Pre-Shift Inspection Findings on a Crawler Crane
At the start of a shift you walk the 150-ton crawler crane. You find: (1) the boom hoist wire rope has three broken wires in one lay over a 6-inch section near a sheave, plus some flattening; (2) the swing brake holds but the swing horn and travel alarm are intermittent; (3) the load moment indicator powers up but the boom angle readout disagrees with a hand-held inclinometer by 3 degrees; (4) the left track shows uneven pad wear and one pad is missing a bolt; (5) the fire extinguisher gauge is in the green but the inspection tag is 14 months old. The operator says the crane 'ran fine yesterday' and wants to start the day's lifts.
1. Which findings are stop-work items and which can be deferred, and why?
Read the worked answer
Stop-work / out-of-service items:
- Boom hoist rope damage: broken wires in one lay plus flattening near a sheave is a removal-from-service condition under wire rope inspection criteria. The boom hoist is a critical, non-redundant rope; failure is catastrophic. Tag out.
- LMI boom angle error of 3 degrees: the LMI is the primary overload protection. A 3-degree error changes the computed radius and therefore the capacity the system reports. It must be recalibrated/verified before lifting; an LMI that is inaccurate is treated as failed.
- Missing track pad bolt and uneven wear: a loose or missing pad can walk off and damage the track or cause derailment under load; inspect and repair before travel or lifting.
Deferrable with action:
- Intermittent swing horn/travel alarm: not a structural stop, but it is a communication/safety device; get it repaired before operating around personnel. Restrict operations until fixed.
- Fire extinguisher: gauge green but tag expired 14 months means it is due for inspection/service; swap it out today. Not a reason to stop the crane, but do it before work.
The operator's 'ran fine yesterday' is irrelevant; defects can appear between shifts.
2. The operator argues the broken wires are 'just three' and the LMI is 'close enough.' How do you handle it?
Read the worked answer
Hold the line and document. Explain that wire rope rejection is based on broken wires per lay in a specified length, and that the location near a sheave means the rope is subject to reverse bending and fatigue - the worst place to find broken wires. Flattening indicates core or strand damage that reduces strength beyond what the wire count alone shows. The manufacturer's criteria and the rope's history govern; 'three wires' is not a judgment you get to soften for schedule.
On the LMI: 3 degrees of boom angle error translates to a radius error that can be several feet at long boom, which can mean thousands of pounds of capacity error. 'Close enough' is not a category for overload protection.
Actions: remove the crane from service, notify supervision, tag the controls, record the findings, and require repair and re-verification (rope replacement, LMI calibration check against a known reference) before returning to work. If pressed, escalate to the lift director/site safety.