The Structure & Working Principle of Hard-Sealed Ball Valves
What are the structure and working principles of the hard-sealed ball valve?
1. Overview
We commonly used the fixed ball valve and floating ball valve. Because the ball valve has the characteristics of small flow resistance, fast opening and closing speed and simple operation, it is very widely used in many industries, such as petroleum, chemical, power stations and petroleum, and natural gas pipeline. The seal of ball valves is formed by the pre-set preload force between the ball, the seat and the force caused by the fluid pressure on the seat sealing surface. Generally, the preload force of ball valves is formed by setting elastic components, such as disc springs and column springs between the seat and the valve body. When the hard-sealed ball valve is in the opening and closing process, the preload always acts on the surface of the sealing pair, resulting in the opening and closing torque of ball valves being greater than that of other types of valves. At the same time, the preload also increases the wear of the seals and affects the service life of the ball valve. In order to overcome the above shortcomings, a screw drive mechanism is designed between the ball and the seat.
2. The working principle
The ball valve consists of the body, cover, ball, seat and stem, etc.
The axis movement of the seat in the valve body is accomplished by a spiral drive mechanism. Specifically, a circular transmission disk is installed on the ball. A spiral groove is provided on the transmission disk, which rotates with the ball. A transmission pin is arranged above and below the seat, and the transmission pin is engaged with the spiral groove on the transmission disc. When the valve is opened and closed, the ball turns and drives the drive disk to turn with it. When the valve is closed, the spiral groove on the drive disc pulls the seat to the ball through the drive pin on the seat, and close contact with the ball at the closing moment to achieve sealing. At the moment of opening, the spiral groove pushes the seat away from the ball through the drive pin on the seat for frictionless operation.
According to the fixed ball valve stem torque calculation formula
MF =MQC +MFT +MZC (1)
MF – the valve stem torque of ball valves, N·mm
MQC – fixed ball valves between the ball and the seat sealing surface friction torque, N·mm
MFT – the friction torque between packing and valve stem, N·mm
MZC – the friction torque generated by bearing, N·mm
How about the structure and working principle of the hard-sealed ball valve?
As the valve seat moves along the axis using a spiral transmission mechanism, there is no force between the valve seat and the ball in the process of opening and closing. Formula (1) is simplified as MF =MFT +MZC (2). It can be concluded from the calculation of equation (2) that the valve stem torque is greatly reduced.
3. The design of the screw transmission mechanism
The upper and lower parts of the seat are provided with 2 transmission pins which engage with 4 spiral grooves on the drive disk. The pitch of the spiral grooves is 1mm. The position of the spiral groove is the starting point of the drive pin on the seat when the valve is in the open position. The drive disc is connected to the stem by a key and rotates with the ball. When opening and closing the valve, the ball and the transmission disc rotate. The power is transmitted to the seat through the spiral groove on the transmission disc so that the seat is along the axis of reciprocating motion.
4. Conclusion
Compared with the prior art, the hard-sealed ball valve has the characteristics of a compact structure, small size and light weight. The structure also has the functions of bidirectional sealing and fire prevention. The most important thing is to realize the ball and the valve seat are basically frictionless, prolong the service life of the valve, and reduce the opening and closing torque of valves. The structure is especially suitable for the large-diameter electric ball valve. The energy-saving effect is very significant.
1. Overview
We commonly used the fixed ball valve and floating ball valve. Because the ball valve has the characteristics of small flow resistance, fast opening and closing speed and simple operation, it is very widely used in many industries, such as petroleum, chemical, power stations and petroleum, and natural gas pipeline. The seal of ball valves is formed by the pre-set preload force between the ball, the seat and the force caused by the fluid pressure on the seat sealing surface. Generally, the preload force of ball valves is formed by setting elastic components, such as disc springs and column springs between the seat and the valve body. When the hard-sealed ball valve is in the opening and closing process, the preload always acts on the surface of the sealing pair, resulting in the opening and closing torque of ball valves being greater than that of other types of valves. At the same time, the preload also increases the wear of the seals and affects the service life of the ball valve. In order to overcome the above shortcomings, a screw drive mechanism is designed between the ball and the seat.
2. The working principle
The ball valve consists of the body, cover, ball, seat and stem, etc.
The axis movement of the seat in the valve body is accomplished by a spiral drive mechanism. Specifically, a circular transmission disk is installed on the ball. A spiral groove is provided on the transmission disk, which rotates with the ball. A transmission pin is arranged above and below the seat, and the transmission pin is engaged with the spiral groove on the transmission disc. When the valve is opened and closed, the ball turns and drives the drive disk to turn with it. When the valve is closed, the spiral groove on the drive disc pulls the seat to the ball through the drive pin on the seat, and close contact with the ball at the closing moment to achieve sealing. At the moment of opening, the spiral groove pushes the seat away from the ball through the drive pin on the seat for frictionless operation.
According to the fixed ball valve stem torque calculation formula
MF =MQC +MFT +MZC (1)
MF – the valve stem torque of ball valves, N·mm
MQC – fixed ball valves between the ball and the seat sealing surface friction torque, N·mm
MFT – the friction torque between packing and valve stem, N·mm
MZC – the friction torque generated by bearing, N·mm
How about the structure and working principle of the hard-sealed ball valve?
As the valve seat moves along the axis using a spiral transmission mechanism, there is no force between the valve seat and the ball in the process of opening and closing. Formula (1) is simplified as MF =MFT +MZC (2). It can be concluded from the calculation of equation (2) that the valve stem torque is greatly reduced.
3. The design of the screw transmission mechanism
The upper and lower parts of the seat are provided with 2 transmission pins which engage with 4 spiral grooves on the drive disk. The pitch of the spiral grooves is 1mm. The position of the spiral groove is the starting point of the drive pin on the seat when the valve is in the open position. The drive disc is connected to the stem by a key and rotates with the ball. When opening and closing the valve, the ball and the transmission disc rotate. The power is transmitted to the seat through the spiral groove on the transmission disc so that the seat is along the axis of reciprocating motion.
4. Conclusion
Compared with the prior art, the hard-sealed ball valve has the characteristics of a compact structure, small size and light weight. The structure also has the functions of bidirectional sealing and fire prevention. The most important thing is to realize the ball and the valve seat are basically frictionless, prolong the service life of the valve, and reduce the opening and closing torque of valves. The structure is especially suitable for the large-diameter electric ball valve. The energy-saving effect is very significant.
