Ihab Saad – Excavators
AI: Summary ©
The efficiency of a hydraulic excavator is discussed, using a table to estimate the output and using booms to extend the excavator's reach. The machine uses a crane to hold dirt in the bucket and prevent spillage, while also using a dipper to hold dirt in the bucket and prevent it from getting out of the soil. The speakers discuss proper construction practices, maneuvering, and optimal productivity, as well as factors affecting productivity and cycle times. The cost of construction is estimated and productivity is estimated at around 180,000 cubic yards per hour.
AI: Summary ©
Five, 2.95 it's going to be lumped into larger particles. For wet
clay, it's going to be anywhere between point five and point nine.
Rock well blasted, relatively graded, is going to be point
seven, 2.9
and rock poorly blasted is going to be point four to point seven.
So we're going to use only about half of the capacity of that
bucket.
Here we have an example estimate the hourly production for a loader
with the bucket heaped capacity of five cubic yards. The soil is sand
and the load factor. And the load factor is basically to convert
from loose to bank volume, because that soil filling the scoop or
filling the bucket is going to be in its loose condition. So if we
want to convert it and get the production in bank, cubic yards
per hour, we need to convert to bank volume. That load factor is
point eight. The Cycle Time for the loader is one minute and 30
seconds, which is 90 seconds, and the job efficiency is 80% so let's
see how we're going to solve this. First of all, the bucket load is
going to be equal to the fill factor times the bucket heat
capacity. The fill factor for that type of soil based on this
equation at this table here, we mentioned that it's going to be
sand. So for sand is going to be around point nine to 1.0 we can
choose either one or any range in between an average. So we're going
to take, in this case, point nine times the bucket capacity, which
is five, which means we're going to have soil volume inside the
bucket of 4.5 loose cubic yards. Then we need to convert these
loose cubic yards into bank cubic yards. So we're going to multiply
by the load factor. So that's going to reduce the volume.
Therefore each bucket is going to carry 3.6 bank cubic yards for
each cycle. Number of cycles per hour is going to be one hour,
which is 60 minutes divided by the cycle time. Now the cycle time was
given into minutes and seconds, so we need to make sure that we are
using the same unit, so 60 divided by one and a half, which is going
to give us 40 cycles per hour. That is with the assumption that
we're going to use 60 minutes per hour as production. But this is
not always true. We're going to have to look at the efficiency.
The efficiency was given to us as point eight or 80% therefore the
volume, the total Audi production, is going to be the volume per
cycle, times the number, number of cycles per hour, times the
efficiency. And that gives the total production of 115.2
bank cubic yards per hour.
Again, here's the table that we use to get the factor for the
sand.
The hydraulic excavator, also called hydraulic hoe or hydraulic
excavator backhoe, depending on the way the bucket is facing if
it's facing forward, it's a hoe or a shovel. If it's facing backward,
it's a backhoe. It digs by pulling the dipper back towards the
machine. So there's going to be a hydraulic force
pushing that bucket into the soil and then pulling it to get out of
the soil, with a breakout force to take the soil and to be scooped
away. When the dipper is filled, it's curled up to reduce the
spinach through the hydraulic arm of the equipment,
and that's basically what it looks like. So here's the articulated
hydraulic arm
with pistons, and here's the digger or the bucket or the
dipper, so it has some teeth at the edge to help loosen and break
the soil. And once it's full, it's going to be tilted upwards to
avoid or to reduce the spillage.
It's used for trenching work, as it can also lay pipes, pull trench
shields or sheet piles, and backfill the trench. After the
operation of laying the pipe is complete,
the dipping width of the bucket should match the trench width to
maximize production. So if we're going to use, for example, a
the width of the bucket is three feet, then the the width of the
trench should be around that these buckets are movable. We can
exchange these buckets and change the bucket size depending on the
operation that we're going to be using it for.
Telescoping booms may replace articulated booms. So instead of
the articulation, we may have telescoping booms to extend the
reach of that of that hydraulic excavator,
the generic equation for estimating the excavator
production is going to be pretty much the same thing, by the way,
which is number of cycles per hour times the volume per cycle. But
here we are basically
adding some other factors.
That affect the production rate. So it's equal to c times s times v
times B times e. Let's look at what each one of these means. C is
the number of cycles per hour. S is the swing depth factor. Now
imagine the cycle is going to include digging, swinging,
dumping, swinging again and starting to dig. The wider that
angle of swing, the slower the operation is going to be, because
you have to move farther distance. Therefore, if that angle of swing
is relatively narrow, that's going to expedite the excavation, which
means reducing the cycle time, which means more cycles per hour,
which means more production per hour.
V is the heaped bucket volume. B is the bucket fill factor, which
we have seen depending on the type of soil. And E is the job
efficiency, which is how many productive minutes per hour can
you get out of this piece of equipment?
We have some effect from the job conditions. Depending on the job
conditions, we can have either excellent job conditions, above
average, average, below average and severe. And for different
sizes of buckets, we can have estimated cycle times. So for
example, the excellent conditions are characterized as easy digging.
We're digging through easy soil to break into unpacked Earth, sand,
ditch, cleaning, etc, digging to less than 40% of the machines
maximum digging depth. So the arm is not going to be extended to the
maximum.
And the swing angle is less than 30 degrees. Again, the amount of
swing is relatively limited. You dump into a spoil pile, so you
don't have to maneuver and to adjust to dump into a truck, no
obstructions. You can see the dumping area. You can see the
digging area. So that's going to be excellent conditions for a less
than a one cubic yard bucket, the cycle time is going to be about 13
seconds. One to two cubic yard buckets going to be about 15. Two
to three cubic yards, it's going to be 16 and so on. The larger the
bucket, of course, the longer the cycle time.
Above average conditions are characterized as medium digging.
Now it's not as easy as the previous one, but packed Earth,
relatively more consolidated and compacted, dry clay soil was less
than 25% rock content. Now the depth, instead of being 40% is
going to increase to about 50% so more reaching out with the arm and
the swing angles less than 60 degrees. So still here, in the
first case, we have 30 degrees. Now we have about 60 degrees. It's
still large dump target, so it could be a large truck or an open
area and few obstructions, as you can see, that's going to extend
the cycle time by about two seconds, two out of 13. That's
about almost 1/7 so almost 14% reduction
and so on. If we keep going down, we're going to see that the
average conditions, for example, more hard packed soil depth even
more 70% and the angle of swing up to 90 degrees and loading into
trucks, so you have to spot and you have to adjust, you have to
maneuver, which, again, is going to slow down the operation up to
when we reach the severe conditions we have digging through
tough and hard soil
depth over 90% of the maximum digging depth. So we are almost
extended to the maximum and a swing angle of over 120 degrees.
So basically we are moving more than 90 degrees. It's basically
almost facing backward, and it's a small dump target requiring
maximum reach, so you have to maneuver to make sure that you
don't spill that soil out of the dump truck, so it requires
additional maneuvering. Now, comparing between the excellent
job conditions and the severe conditions we find that we have
here, for example, difference of eight seconds, eight out of 13.
That's almost 60% which means that the production is going to be
reduced considerably.
Shovels similar to the backhoe, but in this case, is going to be
facing forward. The bucket is going to be facing forward. Is
going to use two kinds of forces to break down the soil. Is going
to have something called crowding force, which moves downwards and
then break out force, which is gonna lift that soil and dump it
into into the truck. So dig with a combination of crowding or
downforce and breakout or forward forces. It has a limited ability
to dig below the track level, because, again, it's gonna be a
risk of over tipping, tipping forward. So we're gonna try to
have.
With that,
the shovel production, like the backhoe, is going to be exactly
the same, C times s times v times B times E, and the production is
mainly affected by the swing angle and the loss time during the
production cycle, depending on the type of soil and the different job
conditions, as we have seen the previous day, the angle of swing
between digging and dumping should be kept to a minimum to improve
production, as we have seen again, difference between 30 degrees and
120 degrees. So
looking at an example here, for example, other factors to improve
the production having a level floor of cut that's going to help
with the stability, moving frequently to be closer to the
working phase, instead of extending the arm, moving on the
tracks to get closer,
keeping digger teeth sharp, which is going to help with the crowding
force and better training for the operator, a skilled operator can
definitely achieve more than an unskilled operator. So the ideal
production is going to be equal to the bucket, bucket capacity times
the fill factor divided by the ideal cycle time. That's going to
give us the ideal production in again, bank cubic yards per hour.
And here's some again,
fill factors for moist loam or sandy clay, one to 1.1 sand and
gravel point nine, five to 1.1 and so on.
Now, based on the the idea shovel productivity in bank cubic yards
per hour, this is sort of the theoretical production rate as
given in the manual of that piece of equipment for different types
of soils, for different bucket capacities. So for example, for
tough clay and a one and a half cubic yard bucket is going to be
tough clay
and one and a half, that's going to give us 210
bank cubic yards per hour. Again, this is the ideal production, not
the actual production. Therefore, the ideal production can be
obtained in one of two ways, either through a table like this,
or through an equation like this, one with the bucket capacity times
field factor divided by the ideal cycle time.
The angle of swing is going to give us a modifying factor, with
the 1.0 being represented by 90 degrees and 100% of the optimum
depth, we're going to see that in an example in just a minute. If
you dig less than the optimum depth or much more than the
optimal depth, that's going to affect the production. If the
angle of swing increases or decreases again, that's going to
affect the production.
Job conditions. We have both job conditions and management
conditions. Management conditions basically something like having a
good operator, a good observer, a good superintendent, good
monitoring of the operation, you have the the trucks lined up very
close to where the soil is going to be done, so that the shovel
doesn't have to move much. Job conditions, depending on how
graded the site is, if you don't have too many obstacles,
the equipment is in good condition and so on. These are things that
also we can't control. So we have another modifying factor based on
the management conditions and the job conditions. For Good job
conditions, good management conditions, we get, for example, a
factor of 75%
Let's now look at another example. A contractor has a project to
excavate an apartment complex and must construct a three foot
compacted fill to support the parking garage. The borrow site
where we're going to be borrowing the soil is three miles from the
construction site, so there's going to be a shovel over there,
or a backhoe, or whatever piece of equipment, and that's going to
dump into trucks, and the trucks are going to bring that soil to
the site for utilization. The borrow site is three miles from
the construction construction site, and 10 cubic yard. 10 cubic
yard dump trucks
will be used to haul the kneaded fill a two cubic yard shovel would
be used to load the dump trucks. The material is tough, dry clay
with a swell factor of 35%
the height of the cut at the borrow site is 11.6 feet, and the
angle of swing of the shovel is 150 degrees. So estimate the ideal
production using the table and using the equation, we're going to
do that and then estimate the actual production for good job and
management conditions. The optimum digging depth of the shovel is 9.8
feet. This is the optimum, and this is the actual so let's see
this equation. This this row.
Again,
with the optimum depth of cut of various sizes of Jetline buckets.
So here is going to give us four different types of soil. What
would be the optimum depth of cut for a three hot three quarters
cubic yard, for one and a quarter cubic yards and so on. And also
here we have the operating factors, the job conditions and
the management conditions, exactly the same table as we have seen
before. And then we have also the drag line productivity correction
factor based on the percentage of the optimum depth of cut and the
angle of swing, as we have seen with the shovel, and ideal
productivity based on
the bucket size in bank, cubic yards per hour. Let's
look at an example. The contractor has a project to construct a large
parking lot for a shopping center. The contractor decided to use a
crawler drag line. Crawler drag line, which means it's gonna be on
tracks with one and three quarters cubic yard bucket to excavate a
large drainage ditch to collect and remove storm water runoff.
The excavated soil is common earth, and the average depth of
cut is 7.6 feet.
The excavated material will be loaded in dump trucks for removal
from site. The angle of swing is 120 degrees. Job conditions are
good and management conditions are excellent. So it's not good and
good job conditions, good management conditions Excellent.
What is the estimated dragline productivity in bank cubic yards
per hour? And then we're going to add a couple of other layers. If
the volume to be removed is 3200 bank cubic yards and the rental
cost per day for that dragline is $1,800
how long would the operation take, and how much will it cost? So now
we are also looking at durations and cost estimating for that piece
of equipment.
So from the table, the ideal production for one and three
quarters bank cubic cubic yard bucket and Common Earth is 210
bank cubic yards per hour. We're just going to look at the table.
The optimum depth of cut is nine and a half feet. The percent of
the optimum depth of cut is because the actual depth is 7.6 so
it's 7.6 times 100% divided by 9.5 which gives 80% now using the 80%
factor with 120 degrees the angle of swing gives us a modification
factor of point nine for good job and excellent management
conditions, the factor is going to be point seven eight. Therefore
the actual dragline production is going to be the ideal 210
times. The factor due to the swing angle and the depth of cut times
the other factor due to the job and management conditions, which
gives 147.42
bank cubic yards per hour.
The total volume that needs to be excavated is 3200 bank cubic
yards. So dividing that by the production per hour is going to
give us 21.7 hours, which is basically assuming eight hours of
work per day is going to be almost three days. We're not going to pay
for a fraction of a day. So we're going to pay for the third day,
whole day. Therefore the cost of operation is going to be three
days times $1,800 per day, which gives $5,400
that's the cost of that operation.
Another piece of equipment, similar to the drag line, is going
to be the clam shell. So
it's going to be the same machine, but the attachment at the edge of
the boom of the crane is going to be different. In this case, it's
going to be a drag line. It's capable of digging at higher
depths. That's one of the benefits of the clamshell. It lacks
positive digging action and lateral control of the shovel or
the backhoe. Again, positive digging, which means the
articulated hydraulic arm is going to give that hydraulic force, that
crowding force, but in this case, it's going to rely, like the drag
line on its own weight and on gravity.
It's used for excavating vertical shafts and footings for
foundations. So this is what it looks like.
And as you can see, we have here the lines that are used to open
and close that clamshell, which has some teeth, again, to cut
through the soil as possible.
It's also used sometimes for grains and in Marine Operations
and so on.
The production is based on the equation, same generic equation,
volume per cycle, time, cycles per hour, and.
So the maximum load should be limited to 80% of safe lifting
capacity for rubber tired equipment and 90% for crawler
mounted equipment. This is a relative factor of safety, just to
make sure that we're not going to have any over tipping or any
stability issues with the with the equipment.
And again, here we have a table that shows the different cranes
and at the different boom lengths, what's going to be the operating
radius, and what's going to be the total load that it that it can
carry at that the tip of that boom. And this shows basically the
capacity of the clamshell bucket itself, the rated capacity is
equal to VS which is this bottom half plus Ve, the top half, which
is the heaping minus Vm, which is at the joint where it opens and
closes the clamshell.
And here it shows again, the different weights, because we can
have either a general purpose bucket, a heavy duty bucket or a
light duty bucket. Each one of them is going to have a different
weight on its own for the different rated capacities and
different sizes of these buckets.
To improve the clamshell production, we're going to have
the dumping radius the same as the digging radius. So the the boom is
going to rotate and is going to dump at the same distance where
it's digging from keeping the machine level to avoid swinging
uphill or downhill, because again, swinging uphill or downhill is
going to affect stability, and it's going to affect the effective
length of the boom of the crane.
So again, with the larger angle of swing, we're going to have
different correction factors. The lower the angle, the better. The
higher the angle, the lower the production.
And again, for different types of soils, we are going to have
different
production rates for the different sizes of the buckets. Let's
look at an example here as well. A contractor has decided to use a
two cubic yard clam shell mounted on a crawler crane to excavate for
the foundations of three concrete piers for a highway bridge. The
excavated material will be dumped in stockpiles for later use in
backfilling. The material is common earth, and the average
angle of swing is 120, degrees. Job and management conditions are
good. What is the estimated productivity of the clamshell in
bank cubic yards per hour.
So here we're gonna look at the table. The bucket size is two
cubic yards we are digging into
common Earth.
So two cubic yards with Common Earth gives us 160 band cubic
yards per hour.
Now the factor due to the swing angle, we have a swing angle of
120 degrees, which is a factor of point nine one. Therefore it's
going to reduce our production. Now, the factor due to good job
and management conditions is point seven, five from the table that we
have seen before. Therefore the productivity, the actual
production, is going to be ideal, times the correction factor one,
times the efficiency or correction factor two, and that gives 109
bank cubic yards per hour.
Now I hope that would be a good introduction to the detailed
discussions about different pieces of equipment. So we have learned
about the cycle time. We learned how to use the different tables
and the different correction factors. The equation is always
the same number of cycles per hour times the volume per cycle. And
there are some factors that affect that volume per cycle and the
number of cycles per hour, we have to include these correction
factors to obtain the actual production from the ideal
production from the tables that are given to us. I'll see you
later on in another lecture. Bye. Bye. You.