General The term Semi-Submersibles used in these Guidance Notes refers to: ? Column-Stabilized Drilling Units defined in the ABS Rules for Building and Clasing Mobile Offshore Drilling Units (MODU Rules) ? Column-Stabilized Units defined in the ABS Guide for Building and Clasing Mobile Offshore Units (MOU Guide) ? Column-Stabilized Installations in the ABS Rules for Building and Clasing Floating Production Installations (FPI Rules). A semi-submersible is a column-stabilized floating offshore structure@ which consists of a deck structure with large diameter support columns attached to submerged pontoons. In the design and operation of semisubmersibles@ the air gap as defined in Subsection 1/3@ also known as the deck clearance@ is an important design parameter. A low air gap may lead to wave impact that the structures and equipment of a semisubmersible are not designed for and could potentially cause serious damage. Conversely@ an excessive air gap could increase the cost@ decrease the stability@ reduce payload capacity and impair global performance. These Guidance Notes provide procedures for the air gap analysis based on either the linear or the second order potential theories@ address nonlinear effects on the air gap analysis@ and identify industry common design practice. The theories and equations referenced in these Guidance Notes are based on the infinite water depth assumption. However@ the procedures described in these Guidance Notes are in general also applicable to finite water depth condition.
ABS 249-2017 history
2017ABS 249-2017 GUIDANCE NOTES ON AIR GAP ANALYSIS FOR SEMI-SUBMERSIBLES