The inside leakage of the valve is to point to when the valve is shut completely commonly hind, still have medium to flow from the outlet of valve diameter to flow, leakage or drip to wait for a circumstance. The fault is caused by erosion of the medium or impurities. Even if the stem screw in place, because there is still a gap between the spool and the valve body, so the medium can flow.
Valve leakage, generally refers to when the valve is completely closed or open, the valve packing of the external sealing parts of medium leakage phenomenon. That is, between the valve and the connecting flange or connecting thread, the sealing is not strict and causes the medium to flow out of the connecting sealing surface, or between the stem and the valve cover is not strict and causes the medium to leak, or there is trachoma on the valve body blank, and because of the medium erosion causes the valve body to wear and the leakage phenomenon.