During a rig move an international drilling contractor suffered a failure to a gear train whilst jacking down. The failure resulted in significant damage to one of the cord racks.

Once the rig was in port Stowen mobilised personnel to complete a Close Visual Inspection (CVI) of the damage,  a three-man NDT rope access team was deployed to survey the damage and complete the repairs.

SURVEY OBJECTIVES:

• Identify damaged leg sections within the leg structure affected

• Confirm quantity of teeth that had sheared off

• Take dimensions from damaged leg section splices and tubular braces. 

• Close Visual Inspection and dimensional check of jacking column. 

 

 

The Findings

The CVI survey confirmed that the damage had been limited to one individual leg section between 300’ to 330.’

Two teeth had been completely sheared off the rack and seven other teeth showed signs of damage. Following an additional UT inspection of the damaged teeth it was confirmed they were beyond repair

The Repair

Working alongside the clients engineering department and DNV, Stowens project team devised a plan to remove & replace the damaged section of rack weighing in at 7.5t. This process is believed to be a world first for a rig of this size and class and certainly a first for our client.

The plan was executed by jacking the rig up to the required elevation and building a habitat around the damaged leg section. The habitat was required to give protection from adverse weather conditions in the region, which were often below 0°C with high wind speeds and heavy rain.

Stowen mobilised a 14-person team of multi-skilled rig builders comprising of heat treatment techs, 6GR coded welders and fitters, L3 riggers & NDT inspectors to commence the repairs.

Working 24hrs a day in often very challenging conditions the team was able to complete the repairs without incident, on schedule and within budget.