1. Appearance
1.1. The floating ball valve and the trunnion mounted ball valve are still easy to distinguish in appearance. If the valve body has a lower fixed shaft, it must be a trunnion mounted ball valve. (You can refer to the appearance of the ball valve from RXVAL Valves).
1.2. If there is a grease valve on the ball valve body, it is basically a trunnion mounted ball valve.
But the reverse is not true. It is not correct to have a floating ball valve without a grease valve, because a small size such as a 1″ 300LB trunnion mounted ball valve usually does not have a grease valve. (You can refer to the appearance of the RXVAL ball valve)
2. Working Principle
2.1 The ball of the floating ball valve has only the upper stem, and the ball has no supporting shaft. Under the action of the pressure difference, the ball can be slightly displaced, so it is called a floating ball valve.
There is also a fixed shaft at the bottom of the trunnion mounted ball valve, which fixes the position of the ball, so it cannot be displaced, so it is called a trunnion mounted ball valve.
2.2 The ball of the floating ball valve is displaced due to the pressure of the medium, and is tightly attached to the valve seat to achieve sealing. It is necessary to consider whether the material of the seat can withstand the working pressure.
The ball of the trunnion mounted ball valve is fixed, and the seat is moved by the pressure of the medium, and it is tightly attached to the ball to achieve sealing.
3. Function and Using
3.1 The floating ball valve is suitable for medium and low pressure, and the diameter is small; the trunnion mounted ball valve can withstand up to 2500LB, and the size can reach 60 inches. For example, the large-diameter and high-pressure ball valve of RXVAL is trunnion mounted ball valve.
3.2 Trunnion mounted ball valve can realize the function of double Blood and Bleed, while the floating ball valve is mostly one-way seal. The trunnion mounted ball valve can block the medium at both upstream and downstream ends at the same time. When the pressure in the cavity of the valve body is greater than the tightening force of the spring of the valve seat, the valve seat will be pushed open to release the pressure in the cavity to ensure safety.
3.3 Trunnion mounted ball valves usually have a longer life than floating ball valves. According to user feedback, RXVAL’s fixed ball valve has been used for 10 years without any problems.
3.4 The torque of the trunnion mounted ball valve is smaller than that of the floating ball valve, so the operation is more labor-saving.
3.5 The trunnion mounted ball valve above 4 inches is equipped with a seat grease valve, but the floating ball valve does not.
3.6 The sealing performance of the trunnion mounted ball valve is more reliable: the PTFE single material sealing ring is embedded in the stainless steel valve seat, and the tail end of the metal valve seat is provided with a spring to ensure sufficient pre-tightening force of the sealing ring. The valve continues to ensure good sealing performance under the action of the spring.
3.7 The trunnion mounted ball valve has a grease valve, which has the function of injecting sealing grease when the valve leaks.
3.8 RXVAL friendly reminder, If the ball valve of the same specification, the trunnion mounted ball valve is generally more expensive than the floating ball valve.
Floating Ball Valve Structure
Trunnion Mounted Ball Valve Structure
Post time: Jul-06-2022