An online test method for PCV valve control circuit

Abstract

The present invention discloses an online test method for a PCV valve control circuit, comprising the following steps: S1-S4, modifying the PCV valve control circuit; S51, closing the first solenoid valve and the second solenoid valve; S52, the first coil of the solenoid reversing valve is energized and the second coil is de-energized; S53, judging whether the pressure value displayed by the first pressure switch is greater than the pressure value displayed by the second pressure switch, if so, performing step S53, if not, the test fails, and troubleshooting is performed; S54, the first coil of the solenoid reversing valve is de-energized and the second coil is energized; S55, judging whether the pressure value displayed by the second pressure switch is greater than the pressure value displayed by the first pressure switch. The present invention can improve the problems of wasting working fluid and affecting the stability and safety of boiler operation in the existing PCV valve online test by simply modifying the control circuit.

Description

Technical Field

[0001] The utility model relates to a boiler safety protection technology of a thermal power plant, in particular to an online test method of a PCV valve control loop. Background Art

[0002] In thermal power plants, safety valves and PCV valves are usually installed on the steam pipe at the outlet of the boiler superheater header. The PCV valve is located between the outlet of the superheater header and the inlet of the safety valve. The main functions of the PCV valve and the safety valve are to prevent overpressure in the boiler and discharge the superheated steam directly into the atmosphere without cooling, which is simple. Among them, the main function of the PCV valve is to eliminate the action of the safety valve caused by pressure fluctuations during boiler operation. It is opened before the safety valve is activated to discharge excess steam to ensure the normal operation of the boiler under the specified pressure, thereby protecting the safety valve, reducing the number of actions of the safety valve, and extending the service life of the safety valve. When the superheated steam pressure of the boiler is high, the PCV valve opens to relieve pressure first, and the set pressure is slightly lower than that of the safety valve. The full opening process of the PCV valve only takes a few tenths of a second, and the action is fast, which can ensure that the boiler safety valve does not act, especially for a series of complex controls such as quick opening of the steam turbine bypass, reducing the combustion intensity, and maintaining the water level of the steam drum. It wins precious buffer time. In addition to acting according to the set pressure, the PCV valve can also be remotely operated by the operator to manually open or reseat it, and the operation flexibility is strong.

[0003] Generally, the PCV valve is controlled and operated by the PCV valve control circuit, which includes a solenoid reversing valve (two-position five-way solenoid reversing valve), a cylinder, and a compressed air pipeline arranged between the solenoid reversing valve and the cylinder. The control air source is provided by the air compressor, and the compressed air enters the air inlet of the solenoid reversing valve. The two working ports of the solenoid reversing valve are respectively connected to the upper cylinder air source port and the lower cylinder air source port of the cylinder through the compressed air pipeline. The corresponding air path between the solenoid reversing valve and the cylinder is connected to realize the movement of the cylinder piston, so that the movement of the cylinder piston drives the PCV valve to operate. In order to ensure the safety of the boiler unit, it is necessary to frequently test and overhaul the PCV valve control circuit so that the PCV valve can operate normally. At present, during the operation of the unit, when conducting a PCV valve control loop test, it is necessary to frequently open or close the two-position five-way electromagnetic reversing valve, and then perform pressure detection on the gas source connecting pipe on the PCV valve side to detect whether the PCV valve is normally opened or closed. This wastes the working fluid invisibly, and when the boiler pressure is normal, opening the PCV valve to release the working fluid can easily affect the stability of the unit's gas pressure. When the boiler steam pressure is too high, closing the PCV valve for testing affects the safety of the boiler operation. Summary of the invention

[0004] The purpose of the present invention is to provide an online test method for a PCV valve control loop to solve the problems of easy waste of working fluid and poor safety and stability of boiler operation in the existing PCV valve control loop test method.

[0005] To solve the above technical problems, the purpose of the present invention is achieved as follows:

[0006] An online test method for a PCV valve control loop comprises the following steps:

[0007] S1. Reconstruct the PCV valve control circuit during the unit overhaul: select a dual-electrically controlled two-position five-way electromagnetic reversing valve as the electromagnetic reversing valve, the electromagnetic reversing valve includes an air inlet, two exhaust ports, two working ports and two coils, the air inlet of the electromagnetic reversing valve is connected to the air compressor, the two exhaust ports are respectively the first exhaust port and the second exhaust port, the two working ports are respectively the first working port and the second working port, and the two coils are respectively the first coil and the second coil;

[0008] S2, a first gas source connecting pipe is provided between the first working port and the upper cylinder gas source port of the cylinder, and a second gas source connecting pipe is provided between the second working port and the lower cylinder gas source port of the cylinder;

[0009] S3, installing a first pressure switch on the first gas source connecting pipe, and installing a second pressure switch on the second gas source connecting pipe;

[0010] S4, a first solenoid valve is provided on the first gas source connecting pipe, the first solenoid valve is located between the first pressure switch and the gas source port of the upper cylinder, and a second solenoid valve is provided on the second gas source connecting pipe, the second solenoid valve is located between the second pressure switch and the gas source port of the lower cylinder;

[0011] S5. Start the unit to conduct the test, which specifically includes the following steps:

[0012] S51, close the first solenoid valve and the second solenoid valve;

[0013] S52, the first coil of the electromagnetic reversing valve is energized and the second coil is de-energized;

[0014] S53, determining whether the pressure value displayed by the first pressure switch is greater than the pressure value displayed by the second pressure switch, if so, proceeding to step S54, if not, the test fails and an operator is required to perform troubleshooting;

[0015] S54, the first coil of the electromagnetic reversing valve loses power and the second coil gains power;

[0016] S55. Determine whether the pressure value displayed by the second pressure switch is greater than the pressure value displayed by the first pressure switch. If so, the test is successful; if not, the test fails and the operator is required to perform troubleshooting.

[0017] The step also includes step S6. In step S6, the test is ended after the test in step S55 is successful, and the first coil and the second coil are both de-energized.

[0018] In step S6, after the first coil and the second coil are both de-energized, the first solenoid valve and the second solenoid valve are opened.

[0019] The first solenoid valve and the second solenoid valve are both normally open solenoid valves.

[0020] In step S5, the air compressor always fills the air inlet of the electromagnetic reversing valve with compressed air, and the pressure value of the compressed air is 0.6 MPa.

[0021] In step S52, when the first coil of the electromagnetic reversing valve is energized and the second coil is de-energized, the first gas source connecting pipe is connected.

[0022] In step S54, when the first coil of the electromagnetic reversing valve loses power and the second coil gains power, the second gas source connecting pipe is connected.

[0023] The beneficial effects of the present invention are:

[0024] In the present invention, a simple transformation is performed on the existing PCV valve control loop, which is simple and easy to implement. When the PCV is tested online, it is possible to ensure that the control loop is accurately tested online without stopping the machine, and faults are discovered and eliminated in time. In the entire test process, the PCV valve is not opened, so no steam working medium is wasted, thereby ensuring the safe and stable operation of the boiler unit, extending the service life of the PCV valve, and virtually reducing the test cost of the PCV valve control loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0026] Figure 1 It is a schematic diagram of the structure of the PCV valve control circuit after modification of the present invention;

[0027] Figure 2 It is a specific flow chart of step S5 of the present invention.

[0028] Description of Reference Numerals

[0029] 1. Solenoid reversing valve; 11. Air inlet; 12. First working port; 13. First exhaust port; 14. Second working port; 15. Second exhaust port; 16. First coil; 17. Second coil; 2. Cylinder; 21. Upper cylinder air source port; 22. Lower cylinder air source port; 23. Piston; 31. First air source connecting pipe; 32. Second air source connecting pipe; 41. First pressure switch; 42. Second pressure switch; 51. First solenoid valve; 52. Second solenoid valve. DETAILED DESCRIPTION

[0030] The technical scheme in the embodiment of the present invention is described clearly and completely below in conjunction with the accompanying drawings in the embodiment of the present invention. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0031] like Figure 1-2 As shown, an online test method of a PCV valve control circuit of the present invention comprises the following steps:

[0032] S1. During the overhaul of the unit, the PCV valve control circuit is modified, that is, in the modified PCV valve control circuit, the unit is in a shutdown state: a double-electrically controlled two-position five-way electromagnetic reversing valve is selected as the electromagnetic reversing valve 1, and the electromagnetic reversing valve 1 includes an air inlet 11, two exhaust ports, two working ports and two coils. The air inlet 11 of the electromagnetic reversing valve 1 is connected to the air compressor, the two exhaust ports are respectively a first exhaust port 13 and a second exhaust port 15, the two working ports are respectively a first working port 12 and a second working port 14, and the two coils are respectively a first coil 16 and a second coil 17.

[0033] S2, a first gas source connecting pipe 31 is connected between the first working port 12 and the upper cylinder gas source port 21 of the cylinder 2, and a second gas source connecting pipe 32 is connected between the second working port 14 and the lower cylinder gas source port 22 of the cylinder 2.

[0034] S3. Install a first pressure switch 41 on the first gas source connecting pipe 31, and install a second pressure switch 42 on the second gas source connecting pipe 32. The set values ​​of the first pressure switch 41 and the second pressure switch 42 are both 0.4Mpa, that is, an alarm is triggered when the values ​​of the first pressure switch 41 and the second pressure switch 42 are lower than 0.4Mpa.

[0035] S4. A first solenoid valve 51 is provided on the first gas source connecting pipe 31, and the first solenoid valve 51 is located between the first pressure switch 41 and the upper cylinder gas source port 21. A second solenoid valve 52 is provided on the second gas source connecting pipe 32, and the second solenoid valve 52 is located between the second pressure switch 42 and the lower cylinder gas source port 22. Both the first solenoid valve 51 and the second solenoid valve 52 are normally open solenoid valves.

[0036] Steps S1-S4 are modifications to the PCV valve control circuit during unit maintenance, shutdown, and furnace shutdown. After the step modification is completed, the control circuit test of step S5 can be performed at any time during the operation of the unit.

[0037] S5. Start the unit to conduct the test, which specifically includes the following steps:

[0038] S51, close the first solenoid valve 51 and the second solenoid valve 52;

[0039] S52, the first coil 16 of the electromagnetic reversing valve 1 is energized and the second coil 17 is de-energized; in this step, when the first coil 16 of the electromagnetic reversing valve 1 is energized and the second coil 17 is de-energized, the air inlet 11 is connected to the first working port 12 and connected to the first air source connecting pipe 31, and the first air source connecting pipe 31 is connected (that is, the first air source connecting pipe 31 is connected to the air inlet 11); the second exhaust port 15 is connected to the second working port 14, and the second air source connecting pipe 32 is connected to the second exhaust port 15, and is connected to the outside atmosphere. At this time, the compressed gas enters the upper cylinder air source port 21 of the cylinder 2 through the first air source connecting pipe 31, pushing the piston 23 of the cylinder 2 to move to the bottom of the cylinder body. If there is no problem with the pipeline, the pressure in the first air source connecting pipe 31 should be greater than that in the second air source connecting pipe 32.

[0040] S53, determining whether the pressure value displayed by the first pressure switch 41 is greater than the pressure value displayed by the second pressure switch 42, if so, proceeding to step S54, if not, the test fails and the operator is required to perform troubleshooting;

[0041] S54, the first coil 16 of the electromagnetic reversing valve 1 loses power and the second coil 17 gains power; in this step, when the first coil 16 of the electromagnetic reversing valve 1 loses power and the second coil 17 gains power, the air inlet 11 is connected to the second working port 14 and connected to the second air source connecting pipe 32, and the second air source connecting pipe 32 is connected (that is, the second air source connecting pipe 32 is connected to the air inlet 11); the first exhaust port 13 is connected to the first working port 12, the first air source connecting pipe 31 is connected to the first exhaust port 13, and the outside atmosphere is introduced. At this time, the compressed gas enters the lower cylinder air source port 22 of the cylinder 2 through the second air source connecting pipe 32. If there is no problem with the pipeline, the pressure in the second air source connecting pipe 32 should be greater than that in the first air source connecting pipe 31.

[0042] S55. Determine whether the pressure value displayed by the second pressure switch 42 is greater than the pressure value displayed by the first pressure switch 41. If so, the test is successful. If not, the test fails and the operator is required to perform troubleshooting.

[0043] S6. In step S6, after the test of step S55 is successful, the test is ended, and the first coil 16 and the second coil 17 are both de-energized. At this time, the gas circuit state of S54 is maintained. In this step, after the first coil 16 and the second coil 17 are both de-energized, the first solenoid valve 51 and the second solenoid valve 52 are opened, so that the control circuit is switched to a normal working state, providing a gas source for the control circuit for the normal operation of the PCV valve. Since the first solenoid valve 51 and the second solenoid valve 52 are normally open solenoid valves, the first solenoid valve 51 and the second solenoid valve 52 are closed in the energized state, and the first solenoid valve 51 and the second solenoid valve 52 are opened, and it is only necessary to de-energize the first solenoid valve 51 and the second solenoid valve 52.

[0044] In step S5, the air compressor always fills the air inlet of the electromagnetic reversing valve 1 with compressed air, and the pressure value of the compressed air is 0.6 MPa.

[0045] The present invention can improve the problems of wasting working fluid and affecting boiler operation stability and safety in the existing PCV valve online test by simply modifying the control loop.

Claims

1. An online test method for a PCV valve control circuit, characterized in that: The following steps are involved: S1. Reconstruct the PCV valve control circuit during the unit overhaul: select a dual-electrically controlled two-position five-way electromagnetic reversing valve as the electromagnetic reversing valve, the electromagnetic reversing valve includes an air inlet, two exhaust ports, two working ports and two coils, the air inlet of the electromagnetic reversing valve is connected to the air compressor, the two exhaust ports are respectively the first exhaust port and the second exhaust port, the two working ports are respectively the first working port and the second working port, and the two coils are respectively the first coil and the second coil; S2, a first gas source connecting pipe is provided between the first working port and the upper cylinder gas source port of the cylinder, and a second gas source connecting pipe is provided between the second working port and the lower cylinder gas source port of the cylinder; S3, installing a first pressure switch on the first gas source connecting pipe, and installing a second pressure switch on the second gas source connecting pipe; S4, a first solenoid valve is provided on the first gas source connecting pipe, the first solenoid valve is located between the first pressure switch and the gas source port of the upper cylinder, and a second solenoid valve is provided on the second gas source connecting pipe, the second solenoid valve is located between the second pressure switch and the gas source port of the lower cylinder; S5. Start the unit to conduct the test, which specifically includes the following steps: S51, closing the first solenoid valve and the second solenoid valve; S52, the first coil of the electromagnetic reversing valve is energized and the second coil is de-energized; S53, determining whether the pressure value displayed by the first pressure switch is greater than the pressure value displayed by the second pressure switch, if so, proceeding to step S54, if not, the test fails and an operator is required to perform troubleshooting; S54, the first coil of the electromagnetic reversing valve loses power and the second coil gains power; S55. Determine whether the pressure value displayed by the second pressure switch is greater than the pressure value displayed by the first pressure switch. If so, the test is successful; if not, the test fails and the operator is required to perform troubleshooting.

2. The online test method of the PCV valve control circuit according to claim 1, characterized in that: The step also includes step S6. In step S6, the test is ended after the test in step S55 is successful, and the first coil and the second coil are both de-energized.

3. The online test method of the PCV valve control circuit according to claim 2, characterized in that: In step S6, after the first coil and the second coil are both de-energized, the first solenoid valve and the second solenoid valve are opened.

4. The online test method of the PCV valve control circuit according to claim 1, characterized in that: The first solenoid valve and the second solenoid valve are both normally open solenoid valves.

5. The online test method of the PCV valve control circuit according to claim 1, characterized in that: In step S5, the air compressor always fills the air inlet of the electromagnetic reversing valve with compressed air, and the pressure value of the compressed air is 0.6 MPa.

6. The online test method of the PCV valve control circuit according to claim 1, characterized in that: In step S52, when the first coil of the electromagnetic reversing valve is energized and the second coil is de-energized, the first gas source connecting pipe is connected.

7. The online test method of the PCV valve control circuit according to claim 1, characterized in that: In step S54, when the first coil of the electromagnetic reversing valve loses power and the second coil gains power, the second gas source connecting pipe is connected.

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