Hii readers, today we will show you some tips how to select correct crane envelope that will fit in the building foot print, and the user must identify and pass on the following key information to the supplier before proceed with manufacturing process:
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.
Ok, thats all for today. We will learn some more in next post. Thank you for reading.
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