A wide variety of valves are commonly utilised in power plant and other petrochemical industries. Valves are used in all piping systems to meet safety requirements or control purposes. Understanding the role of each valve type will have a crucial impact on the equipment, plant reliability, process quality, as well as the economics of the entire activity. It is necessary to select the appropriate valve type of a particular flow characteristic for different applications. Also, valve operation impacts the process and the system. Understanding the issues encountered with valves is crucial for diagnosis, troubleshooting and identifying the maintenance needed for the specific type of valves.