The floating type and the fixed type of the ball valve mainly differ in appearance, working principle and function use.
1. Appearance
1. The floating ball valve and the fixed ball valve are still easy to distinguish in appearance. If the valve body has a lower fixed shaft, it must be a fixed ball valve.
2. If there is a seat grease valve on the ball valve body, it is basically a fixed ball valve. But not the other way around, it is not correct to have a floating ball valve without a seated grease valve, because a small size such as a 1″ 300LB fixed ball valve usually does not have a seated grease valve.
2. Working principle
1. The ball of the floating ball valve has only the upper stem, and 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 fixed ball valve, which fixes the position of the ball, so it cannot be displaced, so it is called a fixed ball valve.
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 valve seat can withstand the working pressure. The sphere of the fixed ball valve is fixed, and the valve seat is moved by the pressure of the medium, and it is tightly attached to the sphere to achieve sealing.
3. Function and use
1. The floating ball valve is suitable for medium and low pressure, and the diameter is small; the fixed 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 VTON in the United States uses a fixed ball valve.
2. The fixed ball valve can realize the function of double resistance and double row, while the floating ball valve is mostly one-way seal. The fixed ball valve can block the medium at both ends of the upstream and downstream at the same time. When the pressure in the cavity of the valve body is greater than the tightening force of the valve seat spring, the valve seat will be pushed open to release the pressure in the cavity, and the packaging is safe.
3. Fixed ball valves usually have a longer life than floating ball valves.
4. The torque of the fixed ball valve is smaller than that of the floating ball valve, so the operation is more labor-saving.
5. The fixed ball valve above 4 inches is equipped with a valve seat grease injection valve, but the floating ball valve does not.
6. The sealing performance of the fixed 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.
Post time: Mar-08-2022