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First, the product description:
 HS11X-16T silk mouth backflow preventer is to repair the pipeline and power, the tap water is often interrupted, once the power supply is restored, tap water becomes yellow and dirty, it is due to the process of water, from the fire pipe , Unoccupied buildings or water pipes have not yet used the branch of the backwater, rust water back. In order to allow residents to drink clean water, backflow preventer this device can effectively prevent the occurrence of dirty water in the above circumstances, not only ensure the safety of residents drinking water, but also save water resources. According to the introduction of China Building Standard Design Institute, the Ministry of Construction has revised the relevant national standards and installed "backflow preventer" on the building water supply pipelines.  

Second, the product structure:
 Backflow prevention device is composed of two levels of back-stop system and a drainage pressure relief system. The drainage pressure relief system upper chamber is connected with the inlet end of the first-stage check-back system. 
 The first and second-level check-back system is mainly composed of the valve body, inlet joint, disc, gaskets, springs and so on. 
 Drainage pressure relief system is mainly composed of valve cover, diaphragm, valve core, gaskets, drain, spring, air baffle, etc. The outlet of air baffle must be connected to the drainage pipe network or sewer.

Third, the working principle:
 Backflow prevention device is added in the secondary checkback system, a drainage pressure relief device, so that even if the secondary check seal at the same time damage, it can also play a role in preventing backflow pollution. Its working principle: 
 1. Normal water supply: 
 a. Clean municipal water from the first-class check-back system through the drain to the second-level check-back system to export water to users, the first-level check-in system to import high-pressure water into the drainage diaphragm Cavity, and the diaphragm under the cavity and the first stage check valve outlet (second stage check valve inlet) communicating, due to its existence of a certain pressure difference ΔP1 = 0.035MPa, pushing the valve flap down, drain closed, backflow preventer Normal water supply; 
 b. When the valve after the pipeline without users, water still. Such as the inlet pressure remains unchanged, there is pressure before and after the drain is still closed, such as the inlet pressure drops, the intermediate chamber and the valve differential pressure ΔP1 ≤ 0.022MPa, then the drainage control spring to open the spool, open the drain Allow the middle chamber to drain, keeping ΔP1 at 0.035 MPa. 
 
 2. seal failure: 
 a. Backflow preventer after the pipe network pressure rises above the valve inlet pressure, such as the second check valve seal intact, high-pressure water will not backflow, the diaphragm up and down to maintain the original pressure Poor, drain closed, no pressure relief. When the second check valve seal leak damage, the second check valve before the pressure increases, resulting in lower diaphragm pressure drop across the drain, drain open, drain pressure relief; this time, such as the first stop Check valve seal damage at the same time, as the second-stage check valve back to the high-pressure water has been decompression, it will not back to the first-class check valve. 
 b. When the valve pressure is higher than the pressure before the valve, such as water pressure continues to decline, the pressure on the diaphragm diaphragm pressure drop, the safety control valve to open the drainage spring drainage regulator drainage. When the inlet pressure drops to zero or negative pressure, the drain opens completely, the water is drained and the air enters the vacuum chamber through the drain to prevent siphon backflow.
 
 3. The valve opening pressure ≤ 0.07MPa, the specification provides in the range of 0.06 ~ 0.1MPa, inlet check valve working pressure is 0.035MPa. 
 
 The main shape and installation size: