The explosion-proof rating of industrial explosion-proof robots is determined based on the degree of danger in the explosive environment, the effectiveness of explosion-proof technical measures, and the safety performance of the equipment itself. This requires a comprehensive assessment based on international (such as IEC 60079) and domestic (such as GB 3836, GB 12476) standards. 

The core logic is: first, determine the type of hazardous environment (gas/dust) and the zone classification; then, select the applicable type of explosion-proof technology (such as flameproof, intrinsically safe, etc.); finally, refine the rating through parameters such as temperature class and protection level. 

The following details this process from four dimensions: environmental classification → explosion-proof technology type → key parameters (temperature class, protection level) → complete explosion-proof marking

I. Hazardous Environment Classification: Determining "where to use" 

The explosion-proof robot's explosion-proof rating first requires matching the type of explosive environment (gas or dust) and the hazardous area classification (Zone 0/Zone 1/Zone 2 or Zone 20/Zone 21/Zone 22) where it will be used. This is the basis for classifying the explosion-proof rating. 

1. Gaseous Explosive Environments 

refer to environments where flammable gases (such as methane, hydrogen, ethylene) or vapors (such as gasoline vapor) mixed with air may explode.  These are divided into 3 zones based on the frequency and duration of the explosive gas mixture: 

• Zone 0 (Gas Zone 0): Explosive gas mixtures are continuously or permanently present (e.g., inside sealed containers, near continuously leaking pipes); 

• Zone 1 (Gas Zone 1): Explosive gas mixtures may occur periodically or occasionally during normal operation (e.g., near pumps, valves); 

• Zone 2 (Gas Zone 2): Explosive gas mixtures do not occur during normal operation, and only exist for a short time under abnormal conditions (e.g., around storage tank areas). 

2. Dust explosive environments 

refer to environments where combustible dust (such as metal powder, coal dust, and plastic powder) is mixed with air and may cause an explosion.  These environments are divided into three zones based on the thickness and frequency of the dust layer: 

• Zone 20 (Dust Zone 20): Combustible dust is continuously or frequently present (e.g., inside dust containers, within pipes continuously conveying dust); 

• Zone 21 (Dust Zone 21): Combustible dust may appear periodically or occasionally during normal operation (e.g., near crushers and screening machines); 

• Zone 22 (Dust Zone 22): Combustible dust does not appear during normal operation, but only exists for a short time under abnormal conditions (e.g., around dust collection equipment).

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II. Types of Explosion-Proof Technology: 

Determining "How to Achieve Explosion Protection" Based on explosion-proof principles, industrial robot explosion-proof technologies can be classified into intrinsically safe, flameproof, increased safety, pressurized, and dust explosion-proof types (corresponding to the "Ex" marking in the standards). The explosion-proof capabilities of different technologies vary significantly and must be selected according to the environmental hazard level. The following are common types of explosion-proof technologies used in robots: 

1. Intrinsically Safe Type (Ex i) 

• Principle: By limiting the energy of the circuit (current, voltage, power), it ensures that even if electrical sparks or thermal effects occur, they cannot ignite the surrounding explosive gases or dust. 

• Features: Small size and light weight (suitable for flexible robot movement), but limited power (only suitable for low-power components such as sensors and small motors). 

• Sub-levels: 

• ia level: Can be used safely for a long time in Zone 0 (gas) or Zone 20 (dust) (failure probability ≤ 1×10⁻⁶/h); 

• ib level: Suitable for Zone 1 (gas) or Zone 21 (dust) (failure probability ≤ 1×10⁻⁵/h); 

• ic level: Only suitable for Zone 2 (gas) or Zone 22 (dust) (higher failure probability). 

2. Flameproof Type (Ex d) 

• Principle: The equipment casing is made of high-strength materials (such as cast steel, aluminum alloy) that can withstand the pressure of internal explosions (such as those caused by circuit short circuits) without damage, and the casing structure (such as the gap and length of the joint surfaces) is designed to prevent the internal explosion flame from spreading to the external environment. 

• Features: Strong explosion-proof capability (can withstand internal explosion pressure), but the casing is heavy (which may affect the robot's load and flexibility), suitable for high-power components (such as high-power motors and drivers). 

• Sub-levels: Determined according to the applicable gas group (e.g., IIC level is suitable for high-risk gases such as hydrogen) and temperature group (see below).

3. Increased Safety Type (Ex e) 

• Principle: Reduces the risk of ignition through optimized design (such as reducing temperature rise, strengthening insulation, and improving connection reliability), but needs to be used in conjunction with other explosion-proof technologies (such as flameproof or intrinsically safe types) and cannot be used as a stand-alone explosion-proof measure. 

• Applications: Commonly used in auxiliary components of robots (such as junction boxes, cable entry devices). 

4. Pressurized type (Ex p) 

• Principle: By filling the equipment enclosure with clean air or inert gas (such as nitrogen), the internal pressure is maintained higher than the external pressure, preventing explosive gases or dust from entering. 

• Features: Requires continuous gas supply (dependent on an external gas source), suitable for scenarios requiring frequent movement but high protection (such as inspection robots on chemical production lines), but the system is complex and costly. 

5. Dust explosion-proof type (Ex t) 

• Principle: Designed for dusty environments, it prevents dust ignition through enclosure protection (such as IP6X dustproof rating), surface temperature control (below the minimum ignition temperature of the dust), or special structures (such as anti-dust accumulation design). 

• Subdivisions: Divided into Ex tD A20, Ex tD A21, etc., according to the type of dust (combustible dust/conductive dust) and hazardous area (Zone 20/Zone 21/Zone 22).

III. Key Parameters: 

Refining "Explosion-proof Capability" In addition to the type of explosion-proof technology, the explosion-proof rating needs to be further refined through two key parameters: temperature class and protection level, to match the characteristics of explosive substances in the specific environment.

1. Temperature Class (T1-T6) 

Refers to the maximum allowable surface temperature of the equipment during normal operation or fault conditions, which must be lower than the minimum ignition temperature (autoignition point) of the surrounding explosive substances. The higher the temperature class, the lower the allowable surface temperature, and the stronger the explosion-proof capability. 

Temperature Group | Maximum Surface Temperature (°C) | Examples of Applicable Explosive Substances |

T1 | ≤450 | Hydrogen (H₂, autoignition temperature 585℃), Acetylene (C₂H₂, 305℃) | Lower temperature group required

T2 | ≤300 | Ethylene (C₂H₄, 425℃), Propane (C₃H₈, 450℃) |

T3 | ≤200 | Coal gas (main components CO, H₂, higher autoignition temperature) |

T4 | ≤135 | Gasoline (C₈H₁₈, 280℃), Benzene (555℃) |

T5 | ≤100 | Carbon disulfide (CS₂, 102℃) |

T6 | ≤85 | Ethyl nitrate (75℃), Hydrogen (T1 required, but T6 required in extreme scenarios) | 

Note: The robot must select the corresponding or lower temperature group based on the lowest ignition temperature of the explosive substances in the environment (e.g., if T4 group gases are present in the environment, the robot must be at least T4 or higher).

2. Protection Level (Gas/Dust Group): 

Further clarifies the scope of application of explosion-proof equipment for gas or dust environments: 

• Gas Environment Protection Level: 

• Class I: Only applicable to methane gas in coal mines (special scenarios, less relevant to robots); 

• Class II: Applicable to gases other than methane (e.g., IIA: propane; IIB: ethylene; IIC: hydrogen, acetylene), the higher the level (IIC > IIB > IIA), the higher the hazard of the applicable gas. 

• Dust Environment Protection Level: 

• Da level: Applicable to Zone 20 (continuous presence of combustible dust cloud); 

• Db level: Applicable to Zone 21 (occasional presence of dust cloud); 

• Dc level: Applicable to Zone 22 (very rare presence of dust cloud). 

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IV. Complete Explosion-Proof Mark: 

The final explosion-proof rating of the explosion-proof robot, combining "environment-technology-parameters," is intuitively represented by the explosion-proof mark. The mark must include information such as environment type, explosion-proof technology, gas/dust group, and temperature group. The following are typical examples: Example 

1: Explosion-proof robot for gaseous environments: 

Marking: Ex d IIC T4 Gb 

• Ex: Explosion-proof electrical equipment; 

• d: Flameproof explosion protection technology; 

• IIC: Suitable for Class II C gases (such as hydrogen, acetylene); 

• T4: Maximum surface temperature ≤ 135℃; 

• Gb: Protection level (suitable for Zone 1, failure probability ≤ 1×10⁻⁵/h). Example 

2: Explosion-proof robot for dusty environments: 

Marking: Ex tD A21 Db 

• Ex: Explosion-proof electrical equipment; 

• tD: Dust explosion-proof type (enclosure protection); 

• A: Dust type (Class A: combustible non-conductive dust, such as coal dust); 

• 21: Suitable for Zone 21 (dust clouds occur occasionally); 

• Db: Protection level (suitable for Zone 21, failure probability ≤ 1×10⁻⁵/h). 

Summary: How to choose the appropriate explosion-proof rating? 

The explosion-proof rating of industrial explosion-proof robots needs to be determined comprehensively based on the hazard level of the actual application environment (Zone 0/1/2 or Zone 20/21/22), the characteristics of the explosive substance (gas type/dust type, minimum ignition temperature), and the technical capabilities of the equipment itself (explosion-proof technology type, power requirements). For example: 

• In a Zone 1 environment with hydrogen (IIC class), an explosion-proof robot with Ex d IIC T4 Gb or higher explosion-proof rating should be selected; 

• In a Zone 21 environment with flour dust (IIIA class), a dust explosion-proof robot with Ex tD A21 Db should be selected.

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