Pipes and Tubes, Alloy Steel Pipe and Tube, Duplex Steel Pipe and Tube Manufacturers in India Pipe is a round tubular used to distribute fluids and gases, defined by a nominal pipe size (NPS or DN) that represents a rough indication of the pipe conveyance capacity; Tube is a round, rectangular, squared, or oval hollow section measured by outside diameter (OD) and wall thickness (WT), both...