Are Trunnion Ball Valves Bidirectional?
16 Mar,2022

A trunnion ball valve is a bidirectional, rotary device with a ball mounted in a trunnion. The trunnion is the mainframe for the valve, and the body houses all the other components. 

The body protects the other parts of the valve and helps them work together. A trunnion ball valve is a revolving-ball design with a single stem and body. It is shaped with the spherical surface of the ball aligned with the diameter of the stem. 

This type of valve has a fixed centerline that allows for a tight seal while preserving the isolation of equipment. Another benefit of a trunnion ball valve is that it is able to withstand both high pressure and temperatures.

In a trunnion ball valve, the spherical surface of the ball and the body are held in alignment. This means that the ball does not move upstream or downstream. The flow of a fluid through a trunnion is controlled by the spherical surface of the body. Because of this unique design, the trunnion is a true bidirectional sealing valve.

If you want to know more about bidirectional valves, follow this guide. 

What Is A Bidirectional Valve?

If you’re unfamiliar with bidirectional valves, it’s important to understand how they operate. Typically, a valve has two ports, an inlet, and an outlet. Normally, the valve remains closed. When it is at rest, however, it is considered “normally open.” This is the case when the valve is connected to flow lines. 

This type of valve has two ports – an inlet and an outlet. The inlet is blocked, so there is no fluid flow. Because of this, the bidirectional valve is often called “normally closed.” The at-rest box is connected to the flow lines. Similarly, the bidirectional valve can open in either direction. It is a common type of control valve.

The bidirectional valve is typically used in systems that move either air or hydraulic fluid, which requires it to be able to control the direction of flow. A bidirectional valve can be used in either direction, and it is often necessary for some systems. 

A bidirectional valve has two different sides. The upstream side is the pressure source, and the downstream side in the flow. This makes the valve versatile and convenient for different applications. In this type of valve, the fluid flows in both directions.

A trunnion ball valve, for instance, is made with the body and stem being aligned with each other. The ball is supported within the body, with the centerline of its spherical surface being equal to the diameter of the stem. This means that the ball does not move upstream or downstream, and the surface inside the body carries pressure end loads. A trunnion ball valve is a true bidirectional sealing valve.

A trunnion ball valve has a stem that holds the ball in place. The centerline of the ball’s spherical surface is the same as the diameter of the stem. Because of this, the ball doesn’t move upstream or downstream. Instead, it moves upstream so that the pressure applied to it doesn’t back feed into the supply. This makes a trunnion-ball bidirectional sealing valve.

Difference between Bidirectional and Unidirectional Valve

There are several differences between a bidirectional and a unidirectional valve, but both are important in the same application. While in bidirectional valves, fluids medium can flow in both directions, in the unidirectional valve, the medium flows in only one direction. 

Bidirectional and unidirectional valves function differently. The bidirectional valve is designed to block fluid flow in either direction. A bidirectional valve will have an arrow on the outside and a seat that will prevent the fluid from flowing in the opposite direction. The unidirectional valve is designed to only allow one direction of flow. A unidirectional valve will have a single seat. It will have an arrow on the outside and only one seat inside.

A bidirectional valve is designed to block fluid flow in both upstream and downstream directions. A unidirectional valve has a seat that seals the pressure source in one direction. Therefore, it is ideal for applications that require one direction of flow only. For instance, a swing check valve is not directional. 

What Is A Trunnion Ball Valve?

A trunnion ball valve is a quarter-turn valve. It features a hollow sphere-shaped ball in the center. When the actuator is turned on, the ball rotates to start or stop the flow. This is what makes this type of valve so versatile and useful. It can be used in both industrial and residential settings. 

A trunnion ball valve is a type of ball valve that uses a ball and stem to open or close. This type of valve contains seals on the seats and stem to prevent fluid leakage. Additionally, it has an adjustable gland packing box to help the valve withstand varying pressures. Typical trunnion-ball valves are equipped with two bleeders for depressurization.

Trunnion-mounted ball valves have three sections or pieces. Each section of the trunnion has a shaft and is made of metal. This material helps the ball absorb added pressure from the flow and reduces the stress on the ball. A trunnion-mounted ball valve is most common in large-scale and low-torque applications. In the electrical industry, it is often used in turbines and generators.

Are Trunnion Ball Valves Bidirectional?

Yes, trunnion ball valves are truly bidirectional. In this type of valve, the medium flows in both directions. The trunnion ball valve stem is rigidly fixed in place, holding the ball securely in place. In addition, it has spring-loaded seats that prevent the ball from floating downstream. The spring-loaded seat mechanism makes the valve leak-proof as the ball wears out. It’s a good choice for high-volume petrochemical pipelines or gas lines. The trunnion stem and trunnion-mount ball valves are also a good choice for corrosive environments, including nuclear power plants.

Trunnion ball valves have a spherical stem and body. The ball’s spherical surface is identical to the diameter of the stem. Because of this, the ball won’t move upstream or downstream. This means that the seals are bidirectional, and the valve can handle high pressure and temperatures. And because of the trunnion’s unique design, it can be used in multiple applications.

Bidirectional Sealing in Trunnion Valve

Trunnion ball valves provide true bi-directional sealing. The spherical surface of the ball, held within the body, is parallel to the stem’s diameter. This means that the ball never moves upstream or downstream. The sealing surface within the body carries pressure end loads, making this a true bi-directional valve. A trunnion ball valve is a highly efficient option for applications involving high-pressure fluid flow.

In trunnion-mounted ball valves, the ball is attached only to the stem. The seat rings are pressed against the ball. In a bi-directional valve, the elastomeric seat ring presses the ball against the downstream seat, providing a tight seal in both directions. Floating ball valves also provide bi-directional shut-off.

Bi-directional sealing in trunnion-mounted ball valves prevents the passage of line fluid into the valve body. They also preserve equipment isolation in power applications. Unlike their single-directional counterparts, trunnion-mounted ball valves are better suited for high-pressure, large-scale applications. They also allow for a more controlled and reliable flow, which leads to a longer valve life.

A trunnion mounted ball valve has a spring-loaded seat and is used in many different industrial applications. A spring-loaded seat allows the ball closure to move into a cavity while maintaining a tight seal. This type of valve is commonly used in shut-off and control applications, as it provides tight sealing with low torque.