Comparison of power density of transmission elements in hydraulic, pneumatic, and electric drive systems

This paper explores the transmittable power of power transmission elements in fluid power and electric drive systems. We consider a simple model for the piping in hydraulic and pneumatic systems that ignores the fittings and auxiliary equipment and the wiring in electric drive systems that ignores the terminals and auxiliary equipment. We analyze the data based on specifications of hoses for hydraulic systems, tubes for pneumatic systems, and cables for electric drive systems from the manufacturers’ catalogs. We survey the outer and inner diameters, mass per unit length, maximum working pressure, mean flow velocity, rated voltage, and rated current to estimate the maximum transmitted power and examine the relationship between the power and the size and weight and calculate the power density. The influences of mass of oil, return lines of hydraulic circuit, materials of pneumatic tubes, and number of cable cores are also discussed. In conclusion, the transmittable power of the elements of all systems can be approximated by a power function for the mass per unit length. The relation between the transmittable power and the mass for hoses, tubes, and wires is similar. The power density of hydraulic hoses and electrical cables is high; the power density of pneumatic tubes is low. Oil in the pipes and return lines of hydraulic systems is not