[Abstract] This paper introduces the characteristics of the balance valve and the problems that need attention in air-conditioning water system. Compared with other control valves, the balance valve has more complete functions and good regulation performance. Key words: balance valve; water system; flow rate; pressure resistance I. INTRODUCTION Current central air conditioning Most of the water system for two control, both winter and summer. In order to balance the resistance of the water system, designers generally use the same type of water system as much as possible. However, due to some limitations in actual projects, designers also design some different types of water systems. In addition, although the system loops use the same type of water system, there are also serious resistance imbalances between the system loops. In order to improve the conditioning function of air conditioning water system, with good performance control valve to take belt is still widely used gate valve, globe valve, butterfly valve and other current balance valve because of its more complete functions and good regulation performance, is more and more affected Emphasis and welcome. Second, the balance valve characteristics Compared with other valves, the balance valve has the following characteristics: (1) linear flow characteristics, that is, the pressure difference in the valve before and after the case, the flow and opening generally linear relationship; (2 ) Has an accurate opening instructions; (3) there is a degree of opening locking device, non-managers can not easily change the opening; (4) the valve body has two pressure-measuring holes, connected with a smart meter hose, To show the valve before and after the pressure drop and flow through the valve. Although balancing valve has many advantages, but its application in air conditioning water system there are still many problems. If these problems are not solved well, the characteristics of the balance valve can not be fully revealed. Third, the application of air conditioning water system should pay attention to the problem 1. Selection problems Some designers in the selection of balance valve, for the convenience of the map, often according to the pipe diameter directly determine the nominal diameter of the valve ("Practical Heating and Air Conditioning Design Manual," a book is also required), in fact, this is not the best choice. Balance valve and gate valve, globe valve, butterfly valve is different, in order to ensure the regulation accuracy, to ensure and give full play to its regulatory role, should make the choice of balancing valve in the design flow and pressure to meet the circumstances, the opening control in 60% to 90 %, So that both to meet the design flow requirements, but also a certain amount of adjustment margin. Therefore, the nominal diameter of the selected counterbalance valve is not necessarily equal to the pipe diameter. 2. Design and construction instructions Problem In the actual engineering design, few designers to balance the valve to consume the pressure and flow through the balance valve in the design and construction instructions given, which brings difficulties to the system adjustment, but also to The advantages of the balance valve have not been played. If the construction instructions given with a balance valve-related parameters, so that you can adjust the entire system to provide favorable conditions. In addition, the design of opening, measured the actual flow is not necessarily equal to the design flow, according to the actual measured flow, and then open a large or small balance valve, the implementation of fine-tuning, has been to achieve satisfactory design flow value. 3. The partition air conditioning water system main pipe installation balance valve should pay attention to the problem Several air conditioning water system is often divided into several cells according to the characteristics of air conditioning load, each area consists of a water system loop. Although the water system loops in each subdivision may use the same system, there is still a problem of resistance imbalance between the loops, which necessitates the installation of counterbalance valves on the tubes connected to the headers of the sumps, The actual measured backwater temperature regulates the water flow in each loop, allowing each loop to operate at the designed flow rate. Of course, the balance valve can also be installed in the manifold on the water supply pipe, the precondition is that the balance valve pressure capacity to meet the design requirements. Due to the different load characteristics in winter and summer, the temperature of return water is different, the flow rate of each district water system changes in winter and summer, and the water systems of each district have to be rebalanced. Therefore, when choosing the main balance valve of each district water system To fully consider the situation in both winter and summer, to determine a balance valve of the best nominal diameter, in order to ensure the balance of winter and summer balance valve adjustment accuracy. 4. Balance valve installation problem To make the water flow before and after the flow balance valve stability, to ensure measurement accuracy, the balance valve should be installed in the straight pipe section, that is, before and after the balance valve should be 5 times and 2 times the diameter of the straight pipe section. If the balance valve is located in the El pipe section of the pump, the valve is required before the 10-diameter straight pipe length. Construction workers in the handling and installation of balancing valve, we should pay attention to gently, to prevent the valve or manometry d:: fL was hit bad. The construction technician must remind the construction staff to pay attention to the installation position and installation direction of the balance valve, and adjust the balance valve handle and manometric d,: fL in a convenient position for operation. After the entire air-conditioning water system commissioning is completed, must be balanced valve insulation. Balance valve to be adjusted, the normal operation of the pipe network system, do not change the balance valve opening, in particular, do not change the positioning locking device. When repairing a loop, the balance valve of the loop can be closed to zero. Repair open to the original lock position. After each adjustment positioning, the balance valve should be well insulated. The balance valve to repair the balance of the pipeline system, will be more efficient, intuitive and accurate, so that the entire system at the best operating conditions, reduce energy waste and reduce operating costs. Therefore, the installation of balancing valve has its energy-saving. 5. Pressure problems Air conditioning water system balance valve nominal pressure is generally 16kg / cm2. Strength test pressure is generally 1.5 times the nominal pressure, that is, the test pressure of 24kg / cm2: tightness test test pressure should be nominal pressure, that is, 16kg / cm2. three. Conclusion Only efforts to improve the quality of balance valve to reduce low, and through reasonable design and selection, the correct installation and commissioning, in order to ensure that the actual flow and design flow in each loop is consistent, the entire air-conditioning system in the best conditions Run, reduce energy consumption, reduce operating costs and improve the reliability of the water system throughout the air conditioning.
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