A double girder crane carries its hoisting mechanism on top of two box girders instead of underneath a single one. That one change gives you four things a single girder crane cannot match: much heavier capacity, a hook that lifts higher in the same building, room for two hoists on one bridge, and a maintenance platform you can actually stand on. It costs more and it loads your building harder — so it is worth specifying properly rather than by habit.
Two parallel box girders are bolted or welded into a bridge with end carriages at each corner. An open winch trolley runs on rails on top of the girders: a fabricated frame carrying the hoisting drum, reducer, brake, motor and the trolley travel drives. Because the drum is up there in the open rather than inside a compact hoist, the rope reeving can be arranged for the duty — single rope for standard hook work, doubled reeving for heavy loads, two separate hooks for main and auxiliary lifting, or a grab / magnet / C-hook attachment instead of a hook.
The higher hook position is the reason many buyers pay for double girder even when the load is light: the hook can come within a few hundred millimetres of the girder, which in a low building means lifting the load higher over machinery. If your building is the constraint and you cannot raise the roof, this is often the cheaper fix.
Control is normally from a cabin hanging under the bridge with the operator looking along the hook — the right choice when the operator must see the load precisely or work all shift in the same bay. Where floor-running machines and people share the space, radio remote with a walk-on operator and an anti-collision device is often safer. Our standard quotation assumes you tell us which one you want; we will recommend based on your cycle.
The pattern is always the same: heavy loads, long shifts, or a hook pattern that only two girders can carry. If any two of those apply to you, a double girder machine is the honest choice and we will say so.
Two 50 t cranes can differ by 30–50% in price purely on duty class. Duty class (A5 / A6 / A7, or FEM 1Bm / 1Am / 2m, or ISO M5 / M6 / M7) is a measure of how often the crane is used and how heavily it is loaded — not how heavy a single lift is. It changes the motor sizes, the reducer ratings, the brake sizes, the rope safety factor, the wheel material and the girder stiffness.
A workshop crane lifting a few times an hour is A5. A production crane in a two- or three-shift plant is A6. A grab crane in a waste plant or a ladle crane in a foundry is A7 territory. If you specify A5 for A7 work, the crane will fail early and nobody will honour the warranty as a manufacturing defect. If you specify A7 for A5 work, you simply paid too much. Tell us the process and we will classify it with you, in writing, on the offer.
For cranes wider than a container, we plan the shipping split early — girder sections, transport brackets, and a welding or bolting method you can close on site — and that plan goes into the quotation, not into a phone call after the order.
| Capacity | 5 t, 10 t, 16 t, 20 t, 32 t, 50 t, 75 t, 100 t (with or without auxiliary hoist) |
|---|---|
| Span | 10.5 m – 31.5 m standard; wider spans engineered to order |
| Lifting height | 6 m – 30 m |
| Duty classification | A5–A7 (FEM 1Bm–2m, ISO M5–M7) |
| Trolley | Open winch trolley, single or double drum; main + auxiliary hooks; grab / magnet / C-hook versions |
| Hoisting speed | 0.5–8 m·min⁻¹ stepless with VFD (typical); two-speed options |
| Bridge travel speed | 30–60 m·min⁻¹ with VFD depending on duty |
| Trolley travel speed | 20–40 m·min⁻¹ |
| Power supply | 380 V / 50 Hz, 3-phase standard — other voltages and 60 Hz on request |
| Control | Cabin with AC, radio remote, or cabin plus remote; pendant optional |
| Protection | Overload limiter, travel limiters, buffers, rail sweeps, anti-collision and interlock devices as required |
| Finish | Two coats primer + two coats finish; heavy-duty epoxy or galvanized for outdoor and coastal sites |
The table shows the range we normally supply. Your offer states the exact capacity, span, lifting height, duty class and voltage for your site — and where a figure in this table differs from the offer, the offer prevails. Send us your requirement and we will confirm each line in writing before you order.
When you need capacity over about 20 t; when the span is over 30 m; when a hook must lift close to the roof; when you need two hooks on one bridge, or a grab, magnet or C-hook; or when the crane runs hard every shift. If none of those apply, a single girder crane will do the same job for less, and we will tell you that even though the invoice would be smaller.
A hoist trolley is a compact, sealed wire rope hoist running on the girder — simple, light, and well suited to lighter duty and short spans. An open winch trolley is a built-up frame with the drum, reducer and motor in the open, which allows heavier loads, doubled rope reeving, two drums, and much easier inspection and repair. On double girder cranes above roughly 20 t, the open winch trolley is the normal choice.
That is the first thing to check, and we give you the numbers to check it with. Before you commit, we will send wheel load per corner at rated load, the wheel base, the rail section and the clearance envelope. Your structural engineer confirms the runway and columns. If the wheel loads are too high for the existing structure, the usual fix is a longer wheel base or more wheels rather than a different crane — tell us and we will quote it that way from the start.
Yes — grab cranes for bulk material and waste, magnet cranes with cable reels and control for steel scrap and plate, and C-hooks or coil lifters for steel coils are all standard configurations for us. Tell us the material, the density and the throughput per hour, and we will specify the attachment with the crane rather than after it. Note that grab and magnet duty almost always means A6 or A7, with a heavier structure than a hook crane of the same capacity.
Most cranes up to about 31.5 m span ship in 40 ft containers with the girders split or the bridge partially dismantled, using transport brackets we design and supply. Larger machines with very wide spans often go break-bulk. We send a loading plan and an erection sequence drawing, and we can quote a supervisor to attend site for assembly, testing and handover. If your site has no mobile crane big enough, tell us early — the erection method should decide the shipping split, not the other way around.
Workshops, warehouses, assembly and maintenance bays. Light structure, low wheel load, quick to install.
1–20 t · span to 30 mOutdoor stockyards, precast beds, container and aggregate handling. Hook, grab or C-hook.
3–100 t · rail or tyreLaunching gantries and bridge erection machines for road and rail viaduct projects.
Project-engineeredSend capacity, span and lifting height and we will reply with a specification and a price within 24 hours.
We quote from 4–5 long-term partner factories in Changyuan, Henan. You will know which one is building your crane, our inspectors test it before shipment, and the drawings, test report and manuals travel with the machine. More about how we work →
Crane type, capacity (t), span (m) and lifting height (m) is usually enough for us to quote. Send a photo of your workshop if you are not sure.
