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In heating and air conditioning systems often appear uneven heat and cold, some users room temperature is not standard, mainly due to imbalance in hydraulic conditions, that is, all hot users of the water flow distribution is unreasonable, to solve this problem only by balancing valve to complete. Heating system in the traditional heating system is an evenly distributed heating mode, this heating mode generally take a qualitative adjustment of the constant flow. Jincheng heat network is taken by this heating mode, under the guidance of this mode of heating, all thermal systems in all entrances of the user to install a self-operated flow balance valve, but there are some problems in the installation and use. To Linfen Huasong Valve Co., Ltd. production of self-flow balance valve and self-pressure control valve, for example, a brief description of its principles and applications. A self-operated flow balance valve 1.1 Working principle When the media into the main valve, the inlet pressure P1, manual throttle before and after the pressure was P2 and P3, when the throttle opens to a certain position, that is man-made to determine the " (P2-P3), the actual value of (P2-P3) exceeds the allowable given value. At this time, the main valve and valve plug automatically close the valve Until the flow rate is again maintained at the set flow rate and vice versa. 1.2 Shortcomings General requirements for the minimum working pressure is 20kPa. If installed in the most adverse circuit, will inevitably require more circulating pump circulation 2m water Zhu working lift. Jincheng populace will be installed self-flow balancing valve approach is wrong, it should take away from the heat station (or direct supply of low-temperature boiler room) near the floor installation, if the user away from the heat station distance greater than the heating radius of 80 % Should not be installed when the flow of self-balancing valve. 1.3 Installation location Heat network near the end of the flow is too large, the distal flow is too small, the proximal end of the pressure head pressure is greater than the user need to pressure head, the valve must be surplus pressure head, that is, the pressure head = excess pressure head pressure head - Need to use pressure head. Figure 1 (a) shows the installation position and pressure points of the hot user balanced valve. If the user supplies water to the balance valve, P3 is approximately equal to P4. The P2 pressure line is shown in Figure 1 (b) and is almost parallel to P4. If the user installs counterbalance valve wicket, then P2 is approximately equal to P1, P3 pressure line is almost parallel to P1. The actual indoor water pressure P2, return pressure P3, if the pressure is too low will empty, over pressure will lead to over-pressure cast iron steam. Therefore, Jincheng balance valve installed in the return pipe approach is wrong. The correct approach is: the relatively low-lying buildings can be installed in the water supply pipe, pressure head to ensure that the indoor does not exceed the standard, in the relatively high-rise buildings can be installed in the return pipe to ensure that the indoor does not empty. In a large heating radius, the external network for a large pressure difference between supply and return should be installed in the home water supply flow balance valve installed in the terrain elevation difference of not more than 10m branch back to install a manual balance pipe valve. Here self-flow balancing valve is responsible for controlling the distribution of flow, manual balancing valve to adjust the pressure so that the valve pressure reaches 0.25MPa full water operating conditions. 1.4 heating operation In recent years, Jincheng heat network circulating pump is generally equipped with a frequency converter, the temperature changes, the quality and transfer both temperature and flow simultaneously adjusted. The use of a single parameter of the outdoor temperature control heat cycle pump speed, to achieve variable flow mode of operation known as active heat variable flow. In this case, when the system flow becomes smaller, the near-end user loop self-operated flow balance valve action, to maintain the same traffic, and remote user loop traffic will be a serious shortage, which is the reason Jincheng heating network is not good . In the heat source variable flow in this case, self-balancing valve can not guarantee the balance of hydraulic conditions. If the total heat network into 75% of the original flow, requiring all hot user traffic has become the original 75%, self-balancing valve can not complete this task, only by manual balancing valve to adjust the amount of withered system flow, Achieve balance of hydraulic conditions. However, with the deepening of heating system reform and the promotion of household-based control of household heat metering, the future model is that the caloric needs of users will change at any time. The heat load and circulation flow depend on the needs of users and may also be referred to as user initiative Variable flow. In this mode, the hot user traffic changes at any time, when the user system temperature control valve is closed, the user system traffic becomes smaller, in order to maintain the original flow unchanged, self-flow balancing valve will open the valve until all open until. When the user system temperature control valve open, the user system becomes larger, in order to maintain the same constant flow, self-flow valve will close the balance valve, has been completely shut down. Only self-flow flow balance valve failure, the user's flow requirements can be achieved, self-flow flow balance valve is only a flow-limiting valve here, only play the role of the maximum flow limit. 2 Self-acting pressure control valve to replace the self-flow balance valve Self-operated pressure control valve and self-flow balancing valve belong to the same variable flow - constant flow device, the difference is that the flow control valve of the variable flow device in the valve body , And self-operated pressure control valve variable flow device in the valve "user". 2.1 Self-operated pressure control valve works When the network when the water pressure P1 increases, the controlled circuit water pressure P2 instantaneous increase, along with pressure-sensitive membrane force balance is broken, the valve flap to move the direction of closure , The resistance of the valve increases, and P2 returns to its original size, that is, P2-P3 remains unchanged and vice versa. When the back pressure P3 of the network increases, the force balance of the pressure sensitive film is broken, the valve flap moves to the shoulder, the resistance of the valve decreases, P2 increases, P2-P3 restores unchanged, and vice versa Also. When the resistance inside the controlled loop changes, such as a branch off, the total loop resistance increases, at this moment P2 increases, P2-P3 increases, along with the pressure sensitive membrane force balance Breaking, the valve flap to close the direction of movement, the valve resistance increases, P2 has returned to its original size, that P2-P3 unchanged, we can see, whether it is fluctuations in network pressure, or resistance within the controlled loop changes , Can ensure that the controlled loop pressure is constant. 2.2 The characteristics of self-operated pressure control valve Self-operated pressure control valve is divided into two types of constant pressure recommended and adjustable pressure can be used to make the valve before the pressure regulator, the valve pressure regulator and differential pressure regulator. â–³ P = SG2 P for the return water pressure difference, S is the indoor resistance coefficient, G is the indoor design flow. By controlling the indoor backwater pressure differential flow control, flow control in this way, we must rely on portable flow tester to determine, the advantage is for the remote user does not increase the consumption of pressure head. 2.3 Installation Position Self-operated pressure control valve for user-system differential pressure adjustment, can be installed on the water supply can also be installed on the backwater. Two installation of differential pressure valve structure is different, not interchangeable, but can be directly in front of the electric valve control electric valve pressure before and after. There are three methods of installation: first, on the total entrance of each building; second, on each entrance to each building, entrance to each unit of the residential building; and third, Or the entrance to each floor. The third method is the highest cost, the first method is the lowest cost, the first method is generally considered more appropriate. 2.4 The role of self-operated pressure control valve After the installation of self-operated pressure control valve, self-pressure control valve consumption surplus head of the system can isolate the interaction between flow changes of users interfere with each other, the controlled system can be under water pressure, Automatically eliminate excess pressure head pipe network and pressure fluctuations caused by traffic changes, help to stabilize the system operating conditions. Self-operated differential pressure control valve can solve the problem of pressure difference caused by the direct connection of buildings and terrain. When the heating system is initially started and cold, the heat demand of the user may exceed the heating capacity of the system. The self-operated differential pressure controller can limit the effect of near-end user heating for remote users. These performances support "user" Active variable flow. Self-operated differential pressure control valve can be used in conjunction with the thermostatic valve to meet the variable flow of household metering heating. 3 Conclusion To sum up, in the metrological charging reform, the hot user system should be used to measure self-charging pressure controller, to avoid the replacement of heat meters after the replacement valve.