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HMRC internal manual

Oils Technical Manual

Pipelines: How do we deal with the mixing that happens when one product follows another down a pipeline?


As a parcel of oil is injected into the pipeline at the ingress point, it shunts along the parcels that are in front of it. Each parcel of oil may be of a different type. Where 2 parcels are shunted together they will meet, merge and mix to form ‘new oil’, a third type of oil of a different description to the two original constituents. The point at which two different oil products meet and merge in the pipeline is known as the interface.

Where a parcel of AVTUR is used instead to separate two parcels of oils, this is known as a buffer and will also form interfaces.

Authorisation and Approval

We have to approve both the pipeline operator and the pipeline user(s) for mixing before this can occur in a pipeline. This enables the mixing to be controlled so that the original duty paid on parcels of oil can be adjusted according to the changes in the descriptions and quantities when the oil is delivered from the pipeline system.