Overhead Crane (EOT) Explained: Types, Design and Safety

An overhead crane, often called an EOT crane (electric overhead travelling crane), runs on rails fixed high along the sides of a building and carries a hoist across the span between them. It is the standard lifting system in factories, warehouses, steel fabrication shops, power stations and workshops. For a structural engineer, it is also one of the most demanding loads a building can carry, because the crane’s forces move, repeat and act in three directions.

This guide explains how overhead cranes work, the main types, what they require of the building structure, and the lifting framework in Singapore, from the Workplace Safety and Health (Operation of Cranes) Regulations 2011 to the examination of lifting machines and the Singapore Standard for overhead travelling cranes.

How an overhead crane works

An EOT crane has three main motions, each driven by electric motors:

Long travel: the bridge, spanning the building, runs along runway rails mounted on crane girders at each side.
Cross travel: a trolley carrying the hoist runs along the bridge.
Hoisting: the hoist raises and lowers the hook using wire rope or chain.

Together, these motions let the hook reach almost any point in the building’s floor area below. Control is by pendant, radio remote or, on larger cranes, a cab. Limit switches stop travel at the ends of the runway and prevent the hook block being drawn into the hoist, and overload protection cuts the hoist when the rated capacity is exceeded.

Main types of overhead crane

Single-girder cranes

A single bridge beam carries an underslung hoist running on its bottom flange. Single-girder cranes are lighter, simpler and cheaper, and suit lighter loads and moderate spans.

Double-girder cranes

Two bridge beams carry a trolley running on rails on top. Double-girder cranes offer higher capacity, longer spans and more hook height, because the hoist sits between or above the girders.

Top-running and under-running

Top-running cranes sit on rails on top of the runway girders, the usual arrangement for heavier cranes. Under-running or underhung cranes hang from the bottom flanges of runway beams, often suspended from the roof structure, and suit lighter loads in buildings without crane columns.

Related systems

Monorail hoists run along a single beam on a fixed path. Workstation cranes are light, modular systems for assembly areas. A gantry crane works on the same principle but carries its own legs down to the ground, and a jib crane serves a circular area around a pillar or wall.

What an overhead crane demands of the building

When a building is designed for an overhead crane, the crane loads shape the structure. This is where many problems begin: cranes are added to buildings that were not designed for them, or upgraded to a higher capacity without checking the structure.

Crane loads

Vertical wheel loads: the self-weight of the crane plus the lifted load, concentrated at the end carriage wheels and greatest when the trolley is at one end of the bridge.
Dynamic effects: hoisting and sudden release of loads increase the effective wheel loads, accounted for by dynamic factors.
Horizontal transverse forces: trolley acceleration and braking, and the crane skewing as it travels, push sideways on the rails.
Longitudinal forces: acceleration and braking of the whole crane along the runway.
Buffer forces: impact at the ends of the runway.

Runway girders, columns and fatigue

Crane runway girders are typically steel beams on column brackets or stepped columns, designed for bending, lateral torsional buckling, local wheel load effects in the web and, critically, fatigue. Every pass of a loaded crane is a load cycle, and over decades the welds and details at the top flange can crack. The design must also limit deflections and keep the rails aligned, because misalignment causes skewing, wheel wear and higher horizontal forces.

Columns and foundations must resist the crane’s vertical and horizontal loads together with wind and other actions. Installing a crane in an existing building, or increasing its capacity, therefore needs a structural assessment and usually Professional Engineer involvement. Our article on steel structure consultancy in Singapore describes what that review typically covers.

Where the overhead crane is used

On a building project, the crane itself is usually part of the finished building rather than a construction tool: it is the client’s equipment for operating a factory or workshop. During construction, the crane is installed after the structure is complete, then tested and registered before use. In precast and steel fabrication facilities that supply construction projects, overhead cranes move materials through every stage of production.

Singapore lifting and safety requirements

Regulations, plans and supervision

The Operation of Cranes Regulations apply to any workplace in which a crane is in use, and their definition of a crane covers machines that move suspended loads beneath an elevated structural member. The responsible person must establish a lifting plan and must appoint a lifting supervisor, trained through a course acceptable to the Commissioner and with at least one year of relevant experience, before any lifting operation involving a crane. Routine, repetitive lifts may be covered by a basic lifting plan, as the WSH Council’s code describes, with additional planning for unusual or heavy lifts.

Standard

SS 497 is the Singapore Standard code of practice for the design, safe use and maintenance of gantry cranes, overhead travelling cranes and monorail hoists. The WSH Council’s Code of Practice on Safe Lifting Operations includes a sample checklist for overhead travelling cranes.

Registration and examination

Overhead cranes are lifting machines that must be registered with MOM before use and tested and examined by an Authorised Examiner, an MOM-approved Professional Engineer. Under the revised requirements effective 12 September 2025, fixed cranes and other lifting machines are examined at least every 12 months, with overload tests required at first registration or re-registration rather than periodically. Lifting gear such as slings and shackles must also be re-examined periodically.

Operational hazards

Workers struck by loads or the crane’s travel, controlled by clear floor routes, warning devices and keeping people out from under loads.
Falls during maintenance on the runway, needing safe access and fall protection.
Electrical hazards from conductor rails, requiring isolation before work.
Operators who are not trained for the specific crane; operators should be trained and competent.

If you are adding a crane to an existing building or upgrading its capacity, our structural engineering consultancy can assess the structure.

Frequently asked questions

What does EOT crane mean?

EOT stands for electric overhead travelling crane, a bridge crane driven by electric motors that runs on elevated rails along the sides of a building and carries a hoist across the span.

What is the difference between single-girder and double-girder overhead cranes?

A single-girder crane has one bridge beam with an underslung hoist and suits lighter loads, while a double-girder crane has two beams with a trolley on top, giving higher capacity, longer span and more hook height.

Can an overhead crane be added to an existing building?

It can, but the columns, runway girders, connections and foundations must be assessed for the crane’s vertical, horizontal and fatigue loads, which usually requires a Professional Engineer.

Why is fatigue important for crane runway girders?

Each pass of a loaded crane is a load cycle, and over many years repeated stress at welds and top flange details can cause fatigue cracking, so runway girders must be designed and inspected with fatigue in mind.

How often must an overhead crane be examined in Singapore?

Under MOM’s revised requirements from 12 September 2025, fixed cranes and other lifting machines are tested and examined by an Authorised Examiner at least once every 12 months.

Adding or upgrading a crane in an existing building? Talk to our consultancy or get in touch.