Trunnion Ball Valve – How They Work – The Ultimate Guide

The trunnion ball valve is known to be an important instrument in both industrial and residential use. It is used for governing the fluid flow in a pipeline, which can be steam, gas, or even oil. It’s a quarter-turn design that comes with a ball that is capable of rotating 90 degrees on its own axis. The rotation either block or enable the fluid flow. The center of these special valves has a spherical disc design that rotates to control the start-stop flow cycle.

The disc, commonly known as a ball, is crafted with a small bulging shaft. This shaft can be seen at the top and bottom that is mechanically supported. The position of a hole in the center of the ball is the main controller of flows in this case. 

Trunnion-mounted ball valves are very useful in industries due to their unique working mechanism. The best thing about these devices is that they require such shut-off operation due to their versatility. Below we have discussed everything about the working of trunnion ball valves and some other important information.

Basic Working of the Trunnion Ball Valve

A trunnion valve is basically used to control or regulate the shut-off cycle. This serves the purpose of controlling the flow of fluids in any type of pipeline. It contains the elements that are must require to enable or disable fluid flow through the pipe. The valve is designed by a top trunnion ball valve manufacturer to integrate pipe or tube sections in order to perform this function.

The Working Structure Of Trunnion Ball Valve

Trunnion ball valves have a framework that is much similar to that of traditional ball valves. The typical ones differ in the only way that they already have enough mechanical anchor points for the purpose of endorsing the ball that is solidly supported on its x-axis by the two ends. It secures it and makes managing the valves pretty easy.

The working design of the trunnion-mounted ball valve includes dismal tended shafts at the top and bottom as mentioned above. This makes it particularly suitable for larger diameters as well as higher pressures. The ball is held in place in the trunnion mounted design by squeezing the seat rings only at two ends.

Because of its flexibility, the ball allows a good amount of movement. When in use, it floats downstream more toward the seat ring in order to form a seal. If the loads on the floating ball are significantly higher, the seat rings will not at all be able to provide the necessary support needed by the ball. This is where the trunnion’s power comes into solid play. The seat rings in a trunnion design are the parts that float in contrast to the traditional design in which the ball floats.

Working Features of Trunnion Ball Valve 

The trunnion-mounted ball valve has numerous operational features. Among the most important  ones are:

Antic Static

Due to the fact that the stem and ball of a trunnion ball valve are suspended on some non-metallic parts, there is a bright possibility of a static charge accumulating on the stem/ball. An antistatic ball and metal spring are both included in the design in order to maintain the metal-to-metal contact. This contact takes place between the rotating stem or ball and the valve body. As a result, it aids in grounding the charges to the valve body.

Blowout Proof Stem

The trunnion valve stem is designed with a shoulder at the bottom. It is protected by the filling box in the event that the stem accidentally blows out under certain working conditions. This can happen in a wide variety of certain ways. 

Emergency Seal

A trunnion-mounted ball valve is designed with sealant injection. It is present at the seat and stem. In the event of a failed seal, injection sealants can be reliable and work as a temporary emergency seal.

Fire-safe design

The trunnion ball valve design has been tested and certified as fire-safe. It is reliable for preventing fire spread as well as pollution. The product has been tested and it has been found to be compliant with API 607 or API 6FA.

Types of Trunnion Ball Valve

The body of the configuration characteristics indicates how a ball valve can be used as well as the ease of inspection along with certain replacements. Three types of trunnion ball valves will be investigated which is based on the mentioned parameters:

Top Entry Trunnion Ball Valve

This trunnion valve has a one-of-a-kind design that allows the ball to be assembled from the top. They are primarily made of cast metal. The ball valve has a removable bonnet cover that sits atop the ball valve. By removing the bonnet, you can easily access all the interior parts. The valves are simple to take apart and can be reassembled. The trunnion ball valve can be easily maintained and repaired by simply removing it from the pipeline.

Side Entry Trunnion Ball Valve

The side entry design is also known as a split body trunnion-mounted ball valve. It constructs its ball from the side. They are frequently made of forged metal. The body is frequently divided into three or two pieces and these are joined together like extensions in this particular design. A section of the body is significantly larger than the rest of the design.

This larger piece houses the stuffing that wraps around the ball as well as the ball itself. They are easily repairable and inspectable due to the reason that the smaller piece can be pulled out to access the valve.

Welded body trunnion ball valve

The welded body design is primarily intended for gas transmission via buried pipelines. They come in larger sizes ranging from about 30 to almost 60 inches. They have medium pressure classes of up to 900 psi according to ASME. RAM materials for the design can be either centrifugal castings or forgings.

They are made of various materials, some of the common ones are martensitic stainless steel and carbon steel. The valve’s main technical features include an anti-blowout stem and a valve seat design that is available in three different design patterns:

  • DPE (Double Piston Effect)
  • SPE (Single Piston Effect)
  • DUAL (SPE upstream and DPE downstream)


Trunnion-mounted ball valves are one of the best regulating inventions that provide tight shut-off in large, high-pressure, critical operations. Not only this but these devices are also specialized low-pressure applications. The valve seats are always in contact with the ball, resulting in tighter seals that are best to prevent any kind of leaks.

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Aniket jain

Hi there, My self Aniket Jain. A virtual SEO expert, content writer, and digital marketer. Works with lots of passion, hardly dedicated to what's best and what's next ✌️. Hope u all like my work ✌️

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