Such a vessel is known from the prior art. During the laying of the pipeline the tower is positioned in an upright position, with an angle relative to the hull structure that is variable. If for one reason or another, the pipelaying operation has to be stopped, for instance when bad weather conditions are forecasted, the vessel has to be prepared for pipe abandonment. This means that the pipeline has to be abandoned from the vessel by positioning the pipeline on the seabed. Furthermore, the tower has to be pivotally lowered towards the hull structure and placed in a lowered position. The pipeline may remain connected to the vessel via for example a cable. Because of the high waves which occur during bad weather, the length of said cable must be such that it provides sufficient clearance between the vessel and the pipeline.
The known vessel abandons the pipeline by means of the A&R means which are provided in the tower. Said A&R means generally comprises reeling means with long cables. During the abandoning operation it is required that the tower remains in an upright position. After the pipeline is positioned on the seabed, the lowering of the tower towards the hull structure and in the lowered position can be started. Said preparation of the vessel for bad weather is a time consuming operation. This is also the case for the preparation of the vessel for resuming an operation, for instance after the weather conditions have improved. For this, the tower has first to be raised from the hull structure to an upright position. After that, the pipeline can be recovered by the A&R means.
This means that the preparation of the vessel for bad weather or for resuming an operation after bad weather is very time consuming. Due to this, costly operational time in which pipeline can be laid is lost.
Furthermore, due to the fact that the preparation of the vessel for bad weather is very time consuming, said preparation has to be started long before the bad weather is expected to arrive. The accuracy of a weather forecast highly depends on the time period in which said forecast is made. This means that a bad weather forecast which is made several hours before the actual arriving of the bad weather is far more accurate than a forecast made one day or more before the arrival of said bad weather. With the known vessel it often happens that due to the a wrong weather forecast, the vessel is taken out of operation and prepared for bad weather, while said bad weather at the end changes of course and does not arrive at the vessel location. Many hours of operational time often lost this way.