Most facilities spec the wrong EOT crane type and spend years managing the consequences. A single girder crane forced into heavy-duty service wears out in 8-10 years instead of 20. A double girder crane over-specified for light loads adds 30-40% unnecessary cost with no performance return. Electric Overhead Travelling cranes split into two primary configurations—single girder and double girder—and each suits a defined range of load, span, duty, and budget conditions. This guide covers design differences, capacity and span ranges, duty classification matching, installation requirements, and the decision criteria determining which configuration fits your specific project.
What Are EOT Cranes?
EOT cranes are electrically operated bridge cranes travelling on elevated runway beams. A bridge spans the runway rails. An end truck assembly rides each rail. A hoist and trolley system handles the load.
The entire bridge travels along the runway. The trolley travels across the bridge. This two-axis movement covers the full working floor area beneath the crane. Single and double girder variants share this basic structure but differ significantly in how the bridge is built.
Single Girder EOT Cranes
Single girder cranes use one main beam forming the bridge. The hoist hangs from the lower flange of this beam. The trolley runs below the girder, which limits hook height but reduces overall crane depth.
Capacity range sits between 1 and 20 tons. Span covers up to 30-35 meters in standard configurations. Duty classes A3-A5 cover the operational range—light to moderate service with 5-12 lift cycles per hour.
Where Single Girder Works Best
- Workshops and fabrication shops with loads under 15 tons
- Buildings with limited headroom needing shallow crane profiles
- Cost-sensitive projects requiring fast installation and lower structural load
- Operations with moderate duty cycles under 5,000 hours annually
Double Girder EOT Cranes
Double girder cranes use two parallel main beams. The crab mechanism—hoist and trolley combined—rides on top of the girders. This raises the hook to the maximum available height and supports far heavier loads.
Capacity starts at 10-20 tons and scales to 250+ tons. Spans exceed 40 meters routinely. The dual beam structure distributes loads more evenly and resists deflection across long spans. Duty classes A5-A8 apply—moderate to severe service in steel mills, foundries, and multi-shift production facilities.
Where Double Girder Works Best
- Heavy manufacturing with consistent loads above 20 tons
- Wide-bay facilities requiring spans over 30 meters
- Operations needing maximum hook height under the roof structure
- High-cycle environments running intensive multi-shift operations
Key Design Differences
The hook height difference is the most underestimated factor. Single girder cranes lose 600-900mm of vertical clearance because the hoist hangs below the beam. Double girder cranes recover this height with top-mounted crab units. In a facility with 8-meter clearance, that difference determines whether tall loads can be handled at all.
Maintenance access differs fundamentally. Double girder bridges include walkway platforms along the girder tops. Technicians reach the crab, hoist, and electrical systems at crane level. Single girder cranes require external platforms, ladders, or mobile equipment for the same access.
Structural weight splits the cost equation. Single girder cranes weigh 30-40% less. Lighter cranes need lighter runway beams and supporting columns. This reduces building structure costs, which often equals or exceeds the crane cost itself in new construction.
Duty Class and Application Matching
Duty class governs structural design, not just operational tempo. A crane specified below its actual duty class experiences accelerated fatigue. Bearings, welds, and structural joints fail earlier—often before the first major overhaul interval.
Single girder suits A3-A5 duty reliably. Double girder handles A5-A8 without structural compromise. The contrarian insight: many facilities running A5 duty with 15-ton loads choose single girder to save cost—then replace the crane at year 12 instead of year 22. The 25% initial saving costs far more over time.
Installation and Building Requirements
Single girder cranes suit both new and retrofit installations. The lighter structure works with smaller runway beams. Existing building columns often carry single girder loads without reinforcement.
Double girder cranes require heavier runway beams and stronger column bases. New construction can account for this in the structural design. Retrofitting an existing building for double girder loads often triggers significant structural work adding 20-35% to project cost.
Headroom requirements differ by design. Single girder cranes need less vertical clearance. Double girder systems consume more height due to the crab mechanism sitting above the bridge. Measure available headroom carefully before specifying either type.
Frequently Asked Questions
Can a single girder crane handle 20-ton loads?
Single girder cranes can be manufactured for 20 tons, but the practical upper limit before double girder becomes more cost-effective and structurally reliable is 15-17 tons. At 20 tons on spans beyond 20 meters, deflection and fatigue risk increase measurably. Specify double girder for consistent 20-ton operations above 20-meter spans.
What is the lifespan difference between single and double girder cranes?
Properly duty-matched single girder cranes last 18-22 years. Double girder cranes in A6-A8 service deliver 20-25 years when maintained correctly. The gap closes when single girder cranes are run above their rated duty class—where service life drops to 10-14 years. Matching duty class to actual operating intensity determines lifespan more than girder count.
Does double girder always cost more installed?
Equipment cost is higher—typically 30-50% above equivalent single girder. But total installed cost depends on building structure. In new construction where columns are designed for double girder loads from the start, the cost gap narrows. In retrofits, structural upgrades can make double girder total project cost 60-80% higher than single girder.
Which type suits a 10-ton, 20-meter span application?
Single girder handles this confidently at A3-A5 duty. The span and load sit well within standard single girder capability. Double girder would over-specify the requirement, adding unnecessary cost. Only upgrade to double girder here if the duty class exceeds A5 or if hook height is a critical constraint.
How do control systems differ between types?
Control systems—pendant, wireless remote, or cabin—apply to both types equally. Double girder cranes more commonly include operator cabins because the larger bridge structure accommodates cabin mounting and because heavy-duty operations justify the ergonomic investment. Single girder cranes more typically use pendant or radio remote controls due to lighter construction.
Conclusion
Single and double girder EOT cranes serve defined roles. Single girder handles 1-20 tons across moderate spans and duty cycles with lower cost and lighter building requirements. Double girder handles 20-250+ tons across wide spans and intensive duty cycles with superior hook height, maintenance access, and long-term structural performance. The decision turns on four factors: load, span, duty class, and available headroom. Get these four right and the crane type follows logically.
Heben Cranes manufactures both single and double girder EOT cranes engineered to specification—not catalog defaults. Capacities from 1 ton to 250+ tons, spans to 40+ meters, duty classes A3 through A8, and full control system options from pendant through radio remote and operator cabin. Every crane ships with load test certification, structural calculations, and installation support. Our technical team evaluates your load, span, duty cycle, and building conditions before recommending a configuration—so the crane you receive matches what your facility actually needs for the next 20
