ment ships are envisioned, with one ship having heavy-lift capacity, one 

 ship acting as a termination and collection point of the nnooring legs, and 

 one ship acting as a wire rope or cable supply and assist ship. A fourth ship, 

 such as a seagoing tug, may be required for moor tensioning and intership 

 transfer. 



On arrival at the mooring site, the three ships take a position over 

 the site of the first mooring leg anchor. Then the anchor is lowered in a 

 controlled manner, keeping a constant rate of tension on the wire rope to 

 place the anchor as opposed to dropping it. The use of a battery-operated 

 bottom-sensing device attached to the anchor serves to indicate depth and 

 anchor position relative to the bottom. A scheme using a different frequency 

 for the sensing device on each anchor would provide an accurate positioning 

 system. 



An example of an anchoring system is shown in Figure 8. The anchor, 

 a single shot of chain, a clump, and at least two additional shots of chain are 

 attached to steel wire rope and deployed the full scope length. The wire rope 

 is then connected to the terminal swivel socket and to the catenary support 

 buoy. A nylon mooring line is attached to the terminal rig. This nylon 

 mooring line is connected to a second ship at the central position of the 

 moor, which would also be the location of the surface plant. Tension is kept 

 by the second ship while the mooring legs are deployed 180 degrees apart. 

 An estimate of mooring time per leg is 1 day to depths of 6,000 feet and 2 

 or 3 days per leg to depths greater than 6,000 feet. On completion of the 

 deployment of the mooring system the surface plant hull js towed to the 

 ship at the plant site. The nylon mooring lines are transferred from the 

 ship to the hull by divers. This involves passing the lines through hawsepipes 

 to the termination points (bits) on the deck of the hull. If required, a winch 

 is used to pretension the lines. 



The load module is deployed by positioning it relative to the bottom 

 and slightly off-center along a bisector of the mooring legs. The ship that 

 lays the power cable is brought alongside and the power cable is connected 

 to the load module. The submergence of the load module and the paying 

 out of the power cable from the ship storage drum are synchronized. On 

 completion of the deployment of the load module the power cable is trans- 

 ferred and connected to the surface plant. 



Two basic modes of load module emplacement are available: the 

 free-fall technique and the tethered concept described earlier for the in-situ 

 plant emplacement. The free-fall technique was not considered suitable for 

 this emplacement. The second scheme involves tethering at the surface or at 

 the bottom and winching down from the deployment ship. A surf ace- tethered 

 emplacement uses a cable attached to the deployment vessel and is winched 



77 



