A method for calibrating safety valves of utility boilers

Abstract

The present invention relates to a method for calibrating safety valves of a power station boiler. This method calibrates the safety valves of the power station boiler after the steam turbine of the generating unit is shut down. During calibration, the superheated steam in the boiler superheater is guided into the reheater steam pipeline, and the reheater steam pressure is adjusted to be stable at the set pressure working point. The safety valves of the reheater are calibrated at the pressure working point to determine the corresponding compressed air lifting pressure, forming a reheater steam pressure - compressed air lifting pressure calibration point, and judging whether the calibration point is within the set safety range. Compared with the prior art, the present invention has the advantages of high safety, accurate calibration, and high efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of power station boiler safety control, and particularly to a method for calibrating safety valves of power station boilers. Background Art

[0002] Pressure-bearing equipment is generally equipped with safety valves. The safety valves of power station boilers, especially those of large boilers, are equipped with controlled safety valves. Shanghai Shenergy Caojing Power Generation Co., Ltd. is equipped with 8 electric-pneumatic controlled safety valves for boiler reheaters produced by German Bopp & Reuther, which have measurement, testing and control devices. According to the manufacturer's instructions, the calibration of the safety valves is completed under two different working conditions, that is, the medium - the reheated steam pressure is at 4.5 MPa and 3 MPa respectively in the two working conditions. The calibration principle is: at the stable point pressure of the medium - reheated steam of 4.5 MPa, release the air in the upper cylinder of the reheater safety valve to make it communicate with the atmosphere, and introduce the compressed air in the test device into the lower cylinder, and slowly increase the pressure of the compressed air in the test device to make this pressure overcome the spring pressure of the safety valve. When the safety valve slightly opens and the opening sound is heard at this time, stop increasing the pressure of the compressed air in the test device, and record the compressed air pressure P1 at this time. Similarly, in another working condition, increase the pressure of the compressed air in the test device at the stable point pressure of the medium - reheated steam of 3 MPa until the safety valve slightly opens, and record the compressed air pressure P2. Plot the recorded data on Figure 1 and integrate a straight line Y through the point of 7.5 MPa on the abscissa. Draw two parallel lines Y1 and Y2 at ±3% of the straight line Y, and check whether all the points obtained from the recorded data fall between Y1 and Y2.

[0003] If both P1 and P2 fall between Y1 and Y2, it indicates that the safety valve calibration is qualified. If a point falls outside Y1 and Y2, it indicates that this point is unqualified and the compression force of the safety valve spring needs to be adjusted.

[0004] Since calibrating the safety valve in this way requires stabilizing the unit load and medium pressure under normal operating conditions, there are several major disadvantages:

[0005] 1. Under normal operation of the unit, in order to maintain the stability of the load and medium pressure, it is necessary to withdraw from the automatic generation control (AGC) operation mode, which affects the regulation of the power grid load and frequency.

[0006] 2. It is difficult to adjust the medium pressure to the required 4.5 MPa and 3 MPa and maintain stability (otherwise the calibration result is inaccurate), and to meet this requirement, the operation adjustment takes a long time.

[0007] 3. Since it is under normal operating conditions, if problems such as the jamming of the safety valve spool or the malfunction of the solenoid valve of the calibration device (jamming) occur, the problems need to be solved by shutting down the boiler.

[0008] 4. Since it is necessary to adjust the fuel quantity (or coal type) and feed water pressure to regulate the reheat steam pressure, it often causes the medium pressure to fluctuate and exceed the pressure, threatening the stable operation of the unit and the safety of the calibration personnel.

[0009] Therefore, there is an urgent need to design a new safety valve calibration method. Summary of the Invention

[0010] The purpose of the present invention is to provide a safety valve calibration method for a power station boiler to overcome the defects existing in the above-mentioned prior art.

[0011] The purpose of the present invention can be achieved by the following technical solutions:

[0012] A safety valve calibration method for a power station boiler, which calibrates the safety valve of the power station boiler after the steam turbine of the generating unit is shut down. During calibration, the superheated steam in the boiler superheater is guided into the reheat steam pipeline, and the reheat steam pressure is adjusted to be stable at the set pressure working point. The safety valve of the reheater is calibrated at the pressure working point to determine the corresponding compressed air lifting pressure, forming a reheat steam pressure-compressed air lifting pressure calibration point, and judging whether the calibration point is within the set safety range.

[0013] Preferably, there are two set pressure working points, which are 4.5 Mpa and 3 Mpa respectively, and then the safety valve of the reheater is calibrated at the two pressure working points respectively.

[0014] Preferably, during the calibration process, the safety valve is first calibrated at the pressure working point of 4.5 Mpa for the reheat steam pressure, and then the safety valve is calibrated at the pressure working point of 3 Mpa for the reheat steam pressure.

[0015] Preferably, the method specifically includes the following steps:

[0016] S1. Shut down the steam turbine of the generating unit;

[0017] S2. Set the lifting pressure protection value of the safety valve of the reheater;

[0018] S3. Adjust the high-pressure bypass valve and low-pressure bypass valve in the reheat steam pipeline to make the reheat steam pressure stable at 4.5 Mpa;

[0019] S4. Calibrate the safety valve of the reheater at the 4.5 Mpa pressure working point to determine the compressed air lifting pressure p1, forming the first reheat steam pressure-compressed air lifting pressure calibration point P1: (4.5 Mpa, p1);

[0020] S5. Adjust the high-pressure bypass valve and low-pressure bypass valve in the reheat steam pipeline again to make the reheat steam pressure stable at 3 Mpa;

[0021] S6. Conduct the safety valve calibration of the reheater at the working point of 3 Mpa, determine the compressed air lifting pressure p2, and form the second reheater steam pressure - compressed air lifting pressure calibration point P2: (3 Mpa, p2);

[0022] S7. Judge whether both P1 and P2 fall within the set safety range. If so, the safety valve calibration passes; otherwise, the safety valve calibration fails.

[0023] Preferably, the set pressure protection value of the reheater safety valve in step S2 is set to 5.1 Mpa.

[0024] Preferably, the method of adjusting the reheater steam pressure to be stable at 4.5 Mpa in step S3 is: open the high-pressure bypass valve and gradually reduce the low-pressure bypass valve to gradually increase the reheater steam pressure to 4.5 Mpa.

[0025] Preferably, the method of adjusting the reheater steam pressure to be stable at 3 Mpa in step S5 is: reduce the opening of the high-pressure bypass valve and gradually increase the low-pressure bypass valve to gradually reduce the reheater steam pressure to 3 Mpa.

[0026] Preferably, the method of calibrating the reheater safety valve at the pressure working point is specifically as follows:

[0027] Close the main intake valve of the upper cylinder, exhaust the upper cylinder, and confirm that the pressure of the upper cylinder gradually reaches 0 Mpa;

[0028] Press the "TEST" button on the test device for calibrating the safety valve, confirm that the "TEST" indicator light is on, and the solenoid valve operates normally when electrified;

[0029] Open the intake knob of the lower cylinder, inflate the lower cylinder, observe the pressure change of the lower cylinder, continuously increase the pressure of the lower cylinder. When the reheater safety valve operates, release the "TEST" button, stop inflating the lower cylinder, and record the current magnitude of the compressed air lifting pressure.

[0030] Preferably, during the exhaust process of the upper cylinder, slowly open the exhaust valve of the upper cylinder to exhaust gradually.

[0031] Preferably, during the inflation process of the lower cylinder, slowly adjust the intake knob of the lower cylinder to increase the pressure gradually.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The present invention conducts the safety valve calibration after shutdown, which is one of the keys to the improvement of this working method, and can ensure the safety of the unit operation and the safety of the calibration personnel;

[0034] (2) The present invention can obtain relatively stable reheater steam pressures of 3 MPa and 4.5 MPa without adjusting the fuel quantity, coal type, nozzle angle, and water supply quantity, and does not require special adjustment of the boiler combustion conditions, thus avoiding damage to the originally well - operating boiler combustion conditions caused by special adjustment of the boiler combustion conditions, preventing combustion and medium pressure fluctuations. Poor adjustment often leads to medium overpressure, which may threaten the stable operation of the unit and the personal safety of on - site calibration personnel;

[0035] (3) The present invention uses a high - pressure bypass valve and a low - pressure bypass valve to control the reheater steam pressure (a stable pressure can be set on the CRT), making the required pressure stable and accurate, so that the verified data is very correct;

[0036] (4) The present invention does not need to withdraw from AGC operation and will not affect the regulation of power grid load and frequency;

[0037] (5) The present invention will not have problems such as the need to stop the furnace due to the jamming of the safety valve spool or problems (jamming) with the solenoid valve of the calibration device;

[0038] (6) This work of the present invention has been applied in this power plant many times and operates well. This method can be promoted in the power generation industry. This method can shorten the calibration time by 5 - 7 hours, improving the productivity and efficiency. Description of the Drawings

[0039] Figure 1 It is a diagram for processing existing safety valve calibration data;

[0040] Figure 2 It is a flow block diagram of a method for calibrating a safety valve of a power station boiler according to the present invention;

[0041] Figure 3 It is a schematic diagram of a method for calibrating a safety valve of a power station boiler according to the present invention.

[0042] In the figure, 1 is the reheater safety valve, 2 is the high - pressure bypass valve, and 3 is the low - pressure bypass valve. Detailed Embodiments

[0043] The present invention will be described in detail below with reference to the drawings and specific embodiments. Note that the following description of the embodiments is only illustrative in nature, and the present invention is not intended to limit the objects to which it is applicable or its uses, and the present invention is not limited to the following embodiments.

[0044] Embodiment

[0045] Combined with Figure 2 and Figure 3 shown, a method for calibrating a safety valve of a power station boiler. This method calibrates the safety valve of the power station boiler after the steam turbine of the generating unit is shut down. During calibration, the superheated steam in the boiler superheater is guided into the reheater steam pipeline. Figure 3The arrow indicates the flow direction of superheated steam. Adjust the reheat steam pressure to stabilize at the set pressure working point, and calibrate the safety valve 1 of the reheater at the pressure working point to determine the corresponding compressed air lifting pressure, forming a reheat steam pressure - compressed air lifting pressure calibration point, and judge whether the calibration point is within the set safety range. There are two set pressure working points, which are 4.5 Mpa and 3 Mpa respectively, and then calibrate the safety valve 1 of the reheater at the two pressure working points respectively. During the calibration process, first calibrate the pressure working point with a reheat steam pressure of 4.5 Mpa, and then calibrate the pressure working point with a reheat steam pressure of 3 Mpa.

[0046] The method specifically includes the following steps:

[0047] S1. Stop the steam turbine of the generator set. During the actual operation, the safety valve calibration can be carried out when the steam turbine of the generator set is stopped.

[0048] S2. Set the popping pressure and pressure protection value of the safety valve 1 of the reheater. Among them, the popping pressure of the safety valve of the reheater is set to 5.1 Mpa.

[0049] S3. Open the high-pressure bypass valve 2 and gradually reduce the opening of the low-pressure bypass valve 3 to gradually increase the reheat steam pressure to 4.5 Mpa.

[0050] S4. Calibrate the safety valve 1 of the reheater at the 4.5 Mpa pressure working point to determine the compressed air lifting pressure p1, forming the first reheat steam pressure - compressed air lifting pressure calibration point P1: (4.5 Mpa, p1).

[0051] S5. Reduce the opening of the high-pressure bypass valve 2 and gradually increase the opening of the low-pressure bypass valve 3 to gradually reduce the reheat steam pressure to 3 Mpa.

[0052] S6. Calibrate the safety valve 1 of the reheater at the 3 Mpa pressure working point to determine the compressed air lifting pressure p2, forming the second reheat steam pressure - compressed air lifting pressure calibration point P2: (3 Mpa, p2).

[0053] The specific method of calibrating the safety valve 1 of the reheater at the set pressure working point in the above steps S4 and S6 is as follows:

[0054] Close the main intake valve of the upper cylinder, exhaust the upper cylinder, and confirm that the pressure of the upper cylinder gradually reaches 0 Mpa;

[0055] Press the "TEST" button on the test device (EPC5400 cabinet) of the calibration safety valve, confirm that the "TEST" indicator light is on, and the solenoid valve is energized and operates normally;

[0056] Open the intake knob of the lower cylinder to inflate the lower cylinder. Observe the pressure change of the lower cylinder and continuously increase the pressure of the lower cylinder. When the safety valve 1 of the reheater operates, release the "TEST" button to stop inflating the lower cylinder, and record the current pressure increase of the compressed air.

[0057] During the exhaust process of the upper cylinder, slowly open the exhaust valve of the upper cylinder to gradually exhaust. During the inflation process of the lower cylinder, slowly adjust the intake knob of the lower cylinder to gradually increase the pressure.

[0058] S7. Judge whether both P1 and P2 fall within the set safety range. If so, the safety valve calibration passes; otherwise, the safety valve calibration fails. That is, plot the reheater steam pressure - compressed air pressure increase calibration point P1 and the reheater steam pressure - compressed air pressure increase calibration point P2 in Figure 1 to see if P1 and P2 fall between the straight line Y1 and the straight line Y2. If so, the safety valve calibration is qualified; if not, the tightness of the safety valve spring needs to be adjusted. After the unit is put into operation, calibrate the safety valve again. Figure 1 In the straight line Y1 and the straight line Y2 are the threshold curves given by the safety valve manufacturer for safety calibration.

[0059] The above embodiments are only examples and do not represent the limitation of the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical idea of the present invention.

Claims

1. A method for calibrating safety valves of utility boilers, characterized in that, This method is to calibrate the safety valves of the power station boiler after the steam turbine of the generator set is shut down. During calibration, the superheated steam in the boiler superheater is guided into the reheater steam pipeline, and the reheater steam pressure is adjusted to be stable at the set pressure working point. The safety valves of the reheater are calibrated at the pressure working point to determine the corresponding compressed air lifting pressure, forming a reheater steam pressure - compressed air lifting pressure calibration point, and judging whether the calibration point is within the set safety range; There are two set pressure working points, which are 4.5 MPa and 3 MPa respectively. Then, the safety valves of the reheater are calibrated at the two pressure working points respectively; During the calibration process, first calibrate the pressure working point where the reheater steam pressure is 4.5 MPa, and then calibrate the pressure working point where the reheater steam pressure is 3 MPa; This method specifically includes the following steps: S1. Shut down the steam turbine of the generator set; S2. Set the popping pressure protection value of the safety valve of the reheater; S3. Adjust the high-pressure bypass valve and low-pressure bypass valve in the reheater steam pipeline to make the reheater steam pressure stable at 4.5 MPa; S4. Calibrate the safety valve of the reheater at the 4.5 MPa pressure working point to determine the compressed air lifting pressure p1, forming the first reheater steam pressure - compressed air lifting pressure calibration point P1: (4.5 MPa, p1); S5. Adjust the high-pressure bypass valve and low-pressure bypass valve in the reheater steam pipeline again to make the reheater steam pressure stable at 3 MPa; S6. Calibrate the safety valve of the reheater at the 3 MPa pressure working point to determine the compressed air lifting pressure p2, forming the second reheater steam pressure - compressed air lifting pressure calibration point P2: (3 MPa, p2); S7. Judge whether both P1 and P2 fall within the set safety range. If so, the safety valve calibration passes; otherwise, the safety valve calibration fails; The method of adjusting the reheater steam pressure to be stable at 4.5 MPa in step S3 is: open the high-pressure bypass valve and gradually close the low-pressure bypass valve to gradually increase the reheater steam pressure to 4.5 MPa; The method of adjusting the reheater steam pressure to be stable at 3 MPa in step S5 is: reduce the opening of the high-pressure bypass valve and gradually open the low-pressure bypass valve to gradually reduce the reheater steam pressure to 3 MPa.

2. The method for calibrating a safety valve of a power station boiler according to claim 1, characterized in that In step S2, the popping pressure protection value of the safety valve of the reheater is set to 5.1 MPa.

3. A method for calibrating a safety valve of a power station boiler according to claim 1, characterized in that, The method of calibrating the safety valve of the reheater at the pressure working point is specifically as follows: Close the main valve for air intake of the upper cylinder, exhaust the upper cylinder, and confirm that the pressure of the upper cylinder gradually reaches 0 MPa; Press the "TEST" button on the test device for calibrating the safety valve, confirm that the "TEST" indicator light is on, and the solenoid valve is energized and operates normally; Open the air intake knob of the lower cylinder, inflate the lower cylinder, observe the pressure change of the lower cylinder, continuously increase the pressure of the lower cylinder. When the safety valve of the reheater operates, stop inflating the lower cylinder, release the "TEST" button, and record the current magnitude of the compressed air lifting pressure.

4. A method for calibrating a safety valve of a power station boiler according to claim 3, characterized in that, Slowly open the exhaust valve of the upper cylinder to exhaust during the exhaust process of the upper cylinder.

5. A method for calibrating a safety valve of a power station boiler according to claim 3, characterized in that, During the inflation process of the lower cylinder, slowly adjust the air intake knob of the lower cylinder to gradually increase the pressure.

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