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:
Service
Temperature
Application system identification
Media flow (fluid phase)
Pressure
Flow rates
with these basic inputs ,governing standards and design basis ,a valve engineer filters and selects the most appropriate
Notes:
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.