An alignment of failures
Article published in the Regulator | Issue 1: 2017
In March 2016, NOPSEMA was notified of a dangerous occurrence on an offshore platform where a 7.5 tonne motor-operated valve (MOV) was being lifted and removed by a spreader bar when the device failed and the MOV dropped 0.3 metres to the deck below. Given the size and weight of the MOV this ‘dropped object’ incident had the potential to cause death or serious injury. The failure of the spreader bar to safely lift the MOV was not the result of a single mistake but an alignment of failures across the design, procurement and assembly of the lifting equipment.
To lift and remove a 7.5 tonne MOV, the operator contracted an engineering firm to design a spreader bar that could safely complete the task. The engineering drawings that were developed, however, were ambiguous and lacked sufficient written information to show that a standard component had to be modified before it could form part of the lifting equipment.
During the procurement process, the rigging supplier quoted an incomplete bill of materials (the list of components that make up the spreader bar) based on what they assumed the engineering drawings required. Not realising the discrepancy between the engineering drawings and the proposed bill of materials, the operator signed off on the rigging supplier’s quote.
At this stage, the components ordered to assemble the spreader bar were incomplete and the engineering drawings lacked sufficient written information to show that a standard component had to be modified for the lifting equipment to be assembled correctly.
During assembly, the rigging personnel on the facility identified the discrepancy between the components supplied to them and the spreader bar’s engineering drawings. To get the job done, the rigging personnel made certain assumptions and decisions without obtaining appropriate approval. Specifically, the spreader bar was assembled using another component instead of the modified component that was required.
Due to the alignment of failures during the design, procurement and assembly of the lifting equipment the spreader bar dropped the MOV and presented an unacceptable risk of death or serious injury to the workforce.
Operators, manufacturers and suppliers all have duties with regards to equipment that will be used by members of the workforce at a facility.
A manufacturer of equipment supplied to an offshore facility has a duty of care under the OPGGS Act to take all reasonably practicable steps to make available adequate written information about the design, construction and safe use of the equipment. Equally, it is the operator’s responsibility to ensure manufacturers are providing them with adequate written information in the engineering drawings, particularly if modification is required to a standard component.
Operators must refrain from making assumptions about engineering drawings during the procurement and assembly phase. Clarification of the design basis with the appropriate person in charge of the project work or task must be sought if there is any ambiguity, and any changes must be communicated and authorised appropriately.