Boom Pendants

should show the boom is at zero degrees or adjusted to read  zero  degrees. The boom angle indicator is a quick reference for the  operator  to  know  what  angle  the  boom  is  at. However, do NOT rely on the boom angle indicator for radius accuracy especially when the lift exceeds 75 percent   of   the   rated   capacity.   Use   the   radius measurement to determine the capacity of the crane from the load charts and to avoid any possibility of error. Sheaves Sheaves are located in the hook block boom tip, boom bridle, gantry, and boom mast. Sheaves rotate on either  bearings,  or  bushings,  and  are  installed  basically anywhere wire rope must turn or bend. Boom Pendants A  pendant  line  is  a  fixed-length forming part of the boom suspension section  of  boom  has  two  boom  pendants. of  wire  rope, system.  Each Both pendants must stay with the section of the boom they came with. When storing a boom section, secure the two pendants to the boom section with tie wire or rope. If a pendant is bad, both pendants must be replaced. If you only replace  the  one  bad  pendant,  the  new  or  replaced pendant could be of a different length or be different in manufacture.  This  difference  will  cause  an  uneven  pull or twist on the boom when the boom is put under a load or strain. Jib and Extension Figure  12-17  shows  one  type  of  jib  and  boom extension. A jib is an extension of a boom capable of being mounted on either a hydraulic or lattice boom. The jib is equipped with its own forestay pendant lines, connected from the jib tip to the jib mast. The jib mast is connected to the boom tip. The jib backstay pendant is normally manually adjustable to change the angle of the jib. On most cranes the function of the jib is to increase the lift height and to aid in increasing load radius. The operator’s manual will have instructions on how to install a jib or extension. You must remember if lifts are made with the main hook block the weight of the jib assembly  will  reduce  the  lifting  capacity  of  the  crane; therefore,  you  must  deduct  the  effective  weight  of  the jib assembly from the gross capacity of the crane. Gantry The  gantry,  or  A-frame,  is  a  structural  frame, extending  above  the  revolving  superstructure  (fig. 12-18). The gantry supports the sheaves in which the Figure  12-17.—Jib  and  boom  extension  mounted  on  a hydraulic  boom. Figure  12-18.-Gantry. 12-9


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