A light, modular stairway was required to quickly and safely access the Vermilion Oil and Gas (VOGA) Wandoo A platform helideck from the Noble Tom Prosser (MODU) cantilever deck 7.5 metres above.
Cube Offshore were contracted to design, manufacture and test a fully functional solution.
Several months later, a similar requirement arose to safely access the Wandoo B platform main deck from the Tom Prosser cantilever deck. This configuration resulted in a 9.5m vertical separation between decks, the landing area was more remote and the stair was to remain attached to the cantilever during skidding activities.
Cube’s design solutions for Wandoo A included the following:
- Weight – aluminium design used for significant weight reduction
- Transport – split into two modular parts for road transport & manual handling into position. Each part certified for offshore lift so no baskets required.
- Installation – simple bolt connection in middle for assembly. Upper end stabbed into guide / Lower end on heavy duty castors
- Significant relative motions between Wandoo A and Noble Tom Prosser cantilever accommodated by incorporating a swivel hinge at the top and rollers at the base
The Wandoo A stairway was to delivered on schedule and to budget. The stairway was transported, assembled and deployed safely and quickly.
The requirement at Wandoo B was not forseen by VOGA. However, Cube was able to reuse the two existing halves by adding a middle section (see photos below). This creative design for a new application saved VOGA significant time and cost. All pre-existing design requirements were met.
Elevation of WNA aluminium access stair
Stair pre-assembled inside the Tom Prosser cantilever module
Stair lifted and stabbed into pre-installed sockets in the mousehole gutter opening
Access stairs landing on the WNA helideck
Hatched area on WNB main deck shows stair landing area subject to cantilever skidding requirements
Re-use of WNA stair sections for WNB application with the addition of a central tower section
3D isometric of WNB aluminium access stair
View looking down WNB access stair tower, onto the WNB main deck from the Tom Prosser cantilever