The 5-year major inspection on an elevating work platform is significantly more involved than the 6-monthly in-service check. Here is what AS 2550.10 requires, what the structural and mechanical checks involve, and — for insulated booms — what the acoustic emission and high voltage tests are actually doing.
Why the Major Is Different
The 6-monthly in-service inspection is a functional and visual check. The operator confirms that controls work, safety devices activate, structural members are undamaged, and the machine is fit for the next six months of operation. It is important, but it is not a deep inspection.
The 5-year major is a systematic assessment of the machine's structural integrity, mechanical condition, and — where applicable — electrical insulation. It goes further than anything that can be done visually during a 6-monthly, and it requires NDT, load testing, and specialist electrical testing that the 6-monthly does not.
Structural Checks
The structural inspection covers all primary load-bearing members — boom sections, turntable, chassis, and outrigger assemblies. The inspector looks for:
- Cracks in boom sections, particularly at stress concentration points — pivot connections, cylinder attachment points, and section joints
- Deformation, dents, or section loss that was not present or not documented at the previous major
- Weld condition on fabricated components — visual inspection at minimum, with MT or PT on welds in high-stress locations
- Corrosion, particularly in hollow sections where moisture accumulates and is not visible externally
- Pin and bush wear in all articulation joints
For boom-type machines, UT thickness measurement may be required on hollow sections where corrosion is suspected but not visible.
Mechanical Checks
The mechanical inspection covers the hydraulic system, drive system, slew ring, and all safety devices:
- Hydraulic cylinder condition — seals, rods, and end fittings
- Slew ring condition and backlash measurement
- Load sensing and overload protection systems
- Platform levelling system function and adjustment
- Emergency descent and lowering systems
- Limit switches, interlocks, and outrigger load monitoring
The machine is function-tested under load at the rated capacity, and the rated load test is documented.
Acoustic Emission Testing — Fibreglass Booms
For insulated boom machines — boom lifts used in live-line electrical work — the insulating section of the boom is a fibreglass composite component. Over time, fibre fractures, delamination, and moisture ingress can degrade the structural integrity of the fibreglass without any visible external sign.
Acoustic emission testing (AET) to AS 4748 is the required method for assessing fibreglass boom integrity. The boom is loaded while acoustic sensors attached to the fibreglass section listen for the characteristic high-frequency sound of fibre fracture or delamination propagating under stress. The results are plotted and assessed against the acceptance criteria in AS 4748 — a boom that emits significant acoustic activity under load has internal damage that cannot be seen but can be detected.
This test cannot be substituted with visual inspection. It is a mandatory part of the major for any fibreglass insulated boom.
High Voltage Testing — Bucket Liners and Boom Insulation
For machines used in live-line electrical work, the insulation system must be electrically tested at each major and at 6-monthly intervals. DEG Calibration & Compliance carries out HV testing to ANSI/SIA A92.2:
- Bucket liner dielectric test — the liner is filled with water and a test voltage is applied to confirm the liner is intact
- Boom insulation test — the full insulation system of the boom is tested at the rated proof voltage for the machine's insulation class
The leakage current is measured and compared against the acceptance criteria. A liner or boom section that fails the dielectric test must be removed from service immediately — it is not a maintenance issue, it is a safety-critical failure.
What the Certificate Must Contain
The major inspection certificate must reference AS 2550.10, document all checks performed, record the results of any NDT and load testing, and — for insulated machines — reference the AET and HV test results and their standards. Certificates that do not contain this level of detail are not compliant with the standard.
DEG carries out 5 and 10-year EWP majors nationally, including structural NDT, AET to AS 4748, and HV testing to ANSI/SIA A92.2.
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