Fields producing crude oil into the Brent System pipeline are required to measure and account for production in units of mass, whereas traditionally volumetric units are usually preferred. The measurement of mass is currently done indirectly, by continuously multiplying volume and density measured at line pressure and temperature: the density being measured by continuous on-line transducers of the vibrating element type.

Although the vibrating element density transducer is capable of very high orders of accuracy and has been widely used for clean hydrocarbon liquids and gases, its use for fiscal or custody transfer measurements on crude oil to date has been limited.

In this paper the experience gained since the beginning of 1980 with a twin density transducer system on the Thistle ‘A’ platform is described in order that operators intending to install similar systems may benefit from BNOC's experience.

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