# Ihab Saad – Excavators

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## AI: Transcript ©

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.