Single Trolley with Two Hooks Bridge Crane

A single trolley with double hook overhead crane means that there is only one trolley on the main crane girder, but this one trolley is equipped with two hooks, often referred to as the main hook and the secondary hook. The lifting capacity of the main hook is usually higher, while the lifting capacity of the secondary hook is lower. This configuration is ideal for lifting irregular objects, and because single-hook designs are not stable and have limited maneuverability, cranes equipped with a secondary hook tend to be more stable and can assist in turning objects. Ideal for equipment maintenance as well as the processing industry.

Structure And Design

1. Main Girder Construction

The bridge crane's main girder is fabricated from high‑strength, welded steel box or I‑section beams, designed for optimal rigidity and minimum deflection under load. The main beam can be single beam or double beam structure. Finite element analysis is used to determine flange thickness and web dimensions, ensuring the girder supports dual‑hook trolley loads evenly. End trucks equipped with ground‑milled wheels ride on parallel runway rails, distributing the overall weight and minimizing wear.

2. Trolley Frame And Hoist Mounting

The trolley frame comprises a welded steel chassis sized to carry two hoists side by side or in an offset layout, depending on the application. This frame supports either two identical hoist units for synchronized lifts or a main‑and‑auxiliary hoist arrangement, where the auxiliary hook addresses load stabilization and minor adjustments. The spacing between the hooks supports adjustment to accommodate the different shapes of the load. Precision‑machined wheel bearings and hardened gear reducers deliver smooth trolley travel and reliable performance over thousands of cycles.

3. Runway And End‑Truck Assembly

Runway beams—secured to building columns or dedicated runway supports—guide the bridge's travel. End trucks incorporate motor‑driven wheels on adjustable axles to accommodate rail tolerances, reducing binding and ensuring consistent load paths. Anti‑derailment devices on the trucks further enhance safety by preventing wheel lift‑off under dynamic loads.

Advantages

1. Load Stability And Control

Dual hook points reduce tilt and rotation, ensuring large or irregularly shaped loads remain level throughout the lift—this is critical in aerospace and composite manufacturing where even minor misalignment can impact assembly quality.

2. Increased Throughput

With independent hook control, operators can perform two lifts per cycle without repositioning the bridge, effectively doubling material handling rates in bulk loading or production line scenarios.

3. Reduced Infrastructure Costs

Compared to dual‑trolley systems, single trolley dual‑hook cranes require only one set of bridge drive units and control circuits, lowering initial cost and simplifying runway support requirements.

4. Lower Maintenance Complexity

Fewer moving parts—one trolley instead of two—mean reduced points of failure. Common components such as wheels, motors, and brakes are centralized, streamlining spare parts inventory and preventive maintenance tasks.

5. Optimized Headroom and Hook Approach

Single trolley designs reduce the required headroom envelope compared to dual‑trolley alternatives, maximizing usable vertical space in low‑clearance facilities. Hook approach—the horizontal distance from runway to hook centerline—is maintained for both hooks without doubling runway width.

Dual-Hook Operational Mechanics

Precision Control and Load Management

The system's design ensures synchronized or independent hook operation without compromising safety:

1. Load Distribution Monitoring:

   • Strain gauges embedded in the trolley frame measure real-time load distribution.

   • If one hook bears >60% of the total weight, the system triggers an audio-visual alarm and restricts further hoisting (per ANSI/ASME B30.2 safety requirements).

2. Speed Synchronization:

   • Variable frequency drives (VFDs) allow operators to match hoisting speeds between hooks (0.5–8 m/min).

   • A 2021 study by the European Materials Handling Federation showed synchronized dual-hook systems reduced load adjustment time by 33% compared to manual repositioning.

3. Anti-Sway Technology:

   • Inverter-controlled trolley travel accelerates/decelerates gradually, limiting load swing to ≤5 degrees (critical for narrow aisles or multi-crane facilities).

Applications

1. Aerospace And Composite Manufacturing

Long fuselage sections, wing assemblies, and composite panels often demand two‑point lifting to avoid deformation. Dual‑hook cranes deliver the necessary stability and precision for these delicate components.

2. Power Plant Maintenance

Large turbines, generators, and heat exchangers require balanced lifts at multiple points. A single trolley with two hooks enables removal and installation with minimal load sway, improving safety and alignment during maintenance.

3. Shipyards And Maritime Operations

Ship sections, lifeboats, and deck machinery often need dual‑hook handling. Parallel or tandem lifts accelerate assembly and repair tasks, cutting vessel dock time.

4. Specialty Fabrication

In industries such as wind‑turbine manufacturing and heavy machinery production, dual‑hook cranes support parallel handling of large castings and machined parts, streamlining work flows and reducing manual rigging effort.

5. Precision Assembly Lines

Automotive and railcar assembly lines benefit from tandem lifts of chassis or sub‑assemblies. Coordinated hook movement ensures precise placement, improving throughput and reducing scrap rates.

FAQs

Q: Can the hooks operate at different heights?
A: Yes. Our system allows height differentials up to 4 meters via independent drum controls.

Q: What's the lead time for a custom 25-ton dual-hook crane?
A: 14–18 weeks, including design validation, material procurement, and FAT (Factory Acceptance Testing).

Maintenance and Lifecycle Management

Preventive Maintenance Schedule

Component Lifespan

• Wire Ropes: 8–12 years (with proper lubrication and <10% broken wires).

• Hooks: 15–20 years (if annual MPI shows no cracks).

• Electronics: 10–15 years (subject to environmental conditions).

How to get quotation?

Send us your RFQ including the parameters above, we will reply our quotation accordingly.