API MPMS 17.2:1999 (R2011)

To determine the quantity and quality of cargo on board marine tank vessels, it is necessary to accurately gauge, ascertain the temperature, collect a representative sample, and calculate the amount of all materials contained in the vessel's lines, cargo tanks, and slop tanks. Any void spaces that may contain cargo, such as permanent ballast tanks, double bottoms, and cofferdams, must also be checked, and any volumes contained in these spaces must be calculated. This publication describes the appropriate methods of performing these procedures for crude oils and petroleum products normally carried on board marine tank vessels. This standard covers the use of manual and automatic measurement systems commonly used on marine tank vessels. It establishes the procedures for obtaining the level measurements of cargo, free water, and OBQ/ROB as well as taking the temperatures and samples required for the marine custody transfer of most bulk liquid petroleum cargoes. It does not address in detail the technologies of the equipment used. This standard is not intended for use with pressurized or refrigerated cargoes such as liquid petroleum gas (LPG) and liquid natural gas (LNG).