Choosing the right overhead bridge crane is a critical decision that impacts your facility’s productivity, efficiency, and long-term operational costs. At the heart of this choice often lies a fundamental question: Should I choose a single girder or a double girder design?

While they may look similar at a glance, these two types of cranes are engineered for different purposes. Selecting the wrong one can lead to unnecessary expense or, worse, a crane that can’t handle your workload. Let’s break down the key differences to help you make an informed decision.

Double girder overhead crane

What’s the Structural Difference?

The names say it all. The primary difference is in the bridge—the beam that moves along the runway rails.

• Single Girder Crane (SGC): Features one main bridge beam. The trolley and hoist run on the bottom flange of this single girder.

• Double Girder Crane (DGC): Features two main bridge beams that run parallel to each other. The trolley and hoist run on a rail installed on top of the girders, typically using a separate track.

This fundamental structural difference leads to variations in capability, performance, and application.

Single Girder Overhead Crane: The Agile Workhorse

Single girder overhead crane

Ideal for: Lighter loads, lower headroom, and cost-effective solutions.

How it works: A single bridge beam spans the bay with end trucks on either side. The hoist is suspended from a trolley that moves along the bottom flange of the girder.

Advantages

• 1. Lower Cost: The most significant advantage. Less material and a simpler design mean a lower initial investment.
• 2. Lighter Weight: The reduced weight can simplify support structure requirements (like building columns and runway beams), potentially saving on construction costs.
• 3. Better for Lower Headroom: Since the hoist is mounted below the girder, it requires less vertical space (crane hook height), making it excellent for facilities with height restrictions.

Limitations

• 1. Lower Capacity: Generally suited for applications up to 20 tons, though some can go higher.
• 2. Shorter Spans: More prone to deflection (bending) over longer spans, which can limit their use in very wide facilities.
• 3. Slower Speeds: Typically designed for slower lifting and travel speeds, which is fine for standard material handling but not for intense, rapid-cycle work.

Double Girder Overhead Crane: The Heavy-Duty Powerhouse

Double girder overhead crane

Ideal for: Heavy loads, long spans, high-duty cycles, and specialized applications.

How it works: Two parallel girders form the bridge. The trolley travels on rails on top of the girders, placing the hoist between the two beams.

Advantages

• 1. Higher Capacity: Designed to handle much heavier loads, commonly from 10 tons up to several hundred tons.
• 2. Longer Spans: The dual-girder design offers superior rigidity and reduced deflection, making it the only choice for wide-span applications.
• 3. Higher Hook Height: The top-running design allows the hoist to be positioned between the girders, providing greater lift height in the same building compared to a single girder bridge crane.
• 4. Durability & Speed: Built for more severe service, higher duty cycles, and faster hoisting/travel speeds. They are the standard for demanding environments like steel mills and foundries.
• 5. Easier Maintenance & Access: Walkways, cabs, and main hoist components are more accessible as they are mounted on top of the bridge.

Limitations

• 1. Higher Initial Cost: Requires more material and a more complex design, leading to a higher purchase price.
• 2. Heavier Weight: The crane itself is heavier, often requiring more robust (and expensive) support structures and runways.
• 3. More Headroom Required: The design consumes more vertical space, which might be an issue in facilities with strict height limits.

Side-by-Side Comparison Table

How to Choose: Which One is Right for You?

Ask yourself these key questions:

• 1. What is your maximum load weight? If it’s under 20 tons and not used intensively, a single girder might suffice. For heavier loads, double girder is mandatory.
• 2. What is your bay span? For spans longer than 80 feet (~25 meters), a double girder crane will provide the necessary stability and reduce deflection.
• 3. What is your available headroom? If every inch of lift height is precious and your building is low, a single girder could be the perfect fit.
• 4. What is your duty cycle? Is the crane running for a few hours a day or in continuous, demanding shifts? Double girders are built for toughness and longevity in harsh conditions.
• 5. What is your budget? Consider both the initial cost and the total cost of ownership. While cheaper upfront, an SGC might not last as long under heavy use, leading to more maintenance and earlier replacement.

The Bottom Line

There is no universal “best” choice—only the best choice for your specific application.

• Choose a Single Girder crane for cost-effective, light-to-medium duty material handling in environments with space or budget constraints.
• Choose a Double Girder bridge crane for heavy loads, long spans, high-speed operation, and severe-duty applications where reliability and durability are non-negotiable.

Always consult with a qualified overhead crane engineer or manufacturer. They can assess your facility, operational needs, and long-term goals to recommend the optimal solution that ensures safety, efficiency, and productivity for years to come.