What is Mounted Ball Valve?
What is a mounted ball valve?
The mounted ball valve is widely used in petroleum and natural gas pipelines, as well as in petroleum refining, petrochemical, chemical, chemical fiber, metallurgical, electric, nuclear, food, and other devices.
It’s easy and quick to remove the mounted ball valve from the pipelines. And the maintenance is also easy and quick. When the valve encounters failure on the pipeline and needs to be repaired, there’s no need to remove the valve from the pipeline, just remove the middle flange bolts and nuts, take the valve cover and valve stem together from inside the valve body, then remove the sphere and valve seat.
In this way, we can repair the sphere and valve seat, which saves time and reduces the loss in production to the lowest point.
What are the types of mounted ball valves?
The mounted ball valve can be divided into a float ball valve and a fixed ball valve.
The nominal size of the mounted float sanitary ball valve is equal to or less than DN200. There is a compression spring applied to the sphere. The role of the compression spring is to apply preload on the sphere so that the sealing surfaces of the valve seat are in close contact with each other under any circumstances, which provides good sealing performance.
When the wedge angle between the valve seat and the contact surface of the valve body is 10 degrees, the valve seat can self-lock. In the direction of the pipeline, when the valve seat is under relatively large pressure, the valve seat will not have any displacement. So valve of this kind of structure has the characteristics of a gate valve and ball valve. It’s discovered during maintenance and check-up that the valve body and valve seat are prone to leakage.
If we increase the preload of the spring, then it’ll almost certainly increase the closing torque of the ball valve. In order not to increase the closing torque of the ball valve, a rubber O-shaped ring is added to the back of the valve seat sealing surface, which solves the leakage problem of the back of the valve seat sealing surface.
The disadvantage of mounted fixed ball valve is that the spring preload can’t be adjusted and controlled and that there’s a large amount of spring compression when installing, making the installation difficult.
In order to solve this problem, use ANSI 302 instead of 304 for spring materials. ANSI 302 spring has good stiffness and its corrosion resistance is similar to that of the 304 spring. In addition, spring seats and regulating nuts are added. Threads are machined on the outer ring of the valve seat and the spring seat respectively.
Use the regulating nut to press the spring tight into the spring seat and the valve seat suite is loaded into the valve body. Since the spring has been compressed before the installation of the sphere, it’s quite easy to install the sphere. After the installation of the sphere, push the regulating nut out of the spring seat. At this time, the spring has a small preload on the sphere. If the preload needs to be increased, use the regulating nut to adjust.
