NDT Methods for EWPs and Cranes: A Complete Guide

Why NDT matters for lifting and access equipment

EWPs and cranes are fatigue-loaded structures. Every lift, every boom extension, every slew cycles the steel through stress ranges, and over thousands of cycles microscopic flaws at welds and pin bores can initiate cracks. These cracks propagate slowly and silently. By the time a crack is visible to the naked eye it is often well advanced, and in high-consequence components that can mean very little margin remains before failure.

NDT lets an engineer detect these flaws early, quantify them and make an informed decision about repair, monitoring or withdrawal. It is the difference between an inspection that confirms a machine 'looks fine' and one that verifies the load-bearing structure is genuinely sound. On cranes and EWPs the stakes are high because failure of a boom or pin puts people at height directly at risk.

Visual inspection: the essential first step

Visual inspection is the foundation of all NDT. A trained inspector examines welds, coatings and structure under good lighting, often aided by magnification, gauges and reference standards. It detects surface cracking, corrosion, distortion, weld undercut, poor profile and evidence of overload or impact.

Its limitations are obvious: it cannot see beneath the surface or through coatings, and fine tight cracks can be missed. But visual inspection guides everything that follows. It tells the engineer where to focus the more sensitive methods and it catches the gross defects that instrumented techniques might not even be applied to. Visual weld inspection to a recognised acceptance standard is a service in its own right, not merely a preliminary.

Magnetic particle inspection

Magnetic particle inspection (MPI or MT) is the workhorse for ferromagnetic components such as steel booms, welds, pins and machined bores. The part is magnetised and fine iron particles are applied; where a surface or near-surface crack disrupts the magnetic field, the particles gather at the flaw and make it visible, often under ultraviolet light with fluorescent media.

MPI is fast, sensitive to the tight surface cracks that fatigue produces, and well suited to the weld toes and pin bores where EWP and crane cracks concentrate. It requires a clean surface and works only on magnetic materials, so it cannot be used on aluminium or stainless components. For steel weldments it is usually the first-choice surface method during a major inspection.

• Best for steel welds, pins and machined bores
• Detects surface and slightly sub-surface cracks
• Fast and highly sensitive to fatigue cracking
• Cannot be used on non-magnetic materials

Dye penetrant testing

Dye penetrant testing (DPT or PT) works on any non-porous material, making it the go-to surface method for aluminium platforms, stainless components and non-magnetic castings where MPI cannot be used. A coloured or fluorescent dye is applied and drawn into surface-breaking flaws by capillary action; after excess dye is removed, a developer draws the dye back out to reveal the flaw.

It detects only surface-breaking defects, and surface preparation and cleanliness are critical to a reliable result. Where a component is aluminium or the crack must break the surface to matter, dye penetrant is simple, portable and effective. It is frequently used alongside MPI so that mixed-material assemblies are fully covered.

Ultrasonic testing

Ultrasonic testing (UT) sends high-frequency sound into the material and interprets the echoes. It excels at detecting sub-surface flaws such as internal weld defects and laminations, and it is the primary method for measuring remaining wall thickness where corrosion has eaten into a member from the inside or beneath coatings.

On EWPs and cranes, UT is used to verify thickness in boom sections and chassis members suspected of internal corrosion, to examine thick full-penetration welds, and to assess pins and shafts. It requires skilled operators and good coupling to the surface, and interpretation is more subjective than a surface method, so operator competency is essential. Advanced variants such as phased array extend its capability on complex welds.

Eddy current testing

Eddy current testing (ET) induces electrical currents in a conductive material and detects the disturbance a crack causes. Its great advantage is that it can find surface and near-surface cracks through thin coatings and paint, which is valuable where stripping the coating is impractical or undesirable.

On lifting equipment it is often applied to bolt holes, fastener regions and coated surfaces, and it is well suited to inspecting fastener holes for fatigue cracking without disassembly. It works on conductive materials including aluminium, complementing the magnetic-only reach of MPI. Like UT, it demands trained operators and appropriate reference standards to calibrate against.

• Detects cracks through thin coatings without stripping paint
• Works on conductive non-magnetic materials such as aluminium
• Well suited to fastener and bolt-hole inspection

Choosing the right method for the job

No single method covers every situation, which is why a competent inspection uses a considered combination. The engineer selects methods based on the material, the geometry, the likely defect type and the consequence of failure. A steel boom weld is a natural candidate for MPI; an aluminium platform for dye penetrant; a corroded chassis member for ultrasonic thickness measurement; a coated bolted joint for eddy current.

Just as important is who performs the work. NDT should be carried out and interpreted by personnel certified to a recognised scheme such as AS 3998, working to defined procedures and acceptance criteria. The results must be documented with the method, technique, locations examined and findings, so that they can be relied upon in the engineering report and, if needed, in an investigation.

NDT in the wider inspection and investigation process

During a major inspection, NDT is applied to the critical components identified by the engineer and the manufacturer's data, and the results feed directly into the recertification decision. In an incident or failure investigation, NDT helps establish whether a crack pre-existed the event, how far it had propagated and whether it originated at a weld defect, a design detail or corrosion.

For owners, the key point is that NDT is not an optional extra bolted onto a visual inspection; it is what turns an inspection into genuine engineering verification. When commissioning inspections, ask which methods will be applied to which components and confirm that certified personnel will carry them out.