SPS could 'revolutionise' shipbuilding industry

News - September 22, 2000

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The Sandwich Plate System (SPS), a steel-elastomer engineering construction, could revolutionise the shipbuilding industry, make better ships that are lighter and safer - and have many other advantages compared to those built using conventional stiffenedsteel plate - claim its proponents.

SPS is the invention of Dr Stephen Kennedy, formerly a Professor of Structural Engineering at Carleton University in Ottawa, Ontario. With his brother, Michael Kennedy, Dr Kennedy has formed a company - Intelligent Engineering (IE) - to develop the SPS and market it to the shipbuilding and civil engineering industries.

Experts in their fields at classification societies, universities, shipyards and shipowners have all testified to what they believe to be a truly revolutionary way of building ships.

The Sandwich Plate System is effectively a laminate or 'sandwich' in which the outer 'layers' are steel plates, and the inner core or 'filling' is an elastomer, a solid polyurethane formed by the rapid reaction of two liquid components.

The sandwich is easily fabricated on site, using readily available injection equipment, which, says the inventor of the SPS, is inexpensive, costing a few pennies per kilogram of material injected. The injection process for a typical panel takes about 90seconds to complete. The equipment is said to be easy to install and operate in shipyards, or, panels could be prefabricated on a production line basis and delivered to a yard.

"By nature, Lloyd's Register is a sceptical organisation, says Alan Gavin, LR's Marine Director, "but LR has also become convinced of the potential benefits of the SPS".

In fact, Gavin said that the only potential disadvantage with the SPS is that yards will have to retrain and retool in order to use it. Other experts who have praised the potential of the system include Professor Chengi Kuo at Strathclyde University, andDr John Parker, Chairman of the Babcock International Group plc, a former President of the Royal Institution of Naval Architects (RINA) and Chairman of the LR Technical Committee.

The precise cost building a ship using the SPS would depend very much on the complexity of the ship, but given the advantages over traditional steel plate, particularly the significant reduction in stiffeners and in welding, SPS is expected to be highlycost-effective in the long-term.

The SPS has passed more than 80 different fire tests, including many conducted by the Marine & Coastguard Agency (MCA) in the UK, with flying colours.

Weight reduction would be key benefit of the SPS - in a 40,000dwt tanker, eliminating stiffeners would also eliminate a significant quantity of heavy fillet welds.

Reducing the weight of a ship would reduce its mass and make it easier to propel - for the same hull shape, less energy would be required to push it through the water, and, depending on the density of the cargo, more cargo could be carried for the same displacement.

In fatigue tests the SPS had also demonstrated a level of performance that far exceeded that which is possible with conventional structures. The elastomer in the composite structure has the effect of dissipating stress over larger areas, reducing hard spots where stiffeners are welded to plates, inhibiting the formation of cracks.

Eliminating welds, sharp edges, hard spots and other such potential sources of corrosion would have an extremely beneficial effect on maintenance requirements and operating life, and the physically less complex structures produced would be easier to coat.

The first ship to have made use of the SPS is P&O's ro-pax ferry Pride of Cherbourg, which was fitted with a 42m2 SPS deck section towards the end of last summer at A&P's Falmouth yard in the UK. A deck section was selected to trial the SPS in order to demonstrate its performance parameters in an area of regular, heavy usage. Using the SPS rather than a conventional construction meant that bulb flats and associated welds were eliminated, there was significant reduction in fatigue and corrosion prone details, a 6 per cent weight reduction was achieved, and the SPS provided superior thermal insulation and improved vibration characteristics.

Twelve months later, P&O confirms that the ship has not encountered any problems, and says more of its ships could be fitted with the SPS construction.Gavin says that all types of structure can be built using the SPS, and most types of ship.

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