What is a trunnion ball valve?
Ball valve is a stop valve, which uses a rotating ball with a hole. In trunnion ball valves, the top and bottom of the ball have small protruding shafts, which are mechanically supported. This makes it suitable for higher pressures and larger diameters. Most ball valves in the world have no trunnion design. They are called floating ball valves. In this design, the ball is held in place by seat ring compression on both sides. The ball has a certain degree of freedom of movement. During use, the steel ball floats slightly downward on the stay ring and forms a seal. When the load on the ball becomes very high, the stay ring will not be able to support the ball, which is where the trunnion design provides a solution. In the trunnion design, the ball no longer floats, but the seat ring floats. The advantage of this solution is that its working torque is lower than that of floating ball valve. Considering the cost of actuators transmitting lower torque, lower operating torque can reduce the cost of the whole system. However, Trunnion Ball Valves themselves will usually have a high cost.
Five differences between floating ball valve and trunnion ball valve
The float valve and the trunnion ball valve are easily distinguished in appearance. If there is a fixed shaft at the bottom of the valve body, it must be a trunnion ball valve.
If there is a grease injection device on the ball valve body, it is basically a trunnion ball valve. However, if there is no oil filling device, can it be said that it must be a floating ball valve? This is incorrect because small valves (e.g. 2 “150Lb Trunnion Ball valves are usually not filled with the injection device).
2. Sealing surface
Since the ball of the floating ball valve is floating, under the pressure of the medium, the floating ball will move and lean against the downstream valve seat. Therefore, the seal of floating ball valve belongs to one-sided seal. The trunnion ball valve cannot be moved, so both sides of the trunnion ball valve must be sealed.
Due to different sealing principles, the requirements for sealing surface materials of the two ball valves are also different, especially the sealing surface of the floating ball valve must be able to bear the pressure generated by the floating ball.
3. Working principle
Floating ball valve has only the upper valve stem, and the ball can have a small displacement, so it is called floating ball valve. The trunnion ball valve has another rod at the bottom of the ball to fix the position of the ball, so the ball cannot move.
The sealing of the floating ball valve is realized by the pressure of the medium. When the ball valve is closed, the floating ball is pressed on the sealing surface under the action of pressure to realize the sealing. The ball will not displace, but the floating valve seat will move and press against the ball under the action of medium pressure, so as to realize sealing.
4. Applicable occasions
Floating ball valve is suitable for medium and low pressure, usually with small diameter. Trunnion Ball valve can be used under high pressure, and the size can reach 60 inches.
Trunnion ball valve is a double discharge (DBB) valve, while floating ball valve only seals the downstream side. Trunnion Ball valve can block upstream and downstream media. When the pressure in the middle chamber is greater than the elastic force of the valve seat, push the valve seat away to release the pressure in the chamber to ensure safety.
For floating ball valves, Trunnion Ball valves are usually used for longer time, smaller size and easy to operate.
Trunnion ball valve also has the function of automatically releasing pressure. When the medium temperature in the valve rises and causes abnormal pressure rise, trunnion ball valve can automatically release pressure without safety valve, which is very important to ensure safety. Industrial production.
China trunnion ball valves manufacturer www.sfutube.com supplies trunnion ball valve for industrial use, in kinds of materials such as carbon steel, stainless steel, alloy steel, etc.