Providing right information to the supplier is utmost important for him to deliver the right valves, Hence one has to ensure that supplier is provided with correct information. Information should briefly include.
Media that valve is going to regulate
Pressure of media.
Size of the Pipeline or valve
For Automated valves, Information pertaining to actuation force is also important.
Electrical supply rating available for the MOV (Motor operated valves)
For Pneumatically operated valves please provide information about lowest workable air pressure available at the site.