EOT
crane are widely used in range of material handling application. Selection of
EOT Crane is quite cumbersome. To select correct EOT Crane envelope that will
fit in the building foot print, the user must identify and pass on the
following key information to the supplier:
1)
Crane Capacity * - The rated load, the
crane will be required to lift. Rated load shall mean the maximum load for
which a crane or individual hoist is designed and built by the manufacturer and
shown on the equipment identification plate.
2)
Lift Height - The rated lift means the
distance between the upper and lower elevations of travel of the load block and
arithmetically it is usually the distance between the beam and the floor, minus
the height of the hoist. This dimension is critical in most applications as it
determines the height of the runway from the floor and is dependent on the
clear inside height of the building. Do not forget to include any slings or
below the hook devices that would influence this value.
3)
Runway Height – The distance between the
grade level and the top of the rail.
4)
Clearance- The vertical distance
between the grade level and the bottom of the crane girder.
5)
Clear Span- Distance between columns
across the width of the building. Building width is defined as the distance
from outside of eave strut of one sidewall to outside of eave strut of the
opposite sidewall. Crane Span is the horizontal center distance between the
rails of the runway on which the crane is to travel. Typically distance is
approximate to 500mm less than the width of the building. How much span a crane
requires depends on the crane coverage width dictated by the application.
(According to the span and the maximum load handling capacity, the crane steel
structure is selected to be either a single or double girder crane
construction).
6)
Building Height-
Building height is the eave height which usually is the distance from the
bottom of the main frame column base plate to the top outer point of the eave
strut. Eave height is the distance from the finished floor to the top outer
point of the eave strut. There must be a safety distance between the top edge
of the crane runway rail and the first obstacle edge in the building (for
example roof beams, lights and pipes).
7)
Runway Length- The longitudinal run of
the runway rail parallel to the length of the building.
8)
Hook approaches -
Maximum hook approach is the distance from the wall to the nearest possible
position of the hook. The smaller the
distance is, the better can the floor area be utilized. Always check which
crane gives optimum hook approaches and when combined with the true lift of the
hoist you can utilize most of the available floor space. This is also termed as
side hook approach.
End
Approach –
This term describes the minimum horizontal distance, parallel to the runway, between the outermost
extremities of the crane and the centerline of the hook.
9)
Bridge, Trolley and Lift Speeds - The
rate at which the bridge or trolley travels or at which the hoist lifts is
usually specified in feet per minute or FPM. The crane operating speeds are
selected to allow safe operation whilst using the pendant. Dual operating
speeds, normally a fast and slow speed with a ratio of 4:1 are commonly used
but for optimum control a variable speed control system is strongly
recommended.
10)
Electrical Requirements -
Specify the circuit voltage shall not exceed 600 volts for AC or DC current.
Ideally 480 volt, 3 phase, 60 hertz for US requirements. The runway power is
usually by conductor bar and hoisting trolley by festoon cable. (refer section
6 for details)
11)
Control Requirements - The
control circuit voltage at pendant pushbuttons shall not exceed 150 volts for
AC and 300 volts for DC. Other control options including radio control,
free-floating pendant (festooned) or hoist-mounted pendant requirements must be
stated.
Other than addressing the above parameters, some
specific conditions applicable to your application must be mentioned.
1)
Do you need the use of a second hoist on the
bridge crane? (This hoist may be used as an auxiliary hoist or be required in a
process such as tilting/tipping. In case you are handling long materials, like
steel tubes and plates, the best solution are to have a crane with two hoists
(and hooks) for better stability of the load ensuring safe lifting).
2)
What will the operating environment be (dust,
paint fumes, outdoor, etc.)?
3)
Is there existing cranes on the runway? Then,
consider the use of a collision avoidance or collision warning system.
