2. The inspection of the submerged portion of offshore oil and gas platforms and 

 other structures during and after installation for defects prejudicial to structural 

 integrity such as cracks and bent, broken, or missing structural members. 



Detailed inspection requirements for the vehicle documented in the EAVE program 

 plan (ref 2) are as follows: 



1. Pipeline Inspection Tasks. 



a. Conduct pre- and post-inspection mapping of areas of pipeline route to de- 

 termine its geographical coordinates and pertinent terrain characteristics. 



b. Initiate inspection by locating specified starting point on pipeline. 



c. Navigate along, or track, pipeline with precision required by onboard sensors 

 to perform their functions; the platform's maneuvering ability will permit 

 stopping, maintaining position (hovering), and retracing pipehne. 



d. Observe, by means of onboard sensors, irregularities in pipeline condition; 

 report these irregularities to a remote station and, upon command, perform 

 a more detailed inspection or move to a new inspection area. 



2. Offshore Structures Inspection Tasks. 



a. Locate structure, or a particular section of total structure to be inspected, 

 after deployment in the approximate area. 



b. Navigate so as to trace structural members with precision required by on- 

 board sensors to perform their functions; maneuvering ability will permit 

 stopping, maintaining position (hovering), and retracing a structural member 

 or network of members. 



c. Observe, by means of onboard sensors, gross structural irregularities and 

 defects; report these irregularities to a remote station and, upon command, 

 perform a more detailed inspection or move to a new inspection area. 



Environmental requirements associated with the inspection tasks may be summarized 

 as follows: 



Operating areas OCS of the United States 



Operating depth (max) 2000 feet (near-term goal); 6000 feet 



(long-term goal) 



Operating sea state (max) As limited by support vessel 



Current velocity at work site (max) 2 knots. 



It has been determined that the potentially most useful application of a fiber-optic 

 link in the offshore inspection scenario is that of pipeline inspection. In this application, 

 the submersible can deploy the Unk along a relatively straight run with relatively little 

 opportunity for entanglement of the Hne in the propellers or nearby features. Success will 

 depend primarily upon the ability to deploy the link reUably with little or no drag. 



A fiber-optically controlled vehicle for structures inspection promises to be signifi- 

 cantly easier to maneuver than a tethered submersible with the same mechanical configura- 

 tion and number of degrees of freedom. The stiff fiberglass-armored version of the fiber- 

 optic tether promises to be less prone to breakage as a result of entanglement in the structure 

 or with the vehicle propellers. 



13 



