Underwater installation apparatus

1. An apparatus for deployment from a base for installing a component at an underwater facility, comprising a carriage lowered from the base in use of the apparatus, the carriage being adapted to releasably retain the component, a compensator located between the carriage and the base in use for compensating for relative motion between the underwater facility and the base, and a suspension cable for suspending the carriage from the base, wherein the compensator comprises a plurality of arms pivotably connected to the cable; wherein

the arms are connected to a resiliently deformable member; and

wherein the arms are pivotally connected together to define a parallelogram linkage having four pivot bearings, and the resiliently deformable member is connected between two of the pivot bearings.

2. The apparatus according to claim 1 , wherein the compensator is located between the suspension cable and the carriage.

3. The apparatus according to claim 1 , wherein the resiliently deformable member is a spring.

4. The apparatus according to claim 1 , wherein the carriage is provided with guide cables for engaging with the underwater facility.

5. The apparatus according to claim 4 , wherein the guide cables when engaged with the underwater facility provide a guide for locating the component at the underwater facility.

6. The apparatus according to claim 4 , wherein the compensator acts to keep the guide cables tensioned during installation of the component substantially regardless of said relative motion.

7. The apparatus according to claim 4 , wherein the guide cables are manipulable by a remotely operated vehicle to engage with the underwater facility.

8. An apparatus for deployment from a base for installing a component at an underwater facility, comprising a carriage lowered from the base in use of the apparatus, the carriage being adapted to releasably retain the component, a compensator located between the carriage and the base in use for compensating for relative motion between the underwater facility and the base, and a suspension cable for suspending the carriage from the base, wherein the compensator comprises a plurality of arms pivotably connected to the cable; and

wherein the carriage is provided with a retractable cable for engaging with the component.

9. The apparatus according to claim 8 , wherein the retractable cable is manipulable by a remotely operated vehicle to engage with the component.

10. An apparatus for deployment from a floating vessel for installing a component at an underwater facility, comprising:

a suspension cable adapted to be lowered from the vessel for installing the component at the underwater facility;

a wave motion compensator having first and second ends movable relative to each other between a retracted position and an extended position in response to wave movement, the first and second ends being biased toward the retracted position, the first end being connected to the suspension cable to allow the suspension cable to move upward and downward relative to the second end of the compensator in response to wave movement; and

a carriage connected to the second end of the compensator, the carriage having an engaging member that releasably retains the component with the carriage as the carriage is being lowered with the suspension cable toward the underwater facility.

11. The apparatus according to claim 10 , wherein the compensator comprises:

four linkage bars pivotally connected together in an arrangement having an upper pivot point, a lower pivot point and two lateral pivot points, the upper pivot point being the first end of the compensator and the lower pivot point being the second end of the compensator; and

a spring member connected between the lateral pivot points and urging them apart from each other.

12. The apparatus according to claim 11 , further comprising:

a pair of guide lines for guiding movement of the component from the carriage to the underwater facility, each of the guidelines having a first end connected to an opposite side of the carriage and a releasable coupling on a second end for connection to the underwater facility when the carriage is a selected distance away from the underwater facility, the selected distance being substantially the same as the length of the guide lines.

13. The apparatus according to claim 10 , wherein the engaging member comprises:

a winch mounted to the carriage;

a deployment cable wound around the winch and having a free end for connection to the component.

14. The apparatus according to claim 12 , wherein each of the couplings has a storage position releasably connected to the carriage, defining a loop for each of the guidelines while the carriage is being lowered toward the underwater facility.