NOTES - 03
EQUIPMENT MANAGEMENT
TIPS FOR THE CONSTRUCTION ENGINEERS
AND PLANT &
MACHINERY ENGINEERS
AN INTRODUCTION TO
CONSTRUCTION PLANT AND EQUIPMENT
AFTER THE INTO MORE
EQUIPMENT MANAGEMENT TIPS
THIS IS APPLICATION OF
YOUR KNOWLEDGE AND EXPERIENCE
A LEARNING FROM THE
FIELD WORK
I. A GENERAL
CLASSIFICATION OF EQUIPMENT
The
equipment used in road construction can be classified as follows:
A.
Equipment for Quarrying and Stone Crushing
B.
Earthmoving Equipment
C.
Compaction equipment
D.
Bitumen (Asphalt) plants
E.
Concreting equipment
F.
Miscellaneous equipment
A. EQUIPMENT FOR QUARRYING AND STONE CRUSHING:
This
is used for reducing rock in the form of rubble or boulders) in small-small
size material of uniform size.
Generally
a jaw crusher driven by diesel engine or electric motor is used. As the name
suggests, the crusher has two jaws one fixed and the other moving. The jaw
plates can be removed and replaced. They are made of manganese steel. Stone is
reduced to aggregate due to crushing between jaws and is graded into different
sizes by a rotary screen placed at slight inclination to the horizontal.
Granulator:
Essentially it is a crusher but it takes small size material and reduces to
small size chips. Output in terms of tones and the width of the mouth opening
is the base for classification.
Jack
Hammer: This is a percussion type drill operated by compressed air. It can be
handled by a man. A jack hammer requires uninterrupted supply of compressed air
at the rate of 2 cu.m/minute (@ 7.03 kg/sq.cm.).
If
it is to be used to drill holes against vertical face of the rock, jack hammer
is mounted on a suitable frame and used with a long drilling rod. It is then
called a wagon drill.
Diamond
drill: This is rotary drill of abrasive type. The drill bit is formed by a
metal matrix in which a number of industrial diamonds are embedded. As the
drill bit rotates the diamonds cut an annular ring in the rock whereby a core
is formed which is then lifted into the collector. This drill is extensively
used in foundation investigation, rock cutting and to obtain samples of rock in
the form of cores.
MOTOR
GRADERS
This
is primarily designed for the earth work operation of leveling, shaping,
grading, finishing etc. It is self propelled with four or six wheels. It has
long wheel base due to which it can travel over an uneven ground. It is
provided with scarifier teeth which loosens the earth before the blade is used
for grading. Raising or lowering the ends of blade and turning the blade
horizontally or vertically is done through power control cables. Engine HP
specifies the capacity.
Attachments
and different uses:
i.
Ripper: This is an attachment consisting of teeth. It is used to loosen hard
material so that scraper can load properly.
ii.
Bulldozer: This is an soil cutting attachment mounted on front of grader. It
consists of dozer blade having replaceable cutting edges. It is known as
straight dozer if blade is fixed straight and at right angle to the tracks. If
it is fixed at an angle, it is called angle dozer. The capacity of the
bulldozer is specified in terms of blade dimensions.
iii.
Push plate: Here, instead of a dozer blade a blade with straight alignment
known as pusher blade is mounted on front of grader.
B.
EARTHMOVING EQUIPMENT (EXCAVATORS):
This
is a basic earthmoving machine which can be used for different works with
different types of front attachments. It consists of the following:
a.
Basic component providing locomotion and power. This remains fixed for all
front end attachments.
b.
Revolving superstructure and mounting. Mounting are of three types - crawler,
truck and wheel.
c.
Attachments to suit the work in hand. These are interchangeable. There are four
types of attachments.
i.
Shovel: Excavators fitted with this attachment is known as shovel. It can be used
for all sorts of material. It can be used to excavate at its own level or at
levels higher enough for crowding action. Dumpers are needed with this
equipment for disposing the excavated material.
ii.
Dragline: Excavator with a dragline attachment is called dragline. The
attachment consists of a bucket which is pulled towards the machine for filling
after which it is lifted and swung away with the boom. Dragline can dig only
soft to medium hard material and it can excavate at or below its base level. It
can also be used to remove material under water.
iii.
Clamshell or grab: In a clamshell a grab bucket replaces dragging bucket.
Digging can be done at, below or above the base level. It operates in vertical
range. The bucket has teeth at its lower end. As the bucket hits the surface
(soft or medium hard) it collects the material which is then lifted, swung away
and discharged.
iv.
Cranes: Though this is not an excavating machine it can be used for lifting and
removing away the loads. The boom has at its end a hook in place of bucket.
Cranes can, as well, be independent equipment.
C. COMPACTION EQUIPMENT
i.
Smooth wheel roller: Most commonly used roller in compaction of roads.
Compaction is achieved by the weight of the roller. This gives satisfactory
results on all types of surfaces like water bound macadam, bituminous surfaces
etc. It is also suitable for compacting subgrades of the roads.
ii.
Tandem Roller: This is also a smooth wheeled roller with two rolling wheels of
approximately the same width - one at the front and the other at the rear.
Compaction with this type is better. This roller is better for rolling
finishing surfaces as it produces smooth and even surface.
iii.
Sheep's foot roller: This roller has a metal drum on the surface of which are
metal studs forming teeth (Projections). The roller can be self propelled or
towed.
During
the movement of the roller the teeth penetrate and press the soil. It is
suitable for compacting cohesive soil to a depth of 5 cm. They can be of single
drum or multiple drums.
iv.
Pneumatic tyred roller: The kneading action of tyres brings about compaction.
Essentially the roller consists of a body mounted on rubber tyred wheels, in
two rows - one at the front and the other at the rear. There is one wheel in
the rear row and as a result total wheels are odd in number. This roller is
useful for compacting fine grained soils.
v.
Vibratory roller: These rollers exert both static and dynamic pressure due to
vibration. It is believed that this roller gives almost double compaction of
the non-vibratory roller of the same weight. The roller is effective on
non-cohesive soils.
vi.
Power Rammer: These types are useful for compacting narrow and restricted areas
around the structure like piers, abutment etc. Both vibration and impact in the
forms of vibrations (at the rate of 50-70 blows per minute).
vii.
Frog Hammer: This is heavier than the normal power rammer. In the frog hammer
the compacting effect is transferred in the form of blows delivered in quick
succession by a weight which is lifted and allowed to fall freely.
Normally
all the rollers are designated by their weight while the power rammer and frog
hammer are rated both in terms of the weight and number of blows per minute.
D. BITUMEN (ASPHALT) PLANT
i.
Bitumen Boiler: This is used for heating bitumen from drums. Boiler is fitted
with a fire box, flue tube and chimney. Full asphalt drums are lifted to the
top where the contents are emptied and heated by flame or combustion gasses.
Fuel used may be coal, wood or oil. The boiler is mounted on wheels and can be
towed from one location to the other.
ii.
Bitumen Spraying equipment: Bitumen boiler is fitted with a pump with a
strainer in the suction pipe. The pump is operated either by hand or
mechanically. On the delivery side there are flexible pipe spray bars and spray
nozzle.
The
rate of application of bitumen can vary by adjusting the height of the spraying
nozzle above the ground. Uniformity of spraying is controlled by the angle at
which the spray bar is kept.
iii.
Bitumen tanker: When bulk bitumen is to be transported, tanker is used. It is
mounted on a truck or a trailer. Capacity of the tanker may range from 5000 to
15000 liters. Oil fired burners are used to maintain the temperature of bitumen
during transit. Unloading is done by using compressed air or gear pump.
iv.
Bitumen pressure distributor: This equipment is used when a specified quantity
of hot bitumen is to be sprayed uniformly for grouting or surface dressing. It
is used with bulk bitumen supply. The set up consists of an insulated tank
mounted on a truck chassis. Heating of bitumen is done by oil fired burners. A
pump - power driven or compressed air driven - is fitted to the vehicle to
handle hot bitumen. At the rear of the truck a spray bar unit with nozzles is provided.
A metering device controls the quantity of bitumen while the rate of spread on
road is maintained by driving the truck at a uniform speed.
v.
Hot mix plant: Base course as well as wearing surface may be provided with
premixed bituminous surface. Hot mix plants are convenient for preparing
required premixed material. Aggregate and bitumen are heated to specified
temperature and are then mixed thoroughly along with filler material in the
specified proportion. Such plants may be batch plant or continuous ones.
Further, they can be portable, mobile or stationary. They may be driven by
diesel engine or electric motors and range in capacity from 3 tons per hour to
60 tons per hour.
Main
components of a hot mix plant are:
i.
Feeder unit
ii.
Screening unit
iii.
Dryer unit
iv.
Gradation control
v.
Bitumen heating unit
vi.
Mixer unit
The
mixing is done in the following steps:
i.
Feed the aggregate into dryer unit and heat it to the desired temperature.
ii.
Separate the aggregate as per size in the screening unit and store it in bins.
iii.
Feed aggregate, filler material and hot bitumen in the pug mill (mixer unit).
The mixing is done thoroughly.
iv.
Discharge the contents of the mixer unit into tipping trucks.
Paver
Finisher:
This
equipment is used for spreading the hot mixed material on the road surface,
compacting it and finishing it before it cools. Hot mix obtained from the hot
mix plant is conveyed by tipping trucks and loaded into the hopper of the paver
finisher. Width and thickness to which material is to be spread can be
adjusted. The paver finisher moves on pneumatic wheels or crawler tracks. This
gives a surface of uniform width and thickness and finish is very good. The
latest finishers are fitted with electronic devices which exercise a close
control on the thickness and width.
E. CONCRETING EQUIPMENT
i.
Concrete mixer: Concrete is obtained by mixing cement, fine aggregate, coarse
aggregate and water in specified proportion.
For
work of small and medium magnitude, where the ingredients mixed on volumetric
basis can produce concrete of required strength, rotating drum type mixers are
used. They may be tilting drum type or non-tilting drum type. Tilting drum
gives more satisfactory results. For major bridge work where large quantities
of concrete of high quality is required and where the investment is justified a
central weigh batching and mixing plants are more suitable. Basically it
consists of multi compartment overhead bins for aggregates of different sizes
and cement. Contents of these bins are drawn into weighing hoppers where
specified quantities of ingredients for a batch are weighed. They are then
discharged into mixer where the accurately measured quantity of water is added
and the mixing is done. The mixed concrete is then dumped into buckets, tipping
trucks etc. for conveying concrete to the place of deposition.
Conveying
the Concrete:
For
narrow road work the concrete may be conveyed manually or through wheel
barrows. Taking into consideration the place of mixing, place of deposition,
the quantity to be handled, it has to be ensured that there is no hold up and
work proceeds smoothly uninterrupted.
On
major bridge works suitable equipment like hoists and winches or cranes with
buckets etc. will have to be used.
Compaction
of concrete: For uniform results and quick work mechanical compaction is
desirable. The equipment most commonly used for concrete compaction is vibrator
of which there are varieties to suit the place and nature of work.
Internal
or immersion vibrators are used for deep and narrow sections. The vibrating
needles are available in 40 mm dia. and 60 mm dia. Length may be up-to 520 mm.
These needless are immersed in concrete at regular intervals to bring about
compaction.
Surface
or external vibrators: They are suitable where depth is limited. For concrete
road surface vibrators mounted on teak wood templates are used. In certain
special situation form vibrators may also be found suitable.
Concrete
vibrators work on compressed air, electric motor or petrol engine. The
frequency of vibration may vary between 7,000 to 10,000 V.P.M.
F. MISCELLANEOUS EQUIPMENT
i.
Air compressor: This is a device used for compressing air at atmospheric
pressure to a desired higher pressure. It is driven electrically or by engine.
Compressed air is used as energy for operating tools, concrete vibrators etc.
ii.
Front end loader: This is essentially tractor - mounted, loading loose
materials into truck or bins. The tractor may be either crawler or wheel type.
Most of the models are front loading and front tipping but some have an
arrangement for front loading and tipping in the rear.
iii.
Tipping trucks: These are the trucks having bodies to convey the material,
which can be tipped by hydraulic ram. They can be used for transporting a
variety of materials like excavated stuff; aggregate or hot mix bituminous
material. In a heavy duty application they are known as dumpers and have the
facility of dumping centers through bottom or side of the body.
iv.
Soil Stabilizer: Sometimes natural soil does not meet the requirements and has
to be treated by adding some material like cement, sand etc. to improve its
characteristics. The process is called soil stabilization and consists in
removing soil, mixing it with additional material, spreading the material and
compacting it. The equipment used for this purpose is called soil stabilizer.
Basically
it is a wheeled tractor having an attachment to cut the soil to the specified
depth, pulverize it, mix it intimately with additives, spread it to the
required thickness and finally compact it. If compaction done by the soil
stabilizer is not adequate suitable compacting equipment is used.
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