A Comprehensive Guide to Trunnion Ball Valves

In this blog post, you’ll read:Trunnion ball valves are highly efficient, cost-effective quarter-turn valves ideal for high-pressure applications. Their unique design, with a fixed ball supported by trunnions, ensures stability and superior sealing, reducing operational torque and maintenance costs. Widely used in industries like oil, gas, and power generation, these valves offer reliable performance in various environments. Choosing a quality trunnion ball valve ensures long-term efficiency and investment value.
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Trunnion ball valves are quarter-turn valves used to turn on or off the flow of a substance in a pipe. Since “free-floating” is the most common type of ball valve design, the trunnion type is a change. The stem and the trunnion are on opposite ends of a trunnion ball valve. The ball links to the stem on one end and the trunk on the other. With this change in shape, the ball remains in place very well. The ball in a floating ball valve is only attached to the stem, which is why it is called “floating.”

Trunnion ball valves are not only superior in performance but also cost-effective. They can be used in low—and high-pressure situations and cost less to run. This cost-effectiveness reassures the users about the value and return on investment of trunnion ball valves. In this post, we will discuss trunnion ball valves in detail. Let’s dive in.

What Are Trunnion Ball Valves?

A trunnion ball valve, a unique configuration, is designed to maintain a ball in position using two trunnions. This distinctive design allows the valve to open or close by enabling the ball to rotate while in position. Many industries rely on this specialized form of valve for its exceptional performance. Trunnion ball valves are available in various sizes and pressure ratings. It is designed to accommodate the diverse requirements of different industries.

The gas, oil, chemical processing, and power generation sectors employ trunnion ball valves. These valves are useful in applications that require a high-quality valve capable of withstanding high temperatures and pressures.

How is a Trunnion Ball Valve Constructed?

trunnion ball valve constructed
Trunnion ball valve constructed

There are different kinds of trunnion ball valves, and you can buy them from a reliable valve manufacturer in China. The seat rings at the two ends of the trunnion shape are compressed together to keep the ball in place. These are the various components of a Trunnion ball valve.


The body of a ball valve is the part that holds the inside of the valve in place and supports it. Depending on its use, the material for this design could be made of various materials. Stainless steel, duplex, low-temperature carbon steel, Inconel, and super duplex are often used materials.


The trunnion ball valve has a design feature called a seat that goes around the ball. The seats keep the ball in place when the actuator is turned on, so it can’t be accessed. There are two kinds: soft and metal. The metal one moves in the same way as the ball.


The trunnion ball valve has an extra tube called a trunnion that holds the ball in place from below. Its job is to keep the ball’s connection tight. Some trunnion-mounted ball valves have the trunnion attached to the spherical ball. However, in others, it is bonded to the spherical ball disc.


It moves slowly around a plate resembling a sphere to stop or start the flow. It’s connected to the trunnion on one end and the stem on the other. The ball is held in place while it is being passed around. Often, the seats of the Trunnion ball valve touch this ball, reducing the force.


The trunnion ball valve’s stem connects the ball to the actuator. It has an extra shaft that connects to the ball and helps hold the ball in place. The stem also lets you control how the ball moves. The stems on trunnion-mounted ball valves are stronger, which means they can handle high temperatures and pressures without damage.


Injection fits are made in the seat and stem area. When the seal is broken, and leaks begin, a sealer injection fitting can add grease. When the sealer is applied, it makes a partial seal that stops more leaks. You should only use the sealant if an injection fits in an emergency.


With a trunnion ball valve’s motor, the valve can be opened or closed. For example, air-operated ball valves use different motors depending on the purpose and medium. Standard actuators on valves are bare stems, hand handles, air actuators, gears, and hydraulic actuators. On top of that, you can use an electric actuator, a gas actuator, a gas-over-oil actuator, and a motor-operated actuator.


The disc in a Trunnion ball valve is shaped like a solid ball with a ball in it. You can connect the ball to the stem on one side and the trunnion on the other. In a trunnion ball valve, the ball or disc is held in place while it turns. Torque is lessened because the seats always contact the ball.

How to Do Trunnion Ball Valves Work?

trunnion ball valves structure
Trunnion ball valve structure

According to the ball valve manufacturer, a trunnion ball valve functions similarly to a floating ball valve. Its operation involves rotating the ball to regulate the passage of gas or liquid.

The valve is opened or closed when the stem receives a signal from the actuator, which causes the ball to rotate by 90 degrees. Throughout rotation, the seat assures that the object remains in position. If leakage does occur, the injection system functions as a partial seal.

The trunnion ball valve’s actuator is rotated 90 degrees clockwise to initiate oil passage through the valve. The ball is linked to the valve stem, in which the actuator is coupled.

The actuator’s rotation moves the stem and the ball connected to it. This results in unimpeded substance movement and decreased pipeline pressure, which hinders the substances’ ability to flow through the conduit.

Advantages of Trunnion Ball Valve

High-pressure applications

The trunnion ball valve is the optimal design type for ball valves in high-pressure applications. These movable ball valves provide a certain degree of mobility for the ball. A sealing is produced on only one side of the valve as the ball floats marginally downstream against the seat ring during operation. Additionally, an increase in torque is applied to the stem. This superior performance in high-pressure situations instills confidence in the reliability and effectiveness of trunnion ball valves.

At this juncture, the trunnion design presents a viable resolution. As it is connected to the trunnion in the trunnion valve configuration, the ball does not levitate. This is helpful because the stem is not subjected to additional torque, and a correct closure is maintained on both sides. Therefore, a trunnion ball valve will provide superior sealing at higher pressures while requiring less torque to rotate.

Spring-loaded seats

The seats for trunnion ball valves are equipped with springs. The pressure in a floating ball valve presses the ball against the seats, establishing a seal. Regrettably, the ball valve is ineffective in low-pressure systems because it requires high pressure to form a proper closure.

Trunnion-mounted ball valves are effective in both low—and high-pressure environments. While functioning properly for high-pressure applications, spring-loaded seats will also form a seal in low-pressure or no-pressure environments.

Reduced operational costs

Additional pressure applied to the valve is absorbed by the trunnion and the stem, reducing operational expenses for a trunnion-mounted ball valve. Consequently, the operational torque is reduced, thereby obviating the necessity for a sizable actuator.

Weight of A Trunnion-Mounted Ball Valve

reduced operational costs
reduced operational costs

The design of a trunnion ball valve adheres to API608 or API 6D, in addition to several other industry standards. API 6D specifies the trunnion valve’s fundamental design, dimensions, and testing criteria. By various bore sizes and body dimensions, the API 6D standard also stipulates the weights of trunnion ball valves that meet the requirements.

Maintenance of Trunnion Ball Valve

Routine maintenance is necessary on trunnion ball valves to ensure optimal performance and lifetime. Routine inspections are essential to guarantee that the valve body, ball, or seats are not damaged. In addition, the stem and the actuator must be inspected to ensure they operate appropriately.

Lubricating the valve ensures that the stem and ball will function smoothly. If the valve is used in a difficult environment, such as one with high temperatures or corrosive fluids, it must be examined more regularly.


Trunnion-mounted ball valves offer several advantages over alternative valve designs, particularly for applications requiring high flow rates and pressure. Their unique design guarantees proper encapsulation, effectively preventing leakage even under high pressure.

Additionally, the trunnion-mounted configuration decreases the necessary torque and prolongs the operational lifespan of the valve. An advance in the correct direction is to acquire a trunnion ball valve from a reputable valve manufacturer in China. Contact us immediately for a quotation!

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