Why trunnion ball valve

A trunnion ball valve and a floating ball valve are examples of valve designs made to fit the needs of specific fluid control systems. While they are both ball valves , they each have unique features that set them apart. As you weigh which of them is best for your project, here is an in-depth comparison of the two to guide you.

A trunnion ball valve consists of a ball mounted on a trunnion on the bottom and joined to a stem at the top. These parts are often welded together which is why this type of valve is sometimes referred to as a trunnion mounted ball valve or a fully welded trunnion ball valve. Given as the ball is mounted and experiences less friction and media pressure force, this valve requires less torque to operate.

A floating ball valve , on the other hand, comprises a ball linked to a stem at the top but floats freely at the bottom. It is held in place by fluid pressure and seat rings as opposed to being mounted on a trunnion. As such, it requires high torque to operate. It is, nevertheless, a reliable bi-directional shut-off valve. A trunnion ball valve consist of 4 main parts:.

The trunnion forms the base onto which the ball is mounted. At the top end, the ball is linked to the stem and the stem is connected to an exterior actuator lever. In a flanged trunnion ball valve , there are spring-loaded seats and a polymer ring insert between the trunnion and the ball. The springs put pressure on the ball to keep it in place.

Together with the polymer ring, they also reduce friction when the ball is rotating. To facilitate the flow of media, the ball is made hollow in the middle. It can either be a full bore or a partial bore. A full bore is a ball whose hollow part is the same size as the pipeline it is installed in.

When the actuator is turned, the stem connected to it also turns. These actions cause the ball to rotate on the trunnion to an open or closed position. During and after fluid flow, seals in the seats and stem prevent the fluid from leaking out of the pipeline. An adjustable gland packing box also helps the valve take on different capacities of pressure.

A typical trunnion ball valve would also have 2 bleeders for purposes of depressurization. The structure of a trunnion ball valve makes it ideal for application in high pressure and high-temperature fluid management applications. It requires less torque to operate. It can be applied in both large scale or small scale operations. Less friction during trunnion ball valve operation helps mitigate wear and tear.

Due to the fully-welded or bolted-together design of a trunnion ball valve, it is difficult to repair it in-line. Repairs would thus interrupt normal pipeline operations. If maintenance is not carried out as required, welded parts could begin to operate with higher friction which could lessen efficiency.

Source: fastcdn. Due to its resilience, a trunnion ball valve can be applied in a wide range of applications including:. Chemical manufacturing plants — the transmission of chemicals through pipelines during production requires stringent management.

More so where corrosive chemicals are involved because leakages and high reactive temperatures could harm staff or the surrounding environment. Trunnion mounted ball valves have a similar structure as traditional ball valves. The only difference is that trunnion ball valves have additional mechanical anchoring that supports the ball or disk.

In this design, the ball is supported from both ends on the x-axis, so that it stays in place and is easy to control. Here is a look at the different parts of a trunnion-mounted ball valve.

The body of the valve is the casing that holds and protects the internal parts of a trunnion mounted ball valve. It can be made of carbon steel, stainless steel, low-temperature carbon steel, duplex, super duplex, Inconel, and more depending on the application.

The stem of a trunnion mounted ball valve connects the ball to the actuator. It is connected to the ball through welded joints and it controls the movement of the ball. The seats of a trunnion-mounted ball valve surround the ball.

When the actuator is turned, the seats hold the ball snugly in place, sealing off any access. Trunnion ball valves have spring-loaded seats that move towards the ball as it is held firmly in place. In a trunnion mounted ball valve, there is an additional shaft that holds the ball in place from below.

This small shaft is known as a trunnion and it keeps the ball firmly in place. In some ball valves, the trunnion is an extension of the ball while in others it is connected to the ball through welded joints. The disk in a trunnion mounted ball valve is in the shape of a perforated, solid ball. The ball is connected to the stem on one end and the trunnion on the other. In a trunnion ball valve, the ball or disk is held in place while it rotates. The seats are always in contact with the ball, hence reducing torque.

The actuator in a trunnion ball valve is used to open or close the valve. There are different kinds of actuators used in ball valves depending upon the application and medium. Bare stem, gear, hand lever, pneumatic actuator , and hydraulic actuator are some common actuators found on the valve. Trunnion mounted ball valves are available in many different configurations. They are highly customizable so you can choose the size, type, and actuator that suits your needs. China also has the best trunnion mounted ball valve manufacturers for you to choose.

Here are some common types of trunnion ball valves. Body configuration determines how a valve can be accessed for maintenance or repair. There are two types of trunnion mounted ball valves based on body configuration.

This type of ball valve has a removable bonnet cover on the top of the valve. The internal parts of the valve can be easily accessed by removing the bonnet. These valves are easy to assemble and disassemble. You can repair or maintain different parts of the trunnion valve without removing it from the pipeline.

Side entry ball valves are also known as split body trunnion mounted ball valves. In these valves, the body is divided into two or three pieces that are bolted together like flanges. One piece of the body is always larger than the rest. The larger piece holds the ball as well as the stuffing that goes around the ball.

These valves are easier to inspect and repair as the smaller piece can be removed to access the valve. The bore of the valve is the hole that is found in the middle of the disk or ball. Trunnion mounted ball valves have two types based on bore size. As a result, the required torque of a trunnion mounted ball valve is generally lower than a comparable floating ball valve.

For example: a DN metal-seated floating ball valve would require a significantly bigger actuator than DN comparable trunnion valve, leading to significantly lower costs of the overall package.

Also, the trunnion seat design in general is much more stable which makes it more suitable for extreme conditions. The trunnion-mounted ball valve is more suitable for high pressure applications and bigger dimensions compared to the floating ball.

Furthermore, it functions as an relief valve automatically whenever the pressure in the central cavity is higher than the spring force of the seats. When this happens, the seat springs relieve automatically in order to drain the excess pressure back into the main line.

Off course, a big disadvantage of the trunnion compared to the floating design is associated with its costs; which are significantly bigger.