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Portsmouth International Port linkspan​​

The investment in the energy saving properties of a new linkspan at
Portsmouth International Port

What

Portsmouth International Port was proud to take delivery earlier this year of a ‘state of the art’ new linkspan from Ravestein BV. 

A linkspan is very simply the floating link between the ship and the port itself.  The range of tide in Portsmouth is 5,1m.  It is unusual for any two ships to have exactly the same freeboard (height above sea level) and therefore the link-span must be fully adjustable for height.  Whilst the linkspan and ship will both be prone to the same tides, the linkspan itself must be built such as to be afloat at all times but also have sufficient buoyancy to support the discharging cargo of freight and passenger vehicles.  ​​The heights of High and Low water are therefore critical.
For normal operations, the seaward end of the linkspan is supported on a buoyancy tank capable of supporting the ‘dead’ load of the bridge, upper deck and tank structure and the additional ‘live’ load of any one of the following vehicular loadings.

* 2 lanes of HGV Vehicles on the top and bottom decks simultaneously.
* 1 lane of loaded, 85t MAAFI units/Cassettes plus one lane of tugs returning empty on the lower deck only.
* 1 vehicle of 45 units HB loading (180t) on the lower deck only.
Thanks to PECS, the linkspan has been made using steel of a higher standard and quality in order to give it a 30 year life cycle instead of the more usual 20 years. Ravestein BV were asked to quote for those carbon saving technologies that could be incorporated into the design. With no roof and adjusting angles, solar panels were wanted but not able to be operated efficiently.

​The double decked linkspan will be used by Brittany Ferries’ new gas powered vessel, the Honfleur, when she enters into service next year. The larger environmentally friendly ferry will serve the popular route from Portsmouth to Caen.

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Why

Powered by Liquid Natural Gas (LNG), the new linkspan will emit far fewer emissions than conventional fossil fuels. PECS supported the port in thinking through low carbon technology that could be incorporated within the linkspan and have part funded carbon saving properties.   ​​
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​The International Port consists of 5 RO-RO berths and 2 commercial berths situated at the North Western side of Portsea Island on 14 Hectares of  land. The challenges of reducing the Carbon footprint of a unit that customers required to be larger, heavier and quicker than that which it replaced, were great. 

​​Fortunately the PECS partnership includes ‘knowledge partners’ whose task within the group is to validate the scientific basis of carbon reduction claims. Current indications are that a 6% reduction over the previous linkspan may be taking place but the linkspan is still subject to acceptance as minor problems are addressed.​​

The new linkspan, designed and built by Ravstein BV (who also incorporated the new technologies requested), is a unit 400 tonnes heavier than its predecessor that takes more weight and operates more quickly. Critically this allows a greater amount of time for the ship to make her channel crossing allowing for fuel savings and reduced carbon production.   

the ‘bank-seat’ after removal of the old link-span 
the new link-span in place and operating 
+32 487 54 87 68
 

How


The delivery and installation of the new linkspan took just under a month and had a strict timetable:​​

03/03/2018: MTS Vigilant sails from Rotterdam with linkspan under tow
07/03/2018: MTS Vigilant arrives in Portsmouth roads, linkspan delivered to berth adjacent to operating position 
08/03/2018: old linkspan removed and towed to Porchester moorings
10/03/2018: new linkspan positioned on berth 4 bank-seat (shore hinge)
17/03/2018: new linkspan becomes operational (lower deck only)
27/03/2018: load test both deck for Lloyd's Register Certification
30/03/2018: subject to successful load test above linkspan to become fully operational

The new linkspan being pushed into her lay-by position before the floating away of the old one the next high water
New linkspan being towed to her new position
The removal of one linkspan and the delivery and fitting of a new one is not an easy feat of engineering and required perfect planning and the adoption of fall-back positions should everything not going to plan. This included the provision of a mobile crane capable of lifting 700 tonnes available in case the tide height on the day was insufficient to lift the old linkspan off its bank seat. In the event the pontoons (that were filled with water to allow them to access the underside of the old linkspan and then had the water pumped out) had sufficient buoyancy and height to float the old linkspan off the bank-seat at the next High Water.
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​This picture depicts the delivery tug 'MS Vigilant'  (in red) standing-off from the newly delivered  linkspan.

Simultaniously a local multi-cat pushes up against the unit as it is secured in its temporary position awaiting the removal of the old linkspan (seen to the left of the picture). 

Budget

 

Timeline and events

Despite build, delivery, testing and operation, the new linkspan is subject to much ‘snagging’ work before final acceptance.  The largest  ‘snag’ has been the upper deck hydraulic rams which have proven to be unfit for purpose and were replaced in June 2018.  Until all ‘snagging’ has been completed and the engineers have accepted the new linkspan, the important work of measuring energy use by the new linkspan cannot yet be accurately measured.

Results


Carbon reduction

As a direct result of the Interreg 2 Seas project and PECS, the new linkspan at Portsmouth International Port has:

* Higher Quality Steel to Standard S355 giving the linkspan a life of 30 years rather than the normal 25 years.
* Soft start’ electric ballast pump motors requiring less energy.
* A paint system that should last for 20 to 25 years.
* A water ballast system for raising and lowering the tank rather than the fast air-blower system it replaced.