# Ihab Saad – Excavators

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.
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Five, 2.95 it's going to be lumped into larger particles. For wet

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clay, it's going to be anywhere between point five and point nine.

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Rock well blasted, relatively graded, is going to be point

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seven, 2.9

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and rock poorly blasted is going to be point four to point seven.

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So we're going to use only about half of the capacity of that

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bucket.

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Here we have an example estimate the hourly production for a loader

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with the bucket heaped capacity of five cubic yards. The soil is sand

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and the load factor. And the load factor is basically to convert

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from loose to bank volume, because that soil filling the scoop or

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filling the bucket is going to be in its loose condition. So if we

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want to convert it and get the production in bank, cubic yards

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per hour, we need to convert to bank volume. That load factor is

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point eight. The Cycle Time for the loader is one minute and 30

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seconds, which is 90 seconds, and the job efficiency is 80% so let's

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see how we're going to solve this. First of all, the bucket load is

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going to be equal to the fill factor times the bucket heat

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capacity. The fill factor for that type of soil based on this

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equation at this table here, we mentioned that it's going to be

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sand. So for sand is going to be around point nine to 1.0 we can

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choose either one or any range in between an average. So we're going

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to take, in this case, point nine times the bucket capacity, which

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is five, which means we're going to have soil volume inside the

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bucket of 4.5 loose cubic yards. Then we need to convert these

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loose cubic yards into bank cubic yards. So we're going to multiply

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by the load factor. So that's going to reduce the volume.

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Therefore each bucket is going to carry 3.6 bank cubic yards for

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each cycle. Number of cycles per hour is going to be one hour,

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which is 60 minutes divided by the cycle time. Now the cycle time was

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given into minutes and seconds, so we need to make sure that we are

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using the same unit, so 60 divided by one and a half, which is going

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to give us 40 cycles per hour. That is with the assumption that

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we're going to use 60 minutes per hour as production. But this is

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not always true. We're going to have to look at the efficiency.

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The efficiency was given to us as point eight or 80% therefore the

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volume, the total Audi production, is going to be the volume per

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cycle, times the number, number of cycles per hour, times the

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efficiency. And that gives the total production of 115.2

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bank cubic yards per hour.

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Again, here's the table that we use to get the factor for the

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sand.

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The hydraulic excavator, also called hydraulic hoe or hydraulic

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excavator backhoe, depending on the way the bucket is facing if

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it's facing forward, it's a hoe or a shovel. If it's facing backward,

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it's a backhoe. It digs by pulling the dipper back towards the

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machine. So there's going to be a hydraulic force

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pushing that bucket into the soil and then pulling it to get out of

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the soil, with a breakout force to take the soil and to be scooped

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away. When the dipper is filled, it's curled up to reduce the

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spinach through the hydraulic arm of the equipment,

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and that's basically what it looks like. So here's the articulated

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hydraulic arm

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with pistons, and here's the digger or the bucket or the

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dipper, so it has some teeth at the edge to help loosen and break

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the soil. And once it's full, it's going to be tilted upwards to

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avoid or to reduce the spillage.

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It's used for trenching work, as it can also lay pipes, pull trench

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shields or sheet piles, and backfill the trench. After the

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operation of laying the pipe is complete,

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the dipping width of the bucket should match the trench width to

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maximize production. So if we're going to use, for example, a

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the width of the bucket is three feet, then the the width of the

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trench should be around that these buckets are movable. We can

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exchange these buckets and change the bucket size depending on the

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operation that we're going to be using it for.

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Telescoping booms may replace articulated booms. So instead of

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the articulation, we may have telescoping booms to extend the

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reach of that of that hydraulic excavator,

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the generic equation for estimating the excavator

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production is going to be pretty much the same thing, by the way,

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which is number of cycles per hour times the volume per cycle. But

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here we are basically

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adding some other factors.

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That affect the production rate. So it's equal to c times s times v

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times B times e. Let's look at what each one of these means. C is

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the number of cycles per hour. S is the swing depth factor. Now

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imagine the cycle is going to include digging, swinging,

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dumping, swinging again and starting to dig. The wider that

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angle of swing, the slower the operation is going to be, because

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you have to move farther distance. Therefore, if that angle of swing

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is relatively narrow, that's going to expedite the excavation, which

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means reducing the cycle time, which means more cycles per hour,

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which means more production per hour.

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V is the heaped bucket volume. B is the bucket fill factor, which

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we have seen depending on the type of soil. And E is the job

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efficiency, which is how many productive minutes per hour can

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you get out of this piece of equipment?

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We have some effect from the job conditions. Depending on the job

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conditions, we can have either excellent job conditions, above

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average, average, below average and severe. And for different

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sizes of buckets, we can have estimated cycle times. So for

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example, the excellent conditions are characterized as easy digging.

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We're digging through easy soil to break into unpacked Earth, sand,

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ditch, cleaning, etc, digging to less than 40% of the machines

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maximum digging depth. So the arm is not going to be extended to the

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maximum.

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And the swing angle is less than 30 degrees. Again, the amount of

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swing is relatively limited. You dump into a spoil pile, so you

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don't have to maneuver and to adjust to dump into a truck, no

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obstructions. You can see the dumping area. You can see the

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digging area. So that's going to be excellent conditions for a less

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than a one cubic yard bucket, the cycle time is going to be about 13

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seconds. One to two cubic yard buckets going to be about 15. Two

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to three cubic yards, it's going to be 16 and so on. The larger the

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bucket, of course, the longer the cycle time.

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Above average conditions are characterized as medium digging.

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Now it's not as easy as the previous one, but packed Earth,

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relatively more consolidated and compacted, dry clay soil was less

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than 25% rock content. Now the depth, instead of being 40% is

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going to increase to about 50% so more reaching out with the arm and

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the swing angles less than 60 degrees. So still here, in the

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first case, we have 30 degrees. Now we have about 60 degrees. It's

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still large dump target, so it could be a large truck or an open

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area and few obstructions, as you can see, that's going to extend

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the cycle time by about two seconds, two out of 13. That's

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about almost 1/7 so almost 14% reduction

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and so on. If we keep going down, we're going to see that the

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average conditions, for example, more hard packed soil depth even

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more 70% and the angle of swing up to 90 degrees and loading into

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trucks, so you have to spot and you have to adjust, you have to

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maneuver, which, again, is going to slow down the operation up to

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when we reach the severe conditions we have digging through

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tough and hard soil

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depth over 90% of the maximum digging depth. So we are almost

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extended to the maximum and a swing angle of over 120 degrees.

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So basically we are moving more than 90 degrees. It's basically

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almost facing backward, and it's a small dump target requiring

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maximum reach, so you have to maneuver to make sure that you

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don't spill that soil out of the dump truck, so it requires

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additional maneuvering. Now, comparing between the excellent

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job conditions and the severe conditions we find that we have

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here, for example, difference of eight seconds, eight out of 13.

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That's almost 60% which means that the production is going to be

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reduced considerably.

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Shovels similar to the backhoe, but in this case, is going to be

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facing forward. The bucket is going to be facing forward. Is

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going to use two kinds of forces to break down the soil. Is going

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to have something called crowding force, which moves downwards and

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then break out force, which is gonna lift that soil and dump it

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into into the truck. So dig with a combination of crowding or

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downforce and breakout or forward forces. It has a limited ability

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to dig below the track level, because, again, it's gonna be a

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risk of over tipping, tipping forward. So we're gonna try to

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have.

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With that,

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the shovel production, like the backhoe, is going to be exactly

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the same, C times s times v times B times E, and the production is

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mainly affected by the swing angle and the loss time during the

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production cycle, depending on the type of soil and the different job

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conditions, as we have seen the previous day, the angle of swing

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between digging and dumping should be kept to a minimum to improve

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production, as we have seen again, difference between 30 degrees and

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120 degrees. So

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looking at an example here, for example, other factors to improve

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the production having a level floor of cut that's going to help

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with the stability, moving frequently to be closer to the

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working phase, instead of extending the arm, moving on the

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tracks to get closer,

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keeping digger teeth sharp, which is going to help with the crowding

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force and better training for the operator, a skilled operator can

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definitely achieve more than an unskilled operator. So the ideal

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production is going to be equal to the bucket, bucket capacity times

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the fill factor divided by the ideal cycle time. That's going to

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give us the ideal production in again, bank cubic yards per hour.

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And here's some again,

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fill factors for moist loam or sandy clay, one to 1.1 sand and

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gravel point nine, five to 1.1 and so on.

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Now, based on the the idea shovel productivity in bank cubic yards

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per hour, this is sort of the theoretical production rate as

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given in the manual of that piece of equipment for different types

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of soils, for different bucket capacities. So for example, for

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tough clay and a one and a half cubic yard bucket is going to be

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tough clay

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and one and a half, that's going to give us 210

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bank cubic yards per hour. Again, this is the ideal production, not

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the actual production. Therefore, the ideal production can be

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obtained in one of two ways, either through a table like this,

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or through an equation like this, one with the bucket capacity times

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field factor divided by the ideal cycle time.

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The angle of swing is going to give us a modifying factor, with

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the 1.0 being represented by 90 degrees and 100% of the optimum

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depth, we're going to see that in an example in just a minute. If

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you dig less than the optimum depth or much more than the

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optimal depth, that's going to affect the production. If the

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angle of swing increases or decreases again, that's going to

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affect the production.

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Job conditions. We have both job conditions and management

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conditions. Management conditions basically something like having a

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good operator, a good observer, a good superintendent, good

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monitoring of the operation, you have the the trucks lined up very

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close to where the soil is going to be done, so that the shovel

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doesn't have to move much. Job conditions, depending on how

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graded the site is, if you don't have too many obstacles,

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the equipment is in good condition and so on. These are things that

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also we can't control. So we have another modifying factor based on

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the management conditions and the job conditions. For Good job

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conditions, good management conditions, we get, for example, a

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factor of 75%

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Let's now look at another example. A contractor has a project to

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excavate an apartment complex and must construct a three foot

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compacted fill to support the parking garage. The borrow site

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where we're going to be borrowing the soil is three miles from the

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construction site, so there's going to be a shovel over there,

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or a backhoe, or whatever piece of equipment, and that's going to

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dump into trucks, and the trucks are going to bring that soil to

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the site for utilization. The borrow site is three miles from

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the construction construction site, and 10 cubic yard. 10 cubic

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yard dump trucks

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will be used to haul the kneaded fill a two cubic yard shovel would

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be used to load the dump trucks. The material is tough, dry clay

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with a swell factor of 35%

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the height of the cut at the borrow site is 11.6 feet, and the

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angle of swing of the shovel is 150 degrees. So estimate the ideal

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production using the table and using the equation, we're going to

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do that and then estimate the actual production for good job and

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management conditions. The optimum digging depth of the shovel is 9.8

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feet. This is the optimum, and this is the actual so let's see

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this equation. This this row.

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Again,

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with the optimum depth of cut of various sizes of Jetline buckets.

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So here is going to give us four different types of soil. What

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would be the optimum depth of cut for a three hot three quarters

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cubic yard, for one and a quarter cubic yards and so on. And also

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here we have the operating factors, the job conditions and

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the management conditions, exactly the same table as we have seen

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before. And then we have also the drag line productivity correction

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factor based on the percentage of the optimum depth of cut and the

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angle of swing, as we have seen with the shovel, and ideal

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productivity based on

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the bucket size in bank, cubic yards per hour. Let's

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look at an example. The contractor has a project to construct a large

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parking lot for a shopping center. The contractor decided to use a

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crawler drag line. Crawler drag line, which means it's gonna be on

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tracks with one and three quarters cubic yard bucket to excavate a

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large drainage ditch to collect and remove storm water runoff.

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The excavated soil is common earth, and the average depth of

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cut is 7.6 feet.

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The excavated material will be loaded in dump trucks for removal

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from site. The angle of swing is 120 degrees. Job conditions are

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good and management conditions are excellent. So it's not good and

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good job conditions, good management conditions Excellent.

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What is the estimated dragline productivity in bank cubic yards

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per hour? And then we're going to add a couple of other layers. If

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the volume to be removed is 3200 bank cubic yards and the rental

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cost per day for that dragline is \$1,800

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how long would the operation take, and how much will it cost? So now

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we are also looking at durations and cost estimating for that piece

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of equipment.

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So from the table, the ideal production for one and three

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quarters bank cubic cubic yard bucket and Common Earth is 210

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bank cubic yards per hour. We're just going to look at the table.

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The optimum depth of cut is nine and a half feet. The percent of

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the optimum depth of cut is because the actual depth is 7.6 so

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it's 7.6 times 100% divided by 9.5 which gives 80% now using the 80%

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factor with 120 degrees the angle of swing gives us a modification

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factor of point nine for good job and excellent management

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conditions, the factor is going to be point seven eight. Therefore

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the actual dragline production is going to be the ideal 210

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times. The factor due to the swing angle and the depth of cut times

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the other factor due to the job and management conditions, which

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gives 147.42

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bank cubic yards per hour.

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The total volume that needs to be excavated is 3200 bank cubic

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yards. So dividing that by the production per hour is going to

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give us 21.7 hours, which is basically assuming eight hours of

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work per day is going to be almost three days. We're not going to pay

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for a fraction of a day. So we're going to pay for the third day,

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whole day. Therefore the cost of operation is going to be three

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days times \$1,800 per day, which gives \$5,400

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that's the cost of that operation.

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Another piece of equipment, similar to the drag line, is going

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to be the clam shell. So

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it's going to be the same machine, but the attachment at the edge of

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the boom of the crane is going to be different. In this case, it's

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going to be a drag line. It's capable of digging at higher

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depths. That's one of the benefits of the clamshell. It lacks

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positive digging action and lateral control of the shovel or

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the backhoe. Again, positive digging, which means the

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articulated hydraulic arm is going to give that hydraulic force, that

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crowding force, but in this case, it's going to rely, like the drag

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line on its own weight and on gravity.

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It's used for excavating vertical shafts and footings for

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foundations. So this is what it looks like.

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And as you can see, we have here the lines that are used to open

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and close that clamshell, which has some teeth, again, to cut

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through the soil as possible.

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It's also used sometimes for grains and in Marine Operations

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and so on.

00:29:53 --> 00:29:57

The production is based on the equation, same generic equation,

00:29:57 --> 00:29:59

volume per cycle, time, cycles per hour, and.

00:30:00 --> 00:30:04

So the maximum load should be limited to 80% of safe lifting

00:30:04 --> 00:30:07

capacity for rubber tired equipment and 90% for crawler

00:30:07 --> 00:30:11

mounted equipment. This is a relative factor of safety, just to

00:30:11 --> 00:30:14

make sure that we're not going to have any over tipping or any

00:30:15 --> 00:30:18

stability issues with the with the equipment.

00:30:19 --> 00:30:23

And again, here we have a table that shows the different cranes

00:30:24 --> 00:30:27

and at the different boom lengths, what's going to be the operating

00:30:27 --> 00:30:31

radius, and what's going to be the total load that it that it can

00:30:31 --> 00:30:37

carry at that the tip of that boom. And this shows basically the

00:30:37 --> 00:30:43

capacity of the clamshell bucket itself, the rated capacity is

00:30:43 --> 00:30:48

equal to VS which is this bottom half plus Ve, the top half, which

00:30:48 --> 00:30:53

is the heaping minus Vm, which is at the joint where it opens and

00:30:53 --> 00:30:55

closes the clamshell.

00:30:56 --> 00:31:01

And here it shows again, the different weights, because we can

00:31:01 --> 00:31:04

have either a general purpose bucket, a heavy duty bucket or a

00:31:04 --> 00:31:07

light duty bucket. Each one of them is going to have a different

00:31:07 --> 00:31:11

weight on its own for the different rated capacities and

00:31:11 --> 00:31:12

different sizes of these buckets.

00:31:18 --> 00:31:21

To improve the clamshell production, we're going to have

00:31:21 --> 00:31:25

the dumping radius the same as the digging radius. So the the boom is

00:31:25 --> 00:31:29

going to rotate and is going to dump at the same distance where

00:31:29 --> 00:31:33

it's digging from keeping the machine level to avoid swinging

00:31:33 --> 00:31:37

uphill or downhill, because again, swinging uphill or downhill is

00:31:37 --> 00:31:40

going to affect stability, and it's going to affect the effective

00:31:40 --> 00:31:42

length of the boom of the crane.

00:31:44 --> 00:31:48

So again, with the larger angle of swing, we're going to have

00:31:48 --> 00:31:52

different correction factors. The lower the angle, the better. The

00:31:52 --> 00:31:54

higher the angle, the lower the production.

00:31:57 --> 00:32:01

And again, for different types of soils, we are going to have

00:32:01 --> 00:32:01

different

00:32:03 --> 00:32:06

production rates for the different sizes of the buckets. Let's

00:32:09 --> 00:32:13

look at an example here as well. A contractor has decided to use a

00:32:13 --> 00:32:18

two cubic yard clam shell mounted on a crawler crane to excavate for

00:32:18 --> 00:32:23

the foundations of three concrete piers for a highway bridge. The

00:32:23 --> 00:32:26

excavated material will be dumped in stockpiles for later use in

00:32:26 --> 00:32:31

backfilling. The material is common earth, and the average

00:32:31 --> 00:32:35

angle of swing is 120, degrees. Job and management conditions are

00:32:35 --> 00:32:40

good. What is the estimated productivity of the clamshell in

00:32:40 --> 00:32:42

bank cubic yards per hour.

00:32:43 --> 00:32:48

So here we're gonna look at the table. The bucket size is two

00:32:48 --> 00:32:52

cubic yards we are digging into

00:32:55 --> 00:32:56

common Earth.

00:32:57 --> 00:33:02

So two cubic yards with Common Earth gives us 160 band cubic

00:33:02 --> 00:33:03

yards per hour.

00:33:05 --> 00:33:09

Now the factor due to the swing angle, we have a swing angle of

00:33:09 --> 00:33:13

120 degrees, which is a factor of point nine one. Therefore it's

00:33:13 --> 00:33:18

going to reduce our production. Now, the factor due to good job

00:33:18 --> 00:33:21

and management conditions is point seven, five from the table that we

00:33:21 --> 00:33:24

have seen before. Therefore the productivity, the actual

00:33:24 --> 00:33:29

production, is going to be ideal, times the correction factor one,

00:33:29 --> 00:33:33

times the efficiency or correction factor two, and that gives 109

00:33:34 --> 00:33:35

bank cubic yards per hour.

00:33:41 --> 00:33:46

Now I hope that would be a good introduction to the detailed

00:33:46 --> 00:33:49

discussions about different pieces of equipment. So we have learned

00:33:49 --> 00:33:53

about the cycle time. We learned how to use the different tables

00:33:53 --> 00:33:56

and the different correction factors. The equation is always

00:33:56 --> 00:34:00

the same number of cycles per hour times the volume per cycle. And

00:34:00 --> 00:34:04

there are some factors that affect that volume per cycle and the

00:34:04 --> 00:34:07

number of cycles per hour, we have to include these correction

00:34:07 --> 00:34:11

factors to obtain the actual production from the ideal

00:34:11 --> 00:34:15

production from the tables that are given to us. I'll see you

00:34:15 --> 00:34:17

later on in another lecture. Bye. Bye. You.

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