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Balance valve works in the flow regulation
Balance valve points manual balance valve and self-balancing valve. Both manual balancing valve or self-balancing valve, their role is to increase the proximal end of the heating system to increase resistance, limiting the actual operating flow should not exceed the design flow; in other words, its role is to overcome the redundant heating system proximal With ram, the electric control valve or thermostatic valve can work under a permitted pressure head. Therefore, the manual balancing valve and self-balancing valve, they are all thermostatic valve or electric control valve auxiliary flow regulator, but it is very important, if the selection is not properly designed or unreasonable, electric control valve or temperature control Valves do not work well. 1, manual balance valve 1.1 Manual balance valve works Manual balance valve is a one-time manual adjustment, can not automatically change with the system operating conditions change the drag coefficient, so called static balance valve. The object of manual balancing valve is resistance, can play the role of manually adjustable orifice to balance the resistance of the pipe network system, to achieve the balance of resistance of each loop role. Can solve the system steady-state imbalance problem: when the operating conditions are different from the design conditions, the circulating water is more or less than the design conditions, the balance valve is balanced by the system resistance, the new water volume can be designed according to the proportion of balance The flow of each branch will be increased or decreased in proportion at the same time and still meet the flow requirements corresponding to the current load 1.2 Problems to be noticed in the design and selection of manual balancing valve (2) (1) The characteristic curve of the valve is decided The valve regulating performance, such as the closing valve flow curve, if 95% ~ 100% of the traffic flow that is meaningless, then the opening from 0 to 5% of the flow that is achieved throughout the change, so the valve is It can not be used as a balance of water conservancy conditions. As the theoretical curve of the valve is measured under the top pressure difference, and the actual conditions as long as the valve authority is not 1, the valve in the small opening line valve before and after the pressure difference, the opening is the valve before and after the pressure difference, resulting in valve dG / dC value in the small opening becomes larger, smaller opening in the large opening, so that the actual work of the valve to open the direction of the deviation, the smaller the valve power the greater the deviation, the linear characteristics of the valve due to the actual performance Offset will lead to effective adjustment of the valve opening degree of space becomes smaller, so the theoretical curve of the valve string below the arc as a percentage of the characteristics as well. Equal percentage curve valve, the valve authority of 0.3 ~ 0.5 actual working curve may be close to the linear characteristics. (2) Normally, the flow rate of the valve is too high when the valve is small, and the turbulent swirling zone will be formed after the valve. The vortex zone and the new pressure are very low, where the pressure is lower than the saturated pressure corresponding to the water temperature The flash of water vapor leads to the phenomenon of steam blow: severe noise, vibration of valves and pipes, damage of valves, pipes and pipe supports. Prevention and control of such accidents First of all, in the design of the valve runner to consider the valve seat and valve seat in the small opening to form a narrow throttle passage, constrained the formation of strong turbulent vortex; followed by the valve to maximize the valve Degrees, to avoid the valve in the small opening of the operation. In addition, as far as possible without pressure conditions involved in the problem of alkaline balance valve installed in the water back to the lower water pipes. 2, self-balancing valve 2.1 self-balancing valve works Self-balancing valve can be in the absence of external power supply, the system automatically balances traffic. Self-balancing valve is to maintain the orifice (fixed aperture) before and after the differential pressure to achieve a limited flow, therefore, can also be called the flow valve. Fixed flow valve is the role of object flow, to lock the flow of water through the valve, rather than against the balance of resistance. He can solve the system's dynamic imbalance: In order to maintain the efficient operation of a single chiller, boiler, cooling tower, heat exchanger these devices need to control the flow of these devices is fixed at the rated value; From the end of the system, in order to avoid Dynamic adjustment of the interaction, but also need to end the flow of devices or branches. The problem should be noted in the design Self-flow flow control valve has the drawback of the valve is the minimum work poor requirements, the general requirements of the product minimum working pressure 20KPa, if installed in the most adverse circuit, will inevitably require more circulating water pump 2 m water column The work lift, it should be taken near-end installation, distal uneasy method. Do not install this self-operated flow control valve when the user is at a distance greater than 80% of the heating radius from the heat source.