Most cable cleat inspection programmes end at "looks fine." Corrosion, vibration-induced loosening, and polymer ageing are all progressive processes — visually normal until they are not. By the time the degradation is obvious to a visual check, the cleat may no longer provide its declared short-circuit withstand. Structured inspection catches these processes in the recoverable phase.
§ 01 Five inspection dimensions
Corrosion condition
Check cleat body, bolts, and nuts for surface rust, pitting, or coating loss. On aluminium: white oxide and cratering. On stainless steel: crevice corrosion at bolt contact points and under liner edges (particularly 304 in coastal environments). On galvanised parts: zinc depletion and base-metal exposure.
Finding → Assess penetration depth. Surface treatment if minor. Replace if pitting exceeds ~20% of wall thickness or fastener threads are compromised.Fastener torque
Vibration progressively loosens bolts without producing visible displacement. Spot-check fastener torque with a calibrated torque wrench against installation records. Check for witness marks indicating rotation since last inspection.
Finding → Re-torque to manufacturer's specified value. If bolts cannot hold torque (thread degradation), replace fasteners and re-inspect surrounding cleats.Polymer ageing and cracking
PA66 nylon under combined UV, thermal cycling, and mechanical stress develops surface chalking, micro-cracks, and eventually brittle fracture. Check cleat body and liner for surface crazing, discolouration, or visible cracking — especially at stress concentrations near bolt holes and cleat edges. Low-temperature inspection (in winter) reveals brittleness not apparent at normal operating temperatures.
Finding → Any cracking: replace immediately. Chalked surface with no cracks: monitor and plan replacement at next scheduled maintenance.Cable sheath abrasion at cleat contact
Vibration causes micro-movement between cable and cleat liner; over time the liner or sheath abrades. High-vibration locations — near nacelle exit, at platform transition bends — are most vulnerable. Check the sheath at the leading and trailing edges of each cleat for indentation, scuffing, or material loss.
Finding → Surface indentation only: monitor. Sheath abraded through to insulation: isolate and assess insulation integrity (IR testing). Replace cable section if insulation is compromised.Cable displacement and span geometry
Check that cables remain centred within each cleat and that the span between adjacent cleats shows no visible sag or lateral bow. For trefoil installations, confirm all three conductors remain in the equilateral triangle arrangement. Displacement indicates prior fault loading, fastener failure, or cleat body damage.
Finding → Any displacement or loss of formation: investigate cause before returning to service. Replace damaged components and re-inspect the entire affected run.§ 02 Inspection intervals
- Onshore standard environments: annual full inspection including torque spot-check and visual assessment; comprehensive review at major service intervals;
- Offshore / coastal C5-M: six-monthly inspection minimum — corrosion rates are 5–10× onshore; annual intervals are not conservative enough for these environments;
- After any fault event: mandatory inspection before returning to service regardless of scheduled interval — see below.
§ 03 Post-fault inspection: mandatory, not optional
A short-circuit event subjects every cleat on the affected circuit to the rated electromagnetic impulse — and possibly beyond, if the fault occurred under conditions exceeding the system design level. Cleats can sustain internal cracking or permanent deformation that is not visible externally but eliminates their ability to withstand a subsequent fault.
§ 04 Record-keeping and trend analysis
Inspection records — location, check points, condition findings, actions taken, next recommended inspection — enable trend identification that single-visit assessments cannot. A cleat section showing faster corrosion than the tower average may indicate a local sealing failure or unexpected humidity source. Records also provide essential input for fault cause analysis when a subsequent failure occurs.
Inspection findings that reveal original specification or installation errors should be linked back to the selection and installation workflow. The corrective action taxonomy is in Installation Mistakes.