Gate valves are widely used for all types of applications and are suitable for both above-ground and underground installation. Not least for underground installations, it is paramount to choose the right type of valve to avoid high replacement costs.
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Gate valves are designed for fully open or fully closed service. They are installed in pipelines as isolating valves, and should not be used as a control or regulating valves.
Operation of a gate valve is performed doing an either clockwise to close (CTC) or clockwise to open (CTO) rotating motion of the stem. When operating the valve stem, the gate moves up- or downwards on the threaded part of the stem.
The term Gate Valve originated from the words gatan, gap, gasse and gat, and implies a passage with a barrier, which can be hinged on one side, allowing it to be OPENED and CLOSED.
Some of the first known gate valves were used by the Egyptians, Greeks, and Romans when irrigating fields with water. These were simple wooden barriers, but they were well-suited for the requirements of the task.
In the 19th century, intensive development of gate valves moved quickly forward due to their increasing use in industrial operations. Over time the materials involved in their manufacture were improved and modified to suit different applications.
In addition, there were significant improvements in the efficiency of both internal and external sealing methods.
There is a different type of gate valve, such as:
Standard
Wedge Types
Solid Tapered Wedge
Solid Pliable Wedge
Double Disc type
Bellow Design
Cryogenic Design
Knife Plate
Hulk Plate
The closing feature is very good.
These valves can be used both ways in the circuit
They provide laminar flow, the pressure loss is minimum
They cannot be opened and closed quickly. To fully open or closed wheel or gearbox actuators, the shaft should be rotated as many as the full open revolution number. The full open revolution number is equal to the pitch
Assembly, start-up, and maintenance require large space.
In the fully closed position, the slow movement of the slide causes high flow speed. Due to vibration and collision, abrasion and deformation occur in the seating surfaces and the surface gets damaged from friction.
In systems where high-temperature changes irregularly, due to the load in the pipe at the valve end, leakages in gate valves occur.
At the place of operation, repair and maintenance of seating surfaces are difficult.
Socket or butt-welding end-gate valves in air, fuel gas, feedwater, steam, lube oil, and other systems are typical applications. Threaded-end gate valves may be used in air, gaseous, or liquid systems.
Concern for leakage from threaded connection can be addressed by seal welding the threaded connection or by using thread sealants, as appropriate. In low-pressure and low-temperature systems such as fire protection systems’ water piping or water distribution pipelines, flanged gate valves are commonly used.
Refrences:
https://www.avkvalves.eu
http://www.schuf.de
http://www.pipingguide.net
https://www.ksb.com
A gate valve is a wedge disc for opening and closing. The movement direction of the brake is required to be perpendicular to the direction of the fluid. It can be opened and closed completely, and cannot be adjusted or throttled. The gate valve is sealed by the contact between the valve seat and the gate. Usually, the metal material is sealed and welded to improve the wear resistance. The gate is divided into rigid and elastic gates and is widely used in chemical, petroleum, light industry, hospitals, environmental protection, etc.
How does a gate valve work? The opening and closing disc of the gate valve is the wedge disc, which has two sealing surfaces. The most commonly used mode is that the two sealing surfaces of the gate valve form a wedge. The wedge angle depends on the valve parameters, which is usually 5°, and is 2°52' when the medium temperature is not high. The gate of the wedge gate valve can form a whole, which is called a rigid gate. It is possible to manufacture gates that can produce slight deformation so as to improve the manufacturability, and compensate for the deviation of the sealing surface angle during processing. This kind of gate is called an elastic gate. After the gate valve is closed, the sealing surface can only be sealed by the pressure of the medium. In other words, according to the media pressure, the sealing surface of the gate can be pushed into the other side to ensure the sealing of the sealing surface, which is called self-sealing. Most gate valves adopt the method of forced sealing.
1. The flow resistance is small. The media channel inside the valve is straight, and the flow resistance is small.
2. It is easier for it to do the opening action. Because compared with the shut-off valve, the movement direction of the gate valve is perpendicular to the direction of the medium flow, whether it is open or closed.
3. High and long opening and closing time. The opening and closing stroke of the gate is relatively large, and the elevator is carried out by screws.
4. Water hammer is not easy to occur.
5. The two sides of the channel are symmetrical, and the medium can flow in any direction from both sides, which is convenient for installation.
6. The structure length (the distance between the two connecting end faces of the system shell) is small.
7. The gate valve has simple body shape, short structure, good manufacturing technology and wide application range.
8. The gate valve boasts compact structure, good valve rigidity, soft channel, small flow resistance, long sealing surface between stainless steel and hard alloy, long service life, PTFE packing, reliable sealing, light and flexible operation.
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The suitability of a valve for a specific application is defined by the materials used in relation to the transported fluid as well as its mechanical design. Here is Indelac Valve Selection Guide.
Valve Selection Table
The tables below can be used as a valve selection guide taking into consideration the state of material, its nature and the function of the valve.
Conveyed Fluid
Nature of Fluid
Valve Function
Type of Disc
Liquid Neutral (Water, Oil, etc) On/Off Gate Rotary ball Plug Diaphragm Butterfly Plug gate Control valve, modulating Globe Butterfly Plug gate Diaphragm Needle Corrosive (Acid, alkaline etc.) On/Off Gate Plug gate Rotary ball Plug Diaphragm Butterfly Control valve, modulating Globe Diaphragm Butterfly Plug gate Hygienic (Food, beverages, drugs etc) On/Off Butterfly Diaphragm Control valve, modulating Butterfly Diaphragm Squeeze Pinch Slurry On/Off Rotary ball Butterfly Diaphragm Plug Pinch Squeeze Control valve, modulating Butterfly Diaphragm Squeeze Pinch Gate Fibrous Suspensions On/Off, Control valve, modulating Gate Diaphragm Squeeze Pinch
Conveyed Fluid
Nature of Fluid
Valve Function
Type of Disc
Gas Neutral (Air, Steam etc) On/Off Gate Globe Rotary ball Plug Diaphragm Control valve, modulating Globe Needle Butterfly Diaphragm Gate Corrosive (Acid vapors, chlorine etc.) On/Off Butterfly Rotary ball Diaphragm Plug Control valve, modulating Butterfly Globe Needle Diaphragm Vacuum On/Off Gate Globe Rotary ball Butterfly
Conveyed Fluid
Nature of Fluid
Valve Function
Type of Disc
Solids Abrasive Powder (Silica, etc) On/Off, Control valve, modulating Pinch Squeeze Spiral sock Lubricating powder (graphite, talcum, etc) On/Off, Control valve, modulating Pinch Gate Spiral sock Squeeze
Valve Type Pros and Cons
Because everything is easier to understand with a table, here is another one summarizing pros and cons for the most common valves.
Valve
Advantages
Disadvantages
Butterfly
Quarter turn
Difficult to clean
Open port
Difficulty with slurries
Used with chemical or corrosive media
Throttling limited to low differential pressure
Compact, lightweight design
Potential for cavitation and choke
Available in large sizes
Unguided disc movement is affected by flow turbulence
Low pressure drop and high-pressure recovery
High coefficient of flow
Ball
Superior ease of operation
Poor throttling characteristics
Maintains and regulates high volume,
Difficult to clean, leads to contamination
high pressure, and high temp flow
Rugged construction and long service life
Low purchase and maintenance cost
Able to function without side loads
Permits inspection and repair of seats and seals without removing the valves' body from the line
Does not require lubrication
Diaphragm
Extremely clean
Can only be used in moderate temperature (-60 to 450ºF)
Leak proof seal
Can only be used in moderate pressures (approximately 300psi)
Tight shut-off
Cannot be used in multi-turn operations
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Easy maintenance
No industry standard face-to-face dimensions
Repairs can be made without interrupting pipe line
The body must be made of corrosive resistant material
Reduce leakage to the environment
Gate
Available in large sizes
Low pressure limitations
Can be used with slurries and viscous liquids
Slow open and close time
Used as a shut off valve
Erosion of the seat and disk can occur
Easy to maintain and disassemble
Poor throttling characteristics
Inexpensive
Difficult to repair
Inherently fire-safe (when used with a metal sheet)
Should not be used in sanitary applications
Bidirectional
Globe
Can be fast-acting
High head loss
Precise control
Large opening for disk assembly
Can be used in high-pressure systems
Heavier than other valves
Cantilevered mounting of the disk to the stem
Low coefficient of flow
Not good for clean or sterile applications
Pinch
Very Clean
Cannot be used in high temperature applications
Excellent drainage
Cannot be used in high pressure applications
Minimal turbulence
Cannot be used with gas media
Low airborne contaminants
Low maintenance
Low weight
Can be used in explosion-proof lines
Inexpensive
Once the right valve has been selected, it is time to select the right actuator! See link below to Indelac Actuator Selection Guide:
Gate valve refers to a valve whose closing member gate moves along the vertical direction of the channel axis. It is mainly used to cut off the medium on the pipeline, that is, it is used fully open or fully closed.
Generally, gate valves cannot be used to regulate flow. It can be applied to low temperature pressure or high temperature and high pressure, and can be used according to different materials of the valve. However, gate valves are generally not used in pipelines transporting media such as mud.
advantage:
①After the gate valve is opened, the medium channel inside the valve body is straight without any obstruction, and the flow resistance is very small.
② When opening and closing, the movement direction of the gate plate of the gate valve is perpendicular to the direction of medium flow, the pressure is small, and opening and closing is less labor-intensive.
③The height of the gate valve is large, so the opening and closing time is longer, and water hammer is not prone to occur.
④ Both sides of the gate valve channel are symmetrical, and the medium can flow in any direction on both sides, so the installation of the gate valve is very convenient.
⑤Short structural length, good manufacturing process, and wide application range.
⑥The structure length is relatively short.
shortcoming:
①The sealing surface of the gate valve is very easy to wear, which affects the service life of the valve and is more troublesome to repair.
② The structure of the gate valve is complex and the processing steps are cumbersome. In particular, the sealing surface on the gate seat is difficult to process and there are many parts, so it is more expensive.
③The overall size is large, it requires a certain amount of space to open, and the opening and closing time is long.
Butterfly valve is a valve that uses a disc-type opening and closing part to rotate back and forth about 90° to open, close and adjust the fluid channel.
advantage:
① Opening and closing is convenient, fast, labor-saving, has small fluid resistance and is frequently operated.
②Simple structure, small size, short length, small size and light weight. Suitable for large diameter valves.
③ It can be used for media with suspended solid particles. It can also be used for powdery and granular media depending on the strength of the sealing surface. It can be used for two-way opening, closing and adjustment of ventilation and dust removal pipelines, and is widely used in gas pipelines and waterways in metallurgy, light industry, electric power, and petrochemical systems.
shortcoming:
① The pressure and operating temperature range is small. Due to the limitations of the structure and sealing material of the butterfly valve, it is not suitable for use in high-temperature and high-pressure pipeline systems. The general working temperature is below 300℃ and below PN40;
②The sealing performance is worse than that of ball valves and globe valves, so it is used in places where sealing requirements are not very high.
The ball valve evolved from the plug valve. Its opening and closing part is a sphere, which is used to rotate 90° around the axis of the valve stem to open and close.Ball valves are mainly used on pipelines to cut off, distribute and change the flow direction of media. Ball valves designed with V-shaped openings also have good flow regulation functions.
advantage:
①Has the lowest flow resistance (actually 0);
② Because it will not get stuck when working (when there is no lubricant), it can be reliably used in corrosive media and low-boiling point liquids;
③ Complete sealing can be achieved within a larger pressure and temperature range;
④ Rapid opening and closing can be achieved. The opening and closing time of some structures is only 0.05~0.1s to ensure that it can be used in the automation system of the test bench. When opening and closing the valve quickly, there is no impact in the operation;
⑤The spherical closing piece can be automatically positioned at the boundary position;
⑥The working medium is reliably sealed on both sides;
⑦ When fully open and fully closed, the sealing surface of the ball and valve seat is isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface;
⑧With compact structure and light weight, it can be considered as the most reasonable valve structure for low-temperature medium systems;
⑨ The valve body is symmetrical, especially the welded valve body structure, which can withstand the stress from the pipeline well;
⑩The closing part can withstand the high pressure difference during closing. The ball valve with a fully welded body can be buried directly underground to prevent the valve internal parts from being corroded. The maximum service life can be up to 30 years. It is the most ideal valve for oil and natural gas pipelines.
shortcoming:
① Because the main valve seat sealing ring material of the ball valve is polytetrafluoroethylene, which is inert to almost all chemical substances, has a small friction coefficient, stable performance, is not easy to age, has a wide temperature range and excellent sealing performance comprehensive characteristics.
However, the physical properties of PTFE, including a high coefficient of expansion, sensitivity to cold flow and poor thermal conductivity, require that the valve seat seal must be designed around these properties.
Therefore, when the sealing material hardens, the reliability of the seal is compromised. Moreover, PTFE has a low temperature resistance level and can only be used below 180°C. Above this temperature, the sealing material will age. When considering long-term use, it is generally not used at 120°C.
② Its adjustment performance is worse than that of the stop valve, especially the pneumatic valve (or electric valve).
Globe valve: refers to a valve in which the closing member (valve disc) moves along the centerline of the valve seat. According to this movement form of the valve disc, the change of the valve seat opening is directly proportional to the valve disc stroke.
Since the opening or closing stroke of the valve stem of this type of valve is relatively short, and it has a very reliable shut-off function, and because the change of the valve seat opening is proportional to the stroke of the valve disc, it is very suitable for regulating flow. Therefore, this type of valve is very suitable for shutting off or regulating and throttling.
advantage:
① During the opening and closing process, because the friction between the valve disc and the valve body sealing surface is smaller than that of the gate valve, it is wear-resistant.
②The opening height is generally only 1/4 of the valve seat channel, so it is much smaller than the gate valve;
③ Usually there is only one sealing surface on the valve body and valve disc, so the manufacturing process is relatively good and easy to maintain;
④ Since its filler is generally a mixture of asbestos and graphite, it has a higher temperature resistance level. Generally, stop valves are used for steam valves.
shortcoming:
①Due to the change in the flow direction of the medium through the valve, the minimum flow resistance of the stop valve is also higher than that of most other types of valves;
②Due to the longer stroke, the opening speed is slower than that of the ball valve.
Plug valve: refers to a rotary valve with a plunger-shaped closing member. Through 90° rotation, the channel port on the valve plug communicates with or separates the channel port on the valve body to achieve opening or closing.
The shape of the valve plug can be cylindrical or conical. Its principle is basically similar to that of a ball valve. The ball valve is developed on the basis of the plug valve. It is mainly used in oil field mining and also in the petrochemical industry.
advantage:
① Used for frequent operations, opening and closing quickly and easily.
②The fluid resistance is small.
③Simple, relatively small in size, light in weight and easy to maintain.
④Good sealing performance.
⑤Subject to the installation direction, the flow direction of the medium can be arbitrary.
⑥No vibration and low noise.
shortcoming:
①The cover is too large, resulting in too much torque and insufficient flexibility.
②Affected by weight, the caliber size is limited.
③In actual use, if a large-size valve is used, a reverse cock structure must be used, which can easily affect the sealing effect.
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