1.92km of 1066.8mm OD spiral welded steel, tape coated, concrete lined pipe

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After the success with concrete lined steel (CLS) pipes on the Maitai Valley Pipeline, CLS pipes were again the preferred pipe option for Stage 2 of the project.

Following the successful installation of 7.9kms of 650.2 x 4.8mm WT x 12m concrete lined steelpipe into the Maitai Valley, Stage 2 was commissioned, involving laying pipework from the treatment plant down to Brook St.

The terrain from the treatment plant down to Brook St was very steep and uneven and like the Maitai pipeline, the strength of welded joints and the ability of these joints to be self-supporting was a major advantage.

The hemispherical slip in joints (HSJ) that were supplied on each pipe offered a number of significant advantages to the Brook St pipeline project over alternative methods. The ease of connection from one pipe to another meant that on-site welding was also quick and easy. The welded joint also has the added benefit of providing extra strength to the joints, eliminating the use of support thrust blocks and reducing the effect of circumferential stress. The ability of the HSJ joint to deflect pipes up to 3 degrees at each joint reduced the number of fabricated bends required.

Because of the limited access and steep hillsides, the standard 12m pipe lengths were too heavy to be safely moved by an excavator, Steelpipe were able adjust the manufacturing plant to supply in 6m lengths and solve this problem.

To ensure a minimal amount of disruption to the contractor, the pipes were delivered direct to a laydown site at the Nelson Port by a local Nelson trucking company, with the first shipment being accompanied by a Steelpipe representative. This close contact was maintained throughout the project and was crucial to reducing risks to the project and for the successful, on time completion.