Boiler is an indispensable heat source equipment in industrial production. Because of its high temperature and high pressure characteristics, boiler drum water level control is one of the most important indicators for safe operation of boilers within the allowable range of the process. If the water level is too high, it will affect the steam-water separation effect and affect the steam quality. In severe cases, a large amount of water in the steam will cause water damage to the equipment caused by water impact; if the water level is too low, the water circulation will be destroyed, and the water-cooled pipe wall will cause dry burning, explosion and other major accidents. Bringing significant economic and personal damage to businesses and operators. Therefore, ensuring the accuracy of the water level measurement is of great significance to the safe operation of the boiler. This paper briefly introduces the method of boiler water level measurement, analyzes the cause of boiler drum water level deviation, and summarizes the solution of drum water level deviation. 1 Drum water level measurement method (1) Two-color water level gauge. Working principle: The two-color water level gauge consists of a red and green light source and a body cavity. The red and green light emitted by the light source is directed from both sides to the water level. In the vapor phase, the red light is directed straight ahead, and the green light is obliquely incident on the sidewalls and absorbed. In the liquid phase, since the refraction of water causes the green light to be directed straight ahead, and the red light is obliquely directed onto the wall, the vapor phase red liquid phase green can be seen when viewed directly in front. The image is then sent to the control room via the camera for monitoring. 2 Cause analysis of boiler drum water level deviation (1) Boiler body and sampling position measurement error. 1 During the installation process, the horizontal deviation of the sides of the steam drum should be ≤ 5mm, but under normal circumstances, after the boiler is operated for several years, the deviation caused by the subsidence of the bracket will increase or even reach 15 ~ 20mm. 2 In general, the boiler body manufacturer only performs the cold state determination on the elevation of the boiler water level sampling position. Under the actual installation environment, different ambient temperatures and different sampling pipeline lengths, especially the balanced container without fixed bracket, will also lead to cold correction. The elevation of the elevation is deviated from the elevation of the hot state, which deviates from the water level measurement. Leisuwash specializing in manufacture Automatic Car Wash Machine, Touchless Car Wash , automatic touchless car wash, Touchless Car Wash Equipment, robot car wash, smart car wash system, Leisuwash 360 , Leisuwash Leibao 360 , laserwash 360, leisuwash Touchless Car Wash Machine, Leisu Wash touchless car wash automatic, leisu wash 360 high pressure touchless car wash equipment, robo car wash, touch free car wash, leisuwash 360 touch free car wash, leisuwash 360 price, automatic car wash price, leisuwash in malaysia, no touch automatic Car Wash Machine , Leisuwash 360 Mini , Leisuwash Sg fully Automatic Car Wash Equipment. Leisuwash S90 Drying Automatic Car Wash Equipment,Leisuwash S90 Drying,Automatic Leisuwash S90 Drying Car Wash Machine,Leisuwash S90 Drying Car Wash Machine Hangzhou Leisu Cleaning Equipment Co.,Ltd , https://www.leisuwashtouchless.com
(2) Electric contact water level gauge. Working principle: Due to the great difference in the conductivity of water and steam, the electrical resistance between the electrical contact on the measuring cylinder and the wall of the cylinder is also very different. In the liquid state, due to the small dielectric resistance, when the electrical contact and the wall of the cylinder are added The current flowing through the DC voltage is large, and the current flowing through the electrical contact is not small when the liquid is not immersed in the liquid surface. The current flowing between the two states is very different, and can be fed as a signal to the secondary instrument, and then displayed after being amplified. And control the output to achieve the purpose of displaying the liquid level, so that remote monitoring can be realized.
(3) The differential pressure level transmitter is equipped with a condensing tank or a double chamber balancing container. Working principle: The liquid level in the cylindrical container connected to the steam side of the condensation tank remains unchanged, and the output of the differential pressure transmitter changes with the height of the water level in the steam drum. The liquid level in the reference cup of the double chamber balance vessel remains unchanged. The output of the differential pressure transmitter varies with the height of the water level in the drum. However, the temperature of the balance vessel differs greatly from the temperature of the drum, in order to eliminate the actual water level. Value deviations need to be corrected by DCS or secondary instrumentation.
(2) Errors caused by operational problems and improper maintenance. 1 Improper or inconsistent insulation of the sampling line of the differential pressure transmitter will cause the average temperature of each sampling line to be difficult to determine, and the compensation coefficient cannot be accurately determined, resulting in measurement deviation. It is recommended that the sampling lines of the same-side differential pressure transmitter should be insulated together to avoid the water level measurement deviation caused by this. 2 Measurement error caused by leakage inside the drain valve. Since the drum water level measurement range is relatively small, the internal leakage of the drain valve will affect the water level measurement. It is recommended to ensure the water quality of the boiler and the thorough flushing of the measuring cylinder during operation. 3 The furnace center flame center offset, or the long-running furnace coking degree is inconsistent due to the difference in the water level deviation caused by the difference in circulation efficiency on both sides of the drum.
(3) Common measurement instruments produce measurement errors. 1 two-color water level gauge: two-color water level gauge once blocked valve; sewage valve leakage; pollution inside the official cavity. When the boiler is in the first ignition operation, the valve is clogged or even contaminated by the glass tube due to incomplete washing and water quality problems, resulting in deviation of the two-color water level gauge. Therefore, in the startup process, the boiler should be washed in strict accordance with the process and monitor the water quality change. When the water quality is good, the steam drum pressure reaches 0.5 MPa, and then the water level gauge is washed. 2 electric contact water level gauge: electrode contamination. When the boiler is started for the first time, the water quality is very poor; it contains a lot of rust and salt and adheres to the electrode, which easily reduces the electric resistance between the electrode and the wall, causing display errors. 3 differential pressure liquid level transmitter supporting condensing tank or double chamber balance container: differential pressure liquid level transmitter sampling tube insulation and heating inconsistency; differential pressure transmitter and double chamber balanced chamber sewage valve leakage; The range does not correspond to the balance container size.
3 Water level deviation treatment measures (1) Standardized installation of sampling lines. Both the sampling tube and the sampling valve on both sides of the steam drum should be well insulated and the length should be controlled within 10 meters. The same side sampling tube should be insulated to the transmitter body and should be evenly heated; each water level measuring device has an independent sampling port. In order to prevent leakage inside the drain valve, two shut-off valves can be used in series.
(2) Do a good job in maintenance and repair. The hot state of the sampling position should be strictly checked. The condensing cylinder can be installed with brackets for thermal adjustment; the zero water level deviation of the drum water level can be corrected in time. The transmitter periodically checks for zero drift; the line should be flushed with a drum pressure of 2 MPa.
(3) Artificial temperature coefficient correction and optimization of DCS system compensation formula. The differential pressure measuring device of the external balanced container performs temperature correction by manual measurement in different seasons to reduce the error; optimize the system compensation formula and reduce the deviation caused by the empirical formula.
4 Conclusion <br> In short, there are many reasons for the deviation of water level measurement, but the correct equipment installation and standard operation and maintenance are still the key to ensure the accuracy of drum water level measurement. Therefore, in construction, strictly follow the construction technical specifications, the flushing, sewage discharge and leak detection should be strengthened during operation, and the accuracy and reliability of the water level measurement system should be increased to prevent unnecessary jumping and jumping of the water level due to large deviation of the water level. The resulting economic loss.
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