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The term 'Gas Trials' is used to encompass those tests that are undertaken during a period when a quantity of LNG is taken onboard for testing shipboard facilities at, or near to, the design temperature. Gas Trials are usually carried out prior to the vessel entering service in order to confirm the correct function, integrity and capacity of the complete cargo system, including containment, insulation, cargo handling equipment, pipelines and valves ana the equipment to handle boil-off gas (BOG). This document is intended to provide members of SIGTTO some guidance on the requirements for testing the systems for handling the LNG cargo, and its consequential BOG, using LNG loaded onto a vessel specifically for that purpose. The scope is considered applicable for established membrane, spherical tank and SPB designs. However, it does not extend to novel or prototype designs, which may require specific additional testing. This document is not intended to be used as an operational procedure, but merely as an aide to preparing a specification for gas trials. The guidance aims to cover those items tested prior to the handover of a vessel and also the testing carried out post delivery, when a first full cargo has been loaded. Any figures provided in the text are only indicative and reference should be made to the shipbuilder and manufacturer's information for figures applicable to a specific vessel. The underlying assumption in this document is that the Gas Trials are conducted by the shipbuilder prior to delivery of the vessel. This is the common practice for LNG ships, but by no means exclusive (Note, the normal practice in the LPG industry appears to be for the trials to be conducted at the first load port after delivery). 'Gas Trials Guide for LNG Vessels', SNAME 1977 is an informative reference often cited in LNG Shipbuilding Contracts.