Preston Docks - Diving services for dock gates maintenance

Hughes Subsea mobilised surface supplied Diving equipment to support the client with operatives working from a floating platform for the most downstream gates.

Hughes Subsea have a long and proud history of supporting Preston City Council with the continued maintenance of the 4 sets of lock gates connecting the River Ribble to the Albert Edward Basin and the wider canal system.

Project Details

Hughes Subsea have a long and proud history of supporting Preston City Council with the continued maintenance of the 4 sets of lock gates connecting the River Ribble to the Albert Edward Basin and the wider canal system.

The inspections carried out by Hughes Subsea throughout the years have identified significant defects which have required remedial repairs. The identification of and remedial works to these defects has allowed the docks to remain operational and eliminated the need for costly gate replacement works. 

Since their original installation, the gates have been modified from a chain pull arrangement to hydraulic rams acting above the waterline. To “take the weight” off the heel strap spear posts have been installed adjacent to the mitre beams. The spear posts consisting of “H” section steel columns fixed in a sliding arrangement through the use of brackets bolted through the 18” width of the greenheart gate. The bottom of the spear posts is fitted with a greased wheel encased in heavy steel shrouds.

Being the original greenheart gates dating from the 1890’s the gates are not only considerably durable and robust but have been subject to numerous repair and maintenance regimes. Drilling into them requires specialist equipment and patience. Previous maintenance attempts have also resulted in a number of half-finished holes which requires the diver to be mindful that tooling does do drift into one of these previous apertures. Work site conditions are unfavorable with the diver working in nil-visibility conditions. 

Hughes Subsea mobilised surface supplied diving equipment to support the client with operatives working from a floating platform for the most downstream gates. Due to the unknown condition of each bolt Hughes Subsea has developed and utilized a number of techniques for the removal of the failed bolts:

•    Broco: underwater thermal cutting
•    Drilling
•    Impact driving

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