JB/T 5898-2015 Explosion-Proof Crane Standard Guide
Explosion Protection Classes and Classifications
Kelude Heavy Industry manufactures its explosion-proof cranes in strict compliance with national standards, offering a full range of both overhead and gantry explosion-proof crane models. Under these standards, explosion-proof cranes are classified by their protection method into four types: Flameproof (Exd), Increased Safety (Exe), Intrinsic Safety (Exi), and Pressurized Enclosure (Exp).
The appropriate explosion protection class is selected based on the classification of the explosive gas or dust present at the installation site (Group IIA, IIB, or IIC) and the temperature class (T1 through T6). The standards require that the complete crane's explosion-proof performance be certified by a nationally authorized inspection body, and the Explosion Proof Certificate must be obtained before the crane can be manufactured and sold. Cranes with different explosion protection classes must never be used in locations that fall outside the scope of their certification.
The core design principle for explosion-proof cranes is to eliminate or suppress any potential ignition source that could ignite the surrounding explosive atmosphere. The primary ignition sources include electrical sparks, friction sparks, electrostatic discharge, and hot surfaces. The standards specify concrete control measures for each of these sources: electrical equipment must be of an explosion-proof type, moving parts must be designed to prevent friction sparks, the earthing system must reliably dissipate static charges, and the temperature rise of every component must remain within the limits permitted for the corresponding temperature class.
The standards also define the operating environment for explosion-proof cranes. The standard ambient temperature range is generally -20°C to +40°C; any operation outside this range must be agreed upon between the manufacturer and the user. When an explosion-proof crane is used in an atmosphere containing explosive gas mixtures, the temperature class of the gas mixture must not exceed the temperature class indicated on the crane's nameplate.
For example, a crane certified for Temperature Class T4 (≤135°C) cannot be used in an environment classified as T3 (≤200°C). The standards also require that explosion-proof cranes be equipped with temperature protection devices that automatically shut off the power supply when the motor winding temperature exceeds the allowable limit. Maintenance management requirements stipulate that the user unit must maintain a dedicated maintenance record for each explosion-proof crane, documenting the condition of flameproof joints, insulation resistance values, and grounding resistance values at every inspection.
The Explosion Proof Certificate must be kept safe and must not be lost; once its validity period expires, re-certification must be applied for. Overhaul of an explosion-proof crane must only be carried out by a unit qualified for explosion-proof maintenance. The standards emphasize that any replacement of explosion-proof components must use genuine spare parts of the same grade and specification supplied by the original manufacturer—substitutes could compromise the entire crane's explosion-proof integrity.
Explosion-Proof Construction and Electrical Requirements
Key requirements for the explosion-proof construction include flameproof joint parameters (joint width ≥25mm for Group I / ≥15mm for Group II, surface roughness Ra≤3.2μm), electrostatic protection (grounding resistance ≤4Ω), and cable entry (must use Exd-type explosion-proof sealing glands). Flameproof joints must be free from corrosion and scratches, and coated with 204-1 anti-rust oil before assembly.
Flameproof bolts must be fitted with locking devices, and the flameproof gap must be ≤0.2mm (Group I) or ≤0.3mm (Group II). Moving parts are made of copper-based alloys or use explosion-proof crane wheels to minimize spark generation, while the hook is manufactured from beryllium bronze or aluminum bronze for explosion-proof performance. The wire rope is a rust-resistant galvanized wire rope. For the electrical system, the motor must be an explosion-proof motor (ExdⅡBT4 or ExdⅡCT4) with a Protection Rating of at least IP55.
The control box is of the flameproof type, and cable entries use explosion-proof sealing glands. The conductor rail system uses enclosed conductor rails or copper busbars. All electrical connections must be made inside explosion-proof junction boxes. The earthing system must be reliable, with a grounding wire cross-section of at least 4mm². When replacing explosion-proof components, only genuine spare parts with the same explosion protection class must be used.
| Explosion Protection Class | Applicable Area | Gas Classification | Typical Location |
|---|---|---|---|
| ExdⅡBT4 | 1Zone/2Zone | ⅡBGroup | Petrochemical Refining/Pharmaceutical |
| ExdⅡCT4 | 1Zone/2Zone | ⅡCGroup | Chemical Industry/Hydrogen |
| ExeⅡT4 | 2Zone | ⅡA~ⅡC | General Explosion-proof |
| DIP A21 | 21/22Zone | Dust | Coal Dust/Flour Dust |
Inspection & Maintenance Requirements
Explosion-proof electrical equipment must undergo a flameproof joint inspection every six months—free from corrosion, scratches, or impact damage. Insulation resistance is to be measured semi-annually and must remain ≥1MΩ. Grounding resistance must be checked every six months and stay ≤4Ω. A load test is required annually (1.25 times the rated load held for 10 minutes). Once the Explosion Proof Certificate expires, re-certification is mandatory. Replacement parts must be original components from the same manufacturer with an identical Explosion Protection Class. Before assembly, apply 204-1 anti-rust oil to flameproof joints.
The standard also specifies nameplate marking requirements for explosion-proof cranes—the nameplate must indicate the Explosion Proof Marking, Explosion Proof Certificate number, applicable area, and Temperature Class. Cranes with different explosion protection classes must not be used in locations beyond their certified scope—for instance, an ExdⅡBT4-rated crane cannot be used in Class ⅡC areas containing hydrogen or acetylene. The manufacturer must clearly state in the product manual the hazardous area classification and operating restrictions corresponding to each Explosion Protection Class.
Kelude Heavy Industry provides explosion-proof crane supporting services in accordance with the standard.
| inspection items | technical requirements | Interval | Standard |
|---|---|---|---|
| Flameproof Joint | Ra≤3.2μm | Semi-annual | §5.2 |
| Insulation Resistance | ≥1MΩ | Semi-annual | §5.3 |
| Grounding Resistance | ≤4Ω | Semi-annual | §5.4 |
| Load test | 1.25Times×10min | Annual | §6.2 |
| brake test | Lowering Drift≤100mm | Monthly | §6.3 |
Explosion-Proof Crane FAQ: Key Differences & Requirements
Q: What are the core differences between an explosion-proof crane and a standard crane?
A: An explosion-proof crane incorporates protective measures in its structural design, electrical system, and safety protection. This includes explosion-proof electrical equipment (types Exd, Exe, Exp, etc.), moving parts designed to prevent friction sparks, a reliable earthing system (grounding resistance ≤4Ω), and complete static electricity dissipation devices. The explosion protection class is selected based on the classification of the explosive gas/dust present and the temperature class of the operating environment.
Q: What are the specific requirements for the electrical system of an explosion-proof crane?
A: All electrical equipment must hold a valid Explosion Proof Certificate. Cables must enter through flameproof sealing joints. The conductor rail system must be an enclosed type with IP55 Protection. Motors must be explosion-proof, typically rated ExdⅡBT4 or ExdⅡCT4. The control box must be flameproof. All electrical connections must be made within explosion-proof junction boxes.
Q: How are moving parts protected on an explosion-proof crane?
A: Crane wheels and rails use copper-based alloys to minimize friction sparks. Brakes are fitted with non-sparking friction materials. Hooks are made from beryllium copper or aluminum bronze for explosion-proof performance. Wire ropes and pulleys are designed to avoid high-speed friction. The hoisting and travel mechanisms are equipped with overspeed protection.
Q: What is the recommended inspection interval for explosion-proof cranes?
A: Explosion-proof electrical equipment should undergo inspection of flameproof joints, insulation resistance, and grounding resistance every six months. The complete crane requires a specialized explosion-proof performance inspection annually. The Explosion Proof Certificate must be renewed upon expiration. Replacement parts must be original components of the same grade from the manufacturer.
