tower crane -II
Tower crane 1 Basic Parts of Tower Crane Tower Crane Supplier
Siting and Base Preparation
Decisions taken on the types of crane required for any particular task will be influenced by the inspection of the working site.
The cranes selected should preferably have a working margin in excess of the overall job requirements.
Particular attention should be given to the following factors;
1. Presence of any hazards within the proximity of the crane;
2. The crane standing (ground bearing surface) or support.
The ground must be capable of supporting the crane and its load under all operating conditions. In the event of subsidence, the stability of the crane would be effected and this could produce a dangerous condition.
The ground bearing pressure of a crane should never be underestimated, whether the crane is n service or out of service? If there is any doubt, the advice of the makers should be sought.
When a crane is'n service the ground bearing pressure on the crane standing can be attributed to by the combined effects of the following:
1. The gross weight of the crane;
2. Weight of the load and lifting gear;
3. Dynamic forces from movement of crane and load;
4. wind forces upon the crane structure and the load.
Even when the crane has been placed 0ut of service all the factors stated above still apply, with the exception of the weight of the load and lifting gear.
The ground bearing weight of the crane is transmitted to its standing or support via the carriage wheels, crawlers tracks, outriggers or fixed base.
The magnitude of the forces imparted by the ground bearing weight of the crane will vary according to the position and movement of the crane and its load, and the wind velocity/direction in relation to the position of the crane and jib.
The effects of the wind on a crane structure can be very considerable during on service, or out of service conditions, and they should never be under-estimated. The provision of an anemometer (wind speed indicator) is an essential safety requirement.
This is of particular importance for a crane with a higher tower or a long jib, or even for a crane with a basic jib length when it is working in an unsheltered area.