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USING HDD MAXI-RIGS
ON MAJOR PROJECTS THE HULK - A GALLAGHER HDD660E ELECTRIC MAXI-RIG.
There is increasing awareness across the utility industry that horizontal directional drilling (HDD) can provide an effective whole-of-life solution for the installation of pipelines. In this article, Maxibor CEO and Owner, Rodney O’Meley, provides insights into maxi-rig spreads and highlights the benefits of utilities and other infrastructure asset owners using HDD maxi-rigs on major projects.
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axi-rigs are defined as those HDD rigs required for the installation of pipelines between 400mm (16 inches) and 1200mm (48 inches) in diameter, and rated for more than 45,359kg (100,000lb) of thrust and greater than 9,072kg (20,000lb) of torque. Maxibor has four maxi-rigs – a Vermeer 330x500, American Auger 660, Gallagher 600 and Gallagher 660e, and access to others if required. The maxi-rig spread is a significant investment, as it comprises much more than just the rig. Drill fluid cleaners, high volume pump(s), mud mixer, vacuum truck, rods and tooling and excavators to manage the pipe and rods, all add to the on-site cost of the spread even before a rod is turned. The purchase cost of a new spread today would not leave much change from AUD$8 million. The mobilisation, demobilisation and on-site relocation also requires having prime movers, trailers and sideloaders to move the equipment. A good on-site stock of spare parts, extra rods and tooling are all essential if you want to maintain productivity on major projects, especially in more remote locations, not just ‘nice to haves’.
INVOLVEMENT FROM THE EARLY STAGES The length and diameter of pipelines that maxi-rigs can install will depend on the ground conditions and pipe being installed. While they have the capacity to drill pipelines in excess of 2km with diameters up to 1.6m, typically in Australia maxi-rigs are mostly used on projects in excess of 500m with bore diameters of more than 600mm. Involvement of maxi-rigs on smaller projects can be seen as a reflection that the Australian infrastructure sector has traditionally taken a conservative approach to the use of HDD and other trenchless technology installation methods. The industry has only just reached its 30th year in Australia, whereas the US recently celebrated 50 years and is regularly doing bores over 4km with maxi-rigs. However, the knowledge and capacity to take on more challenging projects in Australia is certainly there, particularly where you have very experienced design and construct HDD providers like Maxibor.
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This enables the integrated body of knowledge required to deliver more complex HDD projects to be involved from early design through to delivery and final commissioning and testing of the pipeline. Maxibor is now regularly being sought out to be involved in the concept stage of projects. Decision makers and other stakeholders are then better informed about the construct options and value-add solutions to project challenges using HDD.
PROVEN IN THE FIELD Maxi-rigs are ideally suited for river crossings, ocean outfalls, hard rock conditions and multiple service bores requiring larger diameter holes. Distance is not a problem, nor is force, to complete the bore, as the power of the maxi-rigs and the pumps (e.g. Gardner Denver PZ9s) are more than sufficient to overcome the most difficult ground conditions, bore length or other design constraints. Projects where Maxibor has used its maxi-rigs have included a 1.320km Logan City Council project which connected the Greater Flagstone Priority Development Area with the Cedar Grove sewerage treatment plant. Maxibor designed and delivered a 1.320km bore installing 500mm of PE100 HSCR PN20 to a depth of over 50m. This is still one of the longest bores in Australia in recent years. The advantage of having maxi-rigs in the fleet was demonstrated on a project to install a new 400m section of water pipeline between Lamb and Macleay Islands in Queensland. Maxibor used one of its Vermeer 100x120s to complete the pilot hole and most of the reaming. The Vermeer 330x500 maxi-rig was then brought in to use its extra muscle to ream the bore hole to a 550mm diameter and pull the DN400 PN20 pipe through. Into 2022, Maxibor has several bores lined up for its maxi-rigs with distances in the 1.5km to 2.5km range. It is also working in the early design stage with various asset owners and principal contractors on other projects across Australia where its ability to solve complex river and harbour crossings and outfall project challenges will help optimise outcomes for all stakeholders.
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