crane operation manual
TRANSCRIPT
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GATEWAY INDUSTRIAL & PETRO-GAS INSTITUTE, ONI, OGUN WATERSIDE
OGUN STATE
CRANE OPERATION MANUAL
COMPILED
BY
BAMISHAYE B. E.
CRANE
A crane is a type of machine, generally equipped with a hoist, wire ropes or chains,
and sheaves, that can be used both to lift and lower materials and to move them
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horizontally. It is mainly used for lifting heavy things and transporting them to other
places. It uses one or more simple machines to create mechanical advantage and thus
move loads beyond the normal capability of a human. Cranes are commonly employed
in the transport industry for the loading and unloading of freight, in
the construction industry for the movement of materials and in the manufacturing
industry for the assembling of heavy equipment.
The first construction cranes were invented by the Ancient Greeks and were powered
by men or beasts of burden, such as donkeys. These cranes were used for the
construction of tall buildings. Larger cranes were later developed, employing the use of
human tread wheels, permitting the lifting of heavier weights. In the High Middle Ages,
harbour cranes were introduced to load and unload ships and assist with their
construction – some were built into stone towers for extra strength and stability. The
earliest cranes were constructed from wood, but cast iron and steel took over with the
coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals,
although hoists in watermills and windmills could be driven by the harnessed natural
power. The first 'mechanical' power was provided by steam engines, the earliest steam
crane being introduced in the 18th or 19th century, with many remaining in use well into
the late 20th century. Modern cranes usually use internal combustion engines or electric
motors and hydraulic systems to provide a much greater lifting capability than was
previously possible, although manual cranes are still utilised where the provision of
power would be uneconomic.
Cranes exist in an enormous variety of forms – each tailored to a specific use.
Sometimes sizes range from the smallest jib cranes, used inside workshops, to the
tallest tower cranes, used for constructing high buildings. For a while, mini - cranes are
also used for constructing high buildings, in order to facilitate constructions by reaching
tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs
and salvage sunken ships.
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This article also covers lifting machines that do not strictly fit the above definition of a
crane, but are generally known as cranes, such as stacker cranes and loader cranes.
History
Ancient Greece
Greco-Roman Trispastos ("Three-pulley-crane"), the
simplest crane type (150 kg load)
The crane for lifting heavy loads was invented by
the Ancient Greeks in the late 6th century BC. The
archaeological record shows that no later than c.515
BC distinctive cuttings for both lifting tongs and lewis
irons begin to appear on stone blocks of Greek
temples.
Since these holes point at the use of a lifting device, and since they are to be found
either above the center of gravity of the block, or in pairs equidistant from a point over
the center of gravity, they are regarded by archaeologists as the positive evidence
required for the existence of the crane.
The introduction of the winch and pulley hoist soon lead to a widespread replacement
of ramps as the main means of vertical motion. For the next two hundred years, Greek
building sites witnessed a sharp drop in the weights handled, as the new lifting
technique made the use of several smaller stones more practical than of fewer larger
ones. In contrast to the archaic period with its tendency to ever-increasing block sizes,
Greek temples of the classical age like the Parthenon invariably featured stone blocks
weighing less than 15-20 metric tons. Also, the practice of erecting large monolithic
columns was practically abandoned in favour of using several column drums.
Although the exact circumstances of the shift from the ramp to the crane technology
remain unclear, it has been argued that the volatile social and political conditions
of Greece were more suitable to the employment of small, professional construction
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teams than of large bodies of unskilled labour, making the crane more preferable to the
Greek polis than the more labour-intensive ramp which had been the norm in the
autocratic societies of Egypt or Assyria.
The first unequivocal literary evidence for the existence of the compound pulley system
appears in the Mechanical Problems (Mech. 18, 853a32-853b13) attributed
to Aristotle (384–322 BC), but perhaps composed at a slightly later date. Around the
same time, block sizes at Greek temples began to match their archaic predecessors
again, indicating that the more sophisticated compound pulley must have found its way
to Greek construction sites by then.
Ancient Rome
Greco-Roman Pentaspastos ("Five-pulley-crane"), a
medium-sized variant (ca. 450 kg load)
Reconstruction of a 10.4 m high Roman Polyspastos powered by a tread wheel at
Bonn, Germany.
The heyday of the crane in ancient times came during the Roman Empire, when
construction activity soared and buildings reached enormous dimensions. The Romans
adopted the Greek crane and developed it further. We are relatively well informed about
their lifting techniques, thanks to rather lengthy accounts by the engineers Vitruvius (De
Architectura 10.2, 1-10) and Heron of Alexandria (Mechanica 3.2-5). There are also two
surviving reliefs of Roman tread wheel cranes, with the Haterii tombstone from the late
first century AD being particularly detailed.
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The simplest Roman crane, the trispastos, consisted of a single-beam jib, a winch,
a rope, and a block containing three pulleys. Having thus a mechanical advantage of
3:1, it has been calculated that a single man working the winch could raise 150 kg (3
pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can
exert over a longer time period. Heavier crane types featured five pulleys
(pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos)
and came with two, three or four masts, depending on the maximum load.
The polyspastos, when worked by four men at both sides of the winch, could readily lift
3,000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3,000 kg). If the winch was replaced by
a tread wheel, the maximum load could be doubled to 6,000 kg at only half the crew,
since the tread wheel possesses a much bigger mechanical advantage due to its larger
diameter. This meant that, in comparison to the construction of the Egyptian Pyramids,
where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per
person), the lifting capability of the Roman polyspastos proved to be 60 times higher
(3,000 kg per person).
However, numerous extant Roman buildings which feature much heavier stone blocks
than those handled by the polyspastos indicate that the overall lifting capability of the
Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek,
for instance, the architrave blocks weigh up to 60 tons each, and one
corner cornice block even over 100 tons, all of them raised to a height of about 19
m. In Rome, the capital block of Trajan's Column weighs 53.3 tons, which had to be
lifted to a height of about 34 m (see construction of Trajan's Column).
It is assumed that Roman engineers lifted these extraordinary weights by two measures
(see picture below for comparable Renaissance technique): First, as suggested by
Heron, a lifting tower was set up, whose four masts were arranged in the shape of a
quadrangle with parallel sides, not unlike a siege tower, but with the column in the
middle of the structure (Mechanica 3.5). Second, a multitude of capstans were placed
on the ground around the tower, for, although having a lower leverage ratio than tread
wheels, capstans could be set up in higher numbers and run by more men (and,
moreover, by draught animals). This use of multiple capstans is also described
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by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense
obelisk in the Circus Maximus (ca. 357 AD). The maximum lifting capability of a single
capstan can be established by the number of lewis iron holes bored into the monolith. In
case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight
extant holes suggest an allowance of 7.5 ton per lewis iron that is per capstan. Lifting
such heavy weights in a concerted action required a great amount of coordination
between the work groups applying the force to the capstans.
Middle Ages
Medieval port crane for mounting masts and lifting
heavy cargo in the former Hansetown of Gdańsk.
During the High Middle Ages, the tread wheel crane
was reintroduced on a large scale after the technology
had fallen into disuse in Western Europe with the
demise of the Western Roman Empire. The earliest
reference to a tread wheel (magna rota) reappears in archival literature in France about
1225, followed by an illuminated depiction in a manuscript of probably also French
origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented
for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291, while in
England the tread wheel is not recorded before 1331.
Double tread wheel crane in Pieter Bruegel's The Tower of Babel
Generally, vertical transport could be done more safely and inexpensively by cranes
than by customary methods. Typical areas of application were harbors, mines, and, in
particular, building sites where the tread wheel crane played a pivotal role in the
construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial
sources of the time suggest that newly introduced machines like tread wheels or
wheelbarrows did not completely replace more labor-intensive methods
like ladders, hods and handbarrows. Rather, old and new machinery continued to
coexist on medieval construction sites and harbors.
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Apart from tread wheels, medieval depictions also show cranes to be powered manually
by windlasses with radiating spokes, cranks and by the 15th century also by windlasses
shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-
spots' in the lifting process flywheels are known to be in use as early as 1123.
The exact process by which the tread wheel crane was reintroduced is not
recorded, although its return to construction sites has undoubtedly to be viewed in close
connection with the simultaneous rise of Gothic architecture. The reappearance of the
tread wheel crane may have resulted from a technological development of
the windlass from which the tread wheel structurally and mechanically evolved.
Alternatively, the medieval tread wheel may represent a deliberate reinvention of its
Roman counterpart drawn from Vitruvius' De architectura which was available in many
monastic libraries. Its reintroduction may have been inspired, as well, by the observation
of the labor-saving qualities of the waterwheel with which early tread wheels shared
many structural similarities.
Structure and placement
The medieval tread wheel was a large wooden wheel turning around a central shaft with
a tread way wide enough for two workers walking side by side. While the earlier
'compass-arm' wheel had spokes directly driven into the central shaft, the more
advanced 'clasp-arm' type featured arms arranged as chords to the wheel rim, giving
the possibility of using a thinner shaft and providing thus a greater mechanical
advantage.
Contrary to a popularly held belief, cranes on medieval building sites were neither
placed on the extremely lightweight scaffolding used at the time nor on the thin walls of
the Gothic churches which were incapable of supporting the weight of both hoisting
machine and load. Rather, cranes were placed in the initial stages of construction on
the ground, often within the building. When a new floor was completed, and massive tie
beams of the roof connected the walls, the crane was dismantled and reassembled on
the roof beams from where it was moved from bay to bay during construction of the
vaults. Thus, the crane 'grew' and 'wandered' with the building with the result that today
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all extant construction cranes in England are found in church towers above the vaulting
and below the roof, where they remained after building construction for bringing material
for repairs aloft.[20]
Less frequently, medieval illuminations also show cranes mounted on the outside of
walls with the stand of the machine secured to putlogs.
Mechanics and Operation
Tower crane at the inland harbour of Trier from 1413.
In contrast to modern cranes, medieval cranes and
hoists – much like their counterparts in Greece and
Rome – were primarily capable of a vertical lift, and not
used to move loads for a considerable distance
horizontally as well. Accordingly, lifting work was
organized at the workplace in a different way than today. In building construction, for
example, it is assumed that the crane lifted the stone blocks either from the bottom
directly into place, or from a place opposite the centre of the wall from where it could
deliver the blocks for two teams working at each end of the wall. Additionally, the crane
master who usually gave orders at the tread wheel workers from outside the crane was
able to manipulate the movement laterally by a small rope attached to the load. Slewing
cranes which allowed a rotation of the load and were thus particularly suited for
dockside work appeared as early as 1340. While ashlar blocks were directly lifted by
sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in
containers like pallets, baskets, wooden boxes or barrels.
It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the
load from running backward. This curious absence is explained by the high friction
force exercised by medieval tread wheels which normally prevented the wheel from
accelerating beyond control.
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Harbour Usage
Beyond the modern warship stands a crane
constructed in 1742, used for mounting masts to large
sailing vessels. Copenhagen, Denmark.
According to the "present state of knowledge" unknown
in antiquity, stationary harbor cranes are considered a
new development of the Middle Ages. The typical
harbor crane was a pivoting structure equipped with double tread wheels. These cranes
were placed docksides for the loading and unloading of cargo where they replaced or
complemented older lifting methods like see-saws, winches and yards.
Two different types of harbor cranes can be identified with a varying geographical
distribution: While gantry cranes which pivoted on a central vertical axle were commonly
found at the Flemish and Dutch coast side, German sea and inland harbors typically
featured tower cranes where the windlass and tread wheels were situated in a solid
tower with only jib arm and roof rotating. Interestingly, dockside cranes were not
adopted in the Mediterranean region and the highly developed Italian ports where
authorities continued to rely on the more labor-intensive method of unloading goods by
ramps beyond the Middle Ages.
Unlike construction cranes where the work speed was determined by the relatively slow
progress of the masons, harbor cranes usually featured double tread wheels to speed
up loading. The two tread wheels whose diameter is estimated to be 4 m or larger were
attached to each side of the axle and rotated together. Their capacity was 2–3 tons
which apparently corresponded to the customary size of marine cargo. Today,
according to one survey, fifteen tread wheel harbor cranes from pre-industrial times are
still extant throughout Europe. Some harbour cranes were specialised at mounting
masts to newly built sailing ships, such as in Gdańsk, Cologne and Bremen. Beside
these stationary cranes, floating cranes which could be flexibly deployed in the whole
port basin came into use by the 14th century.
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Early Modern Age
Erection of the Vatican obelisk in 1586 by means of a
lifting tower.
A lifting tower similar to that of the ancient Romans was
used to great effect by the Renaissance
architect Domenico Fontana in 1586 to relocate the
361 t heavy Vatican obelisk in Rome. From his report, it becomes obvious that the
coordination of the lift between the various pulling teams required a considerable
amount of concentration and discipline, since, if the force was not applied evenly, the
excessive stress on the ropes would make them rupture.
Cranes were also used domestically during this period. The chimney or fireplace crane
was used to swing pots and kettles over the fire and the height was adjusted by
a trammel.
Industrial Revolution
Sir William Armstrong, inventor of the hydraulic crane.
With the onset of the Industrial Revolution the first modern cranes were installed at
harbours for loading cargo. In 1838, the industrialist and businessman William
Armstrong designed a hydraulic water powered crane. His design used a ram in a
closed cylinder that was forced down by a pressurized fluid entering the cylinder - a
valve regulated the amount of fluid intake relative to the load on the crane.
In 1845 a scheme was set in motion to provide piped water from distant reservoirs to
the households of Newcastle. Armstrong was involved in this scheme and he proposed
to Newcastle Corporation that the excess water pressure in the lower part of town could
be used to power one of his hydraulic cranes for the loading of coal onto barges at
the Quayside. He claimed that his invention would do the job faster and more cheaply
than conventional cranes. The Corporation agreed to his suggestion, and the
experiment proved so successful that three more hydraulic cranes were installed on the
Quayside.
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The success of his hydraulic crane led Armstrong to establish the Elswick
works at Newcastle, to produce his hydraulic machinery for cranes and bridges in 1847.
His company soon received orders for hydraulic cranes from Edinburgh and Northern
Railways and from Liverpool Docks, as well as for hydraulic machinery for dock gates
in Grimsby. The company expanded from a workforce of 300 and an annual production
of 45 cranes in 1850, to almost 4,000 workers producing over 100 cranes per year by
the early 1860s.
Armstrong spent the next few decades constantly improving his crane design; - his most
significant innovation was the hydraulic accumulator. Where water pressure was not
available on site for the use of hydraulic cranes, Armstrong often built high water towers
to provide a supply of water at pressure. However, when supplying cranes for use
at New Holland on the Humber Estuary, he was unable to do this because the
foundations consisted of sand. He eventually produced the hydraulic accumulator, a
cast-iron cylinder fitted with a plunger supporting a very heavy weight. The plunger
would slowly be raised, drawing in water, until the downward force of the weight was
sufficient to force the water below it into pipes at great pressure. This invention allowed
much larger quantities of water to be forced through pipes at a constant pressure, thus
increasing the crane's load capacity considerably.
One of his cranes, commissioned by the Italian Navy in 1883 and in use until the mid-
1950s, is still standing in Venice, where it is now in a state of disrepair.
Mechanical Principles
Broken crane in Sermetal Shipyard,
former Ishikawajima do Brasil - Rio de Janeiro. The
cause of the accident was a lack of maintenance and
misuse of the equipment.
Cranes can mount many different utensils depending
on load (left). Cranes can be remote-controlled from
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the ground, allowing much more precise control, but without the view that a position
atop the crane provides (right).
The stability of a mobile construction crane can be
jeopardized when outriggers sink into soft soil,
which can result in the crane tipping over.
There are three major considerations in the
design of cranes. First, the crane must be able to
lift the weight of the load; second, the crane must
not topple; third, the crane must not rupture.
Lifting Capacity
Cranes illustrate the use of one or more simple machines to create mechanical
advantage.
The lever. A balance crane contains a horizontal beam (the lever) pivoted about a point
called the fulcrum. The principle of the lever allows a heavy load attached to the shorter
end of the beam to be lifted by a smaller force applied in the opposite direction to the
longer end of the beam. The ratio of the load's weight to the applied force is equal to the
ratio of the lengths of the longer arm and the shorter arm, and is called the mechanical
advantage.
The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block.
Cables are wrapped multiple times round the fixed block and round another block
attached to the load. When the free end of the cable is pulled by hand or by a winding
machine, the pulley system delivers a force to the load that is equal to the applied force
multiplied by the number of lengths of cable passing between the two blocks. This
number is the mechanical advantage.
The hydraulic cylinder. This can be used directly to lift the load or indirectly to move
the jib or beam that carries another lifting device.
Cranes, like all machines, obey the principle of conservation of energy. This means that
the energy delivered to the load cannot exceed the energy put into the machine. For
example, if a pulley system multiplies the applied force by ten, then the load moves only
one tenth as far as the applied force. Since energy is proportional to force multiplied by
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distance, the output energy is kept roughly equal to the input energy (in practice slightly
less, because some energy is lost to friction and other inefficiencies).
The same principle can operate in reverse. In case of some problem, the combination of
heavy load and great height can accelerate small objects to tremendous speed
(see trebuchet). Such projectiles can result in severe damage to nearby structures and
people. Cranes can also get in chain reactions; the rupture of one crane may in turn
take out nearby cranes. Cranes need to be watched carefully.
Stability
For stability, the sum of all moments about the base of the crane must be close to zero
so that the crane does not overturn. In practice, the magnitude of load that is permitted
to be lifted (called the "rated load" in the US) is some value less than the load that will
cause the crane to tip, thus providing a safety margin.
Under US standards for mobile cranes, the stability-limited rated load for a crawler
crane is 75% of the tipping load. The stability-limited rated load for a mobile crane
supported on outriggers is 85% of the tipping load. These requirements, along with
additional safety-related aspects of crane design, are established by the American
Society of Mechanical Engineers in the volume ASME B30.5-2010 Mobile and
Locomotive Cranes.
Standards for cranes mounted on ships or offshore platforms are somewhat stricter
because of the dynamic load on the crane due to vessel motion. Additionally, the
stability of the vessel or platform must be considered.
For stationary pedestal or kingpost mounted cranes, the moment created by the boom,
jib, and load is resisted by the pedestal base or kingpost. Stress within the base must
be less than the yield stress of the material or the crane will fail.
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Types of Cranes
Overhead Crane
Overhead crane being used in typical machine shop.
The hoist is operated via a wired pushbutton station to
move system and the load in any direction.
An overhead crane, also known as a bridge crane, is a
type of crane where the hook-and-line mechanism runs
along a horizontal beam that itself runs along two widely
separated rails. Often it is in a long factory building and
runs along rails along the building's two long walls. It is
similar to a gantry crane. Overhead cranes typically
consist of either a single beam or a double beam construction. These can be built using
typical steel beams or a more complex box girder type. Pictured on the right is a single
bridge box girder crane with the hoist and system operated with a control pendant.
Double girder bridge are more typical when needing heavier capacity systems from 10
tons and above. The advantage of the box girder type configuration results in a system
that has a lower deadweight yet a stronger overall system integrity. Also included would
be a hoist to lift the items, the bridge, which spans the area covered by the crane, and a
trolley to move along the bridge.
The most common overhead crane use is in the steel industry. At every step of the
manufacturing process, until it leaves a factory as a finished product, steel is handled by
an overhead crane. Raw materials are poured into a furnace by crane, hot steel is
stored for cooling by an overhead crane, the finished coils are lifted and loaded
onto trucks and trains by overhead crane, and the fabricator or stamper uses an
overhead crane to handle the steel in his factory. The automobile industry uses
overhead cranes for handling of raw materials. Smaller workstation cranes handle
lighter loads in a work-area, such as CNCmill or saw.
Almost all paper mills use bridge cranes for regular maintenance requiring removal of
heavy press rolls and other equipment. The bridge cranes are used in the initial
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construction of paper machines because they facilitate installation of the heavy cast iron
paper drying drums and other massive equipment, some weighing as much as 70 tons.
In many instances the cost of a bridge crane can be largely offset with savings from not
renting mobile cranes in the construction of a facility that uses a lot of heavy process
equipment.
Mobile Crane
The most basic type of mobile crane consists of a truss or telescopic boom mounted on
a mobile platform - be it on road, rail or water. Common terminology is conventional and
hydraulic cranes respectively.
Truck-mounted Crane
Developed truck-mounted crane at work
Truck-mounted crane
A crane mounted on a truck carrier provides the mobility for
this type of crane. This crane has two parts: the carrier,
often referred to as the Lower, and the lifting component which includes the boom,
referred to as the Upper. These are mated together through a turntable, allowing the
upper to swing from side to side. These modern hydraulic truck cranes are usually
single-engine machines, with the same engine powering the undercarriage and the
crane. The upper is usually powered via hydraulics run through the turntable from the
pump mounted on the lower. In older model designs of hydraulic truck cranes, there
were two engines. One in the lower pulled the crane down the road and ran a hydraulic
pump for the outriggers and jacks. The one in the upper ran the upper through a
hydraulic pump of its own. Many older operators favor the two-engine system due to
leaking seals in the turntable of aging newer design cranes.
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Generally, these cranes are able to travel on highways, eliminating the need for special
equipment to transport the crane unless weight or other size constrictions are in place
such as local laws. If this is the case, most larger cranes are equipped with either
special trailers to help spread the load over more axles or are able to disassemble to
meet requirements. An example is counterweights. Often a crane will be followed by
another truck hauling the counterweights that are removed for travel. In addition some
cranes are able to remove the entire upper. However, this is usually only an issue in a
large crane and mostly done with a conventional crane such as a Link-Belt HC-238.
When working on the job site, outriggers are extended horizontally from the chassis
then vertically to level and stabilize the crane while stationary and hoisting. Many truck
cranes have slow-travelling capability (a few miles per hour) while suspending a load.
Great care must be taken not to swing the load sideways from the direction of travel, as
most anti-tipping stability then lies in the stiffness of the chassis suspension. Most
cranes of this type also have moving counterweights for stabilization beyond that
provided by the outriggers. Loads suspended directly aft are the most stable, since most
of the weight of the crane acts as a counterweight. Factory-calculated charts (or
electronic safeguards) are used by crane operators to determine the maximum safe
loads for stationary (outriggered) work as well as (on-rubber) loads and travelling
speeds.
Truck cranes range in lifting capacity from about 14.5 short tons (12.9 long tons; 13.2 t)
to about 1,300 short tons (1,161 long tons; 1,179 t). Although most only rotate about
180 degrees, the more expensive truck mounted cranes can turn a full 360 degrees.
Side-lift Crane
A sidelifter crane is a road-going truck or semi-trailer, able to hoist and transport ISO
standard containers. Container lift is done with parallel crane-like hoists, which can lift a
container from the ground or from a railway vehicle.
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Rough Terrain Crane
A crane mounted on an undercarriage with four rubber tires that is designed for pick-
and-carry operations and for off-road and "rough terrain" applications. Outriggers are
used to level and stabilize the crane for hoisting.
These telescopic cranes are
single-engine machines, with the
same engine powering the
undercarriage and the crane,
similar to a crawler crane. In a
rough terrain crane, the engine is
usually mounted in the undercarriage rather than in the upper, as with crawler crane.
Most have 4 wheel drive and 4 wheel steering which allows them to traverse tighter and
slicker terrain than a standard truck crane with less site prep. In addition, there are
rough terrain cranes with the operating cab mounted on the lower as opposed to the
P&H in the above image.
All Terrain Crane
A mobile crane with the necessary
equipment to travel at speed on public
roads, and on rough terrain at the job
site using all-wheel and crab steering.
AT‘s combine the roadability of Truck-
mounted Cranes and the
manoeuvrability of Rough Terrain
Cranes.
AT’s have 2-9 axles and are designed
for lifting loads up to 1,200 tonnes (1,323 short tons; 1,181 long tons).
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Pick and carry crane
A Pick and Carry Crane is similar to a mobile crane in that is designed to travel on
public roads, however Pick and Carry cranes have no stabiliser legs or outriggers and
are designed to lift the load and carry it to its destination, within a small radius, then be
able to drive to the next job. Pick and Carry cranes are popular in Australia where large
distances are encountered between job sites. One popular manufacturer in Australia
was Franna, who have since been bought by Terex, and now all pick and carry cranes
are commonly referred to as "Frannas" even though they may be made by other
manufacturers. Nearly every medium and large sized crane company in Australia has at
least one and many companies have fleets of these cranes. The capacity range is
usually ten to twenty tonnes maximum lift, although this is much less at the tip of the
boom. Pick and Carry cranes have displaced the work usually completed by smaller
truck cranes as the set up time is much quicker. Many steel fabrication yards also use
pick and carry cranes as they can "walk" with fabricated steel sections and place these
where required with relative ease.
Carry Deck Crane
A carry deck crane is a small 4 wheel crane with a 360 degree rotating boom placed
right in the centre and an operators cab located at one end under this boom. The rear
section houses the engine and the area above the wheels is a flat deck. Very much an
American invention the Carry deck can hoist a load in a confined space and then load it
on the deck space around the cab or engine and subsequently move to another site.
The Carry Deck principle is the American version of the pick and carry crane and both
allow the load to be moved by the crane over short distances.
Telescopic Handler Crane
Telescopic Handlers are like forklift trucks that have a telescoping extendable boom like
a crane. Early telescopic handlers only lifted in one direction and did not
rotate, however, several of the manufacturers have designed telescopic handlers that
rotate 360 degrees through a turntable and these machines look almost identical to the
Rough Terrain Crane. These new 360 degree telescopic handler/crane models have
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outriggers or stabiliser legs that must be lowered before lifting, however their design has
been simplified so that they can be more quickly deployed. These machines are often
used to handle pallets of bricks and install frame trusses on many new building sites
and they have eroded much of the work for small telescopic truck cranes. Many of the
worlds Armed forces have purchased telescopic handlers and some of these are the
much more expensive fully rotating types. Their off road capability and their onsite
versatility to unload pallets using forks, or lift like a crane makes them a valuable piece
of machinery.
Crawler Crane
A crawler is a crane mounted on an
undercarriage with a set of tracks (also called
crawlers) that provide stability and mobility.
Crawler cranes range in lifting capacity from
about 40 to 3,500 short tons (35.7 to 3,125.0
long tons; 36.3 to 3,175.1 t).
Crawler cranes have both advantages and
disadvantages depending on their use. Their main advantage is that they can move
around on site and perform each lift with little set-up, since the crane is stable on its
tracks with no outriggers. In addition, a crawler crane is capable of traveling with a load.
The main disadvantage is that they are very heavy, and cannot easily be moved from
one job site to another without significant expense. Typically a large crawler must be
disassembled and moved by trucks, rail cars or ships to its next location.
Railroad Crane
A railroad crane has flanged wheels for use on railroads.
The simplest form is a crane mounted on a flatcar. More
capable devices are purpose-built. Different types of crane
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are used for maintenance work, recovery operations and freight loading in goods yards
and scrap handling facilities.
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Floating Crane
Floating cranes are used mainly in bridge building and port construction, but they are
also used for occasional loading and unloading of especially heavy or awkward loads on
and off ships. Some floating cranes are mounted on a pontoon, others are specialized
crane barges with a lifting capacity exceeding 10,000 short tons (8,929 long tons;
9,072 t) and have been used to transport entire bridge sections. Floating cranes have
also been used to salvage sunken ships.
Crane vessels are often used in offshore construction. The largest revolving cranes can
be found on SSCV Thialf, which has two cranes with a capacity of
7,100 tonnes (7,826 short tons; 6,988 long tons) each. For fifty years, the largest such
crane was "Herman the German" at the Long Beach Naval Shipyard, one of three
constructed by Hitler's Germany and captured in the war. The crane was sold to the
Panama Canal in 1996 where it is now known as the "Titan."
Aerial Crane
Aerial crane or 'Sky cranes' usually
are helicopters designed to lift large loads. Helicopters are
able to travel to and lift in areas that are difficult to reach
by conventional cranes. Helicopter cranes are most
commonly used to lift units/loads onto shopping centers
and highrises. They can lift anything within their lifting capacity, (cars, boats, swimming
pools, etc.). They also perform disaster relief after natural disasters for clean-up, and
during wild-fires they are able to carry huge buckets of water to extinguish fires.
Some aerial cranes, mostly concepts, have also used lighter-than air aircraft, such as airships.
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Fixed
Exchanging mobility for the ability to carry greater loads and reach greater heights due
to increased stability, these types of cranes are characterised by the fact that their main
structure does not move during the period of use. However, many can still be
assembled and disassembled.
Tower Crane
Tower crane atop Mont Blanc
Tower cranes are a modern form of balance crane that
consist of the same basic parts. Fixed to the ground on a
concrete slab (and sometimes attached to the sides of
structures as well), tower cranes often give the best
combination of height and lifting capacity and are used in
the construction of tall buildings. The base is then
attached to the mast which gives the crane its height.
Further the mast is attached to the slewing unit (gear and
motor) that allows the crane to rotate. On top of the
slewing unit there are three main parts which are: the long horizontal jib (working arm),
shorter counter-jib, and the operator's cab.
Tower crane cabin
The long horizontal jib is the part of the crane that carries
the load. The counter-jib carries a counterweight, usually
of concrete blocks, while the jib suspends the load to and
from the center of the crane. The crane operator either
sits in a cab at the top of the tower or controls the crane
by radio remote control from the ground. In the first case the operator's cab is most
usually located at the top of the tower attached to the turntable, but can be mounted on
the jib, or partway down the tower. The lifting hook is operated by the crane operator
using electric motors to manipulate wire rope cables through a system of sheaves. The
hook is located on the long horizontal arm to lift the load which also contains its motor.
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A tower crane rotates on its axis before lowering the
lifting hook.
In order to hook and unhook the loads, the operator
usually works in conjunction with a signaller (known as a
'dogger', 'rigger' or 'swamper'). They are most often in
radio contact, and always use hand signals. The rigger or
dogger directs the schedule of lifts for the crane, and is responsible for the safety of the
rigging and loads.
COMPONENTS
Tower Cranes are used extensively in construction and other industry to hoist and move
materials. There are many types of tower cranes. Although they are different in type, the
main parts are the same, as follows:
Mast: the main supporting tower of the crane. It is made of steel trussed sections that
are connected together during installation.
Slewing Unit: the slewing unit sits at the top of the mast. This is the engine that
enables the crane to rotate.
Operating Cabin: the operating cabin sits just above the slewing unit. It contains the
operating controls.
Jib: the jib, or operating arm, extends horizontally from the crane. A "luffing" jib is able
to move up and down; a fixed jib has a rolling trolley that runs along the underside to
move goods horizontally.
Hook: the hook (or hooks) is used to connect the material to the crane. It hangs at the
end of thick steel cables that run along the jib to the motor.
Weights: Large concrete counterweights are mounted toward the rear of the mast, to
compensate for the weight of the goods lifted.
A tower crane is usually assembled by a telescopic jib (mobile) crane of greater reach
(also see "self-erecting crane" below) and in the case of tower cranes that have risen
while constructing very tall skyscrapers, a smaller crane (or derrick) will often be lifted to
the roof of the completed tower to dismantle the tower crane afterwards, which may be
more difficult than the installation.[42]
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Self-Erecting Crane
Four self-erecting tower cranes mounted on the roof of 1st
observatory (height 375 m) of Tokyo Skytree(Tower tip and two
craneoperator as of 497 m)
Generally a type of tower crane, these cranes, also called self-
assembling, jack-up, or "kangaroo" cranes, lift themselves from
the ground or lift an upper, telescoping section using jacks,
allowing the next section of the tower to be inserted at ground
level or lifted into place by the partially erected crane itself. They
can thus be assembled without outside help, and can grow
together with the building or structure they are erecting.
Self-Erecting Crane
(Here, the crane is used to erect a scaffold which in
turn contains a gantry to lift sections of a bridge spire.)
Telescopic Crane
A telescopic crane has
a boom that consists
of a number of tubes
fitted one inside the
other. A hydraulic or other powered mechanism
extends or retracts the tubes to increase or
decrease the total length of the boom. These types
of booms are often used for short term construction
projects, rescue jobs, lifting boats in and out of the
water, etc. The relative compactness of
telescopic booms make them adaptable for many mobile applications.
Though not all telescopic cranes are mobile cranes, many of them are truck-mounted.
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A telescopic tower crane has a telescopic mast and a superstructure (jib) on top so that
it functions as a tower crane. Some telescopic tower cranes also have a telescopic jib.
Hammerhead Crane
The "hammerhead", or giant cantilever, crane is a fixed-
jib crane consisting of a steel-braced tower on which
revolves a large, horizontal, double cantilever; the forward
part of this cantilever or jib carries the lifting trolley, the jib
is extended backwards in order to form a support for the
machinery and counterbalancing weight. In addition to the
motions of lifting and revolving, there is provided a so-called "racking" motion, by which
the lifting trolley, with the load suspended, can be moved in and out along the jib without
altering the level of the load. Such horizontal movement of the load is a marked feature
of later crane design. These cranes are generally constructed in large sizes and can
weigh up to 350 tons.
The design of hammerkran evolved first in Germany around the turn of the 19th century
and was adopted and developed for use in British shipyards to support the battleship
construction program from 1904 to 1914. The ability of the hammerhead crane to lift
heavy weights was useful for installing large pieces of battleships such as armour
plate and gun barrels. Giant cantilever cranes were also installed in naval shipyards
in Japan and in the United States. The British government also installed a giant
cantilever crane at the Singapore Naval Base (1938) and later a copy of the crane was
installed at Garden Island Naval Dockyard in Sydney (1951). These cranes provided
repair support for the battle fleet operating far from Great Britain.
In the British Empire, the engineering firm Sir William Arrol & Co Ltd was the principal
manufacturer of giant cantilever cranes; the company built a total of fourteen. Among
the sixty built in the world, few remain; seven in England and Scotland of about fifteen
worldwide.
The Titan Clydebank is one of the 4 Scottish cranes on the Clydebank and preserved as
a tourist attraction.
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Level Luffing Crane
Normally a crane with a hinged jib will tend to have its
hook also move up and down as the jib moves (or luffs).
A level luffing crane is a crane of this common design, but
with an extra mechanism to keep the hook level when
luffing.
Gantry Crane
A gantry crane has a hoist in
a fixed machinery house or
on a trolley that runs
horizontally along rails, usually fitted on a single beam (mono-girder) or two beams
(twin-girder). The crane frame is supported on a gantry system with equalized beams
and wheels that run on the gantry rail, usually perpendicular to the trolley travel
direction. These cranes come in all sizes, and some can move very heavy loads,
particularly the extremely large examples used in shipyards or industrial installations. A
special version is the container crane (or "Portainer" crane, named by the first
manufacturer), designed for loading and unloading ship-borne containers at a port.
Most container cranes are of this type.
Deck Crane
Located on the ships and boats, these are used for cargo
operations or boat unloading and retrieval where no shore
unloading facilities are available. Most are diesel-hydraulic
or electric-hydraulic.
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Jib Crane
A jib crane is a type of crane where a horizontal member
(jib or boom), supporting a moveable hoist, is fixed to a
wall or to a floor-mounted pillar. Jib cranes are used in
industrial premises and on military vehicles. The jib may
swing through an arc, to give additional lateral movement,
or be fixed. Similar cranes, often known simply as hoists,
were fitted on the top floor of warehouse buildings to
enable goods to be lifted to all floors.
Bulk-Handling Crane
Bulk-handling cranes are designed from the outset to
carry a shell grab or bucket, rather than using a hook and
a sling. They are used for bulk cargoes, such as coal,
minerals, scrap metal etc.
Loader Crane
Loader crane using a fly jib extension
A loader crane (also called a knuckle-boom
crane or articulating crane) is a hydraulically powered
articulated arm fitted to a truck or trailer, and is used for
loading/unloading the vehicle. The numerous jointed
sections can be folded into a small space when the crane
is not in use. One or more of the sections may be telescopic. Often the crane will have a
degree of automation and be able to unload or stow itself without an operator's
instruction.
Unlike most cranes, the operator must move around the vehicle to be able to view his
load; hence modern cranes may be fitted with a portable cabled or radio-linked control
system to supplement the crane-mounted hydraulic control levers.
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In the UK and Canada, this type of crane is often known colloquially as a "Hiab", partly
because this manufacturer invented the loader crane and was first into the UK market,
and partly because the distinctive name was displayed prominently on the boom arm.
A rolloader crane is a loader crane mounted on a chassis with wheels. This chassis
can ride on the trailer. Because the crane can move on the trailer, it can be a light
crane, so the trailer is allowed to transport more goods.
Stacker Crane
A crane with a forklift type mechanism used in automated (computer
controlled) warehouses (known as an automated storage and retrieval system (AS/RS)).
The crane moves on a track in an aisle of the warehouse. The fork can be raised or
lowered to any of the levels of a storage rack and can be extended into the rack to store
and retrieve product. The product can in some cases be as large as an automobile.
Stacker cranes are often used in the large freezer warehouses of frozen food
manufacturers. This automation avoids requiring forklift drivers to work in below freezing
temperatures every day.
Similar Machines
Shooting a film from crane
The generally accepted definition of a crane is a machine for
lifting and moving heavy objects by means of ropes or cables
suspended from a movable arm. As such, a lifting machine that
does not use cables, or else provides only vertical and not
horizontal movement, cannot strictly be called a 'crane'.
Types of crane-like lifting machine include:
Block and tackle
Capstan (nautical)
Hoist (device)
Winch
Windlass
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Cherry Picker
More technically advanced types of such lifting machines are often known as 'cranes',
regardless of the official definition of the term.
TYPES OF MODERN CRANES
Mounted Crane
A crane mounted on a truck carrier provides the
mobility for this type of crane. Generally, these
cranes are able to travel on highways, eliminating the
need for special equipment to transport the crane.
When working on the jobsite, outriggers are extended
horizontally from the chassis then vertically to level
and stabilize the crane while stationary and hoisting. Many truck cranes have slow-
travelling capability (a few miles per hour) while suspending a load. Great care must be
taken not to swing the load sideways from the direction of travel, as most anti-tipping
stability then lies in the stiffness of the chassis suspension. Most cranes of this type also
have moving counterweights for stabilization beyond that provided by the outriggers.
Loads suspended directly aft are the most stable, since most of the weight of the crane
acts as a counterweight. Factory-calculated charts (or electronic safeguards) are used
by crane operators to determine the maximum safe loads for stationary (outriggered)
work as well as (on-rubber) loads and travelling speeds.
Truck cranes range in lifting capacity from about 14.5 US tons to about 1300 US tons.
Rough Terrain Crane
A crane mounted on an undercarriage with four
rubber tires that is designed for pick-and-carry
operations and for off-road and “rough terrain”
applications. Outriggers are used to level and
stabilize the crane for hoisting.
These telescopic cranes are single-engine machines, with the same engine powering
the undercarriage and the crane, similar to a crawler crane. In a rough terrain crane, the
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engine is usually mounted in the undercarriage rather than in the upper, as with crawler
crane.
Side-lift Crane
A side lifter crane is a road-going truck or semi-
trailer, able to hoist and transport ISO standard
containers. Container lift is done with parallel crane-
like hoists, which can lift a container from the ground
or from a railway vehicle.
All Terrain Crane
A mobile crane with the necessary equipment to
travel at speed on public roads, and on rough terrain
at the job site using all-wheel and crab steering. AT‘s
combine the road ability of Truck-mounted Cranes
and the maneuverability of Rough Terrain Cranes.
AT’s have 2-9 axles and are designed for lifting loads
up to 1200 metric tons.
Crawler Crane
Crawler is a crane mounted on an undercarriage with
a set of tracks (also called crawlers) that provide stability and mobility. Crawler cranes
range in lifting capacity from about 40 US tons to 3500 US tons.
Crawler cranes have both advantages and disadvantages depending on their use. Their
main advantage is that they can move around on site and perform each lift with little
setup, since the crane is stable on its tracks with no outriggers. In addition, a crawler
crane is capable of traveling with a load. The main disadvantage is that they are very
heavy, and cannot easily be moved from one job site to another without significant
expense. Typically a large crawler must be disassembled and moved by trucks, rail cars
or ships to its next location.
Floating Crane
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Floating cranes are used mainly in bridge building and port construction, but they are
also used for occasional loading and unloading of especially heavy or awkward loads on
and off ships. Some floating cranes are mounted on a pontoon, others are specialized
crane barges with a lifting capacity exceeding 10,000 tons and have been used to
transport entire bridge sections. Floating cranes have also been used to salvage sunken
ships.
Crane vessels are often used in offshore construction. The largest revolving cranes can
be found on SSCV Thialf, which has two cranes with a capacity of 7,100 metric tons
each.
Railroad Crane
A railroad crane has flanged wheels for use on
railroads. The simplest form is a crane mounted on a
railroad car. More capable devices are purpose-built.
Different types of crane are used for maintenance
work, recovery operations and freight loading in
goods yards.
Tower Crane
The tower crane is a modern form of balance crane.
Fixed to the ground (and sometimes attached to the
sides of structures as well), tower cranes often give
the best combination of height and lifting capacity and are used in the construction of
tall buildings.
The jib (colloquially, the ‘boom’) and counter-jib are mounted to the turntable, where the
slewing bearing and slewing machinery are located. The counter-jib carries a
counterweight, usually of concrete blocks, while the jib suspends the load from the
trolley. The Hoist motor and transmissions are located on the mechanical deck on the
counter-jib, while the trolley motor is located on the jib. The crane operator either sits in
a cabin at the top of the tower or controls the crane by radio remote control from the
ground. In the first case the operator’s cabin is most usually located at the top of the
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tower attached to the turntable, but can be mounted on the jib, or partway down the
tower. The lifting hook is operated by using electric motors to manipulate wire rope
cables through a system of sheaves.
In order to hook and unhook the loads, the operator usually works in conjunction with a
signaller (known as a ‘rigger’ or ‘swamper’). They are most often in radio contact, and
always use hand signals. The rigger directs the schedule of lifts for the crane, and is
responsible for the safety of the rigging and loads.
A tower crane is usually assembled by a telescopic jib (mobile) crane of greater reach
(also see “self-erecting crane” below) and in the case of tower cranes that have risen
while constructing very tall skyscrapers, a smaller crane (or derrick) will often be lifted to
the roof of the completed tower to dismantle the tower crane afterwards.
It is often claimed that a large fraction of the tower cranes in the world are in use in
Dubai. The exact percentage remains an open question.
Aerial Crane
Aerial crane or ‘Sky cranes’ usually are helicopters
designed to lift large loads. Helicopters are able to
travel to and lift in areas that are difficult to reach by
conventional cranes. Helicopter cranes are most
commonly used to lift units/loads onto shopping
centers and high-rises. They can lift anything within their lifting capacity, (cars, boats,
swimming pools, etc.). They also perform disaster relief after natural disasters for clean-
up, and during wild-fires they are able to carry huge buckets of water to extinguish fires.
Some aerial cranes, mostly concepts, have also used lighter-than air aircraft, such as
airships.
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Self-erecting Crane
Generally a type of tower crane, these cranes, also
called self-assembling or “Kangaroo” cranes, lift
themselves off the ground using jacks, allowing the
next section of the tower to be inserted at ground
level or lifted into place by the partially erected crane
itself. They can thus be assembled without outside
help, or can grow together with the building or
structure they are erecting.
Telescopic Crane
A telescopic crane has a boom that consists of a
number of tubes fitted one inside the other. A
hydraulic or other powered mechanism extends or
retracts the tubes to increase or decrease the total length of the boom. These types of
booms are often used for short term construction projects, rescue jobs, lifting boats in
and out of the water, etc. The relative compactness of telescopic booms make them
adaptable for many mobile applications.
Note that while telescopic cranes are not automatically mobile cranes, many of them
are. These are often truck-mounted.
Level Luffing Crane
Normally a crane with a hinged jib will tend to have its hook also move up and down as
the jib moves (or luffs). A level luffing crane is a crane of this common design, but with
an extra mechanism to keep the hook level when luffing.
Types of Cranes
Hammerhead Crane
The “hammerhead”, or giant cantilever, crane is a
fixed-jib crane consisting of a steel-braced tower on
which revolves a large, horizontal, double cantilever;
the forward part of this cantilever or jib carries the
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lifting trolley, the jib is extended backwards in order to form a support for the machinery
and counterbalancing weight. In addition to the motions of lifting and revolving, there is
provided a so-called “racking” motion, by which the lifting trolley, with the load
suspended, can be moved in and out along the jib without altering the level of the load.
Such horizontal movement of the load is a marked feature of later crane design. These
cranes are generally constructed in large sizes, up to 350 tons.
The design of hammerkran evolved first in Germany around the turn of the 19th century
and was adopted and developed for use in British shipyards to support the battleship
construction program from 1904-1914. The ability of the hammerhead crane to lift heavy
weights was useful for installing large pieces of battleships such as armour plate and
gun barrels. Giant cantilever cranes were also installed in naval shipyards in Japan and
in the USA. The British Government also installed a giant cantilever crane at the
Singapore Naval Base (1938) and later a copy of the crane was installed at Garden
Island Naval Dockyard in Sydney (1951). These cranes provided repair support for the
battle fleet operating far from Great Britain.
Gantry Crane
A gantry crane has a hoist in a fixed machinery
house or on a trolley that runs horizontally along
rails, usually fitted on a single beam (mono-girder) or
two beams (twin-girder). The crane frame is
supported on a gantry system with equalized beams
and wheels that run on the gantry rail, usually perpendicular to the trolley travel
direction. These cranes come in all sizes, and some can move very heavy loads,
particularly the extremely large examples used in shipyards or industrial installations. A
special version is the container crane (or “Portainer” crane, named by the first
manufacturer), designed for loading and unloading ship-borne containers at a port.
Overhead Crane
Also known as a ‘suspended crane’, this type of crane work very similar to a gantry
crane but instead of the whole crane moving, only the hoist / trolley assembly moves in
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one direction along one or two fixed beams, often mounted along the side walls or on
elevated columns in the assembly area of factory. Some of these cranes can lift very
heavy loads.
Deck Crane
Located on the ships and boats, these are used for cargo operations or boat unloading
and retrieval where no shore unloading facilities are available. Most are diesel-hydraulic
or electric-hydraulic.
Loader Crane
A loader crane (also called a knuckle-boom crane or articulating crane) is a
hydraulically-powered articulated arm fitted to a truck or trailer, and is used for
loading/unloading the vehicle. The numerous jointed sections can be folded into a small
space when the crane is not in use. One or more of the sections may be telescopic.
Often the crane will have a degree of automation and be able to unload or stow itself
without an operator’s instruction.
Unlike most cranes, the operator must move around the vehicle to be able to view his
load; hence modern cranes may be fitted with a portable cabled or radio-linked control
system to supplement the crane-mounted hydraulic control levers. In the UK and
Canada, this type of crane is almost invariably known colloquially as a “Hiab”, partly
because this manufacturer invented the loader crane and was first into the UK market,
and partly because the distinctive name was displayed prominently on the boom arm.
A rolloader crane is a loader crane mounted on a chassis with wheels. This chassis can
ride on the trailer. Because the crane can move on the trailer, it can be a light crane, so
the trailer is allowed to transport more goods.
Bulk-Handling Crane
Bulk-handling cranes are designed from the outset to carry a shell grab or bucket, rather
than using a hook and a sling. They are used for bulk cargoes, such as coal, minerals,
scrap metal etc.
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Jib Crane
A jib crane is a type of crane where a horizontal member (jib or boom), supporting a
moveable hoist, is fixed to a wall or to a floor-mounted pillar. Jib cranes are used in
industrial premises and on military vehicles. The jib may swing through an arc, to give
additional lateral movement, or be fixed. Similar cranes, often known simply as hoists,
were fitted on the top floor of warehouse buildings to enable goods to be lifted to all
floors.
Stacker Crane
A crane with a forklift type mechanism used in
automated computer controlled) warehouses (known
as an) automated storage and retrieval system
(AS/RS)). The crane moves on a track in an aisle of
the warehouse. The fork can be raised or lowered to
any of the levels of a storage rack and can be
extended into the rack to store and retrieve product.
The product can in some cases be as large as an
automobile. Stacker cranes are often used in the large freezer warehouses of frozen
food manufacturers. This automation avoids requiring forklift drivers to work in below
freezing temperatures every day.
CRANE MACHINE SLEWING PLATFORM
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ROPE
A rope is a linear collection of natural or
artificial plies, yarns or strands which are twisted
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or braided together in order to combine them into a larger and stronger form, but is not
a cable or wire. Ropes have tensile strength and so can be used for dragging and lifting,
but are far too flexible to provide compressive strength. As a result, they cannot be used
for pushing or similar compressive applications. Rope is thicker and stronger than
similarly constructed cord, line, string, and twine.
Construction
Rope may be constructed of any long, stringy, fibrous material, but generally is
constructed of certain natural or synthetic fibres. Synthetic fibre ropes are significantly
stronger than their natural fibre counterparts, but also possess certain disadvantages,
including slipperiness.
Common natural fibres for rope are manila hemp, hemp, linen, cotton, coir, jute, straw,
and sisal. Synthetic fibres in use for rope-making
includepolypropylene, nylon, polyesters (e.g. PET, LCP, HDPE, Vectran), polyethylene (
e.g. Dyneema and Spectra), Aramids (e.g. Twaron, Technoraand Kevlar)
and acrylics (e.g. Dralon). Some ropes are constructed of mixtures of several fibres or
use co-polymer fibres. Rope can also be made out of metal. Ropes have been
constructed of other fibrous materials such as silk, wool, and hair, but such ropes are
not generally available.Rayon is a regenerated fibre used to make decorative rope.
The twist of the strands in a twisted or braided rope serves not only to keep a rope
together, but enables the rope to more evenly distribute tension among the individual
strands. Without any twist in the rope, the shortest strand(s) would always be supporting
a much higher proportion of the total load.
Usage
Rope is of paramount importance in fields as diverse as construction, seafaring,
exploration, sports, hangings, theatre, and communications; and has been used
since prehistoric times. In order to fasten rope, a large number of knots have been
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invented for countless uses. Pulleys are used to redirect the pulling force to another
direction, and may be used to create mechanical advantage, allowing multiple strands
of rope to share a load and multiply the force applied to the
end. Winches and capstans are machines designed to pull ropes.
Wire rope
Wire rope, or cable, is a type of rope which consists of several strands of
metal wire laid (or 'twisted') into a helix. Initially wrought iron wires were used, but
today steel is the main material used for wire ropes.
Historically wire rope evolved from steel chains which had a record of mechanical
failure. While flaws in chain links or solid steel bars can lead to catastrophic failure,
flaws in the wires making up a steel cable are less critical as the other wires easily take
up the load. Friction between the individual wires and strands, as a consequence of
their twist, further compensates for any flaws.
History
odern wire rope was invented by the
German mining engineer Wilhelm Albert in the years
between 1831 and 1834 for use in mining in
the Harz Mountains in Clausthal, Lower
Saxony, Germany. It was quickly accepted because it
proved superior to ropes made of hemp or to
metal chains, such as had been used before.
Wilhelm Albert's first ropes consisted of three strands
consisting of four wires each.
In 1840, Scotsman Robert Stirling Newall improved the process further.
In the last half of the 19th century, wire rope systems were used as a means of
transmitting mechanical power including for the new cable cars. Wire rope systems cost
one-tenth as much and had lower friction losses than line shafts. Because of these
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advantages, wire rope systems were used to transmit power for a distance of a few
miles or kilometers.
In America wire rope was later manufactured by John A. Roebling, forming the basis for
his success in suspension bridge building. Roebling introduced a number of innovations
in the design, materials and manufacture of wire rope.
Wire Rope Construction
Wires
Steel wires for wire ropes are normally made of non-alloy carbon steel with a carbon
content of 0.4 to 0.95%. The tensile forces and to run over sheaves with relatively small
diameters.
Strands
In the so-called cross lay strands, the wires of the different layers cross each other. In
the mostly used parallel lay strands, the lay length of all the wire layers is equal and the
wires of any two superimposed layers are parallel, resulting in linear contact. The wire
of the outer layer is supported by two wires of the inner layer. These wires are
neighbours along the whole length of the strand. Parallel lay strands are made in one
operation. The endurance of wire ropes with this kind of strand is always much greater
than of those (seldom used) with cross lay strands. Parallel lay strands with two wire
layers have the construction Filler, Seale or Warrington.
Spiral Ropes
In principle, spiral ropes are round strands as they have an assembly of layers of wires
laid helically over a centre with at least one layer of wires being laid in the opposite
direction to that of the outer layer. Spiral ropes can be dimensioned in such a way that
they are non-rotating which means that under tension the rope torque is nearly zero.
The open spiral rope consists only of round wires. The half-locked coil rope and the full-
locked coil rope always have a centre made of round wires. The locked coil ropes have
one or more outer layers of profile wires. They have the advantage that their
construction prevents the penetration of dirt and water to a greater extent and it also
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protects them from loss of lubricant. In addition, they have one further very important
advantage as the ends of a broken outer wire cannot leave the rope if it has the proper
dimensions.
Stranded Ropes
Left-hand ordinary lay (LHOL) wire rope
(close-up). Right-hand lay strands are
laid into a left-hand lay rope.
Right-hand Lang's lay (RHLL) wire rope
(close-up). Right-hand lay strands are
laid into a right-hand lay rope.
Stranded ropes are an assembly of several
strands laid helically in one or more layers
around a core. This core can be one of
three types. The first is a fiber core, made up of synthetic material. Fiber cores are the
most flexible and elastic, but have the downside of getting crushed easily. The second
type, wire strand core, is made up of one additional strand of wire, and is typically used
for suspension. The third type is independent wire rope core, which is the
most durable in all types of environments.[5] Most types of stranded ropes only have one
strand layer over the core (fibre core or steel core). The lay direction of the strands in
the rope can be right (symbol Z) or left (symbol S) and the lay direction of the wires can
be right (symbol z) or left (symbol s). This kind of rope is called ordinary lay rope if the
lay direction of the wires in the outer strands is in the opposite direction to the lay of the
outer strands themselves. If both the wires in the outer strands and the outer strands
themselves have the same lay direction, the rope is called a lang lay rope (formerly
Albert’s lay or Lang’s lay). Multi-strand ropes are all more or less resistant to rotation
and have at least two layers of strands laid helically around a centre. The direction of
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the outer strands is opposite to that of the underlying strand layers. Ropes with three
strand layers can be nearly non-rotating. Ropes with two strand layers are mostly only
low-rotating.
Classification of ropes according to usage:
Depending on where they are used, wire ropes have to fulfill different requirements. The
main uses are:
Running ropes (stranded ropes) are bent over sheaves and drums. They are
therefore stressed mainly by bending and secondly by tension.
Stationary ropes, stay ropes (spiral ropes, mostly full-locked) have to carry tensile
forces and are therefore mainly loaded by static and fluctuating tensile stresses.
Ropes used for suspension are often called cables.
Track ropes (full locked ropes) have to act as rails for the rollers of cabins or other
loads in aerial ropeways and cable cranes. In contrast to running ropes, track ropes
do not take on the curvature of the rollers. Under the roller force, a so-called free
bending radius of the rope occurs. This radius increases (and the bending stresses
decrease) with the tensile force and decreases with the roller force.
Wire rope slings (stranded ropes) are used to harness various kinds of goods.
These slings are stressed by the tensile forces but first of all by bending stresses
when bent over the more or less sharp edges of the goods.
Rope Drive
There are technical regulations for the rope drives of cranes, elevators, rope ways and
mining installations not exceeding a given tensile force and not falling short of a given
diameter ratio D/d of sheave and rope diameters. A general dimensioning method of
rope drives (and used besides the technical regulations) calculate the five limits:
Working cycles up to rope discarding or breakage (mean or 10% limit) -
Requirement of the user
Don and t force (yielding tensile force for a given bending diameter ratio D/d) - strict
limit. The nominal rope tensile force S must be smaller than the Don and force SD1.
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Rope safety factor = minimum breaking force Fmin / nominal rope tensile force S.
(ability to resist extreme impact forces) - Fmin/S ≥ 2,5 for simple lifting appliance
Discarding number of wire breaks (detection to need rope replacement) Minimum
number of wire breaks on a reference rope length of 30d should be BA30 ≥ 8 for
lifting appliance
Optimal rope diameter with the max. rope endurance for a given sheave diameter D
and tensile rope force S - For economic reasons the rope diameter should be near
to but smaller than the optimal rope diameter d ≤ dopt.
The calculation of the rope drive limits depends on:
Data of the used wire rope
Rope tensile force S
Diameter D of sheave and/or drum
Simple bendings per working cycle w-sim
Reverse bendings per working cycle w-rev
Combined fluctuating tension and bending per working cycle w-com
Relative fluctuating tensile force delta S/S
Rope bending length l
Safety
The wire ropes are stressed by fluctuating forces, by wear, by corrosion and in seldom
cases by extreme forces. The rope life is finite and the safety is only given by inspection
for the detection of wire breaks on a reference rope length, of cross-section loss as well
as other failures so that the wire rope can be replaced before a dangerous situation
occurs. Installations should be designed to facilitate the inspection of the wire ropes.
Lifting installations for passenger transportation require that a combination of several
methods should be used to prevent a car from plunging downwards. Elevators must
have redundant bearing ropes and a safety gear. Ropeways and mine hoistings must
be permanently supervised by a responsible manager and the rope has to be inspected
by a magnetic method capable of detecting inner wire breaks.
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Terminations
Right-hand ordinary lay (RHOL) wire rope terminated in a loop with a thimble and
ferrule.
The end of a wire rope tends to fray readily, and cannot be easily connected to plant
and equipment. There are different ways of securing the ends of wire ropes to prevent
fraying. The most common and useful type of end fitting for a wire rope is to turn the
end back to form a loop. The loose end is then fixed back on the wire rope. Termination
efficiencies vary from about 70% for a Flemish eye alone; to nearly 90% for a Flemish
eye and splice; to 100% for potted ends and swagings.
Thimbles
When the wire rope is terminated with a loop, there is a risk that it will bend too tightly,
especially when the loop is connected to a device that spreads the load over a relatively
small area. A thimble can be installed inside the loop to preserve the natural shape of
the loop, and protect the cable from pinching and abrading on the inside of the loop.
The use of thimbles in loops is industry best practice. The thimble prevents the load
from coming into direct contact with the wires.
Wire rope clamps/clips
A wire rope clamp, also called a clip, is used to fix the loose end of the loop back to the
wire rope. It usually consists of a U-shaped bolt, a forged saddle and two nuts. The two
layers of wire rope are placed in the U-bolt. The saddle is then fitted over the ropes on
to the bolt (the saddle includes two holes to fit to the u-bolt). The nuts secure the
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arrangement in place. Three or more clamps are usually used to terminate a wire rope.
As many as eight may be needed for a 2 in (50.8 mm) diameter rope. There is an old
adage; be sure not to "saddle a dead horse." This means that when installing clamps,
the saddle portion of the clamp assembly is placed on the load-bearing or "live" side,
not on the non-load-bearing or "dead" side of the cable. According to the US Navy
Manual S9086-UU-STM-010, Chapter 613R3, Wire and Fiber Rope and Rigging, "This
is to protect the live or stress-bearing end of the rope against crushing and abuse. The
flat bearing seat and extended prongs of the body (saddle) are designed to protect the
rope and are always placed against the live end." The US Navy and most regulatory
bodies do not recommend the use of such clips as permanent terminations.
Swaged terminations
Swaging is a method of wire rope termination that refers to the installation technique.
The purpose of swaging wire rope fittings is to connect two wire rope ends together, or
to otherwise terminate one end of wire rope to something else. A mechanical or
hydraulic swager is used to compress and deform the fitting, creating a permanent
connection. There are many types of swaged fittings. Threaded Studs, Ferrules,
Sockets, and Sleeves are a few examples. Swaging ropes with fibre cores is not
recommended.
Wedge sockets
A wedge socket termination is useful when the fitting needs to be replaced frequently.
For example, if the end of a wire rope is in a high-wear region, the rope may be
periodically trimmed, requiring the termination hardware to be removed and reapplied.
An example of this is on the ends of the drag ropes on a dragline. The end loop of the
wire rope enters a tapered opening in the socket, wrapped around a separate
component called the wedge. The arrangement is knocked in place, and load gradually
eased onto the rope. As the load increases on the wire rope, the wedge become more
secure, gripping the rope tighter.
Potted ends or poured sockets
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Poured sockets are used to make a high strength, permanent termination; they are
created by inserting the wire rope into the narrow end of a conical cavity which is
oriented in-line with the intended direction of strain. The individual wires are splayed out
inside the cone, and the cone is then filled with molten zinc, or now more commonly,
an epoxy resin compound.
Eye splice or Flemish eye
The ends of individual strands of this eye splice used
aboard a cargo ship are served with natural fiber cord
after the splicing is complete. This helps protect
seaman's hands when handling.
An eye splice may be used to terminate the loose end
of a wire rope when forming a loop. The strands of the
end of a wire rope are unwound a certain distance, and
plaited back into the wire rope, forming the loop, or an
eye, called an eye splice. When this type of rope splice
is used specifically on wire rope, it is called a "Molly
Hogan", and, by some, a "Dutch" eye instead of a
"Flemish
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