Outriggers and mats - VERTIKAL

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Outriggers and mats - VERTIKAL Powered By Docstoc
					Stopping                                                                                                  c&a                                          mats

that sinking feeling
It is a truth, universally acknowledged
that a mobile crane or aerial lift in
possession of outriggers must be
in want of a good set of outrigger
mats. Unfortunately, too many
owners and operators appear to be
ignorant to this fact evidenced by
the large number of machine topples
caused by outriggers sinking or
collapsing into the ground due to
the poor set-up.
What is curious is that the vast         Then there are those who think they     for big mobile cranes, thanks to the        underground voids. Is the ground
majority of people understand the        can get by without a set of decent      fact that they are relatively compact       built up, reclaimed, or close to a
principal that if they try and walk      mats, making do with random             and versatile, not to mention their         slope which may give way?
in deep snow they will sink to           off-cuts or other substitutes -         ability to pick and carry. When it          Are there any poorly backfilled
their waist, unless they are             sometimes waiting to see what           comes to any crawler crane over             excavations?
equipped with snow shoes, skis           they can find on site, should some      500 tonnes capacity - and often
                                                                                                                                           Who needs outrigger mats?
or some other method to spread           cribbing be required. This in spite     smaller - most contractors or crane
their weight.                            of the fact that the cost of a set of   suppliers, will insist on building a
Yet this almost instinctive              quality mats - which will last a        platform or mat for the crane to
knowledge does not appear to             lifetime - is a fraction of the         operate from as a matter of routine.
transfer to many supposedly              purchase cost of the machine they       Either to spread the track loads over
well-trained' crane and lift operators   help support. Thankfully safety         a wider area or to prevent ground
or users who continue to work            authorities, such as the UK's HSE       damage, particularly when working
without putting outrigger mats           are beginning to clamp down on          on public roads or close to the
under each jack to spread the            makeshift cribbing, shutting down       water table etc.
                                                                                                                             Aggregates or wood?
  No matter how good your mats, running
                                                                                 The smaller the crane the more              Civil engineers will sometimes insist
  off the edge will cause problems                                               likely the contractor and crane             on the building of a properly
                                                                                 supplier are likely to operate it           engineered and calculated platform
                                                                                 without any such platform. After all,       using a number of layers of well
                                                                                 smaller crawler cranes are typically        compacted aggregates on top of
                                                                                 selected for their low ground               geogrid matting or even a concrete
                                                                                 bearing pressures. The result is            pad. While this may well be the
                                                                                 that ground conditions can often            right way to go for the very largest
                                                                                 be overlooked with smaller crawler          projects where a crane or cranes
                                                                                 cranes and lifts.                           will be working over a long period,
                                                                                 However while tracked cranes and            it can be both time consuming and
                                                                                 lifts are better at crossing soft           expensive for shorter term work and
                                                                                 ground and do generally have                requires a good deal of experience
                                                                                 considerably lower ground bearing           to get it right. A faster and far more
machines weight over a wider             jobs where it is spotted.               pressures than wheeled equipment,           cost effective - not to mention
surface area.                            In this, our fourth annual feature on   they can and do tip over when the           environmentally friendly - platform
Too many operators choose to             outrigger mats and roadways,            ground gives way. So it is vital to         can be constructed from timber,
gamble on the nature of the ground       we are focusing more on large           know as much as possible about              or for smaller equipment aluminium
beneath them. If they have pads on       mats used for working platforms         the make up of the ground with              or even composite mats that
board and they are not used, it is       for crawler cranes, large truck         particular attention to any possible        bolt together.
clearly out of sheer laziness or         mounted lifts and mobile cranes
possibly ignorance - after all there     or as temporary access roads.           This one looks like it found a void. It also looks expensive
is nothing to be gained by winning       We also take a look at how poor
this 'throw of the dice' - and           outrigger set up is the root cause
everything to loose. If they have        of so many accidents.
rented the machine without thought       On a firm footing
to the ground conditions and the         Crawler cranes run the gamut from
rental company has not asked them        the smallest 900kg spider crane to
about it, the chances are that they      some of the largest cranes in the
will not have any mats even if they      world. At the top end tracks have
had a notion to use them.                become the undercarriage of choice

                                                                                               November/December 2009 cranes                    &   access   35
mats                                        c&a
Timber mats (from sustainable            big crane travels, avoiding the need
sources of course) can be purchased      to cover the whole route or area.
or even rented in many areas, from       When it comes to the largest lifts,
a number of specialist suppliers.        especially when a heavy load has to
The benefits are that even a large,      be lifted and carried, a combination
sophisticated mat can be constructed     of aggregates topped by timber is         Aggregate platforms need to be carefully
at short notice and then, if necessary                                             calculated and built or they can easily give way
                                         often used. The aggregate base
moved or adjusted as the project         can be used to both provide a
develops. Timber is still relatively     foundation and help level the route,                                                     ...and then over she goes! While no
                                                                                                                                  one was hurt, the cost and disruption
inexpensive and properly                 while the timber then spreads the                                                        is immense
engineered hardwood timbers with         loads and better handles the wear.
edge protection and lift handles or      Mats, platforms or pads are most
eyes are incredibly versatile and        often considered where the ground
can be adapted to all manner of          is soft and where the ground will        Just over an hour later the
challenges. They can also be             clearly give way under any significant   crane begins to sink further...
moved from back to front while a         pressure. However other considerations
                                                                                                                                           These two Terex CC2800-1
                                                                                                                                           These two Terex CC2800-1
                                                                                                                                        are carrying out a tandem lift
                                                                                                                                        are carrying out a tandem lift
  Crawler mount equipment can induce overconfidence-                                                                                     in Krefeld, Germany from an
                                                                                                                                          in Krefeld, Germany from an
  The person renting this machine would have faced a                                                                                          excellent aggregate and
                                                                                                                                              excellent aggregate and
  large recovery charge                                                                                                                                timber platform
                                                                                                                                                       timber platform

                                                                                  include a surface that will wear            platforms can protect against this
                                                                                  badly and seriously erode with              issue as can some composite mats.
                                                                                  heavy traffic leading to problems           Aluminium and composite mats,
                                                                                  later on. Both timber and aggregate         panels or temporary roadways are

   36 cranes & access November/December 2009
                                                                                                          c&a                                              mats

 A solid wood mat for one
 of the world's largest mobile cranes, the Terex Demag CC 8800

                                                                                                                           This mat both spreads the load, protects the
better suited for gaining access          achieved to some extent with a                                                   wet surface from erosion and reduces wear
across soft ground, a challenge           regular crane by adjusting the                                                                 and tear on the crane's tracks
often faced with utility work such        boom angle to balance out the
as erecting or maintaining remote         counterweight. This is not always
pylons. The growth of wind power          practical though and so                 composite temporary roadways
is also creating business for the         understanding the ground and            and even modular car parks.
providers of temporary roadways,          taking the appropriate steps            TPA, part of the Vp group, tends to
particularly for smaller wind farms       becomes even more critical.             specialise in temporary roadways
or even individual turbines where         The narrow tracked Liebherr             and ground cover but is also
the cost of constructing a                LR1400/2-W - designed for wind          equipped to design custom pads
permanent road is not justified.          farm work, avoids the turning           for cranes and lifts.
There are exceptions of course.           problems, by installing a set of        Finally the most recent entrant
In the Netherlands and parts of           jacks to raise the crane up off its     into the UK, Welex, is also Dutch
northern Germany much of the              tracks, while a second slew ring        owned. Celebrating its 40th                 Aluminium road ways from companies
ground is reclaimed or close to the       allows the undercarriage to be          anniversary it has recently                 such as TPA, Eve and Timbermat are well
                                          rotated to the new direction of                                                     suited for wheeled cranes and lifts to gain
water table and is just too soft.                                                 established new operations in both          access over soft ground.
As a result the use of large timber       travel without disturbing the ground.   the UK and Germany and can offer
mats is the norm. It is for this                                                                                              the ground conditions or pad size, in
                                          Who supplies?                           a wide range of its Ekki hardwood
reason that so many Dutch                                                         mats for both sale and rental.              order to create a positive habit.
                                          The better suppliers of timber mats,
companies are strong in this market.                                                                                          Some equipment, particularly loader
                                          will not only supply standard sizes     Go for quality                              cranes and small truck mounted lifts
Most experienced crawler crane            from stock, but will also help with     All of the timber specialists warn          are often equipped with small or
 In this case a                                                                   against buying some of the cheaper          even no pads at all, with the outrigger
 1,350 tonne fully                                                                timber that is currently coming on          jack 'foot' being hardly larger than
 rigged crane                                                                     the market stressing that it will
 tipped, it looks                                                                                                             the diameter of the cylinder rod. In
 as though                                                                        almost certainly prove to be a false        spite of this many loader crane
 it was                                                                           economy. This is particularly true          operators do not seem overly bothered
 front heavy,                                                                     in northern Europe, where timbers
 while a few steel                                                                                                            to use mats. It is true that most of
 mats have been                                                                   that split and damage easily, are           the time they do operate on good
 used haphazardly                                                                 then prone to freeze/thaw damage
 to no effect                                                                                                                 solid ground and that, unlike mobile
                                                                                  through the winter further                  cranes, they are not usually
                                                                                  undermining their integrity.                required to lift the truck clear of the
                                                                                  Coping with outriggers                      ground. However, too many operators

                                                                                     Ty p i c a l t i m b e r s i z e s f o r m a t s
                                                                                     Light to medium duty -                               70mm x 1m           x 3m
                                                                                     Medium duty -                                        70mm x 1m           x 5m
operators fully understand the            the mat design and calculations            Medium/heavy duty -                                 100mm x 1m           x 5m
dangers of moving a fully rigged          and modify or adapt the timbers            Medium/Heavy duty -                               200mm x 1m x           5/6m
crawler crane particularly on             for specific challenges.
                                                                                     Medium/Heavy duty -                                 225mm x 1m           x 6m
unstable ground and particularly          In the UK, Dutch owned Sarum
when the crane has to turn.                                                          Heavy duty -                                        250mm x 1m           x 6m
                                          Hardwood - Mat and Timber                  Heavy duty -                                      300mm x 1.2m           x 6m
In spite of this a surprising number      services, has been operating for
of crawler cranes do tip over every       many years and has enormous             We have campaigned for several              appear to give no consideration at
year, purely due to ground                experience in providing both mats       years now on the importance of              all to the ground conditions, even
conditions. The majority occur            and outriggers pads. It stresses its    using outrigger mats under the              when setting the stabilisers on grass.
when the fully rigged machine is          credentials in sourcing its             outriggers of any piece of equipment.
being moved, when it is either front      hardwoods from sustainable sources      This is clearly more important with
or back heavy, concentrating the          and focuses its efforts on wood.        some machines than others. Some
loads on only part of the track.                                                  cranes or more particularly lifts, are
Manitowoc's new 2,300 tonne               Locally owned Timbermat of
                                          Stockport, Cheshire, considers itself   equipped with very large built-in
Model 31000 automatically adjusts                                                 pads which can cope with all good
its counterweight in order to keep        a full line specialist in temporary
                                          surfaces and while offering the full    to firm ground conditions without            Loader cranes and small truck
the machine's weight - or centre of                                               requiring a separate mat. However
                                          timber mat service, also sells or                                                    mounted lifts often have only a
gravity - balanced over the centre                                                many owners feel that it is good             minimal built in pad
of its four tracks. This can also be      rents a whole range of alloy and
                                                                                  practice to use a mat regardless of
                                                                                               November/December 2009 cranes                       &   access      37
mats                                           c&a                                                                                                      Here is a nice
                                                                                                                                                 combination of steel
                                                                                                                                                  and timber mats for
                                                                                                                                                the Liebherr flagship
New standards will help                     be widely used 'on rubber'                                                                                the 1,200 tonne
The better operators tend to                and mistakes arise such
understand the risks but it is              as slewing with an
surprising how many still fail to           extended boom or load
comprehend the need to spread               without setting the
the load. New European standards            outriggers. In addition
for loader cranes dictate the               many of the cranes are
manufacturer's maximum loadings             owned or bare leased
permitted on each outrigger which           and operated by a
could go a long way to solving this         variety of people, some
issue. Some, particularly the larger        with little knowledge of
models, will still require the use of       the particular crane.
separate mats, so the challenge of          True, this is changing as
how to get operators to use them            more states insist on
will remain.                                certification, but there
                                            are still a lot of 'casual'
The statistics are clear
                                            operators on site. In
Numerous studies of crane and               Europe and Australia
vehicle mounted lift accidents              road going cranes are
clearly show that the majority are          more prevalent, most with limited      conclusion is flawed or not, one         so the real the percentage is
ground or stability related - in other      or no on-rubber duties so outriggers   thing is for sure, those that do not     considerably higher. Looking at the
words tied into the improper use of         tend to be set for most lifts and on   use mats are more likely to tip their    other causes - 25 cases were due
outriggers. Accurately extracting           arrival on site. It is also more       machine whether it is a crane,           to poor management and two of the
this information from official              common to rent the crane with          aerial lift, telehandler or even a       key causes within this category
statistics is notoriously challenging,      an operator who tends to stay          concrete pump.                           were lack of proper site assessment
as the causes are often poorly              with that particular crane and is                                               and insufficient checks and measures
                                                                                   Our conclusion also helps overcome
recorded. 'Crane collapse' is often         therefore a great deal more                                                     to address ground conditions,
                                                                                   the challenge, often thrown up as an
given as a reason, regardless of            familiar with it.                                                               while another cause included the
                                                                                   objection to supplying mats for
whether it was due to a structural                                                                                          incorrect set up of outriggers and
                                            That sinking feeling                   non-operated equipment, that a
failure, (rare), the fact that outriggers                                                                                   the overriding of interlocks.
                                            In more than 90 percent of the         rental company cannot know the
were either not extended or only
                                            accidents we have reported on          ground conditions and cannot             Looking behind the type of accident
partially extended, or from overturning
                                            where cranes have tipped over due      therefore supply the right size of       into the causes, the study
after the outriggers have sunk into
                                            to sinking or collapsing ground, NO    mat. If a mid-sized mat for the          highlighted three key reasons:
soft ground or broken through into
                                                                                                                            a surprisingly high 48 percent of
an underground void.
                                                                                                                            accidents involved a violation of
Having reported on crane and lift                                                                                           rules and regulations;
accidents from around the world                                                                                             26 percent a lack of knowledge and
over the past six years and studied                                                                                         26 percent human error. This also
numerous safety/accident reports                                                                                            reinforces what we have noticed in
and studies we estimate that                                                                                                accidents that have made it into the
around 65 percent of all wheeled                                                                                            press. In many cases where cranes
crane and aerial lift accidents are                                                                                         or lifts have tipped over due to mats
caused by or are related to                                                                                                 not being used, a full set are clearly
outrigger misuse.                                                                                                           visible - stowed on the machine.
The interesting fact though it is                                                                                           The operator was, one assumes
that there is a clear differentiation                                                                                       too lazy to use them or gambling
between such accidents in North                                                                                             that the ground was firm enough
America and those in                                                                                                        not to require them.
Europe/Australia. In North America
                                                                                                        There is no point
a significant number of the                                                                      having cribbing timbers
accidents are still caused by the                                                                     to hand if they are
operator not extending the                                                                            not used correctly
machine's outriggers at all. While
in Europe the outriggers are                                                       given unit is provided and used,
                                            outrigger mats were used at all.
generally used - on many units due                                                 the chances of the machine
                                            While it is a gross and perhaps
to interlocks being fitted - and the                                               sinking are dramatically reduced.
                                            crass oversimplification, it seems
accidents that do occur are more
                                            that as long as an outrigger mat is    A recent study carried out by the
often caused by outriggers sinking
                                            used (at least one larger than the     government of Singapore's
or punching through into an
                                            outrigger pad) a tip is unlikely.      Manpower ministry, looked at 40
underground void.
                                            It could be of course that those who   serious crane accidents that have
Some of this differential can be
                                            routinely use mats are simply more     occurred there over the past few
attributed to a difference in the type
                                            aware of the dangers and therefore     years. It blamed just nine or 22.5
of cranes most commonly used and
                                            take precautions and as a result       percent on “The failure to use
the way they are operated. North
                                            never appear in our online accident    outrigger mats or cribbing”. It
America has a massive population
                                            gallery? Whether our simplistic        should be noted that a number of         A nice set up with pads close to hand -
of Rough Terrain cranes which can
                                                                                   the accidents involved tower cranes      shame they are not being used.

   38 cranes & access November/December 2009
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mats                                        c&a
So what is the solution? If we could     large built-in pads and more
only ensure that proper mats and         emphasis given on the importance
cribbing are always used, we would       of using them. The rule to limit
almost certainly see a significant       maximum ground bearing pressures
fall in the number of accidents that     might also help. And finally more
occur. One suggestion made recently      training on crane and lift set-up and
was that cranes and lifts be fitted      cribbing techniques.
with sensors that detect the             What do you think?
machine beginning to tip or tilt.
                                         In two separate polls on Vertikal.net
While this is a logical use of
                                         we asked 'Should the use of outrigger
technology we would prefer to see
                                         mats on cranes and lifts be
a rule that required all equipment
                                         mandatory' 81 percent of the 966
fitted with outriggers, to be supplied
                                         respondents said Yes.
with a set of mats or appropriately
                                                                                 Then when we asked rental                 which are supplied with operators
                                                                                 companies if they supplied outrigger      do at least go out fully equipped
                                                                                 mats with all of their machines that      with proper mats and cribbing
                                                                                 were fitted with outriggers just 54       materials. It is the nonoperated/
                                                                                 percent or 98 respondents said Yes        self-drive equipment - smaller truck
                                                                                 - so just under half of all rental        mounts, trailer lifts, spider cranes
                                                                                 companies simply do not supply them.      and lifts - that are rented without
                                                                                 Anecdotal evidence suggests that          mats. A large number of loader
                                                                                 the yes vote was higher than the          cranes although 'operated' are also
                                                                                 reality, with the majority of companies   not suitably equipped, although the
                                                                                 not supplying them.                       better fleet managers do equip their
                                                                                                                           units with a full set of good quality
                                                                                 Interestingly almost all cranes and       composite mats.
                                                                                 large truck mounted platforms

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    Design and Fabrication of:
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   Kelston, Bath. BA1 9AN.
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  40 cranes & access November/December 2009

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