Antifouling Block Valve (also known as backflow preventer) is a safety device that prevents fluid backflow and contamination through mechanical structure. It is widely used in water supply systems, fire protection systems, and industrial pipelines. Its core function is to ensure water quality safety and prevent sewage and pollutants from flowing back to clean water sources due to pressure fluctuations or siphon phenomena.
Structural Composition
A backflow prevention isolation valve typically consists of two check valves connected in series and a drain valve (or safety relief valve). Some models also include a transition section. Its core structure achieves dual protection against backflow contamination through the synergistic action of the double check valves and the drain valve:
Double Check Valves: When one check valve fails to seal, the other maintains a seal, preventing backflow.
Drain Valve: Located between the two check valves, its opening and closing are controlled by pressure differential. During normal water supply, the check valves experience local head loss, causing the pressure in the intermediate chamber to drop below the inlet pressure. This pressure differential forces the drain valve to close, allowing normal water supply. In case of abnormal pressure (e.g., the outlet pressure exceeds the intermediate chamber pressure), even if both check valves fail to seal, the drain valve automatically opens to release backflow and creates an air gap, completely preventing contaminated media from flowing back into the upstream water supply system.
Working Principle
The working principle of the anti-pollution isolation valve is based on physical isolation and pressure difference control, specifically in the following two scenarios:
Normal Water Supply State:
Due to local head loss, the pressure in the intermediate chamber of the check valve is lower than the inlet pressure. The pressure difference drives the drain valve to close, and the pipeline supplies water normally.
Abnormal Pressure State (e.g., the outlet pressure is higher than the intermediate chamber pressure):
Even if both check valves fail to seal, the drain valve automatically opens, releasing backflow and forming an air barrier to prevent the backflow of contaminated media.
Technical Features
Dual Sealing Mechanism:
The dual check valve design ensures that a seal is maintained even if one valve fails. The drain valve provides a third layer of protection, completely eliminating backflow contamination.
Compact Structure:
The integrated design of the dual check valves reduces size and weight, facilitating installation and maintenance.
Low Resistance Design:
The valve body adopts a streamlined structure, increasing the rated flow coefficient by 30%, reducing pressure drop loss, and saving energy.
Corrosion-resistant materials:
The valve body and core are made of high-strength, corrosion-resistant materials such as stainless steel and alloy steel, suitable for harsh working conditions.
Long service life:
Key components are made of wear-resistant stainless steel, ensuring a long service life.
Modular structure:
Valve components are detachable, facilitating inspection and replacement of seals, reducing maintenance costs.
Visual indication:
Some models are equipped with open/closed status indicators, allowing inspection personnel to quickly determine the valve's status.
Mandatory certification:
Requires compliance with industry standards (such as GB/T 39380 and EN 13959) to ensure compliance with anti-fouling standards.
Application Scenarios
Anti-fouling isolation valves are suitable for applications with strict water quality requirements, primarily including:
Drinking water systems:
Installed at the connection points between municipal water supply networks and user pipelines, and at water tank inlet pipes, to prevent backflow of non-potable water or sewage.
Fire protection systems:
Isolating domestic water from fire protection pipelines to prevent fire-fighting water from contaminating domestic water sources.
Industrial Pipelines:
Suitable for industries with strict water quality requirements, such as chemical and pharmaceutical manufacturing, to prevent cross-contamination.
Special Operating Conditions:
Scenery such as submerged water supply pipe outlets, series booster pumps, or suction pipes for multiple booster devices.
Installation and Maintenance
Preparation Before Installation:
Thoroughly flush the pipeline to ensure it is free of impurities.
Install horizontally for easy commissioning and maintenance.
The valve body should not bear the weight of the pipeline to prevent freezing or human-caused damage.
Maintenance gate valves should be installed at both ends, and a filter should be installed before the inlet (for fire protection systems, the risk of filter clogging needs to be assessed).
At least one end should have a flexible joint.
Drainage Outlet Installation:
The drainage outlet should not be directly fixed to the drainage pipe. It should discharge through a funnel to a ground drainage ditch, with the lower end of the funnel at least 300mm above the ground.
Commissioning Points:
After installation, check the valve's opening and closing flexibility and the drain's sealing performance to ensure normal differential pressure control.
Regular testing:
Valve sealing and response speed need to be tested periodically to ensure long-term effectiveness.
Antifouling Block Valve factory
