Key Points for Electrical and PLC Control Audit and Risk Control

I. Core Points for Third-Party Code Audit of Non-Standard Automation PLC Programs

The PLC program serves as the core control unit of non-standard automation equipment. The primary objective of third-party PLC code audit is to ensure the program features rigorous logic, stable operation, safe performance, and good maintainability—thereby preventing equipment malfunctions, safety incidents, or production downtime caused by program loopholes. Below are the specific audit points for non-standard automation PLC program audits:

1. Interlock Logic Audit for Non-Standard PLC

Interlock logic is the critical safeguard against mechanism misoperation, component collision, and equipment/personnel safety hazards in non-standard equipment. The audit of PLC interlock logic focuses on the following aspects:

• Mechanism Interlock: Audit the interlock logic between executive mechanisms (e.g., cylinders, servo motors, conveyor belts) of non-standard equipment to ensure that components with motion conflicts (e.g., telescopic cylinders and rotary motors) cannot act simultaneously. For instance, “The rotary motor shall be prohibited from starting if the cylinder fails to reset.” It is essential to verify the completeness of PLC logic instructions and the absence of missing interlock conditions for non-standard equipment.

• Matching of Electrical Interlock and Mechanical Interlock: Confirm that the electrical interlock (e.g., contactor auxiliary contact interlock) in the PLC program and the mechanical interlock (e.g., mechanical limit switches) of non-standard equipment form dual protection, eliminating risks associated with single interlock failure. Additionally, audit therationality of interlock release conditions, which must only be released after the equipment achieves a safe reset state.

• Redundant Interlock Verification: Check for redundant interlock design in non-standard PLC programs. For key mechanisms of non-standard equipment (e.g., heavy-duty hoisting, high-voltage operations), dual interlock logic must be implemented to prevent safety issues arising from single logic failure. Simultaneously, audit for potential interlock deadlock risks (e.g., mutual locking of two mechanisms leading to startup failure) in non-standard automation scenarios.

2. Emergency Stop Logic Audit for Non-Standard PLC

Emergency stop functions as the final safety barrier for non-standard equipment in emergency situations. The audit of PLC emergency stop logic must strictly comply with international safety standards and focus on the following details:

• Emergency Stop Trigger Range: Audit the linkage logic between hardware emergency stop buttons and the PLC program to ensure that all dangerous actions of non-standard equipment (e.g., motor operation, cylinder telescoping, high-voltage output) cease immediately without delay or omission when the emergency stop is triggered. It is strictly prohibited for “emergency stop to only halt part of the mechanisms” in non-standard automation equipment.

• Emergency Stop Reset Logic: Verify the rationality of the emergency stop reset method for non-standard PLC. A manual reset (rotational reset of the emergency stop button) must be implemented; the non-standard equipment shall not restart automatically after reset and must require a manual start command. Additionally, audit the presence of interlock conditions for emergency stop reset in the PLC program to prevent accidents caused by incorrect reset operations.

• Emergency Stop Signal Priority: Confirm that the emergency stop signal has the highest priority in the non-standard PLC program and is not interfered with by other commands (e.g., automatic mode, manual mode). Even if the program is in automatic operation, all outputs must be immediately cut off when the emergency stop is triggered. Meanwhile, the emergency stop trigger time and position (if multiple emergency stop buttons are installed) must be recorded for traceability.

3. Fault Record Logic Audit for Non-Standard PLC

Fault records serve as critical basis for maintenance and fault diagnosis of non-standard equipment. The audit of PLC fault record logic must ensure records are comprehensive, accurate, and traceable. Specific requirements for non-standard automation equipment are as follows:

• Full Coverage of Fault Types: Audit whether the non-standard PLC program can record all potential faults, including sensor faults (e.g., signal loss, excessive deviation), actuator faults (e.g., cylinder misalignment, motor overload), PLC internal faults (e.g., communication interruption, module alarm), and safety circuit faults (e.g., safety door not closed) of non-standard equipment.

• Completeness of Recorded Information: Fault records for non-standard equipment must include key information, at minimum: fault code, fault description, trigger time, trigger conditions, equipment operation status at fault occurrence, and fault reset time. Avoid “recording only the fault without specific trigger reasons” to facilitate subsequent troubleshooting of non-standard automation equipment.

• Fault Storage and Reading: Verify whether the fault records of non-standard PLC have a power-off preservation function to ensure no loss of fault records after equipment power-off. Simultaneously, audit theconvenience of fault reading methods—supporting query and export via the HMI interface or reading through PLC programming software. The record storage capacity must be able to retain at least the latest 100 faults for non-standard automation equipment.

4. Mode Switching Logic Audit for Non-Standard PLC

Non-standard equipment typically includes multiple operation modes, such as automatic, manual, debugging, and emergency stop. The rationality of PLC mode switching logic directly impacts the operational safety and stability of non-standard equipment. Audit points for non-standard automation PLC are as follows:

• Mode Switching Conditions: Audit whether clear conditions exist for switching between different modes of non-standard PLC. For example, “When switching from automatic mode to manual mode for non-standard equipment, the equipment must be in a stopped state with no fault alarms.” Direct mode switching during equipment operation is prohibited to avoid mechanism misoperation.

• Mode Status Feedback: Verify whether the non-standard PLC program can accurately feedback the current equipment operation mode, clearly displayed via the HMI interface. After mode switching, relevant output commands must be immediately adapted to the new mode (e.g., in manual mode, the actuator only responds to manual operation commands, with automatic commands rendered invalid).

• Mode Interlock Protection: Audit the interlock logic during mode switching of non-standard PLC. For example, “In the debugging mode of non-standard equipment, the safety circuit must remain effective, and the emergency stop button must be triggerable normally” to prevent safety protection failure after switching to debugging mode. Simultaneously, logic design that allows “automatic startup of non-standard equipment after mode switching” is prohibited.

5. Safety Door Logic Audit for Non-Standard PLC

The safety door is a key component for isolating thedangerous area of non-standard equipment and protecting operator safety. Its PLC logic audit must be combined with hardware (safety door switches) and the PLC program of non-standard equipment, focusing on the following:

• Safety Door Status Detection: Audit whether the non-standard PLC program can accurately detect the opening and closing status (closed/disconnected) of the safety door. The safety door switch used (e.g., travel switch, magnetic switch) must be a safety-level component for non-standard equipment. The program must include logic that “prohibits non-standard equipment startup if the safety door is not closed” and requires the equipment to immediately stop all dangerous actions when the safety door is opened during operation.

• Safety Door Bypass Logic (if any): If the non-standard equipment is designed with a safety door bypass function (for debugging and maintenance only), audit the rigor of the PLC bypass logic. The bypass must be protected by password authorization; after enabling the bypass, the non-standard equipment must issue an obvious sound and light alarm. Meanwhile, the bypass enable time and operator (if applicable) must be recorded. In the bypass state, the non-standard equipment may only perform low-speed, non-dangerous debugging operations.

• Fault Alarm Linkage: If thesafety door switch of non-standard equipment fails (e.g.,signal loss, poor contact), the PLC program must immediately trigger an alarm and prohibit equipment startup to avoid safety accidents caused by failure to detect the safety door status.

6. Alarm Mechanism Audit for Non-Standard PLC

The alarm mechanism serves as the early warning signal for non-standard equipment abnormalities. The audit of PLC alarm mechanisms must ensure alarms are timely, accurate, and identifiable, while facilitating rapid troubleshooting by operators. Specific points are as follows:

• Alarm Classification: Audit whether the alarms of non-standard PLC are classified by fault severity (e.g., emergency alarm,general alarm, prompt alarm). Emergency alarms (e.g., emergency stop trigger, safety circuit fault) for non-standard equipment must immediately cut off equipment operation with a sound and light alarm; general alarms (e.g., slight sensor deviation) may maintain equipment operation but must alert operators to pay attention.

• Alarm Feedback and Processing: Verify whether the alarm signal of non-standard PLC can be synchronously fed back to the HMI interface, displaying clear alarm descriptions, fault locations, and processing suggestions for non-standard equipment. Simultaneously, audit whether the alarm has a mute function (after muting, the sound and light alarm stops, but alarm information is retained). After the alarm is resolved, the program must automatically clear the alarm record (or allowmanual clearing) to avoid alarm accumulation in non-standard automation equipment.

• Alarm Redundancy: For key faults of non-standard equipment (e.g., motor overload, high-voltage leakage), dual alarm logic (e.g., PLC internal alarm + external sound and light alarm) must be implemented to ensure timely detection by operators. Additionally, audit the PLC alarm logic for false alarm and missing alarm risks—for example, slight sensor fluctuations should not trigger frequent alarms in non-standard automation equipment.

II. Key Risk Control Points for Non-Standard Equipment Safety Circuits

The safety circuit of non-standard equipment is the core system ensuring equipment safe operation and operator life safety. The focus of risk control for non-standard equipment safety circuits is “ redundant protection, closed-loop verification, and compliance with international standards.” Specific points for non-standard automation equipment are as follows:

1. Risk Control for Safety Relay Application in Non-Standard Equipment

Safety relays are the core control components of non-standard equipment safety circuits. Unlike ordinary relays, they possess fail-safe characteristics. Risk control for safety relay application in non-standard equipment focuses on the following:

• Compliance of Selection: Audit whether the selection of safety relays for non-standard equipment meets the equipment safety level requirements (e.g., EN ISO 13849 standard). Select safety relays with corresponding SIL levels based on the danger level of non-standard equipment; replacement of safety relays with ordinary relays in non-standard automation equipment is strictly prohibited.

• Wiring Specifications: Verify the correctness of safety relay wiring for non-standard equipment. Input signals (e.g., emergency stop, safety door) must be connected to the safety input terminal of the safety relay, and output signals must control the main power supply and dangerous action actuators of non-standard equipment—ensuring that the output circuit enters a safe state (e.g., power cutoff) when the safety relay fails.

• Redundant Design: For high-risk non-standard equipment (e.g., high-voltage, heavy-duty equipment), a dual safety relay redundant design must be adopted to ensure that the other relay can operate normally if one fails, avoiding safety circuit failure. Simultaneously, audit the self-inspection function of safety relays for non-standard equipment to ensure real-time fault detection and alarm triggering.

2. Safety Door Risk Control for Non-Standard Equipment

As a key component for isolating operator safety in non-standard equipment, safety door risk control must be combined with hardware selection, installation, and logic linkage of non-standard equipment, focusing on the following:

• Hardware Selection: Safety doors for non-standard equipment must comply with international safety standards and possess sufficient mechanical strength (capable of withstanding a certain impact force). Safety door switches must be safety-level (e.g., forced-break travel switches) for non-standard equipment; replacement withordinary switches is prohibited to avoid safety door status detection failure due to switch malfunction in non-standard automation equipment.

• Installation Requirements: Safety doors for non-standard equipment must be firmly installed and fully isolate the equipment’s dangerous area when closed. Gaps must comply with international safety specifications (to prevent operator limb access). Additionally, safety doors must be equipped withanti-misopening devices (e.g., door locks) to prevent accidental opening by operators.

• Logic Linkage Risk Control: As noted in the previous PLC program audit, ensure the safety door is linked with the non-standard equipment’s operation logic. Non-standard equipment is prohibited from starting if the safety door is not closed, and must stop immediately if the safety door is opened during operation. Simultaneously, regularly verify the sensitivity of safety door switches for non-standard equipment to avoid signal delay or loss.

3. Light Curtain Risk Control for Non-Standard Equipment

Light curtains are primarily used forpersonnel protection in dangerous areas of non-standard equipment (e.g., stamping, shearing areas). When an operator’s limb enters the dangerous area, the light curtain triggers a signal, and the non-standard equipment stops immediately. Risk control points for light curtains in non-standard equipment are as follows:

• Selection Adaptation: Based on the size and protection requirements of the non-standard equipment’s dangerous area, select an appropriate light curtain model (e.g., light curtain height, detection accuracy) to ensure full coverage of the dangerous area without protection blind spots. Simultaneously, the light curtain must possess anti-interference capabilities (e.g., anti-electromagnetic interference, anti-light interference) to avoid false triggering in non-standard automation equipment.

• Installation and Calibration: The installation position of light curtains for non-standard equipment must be reasonable, with the transmitting and receiving ends aligned and unobstructed. Installation height must comply with ergonomic requirements (to avoid failure to trigger when operators bend or reach). Regularly calibrate the detection accuracy of light curtains for non-standard equipment to ensure immediate signal triggering upon slight obstruction (e.g., finger entry).

• Fault Risk Control: Light curtains for non-standard equipment must have a fault self-inspection function. If the light curtain fails (e.g., transmitting/receiving end damage, signal interruption), it must immediately trigger non-standard equipment shutdown and issue an alarm. Operation of non-standard equipment with afaulty light curtain is prohibited. Simultaneously, audit the linkage logic between the light curtain and PLC program to ensure rapid, delay-free transmission of trigger signals to the PLC in non-standard automation equipment.

4. Emergency Stop Closed-Loop Verification for Non-Standard Equipment

Emergency stop closed-loop verification is a key link ensuring the effectiveness and reliability of the emergency stop function for non-standard equipment, avoiding the risk that “the emergency stop button is pressed but the non-standard equipment does not stop.” Risk control points for non-standard equipment are as follows:

• Signal Closed-Loop Design: After the emergency stop button of non-standard equipment is pressed, the PLC program must not only trigger emergency stop logic but also verify the effectiveness of the emergency stop via a feedback signal (e.g., auxiliary contact of the emergency stop button), forming a “press-trigger-feedback” closed loop. If no feedback signal is received (e.g., emergency stop button failure), the PLC must immediately trigger an alarm and cut off the non-standard equipment’s power supply.

• Regular Verification: Establish an emergency stop closed-loop verification process for non-standard equipment. Manually press the emergency stop button regularly (e.g., daily before startup, monthly) to check if the non-standard equipment stops immediately, if the feedback signal is normal, and if the alarm is triggered. Simultaneously,record verification results to avoid undetected emergency stop function failures in non-standard automation equipment.

• Redundant Verification: For key non-standard equipment, dual emergency stop closed-loop verification (e.g., emergency stop button feedback + equipment operation status feedback) can be implemented to ensure 100% effectiveness of the emergency stop function. Additionally, audit the closed-loop logic for loopholes such as “feedback signal loss but non-standard equipment still running.”

III. Key Points for Compliance Audit of Electrical Cabinet Design for Non-Standard Equipment

The electrical cabinet is the core carrier of the non-standard equipment’s electrical system. Its design compliance directly impacts theoperational stability, safety, and maintainability of non-standard equipment. The audit must comply withinternational electrical design standards (e.g., GB/T 5226.1, IEC 60204), focusing on the following aspects for non-standard automation equipment:

1. Grounding System Audit for Non-Standard Equipment Electrical Cabinet

• Compliance of Grounding Type: Non-standard equipment electrical cabinets must be equipped with protective grounding (PE wire) and working grounding (e.g., grounding for PLC and frequency converters). The two grounding types must be separately configured; sharing agrounding electrode is prohibited to avoid working grounding interfering with protective grounding and causing safety hazards in non-standard automation equipment.

• Grounding Resistance Compliance: The protective grounding resistance of non-standard equipment electrical cabinets must be ≤4Ω (adjusted based on equipment type). Audit the installation of grounding electrodes (e.g., grounding body depth, material) and the specifications of grounding wires (e.g., wire diameter, material) to ensure firm connection without looseness or oxidation, and clear grounding marks for non-standard equipment.

• Internal Grounding Specifications: Metal components inside non-standard equipment electrical cabinets (e.g., cabinet body, door, mounting plate) must be reliably grounded. Sensitive electronic components such as PLC and frequency converters must have separate grounding connections to the grounding bar, avoiding shared grounding wires with high-voltage equipment (e.g., contactors, relays) to reduce electromagnetic interference in non-standard automation equipment.

2. Wire Number Marking Audit for Non-Standard Equipment Electrical Cabinet

• Uniqueness of Wire Numbers: All wires in non-standard equipment electrical cabinets (power wires, signal wires, control wires) must be marked with unique wire numbers, consistent with the electrical schematic diagram. Duplicate or missing wire numbers are prohibited to facilitate subsequent maintenance and fault diagnosis of non-standard equipment.

• Specification of Wire Number Marking: Wire number marks for non-standard equipment electrical cabinets must be clearly visible (e.g., at both ends of wires, terminals). Marking methods must beunified (e.g., wire number tubes, labels), with clear, non-fading fonts. For longer wires, intermediate wire number marks must be added to avoid blurred or lost marks in non-standard automation equipment.

• Consistency between Wire Numbers and Schematic Diagram: Audit whether the wire numbers of non-standard equipment electrical cabinets are fully consistent with the electrical schematic diagram, including wire direction and terminal connections. This ensures operators can quickly locate corresponding lines based on wire numbers, avoiding wiring errors and difficulty in fault diagnosis caused by incorrect wire numbers in non-standard equipment.

3. Terminal Selection and Installation Audit for Non-Standard Equipment Electrical Cabinet

• Adaptation of Terminal Selection: Based on the wire diameter, current size, and purpose of non-standard equipment wires, select appropriate terminals (e.g., wiring terminals, terminal blocks). The rated current and voltage of terminals must exceed actual working values. Selection of terminals with insufficient rated parameters is prohibited to avoid terminal heating and burnout in non-standard automation equipment.

• Terminal Installation Specifications: Terminal blocks of non-standard equipment electrical cabinets must beinstalled neatly and firmly. Terminal spacing must comply with international specifications (to avoid short circuits). Wires must be tightly pressed when connected to terminals, without looseness or virtual connections. Simultaneously, terminals must be marked with corresponding wire numbers (consistent with wire marks). For terminals handling sensitive signals (e.g., PLC, sensors) in non-standard equipment, shielded terminals must be selected to reduce interference.

• Terminal Protection: Terminal blocks of non-standard equipment electrical cabinets must be equipped with protective covers (e.g., insulating protective covers) to prevent electric shock from accidental contact by operators, and to avoid dust and debris entering terminals and affectingcontact performance. Terminals prone to loosening must be regularly inspected and tightened in non-standard automation equipment.

4. Heat Dissipation Design Audit for Non-Standard Equipment Electrical Cabinet

• Adaptation of Heat Dissipation Method: Based on the heating power of equipment inside non-standard equipment electrical cabinets (e.g., frequency converters, contactors, PLC), select an appropriateheat dissipation method (e.g., natural heat dissipation, fan heat dissipation, air conditioning heat dissipation) to ensure the internal temperature of the electrical cabinet is controlled within the range allowed by non-standard equipment (typically 0-40℃), avoiding equipment failure due to overheating.

• Reasonable Heat Dissipation Layout: Heat-generating equipment in non-standard equipment electrical cabinets (e.g., frequency converters) must be installed in well-ventilated positions, avoiding close contact with sensitive electronic components (e.g., PLC). Simultaneously, wire layout must be reasonable to avoid blocking heat dissipation channels. Fans and air conditioners must be firmly installed with unobstructed air vents; dust must be regularly cleaned to ensure heat dissipation effectiveness in non-standard automation equipment.

• Temperature Monitoring: For non-standard equipment with high heating power, a temperature sensor must be installed in the electrical cabinet to monitor internal temperature in real time. When the temperature exceeds the threshold, an alarm is triggered to remind operators to inspect the heat dissipation system, avoiding equipment damage due to overheating in non-standard equipment.

5. Protection Level (IP) Audit for Non-Standard Equipment Electrical Cabinet

• Adaptation of Protection Level: Based on the service environment of non-standard equipment (e.g., workshop dust, humidity, corrosive gas), select an appropriate electrical cabinet protection level (e.g., IP54, IP65) to ensure the electrical cabinet effectively prevents dust, water, and corrosive substances from entering, protecting internal electrical components of non-standard equipment.

• Implementation of Protection Measures: Audit the sealing performance of non-standard equipment electrical cabinets. Cabinet doors, wire inlets, and wire outlets must use sealing strips and sealing joints to avoid dust and water leakage through gaps. Electrical cabinet doors must have a locking function to prevent unauthorized opening. Simultaneously, the cabinet surface must undergo anti-corrosion treatment (e.g., painting, galvanizing) to adapt to harsh environments in non-standard automation equipment.

• Protection Level Marking: The protection level must be clearly marked on the surface of non-standard equipment electrical cabinets, along with service environment requirements. This enables operators to understand the protection range of non-standard equipment and avoid using it in environments that do not meet protection requirements, which could damage the electrical cabinet.

IV. Key Risk Control Points for Sensor and Actuator Selection for Non-Standard Equipment

Sensors and actuators serve as the “sensing organs” and “executive components” of non-standard equipment. The rationality of their selection directly impacts the operational accuracy, stability, and service life of non-standard equipment. The core of risk control for sensor and actuator selection in non-standard equipment is “ adaptability, reliability, and maintainability.” Specific points are as follows:

1. Risk Control for Environmental Adaptability Selection of Non-Standard Equipment Sensors and Actuators

• Temperature Adaptability: Based on the service environment temperature of non-standard equipment (e.g., high-temperature workshops, low-temperature cold storage), select sensors and actuators that can adapt to the corresponding temperature range to avoid equipment damage and reduced measurement accuracy caused by extreme temperatures (e.g., high-temperature resistant sensors for high-temperature non-standard environments, low-temperature resistant cylinders for low-temperature non-standard equipment).

• Humidity and Dust Adaptability: For humid and dusty environments (e.g., food processing, mining non-standard equipment), select waterproof and dustproof sensors and actuators (e.g., IP65 and above protection level) to prevent water and dust from entering the equipment, causing short circuits and faults in non-standard automation equipment.

• Corrosive Environment Adaptability: If non-standard equipment is used in corrosive environments (e.g., chemical industry, electroplating), select sensors and actuators made of corrosion-resistant materials (e.g., stainless steel,corrosion-resistant plastic) to avoid equipment corrosion that affects service life and operational accuracy in non-standard equipment.

2. Risk Control for Redundant Selection of Non-Standard Equipment Sensors and Actuators

• Redundancy of Key Equipment: For core links of non-standard equipment (e.g., positioning, detection, safety protection), adopt aredundant selection design. For example, install two sensors (one main, one standby) at key positions of non-standard equipment; if the main sensor fails, the standby sensor is immediately activated to avoid equipment shutdown. Actuator redundancy (e.g., dual drive for key cylinders) ensures non-standard equipment can still operate normally (or stop safely) if a single actuator fails.

• Adaptation of Redundant Logic: Redundant selection of non-standard equipment sensors and actuators must be combined with the redundant logic of the PLC program to ensure rapid switching of standby equipment. Simultaneously, the time and reason for redundant switching must be recorded for subsequent maintenance of non-standard equipment. Signal conflicts between redundant and main equipment are prohibited to ensure smooth operation logic in non-standard automation equipment.

3.Risk Control for Replaceability Selection of Non-Standard Equipment Sensors and Actuators

• Standardized Selection: Prioritize the selection of standardized, general-purpose sensors and actuators for non-standard equipment, avoiding niche and customized products. This ensures replacement parts can be quickly procured when non-standard equipment fails, reducing downtime. Simultaneously, audit product versatility to ensure interchangeability of products of the same model from different manufacturers in non-standard automation equipment.

• Standardization of Interfaces: The interfaces of non-standard equipment sensors and actuators (e.g., signal interfaces, installation interfaces) must comply with international industry standards and be compatible with equipment such as PLC and HMI. This avoids replacement and linkage failures due to interface mismatch in non-standard equipment.

• Convenience of Replacement: When selecting sensors and actuators for non-standard equipment, consider replacement convenience. For example, sensors adopt plug-in installation, and actuators use standardized installation dimensions to avoid disassembling numerous components during replacement, improving maintenance efficiency in non-standard automation equipment.

4.Risk Control for Service Life Selection of Non-Standard Equipment Sensors and Actuators

• Service Life Adaptation: Based on the design service life and operation frequency of non-standard equipment, select sensors and actuators with matching service life. For example, actuators with high-frequency operation (e.g., cylinders) in non-standard equipment must be long-life and wear-resistant to avoid frequent replacement and reducemaintenance costs. The service life of sensors must exceed the design service life of non-standard equipment to ensure long-term stable operation.

• Audit of Service Life Parameters: Audit theservice life parameters of products (e.g., actuator action count, sensor detection count) to ensure they meet the operational requirements of non-standard equipment. Simultaneously, pay attention to product warranty periods and after-sales support to facilitate timely handling of service life issues in non-standard automation equipment.

• Adaptation of Maintenance Cycle: Combine the service life of non-standard equipment sensors and actuators to establish a reasonable maintenance cycle, conducting regular inspections, calibrations, and replacements to avoid faults caused byequipment aging. Simultaneously, audit product maintenance difficulty, prioritizing products with convenient maintenance and low costs for non-standard equipment.

V. Key Points forHMI Interface and Operation Logic Audit for Non-Standard Equipment

HMI (Human-Machine Interface) is the core carrier for operators to interact with non-standard equipment. The rationality of its interface design and operation logic directly impacts the operational efficiency and safety of non-standard equipment. The core of HMI audit for non-standard equipment is “ simplicity, intuition, misoperation prevention, and controllability.” Specific points are as follows:

1. Misoperation Prevention Audit for Non-Standard Equipment HMI

• Operation Authority Classification: The HMI interface of non-standard equipment must be configured with operation authority classification, such as administrator, operator, and maintenance personnel. Administrator authority is responsible for parameter setting and program modification; operator authority is limited to daily operation (e.g., startup, shutdown, mode switching); maintenance personnel authority is for fault diagnosis and maintenance operations. Authority management must adopt password verification to prevent unauthorized operation and parameter modification, avoiding equipment malfunctions or safety incidents.

• Key Operation Confirmation Mechanism: For key operations of non-standard equipment (e.g., parameter modification, program download, emergency reset), a double-confirmation mechanism must be set on the HMI interface. For example, after clicking the “parameter modification” button, the HMI must pop up a confirmation window to prompt the operator to confirm the operation again. This prevents misoperation caused by accidental touch, avoiding abnormal operation of non-standard equipment or damage to components.

• Invalid Operation Shielding: The HMI interface of non-standard equipment must shield invalid operations under specific working conditions. For example, when the non-standard equipment is in automatic operation mode, the HMI must gray out and disablemanual operation buttons (e.g., single-step cylinder control) to preventmanual operation from interfering with automatic operation logic and causing mechanism collision or equipment failure.

2. Interface Layout and Information Display Audit for Non-Standard Equipment HMI

• Reasonableness of Layout: The HMI interface layout of non-standard equipment must be concise and intuitive, with key functional modules (e.g., operation mode selection, running status display, alarm information) placed in prominent positions (e.g., upper left or middle of the interface). The layout must comply with the operation habits of operators, avoiding frequent page switching and improving operation efficiency. Functional modules of the same type (e.g., parameter setting, fault query) must be classified and integrated to facilitate operator retrieval.

• Clarity of Information Display: The HMI interface must clearly display the real-time running status of non-standard equipment, including operation mode, running speed, mechanism position, and input/output signal status. The display font must be clear and appropriately sized, with obvious color distinction (e.g., green for normal operation, red for fault alarm, yellow for standby status) to facilitate operators to quickly identify the equipment status. Avoid excessive information display on a single page to prevent information confusion.

• Real-Time Performance of Data: The HMI interface of non-standard equipment must display real-time data (e.g., sensor detection values, frequency converter output frequency, cylinder pressure) with a data refresh cycle not exceeding 1 second. This ensures operators can timely grasp the equipment running status and discover abnormal data in a timely manner. Simultaneously, the data display must be accurate, avoiding data distortion or delay caused by communication faults between HMI and PLC.

3. Fault Prompt and Troubleshooting Guidance Audit for Non-Standard Equipment HMI

• Clarity of Fault Prompt: When non-standard equipment fails, the HMI interface must immediately pop up an alarm prompt, clearly displaying the fault code, fault description, andfault occurrence time. The alarm prompt must be eye-catching (e.g., red background flashing, sound prompt) to attract the operator’s attention. At the same time, the fault information must be retained on the interface until the fault is resolved to avoid fault information loss.

• Provision of Troubleshooting Guidance: The HMI interface of non-standard equipment must provide simple and operable troubleshooting guidance for common faults