Calculations of hydraulic losses in plastic pressure pipes

Abstract

Local hydraulic losses at pipe joints are usually calculated by increasing an actual pipe roughness. This assumption is false. The value of hydraulic losses at pipe joints is not dependent on Re value in a wide range of Reynolds number, while friction losses increase when the value Re decreases. In this case, actual hydraulic losses are higher than the calculated ones. The losses of hydraulically smooth pipes at the joints should be considered as the losses due to local obstructions to be calculated separately. Local hydraulic losses at joints depend on the type of a joint, the pipe diameter and length as well as on the Reynolds number. In supply networks (d > 90 mm) the coefficient x of local losses may be considered constant when v = 1,0 m/s. The formulas offered for the increase of the hydraulic friction factor in the case of local obstructions are calculated for socket and muff pipelines. The values of the hydraulic friction factor l from these formulas are in good agreement with the experimental data. The technique offered for calculating the hydraulic losses allows simple and reliable loss calculations to be made for the networks of water supply and gas pressure pipes. It has been found that applying the above methods the computational load may be decreased many times compared to commonly used techniques.