Abstract: Based on the working principle of hydraulic control valve, the paper analyzes the factors that affect the stable operation of hydraulic control valve from the structure, installation and operating environment of the hydraulic valve, and proposes an improved solution to improve the stable operation of hydraulic control valve. Keywords: hydraulic level control valve working principle of stable operation to improve the program 1, Introduction Hydraulic level control valve is an improved float valve, when the pool or water tower water level drops, the float valve opens drainage, the water pressure in the water pipe will be When the water level rises to the control surface, the float valve is closed and the piston moves downward to close the sealing surface. The valve stops water supply to achieve the purpose of automatically controlling the water level. Because of its power consumption, simple structure, easy installation and construction, the application of pressure and Other advantages, in all types of clear water tank (water tank) automatic control of water has a more extensive application. However, due to the influence of water quality and hydraulic factors, the hydraulic level control valve often fails, ranging from waste of water resources, heavy water pumping station, causing serious consequences. Improve the stability of hydraulic control valve, it is very important to ensure safe water supply. 2, the internal structure of the hydraulic water level control valve and the principle of action Hydraulic water level control valve is generally composed of float valve, control tube, hydraulic valve body. Although the appearance of hydraulic control valve body vary, different materials, vertical and horizontal installation forms, but its internal structure and role of the principle is basically the same. The main body of the hydraulic control valve is composed of inlet chamber, water outlet, piston-type valve core, pressure relief cavity and relief port. Set the water pressure P0, pressure relief chamber pressure P1; piston-type valve gravity G, piston-type spool pressure relief chamber end diameter D1, the other end of the diameter D2. The diameter of the orifice connected to the inlet chamber and the pressure relief chamber is d1, and the diameter of the relief port is d2. The friction between the piston-type valve spool and the valve chamber is f, and the supportive force is N. The following is a schematic diagram of the structure of Figure 1 (a second similar structure), for example, the analysis of the piston-type valve force is as follows: Suppose the resultant force of the piston-type valve spool is F, then the force vector formula: F = F1 + F2 + F3 + F4 + f + N + G (1) Expression as algebraic form is as follows: F = P0D22π / 4 + P2 (D12π / 4 - D22π / 4) - P1D12π / 4 ± f-G ± N = (P0D22-P1D12) π / 4 ± f-G + P2 (D12-D22) π / 4 ± N = A ± f-G ± N + B where A = (P0D22-P1D12) π / 4, B = P2 (D12-D22) π / 4; The sign of f is opposite to that of A. When the water level in the pool or water tower drops, when the float valve opens drainage, the water inlet cavity replenishes water through the small hole d1 to the pressure relief cavity. Because the water supply hole d1 <pressure relief hole d2, the water replenishment capacity is less than the pressure relief capacity, the pressure P1 Reduce the spool support force N1 gradually reduced to disappear, there is pressure water into the water pipe P0 overcomes the gravity and friction of the piston-type valve spool to lift it, the above formula F> 0, the sealing surface gradually opened, the hydraulic valve that is open Water to the pool (or water tower). When the pool water level rises to control the surface of water, the float valve is closed and the pressure relief chamber is filled with water more than the pressure relief capacity. N2 gradually decreases and P1 rises (up to P0). The above formula F <0, That is, stop the water supply. Hydraulic control valve under the control of the float, which can automatically control the water level. 3, the factors that affect the stable operation of the hydraulic pressure level control valve 3.2 pressure relief chamber pressure changes When the hydraulic control valve is installed and put into use, (2) where D1, D2, d1, d2G are known constants, affecting the piston-type spool movement force Only the pressure of water P0, the role of P1 and the friction suffered by the piston f. Under normal circumstances: D1≥D2, d1≤d2, the outlet pressure changes within the range of 0≤P2 <P0, discharge pressure 0 <C1 (constant) ≤ P1≤C2 ~ P0. Through the analysis of force, we can see that the safe and reliable operation of the hydraulic valve requires that the pressure in the relief chamber should be properly changed. When the pressure in the relief chamber reaches the minimum, the spool can rise to the maximum opening position. If the piston of the hydraulic control valve The valve spool is strong and can always keep the pressure relief chamber closed and can be tightly combined with the inlet of the water inlet. When the float valve is closed, the pressure in the pressure relief chamber can always rise to C2 (C2 is equal to P0, The method has nothing to do), the piston-type spool in the water pressure P1 and its own gravity G, to overcome the friction f drop and close the hydraulic valve. Visible pressure relief chamber minimum pressure C1 is to determine whether the hydraulic valve can be a key factor in stable operation, pressure relief valve cavity pressure changes in the speed of the decision of the level of sensitivity of the valve. Define the minimum pressure in the pressure relief chamber C1 is the number of stable operation of the hydraulic control valve. When the maximum hydraulic control valve opening, the float valve is stable when the water, the pressure relief chamber pressure P1 = C1. At this point through the replenishment hole, drainage cavity, float valve outlet cross-section of the flow equal; connected to the inlet chamber and the pressure relief chamber channel inlet, pressure relief chamber and float valve outlet (control line) The equation can be C1 influencing factors (cross-sectional position shown in Figure 3 vertical hydraulic control valve installation diagram shown), the following formula holds: ω pass v pass = ω vent ν vent = ω ball ν ball d12 v pass = D12 v Leakage = d ball 2ν ball (3) Z into + P0 / γ + α1ν through 2 / 2g = Z vent + P1 / γ + α2ν vent 2 / 2g + h loss 1 = Z ball + P ball / γ + α3ν ball 2 / 2g + h loss of 2 ........................ (4) finishing the above formula, derived: P1 = C1 = γ (Z ball - Z vent) + P ball / γ + (α3ν ball 2-α2ν vent 2) / 2g + h loss 2-h loss 1)) = γ (Z ball -Z vent) + P0 / γ + (α3 ball 2-α2 v vent 2) / 2g-h loss 3) And subscript: the area corresponding to the cross section ν and subscript: the liquid flow rate corresponding to the cross section Z and subscript: the geometric elevation P and subscript of the cross section corresponding to the water flow Said the flow pressure γ: liquid specific gravity α and subscript: Corresponding kinetic energy dressing coefficient h and subscript: Along the way and local head loss and g: Gravitational acceleration 3.3 Factors that affect the stable operation of the hydraulic control valve 3.3.1 Hydraulic valve structure of their own Hydraulic Valve to reliable operation, requiring piston-type spool solid, flexible lifting, can always keep the pressure relief chamber closed and can be sealed into the water chamber as needed; According to the hydraulic knowledge, it can be seen from (5) that the smaller the pore passage d1 connecting to the pressure relief chamber, the larger the head loss h loss 3, the lower the C1 value. Appropriate to reduce the pore diameter d1 can help reduce the value of C1, float valve opens, the valve core can quickly rise, open the hydraulic valve. When the float valve is closed, the hydraulic pressure valve performance can be improved by reducing (and preventing) the hydraulic valve from closing the valve due to the weakened water replenishment capacity and the slow pressure rise in the pressure relief chamber. However, the small hole diameter d1 channel is too small, easily lead to blocked the hole, resulting in hydraulic valve switch is not working. In addition, increasing the diameter of piston-type valve relief port chamber, help to reduce pressure relief valve closing the role of the pressure chamber; but will increase the pressure on the valve opening P0 requirements. 3.3.2 Hydraulic Valve Installation Hydraulic valve installation, should be the appropriate choice of control pipe diameter and length. Control of pipe diameter increases, the water flow rate will be reduced through the loss of hydraulic control h loss 4, C1 value will be reduced, is conducive to the operation of the hydraulic valve. The diameter of the control tube is generally between dn15 ~ dn40. If the diameter of the control tube is too large, the matching float valve will increase. On the one hand, the float will reduce the water storage space of the water tank and reduce the utilization rate of the water tank. On the other hand, As for the float closing time, pressure relief chamber boost time longer, the hydraulic valve will be delayed off, you need to have a larger pool of effective space in order not to waste water resources. Control of the length of the tube should also be limited to increase the length of the control tube, h loss 4 increases, C1 value increases, pressure relief chamber pressure increased longer, the hydraulic valve will delay closure, adverse and hydraulic valve stable operation. 3.3.3 water pressure and water flow state Hydraulic valve at work, the force caused by the water pressure P0, the lower the water pressure, lift the valve required pressure relief chamber P1 is also low, that is, C1 value is small, not Hydraulic valve is conducive to work. When P0 is low, pressure relief chamber pressure relief, the piston-type valve by the upward pressure can not overcome its own gravity and friction, the hydraulic valve will not open. Due to the material of the valve body parts, P0 can not be too high. High pressure so that the force exerted by the valve core N1N2 increases, the wear and tear on the valve ring seal, affecting the life of the hydraulic valve. Therefore, the hydraulic valve must work in the nominal pressure range. Due to the change of water flow direction, all components in the valve body are subject to the intense flushing and impact of the water flow. Measures must be taken to ensure the structural stability of the valve plug. The components of the valve plug (sealing ring, guide pin, locking bolt, etc.) . 3.3.4 Water Quality Operating Requirements The medium is clean water. The design and installation of the hydraulic valve can ensure that the hydraulic valve does not contain solid particles in the water and does not block the internal size of the valve body, and does not corrode the internal structure of the hydraulic valve. However, the dissolved solids in the water habitat, in the hydraulic valve body and the control pipe fouling, thereby affecting the body of the pressure relief chamber sealing, increasing the spool friction f, spool movement increases the force at the same time Control section of the pipe to reduce the discharge section, the pressure relief chamber drainage capacity decreases, the loss of control head h loss increases 4, C1 value increases, when the C1 value increases to a certain extent, the piston-type spool can not be flexible Exercise, so that the hydraulic valve failure. For high hardness, more soluble solid medium, the need to appropriately increase the diameter of the control tube and strengthen the operation and maintenance of the hydraulic control valve. 4, to improve the steady operation of the hydraulic pressure level control valve program 4.1 targeted selection of hydraulic valve models should be for the work pressure requirements, the media temperature, the physical and chemical properties of the media, select the type and size of the material matching hydraulic control valve. For regions with high water hardness and easy fouling, such as Guizhou Karst topography, the hydrogen carbonate contained in the water is easily fouled under temperature and water pressure. A larger d1 hydraulic control valve should be selected and the control should be appropriately increased Pipe diameter. 4.2 Proper installation of the selected hydraulic valve control valve model, should be based on product features a reasonable installation. Installation Notes: Select the type and size of the hydraulic valve pressure matching flange; inlet diameter should be greater than or equal to the valve nominal diameter, the outlet should be lower than the float valve. Float valve installation should be more than one meter from the outlet pipe and should be installed in a location conducive to maintenance, such as pool near the manhole; to prevent the hydraulic loose spool structure, the spool should be taken at both ends of the nut to take anti-withdrawal measures. In order to prevent siphon backflow, the water outlet pipe outlet should be set anti-siphon holes or slightly above the control level. In order to prevent the noise and water level fluctuation, the outlet should be set energy dissipation tube. When used, the cut-off valve should be fully open, as the same pool installed more than two valves should maintain the same level. Due to the closure of the main valve to float valve closure lag about 30 ~ 50 seconds, so the tank should have enough spare capacity to prevent overflow. In order to prevent impurities, sand into the valve caused by malfunction, the valve should be installed before the filter. If installed in the basement pool, it should be installed in the underground pump alarm device. 4.3 to enhance the routine maintenance Before installing the hydraulic valve, should pay attention to the pipeline flushing, hydraulic valve in use, should be selected depending on the quality of maintenance time, usually one to two times a year maintenance, when the water quality is poor, should be appropriate Increase the number of maintenance. Specific maintenance methods are as follows: (1) Close the valve before the valve. (2) Unscrew the cap on the valve cover. (3) Remove the valve internal piston, piston rod and guide cover. (4) unscrew the piston rod ends nuts. (5) Remove the gland, seals, disc. (6) Remove the guide gland, seals, disc. After disassembly, should remove the parts of the scale and all kinds of dirt, with steel wire throttle nut on the hole, replace the damaged seal. The order of assembly and disassembly are reversed. 5. Conclusion Select the model of hydraulic control valve, and install it rationally so as to strengthen the daily maintenance of hydraulic control valve, improve the stability of hydraulic control valve and avoid the malfunction of hydraulic control valve, Stable operation, to ensure safe water supply. References [1] Nuclear Design Institute of the second. Water supply and drainage design manual. China Building Industry Press, 2001. [2] water supply project. China Building Industry Press, 1995. [3] Department of Hydraulics, Southwest Jiaotong University. Hydraulics. Xi'an University of Architecture and Technology, 1983. [4] Wang Yonghui, Huang Tinglin. Water Physical Chemistry. Northwestern Polytechnical University Press, 1993. About the author: Zhang Hong (1977.1 -), male, undergraduate, assistant engineer. Abstract: Based on the working principle of hydraulic control valve, the paper analyzes the factors that affect the stable operation of hydraulic control valve from the structure, installation and operating environment of the hydraulic valve, and proposes an improved solution to improve the stable operation of hydraulic control valve. Keywords: hydraulic level control valve working principle of stable operation to improve the program 1, Introduction Hydraulic level control valve is an improved float valve, when the pool or water tower water level drops, the float valve opens drainage, the water pressure in the water pipe will be When the water level rises to the control surface, the float valve is closed and the piston moves downward to close the sealing surface. The valve stops water supply to achieve the purpose of automatically controlling the water level. Because of its power consumption, simple structure, easy installation and construction, the application of pressure and other advantages, in all types of clear water tank (water tank) automatic control of water has a more extensive application. However, due to the influence of water quality and hydraulic factors, the hydraulic level control valve often fails, ranging from waste of water resources, heavy water pumping station, causing serious consequences. Improve the stability of hydraulic control valve, it is very important to ensure safe water supply. 2, the internal structure of the hydraulic water level control valve and the principle of action Hydraulic water level control valve is generally composed of float valve, control tube, hydraulic valve body. Although the appearance of hydraulic control valve body vary, different materials, vertical and horizontal installation forms, but its internal structure and role of the principle is basically the same. The main body of the hydraulic control valve is composed of inlet chamber, water outlet, piston-type valve core, pressure relief cavity and relief port. Set the water pressure P0, pressure relief chamber pressure P1; piston-type valve gravity G, piston-type spool pressure relief chamber end diameter D1, the other end of the diameter D2. The diameter of the orifice connected to the inlet chamber and the pressure relief chamber is d1, and the diameter of the relief port is d2. The friction between the piston-type valve spool and the valve chamber is f, and the supportive force is N. The following is a schematic diagram of the structure of Figure 1 (a second similar structure), for example, the analysis of the piston-type valve force is as follows: Suppose the resultant force of the piston-type valve spool is F, then the force vector formula: F = F1 + F2 + F3 + F4 + f + N + G (1) Expression as algebraic form is as follows: F = P0D22π / 4 + P2 (D12π / 4 - D22π / 4) - P1D12π / 4 ± f-G ± N = (P0D22-P1D12) π / 4 ± f-G + P2 (D12-D22) π / 4 ± N = A ± f-G ± N + B where A = (P0D22-P1D12) π / 4, B = P2 (D12-D22) π / 4; The sign of f is opposite to that of A. When the water level in the pool or water tower drops, when the float valve opens drainage, the water inlet cavity replenishes water through the small hole d1 to the pressure relief cavity. Because the water supply hole d1 <pressure relief hole d2, the water replenishment capacity is less than the pressure relief capacity, the pressure P1 Reduce the spool support force N1 gradually reduced to disappear, there is pressure water into the water pipe P0 overcomes the gravity and friction of the piston-type valve spool to lift it, the above formula F> 0, the sealing surface gradually opened, the hydraulic valve that is open Water to the pool (or water tower). When the pool water level rises to control the surface of water, the float valve is closed and the pressure relief chamber is filled with water more than the pressure relief capacity. N2 gradually decreases and P1 rises (up to P0). The above formula F <0, That is, stop the water supply. Hydraulic control valve under the control of the float, which can automatically control the water level. 3, the factors that affect the stable operation of the hydraulic pressure level control valve 3.2 pressure relief chamber pressure changes When the hydraulic control valve is installed and put into use, (2) where D1, D2, d1, d2G are known constants, affecting the movement of the piston spool force Only the pressure of water P0, the role of P1 and the friction suffered by the piston f. Under normal circumstances: D1≥D2, d1≤d2, the outlet pressure changes within the range of 0≤P2 <P0, discharge pressure 0 <C1 (constant) ≤ P1≤C2 ~ P0. Through the analysis of force, we can see that the safe and reliable operation of the hydraulic valve requires that the pressure in the relief chamber should be properly changed. When the pressure in the relief chamber reaches the minimum, the spool can rise to the maximum opening position. If the piston of the hydraulic control valve The valve spool is strong and can always keep the pressure relief chamber closed and can be tightly combined with the inlet of the water inlet. When the float valve is closed, the pressure in the pressure relief chamber can always rise to C2 (C2 is equal to P0, The method has nothing to do), the piston-type spool in the water pressure P1 and its own gravity G, to overcome the friction f drop and close the hydraulic valve. Visible pressure relief chamber minimum pressure C1 is to determine whether the hydraulic valve can be a key factor in stable operation, pressure relief valve cavity pressure changes in the speed of the decision of the level of sensitivity of the valve. Define the minimum pressure in the pressure relief chamber C1 is the number of stable operation of the hydraulic control valve. When the maximum hydraulic control valve opening, the float valve is stable when the water, the pressure relief chamber pressure P1 = C1. At this point through the replenishment hole, drainage cavity, float valve outlet cross-section of the flow equal; connected to the inlet chamber and the pressure relief chamber channel inlet, pressure relief chamber and float valve outlet (control line) The equation can be C1 influencing factors (cross-sectional position shown in Figure 3 vertical hydraulic control valve installation diagram shown), the following formula holds: ω pass v pass = ω vent ν vent = ω ball ν ball d12 v pass = D12 v Leakage = d ball 2ν ball (3) Z into + P0 / γ + α1ν through 2 / 2g = Z vent + P1 / γ + α2ν vent 2 / 2g + h loss 1 = Z ball + P ball / γ + α3ν ball 2 / 2g + h loss of 2 ........................ (4) finishing the above formula, derived: P1 = C1 = γ (Z ball - Z vent) + P ball / γ + (α3ν ball 2-α2ν vent 2) / 2g + h loss 2-h loss 1)) = γ (Z ball -Z vent) + P0 / γ + (α3 ball 2-α2 v vent 2) / 2g-h loss 3) And subscript: the area corresponding to the cross section ν and subscript: the liquid flow rate corresponding to the cross section Z and subscript: the geometric elevation P and subscript of the cross section corresponding to the water flow Said the flow pressure γ: liquid specific gravity α and subscript: Corresponding kinetic energy dressing coefficient h and subscript: Along the way and local head loss and g: Gravitational acceleration 3.3 Factors that affect the stable operation of the hydraulic control valve 3.3.1 Hydraulic valve structure of their own Hydraulic Valve to reliable operation, requiring piston-type spool solid, flexible lifting, can always keep the pressure relief chamber closed and can be sealed into the water chamber as needed; According to the hydraulic knowledge, it can be seen from (5) that the smaller the pore passage d1 connecting to the pressure relief chamber, the larger the head loss h loss 3, the lower the C1 value. Appropriate to reduce the pore diameter d1 can help reduce the value of C1, float valve opens, the valve core can quickly rise, open the hydraulic valve. When the float valve is closed, the hydraulic pressure valve performance can be improved by reducing (and preventing) the hydraulic valve from closing the valve due to the weakened water replenishment capacity and the slow pressure rise in the pressure relief chamber. However, the small hole diameter d1 channel is too small, easily lead to blocked the hole, resulting in hydraulic valve switch is not working. In addition, increasing the diameter of piston-type valve relief port chamber, help to reduce pressure relief valve closing the role of the pressure chamber; but will increase the pressure on the valve opening P0 requirements. 3.3.2 Hydraulic Valve Installation Hydraulic valve installation, should be the appropriate choice of control pipe diameter and length. Control of pipe diameter increases, the water flow rate will be reduced through the loss of hydraulic control h loss 4, C1 value will be reduced, is conducive to the operation of the hydraulic valve. The diameter of the control tube is generally between dn15 ~ dn40. If the diameter of the control tube is too large, the matching float valve will increase. On the one hand, the float will reduce the water storage space of the water tank and reduce the utilization rate of the water tank. On the other hand, As for the float closing time, pressure relief chamber boost time longer, the hydraulic valve will be delayed off, you need to have a larger pool of effective space in order not to waste water resources. Control of the length of the tube should also be limited to increase the length of the control tube, h loss 4 increases, C1 value increases, pressure relief chamber pressure increased longer, the hydraulic valve will delay closure, adverse and hydraulic valve stable operation. 3.3.3 water pressure and water flow state Hydraulic valve at work, the force caused by the water pressure P0, the lower the water pressure, lift the valve required pressure relief chamber P1 is also low, that is, C1 value is small, not Hydraulic valve is conducive to work. When P0 is low, pressure relief chamber pressure relief, the piston-type valve by the upward pressure can not overcome its own gravity and friction, the hydraulic valve will not open. Due to the material of the valve body parts, P0 can not be too high. High pressure so that the force exerted by the valve core N1N2 increases, the wear and tear on the valve ring seal, affecting the life of the hydraulic valve. Therefore, the hydraulic valve must work in the nominal pressure range. Due to the change of water flow direction, all components in the valve body are subject to the intense flushing and impact of the water flow. Measures must be taken to ensure the structural stability of the valve plug. The components of the valve plug (sealing ring, guide pin, locking bolt, etc.) . 3.3.4 Water Quality Operating Requirements The medium is clean water. The design and installation of the hydraulic valve can ensure that the hydraulic valve does not contain solid particles in the water and does not block the internal size of the valve body, and does not corrode the internal structure of the hydraulic valve. However, the dissolved solids in the water habitat, in the hydraulic valve body and the control pipe fouling, thereby affecting the body of the pressure relief chamber sealing, increasing the spool friction f, spool movement increases the force at the same time Control section of the pipe to reduce the discharge section, the pressure relief chamber drainage capacity decreases, the loss of control head h loss increases 4, C1 value increases, when the C1 value increases to a certain extent, the piston-type spool can not be flexible Exercise, so that the hydraulic valve failure. For high hardness, more soluble solid medium, the need to appropriately increase the diameter of the control tube and strengthen the operation and maintenance of the hydraulic control valve. 4, to improve the steady operation of the hydraulic pressure level control valve program 4.1 targeted selection of hydraulic valve models should be for the work pressure requirements, the media temperature, the physical and chemical properties of the media, select the type and size of the material matching hydraulic control valve. For regions with high water hardness and easy fouling, such as Guizhou Karst topography, the hydrogen carbonate contained in the water is easily fouled under temperature and water pressure. A larger d1 hydraulic control valve should be selected and the control should be appropriately increased Pipe diameter. 4.2 Proper installation of the selected hydraulic valve control valve model, should be based on product features a reasonable installation. Installation Notes: Select the type and size of the hydraulic valve pressure matching flange; inlet diameter should be greater than or equal to the valve nominal diameter, the outlet should be lower than the float valve. Float valve installation should be more than one meter from the outlet pipe and should be installed in a location conducive to maintenance, such as pool near the manhole; to prevent the hydraulic loose spool structure, the spool should be taken at both ends of the nut to take anti-withdrawal measures. In order to prevent siphon backflow, the water outlet pipe outlet should be set anti-siphon holes or slightly above the control level. In order to prevent the noise and water level fluctuation, the outlet should be set energy dissipation tube. When used, the cut-off valve should be fully open, as the same pool installed more than two valves should maintain the same level. Due to the closure of the main valve to float valve closure lag about 30 ~ 50 seconds, so the tank should have enough spare capacity to prevent overflow. In order to prevent impurities, sand into the valve caused by malfunction, the valve should be installed before the filter. If installed in the basement pool, it should be installed in the underground pump alarm device. 4.3 to enhance the routine maintenance Before installing the hydraulic valve, should pay attention to the pipeline flushing, hydraulic valve in use, should be selected depending on the quality of maintenance time, usually one to two times a year maintenance, when the water quality is poor, should be appropriate Increase the number of maintenance. Specific maintenance methods are as follows: (1) Close the valve before the valve. (2) Unscrew the cap on the valve cover. (3) Remove the valve internal piston, piston rod and guide cover. (4) unscrew the piston rod ends nuts. (5) Remove the gland, seals, disc. (6) Remove the guide gland, seals, disc. After disassembly, should remove the parts of the scale and all kinds of dirt, with steel wire throttle nut on the hole, replace the damaged seal. The order of assembly and disassembly are reversed. 5. Conclusion Select the model of hydraulic control valve, and install it rationally so as to strengthen the daily maintenance of hydraulic control valve, improve the stability of hydraulic control valve and avoid the malfunction of hydraulic control valve, Stable operation, to ensure safe water supply. References [1] Nuclear Design Institute of the second. Water supply and drainage design manual. China Building Industry Press, 2001. [2] water supply project. China Building Industry Press, 1995. [3] Department of Hydraulics, Southwest Jiaotong University. Hydraulics. Xi'an University of Architecture and Technology, 1983. [4] Wang Yonghui, Huang Tinglin. Water Physical Chemistry. Northwestern Polytechnical University Press, 1993. About the author: Zhang Hong (1977.1 -), male, undergraduate, assistant engineer.
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