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Demolition Tools & Machinery
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DEMOLITION TOOLS &
MACHINERY
Details of the various Tools and Machinery used in demolition and
dismantling work:
Hydraulic Splitter
Hydraulic splitters apply lateral forces
against the inside of holes drilled into concrete in order to
break up concrete with a minimum of noise and flying debris.
About the size of a jackhammer, the tool utilizes a shaft known as
a plug-and-feather assembly which, when inserted into a drilled
hole and forced downward by the tool’s piston, creates the
lateral forces that break the concrete. No heavy impact is
utilized to form the crack, which spreads quickly and without any
noise between the pre-drilled holes until the concrete is split
into manageable pieces.
The typical hydraulic splitter exerts a force between about 150
and 400 tons, depending on make and model. As with most pieces of
equipment of this type, the smaller models with a force capacity
on the lower end of the scale are used for more lightweight work,
or where the equipment must be able to be handled more easily,
such as in horizontal or overhead work. Larger capacity models are
capable of splitting mass concrete and hard rock.
Hydraulic splitters may be available in gas- and
electrically-powered models, but most contractors prefer
air-powered hydraulic pumps, as the tool’s air-compressor can
also be used to power the drills used to form the holes in the
concrete. Multiple hydraulic splitters can be set up to run
side-by-side off the same hydraulic pump, allowing for a greater
combined splitting force, helpful when breaking up particularly
thick or dense concrete.
To correctly operate a splitter, the holes must be drilled
straight into the concrete at the exact diameter specified for the
splitter, and be deep enough to accommodate the plug when fully
extended. The plug and feathers have to be kept well lubricated in
order to remain in working condition.
Expansive Demolition Agents
The expansive demolition agent is a cementitious powder. Using a
drill with a mixing attachment, the powder is mixed in a bucket
and poured or tamped into drilled holes. As the mix hardens and
expands, the concrete cracks between the drilled holes. As the
hairline cracks develop over the slab, they run outward into each
other and grow wider, until the slab literally falls apart under
an expansive force that can exceed 12,000 psi.
Used correctly, expansive demolition agents produce little dust or
debris. The only labor involved is in drilling the holes, mixing
and applying the agent, and then hauling the broken up pieces of
concrete away.
One cautionary note: With expansive demolition agents
involves a phenomenon known as "blow-out." This happens
if the powder mix gets too hot and reacts with the water too
quickly for the material to expand laterally. The result can range
from a puff of smoke to a loud gunshot-like sound that can send
hardened mix 30 feet into the air. Since blow-outs are
unpredictable, safety procedures require workers to stay well away
from the drilled holes once the mix has been poured into them. If
a blow-out does occur, however, it usually has little effect on
the project, since the remaining mix in the hole is usually still
effective enough to crack the concrete.
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Demolition Hammer
Demolition hammers are similar to rotary
hammers and are used in the same way in terms of delivery hammer
blows. However, demolition hammers deliver hammering action only,
unlike rotary hammers, which can also be used to bore holes.
What demolition hammers lack in this regard in terms of
versatility, however, they make up in punch. The demolition hammer
is able to deliver more powerful blows than rotary hammers, since
they typically have about 35% more power. This is due to the fewer
parts in a demolition hammer, and sometimes a longer piston
stroke, as well.
While the demolition hammer delivers fewer blows per minute than a
rotary hammer, the increased strength of the tool actually makes
it a quicker and more efficient means of demolishing concrete and
masonry.
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Rotary Hammer
Big rotary hammers are known as either SDS-max
or spline-drive hammers, depending on whether they accept SDS-max
or spline-shank bits.
The versatility of the rotary hammer allows it to demolish
concrete with a hammer only method, or to deliver rotary-hammer
action for boring holes in concrete. This is done in the rotary
hammer mode by driving twist drills and core bits, or in the
hammer only mode to utilize everything from flat chisels to
ground-rod drivers.
However, this versatility comes at a price, since rotary hammers
have an extra drive train that rotates drill bits in the
rotary-hammer mode. This siphons off energy and decreases
efficiency in the hammer-only mode.
Rotary hammers use a battering ram that floats inside a cylinder
and is launched and retrieved by a piston. A shock-absorbing
airspace between the ram and the piston compresses and drives the
ram forward as the piston advances, then sucks it back as the
piston retracts.
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Chipping Hammer
Chipping hammers are lightweight, hand-held
concrete breakers that can be easily positioned to break vertical
and overhead surfaces. By offering a controlled chipping action,
these hammers allow operators to precisely chip away only specific
areas.
The smallest chipping hammers, powered electrically,
pneumatically, or hydraulically, usually weight between 5 and 30
pounds. As usual, a good indication of the power of the tools is
their weight. The heavier the tool, the more powerful it is apt to
be. The chipping action of this type of equipment is rapid,
ranging from 900 to 3,000 blows per minute.
Because chipping hammers are most often used to break concrete on
vertical and overhead surfaces, they must be light. They are
maneuvered by holding a handle at the back of the tool and
gripping the tool by its shaft with the other hand. Some tools
have a second handle along the side. This gives operators control
of the tool's weight and the ability to direct its chipping action
at different angles.
By offering a controlled chipping action, these hammers allow
operators to precisely chip away only specific areas.
Manufacturers are offering more options than ever on their
chipping hammers, including rotating, shock-absorbing handles, and
heat shields.
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Pavement Breaker
Hand-held pavement breakers may be thought
of as a kind of heavy-duty version of the chipping hammer.
The difference is that pavement breakers are heavier, more
powerful tools that are usually operated perpendicular to the
ground. Because of this, a T-shaped handle is the most common
design for pavement breakers. A few lightweight breakers are
designed with a D-shaped handle that allows the operator to pick
the breaker up and operate it horizontally.
Like chipping hammers, pavement breakers are powered
hydraulically, electrically, or pneumatically. The pounding action
of breakers is usually slightly slower than that of chipping
hammers, ranging from 800 blows per minute to close to 2,000 blows
per minute.
Pavement breakers weigh from 30 to 99 pounds. A good indication of
a breaker's power is its weight.
Pavement breakers weighing between 40 and 50 pounds are
particularly useful for removing concrete for partial-depth
pavement repair. The weight of these tools gives them the power
needed to break up a few inches of concrete without being so heavy
that they demolish the entire pavement.
The pavement breakers weighing 60 pounds and more can handle
medium-to-heavy demolition jobs with reinforced concrete, and are
used to demolish pavements, roads, and thick concrete. One example
of the type of work that the heaviest breakers do is demolition of
high-strength concrete found on airport runways.
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Mounted Breakers
The speed, versatility, and impact energy of
mounted breakers are widely used by contractors to demolish
heavily reinforced walls, slabs and decks.
Excavator-mounted breakers can have production rates of more than
1,100 cubic yards of unreinforced concrete per day. Productivity
varies depending on a variety of factors including type of
concrete, accessibility, and operator skill.
In addition to demolishing concrete, many hammers can be fitted
with special tool shapes that allow them to drive piles and
sheeting, compact soil, edge trenches, penetrate frozen ground,
and cut asphalt.
Hammer impact energy is the most important selection criteria when
choosing a mounted breaker for a particular job, since the hammer
must be able to hit the concrete hard enough to fracture it. Only
when impact energy is sufficient does impact rate (blows per
minute) become a factor.
In factoring impact energy, hammer weight is important, but is
sometimes confusing. Some manufacturers report the weight of the
hammer with the boom bracket, surrounding housing (cradle), and
working tool included. Others report just the hammer weight
itself.
This is why comparing tool diameter may be the simplest and most
accurate means of determining the degree of hammer impact energy.
By measuring the tool diameter at the lowest point just inside the
hammer and comparing it to the diameter of other tools, impact
energy may be reliably measured. This is because the tool diameter
is in direct proportion to the piston size.
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Hydraulic Hammer
A hydraulic hammer shouldn’t be chosen
strictly on the basis of the reach, stability, or hydraulic
capacity necessary, but also on the vehicle on which the tool will
be mounted. Keep in mind that for a given reach, the heavier the
hammer, the heavier the carrier vehicle must be. The weight of the
carrier vehicle prevents overturning when the hammer is at the
boom's maximum reach. Selecting a lightweight carrier decreases
the boom's reach and could cause an overturning accident.
Also, remember that while most hydraulic systems run 2000-psi
pressure, the flow rate varies. For the light hammers, as little
as 5 gallons per minute is required. For the heavy hammers, more
than 100 gallons per minute must be supplied. Again, check the
hammer and carrier manufacturers' literature to match the hammer
to the vehicle. If necessary, add-on hydraulic power units are
available to increase the flow rate.
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Pneumatic Hammer
While pneumatic hammers were once considered
state-of-the-art in the United States, they only account for a
small portion of total hammers in use today. There are still a
number of advantages in using pneumatic hammers, however. These
include:
- They can be mounted on lighter carriers, since their
external air compressor negates the extra hydraulic demands
of a hydraulic hammer
- Mounting an air hammer requires only mechanical changes
– no hydraulic connections, systems to service, or
plumbing kits
- Pneumatic hammers work better in confined spaces than
hydraulic hammers due to their high weight-to-power ratio
- Pneumatic hammers are more conducive to underwater use,
having few, if any, seals
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Hydraulic
Concrete Crusher
Hydraulic concrete crushers are used to
demolish concrete methodically and efficiently. Also called
smashers, densifiers, processors, secondary crushers, and
pulverizers, concrete crushers are used to reduce concrete into
smaller easily manageable or recyclable pieces, as well as to
separate steel reinforcement from concrete.
Interchangeable jaws in some crushers, including cracking jaws,
shear jaws and pulverizing jaws, are often used to work along with
various types and configurations of jaw teeth in order to better
fit the crusher to a particular job.
Secondary concrete crushers usually have some type of pulverizing
jaws and are used on jobs where primary demolition is accomplished
by hammers, crushers, blasting, ball and crane, or sawing. In this
instance, the primary demolition work creates large quantities of
concrete rubble which the secondary crusher further reduces,
separating concrete from reinforcement.
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Diamond
Wire Saw
Wire saws were first developed in the stone quarry industry, and
diamond wire saws have been used in concrete demolishing work to
cut reinforced concrete since the early 1980s.
A loop of diamond wire mounted on a flywheel driven by a hydraulic
or electric motor. Hydraulic drives powered by electric, gasoline,
or diesel units are usually preferred on wire saws when cutting
reinforced concrete, since they are both reversible and provide
continuously variable speed. Water is applied to the cut to
provide cooling and to flush the cut.
Diamond wire saws are more efficient than circular saws, able to
cut concrete of almost any thickness. This makes them very useful
for the kind of heavy demolition found in bridges, damns and thick
concrete structures. In addition, they create little dust, noise
and vibration, making them ideal for demolition work within
inhabited structures.
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The Diamond Wire
The real force behind the diamond wire saw is the diamond wire
itself – a steel carrier cable threaded through steel beads to
which diamond is bonded. There are three basic wire types:
- Electroplated beads with compressed steel spring
spacers.
- Impregnated beads with compressed steel spring spacers
- Impregnated beads with injection-molded plastic spacing
There are also two main bonding systems for the diamond beads:
electroplated and impregnated. Electroplating the wire involves
attaching a single layer of diamond to the steel bead. The
impregnated bonding system is more similar to the impregnated
systems on a circular saw in which a powder metal alloy is blended
with diamond, then pressed and sintered to the steel band,
providing multiple layers of diamond for cutting.
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