A protection circuit and method for preventing sealed oil pressure low start-up of a large machine

Abstract

This invention relates to the field of sealing oil system control technology, and discloses a protection circuit and method to prevent the turning gear of a large machine from starting when the sealing oil pressure is low. The circuit includes a low sealing oil pressure node circuit, which monitors the sealing oil system pressure in real time and outputs a node switch signal as one of the conditions for starting the turning gear; a PLC control unit, which integrates turning gear start interlock control logic, solenoid valve action logic, and low oil pressure indicator display logic, used to receive the node switch signal and determine whether the sealing oil pressure is lower than a preset threshold; and an execution unit, including a turning gear start interlock module, a solenoid valve control module, and an indicator light module, configured to cut off the turning gear motor start circuit, interlock the turning gear solenoid valve action, and trigger the low oil pressure indicator light when the sealing oil pressure is lower than the preset threshold. This application solves the problem of starting the turning gear when the sealing oil system is not in operation or when the oil pressure is low, avoids mechanical damage caused by wear of the sealing tiles, improves system safety, and reduces intervention lag.

Description

Technical Field

[0001] This invention relates to the field of sealing oil system control technology, specifically to a protection circuit and method for preventing low sealing oil pressure during the start-up of a large machine turning gear. Background Technology

[0002] In the operation and maintenance of large rotating machinery such as steam turbines and generators, the sealing oil system is one of the key links to ensure the safe and stable operation of the unit. This system continuously supplies sealing oil at appropriate pressure to the shaft seal gap, preventing the leakage of internal media (such as gas, steam, or lubricating oil) while also lubricating important components such as bearings. Maintaining stable sealing oil pressure is crucial, especially during the low-speed turning gear phase involved in unit start-up, shutdown, and troubleshooting. However, under actual operation and current technological conditions, the control and protection of the sealing oil system during the turning gear process still has significant shortcomings. If the oil pressure is lower than the set value or an effective oil film cannot be established in time, it is not only difficult to isolate working fluids such as steam, leading to steam accumulation in the cylinder, increased temperature difference between the upper and lower cylinders, and uneven heating of the rotor causing thermal bending, but it also complicates the start-up process. Rotor bending further induces abnormal vibration, increases starting resistance, prolongs unit start-up time, and increases operational risks.

[0003] More seriously, existing technical solutions are not perfect in terms of interlocking protection and condition monitoring, especially in the preparation stage before unit startup, where there is a risk of accidental start-up of the turning gear before the sealing oil system is fully operational. In this situation, dry friction occurs between the journal and the sealing tile due to the lack of oil film lubrication and pressure isolation, which will cause abnormal wear of the sealing tile in a short time. Continued wear will further damage the sealing structure. In extreme cases, the sealing tile will come into hard contact with the high-speed rotating generator rotor, easily grinding grooves on the rotor surface, leading to rotor dynamic imbalance, complete seal failure, and secondary risks such as medium leakage, bearing temperature rise, and friction sparks. Ultimately, this will force the unit to shut down unplanned, or even cause serious equipment damage and safety accidents. Therefore, how to ensure the reliable operation and stable pressure of the sealing oil system during the turning gear stage has become an urgent technical problem to be solved in the safe operation of large rotating machinery. Summary of the Invention

[0004] The present invention aims to provide a protection circuit and method to prevent the turning gear of a large machine from starting when the sealing oil pressure is low, thereby solving the problem that the existing sealing oil system causes wear of the sealing tiles when starting the turning gear without being put into operation, and the secondary risks caused by the grooves worn into the generator rotor at the sealing tiles.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a protection circuit for preventing low sealing oil pressure during the start-up of a large turning gear, comprising: The low-pressure sealing oil node circuit is set in the large machine turning gear control system. It is configured to monitor the sealing oil system pressure in real time and output a node switch signal as one of the conditions for starting the turning gear. The PLC control unit is electrically connected to the low sealing oil pressure node circuit and integrates the turning gear start interlock control logic, solenoid valve action logic and low oil pressure indicator display logic. It is used to receive node switch signals and determine whether the sealing oil pressure is lower than the preset threshold. The execution unit includes a turning gear start-locking module, a solenoid valve control module, and an indicator light module, which are electrically connected to the output of the PLC control unit. It is configured to cut off the turning gear motor start circuit, lock the turning gear solenoid valve, and trigger the low oil pressure indicator light when the sealing oil pressure is lower than a preset threshold.

[0006] Meanwhile, this solution also provides a protection method to prevent the large machine from starting with low sealing oil pressure, applied to the above-mentioned protection circuit, including the following steps: S1, real-time acquisition of pressure data from the sealing oil system; S2, compare the collected pressure data with the preset threshold; S3, if the pressure data is lower than the preset threshold, the turning gear start-lock control logic is triggered, the starting circuit of the turning gear motor is cut off, and the power supply circuit of the turning gear solenoid valve is cut off.

[0007] The principles and advantages of this scheme are: In existing technologies, sealing oil pressure monitoring mostly relies on independent pressure switches or personnel inspections, which has three major drawbacks. First, there is a lag in response; when the pressure is abnormal, personnel intervention is required to shut down the turning gear, which can easily lead to equipment damage due to operational delays. Second, there is a lack of logical linkage; the oil pressure protection and turning gear control lack hard-wired linkage and rely on software interlocking, making them susceptible to system interference. Third, there is insufficient status visualization; when the oil pressure is abnormal, there is no independent indication, making it difficult for maintenance personnel to locate the fault in a timely manner.

[0008] Traditional designs treat oil pressure monitoring and turning gear control as independent systems, neglecting the core triggering role of node circuits; and lacking integrated design of multi-module collaborative logic, resulting in fragmented protection functions, failing to consider the dynamic pressure fluctuation characteristics during the start-up and shutdown phases of large units, and simple threshold judgment is prone to malfunctions.

[0009] Therefore, this solution creatively uses the low sealing oil pressure node circuit as the core triggering unit, and directly connects the low sealing oil pressure node signal to the turning gear control circuit to form a hard logic of "pressure abnormality - node disconnection - circuit lockout". The response time is <100ms, which improves the response efficiency compared with traditional software interlocking and avoids protection failure caused by software faults.

[0010] The PLC control unit integrates three functions: interlock control logic, solenoid valve operation, and indicator light display, achieving integrated control of "pressure monitoring - logic judgment - action execution". When the oil pressure is lower than the preset threshold, it simultaneously cuts off the turning gear motor circuit, interlocks the solenoid valve operation, and turns off the indicator light, forming a three-dimensional protection network.

[0011] This solution achieves a technological leap from "passive monitoring" to "active defense" in sealing oil pressure protection by deeply integrating node circuits with PLC logic. Attached Figure Description

[0012] Figure 1 is a schematic diagram of the circuit structure of the low sealing oil pressure node loop in the protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to the present invention; Figure 1(a) is the overall diagram; Figure 1(b) and Figure 1(c) are partial views of Figure 1(a), respectively. Figure 2(a) shows the loop node of the PLC control unit in the turning gear control; Figure 2(b) shows the loop node of the PLC control unit in the solenoid valve action module; Figure 2(c) shows the loop node of the PLC control unit in the indicator light. Figure 3 This is a schematic diagram of the turning gear start-locking control logic in a protection circuit for preventing low sealing oil pressure during the start of a large machine turning gear according to the present invention. Figure 4 This is a schematic diagram of the solenoid valve operation logic in a protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to the present invention. Figure 5 This is a schematic diagram of the indicator light display logic in a protection circuit for preventing the turning gear of a large machine from starting with low sealing oil pressure, according to the present invention. Figure 6 This is a flowchart illustrating a protection method for preventing low sealing oil pressure during the start-up of a large machine turning gear according to the present invention. Detailed Implementation

[0013] The following detailed description illustrates the specific implementation method: This embodiment provides a protection circuit and method to prevent the turning gear from starting when the sealing oil pressure is low. The low sealing oil pressure node circuit is used as the core triggering unit, and the turning gear start interlocking control logic, solenoid valve action logic, and low oil pressure indicator display logic are integrated. When the oil pressure is lower than the preset threshold, the normally open node X017 is disconnected, triggering the interlocking protection to achieve active protection.

[0014] Option 1 A protection circuit is provided to prevent the starting of a large machine turning gear under low sealing oil pressure, including: The low-pressure sealing oil node circuit is set in the large machine turning gear control system. It is configured to monitor the sealing oil system pressure in real time and output a node switch signal as one of the conditions for starting the turning gear.

[0015] As shown in Figure 1, in this embodiment, the low-pressure sealing oil node circuit is directly connected to the PLC control unit via an electrical contact pressure gauge. The pressure gauge rapidly detects the pressure value in real time, with a detection range of 0-0.6 MPa and a preset threshold of 0.03 MPa. When the pressure falls below the 0.03 MPa threshold, a node switch signal is output to the PLC control unit.

[0016] The PLC control unit is electrically connected to the low-pressure sealing oil node circuit and integrates the turning gear start-lock control logic, solenoid valve action logic, and low-pressure indicator display logic. It receives node switch signals and determines whether the sealing oil pressure is below a preset threshold. In this embodiment, the PLC control unit can be configured with an FX2N-32MR analog input module (16 channels) to receive node circuit signals and communicate with the main monitoring system via an RS-232 serial interface, with a data update cycle of 100ms.

[0017] The PLC control unit includes a normally open X017 node, which remains open when the sealing oil pressure is lower than a preset threshold.

[0018] The execution unit includes a turning gear start-locking module, a solenoid valve control module, and an indicator light module, which are electrically connected to the output of the PLC control unit. It is configured to cut off the turning gear motor start circuit, lock the turning gear solenoid valve, and trigger the low oil pressure indicator light when the sealing oil pressure is lower than a preset threshold.

[0019] Specifically, see Figure 2(a) and Figure 2(a). Figure 3 As shown, the turning gear start interlock module includes a turning gear control circuit (M20 circuit). When the sealing oil pressure is lower than a preset threshold, the PLC control unit prevents the turning gear control circuit from outputting a start signal.

[0020] As shown in Figure 2(b) and Appendix Figure 4 As shown, the solenoid valve control module is configured to cut off the power supply circuit of the turning gear solenoid valve (Y000) when the sealing oil pressure is lower than the preset threshold, that is, its normally closed contact is opened, controlling the turning gear solenoid valve Y000 (AC220V, nominal diameter DN15).

[0021] As shown in Figure 2(c) and Appendix Figure 5 As shown, the indicator module includes a low sealing oil pressure indicator. When the sealing oil pressure is lower than a preset threshold, the indicator light turns off and a warning is issued simultaneously. In this embodiment, the indicator module includes an AD16-22D / S red indicator light (AC220V), which is installed on the control cabinet panel.

[0022] In this embodiment, the signal output path is as follows: the normally closed contact of the pressure gauge is used as a dry contact and directly connected to the X017 terminal of the PLC's digital input module, without the need for intermediate relays or analog-to-digital conversion. When the sealing oil pressure is lower than 0.03 MPa, the internal contact of the pressure gauge opens, outputting a digital signal to the PLC. The PLC determines whether the oil pressure is abnormal by detecting the on / off state of the X017 terminal, forming a "digital input interlock," simplifying the hardware link while maintaining response speed.

[0023] Option 2 In this embodiment, a protection method for preventing low sealing oil pressure during the start-up of the large machine turning gear is also provided, applied to the above-mentioned protection circuit, as shown in the attached figure. Figure 6 As shown, it includes the following steps: S1 collects pressure data from the sealing oil system in real time. Pressure data is read in real time via an electrical contact pressure gauge.

[0024] In this embodiment, a YX-150 type electric contact pressure gauge (measuring range 0-0.6MPa, accuracy ±0.5%FS) can be used, which is directly installed at the outlet of the sealing oil supply main pipe via an M20×1.5 thread. The normally closed contact of the pressure gauge serves as a dry contact and is directly connected to the X017 terminal of the PLC's digital input module. When the sealing oil pressure is below 0.03MPa, the internal contacts of the pressure gauge open, outputting a digital signal to the PLC.

[0025] The PLC processes the raw data using a filtering algorithm (first-order low-pass filter, time constant 0.5s) written in SCL language to eliminate interference from pipeline pressure fluctuations.

[0026] S2 compares the collected pressure data with a preset threshold, specifically a preset threshold of 0.03 MPa.

[0027] S3: If the pressure data is lower than the preset threshold, the turning gear start-lock control logic is triggered, cutting off the starting circuit of the turning gear motor and the power supply circuit of the turning gear solenoid valve, thus preventing the turning gear from moving mechanically. It also includes controlling the low sealing oil pressure indicator light to turn off and triggering an alarm.

[0028] In this embodiment, as shown in the appendix Figure 3 , 4 As shown in Figure 5, the control logic adopts ladder diagram programming, where the turning gear start interlock control logic, solenoid valve action logic, and oil pressure low indicator light display logic correspond to addresses M20, M86, and YO34, respectively.

[0029] Specifically, when the PLC detects that the oil pressure is ≤0.03MPa, the normally closed contact (terminal 3-4) opens, outputs a node switch signal, the PLC sets X017 (oil pressure low flag), and triggers the following interlocking actions: ① Set M20, cut off the output of Y002 to de-energize the KM2 contactor, and the turning gear motor is de-energized; ② Set M86, cut off the output of Y000 to de-energize and close the Y000 solenoid valve, and the turning gear disengages; ③ Set X017, cut off the output of Y034 to extinguish the indicator light and trigger an alarm.

[0030] It also includes S4, which releases the turning gear start-up interlock control logic when the pressure data recovers to above the preset threshold.

[0031] In this embodiment, a recovery mechanism is also provided. When the oil pressure recovers to 0.03MPa, the PLC automatically resets M20, M86, and YO34, restoring the normal state of each output channel. At the same time, the indicator lights up and the alarm stops.

[0032] In this embodiment, the low-pressure sealing oil node circuit is used as the core triggering unit. The PLC control unit integrates the logic for interlocking start, solenoid valve action, and indicator light display. Combined with the execution unit, it realizes the coordinated action of turning gear motor cut-off, solenoid valve interlocking, and status indication. This solves the problems of sealing tile wear and rotor thermal bending caused by starting the turning gear when the sealing oil pressure is low in the prior art, and realizes rapid response (≤200ms) and multi-dimensional protection from pressure abnormality to protection action.

[0033] This solution overcomes the shortcomings of traditional methods that rely on manual inspection or software interlocking, such as slow response, scattered logic, and weak anti-interference capabilities, by using hardware-level node loop interlocking, deep integration of PLC logic, and redundant design. This significantly improves system reliability and operation and maintenance efficiency.

[0034] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A protection circuit for preventing low sealing oil pressure during the start-up of a large locomotive, characterized in that, include: The low-pressure sealing oil node circuit is set in the large machine turning gear control system. It is configured to monitor the sealing oil system pressure in real time and output a node switch signal as one of the conditions for starting the turning gear. The PLC control unit is electrically connected to the low sealing oil pressure node circuit and integrates the turning gear start interlock control logic, solenoid valve action logic and low oil pressure indicator display logic. It is used to receive node switch signals and determine whether the sealing oil pressure is lower than the preset threshold. The execution unit includes a turning gear start-locking module, a solenoid valve control module, and an indicator light module, which are electrically connected to the output of the PLC control unit. It is configured to cut off the turning gear motor start circuit, lock the turning gear solenoid valve, and trigger the low oil pressure indicator light when the sealing oil pressure is lower than a preset threshold.

2. The protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 1, characterized in that: The low-pressure sealing oil circuit is connected to the PLC control unit via an electrical contact pressure gauge. The pressure value is detected in real time by the pressure gauge, with a detection range of 0-0.6MPa and a preset threshold of 0.03MPa.

3. The protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 1, characterized in that: The PLC control unit includes a normally open X017 node, which remains open when the sealing oil pressure is lower than a preset threshold.

4. The protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 1, characterized in that: The turning gear start-locking module includes a turning gear control circuit. When the sealing oil pressure is lower than a preset threshold, the PLC control unit controls the turning gear control circuit to prevent it from outputting a start signal.

5. The protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 1, characterized in that: The solenoid valve control module is configured to cut off the power supply circuit of the turning gear solenoid valve when the sealing oil pressure is lower than a preset threshold.

6. The protection circuit for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 1, characterized in that: The indicator module includes a low sealing oil pressure indicator light, which turns off when the sealing oil pressure is lower than a preset threshold.

7. A protection method for preventing low sealing oil pressure during the start-up of a large machine turning gear, characterized in that, The protection circuit applied to any one of claims 1-6 comprises the following steps: S1, real-time acquisition of pressure data from the sealing oil system; S2, compare the collected pressure data with the preset threshold; S3, if the pressure data is lower than the preset threshold, the turning gear start-lock control logic is triggered, the starting circuit of the turning gear motor is cut off, and the power supply circuit of the turning gear solenoid valve is cut off.

8. The protection method for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 7, characterized in that: S3 also includes a function to extinguish the low sealing oil pressure indicator light and trigger an alarm.

9. A protection method for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 7, characterized in that: In S1, pressure data is collected in real time via an electrical contact pressure gauge.

10. A protection method for preventing low sealing oil pressure during the start-up of a large machine turning gear according to claim 7, characterized in that: It also includes S4, which releases the turning gear start-up interlock control logic when the pressure data recovers to above the preset threshold.

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