Special valve for preventing medium backflow with backflow preventer produced by Shuoxiang

1、 Introduction to the DF41X backflow preventer produced by Shuoxiang Valve

DF41X backflow preventer, also known as pressure reducing backflow preventer or anti fouling block valve, is a hydraulic control device that strictly limits the one-way flow of water in pipelines. Its core function is to prevent unclean water or contaminated media from flowing back into the clean water supply system upstream due to abnormal pressure in the water supply network (such as pipe burst, pump shutdown, etc.), thereby effectively ensuring the safety of drinking water quality.

It belongs to a high safety level backflow prevention device with two-stage check and intermediate pressure reducing diversion, and its safety level is higher than that of ordinary single/double check valves.

Main standards:

CJ/T 160-2010 "Pressure reducing Backflow Preventer"

GB/T 26003-2010 "General pressure reducing backflow preventer"

Typical applications:

The access point for introducing municipal tap water into buildings.

The connection between the fire protection system pipeline and the domestic water supply pipeline.

The connection between the internal water pipelines of chemical, pharmaceutical, printing and dyeing enterprises and the municipal pipeline network.

The inlet of non drinking water systems such as green irrigation and reclaimed water reuse should be prevented from flowing back into the drinking water system.

2、 Structure and Function of DF41X Backflow Preventer Product Produced by Shuoxiang Valve

The DF41X backflow preventer consists of three main parts connected in series within a valve body, forming a two-stage isolation and a safety relief chamber.

1. First stage check valve

Location: The first valve at the inlet end.

Function: The main check valve allows water to flow forward and prevents water from flowing in the opposite direction. It is the first barrier to prevent backflow.

2. Second stage check valve

Location: Second valve at the outlet end.

Function: Secondary check valve, together with the primary check valve, forms a dual guarantee. Even if the first level fails, it can still provide backup protection.

3. Pressure reducing chamber and automatic drain (the most essential part)

Location: The chamber located between the first and second stage check valves.

Function: This is the fundamental difference between DF41X and ordinary double check valves. The chamber is connected to the atmosphere through an automatic drain valve.

During normal water supply, if the inlet pressure is higher than the pressure inside the chamber, the drainage valve will close and the water flow will pass through normally.

When the second stage check valve leaks, downstream water will leak back into the pressure reducing chamber. At this point, if the first level check valve is sealed properly, the pressure inside the chamber will increase, and the automatic drain valve will immediately open to drain the leaking water out of the valve instead of flowing back upstream.

When the upstream loses pressure (such as pump stop/pipe burst): the pressure at the inlet end decreases. If there is a leakage in the second stage check valve at this time, the pressure in the pressure reducing chamber will also decrease, and the drain valve will also open. Due to the drainage valve being open to the atmosphere, an air barrier is formed between the upstream and downstream, physically preventing the possibility of backflow.

Workflow diagram:

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Normal water supply: Upstream ->[First stage check valve (open)] ->[Pressure reducing chamber (drain valve closed)] ->[Second stage check valve (open)] ->Downstream

Risk of backflow: Upstream (low pressure)<- [First stage check valve (closed)]<- [Pressure reducing chamber (abnormal pressure, drain valve open, water/air discharged)]<- [Second stage check valve (possible leakage)]<- Downstream (high pressure)

3、 Characteristics of the DF41X backflow preventer produced by Shuoxiang Valve

Absolute safety and reliability: Adopting the principle of "two-stage check+intermediate pressure relief", it can form an air barrier in case of backflow risk, fundamentally preventing backflow pollution.

Double sealing: Both levels of check valves use elastic sealing, which has good sealing performance and small leakage.

Automatic drainage: Built in automatic drainage device, no external power required, relying on hydraulic changes to automatically achieve pressure relief and drainage function.

Online inspection: High level products are usually equipped with inspection ball valves, which can be used to check the working status of the valve without stopping the machine.

Small head loss: Optimized flow channel design minimizes water pressure loss while ensuring functionality.

Easy maintenance: The valve body has a compact structure and modular design, making it easy to inspect and maintain.

4、 Use and maintenance of DF41X backflow preventer produced by Shuoxiang Valve

1. Installation precautions

Installation direction: It must be strictly installed horizontally according to the arrow direction marked on the valve body, with the arrow pointing in the direction of water flow. It is absolutely not allowed to install it upside down or vertically.

Installation location: It should be installed in a place that is easy to operate and maintain, away from corrosive environments. The valve body should not bear additional stress beyond the weight of the pipeline.

Space requirement: A sufficient length of straight pipe section (usually recommended to be at least 10 times the pipe diameter) should be left in front of the valve to ensure stable water flow. The drainage outlet downstream of the valve must reserve sufficient drainage space, and the drainage pipe should not be directly inserted into the sewer. A funnel-shaped discharge should be made to observe the drainage situation.

Filtering device: It is recommended to install a pipeline filter (Y-shaped filter) upstream of the backflow preventer to prevent impurities from clogging the check valve or drain.

2. Daily maintenance and testing

Regular inspection: Observe the valve body for any water leakage or external corrosion. Listen for any abnormal noise from the valve during operation.

Functional testing (for models with detection balls):

Micro leakage test: Slowly open the detection ball valve slightly, and there should be a small amount of water continuously flowing out. This proves that the first level check valve is well sealed and the drain is working properly. Close the detection ball valve and the water flow should stop.

Simulated Backflow Test (Caution Required): Close the valve upstream of the backflow preventer and simulate upstream pressure loss. Then open the downstream water point, and at this time, a large amount of water should be discharged from the drainage outlet of the backflow preventer. This proves that the entire anti backflow system is working properly.

Maintenance cycle: It is recommended to conduct a comprehensive inspection and testing every six months to one year.

3. Common faults and troubleshooting

Fault phenomenon

Possible reasons

exclusion method

The drainage outlet continues to leak continuously

1. The sealing surface of the first level check valve is damaged or stuck with impurities

2. The spring inside the drain fails or the seal is damaged

1. Disassemble and clean the first stage check valve, grind or replace the seal

2. Repair or replace the automatic drain module

Excessive pressure difference between upstream and downstream of the valve

1. The valve diameter selection is too small

2. Scaling or blockage inside the valve

1. Verify the design and replace the valve with a suitable diameter

2. Disassemble and clean the inside of the valve

Valves cannot effectively prevent backflow

1. Serious leakage of the second stage check valve

2. Blockage and failure of drainage system

This is a serious malfunction and must be immediately stopped for maintenance! Disassemble, inspect, and replace damaged components of the second stage check valve and drain.