The butterfly valve is popular because of its fast opening and closing speed, self-sealing tendency and light weight. It is widely used in large and medium caliber equipment in medium and low pressure. Especially in recent years, the butterfly valve with three-dimensional eccentric hard sealing has greatly improved the working temperature of butterfly valve.
But the butterfly valve has two problems:
Firstly, the valve opening and closing torque is large due to the radial eccentricity of the valve rod and the friction force of the sealing surface;
Secondly, due to the gap between the valve rod and the valve body and the interference deformation of the butterfly plate and the valve rod when the butterfly plate is under pressure, the sealing performance of the butterfly valve feeding medium from the side with the valve rod is good, so the sealing requirements cannot be achieved when the medium is fed reversely. It is used to be called one-way sealing, which is not only inferior to ball valve, gate valve and other two-way sealing valves, but also can not meet the needs of users in many cases. More importantly, it does not meet the requirements of the standard.
GB / T13927 stipulates that the “butterfly valve” shall introduce medium in the direction which is most unfavorable to sealing and apply pressure. The butterfly valve with symmetrical valve can be pressurized in any direction.
It can be seen that the butterfly valve which can only be sealed in one way is unqualified according to the requirements of GB / T13927.