Ihab Saad – Cranes and lifting equipment
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AI: Transcript ©
I
welcome to another lecture in construction equipment, and today
we're going to be talking about lifting and loading equipment.
Primarily we're going to be talking about cranes. We're going
to discuss what are different types of cranes and how to
calculate their loads and their cycle times and so on and so
forth.
So
we're going to start with a review of some of the issues, the safety
issues related to cranes, because, again, these are
heavy equipment used for heavy lifting, and therefore we have to
be very cautious while using them. So I'm going to show a few video
clips of some crane disasters, crane accidents, and we're going
to pick up the discussion forward following that
here. As you can see, we have a crane lifting a huge truss for the
roof of a structure, and then suddenly, as you're gonna see,
something with the balance of the truss,
causes a problem. And as you can see, the crane is tilting,
collapsing and falling down that can cost
1000s, if not hundreds of 1000s of dollars when it comes to the price
of the crane itself, the cost of the crane and the cost of the seed
structure it was carrying, in addition to any damages to the
structure itself, to the building itself, and, of course, any
injuries or, God forbid, fatalities.
Here again, it shows a crane lifting that load that was not
properly secured. And as we're gonna see, that load includes some
heavy equipment, probably for HVAC, and it's being lifted
gradually, but as you can see, suddenly, it collapses and falls
on a car. Thank God that there was no one in that car, but as you can
see, the person was standing very close to that car, which could
have caused some severe injuries and maybe even fatalities.
And here's the third one, again, a crane lifting a heavy truck.
And as you can see, the truck is lifted from four corners.
Actually, that's another crane. That's another telescopic Crane
being lifted.
And there's a tagline, as you can see at the bottom, held by that
person, trying to guide that load to where it should be.
So far it's going well.
And then you can see the tilting of the load and collapse again,
that can result in severe damages.
And finally, here we have a tower crane, and the tower crane was
erected to build a certain structure, and then there was a
storm. Let's
see if we're going to be able to play that clip.
Let me go back
try to play the clip. As
you can see, there seems to be a storm or something, and that crane
has not been secured properly, so it keeps rotating freely, and it
can hit something, and it can cause some severe damage.
Some of you may have seen some pictures of
crane dangling from a high rise building recently, following a
recent storm. So again,
as you can see, the wind causes that crane to rotate freely. So
now we're going to start talking a little bit about the types of
cranes that we're going to talk about specific types of lifting
and loading equipment. Include forklifts, man lifts, which again,
are used to lift personnel to perform either maintenance or
repair or installations, material handlers, lift trucks, mobile
cranes and tower cranes. All of these are different types of
lifting and loading equipment.
The crane is the primary machine used for vertical movement of
construction material. So here in these pictures, we have different
pictures of different types of cranes. Here we have a telescoping
boom truck mounted crane where this is the telescopic boom, and
it's mounted on a truck. As you can see, it can carry a heavy
load, because this this number of Acts.
Animals and all terrain crane. Again, it has a higher ground
clearance, allowing it to work on rugged surfaces. And again,
another rough terrain crane, pretty much similar to the All
Terrain
and these are the cranes for heavy lifting, very heavy lifting,
lifting equipment or lifting other
materials, a crawler crane and a lattice boom truck mounted crane
similar to the crawler crane, but on a truck mounted
for easier motion and moving on roads and so on and so forth. And
this is another view of the crawler crane with the lattice
boom. Basically, it's sort of a truss to reduce the weight of the
boom itself and allow it to carry heavier weight. And
that's another view here of the double lattice boom crane. The
load is going to be mounted on this side, and we have
counterweights to counterbalance the load and prevent the crane
from overtipping.
So crawler cranes, the full revolving superstructure of this
type of unit is mounted on a pair of parallel crawler tracks. So
here are the tracks, and on top of these, we're going to have the
full revolving apparatus. That's basically the crane itself. The
crawlers provide the crane with good travel capability around the
job site. So again, if you have a rough terrain on the job site,
muddy terrain or whatever, then you're going to be able to move
with this crawler crane. It's not designed for travel on highways,
because, of course, the tracks are going to damage the pavement.
So again, here's the lattice boom crawler crane rig to the jib
extension. This is the jib extension to extend the reach of
the boom.
And here's another jib extension, as you can see, this is the main
boom, and that's the extension,
as you can see, it has a very far reach. It can reach higher
elevations.
And here's the rubber track, telescoping boom crawler crane on
an urban project. Now, this can work on on regular streets and
highways because of the rubber tracks that are not going to
damage the pavement, so it has the benefit of tracks to allow for
better traction, and at the same time, it's rubber tracks so it can
move on regular roads and highways.
And this is, of course, a telescoping boom that can be
extended hydraulically to reach farther distances.
And here's an extendable counterweight to increase the
lifting capacity. The counterweight is here at the back
of the crane, and the farther it can extend hydraulically, it
offers better balance for the crane to counterbalance the load
at the end of the boom on this side
for the crawler crane, some of the common dimensions, the maximum
boom length can be anywhere between 100 to 400 feet. So it can
be really tall. The maximum fly jib length, which is the
extension, can be anywhere between 30 to 120 feet. The maximum radius
for operation of the boom is anywhere between 80 and 300 feet,
and the minimum radius is going to be 10 to 15 feet. So it can lift a
very heavy load in that very limited minimum radius,
some of the common capacities, the maximum lifting capacity at
minimum radius can be 30 to 600 tons. So 600 tons, that's a really
heavy load, and really heavy crane. The maximum travel speed,
since this is a crawler, is going to be relatively slow. It's 5200
feet per minute, which is point six to 1.2 miles per hour.
The ground bearing pressure seven to 20 psi. So it has a relatively
low ground bearing pressure because of the load being
distributed along the tracks, which creates a larger contact
surface with the ground.
Psi, of course, is pounds per square inch.
So here we have a table for the cranes that shows what's the boom
length and at the different operating radii, what would be the
maximum allowable load. So as you can see here, for example, if
you're operating only at 10 feet radius
for a 4040 foot boom length, you can carry a load of 80,000
pounds. That's 40 tons.
But if you extend that radius to 40 feet, as you can see, the load
drops considerably to only about five and a half tons or so. So
from 40 tons to about five and a half tons based on the radius, of
course, the longer the boom,
as you can see here, for example, with the 140 foot.
A boom. It operates at a radius of 30 feet. It can lift 15,500
pounds, and at 100 feet, that's a far reach, it can have only 11 130
pounds. So
let's look at an example. Here, a contractor will use an American
590, 9c crawler crane. C for crawler crane to support steel
construction of an industrial plant, the longest operating
radius will be 50 feet, and the highest required reach is 65 feet.
That's the vertical reach. The bottom of the boom is mounted on
the crane structure five feet above the ground, and the hook and
slings weigh 1000 pounds. What is the length of the boom to be
mounted on this crane, and what is the maximum load the crane can
lift safely at an operating radius of 50 feet. So it's just a very
simple geometry and trigonometry problem we have to draw this
problem. So we have here a radius of 50 feet,
and here we have the height. The Reach is equal to only 60 feet,
not 65 because, again, the boom itself is five feet above the
ground. Therefore if the reach, the total reach is 65 then the
actual height is going to be 60 feet. So using the Pythagorean
Theorem, we get that this hypotenuse is equal to 78 feet. So
we're going to use a boom that's 80 feet because we have a boom of
50 or 80 and so on. So from the tables, this table, for example,
we're going to use an 80 foot boom and we have a 50 foot radius, so
the load can be up to 8080 pounds. But we have hook and slings that
are equal to 1000 pounds, which has to be deducted from the total
load. Therefore, the maximum safe load is going to be the 8080,
which is what the table gives, minus the sling and so on, at the
hook and sling, which is 1000 pounds, and that gives 7080 pounds
at the ad at the tip of that boom. As
you can see, the problem is very simple.
Now talking about telescoping boom, truck mounted cranes.
As you can see here, it's mounted on a truck, and the truck has out
triggers. These are the out triggers that can extend to the
sides to give better balance and stability to the truck, increase
the width of the base of the truck, therefore improving the
balance. And in this case, what's going to happen is that once these
hydraulic arms are lowered down, they are lower to an extent where
the tires of that truck are not touching the ground anymore, so
the full load is supported by the outriggers.
And here's the telescoping boom. These are truck cranes that have a
self contained telescoping boom,
the out trigger or on large steel mat to prevent damage to pavement.
So here you can have the white steel mat, or light something like
this, the out triggers. Out trigger on layered steel mats.
Note the dangerous ground deformation again. Here, for
example, you're going to notice that the pressure of the
outriggers on the mat is going to create some ground deformation
because the ground is relatively soft. So you could, you should
increase the width of that mat to avoid the high pressure on the
soil that can cause deformation and instability of the whole
crane.
Here. The crane is raised on the out triggers. And here it has an
extension, extension jib. It could be hydraulic. It could be
telescopic with an extension jib as well.
Common dimensions, the maximum boom length, 70 to 170, feet,
maximum fly jib length, 3200 feet. Maximum radius for the womb, only
six 260 240 feet, and the minimum radius 10 feet for most models.
Now let's look at the capacity. The common capacity is anywhere
between 20 and 120 tons, at minimum radius, maximum travel
speed, 40 to 70 miles per hour. So here's the compromise, here's the
trade off, that we have relatively lower load to be lifted by that
crane, but higher mobility of the crane, because this can travel on
highways, so you don't want to waste much time in its
transportation. Number of axles between three and four.
And here we have the lattice boom truck mounted crane, very similar
to the hydraulic telescoping boom, but in this case, we have a
lattice boom which is lighter in weight. The lattice boom structure
is light.
Weight. This reduction in boom weight means additional lift
capacity, as the machine predominantly handles hoist load
and less weight of the boom itself,
the common capacity, again, maximum lifting capacity, anywhere
between 50 to 600 tons. So that's heavy lifting here again, maximum
travel speed, 40 to 60 miles per hour, little bit slower than the
other one, the telescoping, but still relatively good speed, 40 to
60 miles per hour. Number of axles anywhere between four to eight to
accommodate the very heavy lifting, up to 600 tons.
The common dimensions, the maximum boom length, up to 470 feet. From
170 to 470
maximum fly jib length 40 to 300
maximum radius for the boom, only 130 to 380 feet. As you can see,
this is much larger than the telescoping boom, and the minimum
radius anywhere between 10 to 25 feet. So
for rough terrain cranes, again, as you can see, this has a very
high ground clearance. These units are equipped with unusually large
wheels and closely spaced axles to improve maneuverability at the job
site so you can it has relatively low turning radius. They earn the
right to their name by their high ground clearance, as well as the
ability to move on steep slopes. Usually, therefore we drive to
allow for better track. Here we have a telescoping lattice boom,
so it has the benefit of the telescoping boom, and at the same
time, it's a lattice boom for lighter weight,
the common dimensions,
maximum boom length, 80 to 140 feet. Maximum flight, jib length,
20 to 90 feet, relatively small or short. Maximum radius 70 to 120
feet, and minimum radius 10 feet. For most models, the capacity is
also relatively, relatively limited, 20 to 90 tons travel
speed, 15 to 35 miles per hour because of the rough terrain and
number of axles, two for all models,
the All Terrain cranes.
These cranes have an undercarriage capable of long distance highway
travel. It has more than two axles,
yet the carrier has an all axle drive and all wheel steering, crab
steering, large tires and high ground clearance. So again, crab
steering, we talked about that it can move relatively sideways and
all wheel steering, allowing it to turn in a smaller radius. All
Wheel Drive to give better traction and high ground clearance
to be able to move on rough terrains as well.
The Dimensions slightly larger than the rough terrain crane, 100
to 27 270 feet maximum flyg length, 30 to 240, feet. Maximum
radius, 70 to 250,
maximum radius, 100 to two, 300 and it can increase up to 400 feet
for the largest machines, minimum radius, eight to 10 feet.
Common capacities. The maximum lift capacity is 30 to 300 tons,
relatively,
relatively high. Maximum travel speed, 40 to 55 miles per hour,
acceptable, very good speed. Number of axles, two to six and up
to eight or nine, even for very heavy crates.
Now you can you're gonna see these crawler cranes for heavy lifting,
lifting, as you can see here. This is the roof truss, probably for a
stadium, something like that, as we have seen in the in the
accident that we saw at the beginning of this presentation. So
and here we have the counterweights, as you can see,
this is going to be very, very heavy lifting.
Addition counterweight mounted on a wheeled platform to increase
lifting capacity.
It's suitable for building projects. Low Rise structures,
short cycle times. High Rise structures,
it's going to have longer cycle times, high speed, high volume
operations like concrete placement. For site conditions,
you have to select the position and location where you're going to
locate that crane and the vertical reach requirements to avoid
contact with power lines and things like that.
For industrial projects, it's very precise.
It can carry very heavy loads,
working around fixed objects, and again, you have to check the site
conditions and the vertical reach requirements
for heavy civil projects. It can be also used for Bri.
Construction, for example, as you can see, it's carrying the beams
for a bridge. Again, it's very precise. Can carry heavy loads,
high speed, high volume operations, multiple work
locations based on its ground clearance and its flexibility. And
you have to check the site conditions and the vertical reach
requirements as well.
I now that we're done with the red with the ground moving cranes,
we're gonna start looking at tower cranes. And tower cranes, as you
can see, have different shapes, different forms. One is called the
*, or flat top tower crane, like this one.
The other one is the hammer line, which has the cables extending on
top of the crane itself.
This is the horizontal jib. This is the luffing boom. And
here we're going to have the counterweights. And this is the
articulated jib,
which can have a further reach horizontally.
Here are some of the main components of that tower crane.
Here we have the counterweight jib with the counterweights at the
end. And here's the main jib where the load is going to be located on
the trolley here at the other end, here's the slewing ring, which is
going to allow the crane to rotate. Here's the cap where the
crane operator or driver is going to be seated, and that's the tower
or mast of the crane, which can change in height to accommodate
different
construction operations.
Again, here's a view of that clean of that crane, the counterweight
and the counterweight
jib, the main jib and the mast.
Here you can see that this is self elevating crane that can extend
its height depending on the job conditions. So
this one is moving along rails. You can have it fixed in place or
moving along rails, depending on the job requirements.
The cab here we have the cab located at the bottom of the
crane, and then it can climb that mast climbing, rotating operator
cab for higher tower crane
hoisting. Now we're going to look at the different motions of that
tower crane. The first one is hoisting, which is the vertical
lifting. So hoisting is the vertical movement of the load.
The hoist cable runs from the hoist drum located on the crane's
counter jib here, at the end, through the jib, and then the
trolley, which is the moving part on the jib, and down to the hook,
which is going to be where the load is going to be attached to
the crane. And
that's the hoist drum with the cable that's going to be allow for
that load to be lifted or lower down the hoist cable runs from the
hoist drum located on the crane's counter jib, and that's close to
the counterweight here in the back.
The second motion is going to be the trolling, which is the
horizontal motion along the boom or the jib, the main jib of the
crane.
So trolling is a horizontal movement of the trolley along the
jib. It allows for the adjustment of the operating radius.
The third motion is slowing, or rotation. Slowing is the
rotational movement of the jib around the towers or the masts
vertical axis
in fixed tower cranes, the slowing ring is located at the top of the
tower here, and the chips lose around the vertical axis of the
tower. In some cases, you might have that slowing ring located at
the bottom of the mast,
as we have in this picture. So another option is for the slowing
green to be located at the base of the tower, and both the tower and
the jib slew relative to the base of the crane. So all of this is
gonna rotate.
Tower cranes are relatively flexible. They can have different
mounting configurations, which can vary between fixed base or a
stationary base, either freestanding or braced to the
building structure. Because the taller the crane, the higher the
wind load is going to be on it, and it might cause some
instability. So we're gonna have some anchors that transfer lateral
loads, especially wind loads to the building structure itself. So
that's better bracing of the crane to the building. You might have
more than one of these bracings depending on the height of the
crane. The fixed base does not transfer any load to the building
structure. So here it transfers the load directly to the ground.
And here we.
Have a tower crane based on piles, so it has to be very well
positioned to avoid any lateral motion
climbing. The crane can either lift itself on the building
structure as the work progresses and traveling, it can be either on
rails or on wheels. On Wheels are relatively rare because issue of
issues of stability, but rails are more common
for the climbing cranes. The crane can basically self erect itself,
usually climbs through an opening within the structure. Must ensure
that the structures framing has sufficient load carrying capacity
to support
the added stresses of the combined weight of the crane and the lifted
loads. So this is within a core of the building itself, or something
like that.
We're going to see a short video clip of a model of these cranes
being erected.
Here we have how the crane lift itself, how it adds additional
joints, and then it slides up to insert this joint, and then one
it's once this is done, it moves up. And now the crane is much
taller than what it used to be
so let's look at these different video clips that are going to
explain how The crane can self erect and increase its height. You
This is something like a time lapse that shows now we are adding
a joint to the crane is going to slide sideways here, and then the
crane is going to be
mounted to increase its height.
As I said, this is a time lapse, so that takes several hours to
perform.
You can see here the hydraulic action lifting the crane and
now they inserted the new joint,
and now the old crane is going to climb up.
Here's another joint being prepared to be inserted as well.
The
crane is going to climb up and
the joint is going to be inserted and so on. I'm looking
at this thing
now. Let's look at another,
another one, another clip.
This shows a model of that crane. It's not a real one, but just the
model again, looking at how the extension is going to happen,
different components. Here's the cabin now. It shows that
all terrain crane erecting the tower crane itself. So it's first
erecting the base that's on a pad to allow for better stability,
a concrete pad and
that's a telescoping boom
altering cream.
And now it's going to assemble the jib on the ground. And
and now it's going to start assembling the mast of the cream
and
this is the platform that's going to be used for counterweights, and
it's going to add more of these, usually concrete slabs or concrete
blocks for the counterweights.
Of course, the heavier the lifting, the more these weights
are going to be.
And now it's going to start attaching links.
To the mast.
And this is the platform that's going to allow for the extensions.
It's open from one side and
and hydraulically controlled, as you can see.
So now it's going to start adding links and inserting them one by
one to increase the height of the crane and
and yet it's climbing. I
that's the counter jib,
which has the counter weights here in the back.
And you can add additional counterweights,
and now the main jib,
and you connect them, and
as you can see, there's going to be some relaxation, some tension
in this articulation, additional counterweights.
Now we're going to increase the length of that crane.
Oh, first of all, the the cab for The driver or the operator.
Someone once described to me, the best way to visualize this is like
a monkey climbing a tree. So first it reaches with its arms and then
secures the arms, and then the legs move up once the legs are
secured, then reaches with the arms again. So that's exactly
what's happening here. I
now I was going to pick a link and insert it to increase the height.
It's open on one side, as you can see, I'm
lower it, secure it in place
and climb and
so that's how the height of the crane is going to increase. You
can have some bracing to the structure itself. As you can see
here, this is bracing to the structure to add lateral
stability, and then it keeps going up. You might have another brace
of the structure as well, depending on the height, total
height of the building,
and there you are.
And basically it at the end of the work, it disassembly, assembles
itself exactly in the same way as it did, at least for the main
mast, and then you're going to use that
telescoping, altering crane to
to
to remove the main jib and the counter jib and so on.
Let's see if we have a
I guess that was the the second clip
climbing cranes. Here, we can see that the climbing crane is inside
the building itself. So you have an opening in the slab where the
crane is going to be elevating itself internal tower crane
climbing through openings left in the ceiling of the structure. And
you have here temporary shores to carry the extra load resulting
from the load itself.
So.
Here's some here are some hook attachments. So you can have
either digging tools like a clamshell or an orange peel
bucket. You can have hooks, different types of hooks for
different types of loads, slings and so on. You can have grabs,
tongs or grabs, or clamps or magnets. That's usually in
shipyards and car used car yards and so on. Grapples, you can also
have skips or concrete buckets. You can use the crane to pour
concrete to place concrete. You can have weights like a cracker or
a demo demolishing ball, a pile driver, bottom dump platform, or
load platform for brakes and blocks and things like that. So
these, all of these are different hook attachments that can be
hooked at the tip of the chip. The
most important factors to be considered when selecting a tower
crane are the operating radius, because once you install that
tower crane, especially if it's going to be fixed in place, it's
going to cost you a lot of money to install it, so you don't want
to move it every now and then. So you're going to design your site
layout where the crane has the maximum reach and it covers most,
at least, most of the area that you need to be covered. In
addition to that, the lifting capacity, of course, the farther
you go on the gym or on the boom, the lower the load is going to be.
So at the tip of the boom, the load is going to be considerably
smaller than closer to the mast. And the lifting speed, especially
controlling the cycle time, especially when you're placing
concrete and so on and so forth.
The weight of the hook block is usually considered as part of the
crane's dead weight. So as we have seen with the other crane, when we
had the weight of the hook and the sling and so on, We deducted that
from the lifting capacity. Same thing here. The rigging system is
taken as part of the lifted load, always check the manufacturers
load chart notes and the American Society of Mechanical Engineers
standard states that under static conditions, load ratings shall not
exceed 67%
of the calculated tipping load, because you're going to have some
wind loads, some some motion of the load itself, which is going to
create a dynamic load on the boom of the crane, which is going to
lessen the total maximum allowed load at the end of the boom.
For dynamic loads. Load charts are based on the static loading
condition for tipping. When the load is moved from a condition of
rest or is stopped, dynamic loading will occur, and this is
one of the reasons why only 67% of the static load is taken as the
capacity. So you're not gonna load the crane to its maximum capacity.
You're gonna take only two thirds of that maximum capacity
wind loads. Again, as we have seen in one of the the catastrophic
collapses of cranes. Tower cranes are wind sensitive machines.
Because of their high contact surface area, operations should be
discontinued when wind velocities exceed the manufacturers maximum
permissible in service wind velocity, which is usually in the
30 to 40 miles per hour range. So if you have strong gusts of wind,
you may suspend operations until that gust is over, and then resume
work later on. If there's going to be a storm, then the crane must be
locked and secured so that the boom does not rotate, as we have
seen in the previous video clip.
Again, the American Society of Mechanical Engineer standards
require that for structural competence, dynamic effects
associated with hoisting and slowing and wind at maximum
service velocity be considered so there's no safety factor
requirement, as with the tipping conditions. In this case, it's
again left to the consideration and the expertise and the
experience of the operator and the project manager who should stop
the operation if there's any danger to people or to property,
because of how tower craze are loaded, are load rated and from
experience, it's recommended that a 5% work margin be maintained on
every tower crane lift. So if the weight of the load is 15,000
pounds, the weight of rigging is 400 pounds, so the total weight is
15,400
we're gonna allow an extra 5% working margin, which is a factor
of safety of 1.05
therefore the required capacity for the crane which can be
obtained from the table is 16,170
pounds.
And here is a sample of the tau crane loading tables. Again, it
shows for different boom lengths or lengths of the jib and.