Effect On Drainage Capacity Of Dn110 Single Stack Drainage System By The Installation Of Pipe Offsets

In order to increase the resistance for the drop water,so as to reduce the velocity of water flow,some pipe offsets were installed on the drainage systems in parts of high-rise buildings.But it still gets some disagreement in the industry about whether the pipe offsets can improve the drainage capacity or not.To make sure the fair use of it,the drainage capacity should be tested for the drainage system with pipe offsets.The dn110 single stack drainage system,which constructed by U-PVC pipes and in service of 33 layers with a height of 103.7m,was taken into consideration in the experiment by the constant flow test method.Firstly,the terminal velocity theory in the U-PVC vertical pipe was verified.Secondly,the work mechanism of the pipe offset was analyzed by observing the effect on average velocity of drop water and pressure fluctuation in the system,as well as the density of the mixture.Thirdly,the optimum installation method for the pipe offsets was studied by comparing the drainage capacity under different pipe offsets installation conditions.Finally,the effect on the drainage capacity by the installation of Air Ventilation Valve for the dn110 single stack drainage system with pipe offsets setting on the vertical pipe every six layers was also analyzed.The results indicated that:For the dn110 single stack drainage system,the average flow velocity of drop water increased first and then decreased during the dropping before the discharge volume reached the drainage capacity.The terminal velocity in the U-PVC vertical pipe didn't be discovered.By the installation of pipe offsets,the average velocity of drop water could get decreased.And the effect of it was not only related to the collision between water and pipe offset,but also related to the separation between gas and water in the pipe offset.For the dn110 single stack drainage system,the optimum installation method for the pipe offsets was setting on the vertical pipe every eight layers,the drainage capacity could be 1.95L/s,which improved by 21.88% compared with the dn110 single stack drainage system without pipe offsets.While,by setting the pipe offsets on the vertical pipe every six layers according to the traditional method,the drainage capacity could be 1.65L/s,which only improved by 3.13%.For the dn110 single stack drainage system with pipe offsets setting on the vertical pipe every six layers,by the installation of Air Ventilation Valve on the next 1-3 horizontal branches under each pipe offsets could help to improve the drainage capacity.The optimum installation way for the Air Ventilation Valves was setting on the next one horizontal branch under each pipe offset,the drainage capacity could be 2.10L/s,which improved by 27.27% compared with the system without Air Ventilation Valves.