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
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
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
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
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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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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40 cranes & access November/December 2009