Development of Large-Sized
Mobile Harbor Crane
Noriaki Miyata
Toshihito Shimotsu
Nobuhito Iwamoto
Masaki Nishioka
Wataru Mizunuma

With the recent trend toward containerization, it has become necessary for local small and medium-sized harbors to
use mobile harbor cranes that are capable of handling containers as well as other general cargoes in different styles.
Hence, demands for large-sized mobile harbor cranes, which are self-traveling and versatile but do not require any
additional civil works to increase the bearing strength of foundation soil, are increasing. Mitsubishi Heavy Industries,
Ltd. (MHI), using its latest crane technology, has recently developed a mobile harbor crane that is differentiated fromother commercially available models in its easy-to-operate characteristics: (1) crane operation without interferencewith on-deck 13 rows by 5 stacks containers loaded on Panamax size containerships, (2) capable of handling 40.6 toncontainers, (3) interlocking dual-axis anti-sway function and (4) oblique traveling by independent steering mechanism.
bile harbor crane.
It is designed to handle containers loaded on a40 000 DWT Panamax size containership and hoist 40.6ton containers. The crane also has a sufficient slewing
radius for use as backup of a container crane. To increase
the cargo handling efficiency, the operating speed of eachaction is higher than that of conventional rubber-tired
cranes. The crane is equipped with both swivel hook andexpandable spreader as hoisting tools to meet the requirement for most handling needs of containers.

1. Introduction
A general outline of the mobile harbor crane is as follows.
It consists of a traveling device with rubber-tired wheels
for traveling freely on harbor areas, outrigger and a craneunit to load and unload cargo onto or from a ship. The traveling device of the crane consists mainly of a frame fortraveling, an outrigger device, a steering device and an
operator's cab. Rubber-tired wheels are used when thecrane travels, and an outrigger is used to support the craneunit during cargo handling operations. The crane unit consists of a slewing device to swing around the crane unit, aluffing device to raise the jib and a hoisting device to liftcargo. Cargo handling operation is performed by the threedifferent actions of the crane: slewing, luffing and hoisting.
In addition, various types of cargo such as containers,
general cargo, lumber and bulk cargo can be handled bychanging the lifting tools.
A mobile harbor crane, when compared to a gantry crane
fixed on rails installed on the wharf, is a low-cost, lightweight facility that does not require large-scale civil works
for reinforcement of foundation or installation of otherwharf equipment such as rails and power supply unit, reducing the initial equipment investment. Also, in handlingof cargo, it can be used to rearrange stacks of cargo on thewharf yard as well as loading or unloading them on or froma ship. Thus, a mobile harbor crane has the feature of versatility and accordingly can be used to handle cargo invarious ways.

3. Features of the MHI large-sized mobile harbor crane
Mobile harbor cranes used in small and medium-sized
Table 1 Main specifications
Applicable containership class (DWT)
On-deck container stacks

2. Main specifications
Table 1 shows the main specifications of the MHI mo-40 000
13 rows by 5 stacksRated hoisting capacity(t)

65, max.

Applicable container

(t)

40.6

Slewing radius

(m)

53

Lift: above GL(m)35

Lift: below GL(m)-12

Hoisting speed(m/min)0 to 72

Luffing speed(m/min)

Avg. 60

Slewing speed(rpm)

1.2, max.

Traveling speed(m/min)67

Outrigger span(m)13.0Outrigger spacing

(m)

13.5

Outrigger load

(t)

220

Maximum load on wheels

(t)

19

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 Extra No.2 (Jan. 2003)1

126 m13 x 5 rows

Reach: 53 m max.

10 000 DWT containership

Fig. 2 Top view of 10 000 DWT class containership
The working range of this crane covers the overall length of a
10 000 DWT containership.
Handling of containers
loaded on Panamax size
containership

5. Interlocking dual-axis anti-sway function
In operating a conventional mobile harbor crane, slewingof the boom for positioning can lead to secondary sway inthe radial direction following sway in the slewing direction under centrifugal force, as shown in the left top
Fig.. 3. As it is not easy to suppress such comdiagram of Fig
plex sway, crane operators need to reduce the slewing speed
and rate of acceleration to minimize its occurrence. That is
one of the obstacles to increasing the efficiency of cargohandling operations. A relatively long period of time is alsoneeded for acquisition of the required crane operating skill.
To solve this problem in developing a mobile harbor
crane having higher cargo handling efficiency regardlessof the operators' skill, MHI has completed the interlocking
dual-axis anti-sway function for the purpose of sway prevention and positioning.
On the basis of the results of the analytical investigations made on the cargo handling operation, the hoisting
and lowering controls of this crane are designed not for
automatic operation but as an operator-assisting function
for moving horizontally.
5.1 Interlocking dual-axis operating function
The sway caused by centrifugal force can be reduced byminimizing the centrifugal force produced during slewing
operation. Centrifugal force is proportional to the squareof the peripheral velocity and inversely proportional to theslewing radius. However, it is not practicable to sacrificecargo handling efficiency for reduction of peripheral velocity. The solution is to make the slewing radius infinite, thatis to make the trajectory of the top end of the moving boom
a straight-line, as shown in the left bottom diagram ofFig. 3. Thus, no centrifugal force is produced, and accordingly, no sway perpendicular to the straight-line moving
direction is developed.
Consequently, the lifted cargo sways only in the moving
direction as primary sway. To use this principle, a straightline connecting a start point and an end point is drawn toobtain the moving distance of the lifted cargo. Next, a speedcommand to move the top end of boom along the straightline trajectory is determined by using the moving distanceas shown by the curve in Fig.. 3. The speed command isdivided into the slewing speed command portion and theFig. 1 Sectional view of Panamax size containership
Crane operation without interference with any part ofthe containers stacked on the ship's deck in 13 rows
by 5 stacks is possible.

harbors are, in many cases, required to have a performancecomparable to that of gantry cranes in cargo handling capability and maneuverability.
The crane introduced in this paper has the features described below to meet these requirements:(1) This crane is designed so that its boom does not interfere with the top edge of the stack of containers when it
is operated to handle on-deck 13 rows by 5 stacks containers on Panamax size containerships, while theconventional cranes need to be operated while taking
care not to touch the on-deck cargo.
(2) It can hoist heavy-weight containers (40.6 tons), which
are now increasing by replacing ordinary 30.5-ton containers.
(3) It is equipped with interlocking dual-axis anti-sway function that relieves crane operator from sway control andimproves maneuverability and cargo handling efficiency.
(4) It is equipped with independent steering mechanismand oblique traveling function to improve maneuverability and efficiency in bringing the crane alongsidecontainerships, in addition to the conventional curve
traveling function.

4. Cargo handling range
Fig
Fig.. 1 shows a sectional view of a Panamax size
containership. This crane is designed to be capable of handling containers without interfering with any part of the13 rows by 5 stacks containers on the ship's deck. Morespecifically, the boom pivotting point is located high enoughto prevent the boom from interfering with the corner of thetop containers, and the operator's cab is installed besidethe jib supporting point for ease of operation.
FigFig.. 2 shows a top view of a popular containership(10 000 DWT class). As the working range of this cranecovers the overall length of a 10 000 DWT containership,neither relocation of crane nor shifting of ship is necessary. It offers increased cargo handling efficiency.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 Extra No.2 (Jan. 2003)

2End pointSecondarysway occurs.

Boom top-end moving speed(straight-line moving direction)

m/s
1.5
1.0

Peripheral
sway

Stop point

0.5

Boom
05101520

Radial sway

253035404550(s)Dividing into slewing
and luffing speeds

Start point

Slewing operation

deg / s6Slewing speed

4End point

20

Only primarysway occurs.

Boom-2

Sway in straight-line
moving direction

05

1015

deg / s12025(s)

3035

4045

50

35404550

Luffing speed

0-1Interlocking dual-axis
straight-line operation

Start point-20510152025(s)30Fig. 3 Interlocking dual-axis anti-sway function
Sway is suppressed by jointly controlling slewing and luffing operations.

Operating instructions given
through this panel

Coordinate presetting
Fig. 4 Touch panel screen

Land-side container grounding direction

Easy input through touch panel screen is possible.

luffing speed command portion. These two different commands are jointly applied to the boom operation so thatthe top end of the boom moves along a straight-line trajectory for slewing and luffing.
5.2 Anti-sway control function
Primary sway still occurs in the direction of straightline movement during the interlocking dual-axis operation.
To suppress the primary sway, a field-proven feedforward
anti-sway system is employed. In addition, the mobile harbor crane has a real-time speed compensation function thatmaintains the anti-sway effect regardless of the length of

the hanging wire rope, because the wire rope length changes
with luffing operation being performed by the level luffing
function, and also because the hoisting operation is carried out manually by the operator.
5.3 Touch panel control
The interlocking dual-axis anti-sway operation of themobile harbor crane can be easily controlled on the touch
panel screen shown in Fig
Fig.. 4 and with the switches on theoperation console.
Firstly, coordinate presetting is made on the touch panel
screen to determine the position of the containership relaMitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 Extra No.2 (Jan. 2003)

3

ContainershipMoving through curves traveling

Oblique travelingFig. 5 Steering function for traveling
Independent hydraulic steering mechanism is adopted for moving through curves and oblique traveling function.

tive to the crane. For coordinate presetting, two arbitrary
containers are selected from the array of containers on theship displayed on the touch panel screen, the spreader isbrought to the actual position of the first selected container
by manual operation, and the preset key is depressed. Whenthe same procedure is repeated for another container, thecoordinate presetting is completed. The actual operationcommand is given to a target container by simply designating it on the screen. After the target container has been
lifted to a safe level in the air by manual hoisting operation, the joint operation start command is given. Theinterlocking dual-axis anti-sway function then starts working automatically and the positioning of the container tothe designated position is started. Even if the length of thewire rope varies with the intervention of manual hoisting at
this stage, the anti-sway control function remains valid withthe support of the real-time speed compensation function.
In addition, when the lifted container is being unloaded on the wharf, it is possible to give an instruction
to ground it parallel to or perpendicular to the wharf.
Also, the lifted container can be automatically turned
around in the air by swivelling the hook so that all thecontainers are unloaded in the same direction. In thisway, the mobile harbor crane can be used for various
cargo handling operation.

Furthermore, each axle is synchronously controlled inorder to minimize tire wear and axle load.

7. Conclusion
MHI has developed a large-sized mobile harbor cranesuitable for use in small and medium-sized harbors. Demand for the crane is expected to increase further becauseof the following features:(1) Crane structure allowing container handling operation
without interference with on-deck 13 rows by 5 stacks
containers on Panamax size containerships,(2) Capable of handling a 40.6 ton containers, which arebecoming increasingly popular in the industry,(3) Interlocking dual-axis anti-sway function that improves
maneuverability of crane and cargo handling efficiency,and(4) Independent steering and oblique traveling mechanismthat improves maneuverability of the crane for positioning close to a ship.
From now on, MHI will explore the possibilities of further improvement of functions through verification tests
and cargo handling operations, using the mobile harbor
crane in actual operations for improvement of its maneuverability and cargo handling efficiency.
Hiroshima Machinery Works

6. Traveling function
The hydraulically operated traveling device consists ofan outrigger unit, a steering unit and a common hydraulicunit for compact design.
The steering unit is provided with an independent hydraulic steering mechanism and feedback control to satisfy
Fig.. 5 , whenvarious traveling conditions. As shown in Fig
rounding a curve in the usual manner, the rear wheels aresteered in the opposite direction to the front wheels to makethe turning radius smaller. When adjusting the crane tothe position of a ship or in a similar steering operation, thefront and rear wheels can be steered in the same direction
to perform oblique traveling for ease of position adjustment
or to bring the crane closer to the ship.

Noriaki Miyata

Toshihito Shimotsu

Hiroshima Research &Development Center,
Technical Headquarters

Masaki Nishioka

Nobuhito Iwamoto

General Machinery &Special Vehicle
Headquarters

Wataru Mizunuma

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 Extra No.2 (Jan. 2003)

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