Ball valves and gate valves are valves commonly used to control the circulation of liquids and gases along a pipeline. They come in various sizes each suited for different functions. Although they serve the same function they are designed and function differently.
What is a Ball Valve?
A ball valve is used to regulate the flow of water using a pivoting ball. The ball is perforated as well as hollow. With a ball valve, you can provide passage and block the flow of substances. It also allows you to modulate the amount of flow.
What is a Gate valve?
A gate valve is a flap typically a solid that is rectangular. The flap acts as a barrier preventing liquids or gasses from passing through and when lifted it allows for the passage of these substances. Because of this linear motion, the gate valve can only function as open or shut.
How Ball Valve vs. Gate valve Compare
Valve Symbol
The gate valve symbol is comprised of two lines crossing each other to form an ‘X’ with three other lines two at the end and one running down the middle. The symbol has a similar likeness to a bowtie.
The middle line may sometimes be excluded.
On the other hand, ball valve just like a gate valve is an inverted ‘X’ with a circle in the middle.
Advantages
Ball Valve Advantages
- They can resist high-pressure making them the perfect flow control method for substances that are transported under high pressure.
- Ball valves do not require a lot of maintenance. The rotating ball is designed to withstand wear. The parts can also be easily taken apart to be cleaned and reassembled again.
- The ball valve allows for partial opening, it allows one to regulate the flow of fluids.
- Ball valves are durable making them last for longer.
- It has a tight seal which remains so even after being used for a long time. The tight seal ensures that there are no leakages.
- Featuring a tight sealing valve, gate valves have very little erosion happening on the sealing surface.
Gate Valve Advantages
- Gate valves are very cost-friendly. They are relatively cheaper to purchase as well as maintain.
- A gate valve has a relatively straight media channel with no obstruction and this leads to a greatly reduced fluid resistance.
- Gate valves function using a linear motion that is perpendicular to the direction of flow. It therefore requires very little energy to operate a gate valve.
- The gate valve has a simple design that is easy to use.
- With a raising and lowering flap, the gate valve can be used in any direction. It therefore allows for dual-direction flow.
- Gate valves experience minimum pressure loss due to the laminar flow of the substances.
Limitations
It is important to note that not all types of these valves experience the same limitation. Different designs of the flow valves have different features which may address these limitations.
Ball Valve Limitations
- Although the ball valves allow for partial opening this should only be done when needed. When left at the partial opening for long periods the valve may lead to the formation of soft seats which will cause it to get stuck
- The ball valve often gets blockages especially when used to control thick liquids such as slurries.
- They require a wider space to install. The opening valve is bigger and therefore requires more space
- Ball valves tend to cost more when compared to gate valves of similar types
Gate Valve Limitations
- The gate valve is more prone to leakages compared to ball valves. These leakages also increase the rate of erosion on the sealing surface.
- Gate valves experience a functional delay when it comes to stopping water flow as it takes a bit of time to open and close the valve
- It is difficult to visually ascertain whether or not a gate valve is open
Design and Structure (Compare Various Parts)
Ball Valves Structure
Ball valves comprise of;
- Body: This is the main part that encases all the valve components
- Rotary Ball: This is the pivoting ball that is performed to allow for media to go through.
- Stem: The stem is responsible for moving and rotating the ball valve from the inside of the valve. This stem is then connected to an actuator which allows one to control it from outside.
- Seats: It functions as a barrier sealing the body from the ball. It also provides support for the ball.
- Packing: This is a seal surrounding the stem. It stops media from escaping
- Bonnet: It carries the stem and packing.
A gate valve comprises of;
- Body: Outer layer of the gate valve
- Gate; Gate is responsible for sealing the substances to prevent them from flowing or releasing them. There are two main categories of gates used in the gate valves which are Parallel and wedge-shaped gates.
- Seat: The seat executes and secures the seal with the gate. A gate valve is normally fitted with two seats. Gates in these valves are either fused into the body of the valve or as a ring.
- Stem: Stem is responsible for opening and closing the gate by spinning it. It can be spun manually or using an actuator. There are different types of stems, rising stems and non-rising stems.
- Bonnet: It is a protective layer for the inner parts of the gate valve. It is installed either by bolting or screwing it into place.
- Actuator: The part used to open and shut the valve
Working Principle of these Types of Valves
Ball Valve Working Principle
Ball valves have multiple ports, the number of ports depends on the type of ball valve in question. Using an actuator manual methods are used to open or close the port of a ball. The ball valve pushes the valve handle to rotate.
This in turn causes the ball to rotate twisting its ports perpendicularly to the flow. When the open ports are aligned in the same direction as the flow, then the valve is open. This is achieved by turning the handle at a 90-degree angle.
Gate Valve Working Principle
The gate valve functions simply. Regular gate valves are operated using a threaded stem. Its threaded stem is connected to an actuator. An actuator could be a rotating hand wheel or a motor and it is connected to the gate.
You turn the actuator which in turn rotates the stem. Spinning the stem causes the threads to also move resulting in the gate being lifted or lowered. You need to apply a 360-degree movement multiple times for the gate to completely open or close.
Substance flows when the flap is lifted out of the way and stops when it is lowered back to its place.
Flow Control and Head Loss
Ball valves offer more flow control as they allow for partial opening to regulate flow. It also has a quick opening and closing mechanism. It only requires a 90-degree turn compared to gate valves which require several 360-degree turns to either close or open it.
Gate valves have minimum head loss as it structurally straighter than a ball valve and therefore have minimal water resistance due to decreased friction. Ball valves have a smaller head loss only when fully open.
Application of Ball Valve and Gate Valve
Gate valves and ball valves serve a similar purpose. It is best to choose one that better suits your needs. These valves are used in:
- Vehicle Wash Systems
- Oil and Gas systems
- Food and Beverage systems
- Automotive industry
- Chemical and Treatment mixtures
- Irrigation systems
- Home applications for example washing machines and dishwashers.
- Water Treatment Equipment
- Manufacturing plants
- Power Processing plants
- Pharmaceutical
Conclusion
It is important to take into account each of the advantages and limitations of both devices. This will allow you to select the one that is best suited for your needs. Gate valves are cheaper and require a smaller space for installation. Ball valves are more durable and are perfect for flow control. The application of the valve will help you decide the best valve for you.
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