On an insulated EWP the fibreglass is not just structure — it is the barrier that keeps electricity from reaching the operator and the machine. Insulated boom sections and fibreglass baskets are used precisely because they do not conduct, which is what lets crews work near live conductors on powerlines and utilities. That makes damage to the fibreglass a fundamentally different problem from a dent in steel: a scratch you can barely see can be the path that lets current across. This guide explains how fibreglass gets damaged, why the consequences are electrical rather than structural, and why the definitive check is a dielectric test, not a visual one.
How fibreglass damage presents
Damage to an insulating boom or basket includes:
- Surface scratches, gouges, chips and cracks in the gelcoat or laminate, which can breach the barrier or let moisture in.
- Crazing or a network of fine surface cracks, often from UV exposure and age, that can compromise the surface integrity.
- Contamination — dirt, grime, salt, oil or grease built up on the surface, which creates a conductive path across otherwise sound fibreglass.
- Delamination or soft, spongy areas where the laminate has broken down internally.
- Tracking marks — burnt or carbonised lines across the surface that show a current path has already been forming.
Why the damage matters so much
On a steel machine, a scratch is cosmetic. On an insulated boom or basket it can defeat the one feature the crew is relying on. The insulating property depends on the fibreglass presenting a clean, sound, dry surface; break that surface, let moisture in, or coat it with a conductive film and the barrier can no longer be assumed to hold.
This is why contamination is treated as seriously as physical damage. A layer of salty grime or oil across a perfectly intact boom can conduct just as effectively as a crack, and neither is safe to work behind near live conductors.
Why testing, not looking, is the real check
You cannot judge insulation by eye. A boom can look flawless and still fail electrically because of moisture ingress, internal breakdown or contamination you cannot see, and a boom with a visible scratch might still pass — or might not. The only way to know is to test it.
Insulated machines are subject to dielectric (electrical) testing, in which the insulating sections are subjected to a defined voltage and the leakage current is measured against the acceptance criteria for that class of machine. This testing is carried out at defined intervals and after any event that could have affected the insulation, and it is separate from — and additional to — the structural inspection regime that every EWP follows under AS 2550.10.
What happens when damage is found
The response to fibreglass damage depends on what testing and assessment reveal, and it is driven by the electrical result, not just the appearance.
- Contamination is cleaned off with the correct method so the true condition of the surface can be assessed and tested.
- Minor surface damage may be repairable to restore the insulating surface, but only where the repair and subsequent testing confirm the barrier is sound.
- Damage that has compromised the insulating integrity means the section fails and the machine cannot be used insulated until it is put right or the component is replaced.
- Any repair is proven by re-testing, because a repair you cannot verify electrically is no repair at all on an insulated machine.
Protecting the insulation
Keeping insulated fibreglass clean and dry is the day-to-day priority — regular, correct cleaning removes the conductive films that quietly defeat the barrier. Storing the machine out of prolonged UV where practical slows the crazing that comes with age, and careful operation avoids the knocks and gouges that breach the surface.
Above all, dielectric testing is not a discretionary extra — it is the mechanism that proves the insulation still does its job. If an insulated boom or basket is damaged or contaminated, treat it as out of service for insulated work until it has been tested and cleared.
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.