Begin with what the crane must lift
A crane is a long-term fixture, so the choice is worth slowing down for. Before comparing types, write down:
- The heaviest load it must ever lift, including any lifting beam, tooling or other accessory hanging below the hook.
- The typical load, which is often much lighter.
- The size and shape of loads, and whether they must be turned, tilted or positioned precisely.
- Where loads must be picked up and set down, as a footprint on the floor.
- How often lifts happen, and for how many hours a day.
These answers shape every other decision. The capacity should leave room for the heaviest realistic load plus accessories, but buying far more than needed adds cost and structural demands on the building. The right balance needs the actual weights, not estimates.
The main crane types
Bridge cranes
A bridge crane, also called an overhead traveling crane, has a bridge that spans the width of a bay and travels along runway rails mounted high on the building columns or on its own supports. A trolley with a hoist moves along the bridge. Together, the three motions cover a rectangular area. These are the classic overhead cranes in factories, fabrication shops and warehouses.
They come in single-girder and double-girder designs. Single-girder cranes are typically lighter and less costly and are often used for lighter capacities. Double-girder cranes are typically chosen for heavier loads, longer spans and tougher duty, and they can allow greater hook height since the hoist can sit between or on top of the girders.
Their strength is that they use overhead space and keep the floor free. Their drawback is that the building (or a separate support structure) must carry the runway loads, and the runway and crane must fit within the roof height.
Gantry cranes
A gantry crane runs on legs, usually on floor-level rails or wheels, rather than on elevated runways. This makes it suited to outdoor yards, to buildings with no structure to carry a runway, and to situations where the crane must be moved or relocated. Types include full gantry, semi-gantry (one side on a wall-mounted runway, the other on legs) and portable gantries for lighter work.
Gantries cost floor space and may be affected by wind when used outdoors, so site conditions should be reviewed with the supplier.
Jib cranes
A jib crane has a horizontal boom, mounted to a wall, column or free-standing mast, that swings through an arc with a hoist traveling along it. It serves a limited area, such as one machine or workstation, but does so well and economically. Several jib cranes can sometimes relieve a larger crane of repetitive small lifts.
Other options
Monorail systems, which move a hoist along a single beam, suit fixed linear paths. Workstation cranes with lightweight rails suit lighter loads at benches. Mobile cranes, which are a different category, are better for occasional outdoor lifts.
The key questions behind the choice
Capacity
Rated capacity is the maximum load the crane is designed to lift under its specified conditions. It should come from the manufacturer’s nameplate, and the crane must never be loaded beyond it. Remember that any attachment under the hook counts toward the load. The matter of ratings for accessories is discussed under load handling attachments.
Span and coverage
Span is the horizontal distance between the runway rails (center to center for the crane). It decides how wide an area the bridge can serve. The runway length decides how far along the building the crane can travel. A frequent design issue is the “approach,” the minimum distance the hook can reach to the wall or end of the runway, which can leave dead zones along the edges. If loads must be picked up near walls, specify that early.
Hook height and headroom
The hook can only go as high as the building and crane geometry allow. The distance between the underside of the roof structure and the floor limits the height available above the runway, and a double-girder crane typically allows greater hook height than a single-girder crane of the same span. Check clearance for the tallest load plus rigging, and for lights, pipes, and ductwork that might obstruct the crane.
Speed and control
Crane speeds are typically specified for hoisting, trolley travel and bridge travel, and many cranes offer variable speed for smoother handling. For delicate or precise loads, slower, controllable speeds are valuable. Control can be by pendant, radio remote or cab, and the best option depends on visibility and where the operator should stand. Safety features like limit switches and overload protection should be part of the specification, consistent with the discussion of machine safety features.
Duty cycle
Duty cycle describes how hard the crane will work: how often it lifts, how close to its capacity, and for how long. Standards organizations define duty classes, ranging from light, occasional service to heavy, near-continuous service. A crane used a few times a day for light work and one running multiple shifts at near-rated loads are very different machines. Be honest with suppliers about the duty, as underestimating it leads to premature wear.
Power and environment
Consider the available electrical supply and how power reaches the moving crane. Also consider the surroundings: heat, dust, moisture, corrosive air, or hazardous atmospheres call for special design, which links to the topic of harsh environment protection. Outdoor cranes need weather protection and attention to wind.
Building and foundations
A bridge crane’s loads are carried by the runway beams and building structure. A qualified structural engineer should confirm that the structure can handle the added loads, and gantry cranes need suitable ground or rails. Do not assume an existing building can carry a new crane.
Installation, inspection and operation
Cranes should be installed by qualified personnel, tested as required by local rules, and inspected regularly, with records kept. Operators need proper operator training, and the people attaching loads need training in rigging. Never lift over people, and follow the manufacturer’s instructions and local regulations. Preventive maintenance of brakes, wire rope or chain, limit devices and electrics prevents most surprises.
A simple way to decide
Describe each lifting task: weight, path, frequency. If several tasks are scattered across a wide bay, a bridge crane is usually the natural fit. If lifts are concentrated at one workstation, a jib or workstation crane may be enough. If the work is outdoors or the building cannot carry a runway, a gantry is worth considering. When the answer is not clear, ask two or three qualified suppliers to propose solutions for the same written requirements, then compare the proposals. This article is general information, not engineering advice.