Jib cranes continue to dominate the market, some sites also use luffing jib cranes. A trend that is particularly true in urban areas where these materials have strengths to assert, but we are seeing more of them in the UK too, not just for big businesses but small ones as well.
Priority issues
The increasing number of city-building sites, with ever-higher construction and increasingly dense environments, benefits in fact from jib cranes, which are more flexible to use on sites where space is confined and where several cranes are brought to work at the same time. This is all the more true for those materials that have short counter flights and limited out-of-service radii, whereas the implementation of boom cranes requires greater distances between their bases. The other problem is that high cranes do not have priority over the lowest ones. In fact, their performance is bad. In the line of sight: collision avoidance systems which, when two distributor boom cranes cross each other, paralyze one while the other passes.
Unlike jib cranes, cranes cannot lift their loads to pass over their neighbors and thus continue their work. Under one of these machines, about 10 to 15 people work (scrap metal, masons, etc.). However, the salary of two of these people easily represents the monthly cost of renting a crane. Crisis helping, sites with very short deadlines tends to multiply. The use of luffing jib cranes thus ensures a better fluidity of the interactions between the cranes and, therefore, a greater speed of execution of the handling operations. But it is still necessary to calculate their productivity carefully. Because investing in a liftable crane, whether for renting or buying, has a cost that, given the economic context, can be discouraged.
More expensive
What makes them more expensive? It is first and foremost their motorization, more powerful. The luffing jib cranes are equipped with two high-power winches, the hoist winch and the boom hoist, while the boom cranes require a single hoist. Worse: these two winches are also bigger and more powerful. For example, for a 16-tonne crane – which, in addition to carrying a load, must also assume the boom lift – requires a 110-kW engine, whereas a crane-powered crane uses only a 75-horsepower engine. The costs are necessarily affected. In a multi-site construction setup, overlaid boom cranes induce much higher hook heights for overhead cranes.
The installation of several luffing jib cranes thus limits the heights under hook, which has the effect of reducing the cost of the equipment and its transport. If, in UK, the jib cranes still make up the bulk of the market, the use of luffing jib cranes is growing, even though traditionally they were previously used mainly for large height of work that they could work higher than their axis by anchoring on towers under construction.