There are three types of bonnet designs for forged steel check valves. The first one is a bolted bonnet. The valve designed according to this design form, the valve body and the bonnet are connected by bolts and nuts, and the wound gasket (316+ flexible graphite Metal ring connection can also be used when the customer has special requirements. The second design form is the welded bonnet. According to this design form, the valve body and the bonnet are connected with threads, and the customer is fully welded and sealed. The penetration welding connection can also be used when there are special requirements. The third type is the pressure self-tightening bonnet. The valve designed according to this design form has a threaded connection between the valve body and the bonnet, and is sealed with an internal pressure self-sealing ring.

There are three different design structures of check valve, they are lift check valve, ball check valve and swing check valve.