Sealing requirements of valve
The sealing performance of the valve is the valve part of the sealing ability to prevent media leaks, it is the most important technical performance indicators. Sealing of valve including three parts: opening and closing pieces and valve seat sealing surface between the contact points; with the Department filler valve stem and the stuffing box; junction body and bonnet. 
Which is called before a leak within the leak, also known as loose relationship, it will affect the ability of the valve cut off media. For the cut valve, the internal leakage is not allowed. Leakage after the two called the leak, that media leaks from the valve to the valve outside. Leakage will result in material losses, environmental pollution, can also cause serious accidents. For the explosive, toxic or radioactive medium, leakage is not allowed, therefore, the valve must have a reliable sealing performance and usual maintenance.