Download - Factors Effecting Performance
10-06-2014
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Chapter title
FACTORS AFFECTING PERFORMANCE
By Bert van Gent
Dredging and Marine Contractors
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Dredging and Marine Contractors
Dredging…?
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Double production…!
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Breakdown of the dredging process
Overview of dredgers
• Cutter suction dredger
• Trailing suction hopper dredger
• Backhoe dredger
• Grab dredger
• Other equipment
• Environmental dredgers
Equipment
Dredging and Marine Contractors
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1. Loosening the material (and/or dislodging)
2. Picking up the loosened material
3. Transport
• through the primary dredger
• further transport
4. Disposal of the material
• under water
• on shore
Breakdown of the Dredging Process
Dredging and Marine Contractors
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• Hydraulic (erosion, discharge pipe, etc.)
• Mechanical (cutter, conveyor belt, etc.)
Remark
The different sub-processes may require different types of
dredging equipment
Means to realise the partial processes
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1. Hydraulic/mechanical dredgers (CSD)
2. Hydraulic dredgers (TSHD)
3. Mechanical dredgers (Backhoe, Grab)
4. Environmental dredgers
Overview of dredgers
Dredging and Marine Contractors
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Cutter Suction Dredger (CSD)
Hydraulic/Mechanical Dredgers
Dredging and Marine Contractors
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Cutter Suction Dredgers
Mid-size, 600-1500 kW
Small < 600 kW
Large, 1500-3000 kW
Dredging and Marine Contractors
Cutter power
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Mega, 5500-7500 kW Heavy Duty, 3000-5500 kW
Cutter power
Cutter Suction Dredgers
Dredging and Marine Contractors
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• Main characteristics
• Most important parts of the dredger
• Working principle
• Production limiting factors
• Some characteristic figures
Cutter Suction Dredgers
Dredging and Marine Contractors
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Main characteristics
• Nearly all kinds of soils (sand, clay, rock)
• Stationary dredger:
− vulnerable to shipping
− sensitive to wave conditions
• Some are self-propelled for mobilisation
Cutter Suction Dredgers
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Cutter Suction Dredgers - Parts
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Most important parts, machinery
• Cutter head and cutter drive
• Dredge pump(s)
• (Side-) Winches and sheaves for the side
wires for swinging
Cutter Suction Dredgers
Dredging and Marine Contractors
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Working principle
• Cutter disintegrates or dislodges the material
mechanically by rotating cutter head
• Material sucked up and transported through pipeline
by use of centrifugal dredge pumps
• Pontoon movement by:
- swinging around working spud
- progress by successive steps (stepping)
and spuds (spudding)
Cutter Suction Dredgers
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CSD WORK METHOD (1)
Swing
to SB
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Stop at SB,
Push dredger
forward
CSD WORK METHOD (2)
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Start swing
to PS
CSD WORK METHOD (3)
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Continue
swing
to PS
CSD WORK METHOD (4)
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Stop at PS,
Push dredger
forward
CSD WORK METHOD (5)
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Start swing to SB
CSD WORK METHOD (6)
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Stop in
Centre Line
CSD WORK METHOD (7)
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Aux. spud
down
CSD WORK METHOD (8)
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Main spud
up
CSD WORK METHOD (9)
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Main spud
forward
CSD WORK METHOD (10)
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Main spud
down
CSD WORK METHOD (11)
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Aux. spud
up
CSD WORK METHOD (12)
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CSD WORK METHOD (13)
Start
swing
to SB
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CSD WORK METHOD (14)
Continue
swing
to SB
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Process topics
• Over-cutting versus under-cutting
• Spill
• Cutter heads
• Anchors
Cutter Suction Dredger
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spillage
(cutting deeper than design level)
undercutting overcutting
Cutter Suction Dredger
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Cutter head
• Back ring - arms - hub
• Blades - teeth: chisels / pick points
• Various shapes
Cutter with chisels
Cutter Suction Dredger
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Sand/clay cutter head
Cutter Suction Dredger
Rock cutter head
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• Anchors
Depending on soil type
Flipper Delta
Stevshark
Cutter Suction Dredger
Dredging and Marine Contractors
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• Anchors
Anchor islands
Cutter Suction Dredger
Dredging and Marine Contractors
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Production limiting factors
• Soil characteristics
• Available power on cutter
• Side winches (max. power and velocity)
• Thickness and width of the layer to be dredged
• Dredging depth (ladder angle, spuds, cavitation)
• Pumping distance (pump- and pump drive characteristics)
• Shipping
• Waves and currents
• Dirt and debris
Cutter Suction Dredger
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cutter suction dredger small mid-size large
dimensions 65 * 10 * 2 m 70 * 16 * 4 m 120 * 20 * 5 m
(L*W*Dr)
total power < 3,000 kW < 9,000 kW < 13,000 kW
cutter power < 600 kW < 1,500 kW < 3,000 kW
max. swing speed 19 m / min 32 m / min 32 m / min
max. dredging depth 15-20 m 25 m 25 - 30 m
discharge diameter 0.35 - 0.70 m 0.65 - 0.85 m 0.75 - 0.85 m
Characteristic Figures
Cutter Suction Dredger
Dredging and Marine Contractors
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cutter suction dredger heavy duty mega
dimensions 125 * 22 * 5 m 140 * 24 * 6.5 m
(L*W*Dr)
total power < 23,000 kW < 28,000 kW
cutter power < 5,500 kW < 7,000 kW
max. swing speed 32 m / min 32 m / min
max. dredging depth 25 - 35 m 30 - 35 m
discharge diameter 0.80 - 0.90 m 0.90 - 1.00 m
Characteristic Figures
Cutter Suction Dredger
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Cutter Suction Dredger
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Suction dredgers
• Trailing Suction Hopper Dredger (TSHD)
• Plain suction dredger
• Barge unloading dredger
• Water Injection Dredger (WID)
Hydraulic Dredgers
Dredging and Marine Contractors
ing and Marine Contractors
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Trailing Suction Hopper Dredger
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Mid-Size 8,800 m3
Large 13,500 m3
Small, 4000 m3
Trailing Suction Hopper Dredger
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Jumbo 18,000 – 22,000m3
Mega 37,000 m3
Trailing Suction Hopper Dredger
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• Main characteristics
• Most important parts of the dredger
• Process description
• Production limiting factors
• Some characteristic figures
Trailing Suction Hopper Dredger
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Main characteristics
• Free sailing
• Self-propelled
• Self-loading when trailing
• Self-unloading or -discharging
• Seagoing or inland waterway vessel
• All soils (also weak rock!)
• Relatively insensitive for waves
• Not vulnerable for shipping
Trailing Suction Hopper Dredger
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bow-coupling for pumping ashore or rainbowing
suction pipe hopper
service crane
pump room
propulsion
engine room
swell compensator
wheel house
draghead
- 70m
Trailing Suction Hopper Dredger
Dredging and Marine Contractors
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Most important parts
• Dragheads
• Dredge pump(s)
• Hopper, loading and unloading system
Trailing Suction Hopper Dredger
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Dredging cycle
• Loading at the dredging- or sand borrow area
• Sailing (loaded) to the unloading area
• Unloading (dumping or pumping)
• Sailing (empty) to the dredging area
TSHD Process Description
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TSHD Process Description
Excavation (Erosion & Cutting)
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Suction
TSHD Process Description
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Loading Loading (overflow)
TSHD Process Description
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Longitudinal section
Top view hopper
Loading: Basic Principle
TSHD Process Description
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Top view hopper
Full Load: Basic Principle
Longitudinal section
TSHD Process Description
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Text (full)
Hopper loading (mud)
Dredging and Marine Contractors
Total Volume [m3]
Draught [m] (=tons)
Max.
draught
Max. volume
Mud [m3]
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Text (full)
Hopper loading (sand)
Dredging and Marine Contractors
Draught [m] (=tons) Max.
draught
Overflow losses
Sand [m3]
Total Volume [m3]
Max.`volume
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Sailing loaded
TSHD Process Description
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Discharge
TSHD Process Description
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Rainbowing
Hopper Self-discharge: rainbow
TSHD Process Description
DDredging and Marine Contractors
ng and Marine Contractors
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Hopper Self-discharge: Pump ashore
TSHD Process Description
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Text (full)
TSHD Process Description
Dredging and Marine Contractors
Hopper Self-discharge: system
Dredge pump
Jets Jets
Water
Sand
Jets
Water inlet Discharge
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Text (full)
TSHD Process Description
Dredging and Marine Contractors
Jets Jets
Dredge pump
Jets
Water inlet
Hopper Self-discharge: system
Discharge
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Text (full)
TSHD Process Description
Dredging and Marine Contractors
Jets
Water inlet Discharge
Dredge pump
Jets Jets
Hopper Self-discharge: system
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Text (full)
TSHD Process Description
Dredging and Marine Contractors
Jets Jets
Water inlet Discharge
Dredge pump
Jets
Hopper Self-discharge: system
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Sailing empty
TSHD Process Description
Dredging and Marine Contractors
start overflow
DRAUGHT (m)
start
dredging
stop
loading
sailing
loaded
emptying hopper
sailing
empty
TIME IN MINUTES
Cycle-time per trip
next
trip
TSHD Load Graph (emptying by bottom door disposal)
VOLUME SAND (m3)
TOTAL LOAD (ton)
Dredging and Marine Contractors
start overflow
DRAUGHT (m)
start
dredging
stop
loading
sailing
loaded
unloading
hopper
sailing
empty
TIME IN MINUTES
Cycle-time per trip
next trip
VOLUME SAND (m3)
TSHD Load Graph (discharging to shore)
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Process related topics
• The hull
• The hopper
• Dragheads, suction pipes and belongings
• Centrifugal pumps
Trailing Suction Hopper Dredger
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The hull
• Sailing characteristics
• Resistance
• Small keel clearance
• Maximum carrying capacity versus draft, length and width
• Strength
• Stability
Trailing Suction Hopper Dredger
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The hopper
• Carrying capacity
• Volume
• Weight
• Filling system
• Overflow system
• Bottom door disposal system
• Self-discharge system
Trailing Suction Hopper Dredger
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Hopper: carrying capacity
Restriction by volume (full hopper)
Restriction by weight (max. draught)
Low density soils
e.g.: Mud - 1.2 ton/m3
5,000 x 1.2 = 6,000 ton
High density soils
e.g.: Sand - 2.0 ton/m3
3,500 x 2.0 = 7,000 ton
HOPPER
HULL
MUD
5,000 m3
6,000 ton
HOPPER
HULL
SAND
3,500 m3
7,000 ton
Dredging and Marine Contractors
Overflow System
Conical bottom-valves
Bottom-doors
Hopper: loading & dumping facilities
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Dragheads
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Sand Draghead
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Different dragheads
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Suction Pipe
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Workability – Weather Delay
DrDredging and Marine Contractors
edging and Marine Contractors
Swell
Compensator
Draghead Winch
Pressure
Jar
Seabottom
Swell Compensator
Oil
Draghead
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Centrifugal Pumps
Hardware
• Types & sizes
• Basic parts
inboard pump under water pump
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Working principle
• Energy Distribution
• Propulsion
• Pumps
• Boardnet
• Centrifugal pump
Centrifugal Pumps
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Density & velocity meter
Engine-room with 2 pumps in line
Centrifugal Pumps
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Production limiting factors
• Soil characteristics
• Available propulsion power
• Drag head size and weight
• Keel clearance when loaded
• Dredging depth
• Pumping distance (pump- and pump drive characteristics)
• Waves and currents
• Dirt and debris
Production may vary a lot due to these factors
Trailing Suction Hopper Dredger
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Limiting factors
A drag head grid damaged by boulders
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Limiting factors
Dirt and debris
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trailing suction small mid-size large
hopper dredger
dimensions 55*10*4 m 90*18*7 m 130*23*9 m
(L*W*Dr)
max. dredging 10-35 m 25-55 m 25-75 mdepth
hopper capacity <4,000 m3 <8,000 m3 <15,000 m3
sailing speed 8 knots 12 knots 14 knots
propulsion power 400 kW 3,500 kW 8,000 kW
diam. suction-pipe 0.35-0.9 m 0.80 m 0.90-1.00 m
Trailing Suction Hopper Dredger Characteristic Figures
Dredging and Marine Contractors
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trailing suction jumbo mega
hopper dredger
dimensions 180*32*13 m 225 x 38 x 12 – 15.5 m
(L*W*Dr)
max. dredging 50-120 m 55 - 155 mdepth
hopper capacity <30,000 m3 30,000 - 46,000 m3
sailing speed 17 knots 16 - 18 knots
propulsion power
(while dredging) 18,000 kW 26,000 kW
diam. suction-pipe 1.20 m 1.2 - 1.4 m
Trailing Suction Hopper Dredger Characteristic Figures
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Trailing Suction Hopper Dredger
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Suction Dredgers
• Plain Suction Dredger
• Barge unloading dredger
• Water Injection Dredger (WID)
Other Hydraulic Dredgers
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• Suction of free running material (sand)
• Jet water for dislodging and fluidising material
• Deep suction pit necessary
• Stationary dredger, not swinging, only intermittently moving forward
Plain suction dredger
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Barge Unloading Dredger
• Unloading of barges by suction
• Jets for dislodging and fluidising
• Barge to be shifted alongside the dredger during suction
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Water Injection Dredger
• Injection of water into bottom
• Low pressure and high capacity
• Fine sand and silt
• Movement of material due to gravity forces (density current)
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Backhoe Dredger
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Backhoe Dredger
Mega backhoe Simson, 3460 kW
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• Main characteristics
• Typical parts
• Dredging cycle
• Production limiting factors
• Some characteristic figures
Backhoe or Hydraulic Excavator
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Main characteristics
• Normal backhoe/front-shovel on pontoon or
• Specially built pontoon (with spuds) with backhoe on rotating table
• Dredged material is loaded into barges
• Reasonable cutting force can be generated
• Suitable for:
• “Non-rock” type soils with stones
• Blasted rock
• Precision dredging
Backhoe
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Dredging blasted rock
Backhoe
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Bucket
Stick Boom
Backhoe - parts
Spud
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• Different types and sizes to be fitted:
• Sticks
• Buckets
• Booms
• Positioning with spuds
Backhoe
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Dredging cycle
• Lowering bucket
• Filling bucket by cutting and tilting
• Hoisting bucket
• Turning crane towards barge
• Emptying bucket into barge
• Turning back
Backhoe
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overlap Nett dredging width
Centre line
Reach
Barge
Working Method Backhoe
Preferred working direction:
backwards
=> Higher production
=> Less spill
But…
Forward dredging is also possible
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• Work method
• Excavation force at large depth
• Slope dredging (bucket positioning)
• Precision dredging along quay-walls
• Soil and obstructions
• Hard material (no rock)
• Big boulders
• Removal of debris or vegetation
• Workability
• Waves
• Shipping
Production Limiting Factors
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Backhoe Small Medium Large Mega
Length m1
30 45 50 65
Draught m1
1.5 2.0 2.5 3.5
Dredging Depth m1
10-15 15 - 20 20 - 30 20 - 30
Bucket size m3
1 - 3 2 - 8 5 - 20 15-40
Power Installed kW 500 < 1,000 < 2,000 < 4200
Backhoe Characteristic Figures
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Backhoe
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Grab Dredger
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• Main characteristics
• Dredging characteristics
• Typical parts
• Dredging cycle
• Production limiting factors
• Some characteristic figures
Grab Dredger
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Main characteristics
• Can also be used for construction works (shore & bank protection)
• Normal grab-crane on pontoon
OR
• Specially built pontoon (with spuds) with fixed grab-crane on rotating table
• Small grab dredgers for difficult accessible areas
Grab Dredger
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Dredging characteristics
• Dredging up to large depth’s
• Cannot create an even bottom
• Dredged material is loaded into barges
• Non-rock types of soil
• Suitable for debris and vegetation
Grab Dredger
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Areas with difficult access
Grab Dredger
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Groyne Construction
Grab Dredger
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Typical parts
• Different types and sizes to be fitted:
• Grabs
• Booms
• Positioning with spuds or anchors
Grab Dredger
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Standard grab (sand, clay, mud)
Cactus/Polyp grab (stones)
Grab Dredger
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Dredging cycle
• Lowering grab
• Closing grab
• Hoisting grab
• Turning crane towards barge
• Emptying grab into barge
• Turning back
Grab Dredger
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Production limiting factors
• Hard material
• Big boulders, blasted rock
• Removal of debris or vegetation
• Dredging depth
• Waves and currents
• Shipping
Grab Dredger
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Grab Dredger Small Mid-size Large
Dimensions L x Dr. 30 x 1.5 45 x 1.7 50 x 2
Dredging Depth m1 25 40 50
Grab size m3 2.5 - 5 5 - 15 15 - 50
Characteristic Figures
Grab Dredger
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• Bucket ladder dredger (BLD)
• Dipper dredger
• Rock breaker
• Plough or bottom leveller
Other Mechanical Dredgers
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Bucket Ladder Dredger
• Revolving chain of buckets
• Swinging like a cutter suction dredger
• No spuds, position fixed by wires
• Buckets turning upside down to empty
• Discharge into barges
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Buckets are turning upside down to
discharge into barges
Bucket Ladder Dredger
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Bucket Ladder Dredger in Action
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Rock Breaker
• Hydraulic power to break rock
• Assists dredger on small spots
• Broken rock to be removed by excavator
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Plough or Bottom Leveller
• Towed by tug
• Assisting TSHD with removal of ridges and high spots
• Removal of soft material from small harbours
• Low production
• Cheap
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121
Water based
• Barges
• Work boats and launches
• Anchor pontoons, floating line pontoons
• Booster station
Other Equipment
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Survey launch
Multicat for handling and transport
A-frame for anchor handling
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Floating pipeline pontoons
Rubber floating pipeline
Use of floating pipeline
Dredging and Marine Contractors Dredging and Marine Contractors
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Floating cover
Female Ball Joints Male
Rubber Floating Line
Dredging and Marine Contractors Dredging and Marine Contractors
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Booster station
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Land based • Pipelines and valves
• Bulldozers, shovels, etc.
Other Equipment
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• Objective
• Types
• Typical Aspects
Environmental Dredgers
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Objective:
Environmental Dredgers
• Optimise precision
• Accurately dredging of thin layer
• Minimise disposal capacity by high concentration (minimisation of
dilution)
• Minimise turbulence and turbidity
• Safety: bring dredged bottom material via closed system to barge or
disposal area
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H H D Clean
Contaminated
Contaminated material is left behind, and falls in overdepth
Accuracy Aspects
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D increased, H not removed H (contaminated) removed
Accuracy Aspects
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Typical aspects
Environmental Dredgers
• Automation necessary
• Maximising concentration
• Controlling excavation level
• Controlling layer thickness
• Output level low due to:
• High accuracy
• Avoiding turbulence
Dredging and Marine Contractors
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Types
• Environmental disc cutter dredger
Disc cutter head with closed bottom plate and shields
• Environmental auger dredger
Dual active rotating auger in enclosed area
• Horizontally closing grab
Grab sealed off when closed
• Hydraulic excavator fitted with closed visor bucket
• Encapsulated Bucket Ladder Dredger
Environmental Dredgers
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Disk bottom (cutter) dredger
disk cutterhead with closed bottom plate and shields
Environmental Dredgers
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Environmental Auger Dredger
Environmental Dredgers
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• Grab is horizontally closing
• Sealde off after closing
Environmental Dredgers
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Standard Grab
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Horizontally Profiling Grab
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Environmental Dredgers
Hydraulic excavator fitted with closed visor bucket
Dredging and Marine Contractors