The design of a reliable supply system for the work floor in a J-lay tower (summary)

4

Summary

Heerema Marine Contractors (HMC) is designing a new vessel with two functions. The first function is installation and removal of large components, which will be realized with two cranes at the back of the vessel with a lifting capacity of 5500 [mT] each.

The second function is deep sea pipe laying. This will be done with a J-lay system which has the pipe string hanging off the vessel. The prefabricated pipes are lifted and held in the tower, while welding of these pipes to the string, is arranged in the lower part. (See figure S1)

The tower can operate under different angles. This enables handling of different pipe diameters at different water depths. The work range lies between 60 and 110 [degrees]. For different reasons the tower can also be laid flat on deck.

The weld made in the lower part of the tower is performed at a work floor. The floor will be kept horizontal independent on the tower’s working angles (i.e. 60-110 [degrees]), to make it easy to work on. To be able to handle non standard pipes, for example a T-part in the pipe, the floor can also be moved a few meters forward within the tower, to create room for the pipe to pas.

In addition to the weld process a combination of processes are performed at this floor, for example blasting and coating. All these processes require equipment and consumables. The goal of this report is to design a reliable and safe handling system which can support, by delivering consumables and equipment, the welding process in the tower as good as possible. HMC has decided to transport the equipment and consumables towards the work floor in 20 foot containers.

Equipment is positioned on both sides and in front of the work floor as sketched in figure S2.

Figure S2: The work floor including the equipment

Figure S3: Tower top/section view including container positions

5 Containers with equipment and consumables will be moved on deck to the side of the slot (depicted blue in figure S3). From this position, the containers should be moved alongside the work floor (red) to get the containers at the front of the tower (green). Positioning containers at the back (vessel side) of the floor is not possible, because the loader (including the loaded pipe) uses this space.

HMC stated to use three equipment and two consumable containers. Two of the equipment containers should be lined up with the equipment rail as sketch in figure S4 and S5. The third equipment

container (containing the largest part of equipment) together with the two consumable containers should be lined up with the work floor. In case the work floor requires a motion to the front of the tower these three containers need to create sufficient space.

In addition to these requirements the containers need to be kept horizontal in case the tower is laid down. This is done for two reasons:

• To be able to protect the equipment.

• To be able to safely store different material present on the work floor.

Figure S4: Tower front view including containers in their position according to the work floor

Figure S5: Side view with container motions in front of the work floor

A system design was developed meeting almost all (stated and not stated) requirement. (See figures S6 & S7)

6 Drawbacks of this design were:

• The tower design hindered containers to be held horizontal at tower angles larger than 100 [degrees].

• The large complexity of the design, which implies large investment costs and unnecessary high cost of ownership. (The complexity is not made really clear in the figures, however detailing the design would show a significant complexity increase of the figures.)

For these reasons the requirements are critically analysed to be able to create a new design. During this investigation only requirement adjustments, meeting the following two criteria, were made.

• The pipe lay process may not be negatively influenced • The tower and vessel design should not be changed

The new set of requirements allowed the development of an improved concept which is shown in figure S8.

Figure S8: 3D view improved design

The improved design positions the equipment in rail at the front and starboard side of the floor. The consumable container is positioned at the port side.

Containers are moved from deck on a move-in trolley. This trolley is able to move containers along the work floor to the front of the tower at every work angle of the tower.

At the front of the tower this system is able to lift customized containers using a lift transport. These containers are equipped with rail where off equipment is hanging. This rail can be lined up with the equipment rail that is fixed to the tower. In case the tower is laid down, the equipment can be held horizontal in the equipment rail.

7 This improved design has a lower complexity which is verified by the number of drives needed. The improved design needs only 9 drives while the initial design needs at least 15 (drives of the equipment excluded).

The improved design also solves the problem at tower angles between the 100 and 110 [degrees]. To make this improved design only a few concessions had to be made which do not significantly influence the output of the system:

• Using one consumable container instead of two. • Repositioning of the equipment.

• Equipment is kept horizontal in its rail instead of in the containers. • The work floor shape is changed.

The fabrication of this design with an availability as desired seems possible and therefore the goal of the assignment is reached.