A method to prevent excessive deviation of drum water level

Abstract

The present invention relates to a method for preventing excessive deviation of the drum water level, comprising: step 1, calibrating the zero water level baseline of the drum under different working conditions to eliminate the factors causing large water level deviation due to the operation mode; step 2, regularly checking the changes in the indications of each water level measuring point to obtain the reason for the large deviation of the drum water level; the reason is that the water level measuring pipeline is unqualified; step 3, performing a drum water level simulation test according to the calibration results and the collected water level parameters under different working conditions; step 4, using the shutdown opportunity to complete the transformation and insulation of the measuring pipeline, and thoroughly flushing and leak checking the measuring pipeline before putting it into use; step 5, optimizing the algorithm according to the water level calibration results, observing the measurement effect and gradually putting into use the relevant automatic and protective functions. The present invention effectively solves the chronic problem of large deviation of the drum water level during the operation of the unit. There is no need to purchase new equipment, nor is there any need to re-drill holes in the drum and lay cables in high-temperature areas, which effectively curbs the operational risks.

Description

Technical Field

[0001] The invention relates to the technical field of electric power and nonferrous metals, and in particular to a method for preventing excessive deviation of a drum water level. Background Art

[0002] The steam drum is a cylindrical pressure vessel used in water tube boilers to separate steam and water, purify steam, form a water circulation loop and store boiler water. Its main functions are to receive water from the economizer, separate steam and water, supply water to the circulation loop, and deliver saturated steam to the superheater.

[0003] The drum water level is the water position information in the boiler drum and is one of the most important monitoring parameters for boiler operation. Maintaining a certain water level in the drum can slow down the speed of steam pressure change when the operating conditions change, and play a certain buffering role when the feed water and load are not coordinated for a short time. Drum water level measurement is an important guarantee for timely and accurate feedback of water level information and safe operation of the boiler.

[0004] Bias, also known as apparent error, refers to the difference between an individual measurement value and the measured average value. It can be used to measure the precision of the measurement results.

[0005] Keeping the boiler drum water level within the normal range (±50mm) is an important safety indicator for boiler operation. The drum water level will change frequently due to changes in load, combustion conditions and feed water flow. If the water level is too high or fluctuates sharply, it will cause the steam quality to deteriorate and carry water, resulting in salt formation on the heating surface. In severe cases, it will cause water shock vibration of the turbine and damage to the blades. If the water level is too low, it will cause the blowdown to fail, the addition of chemicals into the furnace will enter the steam, and even cause steam to be carried by the downcomer, resulting in deterioration of the boiler water circulation and large-scale explosion of the boiler tube. The above-mentioned vicious accidents caused by problems in the measurement and control of the drum water level are common, seriously affecting the safe operation of thermal power units.

[0006] At present, the reference water column and zero water level benchmark in the calculation formula for drum water level measurement all use the original design parameters. Due to the limitations of the installation process, the actual parameters of each water level meter are not the same, resulting in a greater deviation in the drum water level measurement as the unit load increases; the influence of the insulation and heating process of the measuring pipeline has not been fully considered, which directly affects the full condensation of the medium in the measuring pipeline; the software correction cannot meet the requirements for full-process monitoring of the drum water level. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preventing excessive deviation of the drum water level, to achieve full monitoring and control of the drum water level through accurate measurement of the differential pressure value, to solve the long-standing problem of inaccurate drum water level measurement; to eliminate the hidden danger that the "three-out-of-three" of the drum water level algorithm is actually two-out-of-one due to large water level deviation; to improve the reliability of the thermal control system; to reduce the operating difficulty of the operating staff on duty; and to improve the economy of the unit.

[0008] The present invention provides

[0009] A method for preventing excessive deviation of drum water level, comprising:

[0010] Step 1, by calibrating the drum zero water level reference line under different working conditions, eliminate the factors that cause large water level deviation due to the operating mode;

[0011] Step 2, regularly checking the changes in the indications of each water level measuring point to obtain the reason for the large deviation of the drum water level; the reason is that the water level measuring pipeline is unqualified;

[0012] Step 3, performing a drum water level simulation test according to the calibration results and the collected water level parameters under different operating conditions;

[0013] Step 4: Use the opportunity of furnace shutdown to complete the measurement pipeline transformation and insulation work, and thoroughly flush and check for leaks on the measurement pipeline before putting it into use;

[0014] Step 5, optimize the algorithm according to the water level calibration results, observe the measurement effect and gradually invest in related automatic,protection.

[0015] Furthermore, the step 1 comprises:

[0016] (1) Fill the horizontal connecting pipe with water and remove all bubbles;

[0017] (2) Based on the zero water level reference line of one side of the drum, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the first drum water level 1 balance chamber, observe the liquid level and read the reading from the liquid level to the center line of the steam inlet pipe after the liquid level is stable, and measure three times; when the liquid level is higher than the center line of the steam inlet pipe, the reading is recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line;

[0018] (3) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the first drum water level 1, observe the liquid level and read the reading from the liquid level to the center line of the root of the water inlet pipe after the liquid level is stable, and measure three times; when the liquid level is lower than the center line of the steam inlet pipe, the reading should be recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line;

[0019] (4) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the first drum water level 1, observe that the liquid level is stable, and make a mark directly. Measure three times; the mark will be used as the basis for checking the zero water level reference line during the operation of the unit;

[0020] (5) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the second drum water level 2 balance chamber, observe the liquid level and read the reading from the liquid level to the center line of the steam inlet pipe after the liquid level is stable, and measure three times; when the liquid level is higher than the center line of the steam inlet pipe, the reading is recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line;

[0021] (6) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the second drum water level 2, observe the liquid level and read the reading from the liquid level to the center line of the inlet root after the liquid level is stable, and measure three times; when the liquid level is lower than the center line of the steam inlet pipe, the reading is recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line;

[0022] (7) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the water inlet pipe on the high pressure side of the second drum water level 2, observe that the liquid level is stable, and make a mark directly. Measure three times; the mark will be used as the basis for checking the zero water level reference line during the operation of the unit;

[0023] (8) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the third drum water level 3 balance chamber, observe the liquid level and read the reading from the liquid level to the center line of the steam inlet pipe after the liquid level is stable, and measure three times; when the liquid level is higher than the center line of the steam inlet pipe, the reading is recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line;

[0024] (9) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the third drum water level 3, observe the liquid level and read the reading from the liquid level to the center line of the root of the water inlet pipe after the liquid level is stable, and measure three times; when the liquid level is lower than the center line of the steam inlet pipe, the reading is recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line;

[0025] (10) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the third drum water level 3, observe that the liquid level is stable, and make a mark directly. Measure three times; the mark is used as the basis for checking the zero water level reference line during the operation of the unit;

[0026] (11) Taking the zero water level reference line of the drum on the same side as the reference line, lead the horizontal connecting pipe to the electric contact water level gauge and observe that the liquid level is stable. Then make a mark directly and measure three times. The mark will be used as the basis for checking the zero water level reference line during the operation of the unit.

[0027] Further, the step 3) comprises:

[0028] (1) During the shutdown period, the differential pressure values ​​and compensation parameters of each drum water level from before grid connection to full load conditions are collected from historical trends, and a parameter table is prepared;

[0029] (2) Substitute each parameter into the water level correction formula according to the parameter table to simulate the water level measurement value; replace the reference water column and zero baseline in the correction formula with the calibration result;

[0030] (3) Compare the deviation between the simulated test water level and the actual water level of the drum water level to verify the accuracy of the measurement results.

[0031] Further, the step 5) comprises:

[0032] (1) Modify the range of each drum water level transmitter to the value designed by the boiler manufacturer and confirm that it is correct;

[0033] (2) Set the lower limit parameter of drum water level measurement points 1, 2, and 3 in the DCS configuration file to 0, and the upper limit parameter to the boiler manufacturer's design value, and confirm that they are correct;

[0034] (3) Close the two doors on the high-pressure side of the drum water level transmitter locally; open its balance door; close the two doors on the low-pressure side; and confirm that the operation is in place;

[0035] (4) The DCS room staff reads the differential pressure signal after it becomes stable and records the zero point migration value;

[0036] (5) Calculate the upper limit value of channels 1, 2, and 3 of each drum water level measurement point and record it;

[0037] (6) According to the test results, the lower limit parameter of the drum water level measurement point is set to the zero migration value, and the upper limit parameter is set to the calculation result of the previous step;

[0038] (7) Gradually put the drum water level transmitter into operation and observe whether the instrument valve and joints are leaking;

[0039] (8) Check that the insulation and heating are normal;

[0040] (9) Open the calculation logic of drum water level 1, 2, and 3, and modify the reference water column in its calculation function block to the calibration result; modify the zero water level reference parameter to the calibration result, and check that it is correct;

[0041] (10) After the modified data is effective, exit.

[0042] By means of the above scheme, the water level reference line is dynamically calibrated by preventing the drum water level from deviating too much, the reliability of the reference water column parameters is greatly improved, the instrument pipelines and valves are rearranged, the errors of leakage and local pipeline blockage are controlled, and the chronic problem of large deviation of the drum water level during the operation of the unit is effectively solved. At the same time, most of the work of the present invention is carried out during the shutdown period, and the transformation cost is low compared with similar achievements, and there is no need to purchase new equipment, nor is there any need to re-open holes in the drum and lay cables in the high-temperature area, which effectively curbs the operational risks.

[0043] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the present invention;

[0045] Figure 2 It is a piping diagram;

[0046] Figure 3 This is a schematic diagram of the actual distribution of boiler water level gauges. DETAILED DESCRIPTION

[0047] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0048] Ginseng Figure 1 As shown,

[0049]

[0050] L is the height difference of the sampling tubes on the positive and negative pressure sides, ρ a is the reference water column density, ρ s is the saturated steam density, ρ w is the saturated water density, △P is the differential pressure value measured by the differential pressure transmitter, H0 is the height of the zero water level reference line, and ΔH is the measurement deviation caused by the ambient temperature.

[0051] The method for preventing excessive deviation of the drum water level provided in this embodiment includes the construction of a measurement pipeline and the optimization of a drum water level algorithm. Through the water level calibration under different working conditions on site, the transformation of the water level measurement pipeline is completed according to the space and construction conditions of the work site, and the parameters of the drum water level algorithm are optimized to achieve accurate measurement of the water level, which specifically includes:

[0052] 1) Calibrate the bubble water level

[0053] By calibrating the drum zero water level reference line under different operating conditions, factors that cause large water level deviations due to operating modes can be eliminated. Figure 3 This is a schematic diagram of the actual distribution of steam drum water level gauges.

[0054] The solution is as follows:

[0055] (1) The horizontal connecting pipe is filled with water and all bubbles are discharged.

[0056] (2) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the drum water level 1 balance chamber, observe the liquid level and read the reading from the liquid level to the center line of the steam inlet pipe after the liquid level is stable, and measure three times. Note that when the liquid level is higher than the center line of the steam inlet pipe, the reading should be recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line.

[0057] (3) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the drum water level 1, observe the liquid level and read the reading H0 from the liquid level to the center line of the inlet root after the liquid level is stable, and measure three times. Note that when the liquid level is lower than the center line of the steam inlet pipe, the reading should be recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line.

[0058] (4) Based on the zero water level reference line of the drum on side A, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the drum water level 1, and mark it directly after observing that the liquid level is stable. Measure three times. This serves as the basis for checking the zero water level reference line during unit operation.

[0059] (5) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the drum water level 2 balance chamber, observe the liquid level and read the reading from the liquid level to the center line of the steam inlet pipe after the liquid level is stable, and measure three times. Note that when the liquid level is higher than the center line of the steam inlet pipe, the reading should be recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line.

[0060] (6) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the drum water level 2, observe the liquid level and read the reading H0 from the liquid level to the center line of the inlet root after the liquid level is stable, and measure three times. Note that when the liquid level is lower than the center line of the steam inlet pipe, the reading should be recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line.

[0061] (7) Based on the zero water level reference line of the drum on side A, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of drum water level 2, observe the liquid level and mark it directly after it stabilizes, and measure it three times. This serves as the basis for checking the zero water level reference line during unit operation.

[0062] (8) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the drum water level 3 balance chamber, observe the liquid level and read the reading from the liquid level to the center line of the steam inlet pipe after the liquid level is stable, and measure three times. Note that when the liquid level is higher than the center line of the steam inlet pipe, the reading should be recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line.

[0063] (9) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe at the drum water level 3, observe the liquid level and read the reading H0 from the liquid level to the center line of the inlet root after the liquid level is stable, and measure three times. Note that when the liquid level is lower than the center line of the steam inlet pipe, the reading should be recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line.

[0064] (10) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the drum water level 3, observe the liquid level and mark it directly after it stabilizes, and measure it three times. This serves as the basis for checking the zero water level reference line during the operation of the unit.

[0065] (11) Based on the zero water level reference line of the drum on side A, lead the horizontal connecting pipe to the electric contact water level gauge to observe the liquid level and mark it directly after it stabilizes. Measure three times. This will serve as the basis for checking the zero water level reference line during unit operation.

[0066] 2) Check water level parameters

[0067] Regularly check the changes in the indications at each water level measuring point to determine that unqualified water level measuring pipelines are the main cause of large deviations in the drum water level.

[0068] 3) Drum water level simulation test

[0069] The simulation test was completed based on the calibration results and the collected water level parameters under different working conditions. The scheme is as follows:

[0070] (1) During the shutdown period, the differential pressure values ​​and compensation parameters of each drum water level from before grid connection to full load conditions are collected from historical trends, and a parameter table is prepared.

[0071] (2) Substitute each parameter into the water level correction formula according to the parameter table to simulate the water level measurement value. Note that the reference water column and zero baseline in the correction formula have been changed to the calibration result.

[0072] (3) Compare the deviation between the simulated test water level and the actual water level of the drum water level to verify the accuracy of the measurement results.

[0073] 4) Instrument pipeline modification

[0074] Take advantage of the furnace shutdown opportunity to complete the measurement pipeline renovation and insulation work, and thoroughly flush and check for leaks on the measurement pipeline before putting it into use.

[0075] Ginseng Figure 2 As shown, 1-steam drum; 2-steam side door; 3, single-chamber balance container; 4, steam side door; 5, water level transmitter high pressure door; 6-water level transmitter high pressure door; 7-water side door; 8-water side door; 9-water level transmitter low pressure door; 10-water level transmitter low pressure door; 11-water level transmitter balance door; 12-water level transmitter. Among them, water level transmitter high pressure door 5, water level transmitter high pressure door 6, water level transmitter low pressure door 9, water level transmitter low pressure door 10, water level transmitter balance door 11 and its connecting pipes are pipelines that need to be modified.

[0076] The instrument pipeline modification plan is as follows:

[0077] 1. Remove the original insulation material, determine the installation position of the transmitter three-valve group according to the on-site pipeline direction, and draw the assembly drawing.

[0078] 2. Cut the meter tube 75mm downstream of the first elbow after the transmitter, and make a spectrum on the fracture section for material testing. Confirm that it is suitable for the newly replaced meter tube.

[0079] 3. Place the three-valve group in water and weld the inlet side meter pipe. The two inlet pipes are perpendicular to the upstream plane of the valve group and parallel to each other. The upstream meter pipe is inserted and welded.

[0080] 4. The outlet side meter pipe of the three-valve group should be welded with a valve joint (taken from JW-320P D6) in advance to connect with the transmitter. The joint must be perpendicular to the meter pipe. Due to space limitations, the new outlet meter pipe will be 50mm shorter than the old pipe. The meter pipe with the joint is welded vertically on the downstream surface of the valve group, and the groove needs to be finely ground (also done in water to prevent the internal packing of the three-valve group from burning). Butt weld the upstream meter pipe of the three-valve group.

[0081] 5. The weld is inspected and qualified

[0082] 6. Use air to sweep away impurities in the sampling pipeline.

[0083] 5) Water level algorithm parameter optimization: Optimize the algorithm according to the water level calibration results, observe the measurement effect and gradually invest in related automatic protection.

[0084] The water level algorithm parameter optimization scheme is as follows:

[0085] 1. Modify the range of each drum water level transmitter to the boiler manufacturer's design value and confirm that it is correct.

[0086] 2. Set the lower limit parameter of drum water level measurement points 1, 2, and 3 in the DCS configuration file to 0, and the upper limit parameter to the boiler manufacturer's design value. Confirm that they are correct;

[0087] 3. Close the two doors on the high-pressure side of the drum water level transmitter locally; open its balance door; close the two doors on the low-pressure side; and confirm that the operation is in place;

[0088] 4. DCS room personnel read the differential pressure signal after it becomes stable and record the zero point migration value;

[0089] 5. Calculate the upper limit value of channels 1, 2, and 3 of each drum water level measuring point and record them.

[0090] 6. According to the test results, the lower limit parameter of the drum water level measurement point is set to the zero point migration value, and the upper limit parameter is set to the calculation result of the previous step.

[0091] 7. Gradually put the drum water level transmitter into operation and observe whether the instrument valves and joints are leaking.

[0092] 8. Check that the insulation and heating are normal.

[0093] 9. Open the calculation logic of drum water level 1, 2, 3, and modify the reference water column in its calculation function block to the calibration result; modify the zero water level reference parameter to the calibration result, and check that it is correct;

[0094] 10. Exit after the modified data takes effect.

[0095] The method for preventing excessive deviation of the drum water level greatly improves the reliability of the reference water column parameters by dynamically calibrating the water level baseline, and controls the errors of leakage and local pipeline blockage by rearranging the instrument pipelines and valves, effectively solving the chronic problem of large deviation of the drum water level during the operation of the unit. At the same time, most of the work of the present invention is carried out during the shutdown period, and the transformation cost is low compared with similar achievements, and there is no need to purchase new equipment, nor is there any need to re-open holes in the drum and lay cables in the high-temperature area, which effectively curbs the operation risks.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preventing excessive deviation of drum water level, characterized in that: include: Step 1, by calibrating the drum zero water level reference line under different working conditions, eliminate the factors that cause large water level deviation due to the operating mode; Step 2, regularly checking the changes in the indications of each water level measuring point to obtain the reason for the large deviation of the drum water level; the reason is that the water level measuring pipeline is unqualified; Step 3, performing a drum water level simulation test according to the calibration results and the collected water level parameters under different operating conditions; Step 4: Use the opportunity of furnace shutdown to complete the measurement pipeline transformation and insulation work, and thoroughly flush and check for leaks on the measurement pipeline before putting it into use; Step 5: Optimize the algorithm according to the water level calibration results, observe the measurement effect and gradually put into use the relevant automatic protection; The step 1 comprises: (1) Fill the horizontal connecting pipe with water and remove all bubbles; (2) Based on the zero water level reference line of the drum on the A side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the balance chamber of the drum water level measuring point 1. After observing that the liquid level is stable, read the reading from the liquid level to the center line of the steam inlet pipe. Measure three times. When the liquid level is higher than the center line of the steam inlet pipe, the reading is recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line. (3) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the drum water level measuring point 1. After observing that the liquid level is stable, read the reading from the liquid level to the center line of the root of the water inlet pipe. Measure three times. When the liquid level is lower than the center line of the steam inlet pipe, the reading should be recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line. (4) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the drum water level measuring point 1, observe that the liquid level is stable, and make a mark directly. Measure three times; the mark will be used as the basis for checking the zero water level reference line during the operation of the unit; (5) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the balance chamber of the drum water level measuring point 2. After observing that the liquid level is stable, read the reading from the liquid level to the center line of the steam inlet pipe. Measure three times; when the liquid level is higher than the center line of the steam inlet pipe, the reading is recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line; (6) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the drum water level measuring point 2. After observing that the liquid level is stable, read the reading from the liquid level to the center line of the root of the water inlet pipe. Measure three times; when the liquid level is lower than the center line of the steam inlet pipe, the reading is recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line; (7) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the drum water level measuring point 2, observe that the liquid level is stable, and make a mark directly. Measure three times; the mark will be used as the basis for checking the zero water level reference line during the operation of the unit; (8) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the steam inlet pipe of the balance chamber of the drum water level measuring point 3. After observing that the liquid level is stable, read the reading from the liquid level to the center line of the steam inlet pipe. Measure three times. When the liquid level is higher than the center line of the steam inlet pipe, the reading is recorded as a negative value, indicating that the elevation of the measurement point is lower than the zero water level reference line. (9) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the center line of the root of the water inlet pipe of the drum water level measuring point 3. After observing that the liquid level is stable, read the reading from the liquid level to the center line of the root of the water inlet pipe. Measure three times; when the liquid level is lower than the center line of the steam inlet pipe, the reading is recorded as a positive value, indicating that the elevation of the measurement point is higher than the zero water level reference line; (10) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the high-pressure side water inlet pipe of the drum water level measuring point 3, observe that the liquid level is stable, and make a mark directly. Measure three times; the mark will be used as the basis for checking the zero water level reference line during the operation of the unit; (11) Based on the zero water level reference line of the drum on the same side, lead the horizontal connecting pipe to the electric contact water level gauge to observe the liquid level and mark it directly after it stabilizes. Measure three times; the mark will be used as the basis for checking the zero water level reference line during the operation of the unit; The step 3 comprises: (1) During the shutdown period, the differential pressure values ​​and compensation parameters of each drum water level from before grid connection to full load conditions are collected from historical trends, and a parameter table is prepared; (2) Substitute each parameter into the water level correction formula according to the parameter table to simulate the water level measurement value; replace the reference water column and zero baseline in the correction formula with the calibration result; (3) Compare the deviation between the simulated test water level and the actual water level of the drum water level to verify the accuracy of the measurement results; The step 5 comprises: (1) Modify the range of each drum water level transmitter to the value designed by the boiler manufacturer and confirm that it is correct; (2) Set the lower limit parameters of the drum water level measurement point 1, drum water level measurement point 2, and drum water level measurement point 3 channels in the DCS configuration file to 0, and the upper limit parameters to the boiler manufacturer's design value, and confirm that they are correct; (3) Close the two doors on the high-pressure side of the drum water level transmitter locally; open its balance door; close the two doors on the low-pressure side; and confirm that the operation is in place; (4) The DCS room staff reads the differential pressure signal after it becomes stable and records the zero point migration value; (5) Calculate the upper limit value of each channel of drum water level measuring point 1, drum water level measuring point 2, and drum water level measuring point 3, and record them; (6) According to the test results, the lower limit parameter of the drum water level measurement point is set to the zero migration value, and the upper limit parameter is set to the calculation result of the previous step; (7) Gradually put the drum water level transmitter into operation and observe whether the instrument valve and joints are leaking; (8) Check that the insulation and heating are normal; (9) Open the calculation logic of drum water level measurement point 1, drum water level measurement point 2, and drum water level measurement point 3, and modify the reference water column in its calculation function block to the calibration result; modify the zero water level reference parameter to the calibration result, and check that it is correct; (10) After the modified data is effective, exit.

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