Derelict crane inspection, Cork

You can't assess it if you can't safely approach it

The crane was located at the end of a jetty in Cork - relatively modest in size compared to the large ship-to-shore container cranes at modern port facilities, but a structure that had been left exposed to the elements for years with no maintenance. Size is not what determines the hazard in that situation.

The client's concern was straightforward: the structure looked bad, and sending people in close without knowing the full picture was not acceptable. They needed that picture - a detailed, reliable understanding of the current condition of the crane - before they could safely plan the decommissioning work.

As Bob Foley, founder of Engineers With Drones, put it: "They were concerned that putting people close to the crane as it stood when we inspected it could be dangerous, so they decided to utilise a drone to get an idea of what they were dealing with before they approached it with the idea of removing it."

The high-optical-zoom camera

The key piece of drone technology for a job like this is the high-optical-zoom camera. This is a high-resolution sensor - at least 20 megapixels, in this case potentially up to 40 - paired with a long-focal-length lens, around 120mm, which translates to roughly 7x optical zoom in practical terms.

"That allows you to keep the drone away from the structure while still getting very high-resolution imagery," Bob explains. That matters a great deal when the structure you are inspecting is in an unknown structural state. You do not want the drone close to something that might shed material or partially collapse.

From a safe operating distance, the team was able to get detailed imagery of cable terminations, corroded fasteners, structural members, pivot points, and the condition of guard rails - all the critical elements of the crane that needed to be understood before any human approach.

What the inspection found

Context is everything in an inspection report. Showing a sheared bolt or a corroded joint in isolation tells you very little - you need to know exactly where it sits in the structure and what role it plays. Every image in the report was annotated and positioned relative to a structural diagram of the crane, so the client could immediately understand the significance of each finding.

The inspection covered all primary and secondary structural elements. The findings were classified by severity, with critical defects clearly flagged. Here is a summary of the major findings.

Cable condition

The drone was able to get right into cable terminations and fork connections, clearly showing the corrosion level on the cable strands. On the underside faces, biological growth was present. On the upper faces, the cables appeared cleaner but were still heavily corroded throughout.

Primary jib pivot

The primary pivot point for the jib is one of the most structurally significant components on the crane. The supporting structure around this pivot was found to be heavily corroded, with some elements close to corroding completely through. This was flagged as a critical finding.

Secondary support structure - critical-level defects

Flat horizontal surfaces had retained water over a long period. This caused significantly heavier corrosion on those horizontal faces compared to the vertical surfaces nearby. Several secondary structural members were found to be nearly corroded through. These were classified as critical-level defects due to the falling object risk they presented.

As Bob notes: "Some of these could be four or five hundred kilos of weight, steel beams, things like that. So you don't want that coming down." The presence of the drone, operating remotely, meant that none of the inspection team were exposed to that risk during the assessment.

Guard rails - no material remaining

Perhaps the starkest finding in the report concerned the guard rails. These are the rails that any person climbing the crane would have relied on to prevent a fall. They were found to be entirely gone as functional steel components. "What used to be a steel member is now almost entirely corroded. There is no core material left at all; it is effectively gone, and what remains is iron oxide."

To put it plainly: anybody who would have approached this crane and assumed the guard rails were safe had no idea of the actual condition of the structure. The drone inspection removed that uncertainty entirely.

Why decommissioning is not the simple part

There is a tendency to assume that taking something apart is less hazardous than operating something that is defective. In reality, decommissioning a structure in this condition is a skilled and genuinely dangerous operation. The people who do this work professionally know exactly how to cut, dismantle and lower structures like this without endangering themselves or anyone nearby. They are not using spanners and checking torques - they are using oxygen lances and cutting equipment, and the approach is entirely different.

Knowing the condition of the crane in detail - where the worst corrosion was, which components were at risk of sudden failure, where safe angles of approach existed - was exactly what allowed those specialists to do their job safely. That is what the report gave them.

Know before you go

"The primary thing that they gained from this particular report was knowledge of safety, knowledge of the structure as it stands right now and knowledge and insight on how they could go about decommissioning the crane."

With a full picture of the crane's condition, our client was able to identify the safe angles of approach, understand the specific hazards on the structure and hand that information over to the decommissioning team. Work that previously would have meant sending people in blind - or relying on binoculars from a distance - was now informed by detailed, classified, annotated imagery of every significant element of the crane.

Beyond the immediate safety benefit, the decommissioning also opened up the jetty again. With the unsafe crane structure safely removed, that area of the terminal could be brought back into use for vessels.

Fieldwork time: approximately two hours on site. Report in the client's hands: within 48 hours.