Trunnion Ball Valve

Trunnion Ball Valve


The trunnion ball valve (or TRB) is a type of quarter turn valve that uses an enclosed, perforated and internally supported ball to control flow via its seat. The mechanical anchor of the ball acts as the seat, absorbing the momentum from the moving line flow, keeping high friction between the seat and seats, and keeping low running torque levels, enabling even at maximum operating efficiency. Although a trunnion is essentially an aerodynamic valve, its main purpose is as an air-tight seal between the seating and ball and also to provide a smooth and reliable flow of air.


The TRB is ideal for use in air compressors and for reducing the risk of the valve becoming clogged and leaking. The best way to install a TRB valve is to mount it directly to the compressor’s compressor housing. The mounting bracket allows the valve to be mounted directly on the compressor housing, which ensures there are no restrictions around the valve itself when installation is complete. This is because if the valve were placed outside the housing, then it would have to be bolted to a bracket to provide the necessary seal.


A standard TRB will normally have three ball seals; however, a more advanced model may also feature additional seals, which can reduce the risk of cross-threading. The additional seals are usually provided as standard and are mounted either externally or internally. The external seals are made of a special material that allows air to pass through the TRB when the seal is closed and to leave a small opening once the seal has been opened. The internal seals, which are often referred to as ‘ball screws’ are positioned internally within the trunnion, and are responsible for creating a tight seal around the seat and ball, and ensuring that no air can pass through the seat until the seal has been fully opened.


If a ball seal is installed incorrectly, it could cause a serious flow restriction. Therefore, it is vital to ensure that the installation process is performed correctly, or that the seal will have to be removed. It is not as difficult as it sounds to install a TRB valve, and it is not a complicated task that requires the assistance of an expert. If you have any doubts regarding your installation abilities, you can always call a professional trunnion installation expert, who can ensure the trunnion is correctly installed, and that the seals are installed properly. The only time-consuming part of the installation is ensuring that the seals are correctly set up and attached to the trunnions.


There are two types of seals that are usually used on a TRB valve: ‘fully enclosed’interlocking’ seals. The fully enclosed seal provides excellent flow sealing, with the full sealing ring completely encased within the trunnion and providing the maximum sealing power. The interlocking seal consists of a ball screw that is placed inside the sealed ball, and seals the ring onto the trunnion, allowing air to flow freely around the trunnion until the sealing ring has been fully closed.


As with any other valve, proper installation and maintenance of these valves are paramount to ensuring optimal performance and reliable operation. By keeping the seals clean and well maintained, the seals will last longer, and ensure that air flows uninterrupted, allowing the TRB to continue to perform efficiently.