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Equipment Productivity

estimation

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GROUP B

Fourth Year of Study

MORNING STUDIES

2019-2020
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productivity of construction equipment

Introduction
The work of the Civil Engineering, Mining Industry and Building Sectors of the Construction
Industry requires a wide range of machinery with a number of basic uses. In order that the plant
should have additional flexibility, a variety of attachments have been developed over the years so
that machines can be quickly, and easily converted to perform different functions or to extend
their original functions. Once the equipment needs for an activity have been identified, the next
step is to conduct an equipment productivity analysis to select the optimum size. The objective is
to determine the number of units and the size of equipment that would permit the constructor to
accomplish the activity with a duration resulting in the lowest cost. Because most civil
engineering construction projects are awarded based on lowest cost, it is of utmost importance to
the constructor to select the proper equipment spread providing the lowest construction cost for
the project. The project is segmented into various activities; therefore, the lowest cost must be
determined for each activity.
Earthmoving equipment included in this discussion are:

. Bulldozers
. Front-end loaders
. Motor graders
. Scrapers
. Trucks

BULLDOZERS(1)

A bulldozer is a tractor unit with a blade attached to its front. The blade is used to push, shear,
cut, and roll material ahead of the tractor. It is an ideal surface earthmover that performs best at
about 3 mph. Each model of bulldozer has an operating range for blade size and adjustment.
Larger machines have greater operating ranges than smaller machines. A larger machine can
pitch and tilt deeper than a smaller machine typically. For heavy civil work, bulldozer blade
widths can range from 8ˊ to 22ˊ and operating weights can range from about 7 tons to over 120
tons. Maximum digging depth ranges from about 1.5ˊ to 2.5ˊ
Dozers are multifunctional pieces of equipment that may be used for any of the following
operations(3):
 Backfilling trenches
 Clearing and grubbing
 Creating stockpiles
 Excavating
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 Push loading scrapers

 Ripping compacted soil
 Shaping slopes
 Spreading materials
 Towing compaction equipment
Dozers are classified on the basis of running gear(2):
 Crawler type (see Fig.1)
 Wheel type (see Fig. 2)

The crawler dozer is a crawler tractor with a dozer blade fitted to the front. It is
a tracklaying machine used for bulk earthmoving, excavating, clearing scrub, spreading and
levelling etc. It can also act as a prime mover for towed equipment. Various blades can be fitted
to suit a particular application. (4)

Fig 1: Performance Chart for Tracked Dozer

Wheel Dozer The wheeled dozer as the name implies is a dozer on wheels as
opposed the tracks. The base machine is basically the same as the wheeled loader. The
wheeled dozer is used for bulk earthmoving, clearing scrub, spreading and levelling etc. It is
faster than the crawler dozer but has not the same traction in wet and muddy conditions. (4)

Fig 2: Performance Chart for Wheel Dozer

Swell and Shrinkage(3)

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When soil is loosened and excavated, it breaks up into different size particles creating air pockets
or voids that reduce its density. This increase in volume or reduction in density is known as
swell. The density of soil in its natural state, or in situ, is known as its bank density. When
excavated, the density of the soil decreases and is referred to as its loose density. To convert
bank density to loose density, we need to determine the percent swell of the soil, which is
defined as:

where:
VL is the loose volume
VB is the bank volume
Since density is weight per unit volume, we can rewrite Equation in terms of density as:

where:
DB is the bank density
DL is the loose density

for VB yields the following equation that will be useful in converting loose volume to bank
volume:

Bulldozer Production(1)
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Time components used for most tractor-powered equipment production cycles are similar to
those of the working bulldozer described in this section. Typical production cycles for
earthmoving equipment are very similar as well. Exact components will vary based on the work
setup and operation. The typical production cycle is the following:
1. The bulldozer positions to start excavation
2. The bulldozer scoops or digs for the length of a pass to fill the blade
3. The bulldozer hauls the load by rolling, crawling, pushing, or pulling
4. The load is discharged or dumped at the desired location
5. The bulldozer repositions to exit the dumpsite
6. The bulldozer backtracks to the loading location

load volume∗operation factor

Productivity = cycle time

Example 1(2) A Case 750K bulldozer with a 8ˊ blade is to be used to excavate and push
fairly loose dirt. According to the soils report, the dirt to be moved has a 23% swell factor. When
the dozer is hauled to the site a couple of blade loads are excavated to estimate a typical load.
The average H = 4ˊ the average load width is 6ˊ, and the load length is 9ˊ. Actually observing
and recording times for individual cycles and then finding the average observed cycle time is
probably the most accurate way to estimate a typical production cycle time. The load time
suggested by the manufacturer is about 0.08 min. Once the blade goes through the cut, the haul
push is about 200ˊ with an average speed of about 2.6 mph. Backtrack distance is about 240ˊ and
the dozer will travel at a speed of about 3.2 mph. Once back to the hole, the dozer takes about
0.06 min to reposition. The Case dealer suggests an O&O cost of about $55/h. Your operator
costs about $23/h with contractor outlay. What is the unit cost for the work if there is about 1200
bcy of surface dirt that must be moved by the 750 K

1. How much dirt (lcy) can be moved in one production cycle?

V = [(0.0138)(6ˊ)(4ˊ)(9ˊ)] = 2.98lcy/blade load

2. How much dirt (bcy) can be moved in one production cycle? The quantity takeoff is in
bcy so the lcy load must be converted to bcy

2.98 lcy=1.23 lcy/bcy = 2.42 bcy/production cycle

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Example 2(2)A track-type dozer equipped with a power shift (see Fig. 7.4) can push an
average
blade load of 6.15 Icy. The material being pushed is silty sand. The average push
distance is 90 ft. What production, in loose cubic yards, can be expected?
Push time: 2 mph average speed (sandy material):
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FRONT-END LOADERS
Front-end loaders typically are tractor powered and operate on tires. They are typically
articulated and very maneuverable, making them ideal for constricted areas. They are used
primarily for material moving and re-handling. They are ideal for scooping and hauling
materials in storage piles, where it is to be permanently placed, or loading it into dump
trucks. Loaders are ideal for dumping soil back into the hole after the necessary below grade
work is done. Tracked loaders may be required for extreme surface conditions demanding
greater traction or stability. Every concrete or asphalt batch plant has a tire equipped
frontend loader to stock the feed to the batch hopper with aggregate and sand.

Loader Production
Loaders are used many times with feed hoppers and dump trucks. The loader is sized by the
demand of the feed hopper or the size and number of dump trucks that can be filled.
Production cycle components are similar whether running on tracks or tires. The work
surface stability will influence the cycle time. Small skid-steer loaders are very
maneuverable
and cycle times might be less.
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SCRAPERS
Scrapers are used to excavate, haul and spread earth on large project where a large amount of
material has to be moved. There are two main types of scrapers:

- Towed scrapers
- Motorised scrapers
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Methods of Push-Loading Scrapers

Scraper Production
To load the scraper, the front end of the bowl (nearest the cab) is lowered until the attached
cutting edge penetrates the travel surface. As the scraper moves forward, the front apron of
the bowl is raised so that a strip of excavated earth can flow into the bowl. The amount of
excavated soil depends on the depth of penetration of the cutting edge. The scraper moves
forward until the bowl is full. The blade is lifted and the apron closes. Ripping (bulldozer with
ripper shanks) or tilling (tractor pulling a plow) the soil lift to be excavated prior to the
scraper making a pass can increase scraper production. Sometimes applying water will loosen
soil also To dump the scraper load, the cutting edge is set above the discharged material, raising
the
apron. The material is forced out by means of a movable ejector mounted at the rear of the bowl.
The size of the apron opening regulates the amount of material discharged and the
material lift depth.The capacity of the scraper bowl can be measured by volume or weight. When
the
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capacity or the weight is exceeded, operating efficiency decreases. Scraper volume is measured
in two ways in loose cubic yards. Struck volume is the loose cubic yards that a scraper
would hold if the top of the material were struck off even at the top of the bowl. Heaped
volume is the loose cubic yards that a scraper would hold with the material heaped and
sloping above the sides of the bowl. The heaped volume takes into account the fill factor.
The cycle time for a scraper is estimated by adding the fixed times to load, dump, turn
around, and spot for the next cut, and the variable or travel times to haul full and return
empty. Scraper rimpull, speed, and gradability performance can be verified by referring to
the rimpull, speed, and gradability curves for the model. The expected performance of the
scraper can be compared to these operating requirements of the work. Load times vary
based on power, bowl capacity, and site conditions and range from 0.4 to 1.0 min typically.
Maneuver and spread or maneuver and dump times range from 0.6 to 0.7 min. Additional
maneuvering (spotting) when approaching the cut might be required and should be added if
necessary.
Dozer-assisted means that the dozer makes contact with the back bale of the scraper as it
starts into the hole. The dozer is actually providing most of the pushing power to not only
make the cut, but also to transport the full bowl through and out (boost) of the cut. This
greatly optimizes what a bulldozer is designed to do and greatly reduces the power needed by
the scraper to excavate and start hauling when fully loaded. It is an ideal pairing of equipment
to optimize the capabilities of both.
To determine the number of scrapers that can be matched to one pusher or dozer, the
pusher cycle time must be determined. This cycle time includes match up and to contact with
the rear of the scraper, push through the hole, boost out of the hole, and maneuver to match
up to the next scraper coming through the hole
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References
1. ConstructionEquipment Managementfor Engineers,Estimators,and Owners DOUGLAS D. GRANSBERG

2. Construction Planning, Equipment and Methods by Robert perufiy

3. CONSTRUCTION EQUIPMENT MANAGEMENT John E. Schaufelberger

4. EARTH MOVING EQUIPMENT BASIC LEVEL MECHANICS