Sponsored by the Naval Facilities Engineering Command, NEMO was the first submersible with a nonmetallic pressure hull to be approved by the U.S. Navy for manned service. The NEMO submersible was designed to be a one-atmosphere underwater observatory for 600 ft depth with lateral and vertical mobility. Lloyd’s Register has classed the DeepFlight Super Falcon 3S in accordance with its Rules for the Construction and Classification of Submersibles and Diving Systems. First Composite, Personal Submarine Classed by Lloyd’s Register Subsea Intervention & Survey News.
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Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Suggested Citation:'CHAPTER 3: TECHNICAL ASPECTS OF SYSTEM DESIGN.' National Research Council. 1990. Safety of Tourist Submersibles. Washington, DC: The National Academies Press. doi: 10.17226/1744.
Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages. 3TECHNICAL ASPECTS OF SYSTEM DESIGNThis chapter provides an analysis of the present design, construction, and inspection standardsutilized with regard to tourist submersibles. In the case of inspection practices, relatively detailedsuggestions are presented for the development of a periodic inspection program specifically for these vessels.The life support systems and emergency rescue equipment aboard these submersibles are also reviewedbriefly in this chapter.DESIGN AND CONSTRUCTIONCompared to workboat DSVs, the technologies employed for the metal-hulled tourist submersiblesare conservative and fairly simple. These vessels are shallow diving (30-50 meters, or 98-164 feet), do notrequire elaborate operational equipment, and have short mission times. The major differences, whencompared to submersible workboats, are the need for adequate life support, emergency equipment for arelatively large number of people (30-50), efficient and safe means of loading/unloading passengers, and theneed to withstand a much larger number of dive cycles. Also, the interior of the submersible must bedesigned from both a business and safety standpoint to provide the passenger with maximum comfort, goodviewing opportunities, and a relaxing interior design.A major consideration in design and construction is that these assets will probably have anoperational life of 20-25 years. Consequently, the hulls will have the highest number of diving cycles ofany submersible built as they potentially pass through the hands of many owners. Initial design shouldtherefore take into account a long service life as well as simplicity of maintenance and operation.From a safety standpoint, the emphasis in construction must also be placed on reliability. Highlyreliable methods of construction lead to successful and, hence, safer operating systems. Methods ofconstruction' should be construed to encompass both materials and vehicle fabrication processes.As described in Chapter 2, the major classification societiessuch as the American Bureau ofShipping (ABS), Lloyd's Register, and Det norske Veritas (DnV)have each established rules for the designand construction of steel-hulled submersibles. To date, all but two tourist submersibles have been built toABS class, and ABS has the only set of classification rules the Coast Guard recognizes for submersibledesign. In addition, the American Society for Mechanical Engineers (ASME) has published standards forpressure vessels for human occupancy (PVHO). ABS and the Coast Guard both recognize ASME's standardfor PVHO as a satisfactory standard for man-related undersea pressure hulls.*These submsersibles generally operate in waters where bottom depth does not exceed design operating depth.19 20The present ABS rules make no major distinction between commercial work submersibles and thoseused for tourist service. Therefore, there have been few difficulties in classing the limited number of steel-hulled submersibles specifically designed and built for tourist service. ABS is currently revising its rules toadd provisions for tourist submersibles.For main pressure vessel (MPV) design (and hence fabrication), ABS will approve designs basedeither on ASME for PVHO formulas (Section VIII, 1 or 2), or on ABS' own design formulas, which arebased on Windenburg's critical buckling formula.7Design factors of safety (f.o.s.) compare the actual design stress to the yield stress (strength) of thematerial used. For example, for an f.o.s. of 1.5:1,Material Yield Stress = 1.5Actual Design StressAn f.o.s. of 3:1 or 4:1 on the material's yield stress is used in PVHO design based on ASME standards,while classification societies such as ABS will accept a minimum of 1.5:1 on the yield stress. The criteriaand factors used depend on the designer.8 Also, the method by which ABS inspects the hull during andafter fabrication varies with the design philosophy. For example, if an MPV is designed to PlIHOstandards, ABS does not require strain gauging of the hull during its hydrostatic (drop) test.The question concerning the choice of the f.o.s. for submersibles raises complex engineering designissues and variables, such as operational depth limitations related to the capabilities of emergency responseand the operating environment for a design, as in the case of military submersibles. The committee viewsthe choice of the passenger submersible f.o.s. as an engineering design issue of concern to both the CoastGuard and the classification societies, but outside the scope of this study.MaterialsTo date, nearly all MPVs have been built using steel (either ASTM A516 or the equivalent). Theimplications are positive, since the specifications for steel are well documented, as are the weld proceduresrequired for fabrication. This experience base with steel tends to enhance reliability.However, some cautions are in order, particularly in regard to stainless steel. Stainless steel (e.g.,Type 304 and Type 316) is used extensively in critical systems, including the oxygen system, the compressedair systems, the ballast systems, and all hull penetrators. Some stainless steel formulations have been shownto be susceptible to both stress corrosion cracking and crevice corrosion cracking.9 In the submarineenvironment, where these systems are continually exposed to salt water, both of these forms of attack onthe material can occur. Some austenitic stainless steels (Fe-Cr-Ni-Mo alloysy, which are highly corrosion-resistant, have been used with a high degree of success in marine applications~°~lthough not yet insubmersibles. Other materials that are more suitable for this application are the mild steels, theinconel/monel/copper-nickel alloys, and several types of titanium. While titanium is more expensive thanother more commonly used materials, it may be cost effective.Aluminum ___= ~ ~ ~ ~ A ~ ~ ~ A_ ~ ~ ~ ~ ·^_ _~ ~ ^ ~ ~ A ~A A · JUtilization of other types of material for the MPV presents additional problems. Aluminum is thesecond most popular choice for submersible construction material; but, depending on the series of aluminum*In the drop test, a hull is lowered in water to 1.25 times the design depth for 1 hour to test its capacity to withstandhydrostatic pressure.**W. W. Kirk, International Nickel Laboratory, personal correspondence with C. M. Jones, October 1989. 21selected, it may prove problematic with respect to its weldability. The soon series aluminums, such as 5083or 5456, are excellent materials in the pre- and post-weld condition. This series has not indicatedsusceptibility to early onset of stress and fatigue or cracking in the heat-affected zones in the material oneither side of the welds. Series 6000 and 7000 aluminums are quite the opposite. Due to its availabilityand corrosion resistance, 6061-T6 has been utilized extensively in the submersible industry, bothcommercially and by the U.S. Navy (with disappointing results). The post-weld condition of the materialin the heat-affected area has exhibited tendencies to crack under stress levels far below those predicted.This problem has been brought to the forefront by the Naval Sea Systems Command (NAVSEA),which has issued instructions that 6061-T6 will not be used for structural purposes when it must be weldedwithout first being reviewed on a case-by-case basis. It is noted that the ABS allows a maximum stress of9,000 psi for 6061 aluminum, versus the 8,000 psi the U.S. Navy allows for repair work on existingstructures. NAVSEA's requirement for specific case-by-case technical review does seem prudent andpresumably would be mirrored by the Coast Guard and ABS in their review processes.AcrylicsOther candidate materials include thermoplastic materials such as acrylic. Acrylic spheres have beenutilized on five submersibles to date. The thickness required for the Johnson Sea-Link submersibles' newspheres has been increased from 4 in. to 5 in. by ASME's PVHO. The original spheres were designed witha 20-year life expectancy but showed signs of failure within 15 years of service. This problem is a particularconcern with plastics or composite materials utilized as pressure vessels subject to external (hydrostatic)pressure.To date, three manufacturers have presented designs utilizing acrylic for the MPV. However, theclassification societies have not established rules governing design, construction, and testing of this type ofhull. To further compound the problem, HYCO Technology's ARIES, SEA VIEW, and COMEX's proposedSEABUS are proposed as cylindrical (not spherical) pressure vessels. No relevant test or operationalhistories exist here, since the history is based entirely on spherical shapes such as the U.S. Navy's NEMOsubmersible or the Johnson Sea-Link research submersibles.If large area or extensive use of acrylics as a principal structural material is to be approved andrules for it written, the analytical and testing work will have to be contracted and paid for by theorganization requesting the rules. It will be expensive and might require test-to-failure of a full-sized hullsection, as well as development of extensive fatigue data. Even if acrylic hull standards are developed, thepotential market for this type of submersible may be greatly diminished by the time this can beaccomplished. Me best operating locations may be already taken by steel-hulled submersibles before thefirst acrylic hull submersible enters tourist service.There is another related problem with immediate significance. Present rules, based on PVHOstandards, call for replacing all acrylic viewports after 10,000 diving cycles or 10 years in service (unless apotential designer/fabricator can demonstrate, via testing, that either or both criteria should be extended fortheir application). At an average cycle rate of nearly 2,000 dives per year, the viewports would have to bechanged after 5 years. (Private research is being conducted by Sub Aquatics to extend the time periodspecified by those rules.) If the 10-year or 10,000-cycle requirement were extrapolated to massive acrylichulls, the entire hull would have to be replaced. This cost factor alone might be reason enough to stopany further consideration of this hull material.The classification societies and the certificating agen~the Coast Guardmust be specifically carefulto ensure the adequacy of design and particularly cautious in their interpretation of test data, since theARIES, SEA VIEW, and SEABUS (Comex) applications break new ground in the utilization of acrylicmaterial. As noted earlier, materials such as steel, with an extensive history of use in these areas, exhibitLetters from Commander NAVSEA to Lockheed Advanced Marine Systems: paragraph 2, letter dated May 17, 1985; andparagraph 4, letter dated April 1, 1988. 22their individual weaknesses in ways that are well understood; newer materials such as acrylic or compositematerials will likely exhibit new problems. For examples some experts ascribe little validity to scale modeltesting of acrylic hulls, believing that acrylic does not scale representationally.A U.S. Navy technical expert has suggested to PVHO that designers and builders of acrylic-hulledtourist submersibles build a minimum of two scale models (approximately 1/4 or larger) for testing. Underthis proposal, one model would be tested to destruction to validate the design calculations. The secondmodel would be subjected to the maximum number of pressure cycles that can be withstood through itsdestruction. In this context, a pressure cycle would replicate a dive cycle. The maximum number of cyclesderived from the test would then be used to determine the replacement interval. In contrast to the opinionmentioned above, this expert believes that acrylic scales very well, with scale effects being reasonable. Thesecontrasting views simply reflect the lack of wide experience with these materials and the uncertainty facingthe regulatory agencies.Flammability ConsiderationsThe selection of materials associated with electrical equipment and wiring and the interior of thesubmersible should include consideration of flammability properties, including ease of ignition, flame spread,and composition of combustion products. The design should proscribe the use of materials that exhibit lowflash or fire points. In addition, any potential fire should be restricted to minimal, well-defined, isolatedareas within the submersible without propagation paths. Material selection should minimize the toxic hazardassociated with combustion products.A National Aeronautics and Space Administration Handbooks provides criteria governing materialsselection, evaluation, and control. The Coast Guard will find this handbook useful as a guide.StructureThe predominant method of hull construction used in U.S. operational submersibles is to reinforcecylindrical shell sections with external ring stiffeners. The rules for designing main pressure vessels usingring stiffeners are well known. The external ring stiffener approach maximizes the internal volume availableto passengers without sacrificing the additional strength required for the stiffeners. Some European designsoffer a variation by allowing the stiffeners to penetrate the continuous shelf plate. In the touristsubmersibles observed by the committee, the stiffeners did not penetrate through the cylindrical shell. Itis well that they did not. Such penetration could present numerous problems with regard to maintaininga true cylindrical cross-section, and allowable local deviations from circularity could be exceeded. Additionalproblems presented by allowing stiffeners to penetrate the MPV shell occur in welding. The number ofwelds in the MPV would increase by a factor of two (at the minimum) with penetration. This doubles thepossibility of failure due to poor welding, shell pressure cycle. fatigue. early onset `,f hil~klina Or ae.ner~1instability.Materials selection is also crucial for maintaining structural integrity. For example, 6061 aluminum,which is susceptible to cracking after heating, is widely utilized as exostructure material for touristsubmersibles. The exostructure is the framing around the MPV that supports the superstructure (deck andconning tower) and encloses the ballast tanks. When the tourist submersible surfaces to unload and loadpassengers, there is always contact (impact) with its tender vessel (the ferry boat). Depending on wind andwave action and the relative position (to the ferry boat) of the submersible when it surfaces, the impactforces can replicate minor collisions. It is possible that a collision during operations could exert the forcerequired to buckle the submersible's exostructure and, through it, deform the pressure hull. The damagemight appear minor during a visual inspection, but could be more critical in reality. ~ ~ 7 ~ ~ ,7 ~7^ a_ ._. a.*Dr. Jerry Stachiw, Head, Materials Technical Staff, Naval Ocean Systems Center, San Diego, CA (personal correspondence). 23If the exostructure, as it collapses, damages the shell of the MPV by causing it to deformpermanently, catastrophic failure is only one step away. With a permanent set (deflection) in the MPVshell, the circularity of the shell is compromised. If the dimensional irregularity caused by this impact isgreater than the percentages allowed by classifying agencies, a classical buckling failure could occur if, forinstance, the submersible were to dive to a depth close to its design (or operating) depth. The amount ofallowable deviation from the design diameter (or dimensions) is small; ABS allows 1.0 percent of the designdiameter.This possibility, coupled with various construction methods (e.g., some European designs) placesspecial emphasis on the need for close inspection during annual surveys. At present, ABS rules state thatduring special surveys (done at approximately 3-year intervals) the surveyor Could call' for criticaldimensional checks. Since tourist submersibles are drydocked on land during mandated surveys every 18months and are basically disassembled for inspection, it would be a relatively simple task to check the hullcircularity and verify that it is within the allowable limits.Pressure CyclingTourist submersibles operating in resort areas such as Grand Cayman and the Virgin Islands canaverage 6 dives per day, 6 days a week. This yields a total of 1,872 cycles per year, which is an extremelyhigh number compared to experience with work submersibles and Navy deep submergence rescue vehicles(DSRVs). Military and industrial submersibles would not see that number of cycles in their lifetime. Forexample, the two U.S. Navy DSRVs average less than 100 dives (cycles) per year.Increased pressure cycling causes structural fatigue to appear at earlier stages than the expecteddesign life. This was evidenced by an Aloha Airlines 737, which lost its forward cabin roof inflight in a1988 accident. Because these aircraft island-hop, they undergo a higher than average number of pressurecycles during their operational life. The same case can be made for submersibles. In this connection, itis noted that ABS requires only 1 or 2 cycles of hydrostatic testing, while the Naval Sea Systems Commandrequires a minimum of 10 cycles. While such testing is adequate to verify basic design parameters, it doesnoteven at 10 cyclesaddress the fatigue problem. Increased cycling in operation will eventually lead tofatigue failures, which emphasizes the need for intensified inspection and testing of vehicles that have beenin service for several years.There is a sufficient data base on steels to predict performance with a given number of pressurecycles. I~here is not an adequate data base for predicting performance of new materialsparticularly acrylics.Redundant and Backup SystemsThe safety of a system is partly a function of its reliability; that is, that the subsystem or componentwill be available and operate on demand. System reliability, in turn, can be partly a function of systemredundancy or backup availability. While a less than perfect subsystem or component operational reliabilityis usually acceptable in the commercial working industry where human safety is less at risk, the touristsubmersible industry requires a significantly higher reliability for each subsystem. This can be achieved onlyby having a substantial reserve or a dedicated emergency backup system.Strict redundancy is accomplished by duplicating critical components, such as with an extra set ofgauges, communications gear, and secondary sources of compressed air that are directly accessible. Othersystems may be provided with a backup capability different in design from the primary system. For example,there is a requirement to carry sufficient solid ballast (usually lead or concrete) to be utilized as dropweights. This is needed in the event that the submersible is grounded by flooding of its largest pressurevessel, aside from the main personnel capsule. The drop weight system on one submersible visited by thecommittee (ATLANTIS class) is activated by a hand-driven hydraulic pump, and this activation arrangementmay be common to other tourist submersibles now in operation. In current designs that were observed,there is no provision for a backup in case the hydraulic pump fails. Further, the system can be activated 24only from inside. Other methods of drop weight release, utilized in work submersibles, are pyro-ignitedlinks, cable cutters, etc.The committee observed that the drop weight system on ~ . . . . . . . ., v , the ATLANTIS submersible was notactually tested in situ; that is, the weights were not dropped. Since the first response to an emergencyduring diviners pointed out to the committee by several operatorsis to surface immediately, the abilityto release ballast rapidly is critical, either as water blown out of tanks or as release of weights. Full testingof the drop weight system at sea in at least one vessel of each class would provide significant improvementin safety assurance. In addition, further assurance would be provided by having a manual backup fordropping the weights from inside the vessel. In submersibles whose operating depth is 150 feet or less, thedrop weight system should also incorporate a feature that allows divers to jettison the weights from outsidethe hull.StabilityIf a tourist submersible grounds due to a system failure and the drop weights must be jettisoned,the Coast Guard does not specify a minimum required stability. The minimum stability required to recovera submersible in its normally upright (trim) attitude is governed by the Metacentric Height (see AppendixA). For a submersible to remain upright while submerged and thus exhibit positive stability, the center ofbuoyancy must be vertically located above the center of gravity while submerged (see Appendix A, Enclosure2, Figure 1~. The center of buoyancy can be below the center of gravity while the submersible is on thesurface if the Metacentric Height is positive. Stability is an important parameter; its adequacy could beverified in a simulated (test) emergency ascent. The test envisioned would both test the ability of the dropweight system to function properly in water and verily that the stability required is adequate to guaranteethat the attitude of the submersible during recovery is upright and not severely inclined. Emergency trimcontrol could also compensate for the possibility of unusual loading in case of an event that would causepassengers to retreat to one location in the hull, and a simulated test could include this loading variable.Quality ControlWhile the submersible construction observed by the committee was conducted with quality control(QC) standards, it is essential that requirements to assure quality standards be established and maintainedfor the industry as a whole. QC standards and detailed documentation are important for ensuring safety.Based on site visits and observations, the committee is concerned about the present level of recordkeepingby the manufacturers. The Coast Guard should formalize the QC system, establishing what records mustbe kept and who should to keep them.Conclusions and RecommendationsRegarding Design and ConstructionThe method of tourist submersible design used within both the domestic and international industryis still maturing; hence, there are inconsistencies in industry design standards between those of thecertification and classification agenciese.g., factors of safety utilized in pressure vessel design, designparameter terminology, extent of data required during post-construction hydrostatic tests, and selection ofmaterials used.The Coast Guard should reevaluate the areas of inconsistency with ABS (indicating a lack of adequatedefinition) that exist in tourist submersible design procedure, material selection, and testing. Discussions betweenABS, Lloyd 's Register, and DnV could be of value in the course of the Coast Guard 's assessment. 25System redundancy is prevalent in most designs. In one notable exception however, the drop weightsystems, which are critical in the event of a pressure vessel (non-main pressure vessel [MPV]) flood, didnot have a backup externally operable release on the vessels, the committee observed.The drop weight system for each submersible design should be tested in sim by vessel designer andmanufacturer. The simulated emergency ascent test should account for the possibility of passenger overloadingin one area of the submersible.The present main pressure vessel (MPV) design used for tourist submersibles in service in theUnited States uses a ring-stiffened cylinder where the stiffeners do not extend into the pressure vessel.Submersibles that use other MPV designs may become available for use in U.S. waters. In some cases thesesubmersibles may utilize stiffeners that penetrate the MPV shells imposing additional strength andmaintenance problems. This potential concern places greater emphasis on inspecting and maintaining hulldimensional accuracy.To ensure that structural failure due to shell buckling or general instability does not occur from eitherrepeated impacts (collisions) with the submersible's tender .(feny boat) or because of problems inherent withdesigns that allow stiffeners that penetrate the main pressure vessel, greater emphasis should be placed on post-constn~ction inspection and critical dimensional checks during 18-month surveys. Special attention should begiven to symptoms of fatigue. Failure in aging submersibles also should be a part of the survey.There is a serious lack of information on the performance of acrylics in repetitive loading such asis experienced on tourist submersibles.Expanded testing is needed to validate design cntena. This testing should be done by the designer ormanufacturer proposing to use acrylic materials to the extent that they may pose signif cant questions about theintegrity of the main pressure vessel. Both the Coast Guard and ABS should provide guidance in the planningand conduct of such tests.LIFE SUPPORT SYSTEMSAir Supply/RegenerationABS rules require that the onboard air system be sized for 72 hours plus a normal dive.) Thenormal dive is usually counted as one full day. Adequate overcapacity in air required to blow the ballasttanks and in onboard battery capacity (for emergency power) is required and was built into the systemsobserved by the committee.Air tank capacity for blowing tanks must be adequate for at least the number of dives projectedbetween recharging opportunities. In addition, some excess should be provided for emergencies. This airprovides the primary means of returning to the surface. The air system design (valves, strainers, etc.), aswell as total capacity, therefore merits special attention.The onboard carbon dioxide (CO2) scrubber system (Soda Sorb and blower motors) is essential inmaintaining the quality of the air. According to ABS rules, the allowable CO2 limit is 0.5 percent of gross.Redundancy is provided by arranging alternative circulation patterns in the event of scrubber system failureand by providing extra capacity for scrubber reactants. Adequate sizing in the basic scrubber designs isessential; this capacity must be tested and any deviation from classification requirements observed andrectified. A problem of this nature was evidenced during a joint Coast Guard and ABS inspection of atourist submersible in Guam on April 6, 1988. In that case, the CO2 level during the second scrubber test 26was greater than 0.5 percent (due to improperly installed fans); but the result was approved based on firsttest results that were less than 0.5 percent.Fire SuppressionFire suppression in confined spaces, where humans are present, is difficult. Heat build-up is veryrapid, especially with closed hatches, in which case the temperature can pass 100°C in less than 40 seconds.Under these conditions, smoke rapidly obscures v~sibilin,r, hindering both fire-fighting and escape. Carbonmonoxide (CO) is also an immediate problem, as it affects decision-making capability long before it affectsmotor functions. The present Coast Guard requirement is simply for an approved, portable fire suppressionsystem. The current systems in use on submersibles are an interim response in the absence of a specifiedfire-suppression system.The requirement for a fire suppression system illustrates a problem in that all the available optionshave various safer and health concerns associated with them. For example, use of the gas Halon iscurrently the prevalent method; the ATLANTIS class of submersibles uses Halon 1301 as a fire suppressant.This gas is effective for the purpose but has several drawbacks, including decomposition resulting in acidicbyproducts, limitations on breathability for humans (10 min. at 6 percent maximum), and the fact that theHalon cannot be removed by carbon filters. Despite these deficiencies, Halon 1301 is the best availableshort-term fire-suppression alternative when the time to surfacing is only a few minutes. Halon is afluorocarbon and for that reason will probably be phased out within a few years.- The committee noted that nitrogen is an alternative fire suppressant currently under study by theOffice of Naval Research and the Naval Research Laboratory. Nitrogen is nontoxic and merits considerationas the primary fre-suppressant gas. Like other alternatives, nitrogen has inherent control problems and willrequire highly engineered control systems.Emergency Breathing ApparatusAnother illustration of the differences and complexity of submersibles compared to surface vesselsis the need for emergency air purification or air supply. ABS rules for submersibles require emergencybreathing life support for the duration of the dive or two hours, whichever is longer. (In the case of touristsubmersibles, the two-hour requirement pertains.) Currently there is no Coast Guard standard for devicesto meet this need.There are two aspects to the problem of emergency breathing apparatus: viz., providing emergencybreathing for the passengers and crew (pilot and attendant). Emergency breathing requirements forpassengers, in the event of a hire or loss of power with attendant failure of the air regeneration system, areusually met via individual units. One builder examined by the committee elected to solve this problem byproviding an MSA (Mine Safer Appliances Company) rebreather device designed to remove carbonmonoxide by oxidation and with the ability to remove certain other particulate materials via a filter. Thedevice does not, however, remove other contaminants besides CO and will not support life if oxygen levelsare too low or if for any other reason the atmosphere itself will not support life.The crew is provided with a full face mask, air fed, so that they breathe off the high-pressure airsystem. Thus, they have a life support system that will last as long as there is high-pressure air.The MSA self-rescuer may well be the best available solution to the problem of emergencybreathing for passengers in the event of a hire. However, since the device does not provide air, it does not*Rapidraft Letter from Commander USCG Section Marianas to Commander USCG Washington, DC, April 19, 1988,regarding the completed quarterly control verification exam of the MARIEA I submersible.**This is a problem of much broader scope than tourist submersibles, as Halon is used as a fire suppressant on many vessels. 27appear to satisfy the rules as they exist at this time. The alternative of using air-fed masks for passengerspresents a problem of pressurization of the compartment; sufficient exposure to the pressurized atmospherewould require passengers to be treated for decompression upon rescue, although this would not be aproblem if the submersible is able to execute the prescribed emergency ascent to the surface within aminute or two. Also, air-fed masks are not portable, perhaps making evacuation of passengers on thesurface more difficult.This issue needs further attentionparticularly as to whether the MSA rebreather meets both theletter and intent of the ABS rules. Perhaps the most troubling possibility is the risk of fire. Theatmospheric contamination in such an event is extreme and creates an immediately life-threatening situation.Therefore, every possible precaution must be taken to avoid fire, to minimize the toxic byproducts of anyfire should one start, and to provide a breathing apparatus that will protect every passenger from inhalingtoxic contaminants and smoke.Personal FlotationFinally, the committee observed that the inflatable life jackets used on ATLANTIS are not CoastGuard approved. Indeed, the Coast Guard has not approved any inflatable life jackets for such service, inpart because no user has been willing to pay the cost of testing and approval. (Noninflatable jackets arenot compatible with the storage and access constraints of submersibles.) The use of inflatable jackets inthis context is in line with airline practice, and while not specifically approved for general use they havebeen accepted in current submersible operations. Moreover, aircraft-type inflatable jackets lend a familiarityderived from air travel and therefore may provide some psychological benefits in understanding andaccepting their presence and use. This approach to personal flotation is compatible with an operatingprofile in which an attending surface craft is present at all times.Conclusions and RecommendationsRegarding Life Supportproblems.The gas Halon, used in current fire-suppression systems, presents possible safety and healthBecause nitrogen gas is nontoxic, consideration should be given to the development of a nitrogen-basedfre-suppression system, as a possible replacement for the Halon-based systems.There is an indication that CO2 absorption systems (scrubbers) used on some tourist submersibleshave occasionally been unable to maintain CO2 below required levels. These systems either lacked sufficientcapacity or were incorrectly installed; these deficiencies were overcome by reversing the airflow pattern.The Coast Guard should require that CO2 absorption systems have adequate capacity and redundancy,in accordance with a hazards analysis, and should enforce this requirement in design and periodic inspection.Failure of this system could result in injury or fatality to passengers.The current rebreather devices for providing emergency air supply for passengers do not satisfy ABSrules and are not adequate protection against some types of atmospheric contamination.The Coast Guard, in cooperation with ABS, should promulgate standards on emergency breathingrequirements and systems for tourist submersibles. All participantskoast Guard, ABS, and the users-shouldagree on the application of those rules. 28Inflatable life jackets used aboard tourist submersibles are not Coast Guard-approved, although theCoast Guard is currently accepting them.The Coast Guard should consider testing and approving one or more inflatable life vests.INSPECTIONThe U.S. Coast Guard routinely conducts periodic inspections of surface vessels to ensurecompliance with safety and pollution abatement requirements as defined by Coast Guard regulations. Theseinspections are conducted by personnel at the local level. They are effective because of the knowledge andtraining of the inspectors and because application of the rules results in similar systems and equipment onmost vessels. Years of experience with surface ships has allowed the Coast Guard to develop an inspectionprogram under which the local inspectors are sufficiently knowledgeable to work directly between the rulesand the hardware without interpretation difficulties.Inspection of tourist submersibles is not so straightforward and routine because of the relativenewness of these vessels and the relative lack of experience with them on the part of Coast Guardinspectors. A number of vehicle inspections take place at different stages in the life of a touristsubmersible. They include: construction and post-construction inspections; periodic certification inspectionsand reinspections; and quarterly control exams (for foreign-built vessels).Construction InspectionDuring MPV construction, which could last 2-3 months, the classification society is on-site weekly.In addition, spot (surprise) inspections occur at random intervals. Almost every inspection taking placeduring construction includes participants from both the Coast Guard and the classifying society (e.g., ABS).This phase of construction is critical, since the main pressure vessel is the single most important structuralcomponent of the submersible. The entire construction (or assembly) period could last as long as 12months. The final assembly (after all subsystem components are assembled) takes 5-6 weeks. During thevehicle construction period there are 25-40 inspection visits. When Coast Guard personnel are not availablethey will utilize the information gathered by the classification agency.Among the MPV tests witnessed or performed are critical dimensional checks, material tests,hydrostatic tests, and functional tests. Before the hydrostatic (drop) test is done, radiographic and ultrasonictesting is performed. After the hydrostatic test, ABS performs another dimensional check and non-destructive inspection (dye penetrant and magnetic particle) examination of all welds to ensure compliancewith the specified procedure.Periodic InspectionsOrganized periodic inspections are an important aspect of maintaining safety in tourist submersibleoperations. In general, all vessels carrying passengers must have on board a valid Coast Guard certificateof inspection (COI). A COI is issued by the cognizant Coast Guard Officer in Charge of Marine Inspectionafter an inspector has examined the vessel and determined that it is in satisfactory condition and fit for theservice for which it is intended and that it complies with the applicable regulations. (This is the'certification' process described in Chapter 2.)A COI for small passenger vessels less than 20 meters (65 feet) in length (all . . ~ . . .~ , =, `~ existing touristsubmerses are In this category) is valid for three years. At least two reinspections must be made withinthe triennial period. When possible, these reinspections will be made at approximately equal intervalsbetween triennial inspections for certification. 29ABS also conducts annual and special surveys of tourist submersibles. During the annual surveysthe hull is usually examined for significant damage. The air and hydraulic systems are inspected, the vesselis repainted, and the superstructure is repaired. There is no requirement in ABS rules for a criticaldimensional check, although special ABS surveys that occur every three years 'could call' (according to theguidelines) for such checks. In the committee's view, annual and special surveys should include dimensionalchecks to confirm the roundness or circularity of the MPV.Tourist submersibles represent a new challenge for the Coast Guard inspection system. Althoughthese vessels have much in common with surface craft, the major differences may mean that the expertiseof local inspectors could be insufficient to ensure adequate periodic safety reviews. Como instalar office 365 personal. In addition to theunique aspects of submersibles as a group, it is also reasonable to expect substantial differences betweenthe designs of various manufacturers. In time, some level of standardization is likely to occu~particularlyin safety-related areas; but at present, each vessel could meet the regulations in different ways, so that avalid inspection may require detailed design knowledge on the part of Coast Guard inspectors beyond whatthe present system provides.The U.S. Navy's deep diving submersibles and saturation diving systems present a similar situation.Inspection and certification of these facilities are done by a specialized group of auditors backed by a second_ r _ _ ~ at ~ _ · ~ i. ~ ~ ~ _ ~ ~ . ~ ~ . .~ ~. · , _group ot specialized engineers. Inspections by local personnel are conducted but they are preliminary toa visit by the NAUSEA 92Q Certification Audit Team from Washington, D.C. This procedure works wellfor the Navy, but is contrary to the Coast Guard's proven local inspection procedure.Continuation of local Coast Guard inspections appears desirable and reasonable since localinspectors can provide information about the local operational environment. The use of local Coast Guardinspectors can be satisfactory if the inspectors can be given adequate information on the submersible to beinspected to make the transition from the regulations to design and operational details. The participationof Headquarters personnel expert in submersibles (possibly with input from Marine Safety Center personnel)would ensure that effective, thorough inspections were made.The current inspection procedures appear to be adequate to maintain safe operations on systemsthat are essentially new. The committee has reviewed extensive experience with Navy-controlled deep-diving systems and several research submersibles and has developed an outline of inspection requirements,which is intended to help the Coast Guard and ABS in their review and development of their respectiveinspection procedures, as tourist submersible operations expand and become more routine.In brief, the committee believes that the designs of tourist submarines and their method ofonerntion are Ninny enc,~oh to retire rletnileA knowle~lne an the nart of an in~nector to ensure anadequate safety review. Flus requirement can be met by providing a detailed inspection plan generated aspart of the initial approval process and encompassing the program's equipment, operational procedures, andtraining programs. The inspectors should rarely be required to make technical judgments. Instead, theinspection plan should contain the necessary pass/fail criteria for each approved item or system. Thespecific points and criteria contained within the inspection plan should be derived from a formal hazardanalysis (see Chapter 4~.As with the initial system approval, periodic inspections represent a major effort on the part ofboth the Coast Guard and the operators. Great care must be taken to limit the inspection criteria to thoseitems and procedures of real importance to the safety of the passengers and operational personnel. Inaddition, operational inspections should be part of the inspection protocol. Inspections conducted whilethe vessel is moored at the dock on the surface capture the vessel in a passive mode; an active operationalmode is more indicative of the actual status of the vessel.The committee's suggested inspection plan is described in greater detail in Appendix B.For foreign-built vessels, which are outside the Coast Guard certification procedure, quarterlycontrol verification exams are conducted jointly by the Coast Guard and the classifying agency. The CoastGuard issues a certificate, CG-4504, Control Verification for Foreign Vessels to those foreign vessels itfinds to be in compliance with SOLAS regulations.This form of inspection is essential for determiningwhether the vessel maintains its classification or certification. Because the SOLAS regulations for passengervessels apply to ships on international voyages, their applicability to submersibles (which do not make such 30voyages) is highly questionable. However, they do provide the agencies with a means of spot-checking thesubsystem effectiveness and reliability of foreign-built vessels.Conclusions and RecommendationsRegarding InspectionInspection, both initially during construction and then continually throughout the operational lifeof the vessel, is extremely important for ensuring the safety of passengers and crew.The inspection plan for a given class of submersible should be defined ear) in the design phase, withconsultation taking place among the Coast Guard, the classif cation society, and the prospective operator. Thedevelopment of inspection plans and criteria should be based in large part on the results of a formal hazardanalysis (see Chapter 4).Continuation of local Coast Guard inspections appears desirable and reasonable. Howeverinspectors need to have detailed technical information and knowledge regarding the specific class and Inthey are inspecting. The inspection plan can provide much of this information. ~ ~ . At, .Personnel from Coast Guard Headquarters and the Marine Safety Center should be available to provideadditional in-depth fantiliari~ with tourist submersibles systems and operations.The inspection protocol should include functional tests of critical systems, which must first be definedin the inspection plan. Hull circularity is considered to be an essential factor in this plan.Specific criteria for passing or failing each inspection point must be clearly established and firmlyadhered to.Inspectors and COTPs should not be permitted to deviate from the established criteria, except in the caseof specific items that are identified as such in the inspection plan (and usual with a requirement for.~n~rif~concurrence at higher levels). , , , Next: CHAPTER 4: SYSTEM SAFETY ISSUES »Coordinates: 51°30′45″N0°04′44″W / 51.51255°N 0.078804°W Firmware Installation Instructions Supported Products: Phaser 3610, 6020, 6022, 6500, 6600. 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Lloyd's Register Group Limited (LR) is a technical and business services organisation and a maritime classification society, wholly owned by the Lloyd’s Register Foundation, a UK charity dedicated to research and education in science and engineering. The organisation dates to 1760. Its stated aims are to enhance the safety of life, property, and the environment, by helping its clients (including by validation, certification, and accreditation) to ensure the quality construction and operation of critical infrastructure. Historically, as Lloyd's Register of Shipping, it was a specifically maritime organisation. During the late 20th century, it diversified into other industries including oil and gas, process industries, nuclear, and rail. Through its 100% subsidiary Lloyd's Register Quality Assurance Ltd (LRQA), it is also a major vendor of independent assessment services, including management systems certification for quality certification to ISO9001, ISO14001 and OSHAS18001. Lloyd's Register is unaffiliated with Lloyd's of London.[3] In July 2012, the organisation converted from an industrial and provident society to a company limited by shares, named Lloyd’s Register Group Limited, with the new Lloyd’s Register Foundation as the sole shareholder. At the same time the organisation gifted to the Foundation a substantial bond and equity portfolio to assist it with its charitable purposes. It will benefit from continued funding from the group’s operating arm, Lloyd’s Register Group Limited.
Origin[edit]The organisation was named after a 17th-century coffee house in London that was frequented by merchants, marine underwriters, and others, all men associated with shipping. The coffee house owner, Edward Lloyd, helped them to exchange information by circulating a printed sheet of all the news he heard. In 1760, the Register Society was formed by the customers of the coffee house who assembled the Register of Shipping, the first known register of its type. Between 1800 and 1833, a dispute between shipowners and underwriters resulted in each group publishing a list—the 'Red Book' and the 'Green Book'.[4] Both parties came to the verge of bankruptcy. They reached agreement in 1834 to unite and form Lloyd’s Register of British and Foreign Shipping, establishing a General Committee and charitable values. In 1914, with an increasingly international outlook, the organisation changed its name to Lloyd's Register of Shipping. The Register[edit]The Society printed the first Register of Ships in 1764 in order to give both underwriters and merchants an idea of the condition of the vessels they insured and chartered: ship hulls were graded by a lettered scale (A being the best), and ship's fittings (masts, rigging, and other equipment) were graded by number (1 being the best). Thus the best classification 'A1', from which the expression A1 or A1 at Lloyd's is derived, first appeared in the 1775–76 edition of the Register. The Register, with information on all seagoing, self-propelled merchant ships of 100 gross tonnes or greater, is published annually. A vessel remains registered with Lloyd's Register until she is sunk, wrecked, hulked, or scrapped. The Register was published formerly by the joint venture company of Lloyd's Register-Fairplay, which was formed in July 2001 by the merger of Lloyd's Register's Maritime Information Publishing Group and Prime Publications Limited. Lloyd's Register sold its share of the venture to IHS Markit in 2009. Classification rules[edit]
The Lloyd's Register load line on the hull of the Cutty Sark
Lloyd's Register provides quality assurance and certification for ships, offshore structures, and shore-based installations such as power stations and railway infrastructure. However, Lloyd's Register is known best for the classification and certification of ships, and inspects and approves important components and accessories, including life-saving appliances, marine pollution prevention, fire protection, navigation, radio communication equipment, deck gear, cables, ropes, and anchors.[5] LR's Rules for Ships[edit]LR's Rules for Ships are derived from principles of naval architecture and marine engineering, and govern safety and operational standards for numerous merchant, military, and privately owned vessels. LR's Rules govern a number of topics including:
Specific editions of the rules are available to cater for merchant ships, naval ships, trimarans, special purpose vessels and offshore structures.[6] A ship is known as being in class if she meets all the minimum requirements of LR's Rules, and such a status affects the possibility of a ship getting insurance. Class can be withdrawn from a ship if she is in violation of any regulations and does not maintain the minimum requirements specified by the company. However, exceptional circumstances may warrant special dispensation from Lloyd's Register. Any alteration to the vessel, whether it is a structural alteration or machinery, must be approved by Lloyd's Register before it is implemented. Ships are inspected on a regular basis by a team of Lloyd's Register surveyors, one of the most important inspections being a ship's load line survey – due once every five years. Such a survey includes an inspection of the hull to make sure that the load line has not been altered. Numerous other inspections such as the condition of hatch and door seals, safety barriers, and guard rails are also performed. Upon completion the ship is allowed to be operated for another year, and is issued a load line certificate.[clarification needed] Rules and regulations[edit]Lloyd’s Register provide a list of rules and regulations to the public.
Location[edit]Lloyd's Register's main office is located in London at 71 Fenchurch Street. Lloyd's Register also maintains other offices globally, including Hong Kong and Houston, Texas. Influence in Austria[edit]In 1833 the Österreichischer Lloyd ('Austrian Lloyd') company was formed in the then-Austrian port city of Trieste, consciously modeling itself on the British company and seeking to publish a similar register. Later it also became an important shipping line. References[edit]
External links[edit]
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