Working Principle of Backflow Prevention Device
The backflow prevention device is designed to utilize the medium flowing through the inlet check valve to prevent pressure reduction due to mechanical resistance, overflow head loss and decompression, which will results in an inlet pressure that is higher than the pressure of the drain valve cavity. The pressure difference (ΔP) is used to control the drain valve, which is closed to ensure that the backflow preventer maintains a normal water supply. When the pressure difference between the inlet pressure and the drain valve cavity is less than a certain value (such as 0.008 MPa), the medium is in a critical state of backflow. In this instance, the spring of the drain valve automatically opens the valve. The valve effectively prevents backflow of water by discharging it out of the pipe and simultaneously allowing a large amount of air to enter the valve cavity. This creates an air seal that blocks the backflow of media and prevents siphon backflow.
Types of Backflow Prevention Device
Double check assembly:
It is a device comprising two independent check valves in series, designed to prevent the reverse flow of pressurized water in a pipeline.
Low-resistance backflow prevention device:
It features a double check valve structure comprising the main valve and an intermediate automatic drainage device. This device employs hydraulic principles to automatically control the opening and closing of the double check valve and drainage device, thereby preventing backflow of pollution in the intermediate cavity through air isolation.
Reduced-pressure type backflow prevention device:
It comprises two independent check valves and a drain valve, which is designed to permit a strictly limited one-way flow of pressurized water in the pipeline hydraulic control device, which also incorporates an intermediate drainage chamber that can form an air barrier.
Installation and Maintenance
To facilitate installation and maintenance and ensure the normal use of the backflow prevention device, the control valve and the strainer should be installed before the backflow prevention device and the flexible connector, and the control valve should be installed after the backflow prevention device.
At the drain outlet of the backflow prevention device, a drain pipe should be installed about ≥100 mm above the water collecting well. No valve should be installed in the drain pipeline to block the flow of the medium. The drainage diameter of the water collecting well should ensure smooth drainage.
To facilitate routine inspection and maintenance, the low-resistance backflow prevention device should not be installed in the outdoor well. It is recommended to install the backflow prevention device indoor, with sufficient reserved space. Generally the spacing to the lower edge should be ≥300 mm for convenient installation and maintenance.
The low-resistance backflow prevention device can be installed horizontally or vertically and the flow direction of medium in pipelines should be in line with the direction indicated by the arrow marked on the basic valve body.
Before installation, the pipe network must be thoroughly cleaned. Besides, the strainer screen of the strainer must be cleaned regularly.
Application
City water supply: Prevent sewage from flowing back to the clear water pipe due to pressure fluctuations in the pipe network, and protect the safety of water quality.
Secondary water supply: In high-rise buildings and neighborhoods, it stops water from flowing backward when the pump is off.
Fire-fighting system: Make sure that fire-fighting water is clean and doesn't back up.
Industrial production: In industries such as chemical, petrochemical, pharmaceutical and so on, it can prevent the backflow of harmful or corrosive media, to protect the production equipment and piping systems.
Food processing: Prevent cross-contamination between different batches and different raw materials.
Rainwater, sewage network: Prevent backflow of rainwater or treated water, affecting the normal operation of the system.
Agricultural irrigation: Prevent irrigation water from flowing backward into the water source when irrigation is stopped, protecting water resources.
Taloar understands the crucial role of backflow prevention device in safeguarding water quality and preventing damage to production equipment and piping systems. That's why Taloar has designed a kind of backflow prevention device that is lightweight, reliably sealed, which provides isolation and low head loss, and has a compact design that saves installation space and provides convenience.
If you need to keep up with innovations and technological advancements in backflow prevention device, Taloar will support you! For more details, please contact sales@taloar.com or WhatsApp 008618112507128.
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