Poor quality control during fabrication of a gangway resulted the failure of a pin at a gimballed joint which resulted in the gangway falling 14 metres into water below. Had anyone been on the gangway there would, almost certainly have been multiple fatalities or serious injuries.
Although this was an offshore incident similar hazards may exist on other access structures.
A critical weld that would have strengthen a pin was omitted.
An incorrect grade of pin was used.
Slings and chain connecting the gangway to the landing platform were too long to prevent the structure being dislodged.
Slings and chain were of inadequate strength.
Says OGP: “A purpose built project modular gangway for jacket access from a construction barge parted at the jacket end and fell into the water. To allow for movement of the construction barge the gangway had a roller support at the barge end and was supported by a gimballed joint at the platform end. The failure occurred in the vertical pin of the gimballed joint.
The gangway collapsed into the sea
What Went Wrong?:
Investigation determined that a weld around the centre of the pin was omitted during the fabrication process, which would have increased the stress levels in the pin. It was further determined that the incorrect grade of for the pin was ordered, although the yield stress of the steel was as specified in the design.
Although slings and chains were placed on the gangway and connected to the landing platform they were too long to prevent the gangway from dislodging from the landing platform and of insufficient strength to withstand the impact loads and prevent the gangway from falling into the sea.
Purely by chance no personnel were transiting across the gangway at the time of the incident and there were no injuries to personnel working in the vicinity.
Had personnel been on the walkway when the jacket end fell some ten metres into the sea there could have been multiple fatalities and or serious injuries.
Corrective actions and Recommendations:
- Fabrication yard quality assurance must include a thorough inspection to ensure that the design and specification have been met. These need to include checks that all specified welds have been made, not just Non-Destructive Testing (NDT) of the welds that have been made, and that mill certificates for the steel used matches the grade that was specified, not just the yield stress.
- Secondary fall protection arrangements must be properly engineered and specified in the installation, operation and maintenance procedures for gangways.
- These procedures need to also provide for close visual inspection at least once per shift when the gangway is in use.
Who is responsible?
- The operator of an offshore facility has the general duties of care under the Offshore Petroleum and Greenhouse Gas Storage Act 2006 to ensure all work and activities are safe and the risk to people is as low as reasonably practicable. Specifically, the operator must implement and maintain a safe system of work for any plant and equipment.
- Any titleholder and service contractor who is in control of any particular work carried out at a facility has similar duties as the operator for that particular activity.
Source: OGP Safety Incident Reports http://info.ogp.org.uk/safety/