Figure 1: Chain Inspection on Rig Changeover Deck
Figure 2: ROV Mounted for In-Water Inspection
The failure of a mooring line on a mobile drill rig (MODU) can be catastrophic. Traditionally, the inspection and recertification of moorings on MODU facilities required the relocation of the facility to a dry-dock. This is expensive, time-consuming and risky.
Welaptega has developed an “in-air” inspection technique for moorings on mobile drill rigs. Inspections are conducted as the unit is drilling or as part of a scheduled move. This technique is safer, faster and avoids production downtime. This enables the drilling contractor to maximize safety, drill time and avoid contractual implications of elevated downtime or moving off station.
Welaptega’s inspection methods are largely video based, providing a permanent record which can be reviewed after inspection by the class society or other technical authorities. In-service MODU inspections are designed according to the mooring spread, type of rig, and the classification requirement for the MODU.
Welaptega’s inspection capabilities include chain, wire rope and fibre rope .
Rig-based (in-air) inspection as part of a scheduled MODU move or after a hurricane is perhaps the most efficient method in terms of maximizing inspection work scope while minimizing resources (anchor handlers, dive support vessel, etc).
Rig-based inspection is relatively non-invasive as it can coincide with MODU relocation, performed as part of mooring retrieval and redeployment processes.
Welaptega has modified its established underwater-deployed inspection equipment to be used from the inspection decks on the MODU columns. Inspection equipment and personnel can utilize the inspection platforms below the windlasses to inspect the mooring on retrieval/deployment.
Where it is not feasible to conduct the mooring inspection from the MODU itself, Welaptega can perform the inspection using ROV-deployed equipment. Much of the in-water inspection is limited to components in the catenary, rather than grounded or buried sections. However, in-water inspection can be made more comprehensive by use of an anchor handler to lift grounded/buried components. In-water inspection is also proving to be a method of quickly returning to service following a hurricane event.
The adopted method provides a combination of in-water and rig-based options to accommodate certain scenarios. For instance, if the MODU can pay the moorings partially in or out while on station, the full inspection can be accomplished partially by ROV-deployed equipment and partially from the rig deck, depending upon vessel circumstances, contractual allowances and drilling schedules.
