In heating and air conditioning systems, uneven distribution of heat and cold is a common issue. Some users experience temperatures that do not meet the required standards, primarily due to hydraulic imbalance—meaning the flow of water to different users is not properly distributed. To address this, balancing valves are typically used. Traditional heating systems operate on an even heating mode, which involves constant flow with qualitative adjustments. The Jincheng heating network follows this approach, installing self-operated flow balance valves at all user entrances. However, there are several challenges in their installation and use.
For example, the self-flow balance valve and self-pressure control valve produced by Linfen Huasong Valve Co., Ltd. have specific working principles and applications. A self-operated flow balance valve works by adjusting the pressure difference between the inlet and outlet. When the actual pressure difference exceeds the set value, the valve automatically closes until the flow returns to the desired level. While effective, these valves have limitations. They require a minimum working pressure of 20kPa, and if installed in the most unfavorable circuits, it may increase the pump’s head requirement significantly. In Jincheng, improper installation locations have led to inefficiencies.
The correct installation location for a flow balance valve should be near the heat station or low-temperature boiler room. If the user is more than 80% of the heating radius away, the valve should not be installed. Additionally, the pressure head must be carefully considered. For low-rise buildings, the valve should be placed on the supply pipe, while for high-rise buildings, it should be on the return pipe to prevent vacuum issues. In large networks with significant pressure differences, flow balance valves should be installed on branches with elevation differences less than 10 meters, paired with manual balancing valves to ensure proper operation under varying conditions.
In recent years, Jincheng's heating system has adopted frequency converters for circulating pumps, allowing for variable flow based on outdoor temperature. This method, known as active variable flow, adjusts both temperature and flow. However, when the system flow decreases, the self-operated flow balance valve at the near-end tries to maintain flow, leading to shortages at the far end. This results in poor overall performance. Manual balancing valves are needed to adjust the flow and achieve hydraulic balance.
As heating systems evolve, future models will rely on user-initiated variable flow, where heat demand changes dynamically. In such cases, self-flow balance valves may only act as flow limiters, unable to adapt to real-time changes. Instead, self-operated pressure control valves offer a better solution.
Self-operated pressure control valves function by maintaining a constant differential pressure within the controlled loop. When network pressure fluctuates or resistance changes, the valve adjusts accordingly, ensuring stable pressure. These valves can be installed on either the supply or return line, depending on the system’s needs. There are three main installation methods: at the building entrance, at each unit entrance, or at each floor. Each has its own cost and effectiveness considerations.
These valves isolate the effects of flow changes between users, stabilize system operations, and help manage pressure fluctuations caused by traffic changes. They also support user-initiated variable flow, making them ideal for modern heating systems with metering and individual control.
In conclusion, during the reform of metered charging, it is recommended to use self-charging pressure controllers in hot user systems to avoid complications from replacing heat meters later. This ensures a more efficient and adaptable heating solution for the future.
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