The Performance, Safety and Production Benefits of SPS Structures ...

More documents

Recommendations

Info

The elastomer, as a two-part liquid, is injected intoclosed cavities formed by steel plates and perimeter bars(not shown in Figure 2.1) that are welded or glued toboth plates. To obtain a bond strength greater than of 6MPa once cured, the plates are grit blasted and need to beclean, free of contaminants and dry when the elastomer isinjected.A summary of the technology development undertaken todate and future development work is given in AppendixA.There is increasing interest in new constructionapplications. Ship operators are keen to take advantageof the benefits in improved lifetime performance,reduced maintenance and structural simplicity. An SPSdesign of a Rhine river barge is currently undergoingclass approval; and a prototype service barge for BritishWaterways has been completed and is undergoing trialsas part of a major fleet replacement project. SPS is alsogaining wider use in specific components on ships, wheresome of the unique properties such as fire protection andnoise attenuation are exploited.2.2 RECENT APPLICATIONS OF SPSSPS has found many applications in both civil andmarine industries. Recent projects include a replacementhighways bridge in Canada, where SPS was used toreplace a concrete deck, thus allowing the capacity of thebridge to be increased without upgrading the foundationsand substructure.Figure 2.4 Newbuild RoRo Ferry Funnel CasingsFigure 2.2 Indented Bulk Carrier Tank TopIn the marine industry much of the experience to date hasbeen in deck re-instatements of vehicle ferries, offshoresupport vessels and bulk carriers. Figure 2.2 shows thetank top of a bulk carrier that has suffered extremeindentation of the plating due impact from heavy cargoesand grab damage. The tank top plating was repairedusing an SPS Overlay which returned the structure to a“better than new” condition, as shown in figure 2.3.After 6 months’ service the repaired plating has sufferedvirtually no significant indentation under the sameoperating conditions. The tank top remains flat and even,allowing faster unloading and more efficient cleaning ofthe hold, thus speeding up the turn-round time andimproving the readiness for the next cargo.Figure 2.3 SPS Overlay Repair on Bulk Carrier TankTopIn 2003 Flensburger Schiffbau Gesellschaft commencedthe fitting of SPS panels in the funnel casings of a seriesof new ro-ro vessels (Figure 2.4). The SPS panels wereselected over conventional steel because significantspace savings were required to house machinery andequipment in a confined space. They are approved toA60 standard, with no additional insulation; and this inassociation with the elimination of secondary stiffenersmet the requirements for the application. The panels arestiff, easy to erect and significantly flatter than equivalentstiffened steel panels.A potential application for SPS is the “double hulling” ofexisting single hull vessels. A scheme has beendeveloped which uses pre-fabricated SPS panels to formthe inner hull plating. Use of SPS in this applicationhelps maximise cargo carrying capacity by keeping theinternal structure of the inner hull to a minimum. Tominimise the impact of time-out-of-service, IE’s solutioninvolves dropping the large panel sections through slotsmade in the existing deck or outer hull as shown inFigure 2.5.Other newbuild development projects include:• UR S21 compliant hatch covers: IE has developedhatch cover designs for panamax and capesize bulkcarriers. SPS provides an ideal solution to the newrequirements, as it has a high resistance to theincreased pressures and impact loads anticipated bythe new regulations. The simplified structure gives2
hatch covers that are structurally efficient and easyto manufacture.• Lightweight vehicle decks for dedicated vehiclecarriers: IE is working with industry partners todevelop SPS deck structures that are efficient bothstructurally and in use of space.Figure 3.1 Typical Section Through aDouble Hulled VLCCFigure 2.5 Use of SPS Panels to “Double-Hull” existingSingle Hull Tankers• Kawasaki Ship Building Corporation and IE aredeveloping SPS scantlings for the revolutionary SeaArrow bow. This innovative application of SPSwill provide a structure that will resist high impactloads from the sea, but will collapse in a controlledmanner in a collision. This will minimise overalldamage to both vessels and reduce the risk offlooding and loss of cargo.• IE has commissioned a study by StrathclydeUniversity, which investigates the economics ofusing SPS in the production of superstructures. Theinitial results show that labour costs for constructionusing pre-fabricated SPS panels can be reduced byover 50% against a conventional all-steel alternative.3. THE APPLICATION OF SPS TO DOUBLEHULL TANKERS3.1 BACKGROUND TO DOUBLE HULLTANKERSThe tank configuration of double hull tankers is nowfamiliar to the marine industry. Figure 3.1 shows atypical cross section through a double hull VLCC. Theresulting structure is based entirely on conventional shipconstruction concepts, with transverse web frames thatsupport stiffened plate panels for the inner and outerhulls. In the example shown there are approximately 300longitudinal stiffeners, each of which has to pass throughevery transverse web frame and bulkhead leading to15,000 or more intersections over the cargo region alone.The transition from single to double hulled vessels hasbeen driven by the imperatives of safety andenvironmental protection. The paradox is that theresulting ships are more complex than before, with asubstantial increase in the number of fatigue andcorrosion prone details, where risk of initiating structuralfailure can occur. As well as the basic requirement fortankers to have double hulls, there are now additionalregulatory measures stipulating increased survey andmaintenance (including access for inspection) on tankers.It has been argued that similar standards of inspectionand maintenance of single hulled ships would haveresulted in a similar improvement to safety, but at alower cost.In light of recent incidents involving tankers, especiallyolder single hull ships, it is clear that improvements intanker safety are important and urgently required.However, the fact remains that tankers are now morecostly to build and maintain than ever before.3.2 DESIGN ISSUES FOR CONVENTIONALSTEEL DESIGNSFrom the point of view of hull design, the ideal ship:• Has a structure which is sympathetic in terms ofconstruction – simple and easy to build• Requires little through-life maintenance• Suffers little or no corrosion• Has a minimum of breakdown in coatings• Suffers no cracking or other structural problems• Does not unduly vibrateSince the 1960s considerable experience has beenaccumulated in service performance of tanker designswhich have grown in size, often through a process ofextrapolation of structural arrangements.Through the 1970s, ‘80s and ‘90s, advances incomputing technology have enabled naval architects togain a better understanding of dynamic loads from wavesand ship motions, along with the importance of detaildesign, structural alignment and construction quality.Design processes have improved and lessons from3
Page 4 and 5: construction related failures and i
Page 6 and 7: SPS structures have a high inherent
Page 8 and 9: InnerShellOuterShellCentrelineBulkh
Page 10 and 11: pre-fabricated at a single site for
Page 12 and 13: • The ability to provide fire pro
Page 14 and 15: Stress, MPa9080706050403020100-80 o
Page 16 and 17: (a) corner impact test, punctured s
Page 18: steel ship structures for resistanc

The Performance, Safety and Production Benefits of SPS Structures ...

Create successful ePaper yourself

Delete template?

Save as template?