the marine analyst Sea Trials of Diamond Offshore "Ocean Clipper" by Tom Johnson SNAME 1997

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1 the marine analyst SNAME 1997 Sea Trials of Diamond Offshore "Ocean Clipper" by Tom Johnson Scientific Marine Services, Inc. (SMS) attended and supervised the vessel sea trials for the Diamond Offshore Drilling Company vessel, Ocean Clipper. The extensive sea trials included maneuvering trials, propulsor shaft vibration survey and a hull vibration survey. During maneuvering trials several types of tests were completed including crash stops at full and half speed, turning circles to port and starboard at full and half speed, pullout tests and thruster effectiveness tests. The Ocean Clipper has some history behind her. She was originally built in the early 1950 s as a bulk carrier. She was modified to be a conventionally moored drillship in The upgrades completed in 1997 have modified the ship to be capable to drill in up to 7,500 ft of water. Stationkeeping is maintained through the use of a dynamic positioning system utilizing the main screws and six newly added thrusters. SMS sea trials crew at work on the bridge of the "Ocean Clipper" Due to these upgrades (sponsons, additional riser rack framing, thrusters, increased payload, etc.) surveys were completed to determine if the vibration characteristics of the vessel had changed. In addition, because the sponsons were added, the maneuvering characteristics were investigated to satisfy U.S. Coast Guard requirements regarding the Maneuvering Placard. This placard is required to be posted on the bridge of every ship operating in U.S. waters and must be updated if a ship undergoes major changes to its hull form. "Ocean Clipper" working offshore The sea trials were successfully completed in July 1997 and the vessel is now working offshore Louisiana for BP and BHP in their Neptune prospect.

2 President s Message by Frank DeBord It certainly seems as if more than six months have passed since the last issue of the marine analyst was published. Since then I have moved to Houston where we have moved into new office space, and everybody in Houston and Escondido has been busy on a wide variety of projects. The staff now includes sixteen people in Escondido and four in Houston. A number of ongoing projects are described in this newsletter. In Houston we are working on an Integrated Marine Monitoring System for the Marlin TLP, commissioning of the Oryx Spar Environment and Response Monitoring System and a number of model test projects being completed at the Offshore Technology Research Center. The California office recently completed a ship launch monitoring project for NASSCO and sea trials of the Ocean Clipper for Diamond Offshore. In addition, we are providing tow monitoring services for Chevron for three tows from Korea to Africa, an environmental monitoring system on the Ocean Victory for VASTAR, and several industrial control systems for a local pressure vessel manufacturer with factories in Escondido and India. Although is seems like most of our projects are now related to offshore oil exploration and production, the shipping industry and the civil engineering community are still providing a significant number of interesting projects. We continue to support nine tanker structural monitoring systems for BP Oil Shipping with data analysis, maintenance and upgrades, and we are looking forward to new tanker construction projects for several US flag operators. We recently assisted with the design of a new port in Korea and we are currently working on design of a Naval facility in Saudi Arabia and a harbor in Peru. Personally, the move to Houston is exciting because of the level of activity in the Gulf of Mexico. As described above, SMS has provided services for a number of projects including design evaluations in the model tank, transportation and construction monitoring, sea trials and design and installation of permanent marine monitoring systems. We hope that opening the Houston office will enable us to improve the level of service we provide to the offshore industry and be more responsive to clients on the East Coast and in Europe SNAME Annual Meeting October 15-18, 1997 Westin Hotel and Ottawa Congress Center Ottawa, Canada SMS will be exhibiting at the 1997 SNAME Annual Meeting and International Maritime Exposition in Ottawa, Canada. The theme for this year is New Frontiers in Naval Architecture and Marine Engineering." Featured in our booth will be the Hull Structural Monitoring System, Vibration and Ship Trials, Marine Instrumentation and Monitoring Systems as well as our Naval Architecture and Engineering Services. Please stop by our booth and visit us while you are attending the conference Booth: 611 2

3 SLNC-1 Launch Instrumentation by Rick Ashcroft and Bud Hennessy SMS is proud to have been involved with the launch of the "USNS Watson" at the National Steel and Shipbuilding Company (NASSCO) on 26 July This ship, at more than 950 feet in length and 28,000 LT (launch weight!), is the largest vessel stern launched in the United States in many decades. Obtaining detailed engineering information on large vessels during the launch event has rarely been attempted and launch calculations are performed using a combination of empirical and analytical techniques developed over the years. To obtain data which would allow the refinement of present techniques and provide enhanced launch calculations for the follow on class vessels which are being constructed, NASSCO contracted with SMS to instrument the Watson for the launch. Fore poppet strain gaged "USNS Watson" prior to launch It was desired to obtain as much information as possible about the position, velocity, and acceleration of the ship during the launch event. To provide this, a high accuracy differential global positioning system (DGPS) was obtained from the U. S. Navy. Three receivers aboard the ship were indexed to a fourth receiver located on shore nearby to provide three dimensional position accuracy within 1 centimeter. Also installed aboard the ship to provide back up to the DGPS system were three inertial navigation quality triaxial accelerometer packages and a solid state roll - pitch sensor. These systems provided high resolution position, velocity, and acceleration information during the launch event. In addition, an array of seven strain gages was placed on the deck to measure the strain during launch. To help precisely determine the point of rotation, all ten columns of the starboard fore poppet were also strain gaged. The data acquisition system, also provided by SMS, sampled all instrumentation data channels at 50 Hz. The DGPS system updates at 2 Hz and was recorded along with the other instrumentation data. Indexing was provided so that all information could be referenced to a specific time stamp. The result was a considerable amount of data which is virtually unique. Data analysis is now in progress and promises to provide a great deal of new information which will be helpful for future stern launches of large ships. 3

4 Wave and Sedimentation Modeling for Bahia San Juan de Dios, Mexico by Claudio Fassardi The entrance to a harbor, located in the Bahia San Juan de Dios on the Pacific coast of Mexico, suffers from the occasional appearance of 2-3 meter waves on otherwise apparently calm days. In combination with the shoaling of the entrance these waves break in the entrance and present a hazard to vessels attempting to enter or leave the harbor. During the first few years of existence of the harbor it was noted that shoaling developed in the entrance as a result of longshore sediment transport. The origins and magnitude of this transport had to be determined in order to evaluate the merits of alternative mitigation measures to decrease the sedimentation and therefore the severity of the wave agitation at the entrance. No direct measurement of the local wave climate was available and therefore numerical modeling was undertaken to determine the conditions that could produce the observed sedimentation and local wave shoaling. Average storm conditions were used in a numerical model to generate time varying pressure and wind fields. These fields were then used to generate time series of the offshore wave conditions using a time dependent, discrete, spectral model based on the energy balance equation. The typical waves generated in the storms were modified to determine local intensity by means of a linear refraction-diffraction model. Historical nautical charts dating back to 1945 and more recent aerial photographs were used to calibrate and verify a shoreline response model. Finally, use was made of this model in a comparative study of shoreline response and sediment transport rates with different proposed mitigation structures. Marine Monitoring System For "Marlin" TLP by Frank DeBord SMS has been awarded a contract by ABB Lummus Global Inc. and Han-Padron Associates, LLP to provide an Integrated Marine Monitoring System (IMMS) for the Amoco Marlin Tension Leg Platform. This system will monitor the environment and platform response and will display this information for operating personnel. Equipment provided by SMS will include the data acquisition and display system, weather instruments, a profiling current meter (ADCP), wave height sensors, a differential global positioning system receiver, and platform trim and heel sensors. Displays will also be provided for tendon tensions and drafts that are being measured using systems provided by other vendors. The SMS scope of work also includes a subcontract to Herbert Engineering to provide load management software on the IMMS computer. 4

5 SMS Supports OTRC Complete Model Tests of Mobil Floating LNG Plant by Tom Johnson Coastal & Marine Technology (CMT) assisted the Offshore Technology Research Center (OTRC) complete physical model tests of a floating LNG plant concept developed by Mobil. CMT is a subsidiary of Scientific Marine Services, Inc. This marks the 16 th major project in 4 years completed by CMT in association with the OTRC. Located in College Station, Texas, the OTRC is a National Science Foundation (NSF) Engineering Research Center which is a joint venture between the offshore oil industry, NSF, Texas A&M University at College Station and the University of Texas at Austin. The Mobil floating LNG plant is a concept to test the feasibility and effectiveness of a floating liquefied natural gas (LNG) production facility. The floating facility would be able to process gas and store the LNG within its hull. To meet the requirements of the process equipment, the floating facility must be very stable and have small responses to the sea. Utilization of this concept would eliminate the cost of running a pipeline to shore and building a land-based LNG facility for the project. A major benefit allows for when a field is depleted, the barge could be moved to the next site. The concept will be constructed from four rectangular barges. When assembled, a center moonpool will be created. Mobil LNG barge and offloading tanker The overall objective of the model test program was to provide motion characteristics to verify the calculated motions and to test several configurations to help the design engineers optimize the concept. Measurements of particular interest were the surge, heave, roll and pitch of the barge. Another concern was to investigate any sloshing that may occur in the moonpool at certain wave frequencies. The conclusion of the tests was that the concept was feasible and further preliminary engineering was warranted. Mobil LNG barge in quartering seas 5

6 SMS Becomes a Trimble Marine Survey Dealer This summer SMS became a Marine Survey Dealer for Trimble Navigation Ltd. We are now offering the complete range of survey and precision navigation hardware and software developed by the world leader in GPS (Global Positioning System) technology. Hardware products range from DGPS receivers that use government beacons for sub-meter precision navigation to high end centimeter accuracy differential systems. Software products include a ship trials package, softby Frank DeBord ware for completing hydrographic surveys and packages for precise positioning of structures and piles. All of these software products work in conjunction with the GPS hardware. For information on these products or questions regarding a specific application, please contact Frank in Houston or Claudio in Escondido. SMS Assists Bechtel and the Port of Los Angeles The Port of Los Angeles has replaced the old Badger Avenue railroad bridge (the rail link between the mainland and Terminal Island) with a new structure designed to handle the much heavier rail traffic generated by the expanding port facilities. How do you remove an old bridge? Float it off on barges, of course! But putting a structure on barges brings this Civil Engineering project into the realm of Naval Architecture. To assist Bechtel in support by Rick Ashcroft Bridge section heading to the scrap yard of the Port of LA, SMS was called upon to review and comment on the naval architectural aspects of the removal and installation plans. This included issues of stability and structures as well as review of the detailed evolution plans for both the removal of the old structure and placement of the new. This type of project provides a good example of how many fields of expertise must work together to complete a complex project safely. 6

7 SMS Provides Model Testing Services for Friede & Goldman, Ltd. by Rick Ashcroft Friede & Goldman, Ltd. have developed the JU-2000 concept for a jack up type drilling rig which utilizes an cantilevered accommodation structure. To assure that wave impact would not adversely affect rig operations during storm conditions and to obtain data for comparison with existing computer simulations, physical model tests were indicated. In support of this program, SMS provided turn key model test management, including model fabrication and contracting with the University of New Orleans Ship - Offshore University Laboratory to provide model basin services. The model was tested for calm water resistance in the transit condition and zero speed sea keeping for both head and bow quartering seas. A special test was conducted to determine the potential to broach if exposed to a specific sea state and simulated wind load. During the tests, data was acquired using a stand alone system provided by SMS. In this way, all resistance and motions data was readily available to SMS and F&G naval architects for post test analysis and report preparation. In addition, video tape records were taken by UNO, Friede & Goldman, Ltd. and SMS. These records were edited into a single final video by SMS. JU-2000 jack up, head seas setup JU-2000 jack up in a head seas test Use of the towing tank facility at UNO to perform these zero speed sea keeping tests was made possible by the use of a soft mooring system designed and fabricated by SMS. This system held the model within the test section of the basin while having a minimal effect on the motions. By utilizing a test facility close to the Friede & Goldman, Ltd. offices in New Orleans, it was possible for F&G naval architects to be directly involved with the test phase of the program. Data obtained from these model tests allowed the refinement of numerical tools developed by Friede & Goldman, Ltd. and will assist in the continued development of innovative offshore designs. 7

8 Welcome Aboard! John Fluck has joined SMS as Senior Mechanical Engineer. John has a B. S. in Engineering from California State University Fullerton. In the last 20 years, he has been involved in developing concepts and designs for single point moorings and hydrodynamic physical model tests. In addition, John has been involved in field installation of vessel structural and environmental monitoring systems. Armando Olvera recently graduated from San Diego State University where he received a Bachelor degree in Electrical Engineering. He is experienced in working with Motorola microcontrollers, infrared sensors and LCD displays. In addition, he is proficient in writing subroutines to communicate through serial ports and GPIB bus. Armando s programming skills include C/C++ and Assembly, LabWindows and LabView. Kirk Schumacher is a recent graduate from Florida Institute of Technology where he received a Masters degree in Ocean Engineering. His Bachelors degree is in Maritime Systems Engineering from Texas A&M Galveston. Kirk s student experiences fit well with the broad scope of services that SMS supply. Kirk has been involved in various activities which include physical model testing in wave flumes, field data acquisition and numerical modeling. Michael Stewart is a former Coast Guard Electronics Technician and has an Associate of Arts degree in Electronics. He has worked as a Technician at a Navy radio transmitter facility, installed shipboard equipment including TACAN, QUAD- DAMA and TESS-3 military navigation and communications equipment. Most recently Michael has worked as an electrician at NASSCO in New Ship Construction. 101 State Place - Suite N Escondido, California Phone: (760) Fax: (760) Meadowfern Dr. - Suite 122 Houston, TX Phone: (281) Fax: (281) Visit Us at SNAME 97! Booth 611 Inside: Sea Trials of the "Ocean Clipper" Model Testing at the OTRC and UNO "USNS Watson" Launching Instrumentation President's Message and more... 8