Unique Approach to Dredge Design
Andy Anderson*
Hickey Marine Enterprises, Inc., Vancouver,
Washington (WA), D/B Sea Horse dredging
in the Columbia River.
T
he conversion of a barge mounted Dravo crane into a digging cycle, clamshell dredge is not an uncommon
project in the North American dredging industry. In 2005, when Cliff Larsen, president, and Doug Larsen,
superintendent, of Hickey Marine Enterprises, Inc., Vancouver, Washington (WA), began designing a
machine that would excel in all of its operations, they ran up against the age old problem of having to
make compromises.
The Larsens really wanted to have a good performing crane as well as a good producing digger. They understood
the limitations in the traditional systems but felt it was time to look outside of their comfort zone for alternatives.
Together with their design team they listed their needs and investigated options.
Needs
* High Production dredging capabilities;
* Smooth and efficient craning capabilities;
* High Torque and High Speed swing control;
* Exceptional bucket control.
Traditional Approach
The traditional approach to the design of a clamshell
dredge and marine construction crane is to use a triple
drum winch driven by a single power source, with the
operation of the drums controlled by, clutching in the
drums with frictions for lifting or lower with the water brake and declutching the drums to lower, while
using band brakes to control the lowering speed.
In this style of operation the rearmost drum would
be the topping hoist. The front two drums would be
geared together to turn synchronously to lift the holding and closing lines and would drop the load, still
geared together, driving a water brake to lower the
load. To change to a construction crane mode, one of
the two front drums would be geared to the input drive
to act as the heavy lift line and the lowering of that
load would be accomplished by declutching it from
the prime mover and controlling the lowering speed
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Hickey Marine winches
WORLD DREDGING Mining & Construction,
November 2007
with a band brake.
For most conversions the dredges had a tendency to be good at one task
and only fair at the other. When the winch was set up for a strong digging
cycle it lost something in the controllability needed for good craning, and
vice versa. After much investigation of various possibilities the Larsens’
decided to modify the traditional approach.
They would use a two drum winch assembly for the holding and closing line winch. However, for the other main function components they
would employ the advanced technology of a direct fluid drive with electrohydraulic controls. Hickey Marine had used a direct fluid drive for a topping hoist on a previous crane and other local cranes had used the direct
fluid drive for the swing on several previous projects. All were pleased
with the performance.
They decided to have a separate winch just for the heavy lift line due to
the difficulty of setting up the friction clutched double drum winches for
both dredging and craning. They chose direct hydraulic drive style winches
because of their proven controllability and ruggedness, in addition to the
space saving compact design of these winches. Using a separate identical
winch for topping allowed them to lift and top (or dig and top) at the same
time. The separate winch gives them superior control over the method of
using a third drum on the main winch, eliminating the need for multiple
steps in the traditional style winch – brake to a stop, engage the friction,
select a gear, engage the gear, and throttle up the engine.
This decision also met the requirements the fairly recently imposed
rule by OSHA, ASME B 30.8-1993 Section 8-1.6 regulation — requiring
the topping hoist to be constantly coupled to it’s prime mover and having
a suitable retarder.
D/B Sea Horse’s
swing motor.
New Design Components
They turned to Charlie Sawyer of Sawyer Systems LLC, Vancouver, WA, for the design, manufacture and
installation of the direct fluid drive systems.
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7
Unique Approach to Dredge Design
(from pg. 7)
Topping Hoist and Heavy Lift Winches
Andy Anderson of Special Projects, in Orting, Washington, (formerly with Hagglunds Drives, Inc.) designed
identical winches for both applications and served as project manager for the conversion. He used a standard
variation of the Hagglunds Viking Hydraulic motor style winch which has a very high mechanical efficiency and
produces sufficient torque to directly drive the winch drum without a gear reduction. These characteristics allow
absolute control of torque, eliminate external shock and allow very precise control of position and speed.
Due to their special characteristics, hydraulic motors from Hagglunds Drives, Inc. were chosen to drive all of the
crane’s functions except the holding and closing line winch. Andy called on Dale Laurin of Delcon Service, Gold
Canyon, Arizona (AZ), to review the design integrity of the winches, engineer the tolerances and make the manufacturing drawings. Lee Hayes of Hayes Engineering, Edmonds, WA, did the finite element analysis of the critical
structures of the winch. The winch base and drum were made by Machining and Fabrication of Kent, WA.
The winches have a bare drum diameter of 40 in. with 42 in. between the flanges and 1660 ft of 1 1/8 in. wire on
four layers. Driven by the MB84 Series Hagglunds motor, the winch produces 36,000 lbs. of line pull on the fourth
layer at 143 ft per minute with an input of 3500 PSI pressure and 87 GPM flow. The motors are each driven by P14S
Parker Denison hydrostatic transmission pumps.
In this type of system the flow output of the pumps is electronically controlled and the output of each pump is
directly plumbed to one of the Hagglunds motors without the need for a directional control valve. This creates a very
stiff and responsive coupling of energy input to energy output.
For this system, a flow combiner valve was installed so both the pumps’ flow can be combined to drive the
Topping Hoist at higher speeds. All of this is in a winch package of 88” W X 54” D X 60” H.
Sawyer Systems built and installed the hydraulic systems, including the 200 hp tandem pump power unit which
includes the circuits for brake release and motor case flushing, in a small 90” W X 38” D X 98” H package.
The winches have a manifold mounted directly to the motor that has the double redundant braking counter
balance valve and the mechanical brake auto release logic components.
Ratcheting Lock Mechanism
An additional feature of the heavy lift winch and topping hoist is the ratchet lock mechanism (drum dog). They
use the Hagglunds spring engaged, hydraulically released, flat cam style of ratchet rather than the typical pointed
pawl escarpment type. This brought several advantages, since the flat cam style allows for a less radically pointed
tooth form, is somewhat smaller, and the meeting of two flat surfaces are more secure than the escarpment style.
D/B
Sea Horse’s
Main Drum
Aux. Drive.
8
Swing Control System
As important as it is to have a good power and controllability for the crane
and dredge lines, it is perhaps even more important for the swing. Here again,
the direct fluid drive was a natural for the application, providing superior power
with good responsiveness of control, and the ability to float on command.
Sawyer Systems built the Swing Control System quite similar to the one they
had previously built for American Construction’s D/B Patriot. Two CA70
Hagglunds Compact Motors produce a combined 15,900 lb. ft. of torque at 41.25
rpm. They each drive a pinion through the bull gear with a ratio of 27.5 to 1
and rotate the house at up to 1.5 rpm with 437,300 lb. ft. of torque.
Sawyer’s proprietary Swing Control System uses a joystick for the Sea Horse,
although pedals can also be used. The operator moves the stick to the right or
left in the direction he wants the boom to swing. The further he moves the stick,
the faster the house rotates in direct proportion to the movement of the stick.
As the operator moves the stick back towards the center, the rotation slows,
being hydraulically-dynamically braked since the stick controls the flow of the
hydrostatic transmission pump. As pump and motors are directly plumbed in a
hydrostatic transmission loop, the motor is held between two columns of oil,
the oil from the pump to the motor and the oil from returning motor to the
pump. This system is very ridged providing precise response to input control.
However, when the operator wants the boom to swing according to its own
momentum he moves the stick to neutral which causes the pumps’ compensators to go to zero pressure while providing whatever flow the motors need to
float. If the momentum creates more speed than the operator wants, he simply
moves the stick across neutral in the opposite direction and he will get hydraulic-dynamic braking in proportion to the percentage of input to the 100% posi-
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Hickey Marine Enterprises, Inc., Vancouver,
Washington (WA), D/B Sea Horse dredging
in the Columbia River.
tion of the stick.
Each hydraulic motor has an integral multi-disc wet brake to provide a 2:1 safety factor parking brake that
automatically breaks the rotation whenever the house comes to a full stop.
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9
Unique Approach to Dredge Design
(from pg. 9)
Constant Tension Tag Line Winch
Hickey Marine was worried about control of the bucket - how
to keep it from rotating on its main lines while still allowing the
operator to have the freedom to manipulate the bucket for even
loading of a barge. Previous mechanical systems had proved
troublesome. This was solved with a Sawyer Systems Powered
Constant Tension Tag Line Winch. Here again, the superior control is due to the high mechanical efficiency of the direct drive
fluid motor. The pressure at which a line can be held stationary
in tension can be precisely controlled with basic electro-hydraulic valves. Without the gear slip that would be present in a gear
reduction, the difference between rendering line and hauling line
is quite small.
Using an electronic joy stick and a potentiometer the operator can haul or pay the line with the stick and leave it in any
position within the range of the swing of the bucket, or he can
use the potentiometer to set the desired tension. From there the
operation is hands off, as the winch holds the tension constant,
rendering line as the bucket lowers and bringing in line as the
bucket rises. The controls can be set to manual and the Tag
Line winch can be used as a standard winch within the designed
range using the joystick for a payout and haul in control.
Sawyer Systems Powered Constant
Tension Tag Line Winch
Main Drum Auxiliary Inching Drive
When the dredge was first being designed and the characteristics of the traditional systems were being discussed,
the Larsen’s wondered if they could also solve a prevalent dilemma with holding and closing line winches - not
being able to move the line slowly and precisely or
to power the pay out direction. Their concern was
the various winch maintenance problems compliSwing Tag
cated by the typical controls of the friction mulLine and
tiple drum winches.
Inching
The challenge was to apply a motor to one of the
Drive Power
main drums, freewheeling it most of the time, but
Unit.
then when low tension, precise position or powered pay-out work was required on the winch (such
as setting the line, attaching the beckets or relubing the line) using the motor to turn the drum?
The Larsens and Sawyer working together designed
and implemented the Main Drum Auxiliary Inching Drive for the main drum.
Sawyer Systems was able to design and build a
motor mount and manifold for the Main Drum Auxiliary Inching Drive to accomplish the desired function, because the Hagglunds Compact motor could
be freewheeled by pressurizing its case. The hollow shaft design of the motor allowed the compressed air line into the center of the main drum shaft for the frictions.
Hydraulics would be provided by the Tag Line Winch power unit which would be idle at that time. The main winch
joystick was rigged with a switch to alternately use it to run the Main Drum Auxiliary Inching Drive. An additional
control panel was put near the winch so a mechanic could operate it as he was watching the line on the drum, and
another control panel put inside of the forward door of the house so he could operate it while watching line on the
boom.
Electronic Controls
As the construction of the dredge progressed and the proportional control of the hydraulic systems were being
discussed, Hickey Marine asked Sawyer Systems if they could apply the same performance concepts to the rest of the
crane’s controls. Sawyer Systems complied by designing a system with electronics over pneumatic controls rather
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WORLD DREDGING Mining & Construction,
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Hickey Marine Enterprises, Inc., Vancouver,
Washington (WA), D/B Sea Horse dredging
in the Columbia River.
than using the traditional style direct pneumatic controls.
The electronic control system uses electrical proportional controls at the operator’s station and electrical signals
go to proportional pneumatic valves at the winch. In the direct pneumatic system, the controls at the operator’s
station are pneumatic valves themselves and the signals going to the actuators at the brakes and friction clutches are
columns of compressed air contained inside of tubing running from the operator’s station to the winch.
The primary advantages of electro-remote system are that the speed of the electronic signals are much faster than
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11
Unique Approach to Dredge Design
(from pg. 11)
the pneumatic, and the electronic controls come with a much better range of adjustments to tailor the intuitive feel at the operator’s console to a very precise degree.
As the electronic controls are now much smaller they can all fit into two consoles
attached to the arm rests of the operator’s chair. Additionally, the logic functions
can be done with electrical or electronic components through a programmable logic
controller, also done at the speed of electricity rather than the speed of pneumatic
flow, making the interlocks seem seamless and instantaneous rather than sequential and delayed.
Improved Control and Productivity
Hickey Marine Enterprises’ new Dredge Barge Sea Horse owners, operators and
customers have noticed improved control in the new systems. The winches and
controls have brought rave reviews from operators Darrell Jameson and Phillip
Stacey, for the ease of use, maneuverability, and intuitive control. The superior
performance of the Sea Horse is because:
* Direct Hydraulic Drives allow excellent control of torque, position and speed;
* Powered Constant Tension Tag Line Winch allows exceptional control of the
bucket;
* Swing Control System provides a smooth and precise operation;
* Main Drum Auxiliary Inching Drive allows the holding and closing lines to
move slowly and precisely;
* Electronic Controls are fast and intuitive;
* Ratchet Holding Lock mechanism allows a secure lock.
Operator Cabin
with Remote Controls of
the Winch System.
Improved control translates to faster production. Production cycle times are also improved by having the topping
hoist as a separate winch which allows the dredge to top at the same time it is lifting. The D/B Sea Horse was able
to make its first commercial lift due to the new design using separate winches for the topping hoist and heavy lift
because, while the holding and closing line winch assemblies were incomplete, the crane systems were finished.
The D/B Sea Horse is presently dredging in the Columbia River. While its maximum production rate has not
really been challenged, its digging cycle is about one minute and fifteen seconds producing 4,000 yd3 in a 24 hour
day. Doug Larsen is waiting for an opportunity to prove it can do substantially better.
*Andy Anderson, Special Projects, Orting, Washington (WA); T: 253 389 5547, E: andy1@[email protected]
Hickey Marine Enterprises, Inc., Vancouver,
Washington (WA), D/B Sea Horse dredging
in the Columbia River.
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