In chemical/Power plant construction, Piping is very important activity, critical for project schedule. Piping layout can be finalised only after receiving details from equipment manufacturer and piping erection can start after equipment is erected. In view of this Piping becomes Critical activity in plant construction. By evaluating the layout in PDMS software and prefabricating spools the construction time can be considerably reduced .Also by prefabricating critical piping like P91/P92 materials 50% joints can be done in shop floor in controlled condition. This presentation describes the details and advantages of this methodology based on our experience in this field.