Long distance transportation of solids by slurry pipeline is an evolving technology which commenced in 1957 with the 172 km Ohio coal pipeline in the United States of America.

The world’s first long distance mineral slurry pipeline was built in Australia in 1967 for the Savage River magnetite concentrate mine in Tasmania.

Since then, slurry pipelines built in the region include: the Bougainville, Irian Jaya, and Ok Tedi copper concentrate pipelines, the 24 km Gladstone limestone pipeline, the 18 km New Zealand steel iron sand pipeline, the 304 km Century zinc/lead concentrate pipeline and the 62 km Whyalla magnetite pipeline.

The Savage River Iron Ore Pipeline in Tasmania – a world first

The Savage River iron ore slurry pipeline commenced transporting magnetite concentrate on October 26, 1967 and has continuously operated for over 45 years.

A key element in the evolution of long distance slurry pipelines is the adaptation of cross country oil and gas pipeline technology to the transport of minerals and coal in slurry form.

Cross country oil and gas pipelines are fully welded, using high strength steel pipes, externally coated and buried.

The buried pipeline is further protected from external corrosion by an induced current cathodic protection system.

Unlike long distance water supply pipelines, cross country slurry pipelines have no requirement for either air valves at high points or drain valves at low points.

However, development tests for the Savage River pipeline determined the need to restrict the maximum slope of the pipeline.

Long distance slurry pipelines operate at high pressure.

The Savage River pipeline requires positive displacement pumps to create sufficient pressure to maintain pipeline hydraulics.

At the time Savage River was engineered, it was necessary to select a positive displacement pump from a similar service.

The pump selected was again sourced from the petroleum industry.

Copper concentrate slurry pipelines in Papua New Guinea

The success of the Savage River Pipeline ushered in the adoption of slurry pipelines to transport copper concentrate in mine developments during the late 1960s and early 1970s mining boom.

Copper concentrate slurry pipelines were an advantage to the development of mineral deposits in the jungles of Papua New Guinea.

The copper minerals were extracted at the remote mine site and the resulting concentrate was transported to the coast by slurry pipeline, and in most cases the mine was in the mountains and the terminal was near sea level on the coast, hence, gravity assisted the pipeline hydraulics.

The two earliest systems were the Bougainville Copper Concentrate Pipeline (27 km, DN150) and the Irian Jaya Ertsberg Project (111 km, DN100) followed by the Ok Tedi pipeline (156 km, DN150) in 1986.

Each project required the building of an access road through the jungle for transport of equipment, materials and personnel for mine development and operation, with the slurry pipeline was buried in the access road shoulder.

The Erstberg project was, by far, the most inaccessible mine.

The elevation varied from sea level to about 3350 m at the mine site, with the concentrator and slurry pump station at 2750 m.

The maximum slopes in the escarpment were up to 28 per cent, with the transport of major equipment up the escarpment achieved by dragging the transports with a D9 bulldozer.

However, after one year of operation, the Irian Jaya pipeline experienced major leaks in a region where the hydraulic gradient line intersected the ground profile, resulting in slack or open channel flow.

After the Irian Jaya experience, all long distance slurry pipelines eliminated slack flow by installing choke stations where necessary to hold back the pressure to maintain a packed line.

The world’s first pipeline loading of bulk mineral commodities aboard a tanker offshore, without a deep water port, was successfully completed on 5 July 1971 at Waipipi, New Zealand (NZ).

The Waipipi shiploading system was based on single point oil tanker loading systems developed for the oil industry.

The Waipipi cargo consisted of 43,000 t of ironsands concentrate in slurry form, which were pumped offshore via a 2.4 km, DN300 submarine pipeline to the ore carrier, which was moored to a single point buoy more than 2.4 km off the rugged west coast of New Zealand’s North Island.

The success of the Waipipi system over a 12 year period assisted in the development of a unique technical step in slurry technology resulting in NZ Steel’s long distance ironsands pipeline from Taharoa to Woolf Fisher Steel Mill in South Auckland, a distance of 18 km.

The NZ Steel pipeline was an extension of experience from both Savage River and Waipipi ironsands technologies, which required a wear resistant liner, with the Waipipi experience determining that the wear in rubber lined pipe was minimal.

Spun cast polyurethane was selected as the preferred liner for the NZ Steel pipeline, however, a key technical question was how to join the polyurethane lined pipes by a welded joint to allow long distance pipeline construction methodology.

As a consequence, a unique, high pressure welded coupling was developed to allow down hand welding without destroying the bond between the polyurethane and steel pipe.

The basic principle of the coupling was to control the temperature rise at the polyurethane/steel bond during the down hand joint welding operation.

The NZ pipeline system was recognised as a world first with a unique contribution (one of only seventy awards) to the engineering history in New Zealand.

Cementing a place in the industry

The manufacture of Portland cement up to fairly recent times was a wet process.

Quarried limestone was ground in slurry form to form a high density slurry to which clay, sand and ironstone were added to form a kiln feed slurry.

In more recent times, the wet process has been replaced by a dry process to save energy lost in the drying of the kiln slurry.

A long-distance slurry pipeline was an ideal method to transport the limestone slurries for the wet process.

The slurry pipeline allowed the cement manufacturing to be undertaken on a separate site to the limestone quarry.

In 1981 the Queensland Cement and Lime Company Ltd, commissioned the 24.2 km long DN200 steel pipeline from an inland limestone quarry to a new cement manufacturing plant near Gladstone, Queensland.

The 304 km, DN300 Century Pipeline transports zinc and lead concentrates from the Century mine in north-west Queensland to Karumba on the Gulf of Carpentaria.

At Karumba the concentrate is filtered then loaded onto a barge for subsequent loading onto a ship moored offshore in the Gulf.

The pipeline was commissioned in 1999 and was the first slurry pipeline in Australia to incorporate a high-density polyethylene (HDPE) liner to avoid internal corrosion.

All the early pipelines described above (except the polyurethane lined NZ Steel pipeline) were unlined, bare steel pipelines, where internal corrosion was controlled by raising the pH to approximately 10 with the addition of lime.

The Century Pipeline was welded in lengths of up to 2 km with bolted flange joints joining each length.

The HDPE pipe was then pulled through the steel pipe by a special process involving reducing the outside diameter of the HDPE pipe by passing it through a set of rollers prior to entering the steel pipe, through which it was pulled using a steel wire.

The Century Pipeline was the first slurry pipeline in the world to transport two different products in the one pipeline.

The zinc and lead concentrates were transported in batches with approximately one hour water slug separation.

The Century Pipeline is also the longest slurry pipeline in the world with a single pump station, with three Wirth piston diaphragm pumps each driven by an electric motor installed in parallel.

As is the case with all slurry pipelines today, the Century Pipeline was designed entirely from bench scale laboratory tests.

No pipe loop tests were conducted prior to pipeline construction.

From the laboratory test data the pipeline hydraulics were determined and pipe size and pump requirements specified.

The 62 km, DN200 OneSteel magnetite pipeline transports magnetite concentrate from the Iron Duke mine to Whyalla, South Australia, and was commissioned in 2007.

The Whyalla pipeline was the first slurry pipeline in the world to incorporate a return water pipeline.

A DN400 parallel water pipeline returns the water from the slurry pipeline plus additional water required for mine use.

Until now, all slurry pipelines have required a water supply at the mine site.

However, environmental concerns and water shortages will probably mean that most new slurry pipelines in Australia will require a return water pipeline.

With such a strong historical pedigree, it is inevitable that the region will see the development of more long distance slurry pipelines in the future.

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