1- Ball Valve:
A one-way valve that is opened and closed by pressure on a ball which fits into a cup-shaped
opening.
Advantages of ball valves:
Efficiency: Ball valves don’t need any lubrication, and offer a bubble-tight seal with
low torque.
Affordability: They can often be purchased at a considerably lower cost than
comparable products for the same job.
Durability: They offer a long service life and, when used under the right conditions,
will provide many years of reliable use. Ball valves are less prone to damage than
other kinds of valves, and the plastic variety aren’t susceptible to corrosion.
Easy to use: Ball valves are relatively quick and easy to install, and plastic ball valves
are light and easy to handle.
Versatile: They’re appropriate for a wide range of industrial applications where it’s
necessary to regulate the flow of liquids or gases.
Strong: Ball valves can maintain and regulate high pressure, high volume and a high
flow of temperature.
Simple to repair: Easily access the seats when a valve requires fixing.
Disadvantages of ball valves:
Wear and tear: When used to regulate the wrong types of fluids, such as slurries,
ball valves can stick in position and become jammed due to suspended particles being
trapped. This can cause the valve to wear, or to become damaged or stuck.
2-Gate Valve : also known as a sluice valve, is a valve which opens by lifting a round or
rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the
sealing surfaces between the gate and seats are planar, so gate valves are often used when a
straight-line flow of fluid and minimum restriction is desired
There are a few advantages of gate valve that globe valve doesn’t have:
1. The fluid resistance is small, because the internal media channel of the valve body is
straight, the media flows through the valve does not change its flow direction.
2. It helps to save more energy when open and close gate valve, because the movement
direction of ram is perpendicular of media flow direction, comparing to the globe valve, gate
valve saves more energy when opening and closing.
3. The direction of media flow is unrestricted, non-spoiler, do not reduce the pressure, the
medium can flow from any direction of the gate valve on both sides, which both can reach the
purpose of use. It’s more suitable for the pipeline that medium flow direction may change.
4. The sealing performance is very good, so that the sealing surface is less eroded when it’s
full open.
5. The erosion of sealing surface by working medium is lighter than globe valve when it’s
fully open.
In the meantime, comparing to globe valve, gate valve also has some
disadvantages as below:
1. The sealing surface is easy to damage. When opening and closing, the gate contact with the
valve seat, which cause the friction, then short the seal using life, and the maintenance is
more difficult.
2. The opening and closing time is long, since it needs to be fully open or fully closed, it
takes some certain space to open the gate valve, and due to high dimensions, it requires the
larger space for installation.
3. The structure is complicated. Gate valve usually has two sealing surfaces, which adds
some extra difficulty to the process, polish and maintain. Since there too many parts, the
manufacturing and maintenance is more difficult, the cost is higher than the globe valve.
3- Globe valves: different from ball valve, is a type of valve used for regulating flow in a
pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally
spherical body.
Advantages of Gate Valves
1. Closing feature is very good.
2. These valves can be used both ways in the circuit
3. They provide laminar flow, pressure loss is minimum.
Disadvantages of Gate Valves
1. They cannot be opened and closed quickly. To fully open or close 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
2. Assembly, start-up and maintenance require large space.
3. In systems where high temperature changes irregularly, due to the load in pipe at the valve
end, leakages in gate valves occur.
4. At the place of operation, repair and maintenance of seating surfaces are difficult.
4- Control Valve is a valve used to control fluid flow by varying the size of the flow
passage as directed by a signal from a controller. This enables the direct control of flow rate
and the consequential control of process quantities such as pressure, temperature,
and liquid level.
