An Experiment Study On The Influence Of The Seven-Floor PVC-U Draining Stack Pipe On Trap-Seal

Discharging characteristics of a seven-floor PVC-U drainage system are studied in the thesis. The main water tank in the seventh floor discharges water to the PVC-U drainage system by simulating centralized flow in the most unfavorable theoretical situation. The experiment uses the pressure transmitting instrument to measure the maximum value of pressure change and the mean value of fluctuation pressure charge in drainage system, and uses gauging glass to measure the water height change value around turning on water in water seal of U-trap. The study is mainly conducted from the three following aspects:Firstly, the simulation experiment of PVC-U draining transverse pipe internal pressure undulation under steady pressure. The pressure in the practical drainage system changes frequently, approximating an irregular sine curve, and it is a kind of fluctuation pressure. During a short time (for instance several seconds), this fluctuation pressure pulsates around the mean value. The experiment showed that, PVC-U draining pipe internal pressure is also a kind of fluctuation pressure under steady pressure. But this pressure curve is more regular than the pressure curve in the practical drainage system and its change frequency is relatively slow.Secondly, the simulation experiment under different operational states of the PVC-U drainage system. Data of flow and pressure is recorded through instrument. The draining stack and the draining transverse pipe are analyzed and compared in different operational states, in which states the extreme value-pressure curve and the mean value- fluctuation pressure curve are also compared, and the pressure loss of the draining transverse pipe and the relationship of the pressure and the loss of U-trap are analyzed as well.Thirdly, the simulation experiment of the losses of U-trap with the main water tank draining once and successive several times respectively. The major factors of U-trap dynamic draining are positive pressure splattering and negative pressure suction which change alternatively, and the change frequency is very quick. it is very difficult for water to flow out of the upper limb of U-trap under positive pressure (input joint of draining appliance draining-pipe). But the positive pressure could cause fierce undulation of U-trap water-pressure in the drainage system, thereby water can flow through the U-trap lower limb. In one draining process, the innumerable pressure fluctuation causes the negative pressure, which leads to suction, then water in the U-trap flows through the draining branch pipe, and it is the primary factor of the dynamic U-trap loss. With the increase in the number of draining, the loss of U-trap is getting smaller and smaller, until it stops changing. The following can explain for it : first, the negative pressure suction of the fluctuation pressure has no enough time to discharge the suction water from the draining branch pipe; second, along with the time passed and the suction times of fluctuation pressure increased, the negative pressure value which the loses of U-trap need will be larger and larger.