7.4 Cranes, Structures & Supporting Equipment

Cranes, Structures and Supporting Equipment

A crane is not just the hook and hoist. Its load travels through the lifting medium, drum or pocket wheel, trolley, bridge or jib, end carriages, rails, runway beams, connections, columns and foundations. Every element in that path must suit the rated load, dynamic effects and operating environment.

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Common Arrangements

Crane Motions

A bridge crane may have hoisting, cross-travel and long-travel motions. Controls must identify direction clearly from the operator's viewpoint. Travel paths, hook paths and end approaches must remain clear, and end stops or anti-collision devices are final protections rather than normal brakes.

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Supporting Structures and Load Paths

The rated payload is only part of the imposed load. Design and selection also consider:

• self-weight of hoist, trolley, bridge and accessories;
• acceleration, braking and skew forces;
• impact or hoisting dynamic factors;
• side loads, wind and outdoor exposure;
• wheel loads and their spacing;
• fatigue class and expected operating cycles;
• foundation bearing and anchor forces; and
• maintenance access and rescue arrangements.

For a pillar jib, the overturning effect grows with load × radius. A 2 t load at 5 m creates twice the payload moment of the same load at 2.5 m, before self-weight and dynamic effects. That is why the jib, column, base plate, anchors and concrete foundation form one engineered system.

Trolleys, Clamps and Tracks

A trolley must match the beam flange width and profile and be adjusted with the clearances required by its instructions. Anti-drop features reduce the consequence of wheel or axle failure, while end stops prevent travel off an open runway. A temporary beam clamp also depends on the suitability of the beam and correct installation; most clamps permit in-line loading only unless the manufacturer states otherwise.

Runway switches, turntables and transfer bridges must be fully aligned and locked before a trolley crosses. A small step or gap can shock-load the wheel and supporting structure.

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Deflection Is Design-Specific

Excessive deflection can cause trolley drift, alignment problems, poor load positioning and fatigue. Designers therefore control stiffness as well as strength. However, LOLER does not prescribe a universal L/500 limit. Different crane and runway standards, classes, load combinations and owner specifications can set different criteria.

A calculation question is valid only when it supplies the governing limit. If a design specification states L/500 for a 12,000 mm span, the permitted deflection is:

12,000 / 500 = 24 mm.

That arithmetic does not prove that L/500 governs another crane. The competent engineer must identify the applicable standard and design data first.

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Commissioning, Examination and Testing

Lifting equipment normally needs thorough examination before first use unless the Declaration-of-Conformity exception applies. Equipment whose safety depends on installation or assembly must be examined after installation and before use at that location.

Testing Boundary

HSE states that most lifting equipment does not need routine testing as part of every thorough examination and that overload testing can itself cause damage. Testing may be appropriate for manufacturer verification, installation, major alteration, repair, exceptional circumstances, or where the competent person needs it to support an examination.

The test load and method come from the applicable product or crane standard, manufacturer information, design and competent-person plan. Figures such as 1.25 static or 1.1 dynamic occur in particular contexts, but they are not universal LOLER factors. Never choose a test mass from memory.

Examination Scope

A competent-person examination may address:

• structure, welds, bolted joints, rails and anchors;
• hooks, ropes, chains, drums, sheaves and terminations;
• brakes, controls, emergency stops, limits and overload protection;
• trolleys, end carriages, wheels, buffers and anti-collision systems;
• electrical, hydraulic or pneumatic safety functions; and
• markings, reports, maintenance history and outstanding defects.

NDT is used where visual examination, history, deterioration mechanism or the examination scheme justifies it. It is not mandatory on every weld at every annual examination.

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Safe Operating Check

Before a lift, the operator checks the condition and function within their training: controls and direction, brakes, hook and latch, rope or chain, visible track, travel path, limits where required, and warning devices. Make a trial lift just clear, confirm balance and brake holding, then travel smoothly without dragging, side pulling or driving into end stops.

The lowest safe capacity in the complete configuration governs. A 5 t hoist on a 3.2 t runway is a 3.2 t system, subject to any further configuration or environmental derating.