An overhead crane whose bridge travels along rails at roof level, carrying a hoist that moves across it.
01 / Definition
What a EOT Crane is
An EOT crane — electric overhead travelling crane — runs on rails fixed high along both walls of a bay. A bridge spans between those rails, a trolley runs across the bridge, and a hoist on that trolley raises and lowers the load. Together those three motions reach any point in the volume the bay encloses.
Each motion is its own drive: long travel moves the bridge down the bay, cross travel moves the trolley across it, and hoisting lifts. Each has a motor, a gearbox, a brake and limit switches. Most modern cranes run all three through VFDs, which matters more than it sounds — a load started or stopped abruptly swings, and a swinging load is both a safety problem and a source of structural fatigue.
Also called
02 / Anatomy
The parts that matter
The components a technician reaches for when this machine stops working.
Bridge girder and end carriages
The structural span and the wheeled assemblies that carry it along the runway rails.
Hoist and rope drum
Raises the load. The rope, drum grooving and sheaves are the parts with a defined inspection and discard standard.
Brakes
Each motion has one. The hoist brake is safety-critical and must hold the rated load with the power off.
Limit switches
Stop each motion before it reaches the end of travel. Hoist upper limits usually have a backup for exactly that reason.
Drives and panel
VFDs or contactor gear for the three motions, plus protection and the control circuit from the pendant or radio.
Long travel rails and wheels
Alignment and level here decide whether the crane skews, which is the root of most wheel-flange wear.
03 / Applications
Where it is used
Moving dies, coils, castings, machinery and raw material inside fabrication shops, foundries and warehouses.
04 / Failure modes
How it fails
What actually goes wrong on Indian shop floors, and what each fault looks like to the operator.
FM_01
Load drifting down when stopped
Hoist brake worn, oil-contaminated or out of adjustment. A safety-critical fault — the crane should be taken out of service until fixed.
FM_02
Crane skewing along the runway
One end carriage leading the other, from rail misalignment, uneven wheel wear or long-travel drives out of sync. It chews wheel flanges.
FM_03
Wire rope damage
Broken wires, birdcaging or corrosion. Rope condition is judged against a discard standard, not by appearance alone.
FM_04
Load swinging on start and stop
Direct-on-line starting, or VFD ramps set too aggressively for the span. Hard on the structure as well as unsafe.
FM_05
Limit switch failure
Lever bent or switch seized, so a motion runs past its stop. The backup upper limit is the last defence on hoisting.
05 / Onsite
What our technician checks
A methodical path to root cause, not a scattergun of part swaps.
- 01Lift a known load, hold it, and watch for any drift down — then inspect and adjust the hoist brake
- 02Inspect the full length of wire rope against the discard criteria, paying attention to the section at the sheave at the usual lift height
- 03Check wheel flange wear on all four corners and measure rail span and level at several points along the runway
- 04Test every limit switch, including the backup upper limit, by slow approach
- 05Check gearbox oil level and look for leaks at the output seals on all three drives
- 06Observe a full cycle for swing on start and stop, and review the VFD acceleration and deceleration ramps
06 / Get it fixed
Related services
The MachineryFix services that cover this equipment.
07 / Questions
Frequently asked questions
Why does the load drift down slightly when the hoist stops?+
The hoist brake is not holding, usually from worn linings, oil contamination from a leaking gearbox seal, or lost adjustment. This is safety-critical: the crane should be stopped and the brake inspected before it is used again.
What makes a crane skew as it travels?+
One end carriage advancing faster than the other, from runway rails out of alignment or level, uneven wheel wear, or the two long-travel drives not matched. Skewing wears wheel flanges and rail heads quickly, so the alignment should be measured rather than guessed.
How do I know when a wire rope needs replacing?+
Against a discard standard — number of broken wires in a given length, diameter reduction, corrosion, deformation such as birdcaging or kinks. A rope can look serviceable and still be past its limit, which is why a measured inspection matters.
Why do VFDs matter on a crane?+
They control acceleration and deceleration. A load started or stopped abruptly swings, which is unsafe to work near and fatigues the structure. Smooth ramps also reduce shock loading on gearboxes, brakes and wheels, so the whole crane lasts longer.
Written & reviewed by MachineryFix — last reviewed — questions? Call +91 70133 33007