Valve selection is a major activity of a epc project cycle which begins as early as FEED(front end engineering and design) phase of a project where P&ID’s are designed. P&ID forms the basic document for initiation of valve selection and purchase phase .The P&IDs are designed on a system approach usually which show all major equipment, interconnecting piping, and the required valves.FEED engineer or for a large project a specialist engineer for valve also known as Valve Engineer is assigned to the task.
Valve Engineer will be responsible to select the most appropriate valve in co-ordination with process engineers, control system engineers and purchase engineers. Valve engineer will have the sufficient knowledge about the know-how of the proposed system.The top most priority for selection of a valve will be given to process variables.
Valve engineer ,for selection of a valve for a particular system identifies all the process variables from the PFD’s (process flow diagrams).
PFD’s show various process variables which include:
Application system identification
Media flow (fluid phase)
with these basic inputs ,governing standards and design basis ,a valve engineer filters and selects the most appropriate
The cost of replacing a valve from service is far more than the cost of valve itself, hence careful selection of valve shall be the utmost priority of the specification engineer.