流量计、液位计、温度传感器在净化水处理的应用（The application of flowmeter, liquid level gauge and temperature sensor in purifying water treatment）

流量计、液位计、温度传感器在净化水处理的应用（The application of flowmeter, liquid level gauge and temperature sensor in purifying water treatment） 流量计、液位计、温度传感器在净化水处理的应用(The application of flowmeter, liquid level gauge and temperature sensor in purifying water treatment) The application of flowmeter, liquid level gauge and temperature sensor in purifying water treatment In modern water purification plants, each production process is always related to the instrument and the control technology. Instrument can detect the continuous process parameters, according to the manual or automatic control of the data of parameters, thus coordination between supply and demand, the system between each component, the relationship between the various water treatment processes, so that all kinds of equipment and facilities to get more sufficient and reasonable use. At the same time, due to the continuous comparison between the measured values and the set value, the deviation of the detection instrument can be adjusted immediately to ensure the quality of water treatment. According to the parameters of the instrument, it can further adjust and control the amount of the drug, ensure the reasonable operation of the pump unit, make the management more scientific and achieve the purpose of economic operation. The instrument has the function of continuous detection and the more alarm, so as to handle the accident timely. Instrumentation is also a prerequisite for computer control. Therefore, in the advanced water treatment system, the automatic instrument has a very important role. A water treatment system commonly used in the classification of instruments The instrument for water supply engineering can be divided into two categories: one is the instrument which monitors the physical parameters of the production process, such as temperature, pressure, liquid level and flow. This kind of instrument adopt domestic watch, its performance and quality basically can satisfy requirement. The other category belongs to the analysis instrument which detects water quality, such as the turbidity, pH value, dissolved oxygen content, residual chlorine and SCD value of water. These special instruments develop relatively late in our country, so it is usually economical and reliable to choose foreign advanced products. The testing instrument is directly related to the effect of water supply automation. In engineering design process, from the performance of the instrument, quality, price, spare parts, such as after-sales service for repeated comparisons, we generally adopt imported instrument and method of combining the domestic instrument. The construction mode and monitoring parameters of the monitoring system of the two water purification plant 1. The construction mode of monitoring system of water purification plant The monitoring system of the water purification plant is generally composed of the two levels of the management of the water plant and the on-site monitoring layer, which is monitored by the principle of centralized management and decentralized control. In engineering design, the waterworks plant-level computer system (i.e., host) is located in the centre control room, each site monitoring stations (substation) the number and position according to the technological process and the location of the structure, degree of dispersion. The setting of the site station of general surface water works is: the station of water inlet pumping station, the reaction precipitation and the addition of chlorine and drug distribution station, the filter station, the pumping station and the transformer distribution station, the sludge treatment sub-station. The data of each monitoring instrument are sent to the computer system, which can be displayed, controlled and printed, recorded and reported to the monitoring station. 2. Monitoring parameters of each station A. Monitoring parameters for inlet pump room Water quality parameters: source water turbidity, pH value, water temperature, dissolved oxygen, etc. Operation parameters: adjust pool water level, water suction well water level, source water flow, pump power, pump station total power, etc. B. Reaction precipitation, plus chlorine and drug station Water quality parameters: the export turbidity of sediment pond, residual chlorine after filtration, SCD value. Operation parameters: sedimentation tank level, pre-precipitation flow, liquid level of stirring tank, liquid level of drug, concentration of liquid medicine, and mud level of sedimentation tank. C. Filter sub-station Water quality parameters: post-filtration turbidity and residual chlorine. Operation parameters: water level of filter tank, loss of water head, backwash water flow, flushing water level. Water pump room and transformer room station Water quality parameters: outgoing water flow, residual chlorine. Operating parameters: water pressure, flow rate, water level, water suction well water level, ac voltage, ac current, power, etc. E. sludge treatment sub-station Operation parameters: backflow pond water level, water volume, concentrated water level, backflow water turbidity. The three water treatment system is used in selecting type and designing 1. General requirements for instrument selection (1) precision: the accuracy of the measurement results of the meter in normal conditions, the smaller the error, the higher the accuracy. The accuracy of the physical test instrument in the production process is plus or minus 1%. The accuracy of the water quality analysis instrument is plus or minus 2% (the accuracy of the turbidity meter with high turbid water is 5% or minus 5%). (2) response time: when measuring the measured, the indicator value always has to go through a period of time to be displayed. This period is the response time of the instrument. It is an important indicator that an instrument can reflect the change of parameters as soon as possible. The response time required for the water quality analysis instrument shall not exceed 3min. (3) output signal: instrument analog output should be 4 ~ 20 ma DC signal, load capacity not less than 600 Ω. (4) the protection level of the instrument should meet the requirements of the environment, and generally should not be lower than IP65, and the testing instrument for the pharmaceutical investment system should be able to resist corrosion. (5) the four-wire instrument power supply is 220V AC and 50Hz, and the two-wire instrument power supply is 24V DC. (6) field monitoring instrument should be used with digital display. (7) the working power of the instrument should be independent, and should not be Shared with the computer to ensure that the power supply is not interfered with each other during failure and maintenance, so that each can operate reliably and reliably. (8) to make the computer can detect voltage transformer and current transformer of the abnormal signals and alarm, design selection of the input signal voltage and current transducer should be larger than the current and voltage transformer, which respectively 0 ~ 6 a and 0 ~ 120 v. (9) we should select instrument manufacturers who can provide reliable services and have rich experience. 2. Water level measurement The following factors should be considered in selecting the liquid level meter: (1) measurement objects, such as the physical and chemical properties of the tested media, as well as the working pressure and temperature, installation conditions and the rate of liquid level change; (2) the measurement and control requirements, such as measuring range, precision measuring (or control), display mode, the instruction, remote indication, and the computer interface, security, anti-corrosion, reliability and convenience of construction. The main points of liquid level and selection in water supply engineering are as follows: A. Floating ball level gauge Put a hollow float in the liquid, and when the liquid level changes, the float will produce the same displacement as the liquid level. A mechanical or electrical method is used to measure the displacement of the floating ball, and its accuracy is plus or minus (1 ~ 2) %, which is not suitable for high viscosity liquid, and its output has switch control and continuous output. In the design of the water purification plant, the liquid level is used to measure the liquid level of the well to control the automatic stop of the pump. B. Static pressure (or differential pressure) type level gauge Because the static pressure of the liquid column is proportional to the liquid level, Therefore, the liquid level can be measured by using the pressure gauge to measure the static pressure of the liquid column on the base surface. According to the density of the measured medium and the measuring range of the liquid, pressure or differential pressure range is calculated, and the pressure gauge or differential pressure gauge, which is suitable for the range and accuracy of the measurement, is chosen. The accuracy of this level gauge is plus or minus (0.5 ~ 2) %. -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --