Piping Design Engineering is a Sub-engineering branch that comes under the mechanical/chemical engineering, and it can be specifically for Power Piping and oil & gas refinery piping and further some Sub specific types of piping come under this. (like utility area, Sulfur area, tank farm area, CCU etc.) Piping design http://felixdrtza.full-design.com/AM3D-Mechanical-Consultant-Multi-Disciplinary-Plant-Engineering-Piping-Design-Services-47615838