IOGP high potential event report

Incident description:

During a routine Area Operator surveillance round, detached and broken PVC/FRP cable tray cover sheets were found in different locations on the south side of seawater cooling towers on the ground floor, in a U-ditch, and on top of the cooling tower. It is suspected that heavy winds during the day caused the cover sheets to become detached and fall from the top of the cooling towers from a height of approximately 30m. All operation staff were alerted and a notification was raised.

What Went Wrong:

Object weight approx. 20kg / Dimensions approx.. 1m x 2.7m. Object material: PVC/FRP (marine specification). Clamps are fixed approximately every 2.5m at the edges of the cable tray cover sheets. Clamps were found to be loose in most of the locations. Heavy winds were observed on the day of incident.

Corrective Actions:

The clamps and fixing arrangements were not robustly designed and performed poorly when high wind conditions caused vibration. The clamp bolt is a friction hold clamp which does not penetrate the PVC/FRP cover sheet. Friction hold clamps should not be used with PVC/FRP cover sheets. Each clamp had only one bolt. The clamp selection was decided by the subcontractor according to manufacture preference. Be alert to objects being unexpectedly detached and falling to the ground during high winds. Provide double stainless steel straps, a minimum of 3 per cover sheet, and remove the clamps to avoid the hazard of Falling Objects. Inspect the Cooling Towers for similar types of covers and clamps. Specifications are to be updated to include a statement about avoiding use of friction hold clamps for PVC/FRP cable tray cover sheets.