Chapter 6
I Construction During The Settlement Years
II The Use Of Timber As A Structural Material
III Structural Steel
IV Concrete Technology
V Housing
VI Industrialised Pre-cast Concrete Housing
VII Ports And Harbours
VIII Roads
IX Heavy Foundations
X Bridges
XI Sewerage
XII Water Engineering
XIII Railways
XIV Major Buildings
XV Airports
XVI Thermal Power Stations
XVII Materials Handling
XVIII Oil Industry
i All Welded Storage Tanks
ii Insulated Fuel Oil Pipeline
iii Wartime Concrete Tanks
iv The Cobia 2 Sub-sea Completion
v Mackerel and Tuna Platforms
vi Snapper Post-Trenching Plough
vii The North West Shelf Project Plough
XIX The Snowy Mountains Scheme
XX The Sydney Opera House
XXI The Sydney Harbour Bridge
XXII Hamersley Iron
XXIII North West Shelf
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Snapper Post-Trenching Plough
The Snapper Post-Trenching Plough was designed and fabricated for the singular purpose of burying the Snapper 61 cm gas pipeline. The pipeline is 36 km long and runs along the sea-bed from the Snapper Platform to shore. The plough develops a 'V' shaped trench by ploughing through seabed material, similar to the way a farmer ploughs a furrow. The prefix 'Post' is added to describe the fact that the plough was used after the pipeline had been laid. This was the first time in the world that a laid pipeline has been trenched with a plough. This was done at a low cost compared to other methods and has added a new dimension to pipeline burial.The burial of oil and gas pipelines in an offshore environment is a very desirable feature of pipeline installation, especially for main lines running to shore. The reason for this is that burial provides the pipeline with lateral stability against on-bottom currents. Also the spoil cover gives added protection against damage which could be caused by scallop dredges and anchor cables. Obviously there is a very large incentive to reduce the risk of damage to a pipeline, due to the large costs associated with pipeline repair.
Various methods have been used over the years for lowering pipelines below the sea floor, the most common technique being jet sledding. In Bass Strait in spite of high installation costs the results have only been partially satisfactory. Trenching ploughs, however, are a completely different concept in pipeline burial, being designed and built to cut out a clean even trench in the sea bottom. The trench is made as narrow as possible with sides slopes corresponding to the angle of repose of the seabed material. The material displaced from the sea-bed is moved onto the sides of the trench. After the pipe has settled in the trench, ocean bottom currents move the spoil material back over the pipe and eventually level the sea -floor profile.
People in Bright Sparcs - Gorrie, A. W.
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Australian Academy of Technological Sciences and Engineering |  |
© 1988 Print Edition page 419, Online Edition 2000
Published by Australian Science and Technology Heritage Centre, using the Web Academic Resource Publisher
http://www.austehc.unimelb.edu.au/tia/420.html