Page 243 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

232 CHAPTER 9 LARS and TMS
• Requirement for an internal slipring (usually the case).
• Grooved drum liner—which can help with the proper wrapping of the cable on the drum.
• Level wind—unless a good fleet angle is available, which is usually not the case on limited
space platforms, a level wind will ensure that the cable is being spooled evenly.
• Minimum bend radius—the minimum bend radius of the cable must be taken into consideration
when determining the drum core diameter.
An example of a standard winch with a level wind and hydraulic system (to the right) is shown in Figure 9.11. The winch has a maximum line pull of 33,075 lb (15,000 kg) at full drum with a 1.25 safe working load and can hold 9062 ft (2760 m) of cable. The footprint is approximately 16.6 ft (5 m) by 10.3 ft (3.2 m).
9.2.1.2 Traction winch
If higher tension operations are to be encountered with heavy loads, then a traction winch may be required. Dynacon’s Model 5521XL (Figure 9.12) traction winch system upgrade to the previous winch brings the maximum line pull up to 49,600 lb (22,500 kg). However, the footprint increases by about 30% and the weight reaches 63,000 lb (28,566 kg), without the cable but with the hydraulic power unit.
9.2.1.3 Heave compensation
If high sea states are expected, then heave compensation options exist that can be stand alone or combined with the winch itself (Figure 9.13). The bottom line is that the umbilical needs to have the slack taken up or additional payed out as the dynamics dictate. If these heave dynamics are not compensated for then the vehicle at the end of the umbilical will not be stable and/or the umbilical can become overstressed and damaged.
Heave compensation systems come in either “Active” or “Passive” versions depending upon their configuration. With active heave compensation (AHC), motion sensors sense vessel movement about the vessel’s vertical axis of movement. These sensors measure the amount of heave and
FIGURE 9.11
Dynacon 521XL general purpose ROV winch.