This application is the National Phase of PCT/NL2008/000045 filed on Feb. 15, 2008, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 60/901,661 filed on Feb. 16, 2007, all of which are hereby expressly incorporated by reference into the present application.
The invention relates to a hoisting crane comprising:                a substantially hollow vertical column with a foot which is or can be fixed to a support, and with a top,        an annular bearing structure, which extends around the vertical column and guides and carries a jib connection member, so that the jib connection member can rotate around the column,        a jib connected to the jib connection member, the jib connection member forming a substantially horizontal pivot axis so that the jib can be pivoted up and down,        a column top cable guide having a topping cable and hoisting cable pulley assembly,        a topping winch and an associated topping cable for pivoting the jib up and down,        a hoisting winch and an associated hoisting cable for hoisting a load;wherein the topping winch and the hoisting winch are disposed such that the hoisting cable and the topping cable extend from the associated winch upward through the column to the column top cable guide and from said column top cable guide to the jib, wherein the jib has topping cable pulley assembly for the topping cable and a hoisting cable pulley assembly for the hoisting cable,        wherein the column top cable guide is mounted via an associated rotary bearing structure at the top of the column, such that said column top cable guide follows rotary movements of the jib about the vertical column and adopts substantially the same angular position as the jib. Hoisting cranes of this type, also known as a Heavy Lift Mast Crane (HLMC) have already been commercially available from the applicant for decades, and have in particular been installed on vessels, such as for example a cargo vessel, transport vessel, a tender vessel used in the offshore industry, marine pipelaying vessel, drilling vessel, etc.        
As is preferred the vertical column of the hoisting crane has a substantially continuous outer wall. The horizontal section through the vertical column is substantially circular from the jib connection member to the top, with the cross section gradually decreasing towards the top of the column. The column has a foot which is often substantially rectangular, which has the advantage that the foot can easily be secured (by welding or using bolts) to the longitudinal and transversal bulkheads of a hull of a vessel of which an example is shown in FIG. 1.
The known hoisting crane is popular for vessels that have been specially designed for over sea transport of large and heavy equipment. Capacities in a range from 200 mt up to 1600 mt and load moments in a range from 3000 tm up to 40,000 tm are possible.
FIG. 1 shows an example of a pipelaying and heavy lift vessel equipped with a hoisting crane as described above. Here, the hoisting crane is provided with a fly-jib, which forms the end of the jib. At about a quarter length from the distal end of the jib, a topping cable pulley assembly is mounted to connect the multiple fall topping cable to the jib. Many known hoisting cranes do not have a fly-jib and are provided with a topping cable pulley assembly at the end of the jib. The multiple fall topping cable functions to move the jib up- and downwards.
The upward or topped position of the jib is defined by an angle (angle α in FIG. 1), which is formed between a centerline of the jib and the multiple fall topping cable. When this angle α becomes too small, it is not possible to top the jib further upward anymore. In such a situation the multiple fall topping cable lies nearly parallel to the jib. Thus, a higher vertical column of the crane would permit the jib to be pivoted further in upward direction and with this the hoisting crane can handle larger objects. A higher vertical column is also advantageous during hoisting when the jib is in a lower, e.g. substantial horizontal position.
The forces, which occur when hoisting a heavy load, introduce less tension in the topping cable, when the hoisting crane is designed with a bigger angle α between the topping cables and the jib, when the jib is in the horizontal position. Normally in open sea there are no difficulties with the large geometry of the hoisting crane, but a great height of the crane does effectively limit the operational area of the vessel with such a crane. For example, sometimes the vessel has to come close to a large building on the quayside, close to a drilling rig, or it has to travel inland and pass under a structure like a bridge.