Impact of wear & tear in dredgingBemas 25/10/2006

Impact of wear and tear in dredging

• Types of dredgers

• Activities of JDN

• What is special about dredging and the related maintenance

• Maintenance of dredging equipment includes M+R and W&T

• Typical solutions to make components in contact with soil more resistant to abrasion

• Organisation of the maintenance

Cutterdredge

Hopperdredge

Dipper dredge

JFJ De Nul Barge loading

JFJ De Nul Barge loading

JFJ De Nul Shore discharging

Activities of JDN in 2005 795 Million Euro

0

5

10

15

20

25

Dredging

Capitaldredging

Mainte-

nancedredging

Off shoreactivities

Land

reclama-tion0

10

20

30

40

50

60

70

80

Dredging

Civilworks

James Cook shore discharging at Dubai (Reclamation)

Hopper dredgers

Vasco Da Gama

Il Principe in Valencia (capital dredging)

Offshore: Scour protection with the Side stonedumper Pompei

Rockworks

What is special about dredging and the related maintenance

• There is an enormous variation in the soil to be dredged: mud, sand (fine tocoarse, with or without shells),gravel (round or sharp pebbles), clay, calcarenite, limestone, sandstone (upto 40 MPa), and even basalt (requireshydraulic hammering or blasting): each of this soils involve specific technicaland W&T problems, however, the same dredger has to operate in this widevariety of projects, it means that our choices of W&T resistant materialsmostly are a comprise.

• Even on one project the soil might differ considerably: at different depths, various layers are encountered: this complicates the comparisons betweenthe different types of wear resistant materials

• Mostly there is only a limited information concerning the soil, sometimes the infomation is even wrong.

• The duration of dredging projects is in general quite short: a few months: insufficient time to evaluate new W&T solutions

• The components in contact with the soil are subject not only to abrasion butalso to high impact

Unforeseen: hopper loaded with stones, it was specified in the tender as: ‘sand with gravel’

• The fleet is operating worldwide: coördination is difficult

• Remote areas, without repair facilities, no local supply possible, withdifficult acces, sometimes rather unsafe.

• Local regulations (not always clear in advance) complicate the operations: safety, labour, environment, taxes, import, etc

• Contracts have to start on short notice: no time for proper preparation, while the delivery time for W&T parts is several months

• The volumes dredged with one vessel are rather high (from 3000 m³up to 100.000 m³ per day)

• The installed power is high: for cutter dredgers upto 6000 KW on the cutterhead and 16.000 KW on the dredge pumps.

• Planning of the fleet is continuously adjusted

• Weather conditions (Seastate) affect the operations

• The life time of a dredger is more than 30 years, some reach an ageover 40 years

• To start a project large volumes of equipment are to be mobilisedfrom one part of the world to the other: could be more than 15.000 m³, it involves heavy weights (above 300 tons)

• It is a highly specialised job: training of crew and staff is to be donein house.

• HRM: only few people want to work overseas, the job is to be donein sometimes difficult circumstances, its is a process that neverstops (24 hrs a day, 7 days a week), we continuously move fromlocation, the duration of a contract is uncertain.

Maintenance of the JDN dredging fleet

• Dredging vessels, side stone dumpers, sheerlegs, and seagoing split hopper barges (40 units)

• Auxiliary floating equipment (100 units) (tugs, supply vessels, rock barges(with a dwt of up to 12.000 tons), crane pontons, oil recovery vessel, bunker barges, spray pontons,etc)

• Floating pipe lines, self floating hoses, self floating lines with ball joints (dia 700 mm upto 1100 mm), about 8 km.

• Submerged lines and shore lines (dia 700 mm up to 1100 mm) more than120 km

• Land based auxiliary equipment (cable cranes, excators, dumpers, wheelloaders, bull dozers, gensets, welding machines, compressors, etc) and moblile workshops

• Break downs must be avoided!• The target is to achieve a high efficiency of the equipment, with a maximum

of operational hours, and optimal performance of all systems and installations, this is achieved by PREVENTIVE MAINTENANCE

• M+R

Normal maintenance to the ships (dredging vessels, auxiliaryvessels, land based auxiliary equipment) and their machineryinstallations is based on running hours and on time intervals

• W&T

Maintenance to the components in contact with the dredged soils, is dependent on the type of the dredged material– The cargo hold (hopper)– The dredge pumps– The dredge pipes on board,the dragheads– The cutterheads with their equipment– The floating pipe lines– The submerged pipe lines and the pipe lines on shore

Cost per m³ for a cutter dredge (in sandstone, calcarenite, breccia)

15.3%

17.1%

24.2%3.0%

27.0%

11.8%

1.6%

Remuneration.

Repair Provision.

Wear and Tear.

Insurance.

Fuel, Lubs, Greases &

Consumables

Crew Cost.

Superintendence.

74.9%

7.0%

6.2%

2.0%3.1%

0.9%6.0%

CSD : Marco Polo

Floating Auxiliary Plant.

Reclamation Area.

Pipelines.

Workshop.

Survey Equipment & Personnel.

General site overheads.

Cutter dredge in highly abrasive sand and calcareniteCutter dredge in hard limestone

67.5%

8.4%

7.3%

1.1%

13.8%

0.4%1.5%

CSD : LEONARDO DA VINCI

Floating Auxiliary Plant.

Reclamation Area.

Pipelines.

Workshop.

Survey Equipment & Personnel.

General site overheads.

11.3%

9.9%

39.1%

2.4%

25.2%

11.2%

0.7%

Remuneration.

Repair Prov ision.

Wear and Tear.

Insurance.

Fuel, Lubs, Greases & Consumables

Crew Cost.

Superintendence.

81.4%

5.2%

4.4%

1.5%3.0%

1.5% 2.9%

CSD : JFJ DE NUL

Floating Auxiliary Plant.

Reclamation Area.

Pipelines.

Workshop.

Survey Equipment & Personnel.

General site overheads.

22.7%

21.7%

32.2%

3.8%

10.8%

7.9%1.0%

Remuner ation.

Repair Prov ision.

Wear and Tear.

Ins urance.

Fuel, Lubs, Greases & Consumables

Crew Cost.

Superintendence.

Cost for per m³ for a hopper discharging medium size sand

80.6%

2.0%

8.8%

0.7%3.7%

1.0%3.1%

TSHD : JAM ES COOK

Flo at ing Auxiliary Plant.

Reclamation Area.

Pip elines.

Wo rkshop .

Survey Equipment & Perso nnel.

General sit e overheads.

25.0%

20.1%

8.4%4.2%

29.5%

11.1%

1.8%

Remunerat ion.

Rep air Provision.

Wear and Tear.

Insurance.

Fuel, Lubs, Greases & Consumab les

Crew Cost.

Sup er intendence.

Hopper discharging gravel –short sailingHopper discharging medium sand – long distance sailing

84.6%

2.2%

3.9%1.3%

4.2%0.8%2.9%

TSHD : ALEXANDER VON HUMBOLDT

Float ing Auxiliary Plant .

Reclamat ion Area.

Pipelines.

Worksho p.

Survey Equipment & Personnel.

General s ite o verheads.

19.3%

14.7%

26.5%

4.0%

23.6%

10.0%1.9%

R emunera tion.

R epair Provision.

W ear and Tear .

Insurance .

Fuel , Lubs, Greases & C onsumables

C rew Cost .

Super int endenc e.

87.3 %

1.5 %

5.0 %0 .5%2.0 %

1.2 %2 .6 %

TSHD : VASCO DA GAMA

Float ing Auxili ary Plant .

Reclamat ion A rea.

Pipeli nes.

Workshop.

Survey Eq uipment & Personnel .

General s ite overheads.

27.7%

19.8%

13.4%

4.1%

27.7%

6.4% 0.9%

R emunera tion.

R epair Provision.

W ear and Tear .

Insurance .

Fuel , Lubs, Greases & C onsumables

C rew Cost .

Super int endenc e.

Attention for maintenance starts withthe design of new vessels

• Large dredgers are taylor made, unlike cranes or excators theyare not standard machines.

• Choice of the makers: for the major equipment only first classsuppliers are taken into consideration: it means their equipment is reliable, they can give service, they guarantee the availability of spares for the vessels lifetime

• Reduncy of the installations allows repairs (in case of breakdown or preventive maintenance) while the vessel continues itsoperations

• Design includes safety margins – suction pipe of a hopper, cutterhead, dredge pumps

• Acces to components• Critical parts of the hopper plating are given an extra plate

thickness, which allows for wear down of the cargo hold

• The vessels are self supporting, they are equipped with all meansrequired to realize the repairs :

– Stores for the spare parts

– Travelling deckcranes, overhead cranes, other hoisting facilities

– Repair area on deck for heavy parts

– Robots to change cutterteeth on the JFJ De Nul

– Welding machines, with a distribution system over the vessel

– On board workshops with lathes, milling, drilling machines etc

– Extensive set of tools, measuring devices etc

• Depending on the type of vessel, wear resistant materials are chosen forthe equipment in contact with the soil, this allows for longer service life of the components:– Double walled dredge pumps, with hard cast iron pumphousing, special alloy impellers and wearing plates are used forcutterdredgers,and the large hopper dredgers, on other vessels cast steel single walled pumps are installed

– Dredge pipes are lined with Nihard, or made of alloys with high resistance to abrasion for cutterdredgers and pipes in the pumproom of the large hopperdergers (sometimes in combination with FEDUR), on other hoppers cast steel and rolled mild steel pipe pieces are used

– Cutterheads designed for low maintenance: liners protect criticalparts, the teeth system allows for easy and quick maintenance

– Dragheads protected with domite wearing plates– Rubber hoses : equipped with liners or of special design

Double walled dredge pump

Double walled dredge pump

Breakage, cracks and wear of pump components

Double walled pipe

Double walled pipes

Armoured rubber hoses (Velp)

• Oxar or Nihard IV supportingrings are embedded in the rubber (distance 40 mm)

• The rings have a trapezium shape, with the longest leg at the inside diameter,

• This designs allows formaximum flexibility, and givesan optimum protection againstabrasion

• Life time 5 (25) times higher

Rubber hoses

Where flexible pipe connections are to be used, rubber hoses are required

Rubber has a high resistance toround pebbles but is vulnerablewhen the particles are sharp

Therefor a hose is constructed out of short rubber segments lined withsteel cones (allows bending angles of 35°)

The cones are hardfaced with a welding metal, a FeCrTiMoC basis with embedded TiCarbides

The hardfacing is done in open-arc, fully automatic

Draghead

Dragheads (domite blocks, ceramicbushes, easily replaceble teeth)

Suction mouth of a cutterdredge – trimayand domite

Cutter shield (front part of cutterladder) protected with oxarand trimay bars

Cutterhead

Cutter coming up for maintenance

What is specific about Cutters and their equipment

• The cutterheads should have a strenght suitable for continuousmaximum cutter power (on 3 teeth only when dredging rocks), (6000 Kw for JFJ De Nul)

• Angle of attack is to be appropriate for the application: it will bedifferent for sand & clay and for rock

• The teeth must well protect the arms, the adapter and its socketagainst abrasion.

• Optimal transport of the cut material towards the suction mouth

• The teeth must have a high resistance to abrasion

• Even when wearing down teeth should remain as sharp as possible

• A narrow fit of point and adapter, which should remain constant even after a long service time (reliable, insensitive tolerances)

• Safe and quick replacement of teeth

• The teeth and adapters are made of a special alloy cast steel

• Workability limits the weight of the teeth to 25 kg• Replacement of the adapters to be as maintenance friendly as possible:

easy to fit to the correct position, welding to be reduced to a minimum• The cutterhead is a welded construction, made out of cast steel arms, a hub

and a ring.• The cutterring is protected with Oxar liners• The sockets for the adapters are covered with protection shells, built up with

Wolfram carbides (7888 SH)• The consumption of pick points when dredging hard rock can be up to 500

pcs per day, they are exchanged from the cutter platform while the cutter is mounted on the cutterladder.

• In such conditions the cutterhead might be exchanged 2-3 times a day, because adapters are broken, or damaged (eg due to broken points)

• The cutterheads are repaired in a mobile workshop on shore, up to 40 welders (day and night shift) can be involved to realise this job for onecutterdredge

• To work in such conditions 8-10 cutterheads per cutterdredge are required

• For different types of soil, different cutterheads, and typical teethare required, the soil is seldom homogeneous, so the choice of the equipment will nearly always be a compromise.

• The cost of a cutterhead: 200.000 up to 350.000 US $.• Cost for teeth 50 upto 125 US $ per pc.• JDN disposes of enormous stock of teeth and adapters (at least 40.000 pcs)

• For the JDN fleet the yearly cost for points and adapters is at least 5.000.000 €.

• For special applications teeth are covered with Wo Carbides, it is applied in the workshops of specialised subcontractors,by Plasma Transferred ArcWelding or by Spray Fusion. As an alternative the product is simply melted down by heating in our own on the site workshop (only when low cost labour is available)

Flared points covered with Wo Carbides

Test are performed with ceramic inserts, cast in the teeth (Magotteaux)

Cutter maintenance at Dubai Workshop

Cutter repairs at Port Hedland

Marco Polo Changing Cutter and pickpoints

JFJ De Nul Changing pickpoints

JFJ De Nul - Changing a cutterhead

Two parallel shore discharge lines – one standbyfor the other – each 3 km long

Floating lines

Organisation of the technical department

• Newbuilding and development department: 20 engineers, most of them graduated from a university

• Design office: 20 draughtsmen• Amos department to set up the data base with which our spare partsand preventive maintenance is organised

• Fleet managers in Aalst– Technical superintendents on the contract site, in charge for onedredge

– Highly qualified crew on the ships, foremen for the localworkshops

– Local seaman, welders and mecanics• Workshop in Aalst• Logistic department• Quality control

How is W&T monitored

• US thickness measurements of dredge pumps, dredge pipes, hopperplating etc are done at regular intervals, depending on the type of soil that is being dredged, in the most demandingcircumstances readings are taken weekly, they are entered in the data base

• Increase in cutter power and side winch pull indicate that pick pointsare worn

Logistics

– Purchase department: nearly all parts are bought by this department in the head office.

• We avoid local purchasing, to guarantee the best quality, to reduce the cost, to avoid abuses, to allow our local superintendents to concentrate ontechnical matters

• For W&T parts we have suppliers mainly in the EEC and USA, but also in China, India, Australia and Singapore.

– Warehouses in Belgium, inclusive a (9 ha) storage area near Ghent(includes a 300 m long deep water quay), in Dubai, Batam, Honduras, Argentina (all with direct acces to sea).

– Transport department: transport of parts (7 tons airfreight (M+R) and 10 containers a week), mobilisations of plant

Spare parts

• Standardisation of the installations on board of the vessels allows to interchangeparts beween ships, and to reduce the amount of strategic stocks

• JDN invests more than 10 % of the value of the vessel in spare parts (M+R and W&T), for cutter dredgers up to 15 %

• A standard set of wear and tear parts is always on board or near the vessel, it covers normal breakdowns and average wear in normal soils: pumphousings, impellers, wear plates for pumps, cutters, dragheads, complete suction pipes and dragheads forhoppers, cutterheads, teeth and adapters for the cutterheads and dragheads, criticalcomponents in the on board pipelines, a complete set of rubber hoses etc.

• In the Belgian ware houses and overseas storage areas extra strategic stock is keptto cover wear down of unforeseen abrasive soils, and to allow JDN to start even the most demanding new projects on very short notice. This includes huge stocks of pickpoints for cutterheads, pumphousings, impellers, wearing rings and plates, 100 % spares for all the pipe lines on board of a cutterdredge, all cast pipe pieces for the hoppers, and at least in beween 10 and 20 km pipes for submerged and shore pipelines, spare ball joints for the floating lines etc…

• JDN has its own casting models for all wear and tear parts, which makes usindependent from specialised suppliers, and allows us to work with the foundaries we consider reliable

Loading barges at the Zelzate Quay

Zelzate storage area

Storage area Aalst

Batam storage area and workshop

Dubai storage area

Repairs: where and who

• Own crew

• Local reliable workshops

• Repair yards all over the world, mainly in Europe, Middle East, Argentina, China and Singapore

• Repairs are done as much as possible in the area where the dredgers are at work, we seldom deviate the vessels to have repairs done

• Own workshops, in Aalst and local own mobile workshops (ourDubai workshop employs about 120 people)

Port Hedland mobile workshop

Port Hedland Cutter repair shop

Typical mobile workshop for one cutter dredge

Welding workshop in Aalst

Welding workshop in Aalst

Welding workshop in Aalst

Aalst workshop - Maintenance to valve - sheave

Aalst - Machine shop

Surprise: Dynamite encountered, while dredging a

trench in dead coral, in steep cliffs of 18 m high