and needs to be removed and reground. Secondly, check whether the sealing surface has defects such as pitting, indentation, blisters, cracks, etc., and pay attention to the replacement of the gate or valve seat. Sometimes some valve seats with compression springs will leak due to the weakening of the compression spring’s elasticity. In addition, attention should be paid to whether the T-shaped connection between the valve plate and the valve stem is too loose. If there is a slope, it should be adjusted to its better size immediately.
5. Leakage caused by the entry of debris
If foreign matter such as welding slag, iron filings, impurities enter the valve body, it will also cause the valve plate to close to the expected depth and cause leakage. In this case, the valve body must be removed and cleaned.
6. Leakage caused by improper installation of valve seat
Special tools should be used to install the valve seat. If the valve seat is not installed in place, leakage will occur.

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

Solution for accidental fall off of the valve plate of rising stem wedge gate valve

November 18, 2021

In the previous Tanghai valve knowledge, we have mentioned that if the working conditions are too bad or the gate valve purchased is from an unqualified small manufacturer, or for the rising stem wedge gate valve, the valve will suffer corrosion and wear during the opening and closing process. Or improper operation may cause the valve plate

rising stem gate valve-RS-BB OS&Y (3)

to be disconnected from the valve stem. Once this happens, it will undoubtedly be troublesome for the production pipeline and even cause huge losses. So, if this situation has already happened, how can we deal with it?
Generally speaking, if the valve cannot be opened after it has been closed, it can only be replaced after cutting it out of the piping system. This is mainly for the welding connection. If the gate valve cannot be cut out from the system, another connection process or device shutdown is required. Take the rising stem wedge gate valve as an example, the specific repair methods are as follows:

1. The valve plate falls off but cannot be cut out for processing
Under the condition of ensuring that the medium is sealed, the valve plate can be exposed by changing the assembly methods of the gland, valve stem, packing, etc., and then the valve stem and the valve plate can be restored by conventional methods. This is to ensure that the three seals of the valve can continue to be maintained. After the bonnet is disassembled, the wedge angle of the valve plate is in the friction angle domain, so no matter whether the two ends of the valve plate are under pressure or not, the valve plate will not squeeze out of the valve seat by itself under the self-locking condition.

2. The valve plate falls off, the handwheel can still be turned
(1) In this case, the valve plate can be pushed back to the valve seat to form a seal through the handwheel. Loosen the packing nut but not completely. Loosen the packing first, and do the same for all the nuts on the bolts on the valve cover in turn.
(2) Next, turn the handwheel in the closing direction. The valve stem should be in a state where it will not move anymore. The upper part of the valve cover is separated from the valve body as a whole to ensure that the valve plate and the valve seat are indeed sealed or only A small amount of medium leakage that affects construction treatment. At this time, completely unscrew the nuts on all bolts, remove the upper part of the valve cover and the valve stem, and the top of the valve plate in the valve seat is exposed. Then check the reason and solution of the valve plate falling off.
(3) If it is not for special conditions, welding is generally used to re-establish the connection between the valve stem and the valve plate. However, if it is flammable and explosive oil, gas and other media, it is very unsafe to weld directly in this way. In this case, the end of the valve stem can be taken out and processed into the special form required. During installation, the contact surface of the valve stem and the valve core is treated with a high-strength adhesive repair agent, or directly drilled at the top of the valve plate. Tapping is changed to threaded connection. Special attention is to be paid to the valve stem and bonnet during the repair, which must be installed on a vertical plane to maintain good neutrality, so as to avoid opening difficulties when restarting.
(4) The sealing gasket should be replaced according to the situation to prevent leakage after the sealing surface is put into use, and then part of the packing should be added to the stuffing box as needed, and the packing gland should be properly compressed.

The above method can be used to repair the exposed rod wedge gate valve in a very short time. The repair requires less manpower and short working hours. The cost is mainly for disassembly, welding, bonding or drilling. The construction and material costs can be controlled within 1,000 yuan. . Practice has proved that the above method will open and close normally after repairing the valve, avoiding the loss of production shutdown, and will reduce the direct and invisible property loss of the enterprise. For more details about rising stem wedge gate valves, please contact Tanghai Valve’s online customer service.

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

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

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

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