Problems encountered in the use of butterfly valves

1. Since the multi-layered soft and hard composite seal ring is fixed on the valve plate, when the valve plate is in the normally open position, the medium exerts direct erosion on its sealing surface. This erosion of the soft seal strip in the metal sheet interlayer directly affects the sealing performance.

2. Due to structural limitations, this design is not suitable for valves with a diameter of DN200 or smaller. The reason is that the overall structure of the valve plate is too thick, resulting in high flow resistance.

3. According to the principle of the triple-eccentric structure, the seal between the valve plate’s sealing surface and the valve seat is maintained by the torque generated by the drive mechanism, which presses the valve plate against the valve seat. During forward flow, the higher the medium pressure, the tighter the seal. However, when the medium flows in reverse, if the unit normal pressure between the valve plate and the valve seat becomes less than the medium pressure, leakage occurs.

The high-performance triple-eccentric double-direction hard-sealed butterfly valve is characterized in that the valve seat seal ring consists of multiple layers of stainless steel sheets on both sides of a flexible T-shaped seal ring. The sealing surfaces of the valve plate and the valve seat are conical in shape, with temperature- and corrosion-resistant alloy materials welded onto the conical surface of the valve plate. The spring fixed between the adjusting ring and the pressure plate is assembled together with the adjusting bolts on the pressure plate.

This structure effectively compensates for the tolerance between the shaft sleeve and the valve body, as well as the elastic deformation of the valve stem under medium pressure. It solves the sealing problems that occur during the bidirectional transfer of media. The use of multiple layers of stainless steel sheets on both sides of the flexible T-shaped seal ring provides the advantages of both metal hard sealing and soft sealing. It ensures zero leakage sealing performance at both low and high temperatures.

Tests have shown that during forward flow (when the direction of medium flow is the same as the rotation direction of the butterfly plate), the pressure on the sealing surface is caused by the torque of the drive mechanism and the medium pressure acting on the valve plate. As the forward medium pressure increases, the conical surface of the valve plate presses more tightly against the valve seat, resulting in better sealing performance. During reverse flow, the seal between the valve plate and the valve seat is maintained by the torque of the drive mechanism. As the reverse medium pressure increases, if the unit normal pressure between the valve plate and the valve seat becomes less than the medium pressure, the stored elastic energy of the spring in the adjusting ring compensates for the pressure between the valve plate and the valve seat, providing automatic compensation. Therefore, unlike existing technologies that install multi-layered soft and hard seal rings on the valve plate, this new design installs them directly on the valve body. Adding an adjusting ring between the pressure plate and the valve seat is an ideal way to achieve double-direction hard sealing. It has the potential to replace gate valves, globe valves, and ball valves.