Advantages and disadvantages of gate valves

I hope experts who have research in this area can help complete it

A gate valve is a type of valve in which the closing element (gate) moves vertically along the center line of the passage. Gate valves can only be used to fully open or close a pipeline for shut-off purposes; they cannot be used for regulation or throttling. Globe valves are a type of valve with a wide range of applications; they are generally used as shut-off devices for diameters of DN≥50 mm. Sometimes, globe valves are also used for shut-off devices with much smaller diameters. The gate of such valves has two sealing surfaces. In the most common design, these two sealing surfaces are wedge-shaped, and the wedge angle varies depending on the valve parameters, usually being 50 degrees; it is 2°52’ when the temperature of the medium is not high. The gate of a wedge-type gate valve can be made as a single piece, known as a rigid gate ； It is also possible to create a gate plate that can undergo slight deformation, in order to improve its workability and compensate for any deviations in the angle of the sealing surface that occur during processing; such a gate plate is called an elastic gate plate. When the gate valve is closed, the sealing surface can rely solely on the pressure of the medium to achieve sealing – that is, the pressure of the medium is used to press the sealing surface of the gate against the valve seat on the other side, thereby ensuring a secure seal; this is what is known as self-sealing. Most gate valves use forced sealing; that is, when the valve is closed, external force is required to press the gate tightly against the seat in order to ensure the seal of the sealing surface. A gate valve in which the gate moves in a straight line along with the valve stem is called a lift-type gate valve (also known as a stem-type gate valve). Typically, a trapezoidal thread is present on the lift rod; through the nut at the top of the valve and the guide groove on the valve body, rotational motion is converted into linear motion, that is, the operating torque is transformed into an operating thrust. When the valve is opened, the flow path is completely unobstructed when the lift height of the gate equals 1:1 of the valve’s diameter; however, this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a reference point – that is, the position at which it can no longer be moved – and this is regarded as its fully open position. To account for locking due to temperature changes, it is common to turn the valve to its full-open position and then reverse it by 1/2–1 turn as the position for a fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (i.e., the stroke). Advantages of gate valves: (1) Low fluid resistance. Since the flow channel inside the gate valve body is straight, the direction of the fluid flow does not change as it passes through the valve, resulting in low fluid resistance. (2) The opening and closing torque is low, making the operation less strenuous; since the direction of movement of the gate during opening and closing is perpendicular to the flow direction of the medium, gate valves require less effort to operate compared to globe valves. (3) The flow direction of the medium is not restricted; it does not cause turbulence nor reduce pressure. The medium can flow in either direction through the gate valve, and this ensures proper functioning. It is particularly suitable for pipelines where the flow direction of the medium may change. (4) The structural length is shorter because the gate of a gate valve is placed vertically within the valve body, whereas the disc of a globe valve is placed horizontally within the valve body; as a result, its structural length is shorter than that of a globe valve. (5) Good sealing performance; the sealing surface suffers less erosion when fully open. (6) When fully open, the sealing surface is subject to less erosion by the working medium compared to a globe valve. (7) It has a relatively simple shape, good castability, and a wide range of applications. Disadvantages of gate valves: (1) The sealing surface is prone to damage. During opening and closing, relative friction occurs between the gate and the valve seat at the two sealing surfaces, which can lead to damage; this affects the sealing performance and service life of the seals, and maintenance is relatively difficult. (2) Long opening and closing time, large height: Since gate valves must be opened or closed completely, the gate moves over a large distance; opening requires sufficient space, resulting in a large overall size and high installation requirements. (3) Complex structure: Gate valves generally have two sealing surfaces, which adds difficulties to processing, grinding, and maintenance; there are many complex components, making manufacturing and maintenance challenging, and their cost is higher than that of globe valves. Bore contraction of gate valves: If the diameter of the passage inside a valve is not uniform (usually the diameter at the valve seat is smaller than that at the flange connection), this is referred to as bore contraction. Path contraction can reduce the size of components, thereby decreasing the force required to open and close them, while also expanding the range of applications for these components. But after the lumen constriction. The fluid resistance loss increases. Under certain working conditions in some industries (such as oil pipelines in the petroleum sector), valves with reduced bore diameter are not permitted. This is done, on the one hand, to reduce the pressure loss in the pipeline, and on the other hand, to avoid obstacles for mechanical cleaning of the pipeline resulting from a reduced diameter.

Another issue is that the solid-liquid ratio cannot be too high; if it is, precipitation will occur inside the valve, resulting in poor sealing. Such valves are significantly worse than other types of valves

The comrade on the third floor has provided a fairly comprehensive answer; thank you for sharing! :handshake

　 The operating element of a gate valve is a gate, whose movement is perpendicular to the direction of the fluid flow. A gate valve can only be opened fully or closed fully; it cannot be used for regulation or throttling. The gate has two sealing surfaces. In the most common type of gate valve, these two sealing surfaces are wedge-shaped; the wedge angle varies depending on the valve parameters, usually being 50 degrees, and it is 2°52’ when the temperature of the medium is not high. The gate of a wedge-type gate valve can be made as a single unit, known as a rigid gate ； It is also possible to create a gate plate that can undergo slight deformation, in order to improve its workability and compensate for any deviations in the angle of the sealing surface that occur during processing; such a gate plate is called an elastic gate plate. 　　Based on the arrangement of their sealing surfaces, gate valves can be divided into wedge-type gate valves and parallel-plate gate valves. Wedge-type gate valves can further be classified into single-gate type, double-gate type, and elastic-gate type ； Parallel plate gate valves can be divided into single-plate type and double-plate type. Based on the position of the valve stem threads, they can be divided into straight-through gate valves and concealed stem gate valves. 　　When the gate valve is closed, the sealing surface can rely solely on the pressure of the medium to achieve sealing – that is, the pressure of the medium is used to press the sealing surface of the gate against the valve seat on the other side, thereby ensuring a secure seal; this is what is known as self-sealing. Most gate valves use forced sealing; that is, when the valve is closed, external force is required to press the gate tightly against the seat in order to ensure the seal of the sealing surface. 　　A gate valve in which the gate moves in a straight line along with the valve stem is called a lift-type gate valve (also known as a stem-type gate valve). Typically, a trapezoidal thread is present on the lift rod; through the nut at the top of the valve and the guide groove on the valve body, rotational motion is converted into linear motion, that is, the operating torque is transformed into an operating thrust. 　　When the valve is opened, the flow path is completely unobstructed when the lift height of the gate plate equals 1:1 of the valve’s diameter; however, this position cannot be monitored during operation. In actual use, the apex of the valve stem is used as a reference point – that is, the position at which it can no longer be moved – and this is regarded as its fully open position. To account for locking due to temperature changes, it is common to turn the valve to its full-open position and then reverse it by 1/2–1 turn as the position for a fully open valve. Therefore, the fully open position of the valve is determined by the position of the gate (i.e., the stroke). 　　In some gate valves, the valve stem nut is located on the gate, and the rotation of the handwheel causes the valve stem to rotate, thereby lifting the gate. Such valves are known as rotary stem gate valves or hidden stem gate valves. 　　Working principle of manual gate valve: By rotating the handwheel, the thread connection between the handwheel and the valve stem is moved forward or backward, thereby lifting or lowering the valve disc connected to the valve stem, thus enabling opening and closing of the valve. Gate valves have the following advantages: 1. Low flow resistance. The medium flow channel inside the valve body is straight, allowing the medium to flow in a linear path with low flow resistance. 　　2. It is less labor-intensive to open and close. It is in comparison to globe valves, because whether it is open or closed, the movement direction of the gate is perpendicular to the flow direction of the medium. 　　3. Large height and long opening/closing time. The opening and closing stroke of the gate plate is large, and lowering is achieved through a screw. 　　4. Water hammer phenomenon is unlikely to occur. The reason is the long shutdown time. 　　5. The medium can flow in either direction, making installation easy. The channels on both sides of the gate valve are symmetrical. 　　6. The structural length (the distance between the two connecting end faces of the housing) is relatively small. 　　7. The sealing surface is prone to wear, affecting its service life. During opening and closing, the sealing surfaces of the gate and the valve seat rub against each other, and under the pressure of the medium, abrasion can occur, which affects the sealing performance and shortens the service life. 　　8. The price is relatively high. There are many contact sealing surfaces, making the processing complex; in particular, the sealing surfaces on the gate seat are difficult to machine, and there are numerous components involved. 　　It has a simple shape, a short structural length, good manufacturability, and a wide range of applications. 　　The disadvantages of gate valves are as follows: Erosion and abrasion easily occur between the sealing surfaces, making maintenance relatively difficult. 　　It has large external dimensions, requires space to open, and takes a long time to open and close. 　　The structure is relatively complex. 　　Based on the arrangement of their sealing surfaces, gate valves can be classified into wedge-type gate valve and parallel-plate type gate valve. The wedge-type gate valve can further be divided into single-gate type, double-gate type, and elastic-gate type ； Parallel plate gate valves can be divided into single-plate type and double-plate type. Based on the position of the valve stem threads, they can be divided into straight-through gate valves and concealed stem gate valves. 　　The following points should be noted regarding the installation and maintenance of gate valves: The handwheel, handle, and transmission mechanism must not be used for lifting, and impact is strictly prohibited. 　　Double-disc gate valves should be installed vertically (i.e., the valve stem is in a vertical position with the handwheel at the top). 　　For gate valves equipped with a bypass valve, the bypass valve should be opened first before opening the valve (to balance the pressure difference between the inlet and outlet and reduce the force required to open it). 　　Gate valves with belt drive mechanisms shall be installed in accordance with the provisions of the product instruction manual. 　　If the valve is used frequently for opening and closing, it should be lubricated at least once a month. 　　Structural features: For a long time, conventional gate valves used in the market have suffered from problems such as leakage and rusting. The elastic seat gate valves produced by our company, utilizing advanced European rubber and valve manufacturing technologies, overcome these defects associated with conventional gate valves. By taking advantage of the slight elastic deformation of the elastic gate plate, these valves achieve excellent sealing performance. They offer significant advantages such as easy operation, reliable sealing, good elastic memory, and a long service life. It can be widely used in pipelines for tap water, sewage, construction, petroleum, chemicals, food, pharmaceuticals, light textiles, electricity, ships, metallurgy, energy systems, etc., as regulating and shutoff devices. 　　Features of gate valves: Light weight: The body is made of high-grade ductile iron, resulting in a weight that is about 20%~30% lower than that of traditional gate valves, making installation and maintenance easier. 　　Flat-bottomed seat: Traditional gate valves often suffer from leaks due to the accumulation of foreign objects such as stones, wood pieces, cement, iron shavings, and debris in the grooves at the bottom of the valve after water is used for cleaning. This accumulation makes it difficult for the valve to close tightly. Gate valves with elastic seat seals feature a flat-bottom design similar to that of plumbing fixtures, which prevents the buildup of debris and ensures unobstructed flow of fluids. 　　Full rubber coating: The gate valve disc is covered with high-quality rubber on both the inner and outer sides. Europe’s top-tier rubber vulcanization technology ensures that the vulcanized disc maintains precise geometric dimensions; moreover, the rubber bonds firmly to the ductile iron disc, preventing it from coming loose and offering excellent elastic memory. Water Precision-cast valve body: The valve body is manufactured through precision casting, and its precise geometric dimensions ensure that the valve remains sealed without the need for any further machining. 　　Globe valves have the following advantages: 1. Low fluid resistance, with the sealing surface being less subject to abrasion and erosion by the medium. 　　2. It is easier to open and close. 　　3. The flow direction of the medium is not restricted; it does not cause turbulence nor reduce pressure. 　　4. It has a simple shape, a short structural length, good manufacturability, and a wide range of applications. 　　The disadvantages of gate valves are as follows: 1. Erosion and abrasion can easily occur between the sealing surfaces, making maintenance difficult. 　　2. It has large external dimensions, requiring sufficient space to open, and the opening and closing process takes a long time. 　　3. The structure is relatively complex. 　　Based on the arrangement of their sealing surfaces, gate valves can be classified into wedge-type gate valve and parallel-plate type gate valve. The wedge-type gate valve can further be divided into single-gate type, double-gate type, and elastic-gate type ； Parallel plate gate valves can be divided into single-plate type and double-plate type. Based on the position of the valve stem threads, they can be divided into straight-through gate valves and concealed stem gate valves. 　　The following points should be noted regarding the installation and maintenance of gate valves: 1. The handwheel, handle, and transmission mechanism must not be used for lifting, and collision with them is strictly prohibited. 　　2. Double-plate gate valves should be installed vertically (i.e., the valve stem is in a vertical position with the handwheel at the top). 　　3. For gate valves equipped with a bypass valve, the bypass valve should be opened first before opening the valve (to balance the pressure difference between the inlet and outlet and reduce the force required to open it). 　　4. Gate valves equipped with belt drive mechanisms shall be installed in accordance with the provisions of the product instruction manual. 　　5. If the valve is used frequently for opening and closing, it should be lubricated at least once a month. 　　Main standards for gate valves:
(1) GB12232-89 “General-purpose valve flanged iron gate valves”
(2) GB12234-89 “General-purpose valve flanged and welded steel gate valves”
(3) GB8486-87 “General technical specifications for gate valves, globe valves, ball valves, and check valves with internal thread connections”
(4) GB8465.1-87 “Basic dimensions for gate valves, globe valves, ball valves, and check valves with internal thread connections – Iron gate valves”
(5) JB/T53162-94 “Quality grading of gate valve products”
(6) JB/T5298-91 “Steel flat gate valves for pipelines”
(7) JB/Z243-85 “Procedures for static pressure life testing of gate valves”
(8) JB/TQ648-88 “Iron wafer-type flat gate valves”
(9) JB/T53200-94 “Quality grading of iron wafer-type flat gate valve products”
(10) JB/T53242-94 “Quality grading of steel flat gate valve products”

It can be compared with a stop valve, hehe. A stop valve – also known as a globe valve – has a plug-shaped valve disc as its closing element; its sealing surface is either flat or conical, and the valve disc moves in a straight line along the centerline of the fluid. The movement pattern of the valve stem can be of the lift-type (where the valve stem moves up and down while the handwheel does not move), or it can be of the lift-rotation type (where both the handwheel and the valve stem rotate and move up and down, with the nut located on the valve body). Stop valves are only suitable for full open and full closed positions; they cannot be used for regulation or throttling. 　　Globe valves are classified as valves with forced sealing; therefore, when the valve is closed, pressure must be applied to the valve disc to ensure that the sealing surface does not leak. When the medium enters the valve from below the valve disc, the resistance that the operating force must overcome consists of the friction between the valve stem and the packing, as well as the thrust generated by the pressure of the medium. The force required to close the valve is greater than that needed to open it; therefore, the diameter of the valve stem must be large, otherwise the valve stem may bend. In recent years, since the emergence of self-sealing valves, the flow direction of the medium in globe valves has changed to enter the valve chamber from above the valve disc. As a result, under the pressure of the medium, the force required to close the valve is smaller, while the force required to open it is greater; consequently, the diameter of the valve stem can be reduced accordingly. At the same time, under the influence of the medium, this type of valve is also more airtight. China’s regulations on valve design specified that for globe valves, the flow direction should always be from top to bottom. 　　When the globe valve is opened, the flow rate reaches its maximum when the opening height of the valve disc is 25% to 30% of the nominal diameter, indicating that the valve has reached its fully open position. Therefore, the fully open position of the stop valve should be determined by the travel of the valve disc. 　　Classification of globe valves 　　1. Based on the direction of the flow in the globe valve, they can be classified as: 　　1) Straight-through globe valves 　　2) Angle-type globe valves: In angle-type or Y-shaped globe valves, the flow channel within the valve body is at an angle to the main flow direction; this results in less disruption to the flow pattern compared to conventional globe valves, and consequently, the pressure loss across the valve is also lower. 　　3) Angle-type globe valve: In an angle-type globe valve, the fluid only needs to change direction once, resulting in a lower pressure drop across this valve compared to globe valves with conventional designs. 　　4) Plunger-type globe valve: This type of globe valve is a variant of the conventional globe valve. In such valves, the valve disc and seat are typically designed based on the plunger principle. The valve disc is polished to form a plunger that connects with the valve stem, and sealing is achieved through two elastic sealing rings fitted over the plunger. The two elastic sealing rings are separated by a collar, and the sealing rings around the plunger are pressed in place by the load applied to the valve cover by the valve cover nut. The elastic sealing ring can be replaced and is made from a variety of materials. This valve is primarily used for opening or closing, but it also comes with a specially designed plunger or special rings that allow for flow regulation. 　　2. Based on the position of the threads on the stem of the globe valve, they can be classified as: 1) Globe valves with upper-threaded stems: The threads on the stem of such globe valves are located outside the valve body. Its advantage is that the valve stem is not subject to erosion by the medium, making lubrication easier; this type of structure is quite commonly used. 　　2) Lower-threaded valve stem globe valve: The threads of the globe valve stem are located inside the valve body. In this type of structure, the valve stem threads are in direct contact with the medium, making them susceptible to erosion and unable to be lubricated. This type of structure is used in applications with small diameters and low temperatures. 　　Globe valves have the following advantages: 1. They have a simple structure, making them easy to manufacture and maintain. 　　2. The working stroke is small, and the opening and closing time is short. 　　3. It has good sealing performance, low friction between the sealing surfaces, and a long service life. 　　The disadvantages of globe valves are as follows: 1. High fluid resistance, and a large force is required to open and close them. 　　2. Not suitable for media containing particles, with high viscosity, or prone to coking. 　　3. The adjustment performance is poor. 　　According to the position of the valve stem thread, stop valves are classified into external-thread type and internal-thread type. Classified by the flow direction of the medium, there are straight-through type, direct-current type, and angular type. Based on their sealing mechanism, globe valves are divided into gland-sealed globe valves and diaphragm-sealed globe valves. 　　Structural forms of globe valves: The structural forms of the globe valve body include straight-through type, straight-flow type, and right-angled type. The straight-through type is the most common structure, but it experiences the greatest fluid resistance. DC flow has lower fluid resistance and is often used for fluids containing solid particles or those with high viscosity. Right-angle valve bodies are often forged and are suitable for globe valves with smaller diameters and higher pressures. 　　The following points should be noted regarding the installation and maintenance of globe valves: 1. Globe valves that can be operated via handwheels or handles can be installed at any position in the pipeline. 　　2. Handwheels, handles, and actuating mechanisms shall not be used for lifting purposes. 　　3. The flow direction of the medium should be consistent with the arrow indicated on the valve body. 　　Main standards for globe valves:
1. GB/T 12233-2006 “General valves – Iron globe valves and lift check valves”
2. GB/T 12235-2007 “General valves – Flanged steel globe valves and lift check valves”
3. JB/T53174-94 “Globe valves – Product quality grading”
4. JB/T53165-92 “High-pressure balanced globe valves”
5. GB/T 587-2008 “Marine flanged bronze globe valves”
6. GB/T 590-2008 “Marine flanged cast iron globe valves”
7. GB/T 8464-2008 “Valves with threaded connections – Iron and copper”
8. GB8465.2-87 “Gate valves, globe valves, ball valves, check valves – Basic dimensions – Iron globe valves”

Knowledge related to globe valves:
A globe valve is a type of valve in which the closing element (valve disc) moves along the center line of the valve seat. Based on this type of movement of the valve disc, the change in the valve seat opening is directly proportional to the stroke of the valve disc. Due to the relatively short opening and closing stroke of the valve stem in this type of valve, as well as its highly reliable shut-off function, and because the change in the valve seat orifice is proportional to the stroke of the valve disc, it is highly suitable for regulating flow rate. Therefore, this type of valve is very suitable for use in cutting off or regulating flow, as well as for throttling. The selection principles are as follows: 1. Globe valves are suitable for use in pipelines or devices handling high-temperature and high-pressure media. Such as in thermal power plants, nuclear power plants, and the high-temperature and high-pressure pipelines of petrochemical systems. 2. In pipelines where the requirement for convective resistance is not strict. That is, in places where pressure loss is not a major concern. 3. For small valves, needle valves, instrument valves, sampling valves, pressure gauge valves, etc. can be selected. 4. Suitable for use in systems with flow or pressure regulation, where high precision in regulation is not required, and in pipelines with a relatively small diameter, such as those with a nominal diameter of ≤50 mm. 5. In the production of synthetic fertilizers, high-pressure angular stop valves or high-pressure angular throttle valves with a nominal pressure of PN160 (16 MPa) or PN320 (32 MPa) are suitable for use with both small and large-scale fertilizers. 6. In the desiliconization units of the alumina Bayer process, as well as on pipelines prone to coking, straight-through globe valves or straight-through throttle valves with a separate valve body, removable valve seats, and cemented carbide sealing pairs are preferred. 7. In water supply and heating systems used in urban construction, for pipelines with a relatively small nominal diameter, globe valves, balance valves, or plunger valves can be used, such as in pipelines with a nominal diameter of less than 150 mm. The most obvious advantage is that, during the opening and closing process, the friction between the valve disc and the sealing surface of the valve body is lower than that in gate valves, resulting in better wear resistance. The opening height is generally only 1/4 of the diameter of the valve seat passage, so it is much smaller than that of gate valves. Usually, there is only one sealing surface on the valve body and the valve disc, which makes the manufacturing process simpler and facilitates maintenance. Nominal pressure or pressure class: PN1.0–16.0 MPa, ANSI CLASS 150–900, JIS10–20K. Nominal diameter: DN10–500, NPS 1/2–36”. Connection methods: flange, butt welding, threading, etc. Operating temperature range: -196°C–700°C. Actuation methods: manual, bevel gear drive, pneumatic, electric, hydraulic, pneumatic-hydraulic, electro-hydraulic. Valve body materials: WCB, ZG1Cr18Ni9Ti, ZG1Cr18Ni12Mo2Ti, CF8 (304), CF3 (304L), CF8M (316), CF3M (316L), Ti. By using different materials, it can be suitable for various media such as water, steam, oils, nitric acid, acetic acid, oxidizing media, and urea.

What is this? It’s contradictory. . After organizing it, didn’t you read it carefully? Take a look at the part regarding traffic adjustment – sometimes it says it’s possible and other times it says it’s not, which is misleading~~

It seems to have poor sealing properties; it tends to malfunction when used in media containing solids

Globe valves are on-off valves and are not recommended for use as control valves. Some heating companies use them as control valves due to milder winters, but they can only perform rough volume regulation. Linear regulation, quality regulation – requires specialized control valves. It is divided into static adjustment and dynamic adjustment.