HCOTEG110500 - Pipelines: Cross country pipelines
Introduction
The first pipeline network in the UK was the Government Pipeline and Storage System (GPSS) constructed in 1942 to supply all the RAF and USAF air bases in the UK. Most of the commercial Cross country pipelines (CCPs) were built in the 1960s and early 1970s.
Duty status of Mineral Oil transported
The pipeline traffic consists mainly of oils which have already passed the duty point - but may include others such as AVTUR which although they have passed the duty point are fully rebated, and therefore retain a duty liability. Some pipelines do carry duty free or suspended product; the USAF being a duty free shipper. An interactive site showing a map of the whole network, with descriptions of the markers of the pipeline is at http://www.linewatch.co.uk/network.htm.
(N.B. This site requires a multi-media player, access to which is not currently available to all internet users in HMRC).
Technical background
About a third of the primary distribution of oil from depots and refineries is carried by pipelines. This amounts to about 25 million tonnes. Most of the pipelines operate at high pressure, many at around 1400 pounds per square inch. Unsurprisingly, pipelines supplying fuel to airports operate at vastly lower pressures. Pipelines can be only a metre below the surface. The bore size or internal diameter of the tube is commonly about 10-12” but can be up to 16”.
Pipelines are by far the cheapest form of transport, and costs fall with constant use - distance having little effect. Pipelines are most efficient with low viscosity easy to pump fluids, and generally are designed for the white oil to gas oil viscosity range.
Sequencing of oil parcels and contamination
Each consignment down a pipeline is referred to as a parcel.
To keep contamination to a minimum when one product follows another down a pipeline, products are sent in the sequence: naphtha (the lightest), petrol, kerosene, gas oil (the heaviest), kerosene, petrol, naphtha. Although generally there is no physical barrier between each product, an inflatable sphere is sometimes put in the pipe between consignments.
Oils parcels - interfaces and buffers
Pipelines are usually operated remotely by control centres that control the routing of whatever oils they have been scheduled to pipe from ‘A’ to ‘B’. Where one product follows another there is an ‘interface’ (which may also be referred to as a buffer in the case of AVTUR). This interface or buffer is a product that is not to the original specification of the oil to be delivered by virtue of inadvertent mixing in the pipe.
Other considerations
The amount pumped will be measured at the ingress point (inlet) and egress point (outlet) or tank. Because there are commercial interests involved, we can usually assume the accuracy of trade measurement. However, mistakes can occur, and you should not assume that the trade cross checks the meter readings.