Non-destructive testing (NDT) is the reason a major inspection can genuinely say a boom is sound rather than merely 'looks sound'. NDT lets an inspector find cracks and flaws in welds, pins and structural members without cutting the machine apart. Because AS 2550.10 treats critical components as those whose failure would create a risk to safety, understanding how these methods work — and why visual inspection alone falls short — is worth any owner's time.
Why the eye is not enough
The most dangerous defects on an EWP are the ones you cannot see. Fatigue cracks in a highly-stressed weld often begin sub-surface or as a hairline barely wider than a scratch, hidden under paint, grease or a coating. A member can look perfect and still be growing a crack that will one day propagate under load.
A visual inspection remains essential — it catches obvious damage, corrosion and gross deformation — but for critical welds and components it is a starting point, not a verdict. NDT is what turns 'no visible damage' into evidence that the structure is intact.
Magnetic particle testing
Magnetic particle testing (often shortened to MPI or MT) is used on ferromagnetic steel — which covers most of an EWP's structure. The area is magnetised and fine iron particles are applied; where a surface or near-surface crack interrupts the magnetic field, the particles gather at the flaw and make it visible.
It is a natural fit for:
- Critical welds along the boom and at boom-section joints.
- Structural connections, brackets and lugs where fatigue cracking tends to start.
- Pins and shafts once removed, to check for surface cracking.
- Any steel component where surface and near-surface flaws are the concern.
Dye penetrant testing
Dye penetrant testing (PT or DPI) works on the surface only, but it works on materials that magnetic particle testing cannot — including non-ferrous metals such as aluminium components and stainless fittings. A coloured or fluorescent dye is drawn into any surface-breaking flaw by capillary action; after cleaning, a developer pulls the dye back out and the defect shows as a bright indication.
On an EWP it is commonly used on aluminium or non-magnetic parts and on machined surfaces where surface-breaking cracks are the risk. Its limitation is that it only reveals flaws that break the surface — it cannot see below it — so it is chosen for the material and location rather than as a universal tool.
Ultrasonic testing
Ultrasonic testing (UT) is a volumetric method: it sends high-frequency sound into the material and reads the echoes to detect flaws below the surface and to measure thickness. Where magnetic particle and dye penetrant look at the surface, ultrasonic can look inside.
On an EWP it earns its place for:
- Sub-surface flaws in thick structural sections and full-penetration welds.
- Pins, shafts and axles where an internal defect would never reach the surface to be seen.
- Measuring wall thickness to assess corrosion or wear from the inside.
- Confirming the integrity of critical load-bearing members that carry the machine's stresses.
The right method in the right place
No single method does everything. A competent major inspection provider selects the technique to suit the material, the location and the type of flaw being looked for — magnetic particle for surface and near-surface cracks in steel welds, dye penetrant for surface flaws including non-magnetic materials, and ultrasonic for buried defects and thickness. Often more than one is used across the same machine.
The value of NDT lies in both the testing and the interpretation. The reports it produces become part of the machine's compliance history and are the documented basis for certifying that critical welds and components are fit to remain in service.
This guide is general information prepared by EWP Australia and is grounded in publicly available Australian Standards and Safe Work Australia material. It is not a substitute for the current published edition of the relevant standard or for site-specific engineering advice. Always work from the current standard and consult a competent person for your specific equipment and application.