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://zanderdfeab.slypage.com/9875320/am3d-mechanical-consultant-multi-disciplinary-plant-engineering-piping-design-services