Rotary Drilling Rig Main Winch Kept Crushing Wire Rope: Finding the Hidden Drum Misalignment

Wire rope is a wear item, but rapid and repeated rope destruction is not normal wear. In this field case, the main winch pinched the rope during every winding cycle. Friction became severe enough to produce sparks, and a newly installed rope became unusable after less than 200 metres of drilling work.

Replacing the rope again would have restored appearance without removing the load that was damaging it. The inspection therefore focused on rope geometry: the relationship among the winch drum, the main sheave, and the end support that keeps the drum aligned.

This article is adapted from the supplied service report and its two site photographs. It preserves the observed failure pattern, inspected components, confirmed broken fasteners, and repair result while removing personal and internal service information.

A New Rope Failed Far Too Quickly

During main-winch hoisting, the rope pinched each time another wrap formed on the drum. The report notes that this did not resemble the more familiar occasional crossover or localized rope bite. The problem repeated with every drum revolution, indicating a persistent geometry or support problem rather than a single poor winding event.

Severe rubbing sometimes produced visible sparks. Most importantly, the replacement rope did not survive normal service: after less than 200 metres of drilling work it had already reached the point where it had to be discarded. Those facts justified stopping the cycle of rope replacement and inspecting the winch structure.

• The rope pinched during every winding cycle.
• Friction was severe enough to produce sparks.
• A new rope became unusable after less than 200 metres of drilling work.
• The repeated pattern suggested a stable mechanical misalignment.

Fleet Angle Connected the Symptom to Winch Geometry

The report attributes the rope-to-rope friction to an excessive fleet angle as the rope entered the drum. When that angle is wrong, the rope cannot settle into the expected winding path. It is pushed sideways, rubs adjacent wraps, and creates concentrated damage even when the rope itself is new.

Three possible mechanical sources were listed: a problem with the drum, excessive wear in the main-sheave groove, or a failed end-bearing support. This was a useful inspection order because each item could change the drum-to-sheave relationship without producing the same visible damage at first glance.

• Inspect the rope path rather than judging only the damaged rope.
• Compare drum alignment with the sheave centreline.
• Check the sheave groove for abnormal wear that could steer the rope.
• Inspect the drum end support and its fasteners for lost position.

The Sheave Was Acceptable, but the Drum Was Not Straight

The main-sheave groove was checked first. Its wear remained within the acceptable range recorded by the field team, so the sheave did not explain the extreme and repeated rope damage. The drum itself was also examined and was considered serviceable, but its position was visibly skewed.

That observation shifted attention from the drum surface to the structure holding the drum in position. A serviceable drum can still wind rope incorrectly if its bearing support moves. The drum misalignment therefore became the key physical clue leading to the end-bearing mount.

• Main-sheave groove: inspected and within the accepted wear range.
• Drum condition: no confirmed drum-body failure in the report.
• Drum position: visibly misaligned relative to its intended axis.
• Next inspection point: the end-bearing support and retaining hardware.

Eight Broken Retaining Bolts Allowed the Drum to Shift

When the end-bearing area was opened, the technicians found that all eight retaining bolts securing the end bearing had broken. With the support no longer fixed in its designed position, the drum could sit at an angle. That mechanical shift changed the fleet angle and forced the rope into repeated side contact during winding.

The broken fasteners were replaced and the end support was reassembled. After reassembly, the main winch returned to normal operation and the rope-crushing symptom disappeared. The repair result matched the diagnosis: restoring the drum support corrected the rope path rather than merely installing another consumable rope.

• Confirmed finding: eight retaining bolts at the end-bearing mount were broken.
• Mechanical effect: the unsupported end allowed drum misalignment.
• Repair: replace the broken fasteners and reassemble the end support.
• Verification: normal winch operation returned and abnormal rope pinching stopped.

How to Inspect a Used Rig's Main Winch

A clean or newly fitted rope does not prove that the main winch is healthy. During a used-rig inspection, observe several complete winding layers under controlled conditions. Look for sideways rope movement, uneven gaps, sudden crossover, polishing on one side of the rope, abnormal noise, and any movement at the drum supports.

Ask why the rope was replaced and how long the previous rope lasted. If there is a history of rapid damage, request photographs of the sheave groove, drum surface, bearing supports, and mounting fasteners. After repair, obtain a continuous operation video showing smooth winding and stable drum alignment rather than only a stationary photograph of the new rope.

• Treat unusually short rope life as evidence of an underlying mechanical cause.
• Inspect both rope condition and the geometry that controls winding.
• Check support fasteners and bearing mounts for movement or previous repair.
• Verify the completed repair through repeated winding under a safe test condition.

Repair the Cause, Not the Rope

The important repair in this case was not another wire-rope replacement. It was identifying why a new rope was being forced into destructive contact. The acceptable sheave condition, visible drum misalignment, and eight broken retaining bolts formed a consistent chain of evidence.

Kepler Machinery applies this kind of mechanical inspection when evaluating used rotary drilling rigs for export. Buyers receive more useful information when a visible wear item is connected to its root cause and the repair is verified in operation.

Safety Note

Main winches and wire ropes store substantial energy and can move without warning. Inspection, disassembly, lifting, fastener replacement, and operational testing must be carried out by qualified personnel with the machine isolated, components properly supported, and the manufacturer's service and torque requirements available.