Analysis and research on performance test of backflow preventer

1. An overview of the

In the water supply pipeline, backflow preventers are installed in some important water pipelines to prevent backflow from polluting the water source.For some connection between construction water and municipal water supply, backflow preventer device can effectively cut off backflow between downstream end water and upstream end water, prevent backflow of construction water from polluting municipal water supply, so as to ensure the quality and safety of municipal water supply.

2. Structural performance

The key function of backflow preventer is to prevent backflow of water at the downstream end or infiltration of water at the upstream end when there is no water forward flow or abnormal water supply in the pipeline, so as to effectively eliminate the possible danger of backflow pollution.The reverse flow preventer shell adopts a diversion structure to drain the backflow and critical backflow water out of the pipe, completely preventing the backflow of the downstream end water or infiltration of the upstream end, so as to avoid backflow pollution and ensure the safety of water supply.The backflow preventer consists of two separate check valves and a cavity and hydraulically controlled drain valve (figure 1).There is no water medium flow in the water supply pipeline system, and when the downstream pressure may be higher than the upstream pressure and there is backflow of water at the downstream end, it will be discharged through the intermediate.If one of the check valves fails to turn upside down and fails to close, the downstream end water will also be discharged through the intermediate.

According to the role of the backflow preventer, the key to its product performance is to ensure that the drainer is properly opened in backflow and closed when the forward flow is closed.The backflow preventer can not be opened in the middle of the drainer can not guarantee the backflow preventer partition effect, at the same time, the displacement of the drainer is too small, high pressure backflow water at the downstream end of the pipe may infiltrate into the upstream end.Moreover, the overall strength of the product, the strength of the disc and the outlet disc, and the positive differential pressure performance of the sealed inlet/outlet check valve when it is closed are the basic indicators to ensure the long-term normal use of the valve.In order to save energy, reduce emission and improve efficiency, the valve as a whole should also achieve as small as possible head loss.