Gate valves are known to many industries as these valves are used for various types of applications. Gate valves are also highly suitable for underground and above-ground installation. Aside from the argument between plug valves vs. ball valves, people are also intrigued by gate valves.
Gate valves are very in demand in the market today. To avoid unnecessary costs, it is best to get acquainted with gate valves and to know what types are for you to use.
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What Is a Gate Valve?
Gate valves are designed to be used for fully open or fully closed positions. They are used as isolating valves that are installed in pipelines. Gate valves are not advised to be used as regulating or control valves.
Gate valves are operated by making a clockwise rotating motion to open or close through a stem. The gate moves up and down as the valve stem is being operated on the threaded portion of the stem.
When there is minimum pressure loss, and if a free bore is needed, there is also a need to use gate valves. The flow of the fluid that passes through the gate valve is not blocked once the valve is fully open. This results in a very low-pressure loss. Gate valves are multi-turn valves that are operated by a threaded stem. When these valves are turned multiple times to be opened or closed, a water hammer is prevented.
Gate valves are used in almost all services that need fluid, such as steam, petrochemical, hydrocarbon, and HVAC processes. Certain gate valves are also recommended in powder and slurry products.
Types of Gate Valves
1. Solid Wedge Gate Valves
Solid wedge gate valves have a robust and simple design, which makes them one of the most popular types of gate valves. Solid wedge gate valves are used for various kinds of fluids and can be placed in different kinds of positions. Their strength gives these gate valves a robust structure needed for turbulent flow.
Solid wedge gate valves, however, do not compensate for seat alignment changes brought about by thermal expansion or pipe loads. Solid wedge gate valves are prone to leakage, which are also subject to thermal locking if exposed to high-temperature processes. Thus, these valves are used in applications that only require moderate to low pressure temperature levels.
2. Flexible Wedge Gate Valve
Flexible wedge gate valves are solid disk valves that have cuts around the perimeter, which have different shapes, sizes, and depth. Because of their narrow and shallow cut, flexible wedge gate valves are strong but are less flexible. But a wider cut makes these gate valves more flexible.
Flexible wedge gate valves, which are commonly used in steam systems, have been designed to reduce leakage and better seat alignment. The performance of these gate valves is enhanced, especially in thermal binding situations.
Since steam distorts valve bodies during thermal expansion, flexible wedge gate valves give the gate flexibility when the valve seat compresses.
3. Split Wedge or Parallel Disk Gate Valve
Split wedge disk valves are made of two solid pieces that are joined together by a special mechanism. When half of the disk is not aligned, the split disk, which can either be wedge-shaped or parallel, adjusts to the seating surface by itself.
Parallel disk gate valves provide bidirectional sealing as they are always in contact with the seats since they are spring-loaded. Split wedge gate valves are suitable in non-condensing gases and liquids that are in high and normal temperatures.
Thermal binding is prevented even if the valve has been closed due to the freedom of the disk movement.
4. OS & Y Gate Valve or Rising Stem
The stem of rising stem valves goes up as the valve opens and moves down when the valve closes. Gate valves having an inside screw design has a threaded portion of a stem, which is linked to the flow medium. So, when the valve opens, the stem rises together with the handwheel.
In outside screw design, however, the stem’s smooth portion is the only one exposed to the flow medium. So, the handwheel rises lower than the stem. OS & Y means Outside Steam and York Valve.
5. Non-rising Stem Gate Valve or Insider Screw Valve
When it comes to non-rising stem gate valves, the stem has no upward movements involved. The disk of the valve is internally threaded as it travels through the stem when it is rotated.
In non-rising stem gate valves, the stem threads are exposed to the flow medium. Since there is limited space for linear stem movement, this type of design is used. The good thing about non-rising stem gate valves is that their flow medium prevents corrosion, wear and tear, erosion to stem material.
Conclusion
Gate valves are known for their durability and flexibility. They are also remarkable with their strength, especially in various industries. By knowing what gate valves are, you would have a better idea of how to choose the right gate valves.
