H Azeem
Sustainability Implications of Piping System Design
H Azeem
Sustainability Implications of Piping System Design
Industrial plants use up to 37% of global total energy. Piping systems comprise of 65% (by volume) of these plants. Eco-efficient design and construction of piping systems will remain central to sustainability in the industrial sector in conventional industrial plants, like chemical plants and oil refineries, as will sustainable technologies such as Combined Heat & Power (CHP) or Carbon Capture. This research looks at the ASME (B31.3) piping design code and the current best practices for energy (carbon) efficiency in the designing of piping systems for industrial plants. The only constraint the ASME code presents is a minimum wall thickness for the safe design of pipes. No cap is placed on the use of energy (carbon) or material resources. Therefore, the aim of this research is to propose measures for the energy (carbon) efficient design of piping systems. The study of alternative pipe materials, though promising for eco-efficiency, is not covered in this work and carbon steel is taken as a given material. Sample calculations are performed to compare design alternatives by varying pipe diameter and thickness against pump size—a sensitivity analysis to see whether carbon impacts are sensitive to pump characteristics or pipe. Various pipe diameters and thicknesses are plotted against a manufacturer’s pump curves to identify duty points on system curves. A sample case of choosing an optimal ‘pump and pipe size combination’ is presented for given service conditions. As an output, the research delivers a procedure for designers to choose a combination of pump and pipe size and read off values of energy (KWh) and carbon (tCO2e) to help them design energy efficient piping systems. Whole-system life-cycle costing, in which all system benefits are properly factored in the long run, is widely accepted in principle but this research has found it is almost always ignored in practice. On its part, the popular notion of ‘deploying big pipes and small pumps instead of the original design’s small pipes and big pumps’ for energy efficiency is found overly simplistic and sometimes wrong. An optimal combination of pump and pipe size requires careful consideration of various combinations for a given whole system, as increasing a pipe size beyond a certain size for a given pump may be sub-optimal. Also when high pressure results in extra thick pipe as per code constraint, energy efficiency might be achieved by choosing the next bigger pipe to maintain the same internal diameter (that is putting extra thickness outside the pipe, not inside). Key Words: Piping Systems, Energy Efficiency, Pipe diameter optimisation