Erection of tower When the base or chassis has been set up, the tower (which may include the slewing gear and tower head) is then erected and attached to it using a second crane or a self-erection procedure. In either case the tower should be correctly orientated within the base section.
Where the jib is attached to the tower head before the tower is raised from horizontal to the vertical position, some means, such as a plank or board should be placed beneath the outer end of the jib to ensure that it can move freely across the ground as the tower is raised.
Where a second crane is used for erection, the number of sections in any tower sub-assembly should be minimum as to eliminate excessive stresses in the assembly when it is raised from the horizontal to the vertical position. It is recommended that jib-ties are attached before the jib is raised and positioned at the top of the tower section. When a tower section or sub-assembly has been Code of Practice for Safe Use of Tower Cranes 45 placed in position, all bracings, locking devices, etc., should be attached and bolts securely tightened before proceeding with the next stage of the erection operation. It is essential to ensure that any specially strengthened tower sections are positioned where required.
It may be necessary to guy or support the tower depending on its free standing height. When tensioning the guys, ensure that the pull is even on each and that the tower remains perfectly plumb. Ensure also that blocking is installed in the tower to support the guys and to prevent the tower from being damaged.