CARGO HANDLING

March 2007 27

WorldCargonews

Accidents and emergenciesinvolving quayside cranesare occurring more fre-

quently in ports around the world.Portek’s own “case load” has risenfrom four or five incidents a yearto more than 12. Its overall assess-ment is that frequency of incidentswhere damage exceeds US$0.2Mhas risen to around 40 a year.Based on a global population of4000 quayside cranes, this com-putes to a probability of about 1%.Incidents normally, but by nomeans always, involve insuranceclaims and repairs could cost any-thing up to US$2M per crane.

The number of incidents isunderstandable, says the company,given the big rise in crane num-bers, increasing crane dimensionsthat result in reducing visibilityand operator control, and morefrequent adverse and unpredict-able weather conditions.

But in some cases, too, there isinsufficient understanding of theincreasing risks and demands of afast-paced, modern terminal andstandards of crane maintenanceand safety in operating procedureshave been allowed to slip.

Human factorA crane accident is defined by Portekas an unplanned and unintentionalevent involving one or more cranesor other objects that result in damageor injury of some kind and it nor-mally involves a strong human ele-ment in its causation.

For example, in a collision be-tween a ship and a crane, one orboth is under control of an op-erator and hence there is an im-mediate human element involved.Such accidents tend to be moreoften preventable than not.

In one case handled by Porteklast year (in Dunkirk), the flare ofa ship’s bow hit the inside face ofa crane leg in the direction of gan-try travel and moved the cranesome way along the quay, causingbending of the leg and sill beam.Damage was relatively minor andwas confined to one plane.

Apart from collisions betweenship and crane, a crane may con-tact another crane or an objectduring operation. When cranescontact each other due to strongwind gusts during operation, amultiple chain collision is oftenthe result. In another incident inthe Caribbean (Port of Havana)attended by Portek last year, windgusts possibly exceeding 20 m/secblew a working crane along thequay into the adjacent crane thatin turn pushed a third crane intoits dead stop. The portal structureof the second crane and the bo-gies of the third crane sustainedsevere damage.

EmergenciesA crane emergency is defined byPortek as an unexpected and sud-den event in which the crane issubject to damage but its causa-tion is not immediately linked tothe operator and is generally notpreventable by him. Examples arecrane structural failures and cranecollapse, derailment or severedamage due to typhoons or earth-quakes. Sometimes electrical firesbreak out in the diesel generatoror electrical room, or crane drivefaults lead to free fall of the load.

Mechanical faults such as brakeor twistlock failure can result inuncontrolled fall of load. Struc-tural damage may be caused byfatigue failure, by poor workman-ship or design, or by heavyweather during ocean transporta-tion of cranes, perhaps because thelashings and bracing were inad-equate. In other words, humanfault is often involved, but “re-motely” from the incident itself.

There are typically two phases

in any crane accident or emer-gency incident. First, the recov-ery phase comprises survey, salvageand stabilisation. This refers to theprocess of survey and damage as-sessment, temporary bracing tostabilise the crane to prevent fur-ther damage, and isolating opera-tional cranes from the damaged,non-operational crane(s), so as toallow operation to resume in part.

The second phase covers re-pairs and re-commissioning andrefers to design and analysis, sub-mitting proposals for repairs, ob-taining approval from insurers andport authorities, and carrying outthe repairs in shortest time possi-ble, conducting checks, testing andrecommissioning the cranes sothey can be returned to operation.

Isolation zoneBracing and support for cranesfacing imminent danger of furtherinstability or collapse has to becarried out immediately, usuallyrelying on common sense andsound engineering practices in theabsence of detailed analysis. Thecrane has to be isolated and con-tained so that the berth can con-tinue partial operation.

Immediately after an incident,surveyors or claim executives ap-pointed by the ship or crane own-er’s insurers would have been no-tified and deployed to site. At thesame time, crane specialists suchas Portek or others would also becalled by respective parties to as-sess damage jointly and to under-take some emergency measures tostabilise the crane. The damagesurvey report would form the ba-sis for the various parties to agreeon actions to be taken.

Visual inspection is usuallyable to throw up most of theareas in need of repairs. Non-destructive testing (NDT) maybe performed in certain areas ifneeded. Dimensional checksusing theodolite survey instru-ment will be able to determinethe degree of structural deflec-tion or deformation, and theextent of repairs and correctionneeded to bring the crane backto required tolerances.

If the crane is somehow tan-gled up with a ship or other ob-jects, it must be freed as it is dan-gerous to have the ship and thecrane bobbing up and down withthe tide. Scraps on the quay wouldbe cleared, and the crane isolatedto allow port operations to con-tinue around it

Typical damages could includebending and buckling of the legsand sill beams, derailment of wa-terside or landside bogies, bend-ing of legs and sundering of jointsbetween the equaliser beam andsill beam.

Boom time bluesThe most common ship/cranecollision occurs when the flare ofa ship’s bow hits part of the crane.Usually, however, the most seri-ous damage occurs when a shipsnags a crane boom in the downposition. If the ship catches oneend of the crane boom it has along lever arm and can easily bringthe crane down.

More generally, damagedbooms pose a real headache asthey may need to be taken downfor repairs. This usually neces-sitates calling up a heavy dutyfloating crane for removal andreinstallation after repairs, acostly affair. Boom hinges may be

damaged and in situ line-boringwill be needed.

Claims, compensationLiability pertaining to equipmentsuch as a quay crane comes underthe FFO (“fixed or floating ob-ject”) clause of a shipowner’s thirdparty liability insurance policy, orthe hull and machinery or P & Iinsurance. Consequential damagesresulting from lost production mayalso be claimable from the insureras, for example, was the case at acoal terminal serving a powerplant in Indonesia.

One might think that in anemergency situation, all partieswould act expeditiously to cometo an agreement on the claim andreturn the damaged crane to op-eration as soon as possible. In re-ality, however, it could take any-thing from just a few hours to daysor months or even years for theparties to reach agreement.

It is not unusual for a craneowner to claim a higher amountthan the insurer is prepared to pay,or to insist on a brand new re-placement crane. The final out-come is a matter of negotiationinvolving the insurance loss adjust-ers and what the crane owner isprepared to accept.

In some cases, the crane owner,especially if it is a port authority,may take a hard-line approach by(attempting to) put the vessel un-der arrest, as was the case recentlyin an incident in the Port of Mo-bile that involved a fatality.

RepairsCrane structures are designed tolift vertical loads and can tolerateonly limited horizontal loads from

wind and earthquake conditions.They are not meant to absorbhorizontal impact loads arisingfrom collisions with ships or ad-jacent cranes. Any slight impactfrom the ship can result in drasticdeformation and distortion of theportal structures, or total collapse.

It is often useful to construct anumerical model of the cranewith finite element stress analysissoftware. The impact forces aresimulated and correlated to thereal life scenario. The simulation

Crane accidents and how to prevent them** This article is based on “Crane Ac-cidents and Emergencies: causes, repairsand prevention,” a paper by LarryLam, chairman, Portek International,S C Tok, technical director, Portek In-ternational and Peter Darley, director,Portek Systems & Equipment

Typical ship/crane collisions - craneboom that struck a ship’s funnel(above) and waterside crane leg hitdiagonally by ship’s bow. (ibid)

A damaged crane should be braced andsupported immediately to prevent furtherinstability or collapse. (Source: Portek)

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WorldCargonews CARGO HANDLING

The joint at the equaliser beam has becomeseparated and twisted. (ibid)

Portek explains that as derailment (top picture)allows displacement, damage to the sill beamor leg is often much less severe than when thebogies stay on the rail (lower picture), due tothe sever bending forces. (ibid)

results can be used to help understand thebehaviour of the crane structures underimpact and to identify the extent of af-fected areas and possible points of failurenot seen by the naked eye. They also helpthe repairer to determine the correctpoints of support and design the correctrepair methods, and even improve thecrane beyond its original design.

Spring backAs noted above, it is vital to constructsupports for the crane to ensure that it isstable, and to bear the weight of that por-

tion of the crane where repairs are to becarried out. Considerable potential en-ergy, associated with elastic deformation,remains “locked” in the deformed struc-tures. These structures tend to spring backviolently as restraints are removed andhence care must be taken to avoid seri-ous injuries or damage.

Repairs normally involve cutting awaythe damaged plating. This tends to releasethe “locked” energy, allowing the struc-ture to spring back somewhat to its origi-nal form. Jacking or heat application maybe needed to get the structure fully backto its true form. New plating is then fab-ricated and installed.

In the case of bolted joints construc-tion, it is advisable to replace the bolts ifthere is any chance that they have beenstressed and weakened. Electrical damages

are normally confined to power supplytrailing cables being overstretched or bro-ken, or cable reels being crushed. Theseitems have a long lead time, and new ca-ble should be ordered immediately toprevent recomissioning being delayed.

Geometry checkOn completion of repairs, X-ray NDTshould be carried out on the welds in therepaired areas, as well as on other criticalwelds to ensure that hitherto undetectedcracks are identified and dealt with. Thecrane’s geometry in terms of perpendicu-larity, diagonality, trueness of hinges, etcshould be checked to ensure they arewithin tolerance. If the original tolerancecannot be maintained, the parties involvedcan agree on various measures such asadditional reinforcement, or a regime of

monitoring the crane over a period oftime to ensure there is no deterioration.

Better than cureModern container cranes are behemothsof steel and machinery, often fabricatedin a hurry in low cost countries. The com-plexity of such huge and hence highlyflexible structures, subject to fatigue load-ing and exceptional impact loads, are stillnot fully understood. Crane ownersshould be more aware of the risks. Thereis no substitute for a rigorous risk man-agement scheme that includes stringentsafety standards in crane design and manu-facturing, day to day operating proceduresof the crane and the terminal as a whole.

Visual surveys to check for structuralcracks have to be carried out rigorouslyonce a year. At longer intervals the inter-nal faces of the girders need to be in-spected. This often throws up manufac-turing faults; insufficient welding and lackof penetration are common cause of fail-ure. The terminal manager should ensurethat equipment maintenance standards arenot compromised by a busy schedule orthe operations department not releasingcranes for maintenance.

Usually the load test as witnessed by aprofessional engineer does not amount tomuch. It is nothing more than just a for-mality and says very little about the safetystandard of the crane. The crane ownercannot rely on such regulatory certifica-tion; it only gives a false sense of security.

BrakesIt is common for sudden strong windgusts to act on a crane under operationand propel it along the rail, out of opera-tor control, until it collides with an adja-cent crane. In Portek’s view rail clampsare ineffective and so are motor-mounted,multi-disc brakes, which are inaccessiblefor servicing, and deteriorate over time.

According to Portek, the trend todayis to install electro-hydraulic thruster discbrakes in each gantry drive. They shouldbe selected to ensure ample braking ef-fect and should be able to generate suffi-cient sliding friction between the wheeland the rail to prevent a runaway situa-tion. To provide even more braking power,caliper brakes acting directly on the idlewheel can be installed.

In ports subject to strong winds, it isvital that cranes are gantried to designatedpoints to have the storm locking engagedwhen the crane is not in operation. It isalso advisable to gantry the cranes andpark them in a safe spot during shipberthing manoeuvres. The harbour mas-ter should ensure that harbour tugs de-ployed have sufficient power and bollardpull to control the ship’s movement. Theship’s captain and pilot should try to en-sure the ship comes alongside as parallelto the quay as possible.

The importance of safety training forthe operator cannot be overemphasised.Emergency drills have to be ingrained.Drivers should be trained like airline pi-lots on how to react in any emergencysituation. For example, the natural ten-dency in a crane run-away situation is todrive against the wind. But this onlymakes things worse, as when gantry mo-tion is activated, the gantry brake wouldbe open, thus further reducing friction. ❏

Wnd gust effects: a chain collision of three cranesthat left two inoperable. (Ibid)