Dry-Transportation & Wet Tow Engineering
Our service offerings encompass:Dry transport: In Dry transport, the rig is loaded onto a purpose-built submersible ship often referred to as a heavy lift vessel (HLV). Dry-transport highlights:
- Stability Analysis of Rig onboard HLV - Float-on / off operations.
- Longitudinal and Shear Strength check of HLV for each draft.
- Rig catcher and guideposts. Allowable Rig Leg bending moment, Cribbing arrangement and loads, Rig hull structural strength for loads anticipated during voyage.
- Mooring and securing arrangement during float on / off.
- Wind loads and motion loads for each marine sector.
- Limiting Environment for the voyage.
- Forecast Monitoring using DNV Alpha Factors.
- Directional weather and heading control.
Wet Tow: Jack up rigs floating on their own hulls and towed by tugs or barges is called a wet tow. There are two types:
- Field Tow
- Ocean Tow
- Tow route met ocean study: 10-year return non-cyclonic seasonal and directional met-ocean extremes corrected for appropriate exposure in each sector for a towage speed of the rig.
- Critical motion curve: The limitation based on time period of roll/pitch motion vs allowable single amplitude motion. Legs gradually lowered until the resulting motion of the jack up was acceptable as per “critical motion curve”.
- If critical motion curve is not available, then a leg strength can be checked by detailed structural analysis.
- Office based monitoring and forecast review for the wet tow using DNV alpha factors.