This is a simple connection method, commonly used in small valve. In two cases:
1. Direct sealing: internal and external threads directly from the sealing effect. In order to ensure that connections do not leak, often lead oil, hemp and PTFE filled with; including Teflon tape, become more widely used; good corrosion resistance of this material, excellent sealing effect, easy to use and preservation, demolition can be completely removed, because it is a layer of non sticky film, than lead oil, hemp superior.
2. Indirect seal: threads power transmission between the two flat washers, washers for sealing function.