The Conversion of Vessels to Meet Higher Ice Class Requirements Using SPS Overlay

Ice Class Vessels, 28-29 April 2015, London, UK

© 2015: The Royal Institution of Naval Architects

THE CONVERSION OF VESSELS TO MEET HIGHER ICE CLASS REQUIREMENTS

USING SPS OVERLAY

M. Brooking and Dr. O. Sukovoy, Intelligent Engineering (UK) Ltd. UK

SUMMARY

Intelligent Engineering has designed an SPS Overlay solution to upgrade vessels to meet higher Ice Class requirements

enabling them to operate in ice conditions.

Ship owners wishing to upgrade their vessels to satisfy new Ice Class operational requirements have previously faced

undertaking major modifications to existing hull structures such as increased shell plate thickness and additional frames

and stringers.

By using SPS Overlay on the external surface of the shell plating in the ice belt region, higher Ice Class strengthening

requirements can be met without major disruption to the hull structure. The use of SPS Overlay eliminates conventional

crop-and-replace of the existing shell. The inherent local stiffness of SPS Overlay ensures effective distribution of any

localised peaks in the ice pressure loads. In addition to providing increased plate strength, SPS Overlay increases the

section modulus of the framing plate/stiffener combination thus minimizing changes to the existing frames. SPS

Overlay’s ability to absorb high impact loads makes it ideal for this application. The system uses the existing hull as one

side of a steel composite panel formed by a new top plate and an elastomer core, greatly reducing the complexity of the

conversion, time out of service and total repair costs.

This paper describes the technical work carried out to design and achieve DNV-GL class approval, and install the SPS

upgrades.

1. INTRODUCTION

SPS (Sandwich Plate System) is a structural composite

material comprising two metal face plates permanently

bonded to a polyurethane elastomer core, which can be

used as an alternative to conventional steel construction

and repairs. The compact elastomer core provides

continuous support to the face plates prevents local

buckling and in many cases removes the need for

secondary stiffeners.

SPS was initially developed to provide impact resistant

plating for offshore structures and ice islands operating

in harsh ice conditions of the Canadian Beaufort Sea.

Research and development focused on material

characterisation, structural behaviour and performance,

design principles, energy absorption design philosophies

and the development of connection details specific to

sandwich plate structures. Physical properties, design

parameters and production techniques have been

established through extensive analytical, experimental

and prototype work.

SPS has been used widely in the marine industry since

1999; and has an established track record in ship repair

and construction. To date more than 300 projects have

been completed on a wide range of ship types. SPS is

approved by all major classification societies and

regulatory authorities for use in newbuilds and

rehabilitation of ships and offshore units. Lloyd’s

Register published provisional ship construction rules in

2006 [1]; and more recently DNV-GL published Class

Note 30.11 [2] describing the classification requirements.

Figure 1 –Offshore Supply Vessel (OSV)

Intelligent Engineering (IE) was requested to prepare a

design to strengthen the hull structure of an offshore

supply vessel (OSV), illustrated in Figure 1, using SPS in

order to upgrade the Ice Class of the vessel to DNV’s

ICE-1C. The hull needed strengthening to satisfy new

operational requirements. IE has undertaken detailed

design work to confirm that ice strengthening

requirements according to classification standards can be

met using SPS. Following review for compliance with

the applicable Rules and Regulations, DNV-GL granted

the approval to the proposed SPS Overlay design.

Design & Operation of Wind Farm Support Vessels, 28-29 January 2015, London, UK


2. DESIGN

2.1 DESIGN SUMMARY

Built in 2002 the vessel is classed with Det Norske

Veritas, (Class Notation: 1A1 ICE-C Tug Supply Vessel

Fire Fighter) and has principal particulars as listed in

Table 1.

Length overall 80.00 m

Length between

perpendiculars 69.30 m

Rule length 73.10 m

Breadth moulded 18.00 m

Depth Main Deck 8.00 m

Scantling draught 6.60 m

CB 0.7655

Speed 16 knots

Engine output 12000 kW

Table 1 – Principal Particulars

The vessel was built in compliance with the requirements

for the class notation ICE-C, that relate to the hull

strengthening only in the bow region of the vessel. ICE-

C is intended for a vessel which operates in light first-

year ice conditions and calls into ports which

occasionally experience ice. Finnish and Swedish

Transport authorities do not recognise ICE-C as an ice

class, and vessels with this notation are treated as open

water vessels. To satisfy new operational requirements

for areas with potentially heavier ice conditions, the OSV

had to be upgraded to ICE-1C ice class.

The existing structure of the OSV in the ice belt region

was evaluated to determine the extent of strengthening

required to meet DNV ICE-1C class requirements. The

comparison of the required and existing as-built

scantlings for the ice belt regions of the hull revealed that

the existing shell plating and most of the frames in the

area of the forward ice belt are below the minimum Class

requirements for ICE-1C. The shell strakes in way of

(iwo) ice strengthening area should also be of higher

grade steel. Conventional conversion would have

involved replacing existing shell plating with thicker

steel of a higher material grade, replacing or

reinforcement of the existing frames to heavier scantlings

and adding new intermediate ice-frames. This would

have taken the vessel out of service for a long period and

resulted in a higher repair cost. IE developed an SPS

Overlay solution that significantly simplified the

conversion and reduced the project schedule.

The alternative solution proposed was to apply an SPS

Overlay (approximately 900 m2 total) 15-25-E to the

outer shell iwo ice belt in the bow region and 10-20-E

iwo the ice belt midbody and stern regions to strengthen

the OSV hull. For specific areas of existing hull framing

that did not meet the requirements, a small number of

additional web frames and ice stringers were proposed to

reduce the spans and strengthen existing frames in the

forward ice belt region.

The design of ice strengthened structure was then

evaluated using the routine rule based calculations,

supported by Finite Element Analysis.

2.2 STRUCTURAL REQUIREMENTS FOR ICE

STRENGTHENING

To ensure efficient operation and safe navigation in ice

without incurring any damage to vessel and surrounding

environment, a vessel is typically to be designed to a

relevant ice class and shall comply with regulations.

Classification rules require a minimum level of ice

strengthening of the hull structures to be sufficient to

withstand ice loads for normal operations in the ice

conditions associated with the ice class.

The requirements with which the OSV vessel shall

comply when assigning a new class notation ICE-1C and

recommendations related to this alteration using SPS are

specified in:

DNV Rules for Ships Part 5, Chapter 1, “Ships for

Navigation in Ice”, January 2012.

DNV Classification Notes No.8, “Conversion of

Ships”, April 2013.

DNV Classification Notes No.30.11, “Steel

Sandwich Panel Construction”, April 2012.

As per DNV Rules for Ships Part 5, Chapter 1, Section 3

“Ice Strengthening for the Northern Baltic” the

requirements for strengthening the ice belt for ICE-1C

are accepted as equivalent to the Finnish-Swedish ice

class IC requirements given in the “Finnish-Swedish Ice

Class Rules 2010”.

Extent of Ice Strengthening

The extent of the ice strengthening is determined from

the Upper Ice Water Line (UIWL) to the Lower Ice

Water Line (LIWL), which defines the extreme draughts.

For the OSV the UIWL and the LIWL were assumed at

6.60 m and 4.40 m aBL respectively. The ice belt was

divided longitudinally into three regions, i.e. the bow,

midbody and stern regions, as required by DNV Rules

and indicated in Figure 2. Vertical extension of the ice

strengthening for plating and framing was also

determined in accordance with the Rules.



Figure 2 – Ice belt regions

2.3 SPS OVERLAY DESIGN EVALUATION

The results of the design assessment calculations

according to the class ICE-1C requirements are

summarised briefly below.

Shell Plating

The existing hull plating does not meet the ICE-1C class

requirements. To strengthen the hull an SPS Overlay 15-

25-E iwo ice belt bow region and 10-20-E iwo ice belt

midbody and stern regions was proposed. In addition to

providing increased plate strength, the SPS Overlay

increases the section modulus of the framing

plate/stiffener combination thus minimizing changes to

the existing frames.

The proposed SPS Overlay design scantlings are a 15

mm top plate and a 25 mm elastomer core for SPS

Overlay 15-25-E in the bow region of ice belt, and 10

mm top plate and 20 mm core for the SPS 10-20-E in

other two regions of the ice belt. This includes an

additional 2mm on the top plate to withstand the abrasion

of ice.

The steel grade of the SPS Overlay iwo ice strengthening

area shall be minimum grade B/AH as per Pt.5 Ch.1 Sec.

2 E101 of DNV Rules for Ships.

The local plate strengthening is readily achieved, since

the local plate modulus of the SPS Overlay structure is

greater than that of the conventional plating thickness

required by the DNV Rules. The shell plating has been

evaluated by calculating the section modulus of 100mm

wide strips of plate for the conventional design and

proposed SPS Overlay 15-25-E and 10-20-E design.

This evaluation has been extended to demonstrate the

acceptability of the proposed SPS Overlay plating when

future wastage is applied (see Table 2). 20% diminution

of the existing shell plating was assumed for the current

evaluation of the corroded structure, which represents a

conservative assumption. It would be normal practice for

the local Class surveyor to verify the condition of the

existing structure prior to commencing work.

Table 2 – Properties of Shell Plating iwo Ice Belt

Table 2 demonstrates that the section modulus of the

plating, and therefore the local strength of the existing

shell plating strengthened by SPS Overlay, is

considerably greater than that required for the all-steel

solution, even when future wastage is considered.

Therefore all SPS plating scantlings shown in Table 2

provide adequate strength.

In addition to the above, direct calculations by finite

element analysis (FEA) were used to evaluate stresses

and demonstrate adequacy of SPS Overlay plating. Two

finite element models of the SPS Overlay structure for

bow and midbody regions with distinct structural

arrangement have been created. Details of this FEA and a

summary of the results are presented in section 2.4.

Midbody Region

Stern Region

Bow Region



The chemical bond at the interface between the core and

faceplates is required to transfer shear under operational

loads for the full range of operating temperatures. Bond

strength is governed by the surface profile and

cleanliness. Using grit blasting for surface preparation

(see Table 5, Step 1) typically results in interface bond

capacities in the range of 10 to 12 MPa. Recognising that

variations can occur with the surface preparation, the

bond partial safety factor of 1.8 and design value of 7.5

MPa as the allowable bond shear stress, were used for

this application as given in DNV CN No.30.11 Sec.3,

3.5.2.9. The stress distribution at the interface between

the elastomer core and faceplates was analysed with a

finite element model of a section of the side shell

strengthened with 13-25-Existing SPS Overlay (net

scantlings) and 8.8mm existing plating (assumed 20%

deducted for corrosion for 11.0mm as-built plate). The

FE model has been loaded with uniformly distributed

pressure of 3.26 MPa applied over a 220mm×800mm

strip at various locations. The applied load includes a 1.8

safety factor as per Pt.3 Ch.1 Sec.3 A204 of DNV Rules.

In all cases the maximum core shear stresses and stresses

at the core interface were less than the allowable stresses

and therefore the proposed SPS design fully meets the

requirements. Similar calculations were carried out for

the FE model with SPS 8-20-E.

Framing Members

The SPS Overlay works in combination with the framing

members to increase the section modulus of the

plate/stiffener combination. However, additional ice

stringers were required in the bow region between frames

54 and 93 in locations as shown in Figure 3(a). These

additional stringers reduce the span of the transverse

frames. One new stringer is to be fitted between Main

Deck and Tween Deck and the existing ice stringer

1400mm below Tween Deck is to be modified. These

additional stringers reduce the span of the existing

transverse frames. Also additional web frames are to be

installed at Frames 70 and 82, see Figure 3(c), to reduce

the span of the ice stringers and thereby reduce the

required section modulus for these stringers.

The hull framing was assessed in accordance with the

DNV Rules. Table 3 summarises the revised frames

(with reduced span, as illustrated in Figure 3) section

moduli and effective shear areas required in the bow ice

belt region. It also provides the calculated section moduli

of the sandwich plate with transverse frames. The

effective section moduli of the frames have been

calculated in assuming an attached load bearing plating

taken equal to the stiffener spacing as per Pt.3 Ch.2 Sec.

3 of DNV Rules for Ships. The results indicate that the

proposed SPS Overlay design will exceed the minimum

required values and thereby satisfy Class requirements.

Table 3 – Properties of Frames

Table 4 summarises the comparison of the required and

proposed scantlings of the additional transverse web

frames to be installed at Frames 70 and 82. The proposed

arrangement of additional steel to be fitted on top of the

existing frames to form new web frames is illustrated in

Figure 3(c). The web plates of the new web frames are to

be stiffened as per Rules for Ships Pt.3 Ch.2 Sec.3 C 602

with stiffeners positioned 600mm from each end of the

web span and maximum spacing of 900mm elsewhere.

Table 4 – Properties of Web Frames

The required shear area and section modulus for new Ice

Stringers (Figure 3a) for various regions were calculated

in accordance with the Rules (the results are not shown

here).

With the existing arrangement of the stem in the region

below 3240mm aBL, where the supporting elements

were spaced at 520mm, the shell plating thickness should

be increased to 23.0mm. The proposed stem

reinforcement in this region is to install additional

brackets (breasthooks) as indicated in Figure 3(b) with

red lines.



Figure 3 – Framing modifications required in bow region

NEW ICE STRINGER (6400 aBL)

NEW WEB FRAME #70

NEW WEB FRAME #82

EXISTING ICE STRINGER TO BE MODIFIED

PL300X10

PL.10BKT

BK

T

BK

T

BK

T

BK

T

BK

T

BK

T

BK

T

BK

T

BK

T

BK

T

BK

T

BK

TBK

T

~10~

FL75X10

W:570x10FL75X10

FL75X10

W:740x10FL90X10

W400X9FL75X10

BREASTHOOK

SPS 15-25-EXISTING

SPS 15-25-EXISTING

BHD56

BHD60

BHD66

BHD54

BHD58

~10~( )*

~10~( )*

~10~( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*( )*

( )*

( )*

( )*

( )*

W:400x10FL75X10

( )*W:400x10FL75X10

( )*W:400x10FL75X10

( )*1400 1400 1400

3500 42012114

1426

42022836

3633

742

4579

4690

2121

1094

BHD58

#90

#70

#85

#90

#80

W:490x10FL75X10

W:650x10

W:740x10FL90X10

#55 #60 #65

#70

#75

#80

#85

#90

BHD56

BHD60

BHD66

BHD54

ICE STRINGER 6400 A/BL

W400X9FL75X10W:490x10

FL75X10W:650x10

W:740x10FL90X10

W:740x10FL90X10

FL75X10W:490x10

#92#90#85#80#75#70#65#60#55

#60 #65

#75

#55

(a) Proposed new Ice Stringer at 6400 aBL

(c) Proposed new web frames at Fr.70 and Fr.82

FB.100x8

DET "D"

600

EXISTING BKT

REMOVED

( )*

( )*

( )*( )*

( )*

( ) *( ) *

( )*( )*

( )*( )*

PL 7,0

600

700

SCALE 1:50

HP.160X8

SPS 15-25-EXISTING

EXISTING BKT

REMOVED

DET "B"

SWL 6.6m

BWL 4.4m

ICE STR.3400 A/BL

ICE STR.6400 A/BL

SPS 15-25-EXISTING

FB.100x8

FB.100x8

1640 A/BL

4800 A/BL

8000 A/BL

SECTION @ FRAME 70

PL 7,0

W:9

60X

10F

B.1

00X

15

300X10

HP240X10

8.5

HP240X10

8.5

TWEEN DECK

MAIN DECK

TANKTOP

ICE STR.3400 A/BL

ICE STR.6400 A/BL

HP 220x10

250X250X9

HP

.260

X10

HP200X9

HP.160X8

100X8FB

HP 220x10

75X

8FB

PL.8.0

75X

8FB

100X8FB

100X8FB

HP 220x10

HP220X10

75X

8FB

PL.8.0

75X

8FB

100X8FB

BKT.

FB.100x8

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*

( )*( )*

( )*

( )*( )*

( )*( )*

( )*( )*

940

940

( ) *( ) *

( ) *( ) *

( )*

W:1200X

10

FB.100X

15

SCALE 1:50

W:1200X

10

FB

.100X15

HP

260X10

HP

260X10

SPS 15-25-EXISTING

SPS 15-25-EXISTING

DET "B"

SWL 6.6m

BWL 4.4m

ICE STR.3400 A/BL

ICE STR.6400 A/BL

DET "D"

EXISTING BKT

REMOVED

EXISTING BKT

REMOVED

EXISTING BKT

REMOVED

FB.100x8

FB.100x8

FB.100x8

600

600

600

FB.100x8

600

FB.100x8

FB.100x8

FB.100x8

FB.100x8

FB.100x8

FB.100x8

584

200X200X8

8000 A/BL

4800 A/BL

1640 A/BL

SECTION @ FRAME 82

250X250X12

250X250X9

HP

240X

10

HP180X8

500X500X15

300X300X10

300X300X10

ICE STR.3400 A/BL

ICE STR.6400 A/BL

250X250X9

HP

260X

10

HP

240X

10

HP200X9

HP180X8

200X200X8

HP260X10

500X500X15

200X200X8

W:1

200X

10

200X200X8

FB.1

00X

15

HP

260X

10

300X300X10

W:1

200X

10F

B.1

00X

15

TWEEN DECK

MAIN DECK

TANKTOP

300X300X10

FB.150X20

TYPICAL ADDITIONAL BREASTHOOK

#93

12.0

PERIMETER BARSIM TO DET "C"

30°

WELD TO BE FINISHED FULL& GROUND SMOOTH

FB.150X20

FB.200X20

FB.200X10( )*

( )*

150

SECTION 3240 AB. BL.

5120 AB. BL.

6400 AB. BL.

7680 AB. BL.

SECTION 550-1060 AB. BL.

(b) Proposed stem reinforcement



2.4 FINITE ELEMENT ANALYSIS

Direct calculations have been carried out in order to

evaluate the proposed modifications to the side shell

structure. The objective of the calculations was to verify

that the stress levels of an SPS Overlay plating structure,

under applied loads, are within acceptable limits. The

calculations of the vessel’s structural response were

based on a three-dimensional finite element analysis

(FEA) using ANSYS v13.0. FE models were created for

SPS Overlay plating for two representative locations in

the bow and stern regions. In addition, a local detailed

FE model was also used to evaluate the design of the

bow ice belt region.

FEA for Bow Ice Belt Region

Figure 4 illustrates one of the FE models, representing a

portion of the side shell strengthened with an SPS 15-25-

E Overlay between Frames 76 to 82 and between the

Tween Deck and Main Deck developed to verify that it

satisfies DNV’s requirements. The model was built using

shell elements (SHELL 181) for the structural members

(web frame, bulkhead, decks at elevations 4800 and 8000

above baseline, stiffeners etc.), the existing 8.8mm side

shell plate (2.2mm deducted from the 11.0mm as-built

plate, representing assumed 20% diminution), and the

new 13.0 mm thick SPS top faceplate (with the margin

for abrasion and corrosion of 2mm deducted from 15.0

mm plate). The 25mm elastomer core of the SPS

Overlay was modeled using solid elements (SOLID 185)

with 4 elements through the depth to capture the flexural

behaviour.

Figure 4 – Finite element model of bow region

Figure 4 illustrates the finite element model along with

the material properties and boundary conditions used in

the calculations.

The FE model has been loaded with the factored patch

load, i.e. uniformly distributed pressure of 3.26 MPa

applied along a narrow horizontal strip (800mm ×

220mm) as illustrated in Figure 5. The magnification

factor of 1.8 increases the design patch load above the ice

pressure of 1.811 MPa determined according to the Rules

Sec.3 B201. Four different load cases were considered

for the analysis of the SPS Overlay with the centroid of

the patch load positioned in the following locations:

1. directly over the frame at mid-span between the

Tween Deck and the ice stringer;

2. between frames at mid-span between the Tween

Deck and the ice stringer;

3. directly over the ice stringer at its mid-span;

4. directly over the web frame at its mid-span.

In accordance with the Rules the allowable stress in the

steel faceplates governing the design of the SPS 13-25-

Existing Overlay was taken as the yield strength of mild

steel, 235 MPa. The results indicated that the stress in

some locations in way of the frames exceed yield point

for two load cases. The von Mises contour plots

presented in Figure 5 show some plasticity in the existing

shell plate in the elements directly connected to the web

frame (stresses above the 235 MPa yield strength are

illustrated with a grey coloured contour). These stresses

are highly localized and in large part caused by the

geometric hard point in the model where the web of the

HP260×10 frame is connected to the SPS Overlay panel.

This joint location was modeled more accurately and

with higher order elements using local FE model (see

Figure 6) indicating significant reduction of this stress

concentration.

Figure 5 – Load Case 1: von Mises Stresses (MPa)

For the rest of the SPS Overlay, the normal and von

Mises stresses in the steel faceplates did not exceed the

allowable stress limit. Since the high stresses in both

load cases were highly localized and the majority of the

Bow Region

(a) SPS Top plate

800×220 patch load 3.26 MPa

(b) Existing plate

800×220 patch load 3.26 MPa



steel faceplates around the loaded area remains below the

allowable stress limit, the design scantlings selected for

the SPS Overlay were found to be satisfactory.

Local FE Model

A local three-dimensional FE model was created to

represent the behaviour of the side shell structure when

subjected to ice load. A portion of the side shell structure

measuring 2400mm × 2400mm, extending longitudinally

between web frames Fr.60 and Fr.62 and between ice

stringer and Tween Deck in vertical direction has been

modelled as illustrated in Figure 6. The SPS Overlay

component thicknesses used in the analysis were the

same as in FE model illustrated in Figure 4. Solid

elements SOLSH190 have been used and material non-

linearity has been specified in the model. The element

size selected was approximately 25 mm x 25 mm. Full

fixity has been applied at the deck and ice stringer levels

of the model and Y-constraints have been applied to the

free edges fore and aft to create continuous boundary

conditions.

The model was loaded with uniformly distributed

pressure of 3.26 MPa applied along a narrow horizontal

220mm × 800mm strip centred between the ice stringer

and deck. The applied load includes a 1.8 safety factor

as per DNV Rules for direct analyses; the design ice

pressure determined for this location is 1.811 MPa. The

non-linear analysis has been carried out for evaluation of

the strength of the side shell considering two load cases:

LC1 - with the load patch positioned directly above

frame FR.61

LC2 – with the load patch positioned between

frames FR.60 and FR.61.

Figure 6 – Local FE model for bow region

The results indicate that the stresses exceed yield in some

locations. Yielding occurs only at the plate surface

extremities and is highly localised. The small localised

plastification on the extreme fibre of the side shell plate

is insignificant in the global response as the majority of

the shell plating remains fully elastic.

Figure 7 – Von Mises Stresses in the SPS Overlay top

plate and existing shell plate (LC1).

For the LC1 the peak von Mises stress of 249 MPa is at

the surface of the 8.8mm existing shell plate and 256

MPa at the surface of the 13 mm SPS top face plate

(Figure 7); the contour plots with stresses in the cross-



sections through the shell plating are also illustrated,

indicating that the localised yielding does not extend

through the thickness of the plates rendering the response

mostly elastic. Figure 8 illustrates the interface shear

stress contour plot with a maximum interface shear stress

value of 4.7 MPa.

Figure 7 – Interface Shear Stresses in Elastomer Core

(LC1).

For the LC2 the peak von Mises stress of 249 MPa was

at the surface of the 8.8mm existing shell plate and 216

MPa on the surface of the 13 mm SPS top face plate; a

maximum interface shear stress was 6.2 MPa.

2.5 DESIGN REVIEW AND APPROVAL

IE’s drawings illustrating the strengthening of the

offshore supply vessel through SPS Overlay being

applied to the surface of the external shell plating in the

ice belt region along with the proposed side framing

modifications and supporting design calculations and

structural analyses were examined by DNV-GL.

Following their review for compliance with the

applicable Rules and Regulations, approval was granted

for the use of SPS Overlay for ice strengthening of an

OSV hull to DNV Ice Class ICE-1C.

It should be noted that the SPS Overlay strengthening

design approval is limited only to the hull’s structure.

Other requirements that address the capability of a vessel

to meet ICE-1C class include:

Stern frame and rudder

Engine Power

Propeller, shafts and gears

Prevention of ballast tank or fresh water tank

freezing

Sea inlet and cooling water systems

Protection from freezing and icing on decks and

deck equipment.

These were outside the scope of this study and the ship’s

owner was aware of the additional requirements to be

satisfied to achieve the ICE-1C notation.

3. INSTALLATION OF SPS OVERLAY

STRENGTHENING

The methodology for installing SPS Overlay uses a

combination of conventional steel fabrication practice

and SPS technology.

The SPS Overlay application is carried out in accordance

with IE’s standard installation procedures under the

supervision of the attending DNV-GL surveyor. Table 5

outlines the key steps for a vertical SPS Overlay

installation.

The advantages of using SPS Overlay instead of a

conventional solution to strengthen the OSV’s hull are as

follows:

SPS will provide improved lifetime performance,

better resistance to abrasions and indentations from

impacts; and significant potential for reduced

maintenance, repair and downtime costs.

SPS improves the resistance against impact loads

associated with operating in ice conditions;

SPS Overlay is simpler, quicker and less disruptive

to install.

4. CONCLUSIONS

Intelligent Engineering has undertaken detailed design

work to confirm that DNV ICE-1C Ice Strengthening can

be achieved using SPS Overlay and minimal framing

modifications.

The design was examined and verified for compliance

with the applicable Rules and approved by DNV-GL.

Its ability to absorb high impact loads makes SPS

Overlay ideal for this application. Use of SPS Overlay

eliminates conventional crop-and-replace. By minimising

the work required on the inboard side shell, SPS Overlay

offers the potential to significantly reduce the complexity

of the conversion work and reduce the overall conversion

schedule.

5. REFERENCES

1. Lloyd’s Register, ‘Provisional Rules for the

Application of Sandwich Panel Construction to

Ship Structure’, April 2006.

2. DNV-GL., ‘Steel Sandwich Panel

Construction’, Classification Notes No.30.11,

April 2012.

2. DNV, ‘Ships for Navigation in Ice’, Rules for

Classification of Ships Part 5 Chapter 1, July

2013.



Table 5 – SPS Overlay Process

6. AUTHORS BIOGRAPHY

Martin Brooking is the Marine Director for Intelligent

Engineering Ltd. Previously European Marine Business

Manager at Lloyd’s Register, he originally trained as a

ship surveyor and gained experience in both field

surveying and plan approval of tankers. He has also

worked in the Offshore Industry as a Consultant

Engineer with WS Atkins Ltd and DNV-Veritec Ltd,

where he gained particular experience in analysing and

solving fatigue problems on ships and offshore

structures.

Oleg Sukovoy is the Senior Design Engineer for

Intelligent Engineering Ltd. Oleg obtained his Specialist

degree in Naval Architecture at St Petersburg State

Marine Technical University (formerly Leningrad

Shipbuilding Institute). He then worked in Vyborg

Shipyard, Russia as Production Manager for several

years. He received Ph.D. degree in ship and marine

technology from the University of Strathclyde, Glasgow

and worked as Post Doctoral Research Fellow in the

Department of Naval Architecture and Marine

Engineering. He joined IE in 2005.

The Conversion of Vessels to Meet Higher Ice Class Requirements Using SPS Overlay

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