Explosion-Proof Bridge Crane Guide for Hazardous Areas
An explosion-proof bridge crane is a specialized lifting solution engineered for hazardous, flammable atmospheres. Every electrical and mechanical component is either flameproof or increased-safety rated. The LB series serves Zone 1/Zone 2 gas environments, while the LXB underhung model is suited for Zone 2. The first step in selection isn't capacity—it's determining your zone classification.
Explosion-Proof Overhead Crane Overview
Explosion-proof bridge cranes are purpose-built lifting systems for flammable and explosive atmospheres. Their defining feature is that every electrical and mechanical component is designed with explosion protection, enabling safe operation in explosive gas or dust environments. Unlike general bridge cranes, explosion-proof models treat every potential ignition source—from the motor and electrical cabinet to the control grip and limit switches—with flameproof or increased-safety enclosures, ensuring the crane never becomes a source of ignition during operation.
These cranes are widely deployed across chemical processing, petrochemicals, coal chemicals, coatings, pharmaceuticals, grain handling, and defense industries where explosive hazards exist. Production environments in these sectors often contain flammable gases (hydrogen, acetylene, methane, gasoline vapor, etc.) or combustible dusts (aluminum powder, coal dust, flour, plastic powder, etc.). A single spark from the crane's electrical system—or a hot surface reaching ignition temperature—could have catastrophic consequences. For this reason, using explosion-proof cranes that meet national standards in classified areas isn't just a safety measure; it's a legal requirement. The GB 3836 series of standards explicitly governs the selection and installation of electrical equipment in explosive atmospheres.
Understanding Explosion Protection Classes
Hazardous Area Classification
Selecting the right explosion-proof crane starts with identifying the zone classification of your facility. Per GB 3836.1-2021 (Explosive Atmospheres – Part 1: Equipment – General Requirements), hazardous areas are divided as follows:
Gas/Vapor Explosive Atmospheres:
- Zone 0: An explosive gas atmosphere is present continuously or for long periods (over 1,000 hours per year)—the highest risk level. Standard electrical equipment is typically prohibited here, and even explosion-protected devices face strict limitations.
- Zone 1: An explosive gas atmosphere is likely to occur in normal operation (10–1,000 hours per year). This is the most common application zone for explosion-proof cranes; the LB series and select LXB models are rated for this area.
- Zone 2: An explosive gas atmosphere is unlikely in normal operation, or if it occurs, it persists only briefly (no more than 10 hours per year). The LXB explosion-proof underhung crane is suitable for this zone.
Combustible Dust Atmospheres:
- Zone 20: Combustible dust clouds or layers are present continuously or for long periods (over 1,000 hours per year).
- Zone 21: Combustible dust atmospheres are likely to occur in normal operation.
- Zone 22: Combustible dust atmospheres are unlikely in normal operation, or if they occur, they persist only briefly.
Explosion Protection Types
Here's how the common protection types compare:
| Explosion-proof Type | Code | Principle | Applicable Area |
| Flameproof | Ex d | Enclosure Withstands Internal Explosion Pressure, and Prevents Explosion Propagation to External Environment | Zone 1, Zone 2 |
| Increased Safety | Ex e | Enhanced Safety Measures for Electrical Equipment, Prevention of Arcing/Sparking/Overheating | Zone 2(Part of Zone 1) |
| Flameproof+Increased Safety Composite Type | Ex de | Combining Flameproof Enclosure with Increased Safety Wiring, Yes, the Most Common Type for Explosion-Proof Cranes | 1Zone,2Zone |
Understanding the Explosion Proof Marking
The marking on an explosion-proof crane nameplate, such as Ex d ⅡB T4 Gb, is decoded from left to right as follows:
- Ex: Explosion-proof marking (per Chinese and IEC standards)
- d: Type of protection — Flameproof enclosure
- ⅡB: Gas group (ⅡA — propane/acetone; ⅡB — ethylene/ethyl ether; ⅡC — hydrogen/acetylene, with ⅡC being the most hazardous)
- T4: Temperature class (T1 to T6; T6 permits a max surface temperature of 85°C, while T4 allows 135°C)
- Gb: Equipment protection level (Ga — for Zone 0; Gb — for Zone 1; Gc — for Zone 2)
As the technical director at Kelude Heavy Industry explains: "The first step in selecting an explosion-proof crane is not determining the lifting capacity, but identifying the zone classification and gas group of the operating environment. The zone classification dictates the type of protection required, while the gas group sets the minimum explosion protection class — for instance, a ⅡC group (hydrogen environment) demands equipment rated ⅡC, and ⅡB-rated equipment cannot be used in a ⅡC environment."
LB Type Explosion-Proof Single-Girder Bridge Crane
The LB type explosion-proof electric single-girder bridge crane is an explosion-proof variant developed from the LD type electric single-girder crane. It is designed for use in Zone 1 and Zone 2 explosive gas atmospheres as well as Zone 21 and Zone 22 combustible dust environments.
Parameter Range
- Lifting Capacity: 1–20 t
- Span: 7–30 m
- Lifting Height: 6–30 m
- Work Duty: A3–A5
- Explosion Protection Class: Ex d ⅡB T4 Gb to Ex d ⅡC T4 Gb
Key Technical Features
Explosion-Proof Motor System: The LB type is fitted with Ex d ⅡB T4 or Ex d ⅡC T4 flameproof conical rotor motors. The motor housing is manufactured to GB 3836.2-2021, with flameproof joint gaps kept at ≤0.2 mm. The motor junction box is Ex d ⅡB flameproof with increased-safety internal wiring. Hoisting motor power ranges from 5 to 42 kW (configured by capacity), while travel motor power is 0.8–3 kW.
Explosion-Proof Electrical Control System: The complete electrical control system comprises an explosion-proof electrical cabinet, an explosion-proof push-button pendant, explosion-proof limit switches, and explosion-proof conductor rails. The electrical cabinet housing is made of cast aluminum alloy and has passed a pressure test at 1.5 times the rated pressure. The control circuit operates at AC 36V safety voltage to effectively eliminate electric shock hazards.
Explosion-Proof Electric Hoist: Equipped with an HB or BCD type explosion-proof electric hoist rated Ex d ⅡB T4. The hoisting speed is 8 m/min (7 m/min for capacities above 10 t), with a travel speed of 20 m/min. The wire rope is galvanized or phosphated, and the hook is treated with a copper-alloy spark-reducing process to prevent ignition from accidental impact with the load.
Safety Protection Devices: Includes an explosion-proof power-off limit switch, an explosion-proof overload limiter (accuracy ±5%), and explosion-proof travel limit switches. All safety devices carry the Explosion Proof Certificate and are reliable for operation in Zone 1 environments.
LXB Type Explosion-Proof Single-Girder Suspension Crane
The LXB type explosion-proof electric single-girder suspension crane is a suspended-mount explosion-proof crane. Its main girder is directly attached to the factory roof truss or crane runway girder via a suspension system, requiring no floor space. It is suited for Zone 2 explosive gas atmospheres and Zone 22 combustible dust environments.
Parameter Range
- Lifting Capacity: 1–10 t
- Span: 3–16 m
- Lifting Height: 6–24 m
- Work Duty: A3–A4
- Explosion Protection Class: Ex d ⅡB T4 Gc to Ex d ⅡC T4 Gc
Key Differences from the LB Type
The LXB type uses a suspended mounting arrangement that eliminates the need for corbels and runway beam columns, offering greater installation flexibility — an ideal choice for explosion-proof retrofits of existing factory buildings. However, due to the load limits of the suspension structure, the LXB type has a maximum lifting capacity of 10 t and a maximum span of 16 m. Its applicable zones are primarily Zone 2 (some LXB models can meet Zone 1 requirements on a custom-order basis).
Application Scenarios
The LXB type explosion-proof suspension crane is particularly well suited for:
- Intermediate transfer in paint workshops (handling paint drums, solvent containers, etc.)
- Intermediate product transfer in pharmaceutical plants
- Equipment maintenance and hoisting in small chemical units
- Material handling in fine chemical workshops
LB vs. LXB: How to Choose the Right Crane
| Comparison Item | LB Type Explosion-proof Electric Single-Girder Crane | LXB Type Explosion-Proof Electric Single-Girder Suspension Crane |
| Applicable Area | 1Zone,2Zone(Gas);21Zone,22Zone(Dust) | 2Zone(Gas);22Zone(Dust) |
| Mounting Method | Runway Beam Supported Type(Requires Corbel/Column) | Suspended Type(Mounted Below Roof Truss/Crane Runway Girder) |
| Lifting Capacity Range | 1~20t | 1~10t |
| Span Range | 7~30m | 3~16m |
| Explosion Protection Class | Ex d ⅡB T4 Gb ~ Ex d ⅡC T4 Gb | Ex d ⅡB T4 Gc ~ Ex d ⅡC T4 Gc |
| Lifting Speed | 8m/min(≤10t)/7m/min(>10t) | 8m/min |
| Operation Mode | Electric/Remote Control | Electric/Remote Control |
| Suitable Applications | Large Chemical Workshops, Petroleum Refining Units, Coal Chemical Plants | Fine Chemical Industry, Pharmaceutical, Coatings Workshop, Retrofit and Expansion Projects |
| Reference Price | 4~180,000 CNY (Unit: 10k RMB) | 3~120,000 CNY (Unit: 10k RMB) |
Explosion-Proof Crane Core Component Configuration
Explosion-proof electric hoist is the heart of the entire explosion-proof crane system. The HB-series explosion-proof electric hoist (referencing the 3204 knowledge base data) features Ex d ⅡB T4 explosion protection classification, with a flameproof enclosure manufactured to GB 3836.2-2021 standards and flameproof joint gaps ≤0.2mm. The hoisting mechanism utilizes a three-stage helical gear reduction drive, with gears made of 20CrMnTi steel treated through carburizing and quenching to a hardness of HRC58~62. The explosion-proof wire rope uses a 6×19+IWR stainless steel construction, with a breaking force providing a 6:1 safety factor relative to the rated load.
Explosion-proof motor: Equipped with a flameproof three-phase asynchronous motor, Insulation Class F (temperature resistance 155°C), and IP55 Protection. The motor stator windings undergo vacuum impregnation treatment for enhanced moisture and corrosion resistance. The motor housing is marked with the Ex d ⅡB T4 Gb explosion-proof marking and comes with an Explosion Proof Certificate.
Explosion-proof electrical box: Features a cast aluminum alloy housing (ZL102 material) with an anodized surface finish. The enclosure houses flameproof circuit breakers, AC contactors, thermal overload relays, and other control components. Cable entry points are sealed with explosion-proof stuffing glands, and sealing grommets at cable entries ensure explosive gases cannot enter the enclosure through cable inlets.
Explosion-proof operating devices: Include an explosion-proof pendant station (Ex d ⅡB T4, IP65 Protection Rating), an explosion-proof remote control (intrinsically safe type Ex ia ⅡB T4, signal range ≥100m), and explosion-proof travel switches. The pendant's operating buttons are explosion-proof tactile switches with a housing made of reinforced nylon with anti-static additives, featuring surface resistance ≤1×10⁹Ω.
Three-Step Crane Selection Guide
Kelude recommends the following three-step approach for explosion-proof crane selection:
Step 1: Determine the Explosion-Proof Zone Classification
Review the plant's hazardous area classification drawings or commission a safety assessment agency to conduct an explosive atmosphere evaluation to establish:
- Gas environment: Zone 0, Zone 1, or Zone 2?
- Gas Group: ⅡA, ⅡB, or ⅡC?
- Temperature Class: Which of T1 through T6 applies?
- Dusty environment: Zone 20, Zone 21, or Zone 22?
Step 2: Determine Lifting Capacity and Span
Based on the heaviest single load to be lifted (including the lifting spreader weight), apply a 1.25 safety factor to establish the Rated Lifting Capacity. The span is determined by subtracting the safety clearance on both sides (typically 500~800mm each) from the factory building span. Lifting Height is calculated as the distance from the floor (or operating platform) to the highest lifting point plus a 500mm safety margin.
Step 3: Match the LB or LXB Model
- For Zone 1 gas environments + Lifting Capacity ≤20t + Span ≤30m → select the LB model
- For Zone 2 gas environments + Lifting Capacity ≤10t + Span ≤16m + no crane runway brackets in the building / flexible installation required → select the LXB model
- For Zone 2 gas environments + Lifting Capacity >10t or Span >16m → still select the LB model (the LXB's load-bearing capacity is insufficient beyond these limits)
- For Dusty environments in Zone 21/22 → both LB and LXB models are suitable; the final choice is determined by Lifting Capacity and Span requirements
Kelude engineers note: "The most common mistake in explosion-proof crane selection is using Zone 2-rated equipment in a Zone 1 environment. In the event of a safety incident, incorrect selection doesn't just mean equipment damage—it carries criminal liability. Article 99 of China's Work Safety Law explicitly defines the legal consequences of using safety equipment that does not meet required standards."
Frequently Asked Questions (FAQ)
Q: Which national standards apply to explosion-proof bridge cranes?
A: The Design & Manufacturing of explosion-proof bridge cranes complies with the following key standards: GB 3836.1-2021 "Explosive Atmospheres – Part 1: Equipment – General Requirements," GB 3836.2-2021 "Explosive Atmospheres – Part 2: Equipment Protected by Flameproof Enclosures 'd'," JB/T 10222-2011 "Explosion-Proof Electric Hoists," ISO 4301 Crane Design Standard, and TSG Q7016-2016 "Supervision and Inspection Regulations for Installation, Retrofit, and Major Overhaul of Lifting Appliances." All explosion-proof components must carry an Explosion Proof Certificate issued by a nationally accredited explosion-proof certification body (such as the Nanyang Explosion-Proof Electrical Research Institute).
Q: How do I choose between the LB and LXB models, and which offers better value?
A: In terms of pricing, the LB model (5t/16m) is approximately $7,400–$11,800, while the LXB model (5t/10m) is roughly $5,900–$10,400—the LXB is slightly less expensive but the difference is marginal. The decisive factor is the explosion protection requirement: Zone 1 environments require the LB model exclusively, while the LXB is only suitable for Zone 2 environments with a Lifting Capacity ≤10t and Span ≤16m. For existing factory buildings without crane runway brackets, the LXB's under-hung mounting configuration can save approximately $44,400–$74,000 in structural modification costs.
Q: Do explosion-proof cranes require periodic inspection?
A: Yes. Explosion-proof cranes are classified as special equipment (subject to regulatory oversight when the Lifting Capacity is ≥0.5t) and must undergo periodic inspection at least once per year in accordance with TSG Q7016-2016. Inspection items cover flameproof enclosure joint gaps (≤0.2mm), cable entry sealing integrity, Grounding Resistance (≤4Ω), Insulation Resistance (≥1MΩ), and the legibility of explosion-proof markings. Additionally, the sealing grommets in the explosion-proof electrical box should be replaced every 2 years to ensure sustained explosion-proof performance.
Q: What certifications and lead times does Kelude offer for explosion-proof cranes?
A: Kelude holds a national special equipment manufacturing license (including explosion-proof bridge crane qualifications). All explosion-proof products pass Type Test certification through the Nanyang Explosion-Proof Electrical Research Institute and come with an Explosion Proof Certificate and coal mine safety certification (for mining applications). Standard LB-series explosion-proof single-girder cranes have a lead time of 25–35 days, LXB-series 20–30 days, with custom non-standard configurations requiring an additional 10–15 days. The product Warranty Period is 12 months (24 months for explosion-proof components), with 48-hour after-sales response nationwide.
To compare specifications and pricing across the full bridge crane series, refer to the Complete Bridge Crane Selection Comparison Chart—a single reference covering the differences between the LD, QD, LH, LB, and LDY models.
