The Refinery to Auckland Pipeline was built as part of the expansion of the Marsden Point Refinery. Though first conceived in the early 1980s, construction of the pipeline began in 1983 and was commissioned in 1986 by pipeline owner and operator New Zealand Refining Co Ltd (NZRC).

Spanning 170 km, the 10 in. Grade X52 pipeline transports refined products (including gasoline, jet and diesel) from the refinery at Marsden Point to a terminal at Wiri in South Auckland. A small pipeline from Wiri is then used to supply Jet A1 product to Auckland International Airport.

In addition, an 8 in. high pressure gas line, which is owned and operated by Vector Gas, was installed simultaneously with the 10 in. product line within the same trench.

Pipeline design

The original design, performed by a joint venture comprised of Houston-based Pipetech and Murray North partners from Auckland, included three pumps at the Marsden point refinery delivering directly to the terminal in Auckland at a maximum allowable operating pressure of 9.04 MPa.

The pipeline was primarily routed through rural areas and crosses numerous streams and steep hill country with one harbour crossing at Manukau in Auckland. Two options were presented and the current route was selected for minimal disturbance to both environment and landowners.

The route was intended to maximise the use of rural land and minimise crossing of major waterways. This also achieved a reduction in cost with the requirement to use heavier wall pipe in river/harbour crossings and urban areas. This basis of design has required continuous updating for urban encroachment (see ‘Managing land issues in New Zealand’ box). The design was in accordance with ASME B31.4 and NZS5203, which have now been replaced with the use of AS2885 parts 1 to 3 for the pipeline’s continued operation and maintenance.

Pipeline expansion

In the early 1990s, an increase in demand for petroleum product in the Auckland region necessitated additional capacity and a higher flow rate. Planning commenced on the various options available in the mid-1990s and the debottlenecking was conducted in three stages.

Two intermediate pumping stations Wellsford (IPS1) and Kumeu (IPS2) were installed after flow modelling analysis was performed on the pipeline. Pump stations IPS1 and IPS2 were installed in 1998 and 2004 consecutively, boosting the capacity to meet increasing demand from the Auckland region and the aviation industry.

The tie-ins for these stations were performed by hot tapping into the existing line to eliminate the need for shutting down the essential flow of refined product to the region. The new design also catered for surge due to the intermediate pump installations and the operating pressure was reduced to 7.5 MPa with installation of surge relief valves at each station and at the refinery. There is still room for another pump at the second pump station located at Kumeu.

Future plans

There are some additional options that NZRC is also considering for expansion of the pipeline, including using a drag reducing agent and installation of an additional pump at IPS2.

Trials performed using drag reducing agents along one section of the pipeline have demonstrated good results, indicating a possible 15 to 20 per cent increase in flow. As this is economically more attractive it would be an option to an additional pump above with three injection points along the route. Potential issues with cross contamination in Jet A1 are to be resolved.

One of the other alternatives being considered is the installation of additional line work to cater for demand. However, this would pose a major challenge due to the restrictive nature of the relatively narrow Isthmus at Auckland, and would possibly require a longer sub-sea segment, which would require further study. This would need sanction at a national level.

However, based on current predictions of consumption, NZRC expect that the Refinery to Auckland pipeline will have sufficient capacity until 2016, especially given the potential for an extra pump at the IPS2 pump station in Kumeu.

For further information about the pipeline, Peter Owbridge may be contacted via email at (JavaScript must be enabled to view this email address), on +649 432 8311 or on +64 27 493 2395 (mobile).