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GlIOSSARY Buoyancy The tendency for a vessel to float due to the pressure of the surrounding fluid acting in the opposite direction to the pull of gravity on the vessel's mass. If the weight of the displaced volume of fluid exceeds the weight of the vessel (positive buoyancy), it will float. Captain of the Port (COTP) A Coast Guard officer responsible for cafetv Of f~riliti-e one ^~^r~t;~ ; a given port under U.S. jurisdiction. ._r ~ HA_ ^~^ v~_-,~ ~A ~~111~1~3 allu QEOl~Llvllb TO Center of buoyancy The mathematical center of the volume displaced by a vessel. (Unlike the center of gravity, for center of buoyancy only intact volumes—i.e., the external outline~ontribute to the calculation. Internal components such as batteries and motors do not contribute.) Center of gravity That point in an object around which its weight is evenly distributed or balanced (i.e., the mathematical summation of the center of weight of every component aboard a vessel). Certificate of Inspection (COI) A certificate issued by the U.S. Coast Guard that certifies a vessel has been inspected and satisfies safety requirements for the hull and required onboard operating and safety equipment. A COI for small passenger vessels less than 65 feet long is valid for 3 years. At least two reinspections must be made within the triennial incn`~.rtinn nPri^A in BEAM_ An_ +~^ -It ^_ remain valid. Certification The action the U.S. Coast Guard takes in awarding a vessel a Certificate of Inspection (see COI). It is not a guarantee that the vessel is safe to operate, but simple a rec~anitinn that it hoc passed the Coast Guard's inspection on a given date. (:I~.c.~ifirnt;nn Varir~llc rl~c~~;~;~;~ ~~ ~ ~ . . ~ ~ _ A^-r~~~& ~1 AVER 111 -all U~1 l'w1 t11~ ~1 ['v --red ~ ^_~,53~1A~AVA1 Lll~L AL Amp - ~~AA=~O ~la~3~3lll~LlOll dgUllUlUb worlawlae class" specific vessel designs. Classification means the classification agency states that the vessel complies with its rules for design and construction (which underwriters, in turn, take to mean that the vessel is a good insurance risk). CO2 scrubber system An onboard life support system component that removes (nscrubs~) CO2 to maintain the gas at a safe level in the onboard atmosphere. Critical dimensional check A test or inspection of safety-critical dimensions of the structure of a submersible, such as hull roundness or circularity. Deep submergence rescue vehicle (DSRV) One of a class of U.S. Navy minisubs (approximately 50 feet in length) whose primary mission is to rescue submariners trapped in their disabled submarine. The maximum diving depth of the DSRV is 5,~0 few (feet of sea water, rated), or 1,524 meters. Deep submergence vehicle (DSV) A small, deep-diving submersible that typically carries a crew of three (no passengers) and is used in support of offshore gas and oil development or for oceanographic research. DSVs have made dives as deep as 35,800 feet. although mart OOP.r~tP. fit Ar~nth~ Of 1 feet or less. - =~ rip ~~ my Brew Drop test (hydrostatic test) A structural test of a newly constructed submersible, in which the vessel is lowered to its design depth in water to test its physical integrity. Drop weight system An onboard safety system that consists of several weights (usually lead or concrete) 140
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attached to the exoskeleton, which may be dropped to provide positive buoyancy and rapid ascent in the event of an emergency. They are designed to be released from the inside (and, sometimes, the outside) of the vessel. Exostructure The outer shell that surrounds a submersible's MPV and on which are mounted the diving control surfaces, lights, exterior decks, etc. Factor of safeb (f.o.s.) Factors of safety are utilized by designers to provide safety margins. For submarines, the f.o.s. are usually fixed in terms of maximum operating depth and design depth (e.g., if the usual operating depth is 100 feet, the design depth may be 200 feet, for an f.o.s. of 2:1~. In terms of materials, the f.o.s. relate the material's yield strength to the actual or anticipated stress it will bear at the typical operating depth (e.g., an f.o.s. of 2 means that the yield stress is twice the actual stress). Fault tree analysis An analytical technique whereby an undesired state of a subject system is specified (usually one that is critical to safety) and the system is then analyzed in the context of its environment and operation to find all credible ways in which the undesired event can occur. The technique relies on a symbolic logic diagram showing the cause-effect relationship between the undesired event and one or more contributing causes. This surface vessel is used to transfer passengers from the shore site to the submersible and from the submersible to the shore. Hazard analysis A systematic and comprehensive engineering analysis of the hardware, personnel, operational, and procedural elements of a system such as a submersible, which is intended to identify the sources of hazards, their mechanisms, and their effects. Life support A generic term for the functions and systems required to provide for the physical requirements and comfort of the passengers under normal and emergency conditions. On a tourist submersible, life support consists of the breathable air supply (including emergency air) and air filtration and regeneration system, CO2 monitoring, the fire suppression system, and other emergency equipment such as life preservers. Main pressure vessel (MPV) This is the central structural component of a submersible that provides the primary barrier to external water pressure on the hull. Passenger safety depends critically on the integrity of the MPV. Metacentr~c height (BG) An index of intact stability, measured by the vertical separation between the center of gravity and the center of buoyance. For a submersible, positive stability occurs when the center of buoyance is located above the center of gravity. (A separation of [cm] 3-12 inches is the typical range of BG for DSVs and tourist submersibles.) Officer in Charge of Marine Inspection (OCMI) A U.S. Coast Guard officer who is responsible for onboard inspection of vessels under U.S. jurisdiction in and near a given port, in accordance with Coast Guard regulations. Pressure vessels for human occupancy (PVHO) In engineering terms, a class of tank that will be required to withstand external or internal pressure while manned. Quarterly control verification exam For foreign-built vessels only, quarterly control verification exams are conducted jointly by the Coast Guard and the classifying agency. The Coast Guard issues a certificate, CG-4504, "Control Verification for Foreign Vessels," to foreign vessels in compliance with SOLAS regulations. Rebreather A device designed for use by one person and intended to provide emergency air supply requirements for passengers aboard a submersible in the event of an emergency (such as fire or failure of the CO2 scrubber system) that reduces the breathability of the onboard atmosphere. Safety of Life at Sea (SOILS) passenger ship safety certificate An international certificate issued under the SOLAS convention by the government of the nation under whose flag a vessel is sailing. All signatory governments agree that vessels they certificate will be in compliance with the SOLAS Ferry regulations governing ship safety. Else U.~. Coast Guard makes "control verification" inspections to veritr that foreign flag vessels operating in U.S. ports comply with SOLAS regulations. (Only rarely does this apply to tourist submersibles.) 141
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Safety review A comprehensive review of a system's hardware and operations that is intended to improve the identification, analysis, and elimination or control of hazards. This review is broader in scope than the hazard analysis and includes that analysis as input. It brings the organizational experience to bear on the subject system. Submersible Any vessel that operates with its entire hull below the surface of the water. While most are free-swimming, submersibles may also be tethered or on tracks. They may be manned, or unmanned and remotely operated, and (if manned) may or may not require a self-contained air supply. Surface support safety boat A small surface craft, sometimes referred to as the Chase boat, which follows the tourist submersible during its dive in order to provide diver support and immediate assistance in the event of an emergency. This vessel also deploys divers, if required, as part of the underwater entertainment program. Tourist submersible A manned submarine employed by private companies to carry a crew and passengers on a commercial basis, primarily for recreational and educational purposes. Structurally, they are characterized by large viewing windows, large (relative to DSVs) passenger capacity, and shallow diving depths. Operationally, they are designed to make multiple dives and handle a large number of passengers daily. Trim is an inclined attitude taken by a submersible's bow (or stern) when it moves above or below the even keel (level) attitude. A longitudinal separation between the center of gravity and center of buoyancy will cause a submersible to trim about the center of gravity. If the center of gravity is aft of the center of buoyancy, the vessel will trim aft (down by the stern). If the center of gravity is forward of the center of buoyancy, it will trim forward (down by the bow). Yield stress (strength) A material's yield stress or yield strength is the maximum stress that can be applied to the material without permanently deforming it or causing it to fail. T. rim 142
Representative terms from entire chapter: