What is a ball valve and how does it work?

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A ball valve is a shut-off valve that allows, traps, and controls the flow of fluids, gases, and vapours into the piping system by rotating the ball with a ball inside the valve. The ball is seated opposite two seats and has a shaft connected to the operating and rotating machine around the ball. When the cross-section of the bore is perpendicular to the flow zone, the liquid is not allowed to pass through the valve. The fluid flows through the valve and the flow of the liquid depends on the location of the bore exposed on the ground.

Ball valves are a type of quarter-turn valve-like valves and butterfly valves. They can be controlled manually or by using an actuator. The simple operation of a ball valve is the use of a wrench or lever hand operated by the operator. Torque is used to rotate the lever arm 90 ° clockwise or clockwise to open or close the valve. If the lever arm is in line with the pipe, it indicates that the valve is open. If the lever arm is perpendicular to the pipe, it indicates that the valve is closed.

Components of a ball valve

Valve housing

This is the main part of the ball valve which contains all internal components for on/off control. It is made of strong and durable metal, thermoplastic, or thermoplastic-lined metal that protects parts of the ball valve. It also allows access to an external control device that rotates the ball.

Rotary Ball

The ball is designed with a centre bore that the media flows through. The direction of the ball is controlled by turning the stem. The ball valve can have a solid ball or hollow ball. The solid ball has a constant opening diameter throughout its structure, which helps the liquid to flow smoothly at a constant rate. An empty ball, on the other hand, has an empty inner structure, and the space inside allows more liquid to pass through the valve. However, a large area creates chaos and great speed. A hollow ball is lighter and cheaper compared to a solid ball.

Stem

This connects the ball to the external control mechanism. For example, in a manual ball valve the stem is connected to a handle or lever. The stem has markings such as O-rings and packing rings to close the stem and bonnet to avoid liquid leaks. The stem can be manually operated by a lever or hand wheel or by electric, pneumatic, or hydraulic actuation.

Seat

These are the discs lying between the body and the ball. It provides a seal between the ball and its body and supports the ball. The downstream seat is found on the opposite side of the upstream seat which is adjacent to the discharge side of the valve.

Power source

The stem of the ball valve is rotated using manually or activated power sources. Personal activation includes operator-controlled levers and handles. Automatic power sources such as electric, pneumatic and hydraulic actuation are available.

Bonnet

The bonnet is the part of the valve housing that contains and protects the stem and packing. It would be welded or bolted to the body.

Types of ball valves

Ball valves are classified according to their housing assembly, ball design, and bore profile.

Housing assembly

The valve housing assembly can be divided into three commonly used designs: one-piece, two-piece and three-housing. The difference is how the valve is connected and this affects the chances of maintenance or repair. The operation of the valves is the same for each individual.

One-piece ball valve:

This is the cheapest type. The two parts that insert the ball are pressed or welded. The valves cannot be opened for cleaning or repair. This type is usually used for less demanding applications.

Two pieces ball valve:

Two-piece valves can be disassembled to clean, supply and inspect. Usually, the components are connected by a threaded connection. The valve must be completely removed from the pipe to separate the two parts.

Three pieces ball valve:

The most expensive valves usually have three pieces. The parts are usually fastened together by means of a bolt. The advantage of this simulation is that the valve can be serviced without removing the entire valve from the pipe.

Ball design

There are two main types of ball designs - floating and trunnion. Floating is the most common design, while trunnion balls are often the most expensive.

Floating

Floating balls are supported by a cup-shaped seat to form a solid mark between the body and the ball.

Trunnion

Trunnion balls work in much the same way as floating balls, only seats loaded with spring and the ball rotates only on its axis. Operating torque is usually low on trunnion valves.

Ball valve hole design

Full bore

A full-bore design is also called a full port design. The bore diameter is equal to the pipe, which reduces friction loss and makes the valve easier to clean.

Reduced bore

The reduced bore design is the one you will find on most ball valves. This design has a smaller diameter than the full bore and may present a slight friction loss.

V-shaped

A hole in a ball or in a valve seat can have a V-shaped design. V-shaped holes can more accurately control the flow rate when rotating the ball.

Vented

The vented valve has a small hole drilled in the upper side. This hole eliminates unwanted pressure inside the valve.