How the Low Resistance Backflow Preventer works

Here are some of the well-known brands recognized in the backflow preventer industry that are widely recognized and have a great reputation. Although the ranking may change due to time and market conditions, the following brands are generally considered to be among the top brands in the valve industry: Water System Valves and Industrial ValvesThe following more influential first-line brands can be used as a reference, but are for reference only:

Suzhou Neway Valve, Shanghai Qizhong Valve, Shanghai Guanlong Valve, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

<> introduced the structure of a pressure-reducing backflow preventer, the decompression part of the device was improved design, and the piston was used instead of the diaphragm, which solved the problem of not having a long product life caused by the difficult processing of the diaphragm, eliminated the reaction force of the diaphragm, and improved the first-time assembly pass rate of the product.

1. Overview As a valve component that can effectively prevent the unclean water in the branch from flowing back to the main road, the pressure reducing backflow preventer (hereinafter referred to as the backflow preventer) is quite common in developed countries such as Europe and the United States. In China, the main use of ordinary check valves to prevent water backflow is used, and the application of backflow preventers is not very much, especially DN50 usually uses gate valves), in addition to 4 elastic seal test ball valves, constituting a complete decompression type backflow preventer. Under the condition of normal water supply, the water of the main water pipeline is supplied to the user from the check valve at the inlet position through the pressure reduction area to the outlet of the check valve at the outlet position, and the high-pressure water at the inlet valve at the inlet position is directly connected to the upper cavity of the diaphragm of the pressure reducing valve, and the lower cavity of the diaphragm is communicated with the inlet of the check valve at the outlet position.

When there is no user in the pipeline behind the valve and the water is stationary, if the inlet pressure remains unchanged, there is a pressure difference between the front and back, and the valve is closed.

One monk carries water to drink, two monks carry water to drink, and three monks have no water to drink. It's a fable that tells people not to be overly dependent on others, not to think about shifting the blame to others, and that everyone's thoughts are the same. But if the three little monks arrive now, they don't have to worry about running out of water to drink, because now every household has installed tap water, has anyone ever thought about how the water in the upper floors of the house goes up?

Then we have to mention an important role - backflow preventers.

Introduction to backflow preventers

According to the tap water supply equipment, especially the serious backflow pollution of the drinking water pipeline, and there is no effective backflow prevention device, the backflow preventer is developed to strictly limit the water in the pipeline can only flow in one direction. At present, the backflow preventer is mainly divided into two categories: low-resistance backflow preventer and decompression backflow stopper, according to the national standard, the head loss of low-resistance backflow preventer is less than 3 meters, and the head loss of decompression backflow preventer is less than 7 meters.

How the backflow preventer works

When the pressure in the pipe network is normal, the water can easily flow from the inlet to the outlet through two check valves. Because the local resistance of the first check valve makes the pressure in the valve cavity slightly lower than the pressure at the inlet, and the water pressure under the diaphragm is the pressure at the inlet, the water pressure under the diaphragm is greater than the water pressure on the diaphragm, and the safety drain valve remains closed, and the water in the pipeline flows normally. When all valves on the line behind the backflow preventer are closed, the water flow is at a standstill.

At this time, if the pressure at the inlet remains unchanged, the water pressure in the valve cavity is still slightly lower than the water pressure at the inlet, and the safety drain valve is still closed.

When the pressure of the pipeline behind the backflow preventer rises and exceeds the water supply pressure, that is, the so-called back pressure, if the second check valve does not leak, the high-pressure water will not flow back into the valve cavity, and the pressure in the valve cavity still maintains normal flow, so the safety drain valve does not operate to drain water; If the second check valve leaks, the pressure in the valve cavity will increase due to leakage, and the safety drain valve will be drained. This reduces the pressure of the high-pressure water flow on the first check valve, thus effectively preventing the back water from flowing back from the first check valve to the front pipe.

The emergence of tap water has brought convenience to people's lives, people no longer need to go to the river to fetch water to drink, and the tap water is purified, and the water quality is purer. Technology changes life, but many people just enjoy the fruits of science and technology, and few people study how this scientific and technological achievement works. Like a backflow preventer for tap water, few people know how it works, or even know that it exists.

We know that these products are the best when we use these products that bring convenience to people.

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Analysis: What you are talking about is actually called a check valve or a check valve (check valve).

Check valves are only used for one-way opening and closing valves to prevent the reverse flow of fluid media in various pipelines or equipment.

Check valves are widely used and there are many types, and the following are the check valves commonly used for water supply and heat:

1. Spring type: the liquid is from the bottom to the top, relying on the pressure to jack up the spring-controlled valve disc, after the pressure disappears, the spring force will press down the valve disc and close the liquid backflow. It is often used for check valves with small diameters.

2. Gravity type: Similar to the spring type, it relies on the self-gravity closure of the valve disc to prevent backflow.

3. Swing type: the liquid is straight through in the valve body, relying on the pressure to open the side of the rotary valve disc rock resistance, after the pressure is lost, the valve disc relies on its own weight to return to position, and the reverse liquid pressure closes the valve disc.

The principle of other check valves (check valves), such as the check valve for blowdown, the explosion-proof valve for civil air defense and the check valve for liquid use, is similar.

There is also the following information:

Check valve (check valve).

Check valve, also known as check valve, commonly known as single-flow valve, can be automatically opened according to the pressure difference between the front and back of the valve, and the function is to automatically control the flow direction of the liquid, so that it flows in one direction and prevents it from flowing in the opposite direction. Check valves are mostly used in water supply pipelines, and they must not be installed in reverse direction when installed.

Lift check valve. The upper part of the valve core of this valve has a guide rod, the guide rod and the valve core can be freely lifted along the guide sleeve on the valve cover, when the fluid flows from left to right, the valve core is pressed open, and when the fluid flows in the opposite direction, the valve core descends to the valve seat, and the passage is cut off.

The rocking plate check valve, also known as the swing check valve, is slightly the same as the lifting type.

The above two check valves are only installed on the horizontal line.

Spring-loaded check valve, this kind of valve is the development of the lifting type.

Ordinary lift check valves can only be installed on horizontal pipes, while spring lift check valves can be free of direction restrictions. It is used in both horizontal pipes, vertical pipes and pipes at a certain angle.

Spring-loaded check valves. These valves are available in sizes 15 mm (1 2 in) to 50 mm (2 in).

Foot valve. It is a kind of one-way valve specially installed at the inlet of the suction pipe of the water pump, commonly known as the bottom of the well, the shower head, etc.

Backflow preventer is a combination device of hydraulic control valve, which can strictly limit the one-way flow of pressurized water in the pipeline and effectively prevent backflow pollution.

According to the tap water supply equipment, especially the domestic drinking water pipeline backflow pollution is serious, and there is no effective backflow prevention device, the backflow preventer is developed to strictly limit the water in the pipeline can only flow in one direction, and its function is to prevent the medium in the pipeline from backflow under any working conditions, so as to achieve the purpose of avoiding backflow pollution.

At present, the backflow preventer is mainly divided into two categories: low-resistance backflow preventer and decompression backflow stopper, according to the national standard, the head loss of low-resistance backflow preventer is less than 3 meters, and the head loss of decompression backflow preventer is less than 7 meters. Backflow preventers can be divided into pressure-reducing backflow preventers, low-resistance backflow preventers and double-check valve backflow preventers, among which the pressure-reducing backflow preventers are suitable for all anti-backflow pollution situations, but the resistance is larger.

Notes:

1. The backflow preventer with the air balance ridge (such as the pressure-reducing backflow preventer mentioned above) may introduce external pollution, so when the fire water supply system adopts this kind of backflow preventer, it should be set up in a clean and sanitary place, and the drainage should take technical measures to prevent it from being flooded.

2. The resistance loss of the backflow preventer is large, and the impact of the resistance loss needs to be reviewed when applied.

The pressure-reducing backflow preventer is composed of two independent check valves and a hydraulically controlled drain valve, which can strictly limit the one-way flow of pressurized water in the pipeline and effectively prevent backflow pollution.

1. Before installing the backflow preventer, it is necessary to prepare and rinse the sewer pipe with clean water to rinse the stains inside the Liqi, which can effectively prevent blockage. In addition, with a low-resistance backflow preventer, the limb needs to be kept in a horizontal orientation, so that in the event of a problem, maintenance and commissioning will be much easier.

2. In the process of installing the backflow preventer, it is necessary to install and repair the butterfly valve at both ends, and install a filter at the inlet, which can effectively filter out the items that are easy to be blocked. When connecting the drain outlet and the drainage pipe, it is necessary to add a leaky bucket, so that the water limb can pass through normally and is not easy to produce stagnant water.

3. The installation location of the backflow preventer should also be selected, generally it cannot be installed outdoors or in the well of the pipeline, if necessary, it must also be approved by the relevant departments and have professional personnel for construction. If the backflow preventer is damaged, it is necessary to replace it with a backflow preventer of the same model.

The backflow preventer product consists of two separated check valves and a hydraulically driven drain valve. Due to the local head loss of the check valve, the pressure in the intermediate chamber is always lower than the pressure at the inlet. This differential pressure drives the drain valve to be closed and the pipeline to supply water normally.

When the pressure is abnormal, (i.e., the pressure at the outlet end is higher than that of the intermediate cavity), even if the two check valves cannot be sealed in reverse, the safety drain valve can automatically open to empty the backflow water and form an air partition to ensure the health and safety of the upstream water supply.

Generally speaking, this type of valve is suitable for clean water or in piping systems with physical and chemical properties similar to clean water and does not allow the medium to flow backwards. For example:

1. The intersection of the domestic drinking water pipeline and the connected pipeline for non-domestic drinking water (fire protection, production, irrigation, environmental protection, sprinkling, etc.).

2. Municipal tap water is connected to the user's water outlet near the user's water meter.

3. On the pipe when the water floods the outlet of the water supply pipe.

4. On the suction pipe on the drinking water pipeline of the pressurized pump or multi-type pressurized equipment in series.

5. In the drinking water pipeline network of various buildings and the pipelines that do not allow the backflow of medium in production.

How does a backflow preventer prevent backflow and prevent water from being contaminated? The internal structure of the valve was dismantled.

Is it an electric current or a stream of water?

The current is made with a diode.

Check valves are used for water flow.