Scope and application These rules cover classification of floating offshore objects for the following services:

— LNG/LPG production

— LNG/LPG storage and offloading

— LNG/LPG loading (buoy).

Although this document refers primarily to liquefied natural gas (LNG) and liquefied petroleum gas (LPG), the principles herein may also be used for other offshore gas installations such as those involving primarily compressed natural gas (CNG), and gas to liquid (GTL) products.

A floating offshore installation which processes hydrocarbons and refrigerates gas to produce LNG will be termed here an LNG FPSO (LNG floating production, storage and offloading unit). LNG FPSOs are also commonly termed FLNG. The installation may be fed gas directly from a gas well or a gas network or may process associated gas in conjunction with oil production. Such units may also produce, store and offload quantities of LPG and condensate.

A floating offshore installation which processes hydrocarbons and refrigerates gas to produce LPG will be termed here an LPG FPSO (LPG floating production, storage and offloading unit). The installation may be fed gas directly from a gas well or a gas network or may process associated gas in conjunction with oil production. Such units may also produce, store and offload quantities of condensate.

An offshore installation which receives and regasifies LNG is termed an FSRU (floating storage and regasification unit). The storage and hull may generally follow the requirements to a storage unit described in Ch.2 Sec.4. The regasification plant and safety systems may follow the requirements in DNV-RU-SHIP Pt.6 Ch.4 Sec.7 on regasification vessels. FSRUs which follow a ship lass regime may refer to DNV-RU-SHIP Pt.5 Ch.7 and DNV-RU-SHIP Pt.6 Ch.4 Sec.7.

Guidance note:

This document addresses floating steel structures. Concrete structures, both floating and bottom fixed have also been proposed for offshore gas applications. For such designs, see DNV-ST-C502. Where such units are classified, the principles in this document may be applied.

Principles, procedures and requirements for retention of class during operation of the unit are covered DNVRU- OU-0300.