For control valve ,most important is the valve disc designning . The valve disc area is depended on the flow rate of the medium .I give an advice that there are a book on it . If you send me the email id ,I will send it to you by email .
Best Regards
Specialized in special industry valve
For the pipe materials ,I think the best way is have a simple test for the medium . For instance ,put a sample bar into the medium , and observe it's appearance changes .
Specialized in special industry valve