Interlock control method of DCS interlock control system of screw vapor compressor

Abstract

This invention relates to the field of DCS interlocking control methods, and discloses an interlocking control method for a screw steam compressor's DCS interlocking control system. The method includes signal standardization and modularization of interlocking logic. The modularized interlocking logic includes: a start-up permission interlocking module, an operation monitoring interlocking module, an alarm and protection interlocking module, an emergency shutdown interlocking module, and a fault reset interlocking module. This invention standardizes the DCS access process, reducing communication costs and configuration error rates. The five interlocking modules in the modularized interlocking logic cover all operating conditions, improving the safety and stability of unit operation. The tiered alarm and tiered reset mechanisms are more in line with industrial safety standards.

Description

Technical Field

[0001] This invention relates to the field of DCS interlocking control methods, specifically to an interlocking control method for a screw steam compressor's DCS interlocking control system. Background Technology

[0002] In industrial production, screw steam compressors are key equipment widely used in processes such as steam compression and energy recovery. Their stable and reliable operation is crucial for ensuring the safety and efficiency of the entire production system. With the continuous improvement of industrial automation, the centralized control mode of the whole plant DCS (Distributed Control System) is gradually becoming the mainstream trend. More and more traditional screw steam compressor units are beginning to be connected to DCS systems to achieve more efficient and unified monitoring and management.

[0003] However, the integration of traditional screw steam compressor units into the plant's centralized DCS control system has revealed numerous problems, severely impacting the unit's operational efficiency and safety. Regarding control modes, traditional screw steam compressor units mostly employ independent local control, with each unit operating as its own system, lacking unified control logic and standards. When integrated into the plant's centralized DCS control system, differences in the original control methods and logic designs of different units lead to widespread non-standard interlocking logic. This presents a significant challenge in integrating the control logic of each unit into the DCS system, easily resulting in logical confusion, conflicts, and other problems, increasing the risk of system failure.

[0004] Regarding control drawings and signal definitions, the formats and contents of control drawings for different units vary, lacking a unified standard. Signal definitions are unclear; there are no clear specifications for key information such as the type, range, acquisition location, and control purpose of analog and digital signals. This poses significant difficulties for DCS system configuration, making it hard for configuration personnel to accurately understand the signal meanings, easily leading to configuration errors, low on-site integration efficiency, and impacting project progress.

[0005] The existing control scheme has significant shortcomings in fault handling and protection mechanisms. Fault classification is unscientific; it lacks clear distinctions and corresponding handling strategies for faults of different severity levels, making it impossible to respond to various faults in a timely and effective manner. The protection logic is incomplete; there are loopholes and unreasonable aspects in the monitoring of key parameters and the triggering of protection actions, making it difficult to ensure the safety of the unit under abnormal operating conditions. The reset mechanism lacks standardized design; the reset methods for general alarm faults and emergency shutdown faults are unclear, leading to a chaotic unit restart process after fault handling. This makes it impossible to guarantee that all conditions are met before the unit resumes normal operation, failing to meet the requirements for long-term safe, stable, and efficient operation of the unit.

[0006] To address the aforementioned issues, we propose an interlocking control method for the DCS interlocking control system of a screw steam compressor. Summary of the Invention

[0007] The purpose of this invention is to provide an interlocking control method for a DCS interlocking control system of a screw steam compressor, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an interlocking control method for a DCS interlocking control system of a screw steam compressor, comprising: Signal sorting and standardization; Modularization of interlocking logic; The interlocking logic modularization includes: The system includes a start-up permission interlocking module, an operation monitoring interlocking module, an alarm and protection interlocking module, an emergency stop interlocking module, and a fault reset interlocking module.

[0009] Preferably, the signal sorting and standardization includes: The analog and digital signals connected to the DCS by the generating units are uniformly sorted out, and the signal types, ranges, acquisition locations and control purposes are clarified to form a standardized I / O list.

[0010] Preferably, the start-up permission interlock module includes: Before starting the unit, a comprehensive assessment is made of the operating status, cooling water pressure, lubricating oil pressure, and inverter readiness status. Start-up is permitted when all conditions are met. Cooling water pressure ≥ 0.2 MPa; lubricating oil pressure ≥ 0.08 MPa.

[0011] Preferably, the operation monitoring interlocking module includes: Real-time monitoring of the unit's inlet steam temperature, outlet steam temperature, lubricating oil pressure, inlet oil temperature, cooling water pressure, inlet water temperature, return water temperature, high-pressure / low-pressure end return oil temperature, high-pressure / low-pressure end vibration, motor bearing temperature, motor A / B / C phase stator winding temperature, and inverter status. The inverter output frequency is adjusted according to the exhaust steam pressure to achieve closed-loop pressure control.

[0012] Preferably, the alarm and protection interlock module includes: graded monitoring and response to the unit's intake air temperature, exhaust steam temperature, lubricating oil pressure, cooling water pressure, return water temperature, high-pressure / low-pressure end vibration, sensor disconnection, and inverter status; The alarm and protection interlocking module shall immediately trigger an alarm when any of the following conditions are met: Steam inlet temperature ≥190℃; Exhaust steam temperature ≥230℃; Lubricating oil pressure < 0.08 MPa; Cooling water pressure < 0.2 MPa; Return water temperature ≥70℃; High-pressure end / low-pressure end oil return temperature ≥70℃; Vibration at the high-voltage end / low-voltage end ≥12mm / s; Motor bearing temperature ≥75℃; The stator winding temperature of motor phases A / B / C is ≥135℃.

[0013] Preferably, the emergency stop interlock module includes: controlling the DCS controller to immediately execute an emergency stop, cutting off the inverter output and interlocking the start; The emergency stop interlock module shall immediately perform a shutdown and lockout restart when any of the following conditions are met: Exhaust steam temperature ≥250℃; Lubricating oil pressure < 0.05 MPa; Cooling water pressure < 0.1 MPa; Return water temperature ≥ 80℃; High-pressure end / Low-pressure end oil return temperature ≥ 80℃; Vibration at the high-voltage end / low-voltage end ≥20mm / s; Motor bearing temperature ≥80℃; The stator winding temperature of motor phases A / B / C is ≥145℃; Inverter malfunction.

[0014] Preferably, the fault reset interlocking module includes: General alarm faults: Automatically reset after parameters return to normal, no manual operation required; Emergency shutdown failure: The system enters a fault lockout state and is prohibited from automatic restart. The lockout will only be released after the fault source is eliminated, all interlocking conditions are restored to normal, and the operator performs a manual reset at the DCS operator station. After the reset is completed, the system will re-verify the start-up permission conditions, and can only be restarted after passing the verification.

[0015] Preferably, the fault reset interlocking module further includes: Control logic standardization: unify the judgment rules and output logic for alarms, protection, shutdown, and reset, and clarify the delay, interlocking relationship and action flow; Complete the drawings and documents: Create standardized interlocking logic diagrams, signal lists, alarm lists, protection setting lists, and explanatory documents; Logic verification standardization: Performing integrity and security verification on control logic. Compared with the prior art, the beneficial effects of the present invention are: 1. Standardize the DCS access process to reduce communication costs and configuration error rate.

[0016] 2. The five interlocking modules in the interlocking logic modularization cover all operating conditions, improving the safety and stability of unit operation.

[0017] 3. The graded alarm and graded reset mechanism is more in line with industrial safety standards.

[0018] 4. It has strong versatility and can be applied to various screw steam compressor unit DCS control projects.

[0019] 5. Clear logic and standardized drawings significantly improve project delivery efficiency and quality. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides an interlocking control method for a DCS interlocking control system of a screw steam compressor. The DCS interlocking control system includes a DCS controller, a signal acquisition unit, an execution unit, and a human-machine interface unit. An interlocking control method is implemented based on the DCS interlocking control system, and the interlocking control method includes: Signal standardization: The analog and digital signals connected to the DCS by the generator unit are standardized, and the signal type, range, acquisition location and control purpose are clarified to form a standardized I / O list to ensure that the signals are complete, have unified definitions and are unambiguous.

[0022] The interlocking logic is modularized: the start-up permission interlocking module, the operation monitoring interlocking module, the alarm and protection interlocking module, the emergency stop interlocking module, and the fault reset interlocking module work together to achieve full-process safety control.

[0023] The start-up permission interlock module is used for pre-start condition verification of the unit, allowing start-up only when all safety conditions are met, and real-time acquisition of start-up commands, unit status, cooling water pressure, lubricating oil pressure, and inverter ready signals.

[0024] When the unit is in a shutdown state, the cooling water pressure is normal (cooling water pressure ≥ 0.2 MPa), the lubricating oil pressure is normal (lubricating oil pressure ≥ 0.08 MPa), and the frequency converter is ready, a start-up permission signal is output. It should be noted that if any of the above conditions are not met, the start-up is locked and a prompt message is given at the DCS operator station.

[0025] The permissible thresholds can be adjusted according to the unit model and operating conditions.

[0026] The operation monitoring and interlocking module is used for real-time monitoring and closed-loop regulation during normal operation of the unit. After the unit starts up, the operation monitoring and interlocking module controls the output frequency of the frequency converter of the DCS controller to regulate the speed of the steam compressor unit, thereby controlling the exhaust pressure and enabling the unit to enter a stable operating state.

[0027] The operation monitoring interlock module monitors the unit's inlet steam temperature, outlet steam temperature, lubricating oil pressure, inlet oil temperature, cooling water pressure, inlet water temperature, return water temperature, high-pressure / low-pressure end return oil temperature, high-pressure / low-pressure end vibration, motor bearing temperature, motor A / B / C phase stator winding temperature, and inverter status in real time. It adjusts the inverter frequency based on the outlet steam pressure to achieve closed-loop pressure control; it controls the desuperheating spray solenoid valve based on the outlet steam temperature to achieve temperature regulation; and it automatically engages the standby oil pump when the lubricating oil pressure is <0.08MPa and triggers an alarm for emergency shutdown when the lubricating oil pressure is <0.05MPa to ensure the stability of the lubrication system.

[0028] When the operating parameters exceed the limits, alarm, protection, or shutdown logic will be automatically triggered.

[0029] The normal operating logic of this invention is as follows: The steam inlet temperature is consistently below 190℃ and the steam outlet temperature is consistently below 230℃. The DCS controls the steam outlet temperature by spraying water onto the steam inlet through the desuperheating water spray solenoid valve. The steam outlet pressure is controlled by adjusting the speed of the steam compressor unit through the frequency converter, thus keeping the unit under rated operating conditions.

[0030] The lubricating oil pressure is consistently above 0.08 MPa and below the pump head pressure, the main pump continues to run, and the standby pump is in hot standby mode; the cooling water pressure is consistently above 0.2 MPa, ensuring the normal operation of the cooling water system.

[0031] The oil return temperature at the high-pressure end / low-pressure end is consistently below 70℃, and the vibration value at the high-pressure end / low-pressure end is consistently below 12mm / s.

[0032] The temperature of the front and rear bearings of the motor is consistently below 75℃, the temperature of the stator windings of phases A / B / C of the motor is consistently below 135℃, the frequency converter has no fault output, and the unit continues to operate stably.

[0033] The alarm and protection interlock module performs graded monitoring and response to the unit's intake air temperature, exhaust steam temperature, lubricating oil pressure, cooling water pressure, high-pressure / low-pressure end vibration, sensor disconnection, and inverter status.

[0034] The system is equipped with multiple alarm thresholds. Slight deviations in parameters from the threshold will trigger an alarm and prompt the operator to take action. When the parameter reaches a dangerous limit, the protection logic will be activated to prevent equipment damage.

[0035] For general alarm faults, the alarm will automatically clear once the parameters return to normal, and the unit can continue to operate.

[0036] First, let's explain some commonly used concepts in this field: HA: High Alarm. This means that when a parameter value reaches or exceeds a set high threshold, the system issues an alarm signal to alert the operator. However, it generally does not directly cause the equipment to shut down. The operator needs to check promptly and take appropriate measures to prevent the situation from worsening. For example, the inlet steam temperature ≥190℃ alarm (HA) is a high alarm issued when the inlet steam temperature reaches or exceeds 190℃.

[0037] HHS: High High Shutdown, a critical shutdown alarm, indicates that a parameter value has reached or exceeded a very high danger threshold. At this point, the equipment faces a serious risk of damage. The system will not only issue an alarm but also automatically execute an emergency shutdown operation to protect the equipment and personnel. For example, a critical fault shutdown (HHS) with an exhaust temperature ≥250℃ will automatically shut down the equipment when the exhaust temperature reaches or exceeds 250℃.

[0038] LA: Low Alarm. This refers to an alarm signal issued by the system when a parameter value drops to or below a set low threshold, prompting the operator to pay attention. Usually, the cause needs to be investigated and adjustments made, but immediate shutdown is not always necessary. For example, a lubricating oil pressure <0.08MPa alarm (LA) is issued when the lubricating oil pressure is below 0.08MPa.

[0039] LLS: Low Low Shutdown, also known as a critical shutdown low alarm, means that the parameter value has dropped to or below an extremely low dangerous threshold. Continued operation may lead to serious equipment failure or damage. The system will issue an alarm and automatically shut down. For example, the lubricating oil pressure <0.05MPa alarm emergency shutdown (LLS) means that the equipment will automatically shut down when the lubricating oil pressure is below 0.05MPa.

[0040] A: Alarm simply means alarm. It is triggered when there is a frequency converter failure, emergency stop signal, or other abnormal situation, to remind the operator that an abnormality has occurred.

[0041] S: Sequence, indicating that when a frequency converter malfunction or emergency stop signal occurs, not only will an alarm be triggered, but a series of chain reactions will also be triggered, ultimately leading to an emergency shutdown of the equipment to ensure system safety.

[0042] The specific alarm / cascading thresholds are as follows: Alarm when steam inlet temperature ≥190℃ (HA); Alarm when exhaust temperature ≥230℃ (HA); shutdown for serious fault when exhaust temperature ≥250℃ (HHS); When the lubricating oil pressure is <0.08MPa, an alarm (LA) is triggered and the standby pump is started; when the lubricating oil pressure is <0.05MPa, an emergency shutdown (LLS) is triggered. Alarm for oil inlet temperature ≥50℃ (HA); Alarm for cooling water pressure < 0.2 MPa (LA); Emergency shutdown for cooling water pressure < 0.1 MPa (LLS). Alarm for inlet water temperature ≥50℃ (HA); Alarm for return water temperature ≥70℃ (HA), emergency shutdown alarm for return water temperature ≥80℃ (HHS); Alarm for high-pressure / low-pressure oil return temperature ≥70℃ (HA), alarm for high-pressure / low-pressure oil return temperature ≥80℃ (HHS) for emergency shutdown. High-voltage / low-voltage side vibration ≥12mm / s alarm (HA), high-voltage / low-voltage side vibration ≥20mm / s alarm emergency shutdown (HHS); The motor bearing temperature is ≥75℃ alarm (HA), and the motor bearing temperature is ≥80℃ alarm emergency stop (HHS). Specifically, the motor bearing temperature of the present invention includes the front bearing of the motor and the rear bearing of the motor. Motor A-phase stator winding temperature ≥135℃ alarm (HA), motor A-phase stator winding temperature ≥145℃ alarm emergency shutdown (HHS); Motor B-phase stator winding temperature ≥135℃ alarm (HA), motor B-phase stator winding temperature ≥145℃ alarm emergency stop (HHS); Motor C-phase stator winding temperature ≥135℃ alarm (HA), motor C-phase stator winding temperature ≥145℃ alarm emergency shutdown (HHS); Inverter malfunction: Triggers alarm (A) and interlocks (S), alarm triggers emergency shutdown; Emergency stop signal: Triggers alarm (A) and interlocks (S), alarm and emergency stop (emergency stop button on control panel).

[0043] Execution logic under alarm conditions for each parameter: Steam inlet temperature ≥190℃ (HA): The DCS triggers an audible and visual alarm, prompting the operator to check the steam parameters of the pipeline network and take measures to reduce the steam inlet temperature to below 190℃. The alarm will then automatically clear, and the unit will continue to operate.

[0044] Exhaust steam temperature ≥230℃ (HA): DCS triggers audible and visual alarm, prompting operators to check the steam inlet water spray desuperheating system, cooling system and steam inlet conditions. If the temperature drops below 230℃, the alarm will automatically clear and the unit will continue to operate.

[0045] Lubricating oil pressure < 0.08MPa (LA): DCS triggers alarm and automatically activates standby oil pump. If the pressure recovers to above 0.08MPa, the alarm is automatically cleared and the unit continues to operate.

[0046] Oil inlet temperature ≥50℃ (HA): DCS triggers audible and visual alarm, prompting operators to check the oil cooler and lubrication system. If the temperature drops below 50℃, the alarm will automatically clear and the unit will continue to operate.

[0047] Cooling water pressure < 0.2MPa (LA): DCS triggers audible and visual alarm, prompting operators to check the cooling water pump or water supply system. If the pressure recovers to above 0.2MPa, the alarm will automatically clear and the unit will continue to operate.

[0048] Inlet water temperature ≥50℃ (HA): DCS triggers audible and visual alarm, prompting operators to check the cooling water source and heat exchanger condition. If the temperature drops below 50℃, the alarm will automatically clear and the unit will continue to operate.

[0049] Return water temperature ≥70℃ (HA): The DCS triggers an audible and visual alarm, prompting the operator to check the unit load and the unit's sealing condition. If the temperature drops below 70℃, the alarm will automatically clear, and the unit will continue to operate.

[0050] High-pressure / low-pressure end oil return temperature ≥70℃ (HA): DCS triggers audible and visual alarm, prompting operators to check the lubrication and cooling conditions of the high-pressure / low-pressure end bearings. If the temperature drops below 70℃, the alarm will automatically clear and the unit will continue to operate.

[0051] High-voltage / low-voltage vibration ≥12mm / s (HA): DCS triggers audible and visual alarm, prompting operators to check unit alignment, foundation tightness, and operating conditions. If the vibration drops below 12mm / s, the alarm will automatically clear, and the unit will continue to operate.

[0052] Motor bearing temperature ≥75℃ (HA): DCS triggers audible and visual alarm, prompting operators to check the lubrication of the front / rear bearings and the load condition of the motor. If the temperature drops below 75℃, the alarm will automatically clear and the unit will continue to operate.

[0053] When the stator winding temperature of motor phases A / B / C is ≥135℃ (HA): the DCS triggers an audible and visual alarm, prompting the operator to check the motor cooling system and load conditions. If the temperature drops below 135℃, the alarm will automatically be cleared and the unit will continue to operate.

[0054] Inverter fault (A / S): The DCS triggers an audible and visual alarm, prompting the operator to check the inverter status and power supply system. If the fault is cleared, the alarm will automatically clear, and the unit can continue to operate or be restarted as required.

[0055] The emergency stop interlock module is the ultimate protection measure under extreme operating conditions. When the following dangerous situations occur, the DCS controller will immediately execute an emergency stop, cut off the inverter output, and lock the start-up to ensure the safety of equipment and personnel: Exhaust steam temperature ≥250℃; Lubricating oil pressure < 0.05 MPa; Cooling water pressure < 0.1 MPa; Return water temperature ≥ 80℃; High-pressure end / low-pressure end oil return temperature ≥80℃; Vibration at the high-voltage end / low-voltage end ≥20mm / s; Motor bearing temperature ≥80℃; The stator winding temperature of motor phases A / B / C is ≥145℃; Inverter fault (TRUE); Emergency stop signal triggered (TRUE); Once an emergency shutdown is triggered, the unit is not allowed to restart automatically.

[0056] The execution logic for each parameter triggering an emergency stop: Exhaust steam temperature ≥250℃ (HHS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0057] Lubricating oil pressure < 0.05MPa (LLS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, stops oil pump, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the cooling water system supplies water to maintain water pressure and prevents unit seal temperature rise.

[0058] Cooling water pressure < 0.1MPa (LLS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0059] Return water temperature ≥80℃ (HHS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0060] High-pressure end oil return temperature ≥80℃ (HHS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0061] Low-pressure end oil return temperature ≥80℃ (HHS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0062] High-pressure end vibration ≥20mm / s (HHS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0063] Low-pressure end vibration ≥20mm / s (HHS): DCS immediately triggers emergency shutdown: cuts off inverter output, compressor unit stops, opens bypass regulating valve, triggers audible and visual alarm, locks start-up, and records fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent bearing and unit seal temperature rise.

[0064] If the motor front bearing temperature is ≥80℃ (HHS): the DCS will immediately trigger an emergency stop: disconnect the inverter output, stop the compressor unit, open the bypass regulating valve, trigger an audible and visual alarm, lock the start-up, and record the fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent the bearing and unit seals from overheating.

[0065] If the rear bearing temperature of the motor is ≥80℃ (HHS): The DCS will immediately trigger an emergency shutdown: cut off the inverter output, stop the compressor unit, open the bypass regulating valve, trigger an audible and visual alarm, lock the start-up, and record the fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent the bearing and unit seals from overheating.

[0066] If the stator winding temperature of motor phases A / B / C reaches ≥145℃ (HHS): the DCS will immediately trigger an emergency stop: disconnect the inverter output, stop the compressor unit, open the bypass regulating valve, trigger an audible and visual alarm, lock the start-up, and record the fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent the bearings and unit seals from overheating.

[0067] Inverter fault (TRUE): The DCS immediately triggers an emergency stop: simultaneously blocking the inverter output, stopping the compressor unit, opening the bypass regulating valve, triggering an audible and visual alarm, locking the start-up, and recording the fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent temperature rise in the bearings and unit seals.

[0068] Emergency stop signal trigger (TRUE): The DCS immediately triggers an emergency stop: disconnecting the inverter output, stopping the compressor unit, opening the bypass regulating valve, triggering an audible and visual alarm, locking the start-up, and recording the fault code. After shutdown, the oil pump and cooling water system must continue to operate to maintain oil and water pressure and prevent temperature rise in the bearings and unit seals.

[0069] It's important to explain that in the logic programming and signal processing of industrial control systems, "TRUE" and "FALSE" are a pair of basic logical values, similar to 1 and 0 in Boolean algebra. "TRUE" indicates that a condition is met, a signal is valid, or an event has occurred. When the system detects a fault in the frequency converter or receives an emergency stop signal, the corresponding detection module or input channel will determine the signal status as "TRUE," thus informing the control system that an abnormality has occurred and immediate action is required.

[0070] The fault reset interlocking module adopts a hierarchical reset mechanism, strictly adhering to the principle that alarms can be automatically restored, but shutdowns must be manually reset.

[0071] General alarm faults: Automatic reset after parameters return to normal, no manual operation required.

[0072] Emergency shutdown failure: The system enters a fault lockout state, and automatic restart is prohibited; the lockout will only be released after the fault source is eliminated, all interlocking conditions are restored to normal, and the operator performs a manual reset at the DCS operator station.

[0073] After the reset is complete, the system will re-verify the startup permission conditions, and can only be restarted if it passes the verification.

[0074] Control logic standardization includes unifying the judgment rules and output logic for alarms, protection, shutdown, and reset, clarifying delays, interlocking relationships, and action procedures, so that the entire logic can be directly configured and implemented in the DCS system.

[0075] Complete drawings and documents include creating standardized interlocking logic diagrams, signal lists, alarm lists, protection setting lists, and explanatory documents to facilitate design, configuration, commissioning, and delivery.

[0076] Logic verification standardization includes verifying the integrity and security of control logic to ensure that there are no logical defects, no protection gaps, and no risk of erroneous or failed operation.

[0077] Example 1: During the operation of the screw steam compressor, the inlet steam temperature is stable at 180℃. The DCS controls the desuperheating water spray solenoid valve to spray water onto the inlet, controlling the exhaust steam temperature, which is stable at 220℃. The frequency converter adjusts the speed of the steam compressor unit to control the exhaust steam pressure, keeping the unit under rated operating conditions. The lubricating oil pressure is stable at 0.25MPa, and lower than the head pressure of the oil pump. The main oil pump runs continuously, while the standby oil pump is in hot standby mode. The cooling water pressure is stable at 0.3MPa, ensuring the normal operation of the cooling water system. The high-pressure / low-pressure end return oil temperature is stable at 65℃, and the high-pressure / low-pressure end vibration value is stable at 7mm / s. The front and rear bearing temperatures of the motor are stable at 70℃, and the stator winding temperature of the motor's A / B / C phases is stable at 110℃. The frequency converter has no fault output, and the unit operates continuously and stably.

[0078] Example 2: During the operation of the screw steam compressor, the inlet steam temperature rose to 192℃, triggering an alarm (HA) for inlet steam temperature ≥190℃. The DCS activated an audible and visual alarm, prompting the operator to check the pipeline steam parameters. The operator took measures to lower the pipeline steam temperature, reducing the inlet steam temperature to 188℃. The alarm automatically cleared, and the unit continued normal operation. Simultaneously, during operation, the cooling water pressure dropped to 0.18MPa, triggering an alarm (LA) for cooling water pressure <0.2MPa. The DCS activated an audible and visual alarm, prompting the operator to check the cooling water pump or water supply system. The operator checked and repaired the faulty cooling water pump or water supply system, restoring the cooling water pressure to 0.22MPa. The alarm automatically cleared, and the unit continued stable operation.

[0079] Example 3: During operation, the exhaust steam temperature of the screw steam compressor rapidly increased to 252℃, triggering a severe shutdown due to an exhaust steam temperature ≥250℃ (HHS). The DCS immediately triggered an emergency shutdown: cutting off the inverter output, stopping the compressor unit, opening the bypass regulating valve, triggering audible and visual alarms, locking the start-up, and recording the fault code. After shutdown, the oil pump and cooling water system continued to operate to maintain oil and water pressure and prevent temperature rise in the bearings and unit seals. Operators discovered that a fault in the inlet steam spray desuperheating system was causing the excessively high exhaust steam temperature. After repairing the fault, a manual reset was performed at the DCS operator station, and the system re-verified the start-up permit conditions. After passing the verification, the unit restarted and resumed normal operation.

[0080] Example 4: During the operation of the screw steam compressor, the lubricating oil pressure suddenly dropped to 0.04 MPa. An emergency shutdown (LLS) alarm was triggered due to lubricating oil pressure <0.05 MPa. The DCS immediately triggered the emergency shutdown: disconnecting the inverter output, stopping the compressor unit, opening the bypass regulating valve, stopping the oil pump, triggering audible and visual alarms, locking the start-up, and recording the fault code. After shutdown, the cooling water system was maintained to prevent the unit's seal temperature from rising. Operators found that a leak in the lubricating oil pipeline caused the pressure drop. After repairing the leak and replenishing the lubricating oil, a manual reset was performed. The system verified the start-up permission conditions and the unit restarted and operated stably.

[0081] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

[0082] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An interlocking control method for a DCS interlocking control system of a screw steam compressor, characterized in that, include: Signal sorting and standardization; Modularization of interlocking logic; The interlocking logic modularization includes: The system includes a start-up permission interlocking module, an operation monitoring interlocking module, an alarm and protection interlocking module, an emergency stop interlocking module, and a fault reset interlocking module.

2. The interlocking control method for a DCS interlocking control system of a screw steam compressor according to claim 1, characterized in that, The signal sorting and standardization includes: The analog and digital signals connected to the DCS by the generating units are uniformly sorted out, and the signal types, ranges, acquisition locations and control purposes are clarified to form a standardized I / O list.

3. The DCS interlock control method for a screw steam compressor according to claim 1, characterized in that, The startup permission interlock module includes: Before starting the unit, a comprehensive assessment is made of the operating status, cooling water pressure, lubricating oil pressure, and inverter readiness status. Start-up is permitted when all conditions are met. Cooling water pressure ≥ 0.2 MPa; lubricating oil pressure ≥ 0.08 MPa.

4. The interlocking control method for a DCS interlocking control system of a screw steam compressor according to claim 1, characterized in that, The operation monitoring and interlocking module includes: Real-time monitoring of the unit's inlet steam temperature, outlet steam temperature, lubricating oil pressure, inlet oil temperature, cooling water pressure, inlet water temperature, return water temperature, high-pressure / low-pressure end return oil temperature, high-pressure / low-pressure end vibration, motor bearing temperature, motor A / B / C phase stator winding temperature, and inverter status. The inverter output frequency is adjusted according to the exhaust steam pressure to achieve closed-loop pressure control.

5. The interlocking control method for a DCS interlocking control system of a screw steam compressor according to claim 1, characterized in that, The alarm and protection interlock module includes: graded monitoring and response to the unit's intake air temperature, exhaust steam temperature, lubricating oil pressure, cooling water pressure, return water temperature, high-pressure / low-pressure end vibration, sensor disconnection, and inverter status; The alarm and protection interlocking module shall immediately trigger an alarm when any of the following conditions are met: Steam inlet temperature ≥190℃; Exhaust steam temperature ≥230℃; Lubricating oil pressure < 0.08 MPa; Cooling water pressure < 0.2 MPa; Return water temperature ≥70℃; High-pressure end / low-pressure end oil return temperature ≥70℃; Vibration at the high-voltage end / low-voltage end ≥12mm / s; Motor bearing temperature ≥75℃; The stator winding temperature of motor phases A / B / C is ≥135℃.

6. The interlocking control method for a DCS interlocking control system of a screw steam compressor according to claim 5, characterized in that, The emergency stop interlock module includes: controlling the DCS controller to immediately execute an emergency stop, cutting off the inverter output and interlocking the start; The emergency stop interlock module shall immediately perform a shutdown and lockout restart when any of the following conditions are met: Exhaust steam temperature ≥250℃; Lubricating oil pressure < 0.05 MPa; Cooling water pressure < 0.1 MPa; Return water temperature ≥ 80℃; High-pressure end / Low-pressure end oil return temperature ≥ 80℃; Vibration at the high-voltage end / low-voltage end ≥20mm / s; Motor bearing temperature ≥80℃; The stator winding temperature of motor phases A / B / C is ≥145℃; Inverter malfunction; Emergency stop signal triggered.

7. The interlocking control method for a DCS interlocking control system of a screw steam compressor according to claim 6, characterized in that, The fault reset interlocking module includes: General alarm faults: Automatically reset after parameters return to normal, no manual operation required; Emergency shutdown failure: The system enters a fault lockout state and is prohibited from automatic restart. The lockout will only be released after the fault source is eliminated, all interlocking conditions are restored to normal, and the operator performs a manual reset at the DCS operator station. After the reset is completed, the system will re-verify the start-up permission conditions, and can only be restarted after passing the verification.

8. The interlocking control method for a DCS interlocking control system of a screw steam compressor according to claim 7, characterized in that, The fault reset interlocking module also includes: Control logic standardization: unify the judgment rules and output logic for alarms, protection, shutdown, and reset, and clarify the delay, interlocking relationship and action flow; Complete the drawings and documents: Create standardized interlocking logic diagrams, signal lists, alarm lists, protection setting lists, and explanatory documents; Logic verification standardization: Perform integrity and security verification on control logic.