how does a floating ball valve work? - SIO

How Does a Floating Ball Valve Work?

Home How Does a Floating Ball Valve Work?
13/09/2019
Share:

Table of Contents

Floating ball valves are the most common type of ball valve used in the piping industry. They are quarter-turn valves that feature a disk in the shape of a ball. The ball is perforated and hollow allowing the medium to pass through it when the valve is open. Floating ball valves are used in many different kinds of applications.

floating ball vlave
Floating ball vlave

Floating ball valves are capable of providing bi-directional sealing which is why they are used widely in oil and gas, water, and other industries. They are available in a number of different sizes and configurations, like air operated ball valve. You can also customize these valves to make them suitable for high-pressure operations. Floating ball valves are popular in industrial use because of the air-tight seal they provide when fully closed. In this blog we will discuss how floating ball valves are constructed and how they work. Read on to find out more. 

How are Floating Ball Valves Constructed?

Floating ball valves feature all the basic components of a ball valve. In addition to these components, other add-ons like O-rings and extra packing can also be added to customize the valve. Here is a look at some of the main parts of a floating ball valve. 

Diagram of part of a floating ball valve

Body

The body of the floating ball valve houses all the moving parts. It may be a single unit or divided into different pieces. The body is designed to protect the working parts of the valve and make it easier to connect the valve to the pipeline. It is also the first pressure boundary of the valve. Floating ball valve body is usually made of carbon steel, stainless steel, low-temperature carbon steel, duplex, super duplex, inconel, and more.

Trim

The trim houses all the moving parts of a floating ball valve. These parts include the stem, ball, seats, and sleeves of the valve. The stem connects the actuator to the disk or ball. It is connected to a slot at the top of the ball and can move the ball to a quarter turn. Floating ball valves feature anti-blowout stems that can handle both medium and low temperatures. The disk in a floating ball valve is in the shape of a hollow ball. The hollow center of the ball is known as the bore. The ball is made of steel and has perforations on it for better sealing. It is connected to the stem on one end and has the ability to freely float in the valve. Floating ball valves feature two elastomeric seats. The seats have seal rings that provide tight shut-off when the valve is turned off and protect the seats against high-pressure when the valve is turned on.

Actuator

The actuator is what you use to open and close the valve. It is connected to the stem on one end so that when you move the actuator, the stem moves as well. Many kinds of actuators can be used with floating ball valves depending on the application and the medium. Some common types include bare stem, gear, hand lever, pneumatic actuator, hydraulic actuator, gas actuator, gas-over-oil actuator, motor-operated actuator, hydraulic/ electro actuator, hydraulic-operated actuator, and more.  

How Do Floating Ball Valves Work?

Floating ball valves are shut-off valves that provide a tight seal in critical operations. They are suitable for low-pressure and certain high-pressure applications and can control the flow of liquids and gasses. Just like all other ball valves, they cannot regulate the flow of medium and should not be used for throttling purposes. Floating ball valves can either be fully open or fully closed.

Diagram of part of a floating ball valve

For example, if you wanted to control the flow of water in a hydro-electric plant, you will install a floating ball valve like SIO API6D API 607 Floating Ball valve to the pipeline. The valve can be welded in or connected to the pipeline through bolts. To open the floating ball valve, you have to turn the actuator to a 90-degree angle. As the actuator moves, it turns the stem of the valve. The stem is connected to the ball and rotates it so that the hollow side is parallel to the pipeline. The water can now freely flow through the valve to the other end of the pipeline. The onstream pressure moves the ball slightly so it is in contact with the downstream seat, making a seal. This prevents water from getting into the valve body. 

Diagram of how the pressure moves.

To close the valve, move the actuator a quarter turn again so that the ball rotates and the hollow side becomes perpendicular to the pipeline. The onstream pressure on the valve pushes the upstream seat and the ball to the downstream seat so that a tight seal is formed and the flow of water is effectively stopped. Floating ball valves provide bi-directional shut-off. This means the medium can flow from either direction without affecting the function of the valve. 

Types of Floating Ball Valves

Floating ball valves have many different sizes, types, and configurations. They are very versatile and can be customized to suit any kind of application or pipeline such as carbon steel ball valve. Here are some common types of floating ball valves.

Based on Bore Size

The hollow center of the ball is called the bore. There are two types of floating ball valves based on bore size.

Full Bore Floating Ball Valves

Full bore floating ball valves feature a bore size that matches the diameter of the pipeline the valve is connected to. These valves allow the flow of medium without any restrictions and are suitable for liquid and gaseous mediums. In full bore floating valves, the onstream pressure from the pipeline affects the entire surface area of the ball, pushing it against the downstream seat more effectively. Full bore floating ball valves provide tighter seals than any other kind of ball valve.

Reduced Bore Floating Ball Valves

In reduced bore floating ball valves, the size of the bore is a few nominal sizes less than the diameter of the pipeline. These valves are suited for applications where the flow of medium needs to be restricted. They are mostly used in the oil and gas industry. In reduced bore floating valves, the onstream pressure from the pipeline affects a dedicated portion of the ball. This means a certain level of pressure is required to push the ball against the downstream seat. Reduced bore floating ball valves can only be used in applications where the pressure is high enough to achieve tight shut-off of the valve. 

Based on Assembly

Floating ball valves can have one, two, or three pieces joined together through welded or forged connections. There are three types of floating ball valves based on assembly.

One-Piece Floating Ball Valve

This type of floating ball valve features a single cast or forged steel body that houses all the moving parts of the valve. Single-piece floating ball valves are available in different sizes and are the most compact type of ball valve. They are the cheapest floating ball valves available in the market and are widely used in smaller applications. Single-piece floating ball valves cannot be opened for cleaning, repair, or maintenance so they are mostly used with mediums like gasses where little maintenance is required.

One-piece floating ball valve
One-piece floating ball valve

Two-Piece Floating Ball Valve

Two-piece floating ball valves feature two pieces of housing that are either forged or cast together. One piece of the valve is always larger than the other and it houses all the moving parts of the valve. Two-piece floating ball valves can be opened for maintenance, repair, and cleaning. However, the valve needs to be disconnected from the pipeline to do so. 

Two-piece cast floating ball valve
Two-piece cast floating ball valve

Three-Piece Floating Ball Valve

This type of floating ball valve features three pieces of housing or body. These valves are larger in size and more expensive. You can also find small-sized three-piece floating ball valves for compact applications. The three pieces of the body are forged to each other. One half of the body is bigger and houses all the moving parts of the valve. This type of valve can be easily maintained, repaired, or cleaned without having to remove the valve from the pipeline. 

High pressure ball valve in forged steel
High-pressure ball valve

5 Differences Between Floating Ball Valve and Trunnion Mounted Ball Valve

The floating ball valve and trunnion mounted ball valve are the two most popular kinds of ball valves. They are frequently used in similar industries for both high and low-pressure operations However, there is always debate on which of the two valves is better. Here is a look at the top 5 differences between floating and trunnion mounted ball valve.

Diagram of floating ball valve and trunnion mounted ball valve

Source: https://taurusdbbvalves.com

Construction

The first difference between floating and trunnion mounted ball valves is in the way the valve is constructed. In floating ball valves the ball is only connected to the stem from one end whereas the other end is free. The ball is free to float inside the valve. In trunnion mounted ball valve, the ball is connected to the stem on one end and to another shaft called the trunnion on the other end. The ball is held firmly in place and can only rotate as the stem moves. You can easily distinguish between the two valves when you look at them as the trunnion mounted ball will have an added shaft at the bottom.

Type of Seats

In floating ball valves, the seats are usually made of elastomeric material. An elastomer is a polymer with viscoelasticity (both viscosity and elasticity). This soft material helps cushion the pressure from the onstream that pushes the ball to the seats. The seats in the valve directly manage all the pressure from the onstream. The seats in a floating ball valve have additional seal rings as well since they have to manage all the pressure. In trunnion mounted ball valve the seats are spring-loaded. Any additional pressure is managed by the stem and the trunnion. 

Sealing Function

Floating and trunnion mounted ball valves both provide shut-off but have different sealing functions. 

When floating ball valves are closed, the onstream pressure forces the upstream seat and the ball to the downstream seat forming a seal. 

In trunnion mounted ball valves, the onstream pressure activates the spring-loaded seats and they move towards the ball sealing the valve. 

So the main difference in their sealing function is that, in trunnion mounted ball valves the ball does not have free movement and it can only rotate as the stem moves while In floating ball valves, the ball is free to rotate as well as move sideways. 

Application

Floating ball valves are more suited for medium and low-pressure applications. They usually have smaller diameters and only provide seal only from the downstream side. Floating ball valves are suitable for mediums like liquids and gasses. Trunnion mounted ball valves are suited for larger, high-pressure applications. Since the seats move towards the ball, the valve seals from both the upstream and downstream end. Trunnion mounted ball valves can be used with liquids, gasses, as well as slurry mediums. 

Added Features

In floating ball valves the seats need a separate mechanism for releasing additional pressure. This is the reason why they are not suited for high-pressure situations. However, the seats in trunnion mounted ball valve are self-relieving so any additional pressure is handled without the need for a separate mechanism. Trunnion mounted ball valves can also have double block and bleed abilities. This enables these valves to be used in critical high-pressure, high-temperature operations. 

Conclusion

Floating ball valves have many advantages like small flow resistance, simple structure, good sealing performance, and being cost-effective for certain size and pressure. They are used widely in the oil and gas and water industry. As one of the best high pressure ball valves manufacturers, they are available in a number of sizes and can be customized to suit your needs in SIO, whether it’s a metal seat ball valve, three-piece ball valve or ball valve flange type. At SIO we can add value-added features like oval safety handle, locking device, easy automation – pneumatic actuator, T-handle, extended bonnet for insulation, and more. Get in touch with us to discuss your valve needs. 

Copyright© 2019 Ninbo SIO Fluid Equipment Co., Ltd. All Rights Reserved.

Request A Quote

    Please upload only jpg, png, pdf, dwg fliles. (Optional)
    Choose your industry