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
BSTV Product Page
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
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: