Sound knowledge in P&ID is inevitable. The P&ID is the key input for all the piping activities. It is very important for a piping design engineers to read, understand and interpret the P&ID (Process design) in to mechanical system. Preparation of P&ID is the role of process engineer hence piping design engineer are only expected to understand P&ID. There is something called Legend of P&ID which is none other than a drawing that shows the description of the symbols used in P&ID. In condition where symbols are seems to be new and unknown, refer the legend for its description.