Development history
Negative pressure-free water supply equipment is a type of pressurized water supply unit that is directly connected to the municipal water supply network. It uses the residual pressure of the municipal network to provide superimposed pressure and ensure that the pressure of the municipal network is not less than the set protection pressure (the set pressure must be higher than the pressure requirement of the direct supply area of the community, generally not less than 1.2 kg).
The core of pipeline booster (negative pressure-free) water supply equipment is how to prevent negative pressure from being generated during the operation of the secondary booster water supply system, eliminate the impact of unit operation on the municipal pipeline network, and achieve safe, reliable, stable water supply without affecting the water use of nearby users.
Negative pressure-free water supply equipment is also known as pipeline superimposed pressure water supply equipment. Currently, the main types on the market are tank-type negative pressure-free water supply equipment and box-type negative pressure-free water supply equipment.
The technology of booster pumping originated in Japan. Research on this technology began in Japan in the mid-1980s, encompassing not only technical aspects but also discussions on market demand, administrative management, law, and water supply models for high-rise buildings in cities. Direct water supply systems were included in the national policy document "Long-Term Goals for the Transformation and Reconstruction of Water Supply Systems Towards the 21st Century" by the Japanese Ministry of Health, Labour and Welfare, which revised water supply design standards accordingly, raising the service water pressure at the end of the water supply network from 0.15 MPa to 0.2 MPa. With national funding, a sizable laboratory was established in Chiba Prefecture, and a team comprised of researchers from research institutions, water supply companies, scholars, and product manufacturers was assembled. After securing funding, research on "direct water supply" was conducted, with a three-year plan to complete the research on "promoting direct water supply systems," resulting in numerous related research projects. In 1992, the Sapporo City Waterworks Bureau in Japan implemented a new secondary water supply plan. In that year alone, 68 buildings adopted booster pump systems, eliminating their original water tanks, and the results were highly praised. The American professional water company, DAREYET Water Group, has been dedicated to the development and research of new secondary water supply technologies, successfully promoting the use of booster pump systems in the United States and around the world. By the late 1990s, booster pump technology was widely used in Japan, the United States, Western Europe, and other countries.
Equipment Composition
The complete set of equipment consists of a flow stabilizing tank, a vacuum suppressor, a variable frequency speed control water pump unit, a pressure sensor, a variable frequency control cabinet, a backflow preventer (optional), a disinfection device (optional), and a small flow pressure holding tank (optional). The inlet pipe from the municipal water supply network is directly connected to the inlet of the flow stabilizing tank. The outlet of the flow stabilizing tank, after passing through the disinfection device, is connected to the inlet pipe of the booster pump unit. The outlet pipe of the booster unit is connected to the user's water pipe, directly supplying water to the user's water supply network.
Working principle
The steady-flow tank-type negative pressure-free water supply equipment is directly connected to the municipal pipe network and provides water supply by series superposition based on the remaining pressure of the municipal pipe network.
(1) Variable frequency constant pressure water supply: When the water supply of the municipal pipeline is greater than the water consumption of the user, the constant pressure water supply equipment of the steady flow tank type variable frequency constant pressure water supply is used. At this time, a certain amount of pressurized water is stored in the steady flow tank.
(2) Eliminating Negative Pressure: When the user's water consumption increases, causing a pressure drop at the connection between the municipal water supply network and the stabilizing tank, a negative pressure is formed in the stabilizing tank when the pressure drops below the relative pressure of 0. The air inlet valve of the vacuum suppressor opens, allowing atmospheric air to enter the stabilizing tank. At this time, the stabilizing tank is equivalent to an open water tank with a free surface, and the pressure is the same as atmospheric pressure, thus eliminating the negative pressure. When the water level drops to the set value, the level controller transmits a control signal to the control system in the frequency converter control cabinet, controlling the booster unit to stop working, and the user's water supply is cut off. When the user's water consumption decreases, the water level in the stabilizing tank rises, gas is discharged from the vacuum suppressor's exhaust valve, and after the pressure returns to normal, the booster unit automatically restarts, restoring water supply.
(3) Water outage shutdown function: When the municipal water supply is interrupted, the booster unit will automatically stop running under the control of the liquid level controller. After the municipal water supply is restored, it will automatically start to restore normal water supply.
(4) Low flow sleep function: When the user does not use water or the water consumption is very low, the equipment will automatically enter the sleep state (stop) and maintain the water supply pressure. When the user resumes water use, the system will automatically wake up and restore normal water supply.
(5) Continued water supply during power outages: When the community experiences a power outage, the municipal water supply network continues to supply water to users in the lower zones, ensuring uninterrupted water supply during power outages. Once power is restored, the equipment will automatically start and resume normal water supply.
Equipment Classification
Currently, there are two main types of negative pressure water supply equipment on the market: flow stabilizing tank type and regulating water tank type.
Folded Flow Stabilizer Tank
Tank-type negative pressure-free water supply equipment installs a pressure-sealed tank before the water pump. A flow stabilizer (also known as a "vacuum eliminator") is added inside or outside the tank. The water pump draws water through the flow stabilizer tank, pressurizes it, and supplies it to users. The flow stabilizer's regulating effect reduces the impact on the public water supply network. This method has no water storage capacity, and water outages are likely to occur when the city's public water supply network is shut down.
Foldable adjustable water tank type
This method features a non-pressurized regulating water tank with an internal flow stabilizer. An electronic control system ensures the water in the tank circulates at least twice daily, maintaining consistent water quality. When the municipal water supply and pressure meet the requirements for pressure-free water supply, water is drawn directly from the municipal network; otherwise, water is drawn from the regulating tank. This method provides a certain reserve of water and can be used in areas with unstable water supply networks. However, due to the presence of the water tank and manhole, regular cleaning and disinfection are still required as stipulated.
Equipment advantages
1. It saves on equipment investment costs and requires a relatively small footprint. Not only does it save on investment, but it also makes full use of the primary water supply pressure in the municipal water supply network. This can be achieved by appropriately reducing the size of the booster pump, thus saving on equipment costs. Secondly, it saves on the system's footprint, making full use of the saved land and further increasing the building's usable floor space, thus meeting my country's requirements for land resource conservation.
2. Clean and pollution-free: The water supply system is a fully sealed structure, from the tap water supply network to the user's faucet. Therefore, contaminants will not enter the water supply system. The water is not in direct contact with the air, and food-grade stainless steel is used to make the flow parts, so there will be no water pollution.
3. Significant energy-saving effect: The equipment is typically connected in series with the municipal water supply network. This means that the required pressure is added to the water supply network pressure at the water treatment plant, and if the pressure is insufficient, it is increased appropriately, thus making full use of the network's residual pressure. During off-peak water usage periods, the equipment can be shut down, resulting in noticeable energy savings.
4. Simple installation. Since the negative pressure boosting water supply equipment is a complete supply system, users only need to connect the inlet and outlet water pipes to use it. The construction period is short and the installation is convenient.
5. Lower operating costs. Because the selection of booster pumps involves relatively few components, and a system of pump-based water supply can be used, the city's primary water supply pressure can be utilized during off-peak water usage periods. This allows for the fulfillment of urban water needs by either not starting any pumps or starting only one pump. Other pumps are only activated during peak water usage periods. Therefore, the equipment operates with lower energy consumption, effectively reducing operating costs.
6. Power outages will not affect the water supply. Because the equipment's public water supply network is directly connected to the user's network, although the booster pump stops operating during a power outage, the primary water supply pressure from the waterworks can still meet the water demand.
7. Facilitates Post-Management. Because the negative pressure boosting water supply equipment is a fully automatic microcomputer-controlled system, it automatically shuts down during power outages and automatically restarts upon power restoration. It also boasts comprehensive fault detection, technical diagnosis, and alarm alerts, making equipment management and maintenance relatively simple. Furthermore, since it is not susceptible to contamination, there is no need for cleaning.
