Being aware of ground conditionsalso applies to equipment working free on wheels

October 2011 cranes & access 43

The first feature in 2006 was aresult of reviewing the first fullyear of online accident reports onour web-based news serviceVertikal.Net. The original aim ofpublishing this information was toquickly establish the facts andhelp quash the increasingly exaggerated rumours that used tocirculate after every major craneor platform accident.

While this ‘fact’ reporting hasachieved the original objective, theregular reporting of most crane andlift accidents on a worldwide basishas highlighted other issues, including the fact that there are farmore accidents than most peoplerealised and what causes cranes,aerial lift and telehandlers to tip over.

It was not too long before the firstrepercussions occurred. A cluster offatal aerial lift accidents in whichusers were thrown out of the platform because they were notwearing harnesses caused severalrental company owners, managersand safety specialists to get togetherand devise the ‘Clunk Click’ harnesscampaign. Co-ordinated through theInternational Powered AccessFederation (IPAF) it has largely transformed the use of harnessesand short lanyards on boom lifts.

Over the past six years Cranes&Access has taken anin-depth look at the temporary surfaces needed to support and spread high point loadings from lift equipment to prevent tipping and sinking. This includesoutrigger mats for cranes and aerial lifts as well ascrawler crane mats and tracking.

Spreadingthe load

outr iggersc&a

either they are not set at all, or notextended to match the load chartrequired. Most often the loadapplied to the ground has not beenspread widely enough for theground conditions i.e. no mats ormats of the wrong size have beenused.

lifts. The campaign includes a firstclass short video entitled ‘IPAF-Spread the Load’ which clearly andsimply demonstrates the importance of using mats under outriggers and stabilising jacks.

UK loader crane association ALLMI

Similar but less stringent rules willalso apply to mobile cranes in theUSA as new rules come into force.The Department of Labor/OSHArecognised that poor outrigger setup along with lack of operator

Raising the awareness of accidents – ledto the highly successful IPAF Clunk Clickcampaign.

A secondary and perhaps morewidespread issue has been that ofoutrigger related accidents, oftendue to the lack of mats or propercribbing under outriggers. Statisticsindicate that the vast majority ofcrane and aerial lifts tip overbecause of outrigger problems -

The situation has certainly improvedsince 2006 with far more users andoperators now aware of the need to use mats, at least on soft or uncertain ground conditions. But the number of outrigger-related ‘incidents’ is still ridiculously high.IPAF has recently launched a campaign- ‘Spread the Load’ stressing the importance of checking out the ground conditionsboth for units with outriggers andequally important, for those thatwork free on wheels such as self-propelled booms and scissor

has also introduced a programmehighlighting the need to spread outrigger loadings. New loadercrane regulations stipulate maximum ground loadings and putthe onus on manufacturers and suppliers of cranes to keep groundbearing pressures to levels less likely to cause ground failures.These include the automatic monitoring of outrigger extensionsand jack loadings, relating theresults to an overload device/ratedload capacity limiter.

Most incidents involving the ground giving way indicate that no outrigger mats were used at all

A rare case of the ground giving way under a decent mat - clearly a void or softer ground than planned for was the cause

44 cranes & access October 2011

outr iggers c&a

training are a major cause of craneaccidents and it has included clauses in its legislation that ithopes will improve the situation.

While there is now a great deal offocus on the issue of outrigger matsand reducing point loadings, manycrane and lift users are still obliviousto the issue. This is particularly trueof smaller aerial lifts which hasspurred IPAF to step up its campaign. At the recent APEX powered access exhibition inMaastricht at least one third of thetruck mounted and spider lifts wereset up without mats under the outriggers. The exhibitors arguedthat the machines were set up onsolid paved areas or thick concretefloors and so they were notrequired. In all likelihood they werecorrect - the internal floors at theexhibition centre are built to withstand far higher point loadingsthan the machines on display couldever inflict and the interlockingblocks in the outside area it could be argued act like a mat.

However many internal floors arecovered with carpet which hidesnumerous voids and cable ducts andchannels which would clearly nothave taken the weight. On top ofthat, manufacturers at an exhibitionought to be setting an example tousers. If all operators got into theroutine of always putting mats undertheir outriggers we could drasticallycut the number of overturning incidents, save lives, reduce injuriesand improve economic efficiency byeliminating the knock on effects ofmajor accidents.

Doing it rightWe were pleasantly surprisedrecently when a delivery driver of atransit flat bed truck and smallPalfinger loader crane arrived at ouroffices with a bulk bag of gravel.The driver pulled into position andautomatically got out his nylon matsand set up the outriggers beforedoing anything else. The jack to therear of the lifting arc was on interlocking blocks and the operator- employed by Banbury-basedNichols - could easily have just putthat one down without the mat. Infact there are those who would nothave bothered to have put the jackdown at all. It was quite obviousthat given the load and the groundthere was no need and yet he clearly had a well-practiced routineof always using them - saving the20 to 30 seconds was not an option.When we asked he said: “It takes notime and it would not be worth myjob to forget them.” This is the attitude that manufacturers need tohave at trade shows and in advertising literature so that theyplay their part in making the use ofmats second nature.

Staying with loader cranes ALLMIhas issued a document and simplespread sheet-based programme thatnot only explains the importance ofusing outrigger mats but also automatically works out the sizerequired for various ground conditions based on a few simpleinputs such as load, radius and outrigger spread.

Bone idle or ignorant?So why don’t all operators behavelike the above mentioned deliverydriver? As we covered in great detaillast year there are several contributory factors. Ignorance orlack of training, call it what you will,is certainly one, although it is hardto say if this is the most commonreason or laziness is? On numerousoccasions we have received photographs of an accident scenewhere the outrigger jacks havepunched through or sunk into theground causing the crane to tip andyet there on the crane’s deck - are aset of mats. The worst case wehave covered involved an incident inwhich a crane operator sadly losthis life in a bizarre ‘double whammy’. The crane - a 100 tonneplus telescopic - was set up onwhat looked like a firm hardcore surface in a refinery. The operator

had a set of medium sized steelplates on board to use as spreadermats, however at least two of themats were stowed on the deck ofthe crane while he was carrying outhis last routine lift -none had beenused under the outrigger jacks.While placing the load, one of theoutriggers punched through theground surface into some kind ofsmall void or area of softer material.The jack’s small pad created a neathole showing that at that point, theground surface was little more thana crust over a void. The cranelurched over as it lost stability, theboom tip and load then hit theground preventing a full overturn. As the crane started to move, the operator - not sure what was happening - jumped clear of the cabto the ground, just in time to be virtually decapitated by one of thesteel outrigger mats sliding off thedeck of the crane. While this operator was very unlucky he wouldhave been alive today if he hadbothered to use the mats providedwhich would have spread the loadover a sufficiently wide area to haveprevented the incident entirely.

Several outside exhibitors at APEXdid not use mats

While the indoor floors at APEX aresolid, there are voids, many of which arehidden by carpet.

ALLMI – supported by new standards –is aiming to reduce point loadings onloader cranes, where mats are often notused or even supplied

The mat on the unloading side on the drylawn. At the rear a mat was used oninterlocking blocks - not necessary butstill good practice.

The driver wonders why the camera?

46 cranes & access October 2011

outr iggers c&aSecondly, with the mat being usedon the ground it would not havesliced his head off. And finally, if hehad remained in the cab he wouldhave avoided the first two failingsand even escaped injury as the loadwas obviously close enough to theground that the crane was unlikelyto do a flip.

Ease of useModern mats are clean and easy touse, so there really is no excuse notto employ them every time the outriggers are set. On larger platforms or on cranes where largermats tend to be the norm, it helps ifthe mats are stowed in an easy toreach location. Not only does thisencourage their use, but manualhandling rules and risk assessmentsdemand it. Many crane rental companies install rear mountedstorage chests allowing circularmats to be rolled out rather than lifted. When even larger steel matsare required some form of mechanical handling is essential.Most of the larger truck mountedaerial lift manufacturers offer aboom mounted device to lift andplace such mats although Dutchaccess company Debru has developed a unique steel mat handling trailer for its 70 metreWumag - see Handling big mats.

Last minute changeof plans

We have mentioned lack of training/ignorance and laziness astwo of the most common causes ofoutrigger related accidents, butthere is also a third common cause- lack of planning or last minutechanges to a pre-agreed plan ofwork. An absolute classic scenariothat causes overturning is a changeof route while moving a fully rigged

crane with its outriggers raised.Many wheeled or narrow trackcrawler cranes can be moved in thisway while rigged, but doing sorequires meticulous planning with athorough risk assessment and ideally an aviation-type check list. Atypical accident scenario involves acrane moving along a well-plannedroute but encounters a blockage orrestriction along the way. In a properly planned move this has tobe a temporary obstruction, as theroute would have been walked,checked and any obstacles factoredin. ‘Obstacles’ can be as simple as aparked vehicle with no driver insight and in such a case the craneshould park up, lower its jacks andwait… However on a busy site withstrict time pressures and a handfulof observers walking along sideincluding a site manager…. there israrely any shortage of advice for thedriver. With the advice to drive hiscrane around the obstacle beingalmost deafening. After all “it’s thesame level ground so you are notreally changing the plan!” Many acrane operator will crumple in theface of a so much high poweredadvice, especially as the clockkeeps on ticking. So he takes thedetour and on more than one occasion in the past two years theground is nowhere near as level asthe planned route and over goes thecrane and the client’smanager/supervisor is more thanlikely to develop a case of amnesiarelating to his earlier insistence toget on and drive around the obstacle! A good operator shouldstick to his guns – after all if anything goes wrong it is not theoverbearing site supervisor whoselife or job is most at risk. Another cause which often relates

to deviating from the plan alsoinvolves the human frailty of forgetfulness and with the averageage of crane drivers on the rise thismay well become more prevalent?Examples include the setting up of acrane in a restricted width space, or

outriggers were not extended onthat side! Once again the favour isquickly forgotten in the chaos thatensues.

Some of the latest cranes and truckmounted aerial lifts automaticallymonitor this and will not allow the

Leaving the mats on the deck does not help with flotation.

Here is a nice storage set up for both mats and cribbing timbers

When moving a fully or partially rigged crane plan the route carefully and do not deviate unless there is good cause and the new route is thoroughlychecked out first

more typically to leave a lane in theroad behind open for passing traffic.The crane has been set up to carryout one or more lifts over a 180degree range on one side of thecrane, so no problem at all – as longas proper mats have been usedunder the jacks of course. Duringthe work or at the end of it someone on site asks the operatorto place, pick or reach something onthe other side of the machine – as asort of last minute favour. The oper-ator, always ready to oblige and behelpful readily agrees, slews thecrane around and over goes thecrane just as he recalls that the

crane to slew over that area if theoutriggers are not extended.However the majority of equipmenthas no such system in place. Simplepre-settable zone warning devicesor limiters have though been aroundfor decades, but are often not used.None of us likes to plan for a ‘seniormoment’.

In a recent case where a large lat-tice crane was being moved, theplan had the crane’s outriggers fullyextended and skimming the groundin order to act as stabilisers in thecase of anything caused the craneto waver. However according to anumber of people, claiming to be

eye witnesses, the route encountered anunforeseen width restriction. The team pulledthe outriggers in to pass through the restric-tion but then “forgot” or omitted to put theout again and the inevitable happened. Acamber, minor deviation or even a strong gustof wind caused the crane to ‘wobble’ andover she went.

Years ago rolling outriggers were commonlyused for such moves, allowing full pressure tobe retained under the outrigger jacks - as longas the ground is level of course. Some largeDemag lattice units even had wheels built into the outrigger beams. Such devices seem tohave gone out of use, possibly as many werehomemade and may well have inflicted structural side loadings onto outrigger beamsfor which they were not designed? Howeverwith an apparent growing need to moverigged cranes, perhaps they ought to belooked at again?

residential sites before any above groundwork commences. Because of the substantialhome market it is no surprise that the timbermat industry is dominated by Dutch-basedcompanies, increasingly sourcing their timbers from sustainable plantations in Southor Central America. While large timbers -which also make excellent outrigger mats -may look like a basic commodity-type product, nothing could be further from thetruth. The specialists in this market actuallyadd a considerable amount of value in timberselection, machining and combining differentwoods into mats to provide specific performance criteria and improve durability.For further information, check out previousfeatures in the soon to be established library

October 2011 cranes & access 47

Leave the outriggers on one side retracted

and you had better be sure not to forget - especially if there is a

last minute change of plan

Demag built small wheels into the outriggersof some of its models, including this TC4000

An outrigger bogiefrom the 1960s?

section of our web site www.Vertikal.net.

Why timber and not alloy roll-type mats orheavy duty temporary roadways? Price andavailability is probably a factor along withload bearing capacity. Purpose designedheavy-duty timber mats also provide anexcellent surface for all types of crawlertracks and are very ‘forgiving’ taking theabuse from heavily laden crawler crane undercarriages. The main suppliers hold huge inventories of mats and individual timbers, ready for immediate supply withmany offering a rental service for use on specific jobs.

This should not happen to a good qualityengineered mat, although in this case it does look like extreme abuse - moving a big crawler over too big a step up

Timber mat suppliers usuallykeep large inventories ready

for immediate delivery

Crawlers don’t floatToo many people think that a wide trackedcrawler crane can cope with almost anyground conditions. Such assumptions tend tobe found among operators of small to medium-sized cranes which require far lessplanning and preparation compared to largecrawlers. In countries where soft ground conditions are the ‘norm’ such as theNetherlands, timber mats are almost automatically used under every crane, evenrelatively small crawlers. This is particularlytrue with foundation work - a major consideration for most commercial and some

October 2011 cranes & access 49

One sector where large cranes havebeen involved in a number of accidents and near misses over thepast couple of years is wind energy.Most wind farms include multipleturbines in close proximity to eachother, so there is a natural desire totravel large cranes without havingto strip and re-rig them. The productivity gains are naturally hugeand given that the majority of accidents occur while rigging andstripping out, limiting the re-riggingfrequency can bring safety as wellas productivity gains.

However by their very nature, windfarm sites tend to be in remoteareas with uncertain and often softground. Tracks laid between turbines tend to be narrow and notalways capable of handling theloadings big cranes can inflict. In aperfect world the route between turbines would be adequately constructed or if not, paved withtimber mats, just as a crane company might do when using abig fully rigged crawler on the public highway. Unfortunately thedistances are usually great and timeis precious, so this rarely, if ever,happens. The major crane manufacturers offer narrow trackmodels with outriggers for extrastability and do all they can toensure safe travel with the fullboom, counterweight and jibsrequired for the job.

In the past two years two largecranes of this type have gone over,thankfully without serious injuries.One appears to have been due tosoft ground, the other due to goingtoo close to the edge of the windfarm track.

Manufacturers have gone to greatlengths to improve handling on softground and to distribute the totalcrane weight equally over thetracks. Liebherr for example recently introduced an extension toits LR600 superstructure in order toallow a reduced counterweightwhen rigged with boom and jib configuration for 100 metre high,3MW turbine installations. Forheavier work Manitowoc introduceda unique variable counterweightsystem on its 31000 that constantlyadjusts itself to distribute weightover the crane’s four individual trackunits. Expect to see this appear onsmaller models in the years ahead.Where fully rigged crawler cranestend to come ‘unstuck’ is the turns.Even if a track surface can copewith the ground bearing pressuresapplied by a fully rigged crane, the‘spragging’ or churning effect cancause the front of the tracks to digin and start a chain reaction thatultimately can cause it to overturn.Terex installs four motor drive systems on some of its largercranes to help keep turns smooth,while Liebherr takes it a step furtherand fits twin slew rings to its narrow crawlers, allowing thetracks to be lifted clear of theground and rotated to face thedirection of travel.

The key when travelling with suchcranes is to keep the outriggers outand close to the ground with matsat the ready, then if the tracks dostart to sink into the ground theoperator can use them to gain additional stability and prevent anoverturn. Other wind farm liftingcontractors are now preferring to

This crane went over when the road collapsed while travelling fully rigged.

c&a outriggers

Moving fully rigged cranes is attractive in terms of productivity, but precautions need to be taken. These outriggers and strapped on mats savedthe day when one track began to sink

use large telescopic wheeled cranesthat can be relatively easily strippedand then gain the lost time in theirfaster travel speeds between turbine sites. The Grove GTK 1100 isone specialised example of this.Another is of course the LiebherrLTM1200-9.1, a highly popular unitfor wind farm work.

While timber mats lend themselvesfor platforms for big crawlers and aslarger outrigger mats for big

mobiles, there has been a recenttrend towards larger engineeredsteel mats. While more expensiveand less readily available than theirtimber equivalents, they are particularly suited to certain applications such as the narrowtrack crawlers when keeping theiroutriggers lowered and close to theground. In this instance it is possible to strap or rather tie steelmats to the crane’s outrigger pads.

50 cranes & access October 2011

Handling big matsLarge steel and timber mats areheavy and need to be loaded, transported, unloaded and placed mechanically. Because of theweight there is absolutely nochance of any kind of manual handling or depending on a siteforklift. A crane can of course dothis itself as long as the ground isnot too soft. A large truck mountedlift on the other hand is less suitedto such handling. While most suppliers such as Palfinger andBronto will and do provide liftinghooks or hoists on their machinesfor handling mats, they are notalways the most convenient to useand if the application involves frequent moves such devices arenot always the most efficient.

Dutch access rental company Debruhas devised a solution which itclaims has greatly improved its productivity on such work. It has

designed a trailer which can betowed behind its 70 metreWumag/Palfinger truck mounted liftand carry the large steel mats thatit had made for the soft ground typically found on Dutch windfarms. The trailer has its own built-in loader crane for lifting and positioning the 2.4 metre long mats.It is also self-propelled with its ownsmall power unit to both operatethe crane and propel the trailerunder its own steam. Debru saysthat the trailer has enough sparecapacity to carry a small car or 4x4allowing the operator to leave thetruck mounted lift on site and drivehome at the end of the day. There is some debate as to whetherthe trailer is allowable in allEuropean countries due to the various road regulations howeverDebru says it would be happy to co-operate with anyone interestedin the concept.

This trailer from Debru is fully self-contained and self-propelled.

The unit can be towed behind its 70 metre truck mounted lift

outr iggers c&a Some good examples

An extensive steel mat set up for a big crane in a dockside application.

A good combination of steel and timber.

A good example of a steel mat with sand to provide a good base.

51October 2011 cranes & access

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52 cranes & access October 2011