Connections Used for Bonnet of Forged Steel Gate Valves
Forged steel gate valves are mainly used to cut off or connect media inside pipelines. Forged gate valves are suitable for water, steam, oil, acetic acid, oxidants, urea and other media. There are three types of connection used for bonnet of forged steel gate valves:
1. Bonnet welded forged steel gate valves
Bonnet and body are fully welded for sealing. Bonnet welded forged steel gate valves can realize zero-leakage.
Bonnet is connected with body by using bolts. It also uses twisting gasket for sealing. Bonnet welded forged steel gate valves have the advantages for maintenance.
The bonnet is connected with body by using screw threads. There is a self-sealing ring inside body. The advantage of pressure sealing bonnet forged steel gate valves is that the higher internal pressure is, the better sealing performance is.
Installing forged steel gate valves:
1. When forged steel gate valves with handle are installed on thermal insulating pipelines, the handle must not be downward.
2. Installation site, height, inlet and outlet direction must conform to design requirements. The connection must be firm and tight.
3. Before installation, appearance of forged steel gate valves must be checked. In terms of gate valves whose working pressure is higher than 1.0MPa and used for cutting-off, strength and leakage test should be carried out before installation. The valves only can be used after being qualified. When carry out strength test, test pressure is 1.5 times of nominal pressure. Duration cannot be less than 5 minutes. Only non-leakage on shell and packing, the valves are qualified. When carry out leakage test, test pressure is 1.1 times of nominal pressure.
