Crane Skews While Travelling

Measure the runway before replacing the crane — that is usually where the problem is.

Safety: The checks below are meant to help with diagnosis. Work on the electrical panel, brake adjustment, rope/chain and safety components must be carried out by competent personnel, with power isolated and lockout–tagout rules followed. A faulty crane must not be run under load until diagnosis is complete.

Why it happens

A crane travels on two runways, driven from both sides. When the speeds of the two sides are not equal, or the runway geometry is out of tolerance, the crane runs at an angle to the runway; this is called skewing.

A skewing crane advances with its wheel flanges rubbing against the sides of the rail. The result: flange wear, increased friction, higher current on the travel motors, and torsional stress on the structure.

Possible causes

Possible cause	How to identify it
Span deviation	Measured span is not constant along the runway
Misalignment	The rail is visibly curved in plan; drift increases at a certain point
Level difference between rails	Rail top levels differ at the same cross-section
Wheel diameter mismatch	Measured diameters differ on opposite wheels
Drive imbalance	Motor currents on the two sides are noticeably different
Brake timing	One side engages earlier/later than the other
End carriage deformation	Diagonal measurements are not equal

Step-by-step diagnosis

Locate where the drift occursNote where along the runway it increases.
Check the flange wearWhich side and which direction is worn tells you the direction of drift.
Measure the runwaySpan, level difference, straightness — at regular intervals.
Measure the wheel diametersCompare the diameters of opposite wheels.
Compare the motor currentsMeasure the travel currents on both sides, loaded and unloaded.
Check brake releaseDo the brakes on both sides open simultaneously.
End carriage diagonalTake a diagonal measurement to check for deformation or a mounting error.

Lasting fix

A lasting fix almost always starts with measuring and aligning the runway. Span, level and straightness are recorded at regular intervals along the runway; the deviations are written up in an alignment report.

Once the runway is corrected, wheel diameters are compared. If there is a wear difference, the wheels are assessed as a set — replacing a single wheel creates a new diameter mismatch.

Finally, the travel motor currents and brake release timing on the two sides are compared. On VFD-driven systems, the synchronisation parameters are reviewed.

Technical terms

Term	What it means
Skewing	The crane advancing at an angle to the runway.
Span deviation	The distance between the two rail centrelines changing along the runway.
Diagonal measurement	A cross measurement used to check whether the end carriages are square.
Guide roller	A roller that provides lateral guidance instead of a flange.

Frequently asked questions

Can't I just replace the wheel?

It eases the symptom short term, then it comes back. If the runway is out of tolerance, the new wheel wears the same way.

How long does runway measurement take?

It depends on the length of the runway; measurement and reporting is usually completed within a day. The alignment work itself varies with the size of the deviation.

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