New slipway built to launch London Titan
Dorset UK based Jenkins Marine has completed a scheduled refit of its new workboat, Avon, formerly Crossness when part of the Port of London Authority fleet.
With the refit completed, Avon has received its first commission and, in a strange twist of fate, is to help construct a slipway to launch its replacement in the PLA fleet.
Having sold Crossness (now Avon) and secured the sale of sister ship Hookness, also to Jenkins Marine, the PLA has procured a somewhat extraordinary replacement. The new design has been dubbed a marine ‘Swiss Army Knife’. The giant multi-tasker, London Titan, will be a Mooring Maintenance Vessel, or MMV for short, and has been designed to lay buoys, haul wreckage from the bottom of the river Thames, support dive operations, and even dredge. It will weigh in at around 650 tonnes and will be more than 36.5m long and 13.5m wide, with a maximum draft of 2.2m and an air draft of just over 6m. London Titan boasts an impressive specification which was compiled by the PLA after studying current working practise and future projections.
Construction of the vessel was awarded to Manor Marine Services in Portland against stiff European and UK competition. It is the largest vessel built to date by Manor Marine. Consequently, London Titan needs a specially constructed slipway to launch. Manor Marine chartered long standing business associate Jenkins Marine to assist with part of the construction of the civil engineering groundworks to launch Manor Marine’s latest project.
Jenkins Marine was to help with the extraction and disposal of the redundant concrete piles from the existing quay wall to clear the entrance for the newly constructed slipway. Avon's 120 t/m, 19.5m radius deck crane proved invaluable, as some piles required a lifting force in excess of 16 tonnes to extract with the crane by direct pull. The first few piles had to be extracted by tidal lift, a process where a lifting chain is secured to a pile at low tide with the other end of the chain attached to the bow of the vessel. As the tide lifts the vessel, the force of the vessel’s buoyancy is applied to lift the pile.
The Avon was able to employ it’s ballasting system to great effect and speed up the lifting process, pumping over 40 tonnes of ballast in to the stern ballast tanks, and pumping out over 20 tonnes of water from the forward ballast tank, thus increasing the lifting force. Avon also used its new 12m long spud legs to hold position while working on site. The extracted piles were loaded onto the deck (which is able to take up to 100 tonnes of deck cargo), before being offloaded to shore.
A spokesman for the PLA said: "We are delighted to see Avon hard at work here at Portland, helping with the work to build the slipway for the launch of her replacement, London Titan. The launch is expected in March and trials and delivery of the PLA’s new ship is due in August, following completion of fitting out alongside."
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