Introduction to Tower Cranes
Slide 2 OBJECTIVE:
To begin your introduction to tower cranes you will first learn about the different types of tower cranes
and how they are used in the construction world. Next you will be shown the different tower crane
model designations within Terex and their meanings. Once this has been explained to you we will move
on to the components that make up a tower crane, where they are located and their respective
functionalities.
What you will learn in this module will give you the necessary foundation on which you will build your
knowledge concerning tower cranes in the following courses and help you to understand how they are
designed and function.
Slide 3 OVERVIEW:
Tower cranes have been in existence in one form or another for hundreds of years. These machines
made it possible to lift materials for the construction of buildings and load cargo onto boats and ships.
These machines made it possible to build larger and more complicated structures and helped advance
the construction of larger ships in which they would load the cargo for transportation around the world.
In this module you will learn about the different typologies of tower cranes in use today and the
components that make them up.
Slide 4
The first construction cranes were invented by the ancient Greeks and were powered by either men or
beasts of burden. These cranes were used to construct taller buildings and structures and eventually
employed human tread wheels which enabled them to lift heavier loads. The earliest cranes were
constructed of wood but as cast iron and steel became available, their structure changed to incorporate
these advanced materials and their capacities grew. The tower crane’s birth resulted from a need to
build taller and taller structures. Their original design has been modified and built upon resulting in a
highly technical machine capable of lifting tens of thousands of pounds of material hundreds and even
thousands of feet in the air.
Slide 5
Tower cranes are ideal for hi-rise construction projects. Their small footprint and ability to cover a large
area without interfering with activities on the ground make them ideally suited to this type of work. In
addition the operator has an excellent view of the jobsite and what’s going on beneath him. With the
exception of some diesel generator powered units the majority of tower cranes are electrically powered
making them extremely quiet with zero emissions.
Slide 6
Terex tower cranes are divided into three families: CTT, CTL and SK. In the following slides you will learn
the meaning of these designations and the models which make up each family of cranes.
Slide 7
The first category of Terex tower cranes that we will take a look are the CTT’s. The CTT designation
stands for Crane, Tower, Topless, or in other words a Flat Top Tower Crane. This means that there is no
tower top or other structure in place to support the jib.
Slide 8
As we take a closer look into the CTT family of cranes, you will need to know the meanings of certain
designations which make up the model numbers for each machine. Let’s use the CTT181B-8 as an
example. The CTT tells us that it is a flat top crane, the 181 indicates the ton meter rating of the
machine in terms of capacity, the B tells us that this is the third version produced (starting with 181,
then 181A etc), and the 8 indicates the maximum capacity in metric tons. The second example is a flat
top tower crane rated at 561 meter-tons, this is the second version produced, it is rated at 32 metric
tons and is designed to work with HD23 tower sections.
Slide 9
There are three classifications of cranes within the CTT family: City Class, Medium Class and Large Class
cranes. Let’s begin with the City Class. The City Class is currently made up of these six models which
range in maximum capacity from 2.5 to 8 metric tons and maximum jib lengths of 50 to 65 meters. This
class features the hoist, trolley and all electrical controls on the first jib section enabling the entire upper
structure to be erected in as little as four picks with the erection crane. This greatly reduces erection
time thus reducing the erection costs. These cranes are used on projects where large capacities at
extreme radii are not required.
Slide 10
The Medium Class is made up of two models which range in maximum capacity from 8 to 12 metric tons
and maximum jib lengths of 65 to 70 meters. This class also features the hoist, trolley and all electrical
controls on the first jib section enabling the entire upper structure to be erected in as little as four picks
with the erection crane. This greatly reduces erection time thus reducing the erection costs. These
cranes are used on projects where larger capacities and extended radii are required.
Slide 11
The large class cranes consist of the 331, 561A and 721 models which range in maximum capacity of 16
to 40 metric tons and maximum jib lengths of 75 to 84 meters. These cranes are used on large, high-rise
projects where larger capacities at greater radii are required. The hoist motor and other electrical
components are located on the rear or counter-jib of the crane and the trolley motor is located on the
first jib section.
Slide 12
The Flat Top is characterized by the absence of a tower top and pendants. The tee section, counter-jib
and jib sections make up the support structure.
Without the tower top and pendants, erection is simpler and allows for flexibility in erection depending
on the job site. Individual jib sections can be erected if there isn’t sufficient room on the job site to
assemble multiple jib sections together on the ground.
In addition without the tower top, less air space required making flat tops ideal for airport projects (less
radar signature) or other areas where height may be an issue. Job sites with multiple cranes are also
excellent for flat tops because they only require one tower section in order to have sufficient clearance
between cranes.
Slide 13
These are examples of the various components of the CTT cranes, the slewing ring and operator’s cabin,
trolley winch and motor and the hoist winch bed.
Slide 15
Here are several more components shown during the erection phase: The trolley and hook block, the
counter-jib and outer jib assembly.
Slide 16
The next category of Terex tower cranes are the CTL’s which stands for Crane Tower Luffing or in other
words a Luffing Tower Crane or Luffer. A luffing tower crane is different from the flat top in that the jib
moves vertically from 15˚ to 85˚ eliminating the need for a trolley. The A-frame is stationary and acts as
a pathway for the luffing hoist winch rope and as a support structure for the luffing jib.
Slide 17
As we take a closer look into the CTL family of cranes, you will see that the designations which make up
the model numbers for each machine are the same as for the CTT cranes. Let’s use the CTL180-16 TS23
as an example. The CTL tells us that it is a luffing tower crane, the 180 indicates the ton meter rating of
the machine in terms of capacity, the 16 indicates the maximum capacity in metric tons and the TS23
tells us it’s designed to be used with the TS23 tower sections.
Slide 18
The machines which make up the CTL family of luffing tower cranes are broken down into two
classifications of cranes, Medium Class and Large Class cranes. Let’s begin with the Medium Class. The
Medium Class is currently made up of three models which range in maximum capacity from 8 to 18
metric tons and maximum jib lengths of 50 to 55 meters. This class features the main hoist, luffing hoist
and all other electrical controls are located on the counter-jib. These cranes are used on projects where
large capacities at extreme radii are not required.
Slide 19
The Large class of machines which make up the CTL family of luffing tower cranes are currently made up
of three models which range in maximum capacity from 20 to 32 metric tons and maximum jib lengths
of 60 meters. This class features the main hoist, luffing hoist and all other electrical controls are located
on the counter-jib. These cranes are used on projects where large capacities at extreme radii are
required.
Slide 20
These are examples of the various components of the CTL cranes in various stages of erection. The
slewing ring and operator’s cabin, counter-jib with counter-weight basket.
Slide 21
The counter-jib A-frame and the jib assembly.
Slide 22
A luffing jib tower crane is designed for the jib to move vertically to from 15 – 85 degrees.
They are specially designed for use in highly urbanized environments where swing areas are limited or
over-flying of adjacent buildings or other restricted areas is a factor.
These machines allow a higher machine density on a job site since their jib is able to be elevated up to
an 85˚ angle. The design of these machines also requires the main components to be heavier in order to
achieve their rated capacities. This additional weight also reduces freestanding heights requiring
structural tie ins and external climbing to extend the height of the crane.
Slide 23
The final family of cranes in the Terex lineup is the SK which stands for Slewing Crane. This series
features a tower top for structural integrity and pendant ropes which connect to the inner and outer jib.
This design feature allows the jib sections structural weight to be reduced and allow greater jib tip
capacities.
Slde 24
As we take a closer look into the SK family of cranes, you will see that the designations which make up
the model numbers for each machine are similar to the CTT and CTL cranes. Let’s use the SK415-20 as
an example. The SK tells us that it is a hammerhead tower crane, the 415 indicates the ton meter rating
of the machine in terms of capacity, the 20 indicates the maximum capacity in metric tons.
Slide 25
There are three models of cranes within the SK family which are made up of three models ranging in
maximum capacity from 16 to 32 metric tons and maximum jib lengths of 70 to 80 meters.
Slide 26
The hammerhead tower crane is characterized by the tower top and pendants which make up the
support structure for the crane.
The presence of the tower top does require that adjacent cranes must be at least two tower sections
taller in height to provide clearance between cranes.
Slide 27
These are examples of the various components of the SK cranes in various stages of erection. The
slewing ring and operator’s cabin. The counter-jib and the outer jib section.
Slide 28
Now that you’ve been introduced to all three families of Terex cranes, let’s take a look at the
components which make up these machines from the ground up. Just like a house, a tower crane must
have a strong and stable foundation. The mass of the foundation must be large enough to counter the
over-turning moment generated by the maximum load for which the crane is rated in its chosen
configuration.
The three types of foundations are the spread-footer, stationary undercarriage and traveling
undercarriage. The spread-footer is comprised of anchor stools which are connected to the first tower
section and anchored in a concrete base or foundation. The size and depth of the foundation is
determined by the underlying soil conditions and the configuration of the crane and will be discussed in
further detail in following modules. This type of foundation is most commonly used in the US.
Slide 29
The second type of foundation is the stationary undercarriage and is comprised of a steel framework
which supports the tower crane and concrete ballast blocks which are used to stabilize the structure.
These undercarriages may be mounted on concrete base blocks or on steel pedestal feet attached to the
undercarriage. The amount of concrete ballast placed on the undercarriage is determined by the
configuration of the crane and will be discussed in further detail in following modules. This type of
foundation is most commonly used in Europe.
Slide 30
The last type of foundation is the traveling undercarriage. It is essentially identical to the stationary
undercarriage with the addition of motorized “bogies” which enable the undercarriage to be propelled
along a steel tracks similar to railroad tracks. The amount of concrete ballast placed on the
undercarriage is determined by the configuration of the crane and will be discussed in further detail in
following modules. This type of foundation is the least common due to the expense in constructing the
rail bed and is found in shipyards, steel, cast concrete and lumber yards.
Slide 31
The next component that we will look at is the tower section. Terex tower sections range in diameter
from 1 to 4.5 meters and 2 to 12 meters in length and may be used in combination with other tower
sections when used with a transfer or transition section.
Slide 32
The tower sections are connected in three different manners, by pinning, with a a torqued 2 bolt per leg
connection or a pre-tensioned 4 bolt per leg connection.
Slide 33
Next in line in the erection of a tower crane is the rotator or turntable. This component connects the
upper portion of the tower crane to the tower sections. It is normally erected with the operator’s cabin
in place.
Slide 34
The rotator contains a number of components essential to the operation of the tower crane such as the
slewing bearing, main electrical control panel, anemometer, alarm horn, slewing motors, electrical slip
ring, heating and air conditioning and the operator’s cab.
Slide 35
Depending on the type of crane, a flat top will receive an upper slewing support, a luffer will receive an
A-frame and a hammerhead will receive a tower top.
Slide 36
The counter-jib is the next component in the erection process. It contains the electrical hoist control
cabinet, main hoist winch, hoist brake and counterweight. In the case of a luffing jib tower crane a
luffing winch is also included.
Slide 37
Once the counter-jib is mounted, the ballast blocks or counter-weights have to be set in place. Usually
there is a minimum amount required to balance the upper until the jib is erected. This amount is
dependent upon the required jib length and is stated in the operator’s manual.
Slide 38
The inner jib is mounted to the turntable via pinned connections.
Slide 39
Assembly of the outer jib takes place on the ground as does the inner jib with the last piece being the jib
tip.
Slide 40
And is hoisted by the erection crane and pinned to the inner jib section.
Slide 41
Now that we’ve taken a look at the major components which make up a tower crane, let’s look at the
other components. The hoist bed contains several different components such as the B panel which
contains the electrical controls for hoisting, the hoist drum, hoist motor, Hoist gear change motor, hoist
motor blower and hoist brake.
Slide 42
Tower cranes are usually equipped with one or two trolleys depending on the design. A two trolley
design requires an outer and inner trolley. The outer trolley is always required for two parts of line
operation and the inner trolley is required for four parts of line operation. The hook blocks are linked
together to form a single hook block assembly.
Slide 43
A single trolley design incorporates both two part and four parts of line operation into a single hook
block assembly. The block is converted into four parts of line operation by removing the pin and
separating the upper and lower halves of the block assembly.
Slide 44
A tower crane has many different limit switches which keep it operating safely. They are the trolley limit
switch, hoist limit switch, rated capacity limiter, rated moment limiter, traveling limit switch.
Slide 45
The rated capacity and moment limiters prevent the operator from lifting a load that is greater than the
capacity of the crane at radius. If the rated capacity or moment limiter limit switches are activated the
load may only be lowered or the trolley moved inward and not out, placing the crane in a safer
condition.
The traveling limit switch limits the traveling distance of the crane allowing it to slow down and stop in a
controlled manner to prevent striking the end stops and possible overturning the crane when moving
with a load.
The hoist limit switch limits the upper and lower position of the hook block preventing it from two
blocking into the trolley or striking the ground and introducing slack into the hoist drum causing damage
to the hoist rope.
The trolley limit switch limits the travel of the trolley stopping it at an inner and outer point on the jib to
prevent damage from striking the inner and outer jib stops.
Slide 46
Other components which may be used with tower cranes include climbing collars. These are used to
physically connect the tower crane to the structure that it is constructing to provide support as the
height of the tower crane is increased by an external climbing cage.
Slide 47
The external climbing cage as mentioned earlier is used to increase the height of a tower crane.
Slide 48
This is done by lifting the upper structure via a hydraulic jacking system and inserting additional tower
sections.
Slide 49
Lastly there is the internal climbing system which is employed within the building structure. This system
is used where it is impractical to use an external climbing cage or the extreme height of the structure is a
factor.