Why factories stall on their very first lift
Many investors spend months comparing specifications for the main machine, only to discover once the containers arrive that they have no way to take a twelve-tonne machine off the trailer and set it on its concrete foundation to millimetre accuracy. A mobile crane is then rented at a high daily rate, installation slips by weeks, and losses begin before the line has produced a single part. Lifting equipment is not a minor accessory; it is part of the operational infrastructure of the hall, and it must be calculated and ordered together with the production line, not after it.
The three types most used in production halls
Overhead bridge crane
It travels on two runway beams fixed to the building columns or to independent supports, covering almost the entire floor area. The single-girder version is economical and suits capacities up to around ten tonnes, while the double-girder version is used for heavier loads or when lift height is critical, because it raises the hook higher and gives extra vertical clearance.
Gantry crane
It stands on legs that travel on floor-mounted rails and does not require a building structure capable of carrying the loads. It is the logical choice for outdoor yards, for a rented factory where structural modification is not permitted, or when existing columns were never designed for additional lateral loads.
Jib crane
A slewing arm that serves a single workstation within a limited radius. It is inexpensive and quick to install, and is ideal for feeding a press or machining centre with medium-weight molds without tying up the main crane.
Calculating rated capacity correctly
The common mistake is to size the crane on the weight of the heaviest machine alone. A sound calculation adds four elements: the heaviest actual load, the weight of the lifting tackle including spreader beams, slings and chains, a safety margin of at least fifteen percent, and then rounding up to the next standard class. If the heaviest mold weighs 6.2 t and the tackle 0.4 t, the total is 6.6 t; with the margin you reach 7.6 t, meaning the correct choice is an 8 or 10 tonne crane, not a 6.3 tonne one.
Span and lift height: the dimensions everyone forgets
- Span: the distance between the centres of the two runway rails, measured from the actual building structure and not from the architectural drawing.
- Lift height: from floor level to the highest hook position; it must exceed the height of the tallest machine plus sling length and foundation height.
- Headroom: the clearance between the top of the crane and the roof or roof trusses.
- Hook approach: the dead zone near the walls that the hook cannot reach — a direct reason why a crane fails to serve the last station on the line.
Duty class: the spec that separates a ten-year crane from a two-year failure
Cranes are classified under FEM or ISO standards into duty groups that express the number of operating cycles and the average load ratio. An installation crane used a few times a month is fundamentally different from a crane serving a press at thirty cycles per hour. Ordering a class below your real usage saves a small amount at purchase and costs you a motor and brake replacement in short order.
| Item | Single-girder bridge | Double-girder bridge | Gantry | Jib |
|---|---|---|---|---|
| Typical capacity range | 1 - 10 t | 5 - 50 t | 2 - 30 t | 0.25 - 5 t |
| Structural reinforcement needed | Moderate | High | None | Low |
| Coverage | Whole hall | Whole hall | Fixed runway | One station radius |
| Approximate installation time | Days | Weeks | Days | Hours |
Technical requirements to write into the Chinese supplier contract
- Two-speed hoist motor or variable-frequency control for smooth handling and to prevent load swing.
- Overload limiter and end-of-travel buffers on every axis.
- Control panel matching your site voltage and frequency, with a wireless remote in addition to the pendant.
- Signed column load calculations, because your structural engineer needs them before the foundations are poured.
- A 125 percent overload test record as part of the FAT before shipment.
Golden rule: design your hall around the heaviest load you will move five years from now, not the heaviest load you move today; expanding capacity is far easier than replacing a crane already built into the structure.
Safety and operation after handover
The crane is not accepted until an on-site load test has been carried out in the presence of an approved inspection body and the result recorded in an official register. A periodic inspection programme then begins: monthly visual checks of chains, ropes and hook, and calibration of brakes and the overload limiter at least annually. The operator must also be trained and certified; most lifting accidents are caused by wrong hand signals or side pulling rather than by a mechanical defect.
Choosing lifting equipment is a decision made while the hall is being designed, not after the containers reach the port. If you are planning to import a production line and need the crane type, capacity and span defined to match your building structure and installation schedule, contact our team for a technical study and a contract-ready specification for negotiating with Chinese manufacturers.