Fixed steelwork on a mine site — conveyor gantries and trestles, bins and chutes, screen and crusher support structures, access platforms, walkways and stairs — carries dynamic loads, vibration and abrasive material in a corrosive environment, often for decades past its original design intent. Failures are structural collapses and falls from height, and both are foreseeable with a disciplined inspection program.
We inspect fixed structures and access systems against AS 4100, AS 3990 and AS 1657, combining visual and dimensional inspection with UT thickness measurement and MT of critical connections, and report condition by member so maintenance can be prioritised.
Inspection checklist areas
- Primary structure
- Columns, beams, trusses and bracing for corrosion section loss (UT thickness), deformation, impact damage, missing members and unauthorised modification or removal of bracing.
- Connections
- Bolted connections for missing, loose or corroded bolts and slotted holes; welded connections for cracking by visual and MT at gusset, cleat and splice welds; base plates, hold-down bolts and grout.
- Conveyor structures
- Stringer and gantry welds, trestle legs and bracing, drive and take-up frames, idler frame mounts, guarding and nip-point protection to AS/NZS 4024.3610 and AS 1755 practice.
- Bins, chutes and liners
- Shell and hopper plate thickness, stiffener and support welds, liner wear-through, build-up loading, support skirt and column connections.
- Walkways, platforms and stairs (AS 1657)
- Grating condition, fixing clips and support, handrail and midrail height and integrity, kickplates, stair tread and stringer condition, landing and gate function.
- Ladders and fall protection
- Fixed ladder rungs, stiles and cage condition to AS 1657, landing intervals, fall-arrest anchorages and static lines to AS/NZS 1891 and their certification tags.
Known failure modes
Corrosion section loss
Wall thinning at member bases, under spillage and at water traps, reducing capacity below design.
Fatigue cracking at connections
Cracks at welded gusset, cleat and stringer connections under vibration from conveyors, screens and crushers.
Overload from build-up
Accumulated spillage and material build-up on gantries, bins and platforms exceeding the design live load.
Grating and handrail failure
Corroded grating bearer bars, missing clips and rusted stanchion bases causing falls through or over the edge.
Connection bolt loss
Bolts loosened by vibration or lost to corrosion, leaving connections partially engaged.
Applicable standards and regulations
| Reference | Title | Relevance |
|---|---|---|
| AS 4100 | Steel structures | Design basis for strength, serviceability and fatigue assessment of steel structures. |
| AS 3990 | Mechanical equipment — Steelwork | Design basis for machine support steelwork and plant structures. |
| AS 1657 | Fixed platforms, walkways, stairways and ladders — Design, construction and installation | Dimensional and construction requirements for access systems. |
| AS/NZS 1554.1 | Structural steel welding — Welding of steel structures | Weld quality and acceptance criteria for structural connections. |
| AS/NZS 1891 series | Industrial fall-arrest systems and devices | Anchorage and static line requirements where fall protection is provided. |
| AS/NZS 2312 | Guide to the protection of structural steel against atmospheric corrosion | Basis for assessing coating condition and remaining protection. |
| AS/NZS 4024.3610 and AS 1755 | Safety of machinery — Conveyors; Conveyors — Safety requirements | Guarding and nip-point protection on conveyor structures. |
When to inspect
- Periodic structural condition survey, commonly annual for critical structures
- Visible corrosion, deformation, cracking or grating failure
- Change of loading, additional equipment mounted on a structure, or bracing removed
- After impact by mobile plant, overload or seismic or storm events
- Life extension or shutdown planning for ageing plant
Frequently asked questions
How is corrosion loss on steelwork assessed?
By UT thickness measurement at representative and worst-case locations, compared with the original section and the minimum required for the design load. Members below the required thickness are reported with location, remaining section and a recommendation for repair, replacement or load restriction.
What does AS 1657 require for walkways and handrails?
AS 1657 sets requirements for walkway width, grating and its fixing, handrail and midrail heights, kickplates, stair rise and going, landing intervals and ladder construction including cages. The inspection reports non-compliances and defects such as loose grating, missing clips and corroded stanchions that create a fall risk.
Do you inspect conveyor guarding as part of the structure?
Guarding and nip-point protection are recorded where they are attached to the structure under inspection, referenced to AS/NZS 4024.3610 and AS 1755, because missing guards are a frequent finding and a serious hazard.
Can a structure keep operating past its design life?
Often, if a condition survey confirms remaining section and connection integrity and an engineering assessment sets a monitoring regime. Our inspection provides the condition data; the engineering assurance service provides the assessment.