How to determine whether the valve is internal or external leakage?

The inner leakage of an electric valve generally refers to that when the electric valve is completely closed, there is still a situation where the medium flows out from the flow path outlet of the electric valve, leaks or drips, etc.. In terms of popular points, it is not closed, and the seal is not good. ! The cause of this failure is usually caused by the erosion of the medium or the presence of impurities. Even if the electric valve screw (stem) is screwed into place, the medium can flow because there is still a gap between the valve body and the valve body.

The external leakage of the electric valve generally refers to the leakage of the medium when the electric valve is completely closed or opened and the external valve seal of the electric valve is filled. That is, between the electric valve and the connecting flange or the connecting thread, the seal is not strict enough to cause the medium to flow out of the connecting sealing surface, or the medium caused by the poor seal between the stem and the Grun (that is, the pressure cover on the stem of the valve stem). Leakage, or external leakage caused by trachoma on the blank body blank, and external leakage due to wear of the valve body caused by media erosion.

The main factors affecting the dead zone of an electric valve are: friction, swaying, twisting of the valve shaft, and the deadband of the amplifier. Various control valves are not sensitive to friction. For example, rotary valves are very sensitive to friction caused by high seat load. However, for some types of seals, a high seat load is necessary to obtain a closed class. In this way, this kind of valve is designed to be very bad, and it is easy to cause a large dead zone. The effect on the degree of process deviation is obvious and it is decisive.