www.hotsblack.com - CATEGORIES AND FEATURES OF TOWER CRANE(1)

www.hotsblack.com - CATEGORIES AND FEATURES OF TOWER CRANE(1)

Figure 1.3 Parts of a tower crane 
Tower cranes have a number of different features, which may vary in their construction. The tower or mast provides the height required for the crane operation. The tower supports the operator's cab, the main or load-carrying jib and the counter jib on which the crane motors, winches and counterweights are located. (Figure 1.3)


1.Common types of crane (issues for safety and selection)

(a) Horizontal trolley or saddle jib ("A" frame type,Figure 1.4)
 * the jib is held in a horizontal or slightly raised position by tie bars or ropes connected to an "A" frame on the top of the crane tower
* fixed length horizontal jib - the hook is suspended from a trolley which moves along the jib to alter the hook radius
* high capacity available
* can be erected with the tower inside building
* but, needs access for erection and dismantling; semi-permanent structure; jib radius unalterable for out-of-service condition. Consequently fitting in multiple cranes on a congested site may be a problem.



(b) Horizontal trolley or saddle jib (Flat top type,Figure 1.5)
* the horizontal cantilever jib is connected directly to the tower top and does not require tie bars or ropes connected to an "A" frame
* reduced overall height of the crane which can be important on congested sites, near airports and where adjacent cranes oversail
* the hook is suspended from a trolley which moves along the jib to alter the hook radius
* higher weight for a given capacity because of jib being a pure cantilever
* can be erected with the tower inside building
* but, needs access for erection and dismantling; semi-permanent structure, jib radius unalterable for out of service condition. Consequently fitting in multiple cranes on a congested site may be a problem.


(c) Luffing jib (Figure 1.6)
* the jib angle can be changed to reposition the load at various radii. The jib may be single- or multi-component, and if multi-component, may be articulated (goose necked)
* lower capacity than trolley jib cranes for a given tower size but may be lower tower
height
* radius can be altered to avoid obstructions which can be useful on congested sites (higher crane density likely to be possible) or to avoid oversailing other sites/buildings
* care is needed with out-of service position and high wind speeds as the jib can be blown over backwards if the radius is too small, and there may be insufficient wind area to allow the crane to weathervane - check manufacturers' instructions
* can be erected within building
* slow relative to trolley jib cranes
* generally require a bigger power supply than trolley jib cranes of equivalent capacity as additional motor power is needed to alter the angle of the jib.



(d) Self-erector (Figure 1.7)
* alternative to smaller top slew tower cranes or mobile cranes or tele-handlers
(forklifts with telescopic booms)
* space for access, erection and dismantling still required
* lower capacity
* normally mounted on wheeled chassis to facilitate transport to and movement
around site (although not while carrying loads!)
* can also be mounted on rail-going or crawler chassis to enable a greater area to be
covered on site
* generally outside the scope of this report. www.hotsblack.com

Berita Terkait :

www.hotsblack.com CATEGORIES AND FEATURES OF TOWER CRANE(2)

CALCULATION OF TOWER CRANE ANCHORAGE REACTION :

0 komentar:

Posting Komentar

 
Design Downloaded from Free Website Templates Download | Free Textures | Web Design Resources