Chervil Structural Stair Replacement

The Scope

The Chervil monopod has been out of service for some years. To support Quadrant well abdandonment work by jack-up, Quadrant required the stairways between decks to be functional.

Cube’s initial scope was to assess the old, existing stairway. Cube was then engaged to design and supply a new stairway.

The Outcome

Cube assessment of the existing stairway revealed  a significant amount of corrosion in critical areas and a lack of structural integrity.

Chervil is an unmanned, minimal facility and does not have a crane so a replacement was limited to manhandle items. Consequently, Quadrant considered a scaffolding solution but sought input from Cube on an alternative option.

Cube proposed an aluminium, modular design with bolted connections, supported by the existing primary steelwork that fitted over and within the existing stairway. The design enabled the existing stairway and handrail to remain inplace, saving the significant cost of removal. The Cube design provided a significantly cheaper option to scaffolding because of the offshore labour cost.

To make vessel mobilisation, the schedule duration was 6 weeks. Cube committed to that schedule was given the responsibility to design and supply the new stairway. Cube labelled and packed the numerous small parts, generated assembly packs and briefed Quadrant installation team on the assembly. The 8 modular parts where assembled on site in two shifts.

A key risk identified from the outset was the lack of as-built or survey data. Dimensional flexibility was incorporated into the design and was required during assembly.


Cube Offshore - Solving complex engineering challenges
Cube Offshore - Solving complex engineering challenges
Cube Offshore - Solving complex engineering challenges