Semi-Submersible BOP Carrier Upgrade

Houlder supported a BOP upgrade on a drilling semi-submersible during a planned shipyard stay. Houlder engineers undertook a structural review to establish if a BOP carrier upgrade was required to accommodate an increase of load from 200Te to 235Te. Houlder was commissioned to undertake the structural analysis and design suitable strengthening and modification, where required, to ensure any BOP carrier upgrade complied with DNV standards for Drilling Plant & Lifting Equipment.

Equipment Survey and Structural Analysis

Houlder Hydraulic and Structural Engineers undertook an offshore survey to review current equipment status against documentation. This included a 360 degree laser scan of the moonpool area so that the results could be interpreted during the design phase. Structural analysis determined that a BOP carrier upgrade was required to increase structural strength to accommodate the new weight of the BOP.

Mechanical Drive and Hydraulic Operating System Design

The hydraulic operating and mechanical drive system also required upgrades for the increased SWL. There were also operability issues advised by the Client as well as several existing equipment deficiencies. A new duel drive motor arrangement was designed to fit within the existing structure as well an upgraded main jacking cylinder, both to fulfil DNV requirements.
The hydraulic operating system design was reviewed, detailed schematic drawings were provided to the Client for approval prior to system upgrades being commissioned.

Equipment Procurement and Pre-Yard Manufacture

The following materials were ordered and manufactured prior to the SPS commencement. Everything required was delivered to site prior to the rig arrival which ensured no delays. Specific items include;

  • Complete set of replacement hydraulic cylinders with the required DNV approvals
  • New drive system gearbox assemblies and all associated shafting
  • New drive pinions and drive rack system for the moonpool edge
  • All hydraulic components and pipework to enable power unit, control suite and hydraulic system to undergo a complete upgrade package
  • Steel profiles for the structural upgrades and fabrications for the drive system mounting arrangement

Yard SPS Works

Houlder were contracted to conduct the Normar Carrier upgrades during the vessel yard stay. A site management team consisting of structural and mechanical supervisors, site safety and quality/procurement were mobilised to site for the duration of the works.
Outer Frame and Lift Fork structures were removed to a quayside work shop facility which allowed the moonpool area upgrades to progress.
The quayside work shop area saw Houlder’s tradesmen conduct all of the steelwork strengthening whilst the mechanical technicians conducted overhauls and fitted the new drive system.

Hydraulic technicians conducted the pipe-up, flush and pressure testing as well as installing the upgraded controls suite. Simultaneous work on the rig saw the power unit overhauled and the mechanical drive rack installed to the moonpool edge.

The quayside workshop period completed with new paint system application and then re-instatement onto the rig. Commissioning and on board testing culminated in successful 260 tonne dynamic load test.


The Semi-Submersible BOP carrier upgrade project ensured the client had confidence in the safe and efficient operation of their drilling unit.

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