Bridge Crane Selection Guide: LD vs QD vs LH Types Compared

Bridge Crane Types by Structure and Application

Bridge cranes are categorized into two main groups based on structural configuration and intended use:

By Structural Type

By Application

Five Main Models at a Glance

1. LD Type Electric Single-Girder Bridge Crane

The LD Type electric single-girder bridge crane is the go-to solution for workshops handling light to medium loads. With a lifting capacity of 1–20t, spans from 7.5–31.5m, and a work duty classification of A3 to A5, it delivers reliable performance at a budget-friendly price point. The hoisting mechanism uses a CD1/MD1 electric hoist, while the main girder features a box-type or H-beam welded structure. Its simple design keeps installation and maintenance straightforward, making it a popular choice for machine shops, assembly workshops, warehouses, and maintenance bays operating under light-to-medium duty cycles.

In-depth breakdown: LD Type Electric Single-Girder Bridge Crane — Structural Diagram & Application Scenarios

2. QD Type Double-Girder Bridge Crane

The QD Type double-girder bridge crane is the workhorse for heavy-duty applications. Offering a lifting capacity of 5–500t, spans from 10.5–34.5m, and a work duty classification of A5 to A7, this model is built to handle the toughest jobs. The twin main girder design works in tandem with a dedicated trolley hoist, and the hoisting, trolley, and crane bridge mechanisms operate independently for smooth, precise positioning. Operators can choose from floor-mounted pendant control, an operator cabin, or wireless remote control. It's the preferred choice for steelmaking, heavy machinery, shipbuilding, and power plant applications.

In-depth breakdown: QD Type Double-Girder Bridge Crane vs. LD/LH Types — A Side-by-Side Comparison

3. LH Type Hoist Bridge Crane

The LH Type hoist bridge crane sits comfortably between the LD and QD models in terms of capability. With a lifting capacity of 5–50t and spans from 7.5–31.5m, it offers a compelling middle ground. Compared to the LD Type, the LH's double-girder construction delivers significantly higher load-bearing capacity. And versus the QD Type, it swaps the dedicated trolley hoist for an electric hoist, which lowers cost and improves headroom — a key advantage for retrofitting low-profile factory buildings. This model is ideal for medium-duty workshops where overhead clearance is a concern.

In-depth breakdown: LH Type Hoist Bridge Crane vs. QD Type Double-Girder — Which One Fits Your Needs?

4. LB/LXB Type Explosion-Proof Bridge Crane

The LB/LXB Type explosion-proof bridge crane is purpose-built for hazardous environments where flammable gases, vapors, or combustible dust pose a constant risk. Designed and manufactured in compliance with the GB/T 3836 explosion-proof standard, it carries an explosion protection class ranging from Ex dⅡBT4 to Ex dⅡCT4. This makes it suitable for chemical plants, petroleum refineries, coal chemical facilities, pharmaceutical production, and paint shops. The LB model features a single-girder explosion-proof configuration, while the LXB model offers a double-girder design. The hoisting mechanism uses either an explosion-proof electric hoist or an explosion-proof trolley hoist, depending on the configuration.

In-depth breakdown: Explosion-Proof Bridge Crane Selection Guide — LB/LXB Type Hazardous Area Classification

5. LDY Type Overhead Crane for Metallurgic Plants

The LDY Type overhead crane for metallurgic plants is specifically engineered for high-temperature environments involving molten metal handling. With a lifting capacity of 1–20t and a work duty classification of A6 to A7, this crane is built to perform under extreme conditions. Both the main girder and trolley frame are fitted with heat-insulating protective layers that reflect thermal radiation. The hoisting mechanism is equipped with a dual brake system — if one brake fails, the other can independently bring the load to a safe stop. A molten metal leak monitoring system adds an extra layer of safety. This crane is the standard choice for steel ladle and hot metal ladle handling in steel smelting and foundry operations.

In-depth breakdown: How to Select a Metallurgical Foundry Crane — LDY Type High-Temperature Solutions Explained

Full Model Comparison Chart

Note: The price ranges above are estimates for common 5–20t specifications. Actual configurations (span, control mode, crane rail length) can cause significant variation. Kelude Heavy Industry offers free customized quotations.

How to Select the Right Crane in 3 Steps

Step 1: Determine Lifting Capacity

Lifting capacity is the primary factor in crane selection:

• ≤20t — LD single-girder or LH double-girder hoist crane (refer to the comparison table above for further guidance)
• 20–50t — QD double-girder or LH double-girder hoist crane (depending on clearance requirements)
• ≥50t — QD double-girder (the only option; large tonnages require a double-girder trolley configuration)
• Metallurgical duty — Even for lifting capacities ≤20t, an LDY metallurgical crane is mandatory (safety requirement)

Step 2: Assess the Working Environment

Environmental conditions directly determine whether explosion-proof or metallurgical configurations are required:

Step 3: Determine Your Budget and Duty Cycle

Budget and duty cycle (work classification) directly impact the cost-effectiveness of your crane selection:

• Budget under $7,400, occasional use (A3, ≤2 hrs/day) LD Type single-girder — best value for money. A standard 10t/22.5m configuration runs approximately $5,900–$8,900.
• Budget $7,400–$22,200, frequent use (A5, 4–8 hrs/day) LH Type or small-capacity QD Type. The LH's hoist mechanism costs less than the QD's trolley design, and its low-headroom advantage is significant.
• Budget above $22,200, heavy-duty use (A6–A7, 8–16 hrs/day) QD Type double-girder. Although the initial investment is higher, the total lifecycle maintenance cost at A6–A7 duty is actually lower than forcing an LD into heavy-duty service.
• Special environments Filter by model per Step 2, then match your budget to single- or double-girder options. Note that explosion-proof and metallurgical models typically carry a 40%–80% price premium.

5. Common Selection Mistakes to Avoid

Mistake 1: Confusing LD and LH Types

Many buyers assume the LH is simply an upgraded LD, but the two have fundamentally different structures — LD is a single-girder + hoist design, while LH is a double-girder + hoist design. The LH offers higher load capacity, better stability, and a higher work duty than the LD, but it also costs 40%–60% more. The deciding factors are whether your actual lifting capacity exceeds 20t and whether the double-girder configuration is needed for precise trolley positioning.

Buying the Wrong Explosion-Proof Class

A higher explosion-proof class isn't always better — Ex dⅡCT4 costs roughly 30%–50% more than BT4, but for petrochemical Zone 2 areas, BT4 is fully compliant. Conversely, if your environment actually requires CT4 (e.g., acetylene or hydrogen atmospheres) and you opt for BT4, you create a serious safety hazard. Always confirm the hazardous area classification and gas group before making a selection.

Substituting a General-Purpose Crane for Metallurgical Duty

Some small foundries use standard QD overhead cranes to handle molten metal ladles — a serious regulatory violation. Metallurgical LDY cranes differ fundamentally from general-purpose units in heat shielding, dual-brake systems, and secondary protection. Both ISO 4301 Crane Design Standard and TSG Q0002 contain dedicated technical provisions for metallurgical cranes. Never compromise safety to save money with a general-purpose substitute.

Pushing Single-Girder Spans Beyond Limits

The standard maximum span for an LD single-girder crane is 31.5m — anything beyond that requires a double-girder design. We've seen customers request a 36m span on an LD, only to end up with severe main girder deflection and trolley rail-binding issues that forced a complete teardown and rebuild. When your span exceeds standard ranges, stepping up to a double-girder configuration is the more economical choice.

Frequently Asked Questions