LD Type Electric Single-Girder Bridge Crane: Structure & Uses

What Is an LD Type Electric Single-Girder Bridge Crane?

The LD Type electric single-girder bridge crane — also referred to as a single-girder overhead crane or electric single-beam crane — is one of the most widely used light-to-medium lifting machines in industrial workshops. Built around a single main girder that carries the trolley and the load, it offers a simple, cost-effective design that is ideal for factory bays with lifting capacities up to 20 tons and spans within 35 meters. The electric hoist travels along the lower flange of the main girder, performing both vertical lifting and horizontal transport.

Compared to double-girder bridge cranes, the LD single-girder configuration delivers a lighter dead weight and a more compact headroom, which can reduce the required building height and makes it the most cost-efficient lifting plan for new factory construction. Across domestic small and mid-sized workshops, the LD single-girder crane handles the majority of indoor lifting tasks and has become the workhorse model for factory logistics and production line handling.

LD Crane Structural Breakdown: Key Components Explained

The LD Type electric single-girder bridge crane consists of five major systems, detailed below.

1. Main Girder

The main girder uses a box girder or H-beam welded structure and serves as the load-bearing backbone of the entire crane. It is typically fabricated from Q235B (≈S235JR) or Q345B (≈S355J2) steel plates, formed through automatic submerged arc welding, straightening, and shot blasting for surface preparation.

• The box-section girder forms a closed cavity with top flange plate, bottom flange plate, and two web plates
• The bottom flange acts as the runway for the electric hoist and must maintain a straightness of ≤2mm/m
• Mid-span camber is controlled within (1/1000–1/700)L to offset elastic deformation under load
• For long spans (≥22.5m), a pre-cambering process is commonly applied

2. End Carriage

End carriages are located at both ends of the main girder, supporting the full crane weight and transferring the load to the runway rail through the wheel blocks. Each end carriage is fitted with one driven and one idler wheel block at both ends.

• End carriages are connected to the main girder with high-strength bolts for easy transport and on-site assembly
• Wheels are made of ZG310-570 cast steel with a tread surface hardness of HB 300–380
• Span deviation across the end carriages is held within ±3mm to ensure even four-wheel contact

3. Electric Hoist

The electric hoist is the hoisting mechanism of the LD crane. It is suspended from the lower flange of the main girder and can travel along the full length of the workshop.

• Hoisting motor: conical rotor asynchronous motor with self-braking function (brakes automatically upon power loss)
• Gearbox: three-stage helical gear drive with gear precision grade 7
• Wire rope: 6×37 alternate lay, safety factor ≥5 (per ISO 4301 Crane Design Standard)
• Lifting speed: 8m/min standard (two-speed option available at 0.8/8m/min)
• Travel speed: 20m/min (inverter-adjustable from 5 to 30m/min)

4. Crane Travel Mechanism

The crane travel mechanism drives the entire crane longitudinally along the runway rails in the factory building.

• Drive configuration: separately driven (independent drive unit at each end) or centrally driven
• Motor: ZDY series conical rotor motor with integral brake
• Gearbox: vertical three-stage gear reduction, ratio selected based on required travel speed
• Braking: power-off braking plus a mechanically closed brake

5. Electrical System

The LD electrical system is powered via an enclosed conductor rail or cable trolley, with floor handle and wireless remote control as the standard dual control modes.

• Power supply: H-type enclosed conductor rail (copper busbar cross-section 10–50mm²) or C-rail cable system
• Control system: contactor and relay logic; PLC plus inverter drive available as an option
• Safety devices: limit switches (hoist upper limit and travel end limits), emergency stop button, phase loss protection, and overload protection
• Remote control: industrial-grade 2.4GHz wireless remote with an effective range of ≥100m, featuring emergency stop and two-speed/multi-speed control

LD Crane Technical Specifications: Standard Parameters

The following table outlines the standard parameter ranges for Kelude LD Type electric single-girder bridge cranes (custom configurations available upon request):

Note: Figures in parentheses indicate two-speed slow-mode data. Lifting height, span, and travel speed can all be customized to match your facility dimensions.

Application Scenarios for Single-Girder Bridge Cranes

The LD Type electric single-girder bridge crane is a versatile solution used across a wide range of industries. Below are four typical application scenarios and the key configuration considerations for each.

1. Factory Workshops

Machining, stamping, welding, and assembly line workshops represent the most common deployment environment for the LD Type. For these applications, we recommend a lifting capacity of 5–10t with a span of 16–25m, paired with an electric hoist featuring variable frequency hoisting. This setup delivers a lifting speed that balances productivity with precise load positioning.

Case Study: An automotive parts manufacturer equipped its assembly workshop with six LD5t × 22.5m single-girder cranes. With variable-frequency drive (VFD) control on the crane bridge, the facility handles 1,200 workstation-level hoisting and transfer operations per shift.

2. Warehouses & Logistics Centers

Steel coil warehouses, pipe storage facilities, and pallet racking systems demand cranes capable of long-travel distances and wide spans. Typical spans range from 25–31.5m with lifting capacities of 3–10t. Adding a frequency inverter to the electric hoist travel drive minimizes load sway during movement.

Case Study: A steel processing and distribution center deployed an LD10t × 28.5m configuration covering a 6,000m² storage area, achieving a daily throughput exceeding 300 tons.

3. Outdoor Yards & Transfer Stations

For semi-open outdoor yards and rail transfer terminals, the LD Type requires anti-corrosion treatment. Motors should be upgraded to IP55 protection rating, and the electrical cabinet must be fitted with a rain cover.

4. Maintenance Workshops

Railway locomotive servicing and construction machinery repair facilities often require a wide range of lifting capacities (2–20t). The LD Type can be combined with KBK flexible crane systems to handle both heavy-duty lifting and lighter component handling tasks.

LD Type vs. LDA Type: Key Differences Explained

The LDA Type is an upgraded version of the LD Type. The core differences between the two models are outlined below:

In short: When workshop height is limited, the LDA crane (Low-Headroom version) is the preferred choice, saving 300–500 mm of clearance over the standard LD Type. When headroom is ample and cost-effectiveness is the priority, the standard LD Type is the way to go. The two models share highly interchangeable components—end carriages, crane travel mechanisms, and electrical systems—with over 80% spare parts commonality.

LD Type Selection Guide: Span and Lifting Capacity Pairings

The key to selecting the right crane is matching the span with the lifting capacity. Below are proven combinations based on engineering practice:

Recommended Span-to-Capacity Combinationss

Three-Step Selection Guide

1. Determine Lifting Capacity: Multiply the heaviest workpiece weight by a 1.25 safety factor, then round up to the nearest standard capacity rating.

2. Determine Span: Subtract 1.5–2 m from the workshop column spacing, then select the nearest standard span value.

3. Determine Work Duty: For daily operation of ≤4 hours, select A3; for 4–8 hours, select A4; for continuous heavy-duty operation, select A5.

Example: A workshop with 24 m column spacing, heaviest workpiece of 4 t, and 6 hours of daily operation — recommended configuration: LD5t × 22.5 m, A4 work duty, equipped with an MD1 two-speed electric hoist.

Key Advantages of Kelude LD Series Cranes

Kelude LD-type electric single-girder bridge cranes are designed and manufactured in accordance with ISO 4301 Crane Design Standard and JB/T 1306-2008 Electric Single-Girder Crane Standard, offering the following core advantages:

• Pre-Cambered Main Girder: Fabricated with CO₂ gas-shielded welding and CNC cutting, with camber calculated per individual load requirements. No-load camber reaches 1/700–1/1000 of the span.
• Factory Load Testing Before Delivery: Every crane undergoes a static test with rated load at 110% and a 125% Dynamic Load Test prior to shipment, accompanied by a third-party type test report.
• Modular End Carriage: The end carriage and main girder are connected with removable high-strength bolts, allowing the crane to be disassembled and packed into a standard container — reducing freight costs by 30–40% compared to fully assembled shipment.
• Guaranteed Delivery Time: Standard specifications (≤10 t / ≤22.5 m) are delivered within 15–20 working days after receipt of deposit.
• Custom Solutions: Fully customized options available for non-standard spans, special lifting heights, explosion-proof environments, and high-temperature environments.

For LD-type single-girder crane solutions or quotations, feel free to contact the Kelude technical team for detailed engineering drawings and specifications.

To compare specifications and pricing across the full range of overhead cranes, refer to the Complete Overhead Crane Selection Comparison Chart — a single table covering the differences between LD, QD, LH, LB, and LDY models.

Frequently Asked Questions