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The difference between knife gate valve and ordinary gate valve

September 27, 2021

There are many types of gate valves. Knife gate valve is one of them, also called knife gate valve. According to different structure types, gate valves can be divided into flat gate valves and knife gate valves. According to the different connection methods, knife gate valves can be divided into flange type; lug type and wafer type.

DIN-F5-BB-NRS-soft seated-wedge gate valve (10)

Compared with ordinary gate valves, the structure of the knife gate valve is simple, the opening and closing part is a gate, and the movement direction of the gate is perpendicular to the direction of the fluid. It is small in size, flexible in operation, and easy to install. It is more suitable for media with higher consistency and solid particles. As we can see from the name, the knife gate valve mainly relies on the knife-edge gate to cut off the medium. The gate has two sealing surfaces, forming a wedge shape. The gate can be made into an integral rigid gate; it can also be made into an elastic gate that can produce slight deformation and improve the sealing performance from the process. To sum up, compared with ordinary gate valves, knife gate valves mainly highlight the following product advantages:

1. The U-shaped gasket has a good sealing effect.
2. The full-diameter design makes the medium passability strong. At the same time, it can be easily installed, easily disassembled, and maintained under the working conditions of dirty media. The valve seal can be replaced without removing the valve, making the valve maintenance easier.
3. The gate with the function of the guillotine knife has good sluicing effect, can effectively squeeze off all kinds of debris in the medium, and solve the leakage phenomenon of the medium containing lumps, particles and fibers after the sluice is broken.
4. The knife gate valve has an ultra-short structure length, small size, small flow resistance, light weight, material saving, and small effective space.
Although the price of knife gate valve is about 20% higher than that of ordinary gate valve, its better performance has been generally recognized by the market, and it has quietly boarded the list of the most popular product series of Tanghai Valve. Through more than 20 years of research and production of valve technology, Tanghai Valve has senior production experience and advanced technical level, has a formal and modern production base, and has stably provided a large number of products for the knife gate valve market with a good reputation. If you need a knife gate valve, choose Tanghai 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

The difference between fluorine-lined butterfly valve and metal butterfly valve

September 17, 2021

Butterfly valve is one of the most commonly used valves in industrial pipelines. It has a simple structure and is mainly composed of a valve body, a valve stem, a butterfly plate and a sealing ring. It is easy to operate and can be equipped with different driving devices, such as turbine devices, electric devices, and pneumatics. Equipment, etc., to adapt to more working conditions. Compared with other valves of the same caliber, the overall cost of butterfly valves can be reduced by 1.5 to 2 times, which is economical and practical. Therefore, butterfly valves are most suitable for large-diameter valves and are often used in occasions with larger calibers and flow rates.

Fluorine lined butterfly valve-PTFE-WAFER (8)

According to the sealing form of the butterfly valve, we can divide the butterfly valve into two categories: soft sealing butterfly valve and hard sealing butterfly valve. The two butterfly valves with different sealing forms play different roles in the corresponding application pipelines, and it can even be said that there are big differences. Therefore, users should understand the difference between the two types of butterfly valves when choosing butterfly valves, and choose butterfly valve products reasonably and correctly according to their own operating conditions.
Among soft seal butterfly valves and hard seal butterfly valves, our most common and commonly used ones are soft seal fluorine lined butterfly valves and metal seated butterfly valves. The difference between fluorine lined butterfly valves and metal seal butterfly valves is that fluorine lined butterfly valves are generally used for flowing media containing corrosion. In the flexible pipeline, the sealing effect is excellent, and zero leakage can be achieved. However, due to its own material limitation, this type of butterfly valve is only suitable for use in normal temperature and pressure

triple offset butterfly valve-double flange- (4)

conditions. The metal-sealed butterfly valve can be used in working conditions with relatively high temperature and pressure, and it also has certain anti-corrosion performance, but its sealing performance is poor. Specifically, the difference between fluorine-lined butterfly valve and metal sealing butterfly valve is as follows:
1. The difference in structure:
Both sides of the metal seal butterfly valve seal pair are made of metal materials. As for the fluorine-lined butterfly valve of soft sealing butterfly valve, the butterfly plate and valve seat are both wrapped with PTFE;
2. The difference in sealing performance:
The sealing material of fluorine-lined butterfly valve is tetrafluoroplastic, which has excellent sealing performance, but it is prone to aging, abrasion and short service life. The sealing performance of the metal sealing butterfly valve is relatively poor, but it is corrosion-resistant, wear-resistant and has a long service life.
3. The difference in applicable working conditions:
The fluorine-lined butterfly valve has strong corrosion resistance and can be used in corrosive media pipelines. It is only suitable for normal temperature and pressure environments. The metal sealing butterfly valve has poor sealing performance and is generally used in high temperature and high pressure environments.
4. The difference in manufacturing process:
In terms of working principle, the difference between fluorine-lined butterfly valve and metal-sealed butterfly valve is not big. The difference in manufacturing process between the two is mainly in the valve seat. The seat material of the fluorine-lined butterfly valve is non-metallic PTFE and metal-sealed butterfly valve. The valve seat is made of metal materials, and the commonly used materials are copper alloy, chromium stainless steel, stellite alloy, nickel-based alloy and so on.

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

bellows globe valve vs ordinary globe valve

June 29, 2021

The difference and comparison between bellows globe valve and ordinary globe valve
The bellows globe valve is also called the bellows seal globe valve. Through automatic seam welding, a metal barrier is formed between the fluid medium and the atmosphere to ensure the design of zero leakage of the valve stem. Compared with traditional globe valves, it has the following advantages:

Globe valve (9)

1. The bellows globe valve has a long service life, reduces the number of maintenance and lowers operating costs. The sturdy and durable bellows seal design ensures zero leakage of the valve stem and provides maintenance-free conditions.
2. The valve opening and closing torque is small, reducing labor intensity, and can drive any form of driving device, which is convenient for remote control.
3. The appearance is beautiful, the valve channel has a smooth streamline, and the flow resistance coefficient of the valve is reduced. It is a high-quality energy-saving product.
4. The outer seal of the valve adopts bellows seal and graphite, stainless steel gasket seal, the seal is reliable, and the sealing packing does not need to be replaced for long-term use. In industrial use, the leakage caused by the stop valve: high temperature, highly toxic, flammable and explosive, radiant medium, etc., not only pollute the environment, but also often cause significant personal and property losses. However, this type of valve is much safer and more stable, and strictly adopts foreign advanced standards in design and manufacturing.

Advantages and application of bellows globe valve The bellows globe valve has no leakage, and it is safer to be used in high-risk media. Ordinary globe valve is sealed with packing, the valve stem and packing will slide, and it is easy to leak at low temperature (spool).
The bellows cut-off valve uses a closed bellows that can be stretched and compressed to replace the packing seal, which can effectively prevent external leakage caused by packing loss. It is generally used for the transmission of highly permeable media, such as valves on hydrogen systems, as long as the bellows is not damaged, there is generally no leakage; while the general shut-off valve is sealed with packing, which is prone to leakage.
The opening or closing stroke of the valve stem of this kind of valve is relatively short, and it has a very reliable cut-off function. Also, because the change of the valve seat port is proportional to the stroke of the valve disc, it is very suitable for flow adjustment. Therefore, this type of valve is very suitable for use as a shut-off or adjustment and throttling.

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

The difference between carbon steel and cast steel

November 24, 2020

What is the difference between cast steel and carbon steel? First, steel is classified by chemical composition
(1) Carbon steel: a. Low carbon steel (C≤0.25%) b. Medium carbon steel (C≤0.25~0.60%) c. High carbon steel (C≤0.60%)
Steel is classified according to the forming method: (1) Forged steel (2) Cast steel (3) Hot rolled steel (4) Cold drawn steel. The so-called cast steel and carbon steel are just the names produced by the different classifications of steel.

What is the difference between forged steel valve and cast steel valve? Forging and casting are two different

flanges

processing techniques.
Casting: The molten liquid metal fills the cavity and cools. Pores are easy to produce in the middle of the workpiece.
Forging: It is mainly formed by extrusion at high temperature. Can refine the crystal grain in the part.
Forging: Use hammering and other methods to make a metal material in a plastic state into a workpiece with a certain shape and size, and change its physical properties.
Casting: The metal is heated and melted and poured into a sand mold or mold, and solidified into a utensil after cooling.
The difference in performance
During forging, the metal undergoes plastic deformation to refine grains.

What is the difference between a cast iron valve and a cast steel valve? The main difference between cast iron and cast steel valves is the carbon content, which directly affects the strength and plasticity of the steel. Carbon steel is also called carbon steel, an iron-carbon alloy with a carbon content of less than 2% WC. In addition to carbon, carbon steel generally contains a small amount of silicon, manganese, sulfur, and phosphorus. According to its purpose, carbon steel can be divided into three types: carbon structural steel, carbon tool steel and free-cutting structural steel. Carbon structural steel is divided into building structural steel and machine-manufactured structural steel. According to the carbon content, carbon steel can be divided into low-carbon steel (WC ≤ 0.25%) and medium-carbon steel (WC0.25%-0.6%) And high-carbon steel (WC>0.6%) According to phosphorus and sulfur content, carbon steel can be divided into ordinary carbon steel (higher phosphorus and sulfur), high-quality carbon steel (lower phosphorus and sulfur) and high-quality Steel (lower phosphorus and sulfur) Generally, the higher the carbon content of carbon steel, the higher the hardness and the higher the strength, but the lower the plasticity.
The full name of carbon steel is carbon structural steel. Cast steel valves are also carbon steel valves (there are also cast iron valves). They are just made by casting methods, while common steels are made by rolling. The ingredients are the same.

What is the difference between cast steel, cast iron and carbon steel in valve materials? Simply put, you first

lug type butterfly valve, ductile iron, center lined,

distinguish between iron and steel. Both steel and iron are alloys based on iron and carbon as the main additive element, collectively referred to as iron-carbon alloys.
The cast iron is smelted in an iron melting furnace to obtain cast iron (liquid), and the liquid cast iron is cast into a casting, which is called a cast iron.
What is the difference between cast steel and carbon steel. First, steel is classified by chemical composition
(1) Carbon steel: a. Low carbon steel (C≤0.25%); b. Medium carbon steel (C≤0.25~0.60%); c. High carbon steel (C≤0.60%).
Steel is classified according to the forming method: (For valves with different pressures, different materials are used.
Medium and low pressure valve, the valve body material is cast iron. For high-pressure valves, because of the large pressure, the valve body must be made of cast steel. Special valves may use various alloy materials and stainless steel.
It is said that carbon steel is only a kind of steel, and cast steel is a processing method of steel, not a concept.

What is the difference between carbon steel gate valve and cast steel gate valve. Many people think that carbon steel gate valves and cast steel gate valves are two kinds of materials.
1. The cast steel check valve and carbon steel check valve are check valves of the same material, both of which are made of WCB A216 carbon steel.
2. Cast steel check valve, because the valve body of WCB material is cast, so the name suggests, it is called cast steel check valve.
3. Carbon steel check valve, because the main material of WCB material is carbon steel, it is named carbon steel check valve.

The forging process of steel is different in processing form. Cast steel The steel used for pouring castings. A kind of casting alloy. Cast steel is divided into cast carbon steel, cast low alloy steel and cast special steel. Cast steel refers to a type of steel casting produced by casting methods. Cast steel is mainly used to manufacture some parts with complex shapes, difficult to forge or cutting and forming, but require high strength and plasticity. Forged steel: Forged steel refers to various forgings and forgings produced by forging methods. The quality of forged steel parts is higher than that of cast steel parts, can withstand large impact forces, and have plasticity, toughness and other mechanical properties.

What is the meaning of cast steel and carbon steel of the valve? What is the meaning of cast steel and carbon steel. Thank you. Carbon steel is represented by CS, but it is generally not mentioned in the case of cast steel. Detailed materials such as WCB, WCC, LCC, etc. will be stated.

The valve is a control component in the fluid conveying system. It has the functions of cut-off, regulation, diversion, prevention of reverse flow, stabilization, diversion or overflow and pressure relief. Valves used in fluid control systems, ranging from the simplest shut-off valve to the various valves used in extremely complex automatic control systems, have a wide variety and specifications.
Valves can be used to control air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. >>Cast steel has less carbon content, good toughness, and higher pressure and temperature resistance than cast iron. Cast iron valves are not suitable for diesel, sea water and acid media. Cast iron valves are cheaper. Their materials are obviously different, and they are used in different environments! The cost is also different. In short, the price is analyzed in detail, and the properties of various materials are different. Temperature resistant. Cast steel valves can withstand high temperatures, but cast iron valves cannot be used with water.

The difference between American, Germany and China standard valve

November 2, 2020

The difference between American standard valve, German standard valve and China standard valve

lug type butterfly valve, ductile iron, center lined,

(American Standard, German Standard, National Standard) The difference between the valves:
First of all, it can be distinguished from the standard codes of various countries: GB is the national standard, the American standard (ANSI), and the German standard (DIN). Secondly, it can be distinguished from the model. The valve model of the national standard is named according to the pinyin letter of the valve category. For example, the safety valve is A, butterfly valve, D, diaphragm valve, G, check valve, H, globe valve, J, throttle valve, L, drain valve, P, ball valve, Q, trap, S, gate valve, and so on. ,
There are no special specifications between American standard valves, German standard valves, and national standard valves. It is nothing more than the difference between production standards and pressure levels. The material of the valve body and internal parts are easy to say, it is nothing but cast iron, cast steel, stainless steel, etc. Taking the American standard as an example, the pressure level of the American standard ranges from 125LB to 2500LB (or 200PSI to 6000PSI), and the main standard is API, ANSI, commonly referred to as API, and ANSI valves are American standard valves; German standard valve pressures are usually PN10 to PN320. DIN standard; if the valve is flanged, the corresponding flange standard must be adopted. The world’s main valve standards are also the American Standard Petroleum Institute API standard, the American national standard ANSI, the German standard DIN, the Japanese standard JIS, the national standard GB, the European standard EN, and the British standard BS. ,
Simply put, American standard valves are valves designed, manufactured, produced and tested according to American standards. German standard valves are valves designed, manufactured, produced and tested according to German standards. The national standard valve is the valve designed, manufactured, produced and tested according to our country’s standard. The differences between the three are roughly as follows: 1. The flange standards are different; 2. The structural length is different; 3. The inspection requirements are different.
National Standard Valves American Standard Valves German Standard Valves (American Standard, German Standard, National Standard) Valve Standards: Chinese National Standards (GB) Chinese Ministry of Machinery Standards (JB) American National Standards (ANSI) American Petroleum Institute Standards (API) American Society for Testing and Materials Standards (ASTM) American Valve and Fitting Manufacturers Standardization Association Standards (MSS) Japanese Industrial Standards (JIS) German National Standards (DIN) French National Standards (NF) British National Standards, European Standards (BS, EN) Other National Valve Standards ( ГOCT, IEEE, UL)

Tianjin Tanghai Valve Manufacturing Co., Ltd. is one of the largest butterfly valve manufacturers in China. It was founded in 2006. Its predecessor was Tanghai Valve Manufacturing Factory. Now we have our own independent R & D, manufacturing, assembly and warehousing workshops; we have professional pre-sale and after-sale technical support and perfect services.

After 14 years of continuous development and innovation, the company now has a group of high-tech engineers, technicians and skilled production workers, advanced production technology, sophisticated manufacturing equipment, complete testing methods, in strict accordance with international standards and quality management system, formed A comprehensive quality control network.

Our products use advanced manufacturing technology, and strictly conform to API, DIN, BS, EN, ISO, GB and other international standards. The main products are butterfly valves, gate valves, check valves, globe valves, valve parts (Valve body, Valve disc, Valve shaft, Valve seat…), etc. Our products are widely used in various fields such as marine industry, shipbuilding, petrochemical, metallurgy, water treatment, fire fighting, water supply and drainage, etc. The company has won unanimous recognition and praise from customers with high quality and good reputation.

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 is machining accuracy, machining error, tolerance?

October 23, 2020

1. Machining accuracy: the degree to which the actual geometric parameters (size, shape and position) of the part after processing are in line with the ideal geometric parameters. The higher the degree of conformity, the higher the processing accuracy.
2. Machining error: the degree of deviation of the actual geometric parameters of the part from the ideal geometric

U-type-flange-butterfly-valve-2

parameters after processing is called the machining error. The magnitude of machining error indicates the level of machining accuracy, and machining error is a measure of machining accuracy.
3. Tolerance refers to the allowable error of the part processing clock.
What is the difference between them? “processing accuracy” and “processing error” are two different concepts for evaluating the accuracy of geometric parameters of parts. In the actual production, the method of controlling the processing error or the modern active adaptation processing method is used to ensure the processing accuracy.
Machining accuracy and machining error are described from different angles, but the size of the machining error is measured by the deviation of the actual measurement of the part, and the level of machining accuracy is measured by the tolerance level or tolerance value, and by the machining error To control the size. Generally speaking, the machining accuracy can only be guaranteed when the machining error is less than the tolerance.

The difference of cryogenic valve and ordinary temperature valve

September 17, 2020

Cryogenic valves, as the name implies, are valves that can work in cryogenic and cryogenic conditions. The operating temperature is demarcated. Valves with operating temperatures below -40°C are usually called cryogenic valves, which are mainly used for gas liquefaction, For separation, transportation and storage equipment, the operating temperature can reach below -270℃. Currently, there are butterfly valves, check valves, gate valves, globe valves, ball valves, and throttle valves.

In recent years, ultra-low temperature valves have been used more and more widely, and they are one of the

lug type butterfly valve, ductile iron, center lined,

indispensable important equipment in petrochemical, air separation, natural gas and other industries. The working medium is not only low in temperature, but most of them are toxic, or flammable and explosive. , And strong permeability, so it determines many special requirements for valve materials and design. It is not only required to work normally at the set temperature, but also to ensure the working performance at room temperature.

Compared with the normal temperature valve, the low temperature valve has a higher packing part and uses an extended stem. Its purpose is to reduce the heat transferred from the outside into the device; to ensure that the temperature of the stuffing box is above 0℃, so that the stuffing can work normally; to prevent the valve stem and the upper part of the valve cover at the stuffing box part from being too cold The parts are frosted or frozen.

The design of the long-neck bonnet is mainly the design of the neck length L. L refers to the distance from the bottom of the stuffing box to the upper surface of the upper sealing seat. It is related to the thermal conductivity of the material, the thermal conductivity area, the surface heat dissipation coefficient, and the heat dissipation area. , The calculation is relatively cumbersome, and it is generally obtained by experimental methods.

Ferritic stainless steel can be used when the temperature is higher than -100℃, austenitic stainless steel can be used when the temperature is lower than -100℃, copper alloy or aluminum alloy can be used for low pressure and small diameter valves, and the valve body should be able to withstand temperature changes sufficiently. The expansion and contraction, and the structure of the valve seat part will not be permanently deformed due to temperature changes.

The difference between globe valve and check valve

August 13, 2020

With the development of high-tech industry, various valves are often used in daily life. Today we will understand the difference between globe valves and check valves.

The difference between globe valve and check valve:
1. Check valve and stop valve are not the same thing, the difference between the two is mainly that the structure is

Globe valve (6)

very different.

2. The check valve is a one-way valve, which automatically prevents the fluid from flowing in the reverse direction, without a knob, and cannot artificially block the forward flow.

3. The stop valve has a knob, which can artificially control the forward flow. Due to its special structure, even if there is no artificial pipe valve, the fluid cannot flow in the reverse direction.

Globe valve:

The globe valve, also known as the shut-off valve, is a forced sealing valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to not leak. When the medium enters the valve from below the valve

lift-swing-check-valve-2

disc, the resistance that the operating force needs to overcome is the friction force of the valve stem and the packing and the thrust generated by the pressure of the medium. The force of closing the valve is greater than the force of opening the valve, so the valve stem The diameter of the valve must be large, otherwise the valve stem will bend failure.
working principle of globe valve:
The globe valve, also called the cut-off valve, is one of the most widely used valves. The reason why it is so popular is that the friction between the sealing surfaces is small during the opening and closing process, which is relatively durable, has a low opening height, and is easy to manufacture. , Easy maintenance, not only suitable for medium and low pressure, but also suitable for high pressure. The closing principle of the globe valve is to rely on the pressure of the valve stem to make the sealing surface of the disc and the sealing surface of the valve seat tightly fit to prevent the medium from flowing. Our country’s valve “Sanhua” once stipulated that the flow direction of the stop valve should be from top to bottom, so there is directionality when installing. The structural length of the stop valve is longer than that of the gate valve, and the fluid resistance is large, and the sealing reliability is not strong during long-term operation.

Check valve:

Check valve refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing back, also known as check valve, one-way valve, reverse flow valve, and back pressure valve. Check valve is a kind of automatic valve, its main function is to prevent the back flow of the medium, prevent the pump and drive motor from reversing, and the discharge of the container medium.

working principle of check valve:
Check valve refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself to prevent the medium from flowing back. It is also called check valve, one-way valve, reverse flow valve and back pressure valve. Check valve is a kind of automatic valve, its main function is to prevent the back flow of the medium, prevent the pump and drive motor from reversing, and the discharge of the container medium. The check valve can also be used to supply the auxiliary system whose pressure may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis).

Valve manufacturers recommend:
Tanghai Valve Factory is a technological enterprise that produces globe valves and check valves. It designs and produces according to your needs, and provides you with professional, high-quality, low-priced valve products. Welcome to call us for quotations.

The difference between one-way valve and check valve

August 4, 2020

One-way valve means that the fluid can only flow along the water inlet, and the medium at the water outlet

double-wing-check-valve-3

cannot return. Used in hydraulic systems to prevent reverse flow of oil or pneumatic systems to prevent reverse flow of air. Check valve refers to a valve whose opening and closing parts are circular discs and rely on its own weight and medium pressure to generate actions to block the back flow of the medium. It is an automatic valve.

There are two types of check valves: straight-through and right-angle. The straight-through check valve is installed on the pipeline with a threaded connection. Right-angle check valves have three forms: threaded connection, plate connection and flange connection. Hydraulic control check valve is also called lock valve or pressure maintaining valve. It is the same as check valve to prevent reverse flow of oil. However, when the oil flow is required to flow in the reverse direction in the hydraulic circuit, the oil pressure can be controlled to open the one-way valve so that the oil flow can flow in both directions. The hydraulic control check valve adopts a conical valve core, so the sealing performance is good. When the oil circuit is required to be closed, this valve can be used as a one-way locking of the oil circuit to maintain pressure. There are two types of hydraulically controlled check valve to control oil leakage: internal leakage and external leakage. The internal drain type can be used in the oil circuit where the oil flow reverse outlet has no back pressure; otherwise, the external drain type is required to reduce the control oil pressure.

The check valve can also be used to supply the auxiliary system whose pressure may rise above the system pressure. Check valves can be divided into swing check valves (rotating according to the center of gravity) and lift check valves (moving along the axis). The function of this type of valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of the fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve flap act on the valve seat, thereby cutting off the flow.

One-way valve is a directional control valve in which air flow can only flow in one direction but not in the reverse direction. Its working principle is the same as the hydraulic one-way valve. Compressed air enters from port P, overcomes the spring force and friction force to open the one-way valve port, and the compressed air flows from P to A; when there is no compressed air at port P, it will be under the action of spring force and remaining force of port A (cavity) ; The valve port is in the closed state, so that the air flow from A to P is blocked. The one-way valve is used in occasions where the air flow is not allowed to flow in the opposite direction. For example, when the air compressor is inflating the air tank, a one-way valve is set between the air compressor and the air tank to prevent the air tank when the air compressor stops working. The compressed air in the air flow is returned to the air compressor. One-way valves are often combined with throttle valves and sequence valves to form one-way throttle valves and one-way sequence valves.

Check valves have a wide range of uses, and there are many types. The following are the check valves commonly used in water supply and heating:

1. Spring type: the liquid is from bottom to top, and the valve clack controlled by the spring is pushed up by the pressure. After the pressure disappears, the spring force pushes down the valve clack to seal the liquid back flow. Often used for check valves with small diameters.

2. Gravity type: Similar to spring type, it is closed by the gravity of the valve disc to prevent backflow.

3. Swing type: The liquid flows directly through the valve body, and the rotating disc on one side is opened by the pressure. After the pressure is lost, the disc relies on its own weight to return to the position, and the reverse liquid pressure closes the disc.

4. Plastic diaphragm type: Both the shell and the diaphragm are plastic. The general shell is ABS, PE, PP, NYLON, PC. The diaphragm includes silicone resin, fluororesin, etc.

In general, the check valve and the check valve are basically the same thing, but there are some differences. The check valve is a controlled check valve, and the check valve is a non-controlled check valve. That is to say, the one-way valve is used to provide pressure, and its main function is to maintain pipeline pressure. Although the check valve can also provide this function, it is mainly used to control the return of the medium and does not require pressure.

The above is about the difference between check valve and check valve. In fact, a check valve is only one type of valve, and a oneway valve is only a type of check valve. It is only a one-way open-close valve that prevents backflow of fluid in various pipelines or equipment. Check valves have a wide range of uses.

Difference between Soft seal gate valve and hard seal gate valve

July 28, 2020

Soft seal gate valve and hard seal gate valve are two major categories in the gate valve series. Hard seal and soft seal can sometimes compensate for each other, and

13 gate-valve-5

sometimes they are independent of each other. So what is the relationship between soft seal gate valve and hard seal gate valve? What are the main differences? Next, the editor of Tanghai Valve will solve these mysteries for everyone.

1. Sealing material

Soft seal gate valve: the seal pair is made of metal materials on one side and elastic non-metallic materials on the other side, which is called “soft seal”. This kind of seal has good sealing performance, but it is not resistant to high temperature, easy to wear, and has poor mechanical properties.

Hard seal gate valve: The two sides of the seal pair are made of metal materials or other harder materials are called “hard seals”. This kind of seal has poor sealing performance, but has high temperature resistance, abrasion resistance and good mechanical properties.

2. Structure mechanism

The hard seal gate valve is a seal between metal and metal, and the sealing ball and valve seat are both metal. Machining accuracy and craftsmanship are more difficult, and are generally used in high pressure, usually above 35MPa. The soft seal gate valve is a seal between metal and non-metal, such as nylon\tetrafluoroethylene, and the manufacturing standards are the same.

3. Equipment selection

The selection of soft and hard seal gate valves is mainly based on the process medium, temperature and pressure. Generally, the medium contains solid particles or wears or the temperature is higher than 200 degrees. It is best to use hard seals. Valves with a diameter greater than 50 have a larger pressure difference and consider opening the valve torque. , When the torque is large, the fixed hard-seal ball valve should be selected, and its sealing level can reach 6 regardless of the soft or hard seal.

3. Conditions of use

The soft seal gate valve generally has a very high seal, while the hard seal can be high or low according to the requirements; the soft seal needs to be fireproof, because the material of the soft seal will leak at high temperatures, while the hard seal does not have this problem; Seals can generally be made at very high pressures, but soft seals cannot; soft seals cannot be used in some situations due to the problem of the flowing medium. Finally, hard seal valves are generally more expensive than soft seals. As for manufacturing, there is little difference between the two, mainly the difference between the valve seat, the soft seal is non-metallic, and the hard seal is metallic.

Through the above introduction, I believe everyone can understand the difference between soft seal gate valve and hard seal gate valve. With the continuous development of China’s industrial market, it is necessary to understand the difference between soft seal gate valve and hard seal gate valve, which may not only affect Production efficiency may also greatly affect economic efficiency

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The difference between knife gate valve and ordinary gate valve

The difference between fluorine-lined butterfly valve and metal butterfly valve

bellows globe valve vs ordinary globe valve

The difference between carbon steel and cast steel

The difference between American, Germany and China standard valve

What is machining accuracy, machining error, tolerance?

The difference of cryogenic valve and ordinary temperature valve

The difference between globe valve and check valve

The difference between one-way valve and check valve

Difference between Soft seal gate valve and hard seal gate valve

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