Explosion-Proof Bridge Crane Models & Explosion Protection Classes
Key Points Explosion-proof bridge cranes (QB/QBZ types) are designed and manufactured to the GB/T 3836 series of standards, covering three mainstream explosion protection classes: Ex dⅡBT4, Ex dⅡCT4, and Ex tD A21 IP65. With a lifting capacity of 1–100 t and spans of 7–35 m, they are suitable for gas explosion hazard zones 1 and 2, as well as dust explosion hazard zones 21 and 22. Pricing is approximately 1.5 to 2 times that of a standard bridge crane of the same tonnage; a 5 t Ex dⅡBT4 model typically costs around $15,000–$30,000. These cranes must carry the explosion-proof CCC certification (CCC Ex) and are subject to special equipment regulatory oversight.
Explosion-proof bridge cranes are mission-critical equipment in petrochemical, coal chemical, fine chemical, pharmaceutical, and grain processing industries. In explosive gas or dust atmospheres, a crane that fails to meet explosion-proof requirements can become an ignition source with catastrophic consequences. This article provides a systematic overview of the complete model parameters for the QB/QBZ series explosion-proof bridge cranes, a technical comparison of the three explosion protection classes, application scenarios, and price ranges—along with a full operation guide covering hazardous area classification through equipment selection.
QB/QBZ Series Model Parameter Comparison Table
The QB type is the standard explosion-proof bridge crane, while the QBZ type is a dual-purpose explosion-proof and metallurgical crane featuring an additional thermal insulation layer. The table below outlines the technical parameters across the full range of tonnages:
| Parameter | QB Type (Standard) | QBZ Type (Metallurgical) |
|---|---|---|
| Lifting Capacity | 1–100 t | 1–100 t |
| Span | 7–35 m | 7–35 m |
| Explosion Protection Class | Ex dⅡBT4 / Ex dⅡCT4 / Ex t D A21 IP65 | Ex dⅡBT4 / Ex dⅡCT4 / Ex t D A21 IP65 |
| Thermal Protection | Not available | Thermal insulation layer |
| Applicable Hazardous Areas | Gas: Zones 1, 2; Dust: Zones 21, 22 | Gas: Zones 1, 2; Dust: Zones 21, 22 |
| Design & Manufacturing Standard | GB/T 3836 series (ISO equivalent) | GB/T 3836 series (ISO equivalent) |
| Model | Lifting Capacity(t) | Span(m) | Lifting Height(m) | Lifting Speed(m/min) | Travel Speed(m/min) | Work Duty / Classification | Explosion Protection Class |
|---|---|---|---|---|---|---|---|
| QB1 | 1 | 7~16 | 6~18 | 8 | 20 | A3~A5 | Ex dⅡBT4 |
| QB3 | 3 | 7~22.5 | 6~18 | 8 | 20 | A3~A5 | Ex dⅡBT4 |
| QB5 | 5 | 7~22.5 | 6~18 | 8 | 20 | A3~A5 | Ex dⅡBT4 |
| QB10 | 10 | 7~28.5 | 6~18 | 7 | 20 | A4~A6 | Ex dⅡCT4/Ex dⅡBT4 |
| QB16 | 16 | 10~31.5 | 6~16 | 7 | 20 | A4~A6 | Ex dⅡCT4/Ex dⅡBT4 |
| QB20 | 20 | 10~31.5 | 6~16 | 5 | 15 | A4~A6 | Ex dⅡCT4/Ex dⅡBT4 |
| QB32 | 32 | 10~31.5 | 6~16 | 5 | 15 | A5~A6 | Ex dⅡCT4/Ex t D A21 |
| QB50 | 50 | 10~31.5 | 6~16 | 3~5 | 15 | A5~A6 | Ex dⅡCT4/Ex t D A21 |
| QB75 | 75 | 12~35 | 6~14 | 2.5~3.5 | 10 | A5~A6 | Ex dⅡCT4/Ex t D A21 |
| QB100 | 100 | 12~35 | 6~14 | 2.5 | 10 | A5~A6 | Ex dⅡCT4/Ex t D A21 |
The above covers the standard QB series. The QBZ Type (dual-purpose explosion-proof and metallurgical) builds on the QB design by adding a thermal insulation layer to the main girder and high-temperature-resistant electrical components. It is applicable to operating conditions where explosive gases and high-temperature radiation coexist, such as coal chemical coking workshops. At the same tonnage, the QBZ Type is priced 15–25% higher than the QB Type. Kelude's full range of explosion-proof bridge cranes comes standard with explosion-proof 3C Certification and Type Test Reports.
Explosion Protection Class Technical Parameters Explained
Explosion-proof overhead cranes are designed and manufactured in accordance with GB/T 3836.1–.15 (2021 edition, superseding the previous GB 3836 series) and AQ 1021, the standard for explosion-proof diesel engines used in coal mine working faces. Below is a comparison of the protection principles and technical parameters across the three mainstream explosion protection classes:
| comparison Item | Ex dⅡBT4 | Ex dⅡCT4 | Ex t D A21 IP65 |
|---|---|---|---|
| guards Principle | Flameproof——Explosion-pressure containment, Flame path isolation | Flameproof——Higher Strength Enclosure+Wide gapflameproof joint | Pressurization+Dustproof——Enclosure Sealing Dust ingress prevention |
| Applicable todanger zone | 1Zone,2Zone(Gas) | 1Zone,2Zone(Gas) | 21Zone,22Zone(Dust) |
| Gas Group | IIBClass(Ethylene, Propane, etc.) | IICClass(Hydrogen, Acetylene, etc.) | Not applicable to gas atmospheres |
| Temperature Class | T4(Maximum surface temperature≤135°C) | T4(Maximum surface temperature≤135°C) | T85°C~T135°C(Dependent on dust layer) |
| Protection Rating (IP) | IP54 | IP55 | IP65 |
| Motorrequirements | Flameproofexplosion-proof motor | IICClass flameproof Motor(Cast Steel Enclosure) | Dustexplosion-proof motor(IP65Enclosure) |
| wheel material | Copperalloy anti-static wheel | Copperalloy anti-static wheel | Steel wheel+anti-static grounding Belt |
| Typical industries | Petrochemical, Pharmaceutical | Coal chemical, Hydrogen energy, Oil refining | Flour, Coal dust, Aluminum dust, Plastic |
| Price increase | +40~60% | +50~80% | +45~70% |
These three explosion protection classes are not interchangeable. When both gas and dust explosion hazards exist at the site—such as in the coking workshop of a coal chemical plant—a dual-certified explosion-proof crane with both gas and dust explosion-proof certifications is required. For example, the QB model with Ex dⅡCT4 + Ex tD A21 dual-certification configuration. Kelude Heavy Industry offers integrated solutions with combined dual explosion-proof certifications.
1~100t Lifting Capacity Range | Ex dⅡBT4~CT4 Gas Explosion Protection Class | Ex t D A21 Dust Explosion Protection Class | IP54~65 Protection Rating (IP) | CCC Ex Explosion-proof3CCertification | +40~80% Price increase |
Explosion Protection Classes and Their Application Scenarios
Ex dⅡBT4 — The workhorse for petrochemical plants. This protection class is suitable for production workshops and storage areas handling IIB-class explosive gases such as ethylene, propane, benzene, methanol, ethanol, and acetone. Typical applications include FCC units in refineries, petrochemical synthesis workshops, pharmaceutical intermediate production facilities, and paint and solvent warehouses. In these environments, Ex dⅡBT4 offers the most cost-effective explosion protection and covers over 90% of explosion-proof requirements in the petrochemical industry.
Ex dⅡCT4 — The premium choice for hydrogen and coal chemical applications. IIC-class gases include highly flammable substances such as hydrogen (with a minimum ignition energy of only 0.019 mJ), acetylene, and carbon disulfide. The flameproof enclosure of Ex dⅡCT4 equipment must withstand significantly higher explosion pressures (reference pressure is 1.5 to 2 times that of IIB), with narrower flameproof joints and thicker wall sections. Typical scenarios include coking workshops in coal chemical plants (where hydrogen and carbon monoxide are present), electrolytic hydrogen production facilities, and hydrogen chloride synthesis sections in chlor-alkali plants. For more technical details on cranes under special working conditions, refer to Overhead Crane for Metallurgic Plants: Model Parameters, Pricing, and Selection Guide by Tonnage.
Ex tD A21 IP65 — Essential for dust explosion protection. Combustible dust explosions can be just as devastating as gas explosions. The 2014 Kunshan Zhongrong metal dust explosion (75 fatalities) is a stark example of an aluminum dust explosion. The core of a dust explosion-proof crane lies in electrical equipment with a Protection Rating of at least IP65, combined with anti-static grounding and surface temperature control (temperature limits for dust layers are stricter than for gases due to slower heat dissipation). Typical applications include flour milling workshops, pulverized coal preparation systems, aluminum/magnesium powder processing facilities, and plastic powder and coating powder workshops.
Reference Price Ranges and Selection Recommendations by Tonnage
The following reference price ranges apply to explosion-proof overhead cranes by tonnage, based on the Ex dⅡBT4 configuration. Upgrading to Ex dⅡCT4 adds 15–20%, while upgrading to Ex tD A21 IP65 adds 10–15%:
| tonnage(t) | Standard Span(m) | Ex dⅡBT4(10,000 CNY) | Ex dⅡCT4(10,000 CNY) | Ex t D A21(10,000 CNY) | QBZExplosion-proofmetallurgical(10,000 CNY) |
|---|---|---|---|---|---|
| 5 | 7~22.5 | 10~20 | 12~25 | 11~22 | 12~28 |
| 10 | 7~28.5 | 20~35 | 25~42 | 22~38 | 28~48 |
| 20 | 10~31.5 | 35~55 | 42~65 | 38~60 | 48~75 |
| 32 | 10~31.5 | 50~85 | 60~100 | 55~95 | 68~115 |
| 50 | 10~31.5 | 75~130 | 90~155 | 82~145 | 100~170 |
Selection Recommendations:
Step 1: Determine the required explosion-proof type (gas, dust, or dual) based on the hazardous area classification drawing.
Step 2: Identify the gas group and temperature class of the combustible materials present, then select the corresponding explosion protection class.
Step 3: Establish the lifting capacity and work duty based on the load weight and handling frequency.
Step 4: Choose between a standard or non-standard span according to the factory building dimensions.
Overspecifying the explosion protection class is unnecessary—Ex dⅡBT4 meets the requirements for the vast majority of petrochemical applications. Upgrading to Ex dⅡCT4 is only required where Group IIC gases such as hydrogen or acetylene are present. Kelude offers complimentary selection consultations and on-site surveys.
Explosion-Proof System Configuration and Inspection Maintenance
Explosion-Proof Electrical System: The electrical system of an explosion-proof overhead crane comprises five core modules: explosion-proof motors (flameproof 'd' or increased safety 'e'), an explosion-proof electrical control box (Ex d flameproof enclosure), an intrinsically safe operating station (Ex ib IIB/IIC T4), explosion-proof limit switches (Ex d or Ex i design), and explosion-proof junction boxes. All electrical components must have valid explosion-proof certificates, and installation must comply with GB/T 3836.15-2021, "Explosive Atmospheres – Part 15: Design, Selection, and Installation of Electrical Installations."
Anti-Static and Earthing: The traveling wheels of explosion-proof cranes are made from copper alloy anti-static material to prevent spark generation from friction. The crane rails must be reliably earthed with a grounding resistance of ≤4Ω. Safety devices such as overload limiters and load moment limiters (LML) must be intrinsically safe (Ex ia/ib) or flameproof (Ex d). Wire ropes should be lubricated with explosion-proof grade lubricating oil to prevent static accumulation. For further guidance on selecting from the full range of overhead cranes, refer to Overhead Crane Models, Parameters, Pricing, and Selection Guide.
Inspection and Maintenance Cycle: Explosion-proof overhead cranes must undergo annual inspections in accordance with TSG Q7015-2016, "Rules for Periodic Inspection of Lifting Appliances," along with dedicated explosion-proof inspections per AQ 3009-2007, "Safety Specification for Electrical Equipment in Hazardous Areas." These special inspections must be conducted at least semi-annually and cover: flameproof enclosure joint inspection (gap ≤0.2mm), cable entry device seal ring aging checks, insulation resistance testing of explosion-proof motors (≥0.5MΩ), grounding resistance testing (≤4Ω), and wear inspection of anti-static wheels (copper alloy layer thickness ≥1.5mm). The explosion-proof CCC Ex certification requires license renewal every 5 years. User units must maintain a comprehensive device management log documenting all inspections and maintenance activities.
Frequently Asked Questions (FAQ)
Q: What is the fundamental difference between the enclosures of Ex dⅡBT4 and Ex dⅡCT4?
A: The reference pressure of a CT4 enclosure is 1.5 to 2 times higher than that of a BT4 enclosure, because hydrogen has an extremely low minimum ignition energy (0.019mJ) and produces a higher peak explosion pressure. CT4 flameproof enclosures must be fabricated from cast steel or welded high-strength steel plate, with wall thickness increased by 30–50% compared to BT4, and narrower flameproof joint gaps (IIB ≤0.2mm, IIC ≤0.1mm). In practice, if any of hydrogen, acetylene, or carbon disulfide is present on site, Ex dⅡCT4 must be selected over BT4.
Q: Can a dust explosion-proof crane operate without explosion-proof motors?
A: No. Ex tD A21 IP65 requires all electrical equipment to have a protection rating of at least IP65, and the motors must be certified dust explosion-proof (Ex tD A21). A standard motor, even with IP65 protection, does not meet explosion-proof requirements—dust explosion-proof motors must also control the enclosure surface temperature to below the dust layer ignition temperature (T85°C or T135°C) and carry anti-static certification. Kelude's dust explosion-proof overhead cranes come standard with Ex tD A21 IP65 dust explosion-proof motors.
Q: What factors drive the price differences when selecting an explosion-proof overhead crane?
A: Price variations primarily stem from: ① explosion-proof motors (IIC class costs 30–50% more than IIB); ② explosion-proof electrical control boxes (cast steel costs 20–40% more than welded steel plate); ③ copper alloy anti-static wheels and rail earthing systems (adding 15–25%); ④ explosion-proof CCC Ex certification and type testing fees (approximately $3,000–$7,500 per unit); and ⑤ special materials (e.g., thermal insulation layers on BZ Type models adding 10–15%). Within the same explosion protection class, the price gap narrows as span and lifting capacity increase.
Q: In which hazardous areas can an explosion-proof overhead crane be used?
A: Ex dⅡBT4 and Ex dⅡCT4 cranes are suitable for gas environments in Zone 1 (where an explosive gas atmosphere is likely to occur during normal operation) and Zone 2 (where an explosive gas atmosphere is unlikely during normal operation, and if it does occur, it persists only briefly). Ex tD A21 cranes are suitable for dust environments in Zone 21 (where combustible dust clouds are likely during normal operation) and Zone 22 (where dust clouds may occur under abnormal conditions). Note that Zone 0 (where an explosive gas atmosphere is present continuously or for long periods) does not permit the installation of any crane equipment; alternative material handling solutions must be employed in these areas.
