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First, the balance valve Balance valve correctly understood should be balanced hydraulic conditions valve. From this concept all the valves used for the balance of hydraulic conditions, such as regulating valves, pressure reducing valves, self-operated flow control valves, self-operated pressure differential control valves should be regarded as hydraulic balance valve - balance valve. The products on the market called counterbalance valves are just a kind of manual control valve with the function of flow test. Static balance valve refers to manual control valve or manual balancing valve. Dynamic balance valve is self-flow control valve and self-pressure control valve. Self-acting flow control valve has also been called self-flow controller, self-balancing valve. Self-operated differential pressure control valve is also called Automotic Balamce Valve in Northern Europe. Second, the hydraulic conditions and the balance of hydraulic conditions Generally speaking, heating, air conditioning pipe network are closed-loop pipe network, the hydraulic conditions refers to the system pressure at all points, the various sections of the flow, pressure. From the formula â–³ P = SG2 â–³ P - pressure drop or loss of resistance S - pipe or system resistance coefficient G - pipe or system flow shows, flow and pressure are related parameters, flow and pressure control each other means And purpose. Decompression means is to reduce the flow of the upstream pipe; reduce the flow will inevitably reduce the pressure on the point before the pipeline or increase the pressure at the point after the pipeline. Flow changes will inevitably lead to pressure changes; S value unchanged system, pressure changes must be due to changes in flow. So there is not a flow control valve that does not affect pressure, nor a pressure control valve that does not affect flow. Hydraulic conditions balance refers to the rational distribution of the flow. In heating and air conditioning pipe network, water is a heat carrier medium, the rational distribution of water flow is the basis for the balance of thermal conditions. Taking the heating system as an example, the designer carries out the hypothetical situation when the branch flow is the design value during the calculation of hydraulic conditions. Due to the limitation of tubing and maximum flow rate, it is almost impossible to achieve hydraulic balance in design. This will inevitably cause the proximal resistance coefficient can not reach the ideal state of the design, the formation of the proximal flow is too large, the lack of remote flow disorders. Because of hydraulic design into a design hydraulic map, and the actual operation of the hydraulic map must be balanced by the valve to form. The process of regulating the hydraulic conditions with a valve is a process of establishing a reasonable hydraulic pressure chart. The two hydraulic pressure plans will work well when the design is reasonable. Due to the operation of hydraulic conditions is the working curve of the pump and the characteristics of the formation of the outer network formed. For the external network characteristic curve â–³ P = SG2, the S value of the near-end branch in parallel will be less than the designed value, resulting in the total S value far less than the designed value. The circulating pump operates under the condition of small lift and large flow, Power, low efficiency point of operation. Serious shaft power may appear greater than the motor nameplate power, the motor over-rated current, until the burning motor accident. Network transfer process is to increase the proximal balance valve resistance, so that the value of the proximal branch S increased to the design value, the total S value increased to the design value. So that far and near the flow distribution is reasonable and reasonable, circulating pump running in the design conditions, to heat, power saving, improve the quality of heating purposes. Workers often have some misunderstanding of some imbalances in hydraulic conditions: (1) the pump output is insufficient, the actual pump head is less than the nameplate lift, leading to the end of the speech too much water. In fact, the resistance of the near-end feeder is small and the flow rate is large, resulting in a small flow at the far end. The working point of the pump is shifted to a large flow rate, a small lift and an inefficient operating point. (2) Boiler or heat exchanger resistance, all boiler or heat exchanger manufacturers are far less than the nominal resistance of the resistance. In fact, the increase of the total circulating water will inevitably lead to speech boiler heat exchanger and other resistance increases. Water flow increased by 40%, resistance increased by 100%. (3) lack of boiler output, in fact, the flow rate increases after the supply and return water temperature difference can not be greater. Of course, abnormal coal quality and wind system may also contribute to the issue of boiler output.
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