There are two types of cover designs for air drain valves. The first is the bolt-type valve cover, the valve body and the valve cover are connected with bolts and nuts, and the winding gasket (304 clips of flexible graphite) is sealed. Customers have special requirements can also use metal ring connection. The second design form is welded valve cover. The valve designed by sweeping this design form has a threaded connection between the valve body and the valve cover and is fully welded and sealed. Through welding connection can also be used when customers have special requirements.