Cranes – Design, Practice, and Maintenance phần 7 doc

hatch-Sensors The following sensors are used on a container quay crane: – An infrared sensor system underneath the trolley for measuring thesway angle in the direction of trolley travel

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Cranes – Design, Practice, and Maintenance 190

Fig 6.10.1 Hardware topology

spreader onto the twistlock castings which are used to lift the covers of a ship

hatch-Sensors

The following sensors are used on a container quay crane:

– An infrared sensor system underneath the trolley for measuring thesway angle in the direction of trolley travel and the spreader skewangle (SPFS) This sensor may also be used to periodically verifythe main hoist position as a redundant check on the primary posi-tion instrument in the drive

– Four two-dimensional (X and Y ) laser scanners on the trolley areused to locate the corners of the spreader, container, chassis orAGV with an accuracy greater than plus or minus 20 mm on 35 mdistance

– Each of the two corner units contains two high speed laser scannerswhich measure the exact location of the corners of the spreader,

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Sagging, Rock and Roll, Positioning, and AEI 191

Fig 6.10.2 Sensor arrangement on a trolley of a quay crane

container, chassis or AGV One corner unit monitors the watersidecorner and the other the landside corner The waterside corner unitalso includes the laser range ﬁnder which monitors the stack proﬁleand it also can peer into the hold of the ship

A laser range ﬁnder is mounted underneath the trolley and isused for stack proﬁling It measures the distance without the use

of dedicated reﬂectors, and can achieve an accuracy of plus andminus 10 mm at distances of up to 40 m (PSS)

– A laser range ﬁnder is mounted on the backreach of the crane for

an absolute position check of the trolley (APIS)

Learn cycles

First, the crane driver has to handle a container in a normal mannermanually, before the automatic mode is used (Where anti-collisiondevices are not used, Overhead Bridge Cranes (OHBCs) will not require

a learn cycle.)

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Chassis Alignment Systems

Special camera-based vision systems may be employed to enhance theprocedure of aligning the transportation equipment (truck chassis,bump-car, road chassis, etc.) under the crane The vision-type imagingsystem may use natural or artiﬁcial light sources or structured lightsources Based on the image processing, the system indicates to thetruck chassis driver when the chassis or container is aligned with thecentreline of the crane In addition, the same image processing is utilized

to automatically position the trolley over the chassis兾container andautomatically adjust the skew angle of the spreader to match that ofthe chassis兾container The system indicates to the crane operator whenthe chassis position is outside the allowable skew angle which wouldallow landing of the spreader The crane is equipped with a visual sig-nalling system that indicates to the truck driver when he is approachingthe correct position, when to stop, and when he has overshot the correctalignment position

Container Recognition Systems

Camera-based imaging systems are also employed to automaticallyrecognize the identiﬁcation numbers printed on the sides and兾or ends

of the containers moved in the terminal As the operator moves thecontainer to or from a vessel, cameras located at multiple locations onthe crane capture the ID number The ID number is then passed over

a data network to a Yard Management System for processing TheYard Management System then issues orders or instructions to the yardtransportation equipment for proper dispatch of the container

Yard Management Systems

The cranes may be supplied with wireless RF, optical ﬁbre, or guide communication technology to interface with a Yard ManagementSystem The Yard Management System directs the movements of theground trafﬁc, yard stacking crane, and the ship to shore cranes Thesensors used on board the cranes for the various automation functionsdiscussed previously, are utilized to establish reports to the Yard Man-agement System that include container size, container weight, containerpick-up coordinates, container drop-off coordinates, twistlock posi-tions, etc

wave-Acknowledgement

Source of information for Section 6.10, Mr John T Sholes, GE ToshibaAutomation Systems, Salem, Virginia, USA

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Fig 6.11.1 Deﬁnition of the geometry

Patrick Stevedores Pty Inc and the Australian Centre for Field ics (ACFR) at the University of Sydney have recently developed a fullypatented reeving system for the hoist mechanisms of container cranes:the Stewart Platform Reeving Figure 6.11.1 shows the schematic lay-out of the reeving, while Fig 6.11.2 shows the 1:15 scale working model

Robot-of the installation

The ﬁgures show the six hoisting wire ropes of the system When thesix wire ropes are independently controlled, the six spatial degrees offreedom can be used for complete control of the load by ‘microposition-ing’ The reeving system then gives an excellent stiffness; trim, list, andskew can then also be implemented in the system

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Fig 6.11.2 The 1:15 scale working model

Stewart Platform reference:

D Stewart A platform with six degrees of freedom Proc Instn Mech.

Engrs (London), Part I, 1965, 180(15), 371–386.

6.12 Checking the alignment of containers etc with

Laser Scanners

Lase GmbH Industrielle Lasertechnik of Bremen, Germany developed

a fully patented Laser Scanning System with which the distancesbetween the spreader and a container, an AGV or trailer, etc., as well

as the relative position of these parts to each other can be measured.When setting down a container on to – or taking a container from –

an AGV, the misalignment between the container and the AGV, as well

as the relative distances between spreader and container or AGV can

be controlled by using the Rotating Laser Scanners, in combinationwith an Evaluation Unit, being a supervisory PC If misalignments areindicated, a crane driver or checker can correct the positioning.Figure 6.12.1 gives an overview of the system; Fig 6.12.2 shows themeasuring and positioning of the scanners at some 22 m above the quaylevel; and Fig 6.12.3 shows one of the ZPMC cranes, equipped withthis system

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Fig 6.12.1 Overview

Fig 6.12.2 Positioning of the scanners

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Fig 6.12.3 Crane with laser scanners

The scanners have a cone-shaped scan which gives a cone diameter

of approximately 2,8 m over 20 m height The cone-circle is scanned insteps of 0,25 degrees

Nelcon’s ‘1 over 4’ or 5-high Automated Stacking Cranes (ASCs) areprovided with a special ‘rope tower’ wire rope device for the hoistingmechanism Due to the way of reeving and the lay-out, this rope tower

is very stiff and permits the (fully automated) ASC to stack the tainers accurately on top of each other

con-However, under extreme conditions, e.g a heavy storm, it is possiblethat the required stacking accuracy cannot be met For this purposeBTG Engineering BV in Maasdam developed a fully patented SpreaderPositioning System, which controls the eventual sway or swing of thespreader

The spreader itself is therefore provided with hydraulic cylinders,which are controlled by the PLC in the crane On the spreader a box is

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Fig 6.13.1 ASCs with Spreader Positioning Systems

Fig 6.13.2 Box with PSD chip

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mounted in which a LED system throws a beam of light towards a boxunderneath the trolley In this box a PSD chip (Position SensitiveDevice Chip) and a special lens are mounted The beam of the LEDsystem is guided through the lens and hits the PSD chip Through thischip the PLC gets the various commands to activate the hydraulic cylin-ders on the spreader, thus forcing the spreader with the underhangingcontainer to change its position

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Fig 6.14.2 Overview of the system

the work area, the winches, etc The camera of such a system is shockand vibration proof and is extremely light sensitive The system givesthe crane driver a much better feel for his work As the lenses of thecameras are heated, condensation and frost have no inﬂuence on thecamera

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Chapter 7

Construction and Calculation Methods

on Strength and Fatigue

7.1 Materials

(A) For steel constructions

Table 7.1.1 Table of corresponding former designations

Designation Equivalent former designation in

Acc to

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Table 7.1.2

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Construction and Calculation Methods 203

Pipes

52 N pipes are supplied in a normalized condition The normalizingtemperature is approximately 920°C After the required temperaturehas been attained over the entire cross section, the pipes are cooled off

in the air The stress relieving temperature is 530–580°C

The 0,2 yield strength is min 340 N兾mm2; the tensile strength min

460 N兾mm2, the elongation is 20 percent

a higher output and a more homogeneous weld Widely used methodsinclude the following

Manual Metal Arc or MMA-welding

MMA-welding or welding by hand is mostly used for welding steelplates, angles, etc of material quality Fe 360 or Fe 510 (S355)

The welding has to be done with basic electrodes of a high outputtype The skill of the welder is most important to achieve good qualitywelds

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Fig 7.2.1 The welding of a big box girder

MIG-welding

This is a gas-shielded Metal Arc welding, which is carried out using acontinuous wire electrode The continuous wire electrode is fed auto-matically into the welding gun, where the shielding gas is added to thewelding process The weld is then shielded by a stream of Metal InertGas (MIG), which is a mix of CO2and Argon

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Fig 7.2.2 Welded pipe constructions

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MAG-welding

Following the same process as given under MIG-welding a MetalActive Gas (MAG) is where 100 percent CO2is used for the shielding.The MAG process gives a rather deeper penetration than the MIGprocess

Submerged arc welding or SAW-welding

In submerged arc welding an arc is maintained between the work andthe end of a cored wire electrode, which is continuously fed into the arc

by motor driven feed rolls The arc is invisible and operates beneath alayer of granular ﬂux, some of which melts to provide a protective slagcover over the weld pool

There are hand-held welding guns available, however submerged arcwelding is principally done with fully automatic equipment It is par-ticularly suitable for long straight joints of a very high quality, whichare laid in a ﬂat position

Flux Core Arc-welding

This type of automatic welding can, among others, be used in the ing of pipes and tubes The welding wire which gives slag, is of theRutyl type and includes a small percentage of Nickel, giving a ﬁne weld-ing result

weld-Dangers: the prevention of problems

Cracks, which are of course dangerous, can occur in welds, and fore the welds have to be controlled carefully This can be done byvisual, ultrasonic or X-ray inspection and by methods in which pene-trating liquids with a magnetic control system for cracks is used

there-It is always most important to avoid H2 (Hydrogen) The carboncontent of the materials must also be kept as low as possible

The shrinkage of a construction during the welding process must becontinuously controlled, and extra tensions in the construction due toshrinkage must be avoided to prevent cracks or even break-downs.The cooling off of the weld and its surroundings must be kept withinallowable limits It is, therefore, necessary to preheat thicker construc-tions before welding in order to prevent the weld cooling-off too quickly

in relation to its surroundings

Welders

Welders must be well trained for their job Their qualiﬁcation goes from1G up to 6GR

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Possible detrimental phenomena resulting from welding

Among others, these may be:

– differences in chemical position, grain size and stress levels betweenthe weld and the parent material may lead to different corrosionrates In most cases the weld and heat affected zones are attackedpreferentially;

– stress corrosion cracking

Fig 7.2.3 Reduction of the sensitivity to lamellar tearing

Fig 7.2.4 Submerged arc welding

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The types of bolts now widely used are ‘High strength’ types 8.8 and10.9 These marks are shown on the head of the bolt and on the nut.8.8 means: min tensile strength: 80 kN兾cm2

min yield strength: 8B8 G64 kN兾cm2

10.9 means: min tensile strength: 100 kN兾cm2

min yield strength: 10B9 G90 kN兾cm2

The plates which are bolted together must be painted with special paint

on those places where the bolts are used Sometimes injection bolts are

Table 7.3.1 Bolt characteristics

Tensile Tightening Prestressing friction Transmissible tensile

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Fig 7.3.2 Flange plates with injection bolts

Fig 7.3.3 A bolted A-frame construction

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used in heavy construction in order to eliminate the free space whichpops up when the holes in the connection plates do not mate to eachother properly

7.4 Construction of box and lattice girders, etc.

When riveting used to be the main method to connect materials, allcranes and unloaders consisted of lattice constructions Since weldingreplaced riveting, box constructions have become more and more popu-lar Most cranes and unloaders are built up from box-type elements.However, it must be stated that welded lattice girders often can giveexcellent solutions for girders, booms, jibs, towercranes, etc

Fig 7.4.1 Heavy load erection crane

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Fig 7.4.2 Riveted construction

Fig 7.4.3 Bolted construction

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Fig 7.4.4 Welded construction

Fig 7.4.5 Lattice girder construction

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Fig 7.4.6 Flange plate construction

Fig 7.4.7 von Karman strips

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Typical girder constructions

Figures 7.4.8 and 7.4.9 give examples of single and double box girdersand lattice girder constructions

Fig 7.4.8 Double box girder construction

Fig 7.4.9 Single box and lattice girder construction

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Fig 7.4.10 Lattice girder

Fig 7.4.11 Detail of a lattice girder

In single girder constructions the trolley hangs underneath the girder.With double girder constructions, the trolley runs above or in betweenthe girders, thus giving a lower height crane than with the single girderconstruction The legs are normally built of box girders or tubes andsill beams, mostly of box girders These are normally welded Howeverfor erection duties, ﬂange plates or lap plates are used, which are boltedtogether Tubular constructions must be controlled as they become sub-ject to von Karman whirls Wind and storm frequently cause vibrationsdue to these whirls in tubular constructions Special calculation pro-grams are available to check this phenomenon and can indicate if thevibrations are likely to become dangerous and lead to damage

Tiêu đề	Cranes – Design, Practice, and Maintenance
Chuyên ngành	Cargo Handling and Crane Automation
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