First of all in the prior art solutions in which the tubular elements or risers are stored in a covered hold and the movement of the tubular elements occurs by means of bridge cranes there are both safety problems concerning the movement of loads suspended over a vessel and efficiency problems in the exploitation of the space available in the hold of the vessel. In fact, the bridge crane arranged inside the hold occupies a great space for the entire length of the hold itself and this space, intended for the movement of the bridge crane over the stacks of tubular elements, is actually unused space for storage.
Furthermore, the movement of the tubular elements, which are very heavy, by means of bridge cranes and with suspension cables or rigid elements, exposes the tubular elements to impacts that may compromise their tightness or
coupling.
Moreover, the presence of the operators in the control zones exposes the operators themselves to conditions of possible danger.
Furthermore, the poor
automation of the process is often a serious problem in the phases of the operators'
shift change.
In fact when, after about six months, the operators are replaced by a new
crew, a reduction in the
crew's performance occurs with a consequent slowdown in the operations of laying of the tubular elements.
Furthermore, the prior art solutions make the phases of inspection of the tubular elements prior to their taking out difficult.
Before the hold is definitively closed the bridge crane remains exposed to the weather and damage that may compromise its functionality before the launch of the ship.
At present the selection of the risers to be taken as well as their loading operations are carried out by the operators manually, exposing the procedure to errors that may have serious consequences from the environmental point of view or, in any case, slowdowns in the operations of taking out or loading of the risers.
Further drawbacks of the prior art solutions derive from the fact that all the devices involved in the movement of the tubular elements are often considered separately starting from the ship
design phase, but also in the phase of
fitting out of the ship and even in the phase of use of the devices themselves.
The movement activities of the tubular elements, particularly in the case of the risers, are often made complex due to the number of necessary operations and to the number of various machines involved, which are not coordinated or integrated with one another and which must be necessarily managed manually by single operators with all the risks connected to errors of movement, fall of suspended loads, impacts, damage, etc.
As a consequence, a drawback of the prior art systems is that the loading and the taking out of the risers generally occurs manually by the operators who establish the order of loading.
An error by those who are in charge of the loading may cause following delays in the laying phase for example in the case in which a riser suitable to operate at great depths (that must be taken before the others) has been loaded on a bottom rack and below with respect to a series of risers suitable to operate at shallow depths (that must be the last to be taken).
Furthermore, if the operators in charge of the laying do not notice the error, they might lay at great depths a riser that is not suitable to operate at such depths with the risk of breaks that may cause irreparable environmental damage and compromise the operators' safety.