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70-409: The boat can be used for over-the-horizon transportation, inserting lightly armed raiding parties or reconnaissance teams onto beaches, piers, offshore facilities and larger vessels. The CRRC can be inflated in minutes by foot pump, compressor or CO 2 tank and can be deployed from shore and a variety of vessels. Additionally, it can be launched from several types of aircraft and submarines equipped with

140-405: A bell as a rescue chamber to transport divers from one saturation system to another. This may require temporary modifications to the bell, and is only possible if the mating flanges of the systems are compatible. Experimental compression chambers have been used since about 1860. In 1904, submarine engineers Siebe and Gorman , together with physiologist Leonard Hill , designed a device to allow

210-422: A built in breathing system for supply of alternative breathing gases. The pressure vessel is the main structural component, and includes the shell of the main chamber, and if present, the shells of fore-chamber and medical or supply lock. A forechamber or entry lock may be present to provide personnel access to the main chamber while it is under pressure. A medical or stores lock may be present to provide access to

280-476: A closed bell for decompression after bounce dives, following a transfer under pressure , or the divers may surface before completing decompression and be recompressed in the chamber following stringent protocols to minimise the risk of developing symptoms of decompression sickness in the short period allowed before returning to pressure. A hyperbaric treatment chamber is a hyperbaric chamber intended for, or put into service for, medical treatment at pressures above

350-448: A closed bell may be used to transfer a small number (up to about 3) of divers between one hyperbaric facility and another when the necessary infrastructure is available. A hyperbaric stretcher is a lightweight pressure vessel for human occupancy (PVHO) designed to accommodate one person undergoing initial hyperbaric treatment during or while awaiting transport or transfer to a treatment chamber . A transportable decompression chamber

420-554: A compressed breathing gas supply which may be used to raise the internal pressure. Such chambers provide a supply of breathing gas for the user, and are usually called hyperbaric chambers, whether used underwater, at the water surface or on land. The term submersible chamber may be used to refer to those used underwater and hyperbaric chamber for those used out of water. There are two related terms that reflect particular usages rather than technically different types: When used underwater there are two ways to prevent water flooding in when

490-633: A conical chamber called the Transportable Recompression Chamber (TRC) and a cylindrical Transfer Lock (TL), which can be connected by a NATO flange coupling, and is provided with a compressed air and oxygen supply system. The component chambers are mounted on wheeled trolleys and have a design pressure of 110 pounds per square inch (7.6 bar) gauge which is suitable for most of the US Navy treatment schedules that are relevant for bounce dives. At 1,268 pounds (575 kg) It

560-416: A cylindrical container filled with liquid rotating in the z direction in cylindrical coordinates, the equations of motion are: where P {\displaystyle P} is the pressure, ρ {\displaystyle \rho } is the density of the fluid, r {\displaystyle r} is the radius of the cylinder, ω {\displaystyle \omega }

630-418: A diver to enter a closed chamber at depth, then have the chamber – still pressurised – raised and brought aboard a boat. The chamber pressure was then reduced gradually. This preventative measure allowed divers to safely work at greater depths for longer times without developing decompression sickness. In 1906, Hill and another English scientist M Greenwood subjected themselves to high pressure environments, in

700-420: A lock-out chamber, and is also used in submarines , submersibles, and underwater habitats . When used underwater all types of diving chamber are deployed from a diving support vessel suspended by a cable for raising and lowering and an umbilical cable delivering, at a minimum, compressed breathing gas, power, and communications. They may need ballast weights to overcome their buoyancy . In addition to

770-403: A pressure chamber built by Siebe and Gorman, to investigate the effects. Their conclusions were that an adult could safely endure seven atmospheres , provided that decompression was sufficiently gradual. A recompression chamber intended for treatment of divers with decompression sickness was built by CE Heinke and company in 1913, for delivery to Broome, Western Australia , in 1914, where it

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840-440: A role (e.g. Van der Waals forces , hydrogen bonds ). Its free surface will assume the shape with the least surface area for its volume: a perfect sphere . Such behaviour can be expressed in terms of surface tension . It can be demonstrated experimentally by observing a large globule of oil placed below the surface of a mixture of water and alcohol having the same density so the oil has neutral buoyancy . Flatness refers to

910-420: A saturation system. This would be used if the platform is at immediate risk due to fire or sinking, and allows the divers under saturation to get clear of the immediate danger. A hyperbaric lifeboat is self-contained and can be operated by a surface pressure crew while the chamber occupants are under pressure. It must be self-sufficient for several days at sea, in case of a delay in rescue due to sea conditions. It

980-441: A senior-ranking individual is on board. Across from him sits the assistant coxswain, who relays hand signals from other boats and aids the coxswain as required. The remaining passengers (six raiders plus the two coxswains make up a full team) normally lay on and straddle the gunwale, keeping a low silhouette to help avoid detection and leaving room on the deck for weapons, equipment and (if necessary) additional fuel bladders. Because

1050-399: A single leak will not result in loss of pressure throughout the boat, and that air can be bled between chambers to compensate for loss in one. Two additional chambers, located below the gunwale on either side and called "speed skags," provide cushioning for the boat's occupants and additional buoyancy in case of pressure loss in the hull. The final chamber is an inflatable keel tube which runs

1120-518: A special lockout chamber or a Dry Deck Shelter . Its chief advantages are light weight, compact size when stowed, stealth, versatility, and the safety imparted by its super-buoyant nature (which gives it the ability to operate in relatively high seas). A total of eight individual airtight chambers comprise the FC470. The main hull or gunwale contains five intercommunicating chambers, which are separated by internal baffles and valves . This means that

1190-432: A special fuel bladder, which can be of either 6- or 18-gallon capacity and which feeds the engine via a flexible hose. Deflated and rolled up, the boat and all necessary equipment can easily fit into the bed of a small pickup. Most military CRRC's use a 55 horsepower (41 kW) two-stroke engine with a pump-jet propulsor, which consists of a shrouded impeller. This design reduces the risk of serious injury to personnel in

1260-435: A suitable facility. A decompression chamber, or deck decompression chamber, is a pressure vessel for human occupancy used in surface supplied diving to allow the divers to complete their decompression stops at the end of a dive as the surface decompression rather than underwater. This eliminates many of the risks of long decompressions underwater, in cold or dangerous conditions. A decompression chamber may be used with

1330-444: A water-filled or partially water-filled hyperbaric chamber, referred to as a wet pot, usually accessed via a dry hyperbaric chamber at the same pressure, with airlock access to the outside. This allows convenient monitoring and instrumentation, and facilities for immediate assistance. A wet pot allows decompression algorithm validation with the divers immersed and working at specified rates while their metabolic rates are monitored. It

1400-478: A whole is generally to the ASME Boiler and Pressure Vessel Code , Section VIII. These PVHO safety codes focus on the systems aspect of the chambers such as life support requirements as well as the acrylic windows. The PVHO code addresses hyperbaric medical systems, commercial diving systems, submarines, and pressurized tunnel boring machines. An access door or hatch is normally hinged inward and held closed by

1470-434: Is a relatively small chamber in which a diver and an inside attendant can be transported under pressure by land, sea or air at a pressure suitable for hyperbaric treatment. The chamber is designed for transfer under pressure to a full-side decompression chamber at the destination, either directly or via a transfer chamber The US Navy Transportable Recompression Chamber System (TRCS) is an example of this type. TRCS Mod0 comprises

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1540-410: Is a vessel for human occupation, which may have an entrance that can be sealed to hold an internal pressure significantly higher than ambient pressure , a pressurised gas system to control the internal pressure, and a supply of breathing gas for the occupants. There are two main functions for diving chambers: There are two basic types of submersible diving chambers, differentiated by the way in which

1610-435: Is at the pressure of the free water surface , and varies accordingly with depth. The breathing gas supply for the open bell may be self-contained, or more usually, supplied from the surface via flexible hose, which may be combined with other hoses and cables as a bell umbilical . An open bell may also contain a breathing gas distribution panel with divers' umbilicals to supply divers with breathing gas during excursions from

1680-506: Is called transfer under pressure (TUP). This is used to transfer personnel from portable recompression chambers to multi-person chambers for treatment, and between saturation life support systems and personnel transfer capsules (closed bells) for transport to and from the worksite, and for evacuation of saturation divers to a hyperbaric lifeboat. Diver training and experimental work requiring exposure to relatively high ambient pressure under controllable and reproducible conditions may be done in

1750-449: Is commonly referred to in commercial diving and military diving as the diving bell , PTC (personnel transfer capsule) or SDC (submersible decompression chamber). The system can be permanently installed on a ship or ocean platform, but is usually capable of being transferred between vessels. The system is managed from a control room, where depth, chamber atmosphere and other system parameters are monitored and controlled. The diving bell

1820-480: Is later decompressed to 30 feet (9.1 m) on oxygen, then slowly returned to surface pressure. This table typically takes 4 hours 45 minutes. It may be extended further. It is the most common treatment for type 2 decompression illness. U.S. Navy Table 5 is similar to Table 6 above, but is shorter in duration. It may be used in divers with less severe complaints (type 1 decompression illness). U.S. Navy Table 9 consists of compression to 45 feet (14 m) with

1890-406: Is more likely to have small cracks the operators can see and have time to take mitigation steps instead of failing catastrophically. Free surface In physics , a free surface is the surface of a fluid that is subject to zero parallel shear stress , such as the interface between two homogeneous fluids . An example of two such homogeneous fluids would be a body of water (liquid) and

1960-489: Is not truly portable by manpower in most circumstances, but the wheels make it fairly easy to move around on a horizontal surface. A saturated diver who needs to be evacuated should preferably be transported without a significant change in ambient pressure. Hyperbaric evacuation requires pressurised transportation equipment, and could be required in a range of situations: A hyperbaric lifeboat or rescue chamber may be provided for emergency evacuation of saturation divers from

2030-423: Is ordered by the treating physician (medical diving officer), and generally follows one of the standard hyperbaric treatment schedules such as the US Navy treatment Tables 5 or 6. When hyperbaric oxygen is used it is generally administered by built-in breathing systems (BIBS), which reduce contamination of the chamber gas by excessive oxygen. If the diagnosis of decompression illness is considered questionable,

2100-407: Is possible to start decompression after launching if the occupants are medically stable, but seasickness and dehydration may delay the decompression until the module has been recovered. The rescue chamber or hyperbaric lifeboat will generally be recovered for completion of decompression due to the limited onboard life support and facilities. The recovery plan will include a standby vessel to perform

2170-474: Is sometimes necessary to transport a diver with severe symptoms of decompression illness to a more suitable facility for treatment, or to evacuate people in a hyperbaric environment which is threatened by a high risk hazard. A hyperbaric stretcher may be useful to transport a single person, a portable chamber is intended for use transporting a casualty with a chamber attendant, and hyperbaric rescue and escape systems are used to transfer groups of people. Occasionally

Combat rubber raiding craft - Misplaced Pages Continue

2240-406: Is the angular frequency , and g {\displaystyle g} is the gravitational acceleration . Taking a surface of constant pressure ( d P = 0 ) {\displaystyle (dP=0)} the total differential becomes Integrating, the equation for the free surface becomes where h c {\displaystyle h_{c}} is the distance of

2310-478: Is unable to function properly. Hyperbaric oxygen therapy increases oxygen transport via dissolved oxygen in serum, and is most efficacious where the haemoglobin is compromised (e.g. carbon monoxide poisoning) or where the extra oxygen in solution can diffuse through tissues past embolisms that are blocking the blood supply as in decompression illness. Hyperbaric chambers capable of admitting more than one patient (multiplace) and an inside attendant have advantages for

2380-473: Is used to transfer divers from the system to the work site. Typically, it is mated to the system utilizing a removable clamp and is separated from the system by a trunking space, through which the divers transfer to and from the bell. The bell is fed via a large, multi-part umbilical that supplies breathing gas, electricity, communications and hot water. The bell also is fitted with exterior mounted breathing gas cylinders for emergency use. The divers operate from

2450-428: The poles . Over large distances or planetary scale, the surface of an undisturbed liquid tends to conform to equigeopotential surfaces; for example, mean sea level follows approximately the geoid . If the free surface of a liquid is disturbed, waves are produced on the surface. These waves are not elastic waves due to any elastic force ; they are gravity waves caused by the force of gravity tending to bring

2520-562: The CRRC offers no protection to its occupants and is itself highly vulnerable to small-arms fire, operations involving it almost always take place at night and depend on the elements of stealth and surprise. To alleviate this, Zodiac introduced ArmorFlate, the world's first inflatable bulletproof system for inflatable boats, in 2002. It can be installed on the Zodiac FC470 and inflates in 40 seconds. Lockout chamber A diving chamber

2590-469: The air in the Earth's atmosphere (gas mixture). Unlike liquids , gases cannot form a free surface on their own. Fluidized / liquified solids, including slurries , granular materials, and powders may form a free surface. A liquid in a gravitational field will form a free surface if unconfined from above. Under mechanical equilibrium this free surface must be perpendicular to the forces acting on

2660-513: The bell using surface supplied umbilical diving equipment. A hyperbaric lifeboat, hyperbaric escape module or rescue chamber may be provided for emergency evacuation of saturation divers from a saturation system. This would be used if the platform is at immediate risk due to fire or sinking to get the occupants clear of the immediate danger. A hyperbaric lifeboat is self-contained and self-sufficient for several days at sea. The process of transferring personnel from one hyperbaric system to another

2730-433: The bell, and an on-board emergency gas supply in high-pressure storage cylinders. This type of diving chamber can only be used underwater, as the internal gas pressure is directly proportional to the depth underwater, and raising or lowering the chamber is the only way to adjust the pressure. A sealable diving chamber, closed bell or dry bell is a pressure vessel with hatches large enough for people to enter and exit, and

2800-469: The bottom hatch for this purpose. The external door to the medical lock is unusual in that it opens outward and is not held closed by the internal pressure, so it needs a safety interlock system to make it impossible to open when the lock is pressurised. Viewports are generally provided to allow the operating personnel to visually monitor the occupants, and can be used for hand signalling as an auxiliary emergency communications method. The major components are

2870-426: The chamber does not have to be as strong as a pressurised diving chamber (dry bell). The air inside an open bell is at the same pressure as the water at the air-water interface surface. This pressure is constant and the pressure difference on the bell shell can be higher than the external pressure to the extent of the height of the air space in the bell. A wet diving bell or open diving chamber must be raised slowly to

Combat rubber raiding craft - Misplaced Pages Continue

2940-431: The divers' umbilicals (air supply, etc.) attached to the diving chamber rather than to the diving support vessel. Diving bells and open diving chambers of the same principle were more common in the past owing to their simplicity, since they do not necessarily need to monitor, control and mechanically adjust the internal pressure. Since internal air pressure and external water pressure on the bell wall are almost balanced,

3010-576: The diving bell and hyperbaric chamber, related Pressure Vessels for Human Occupancy (PVHOs) includes the following: As well as transporting divers, a diving chamber carries tools and equipment , high pressure storage cylinders for emergency breathing gas supply, and communications and emergency equipment. It provides a temporary dry air environment during extended dives for rest, eating meals, carrying out tasks that cannot be done underwater, and for emergencies. Diving chambers also function as an underwater base for surface supplied diving operations, with

3080-409: The diving officer may order a test of pressure. This typically consists of a recompression to 60 feet (18 m) for up to 20 minutes. If the diver notes significant improvement in symptoms, or the attendant can detect changes in a physical examination, a treatment table is followed. U.S. Navy Table 6 consists of compression to the depth of 60 feet (18 m) with the patient on oxygen. The diver

3150-422: The end of their tour of duty. This is usually done in a decompression chamber, which is part of the saturation system. The risk of decompression sickness is significantly reduced by minimizing the number of decompressions, and by decompressing at a very conservative rate. The saturation system typically comprises a complex made up of a living chamber, transfer chamber and submersible decompression chamber , which

3220-458: The entire internal area of the boat, prevents the hull from collapsing or "taco-ing" under power. A ready-for-use craft includes an outboard engine (two in some configurations); removable aluminium deckplates or roll-up slatted decking; paddles; a bow line for securing the docked boat and a "righting" line which is used to flip the boat in the event of capsizing. At the bow of the boat are storage bags for equipment (foot pumps, extra lines, etc.) and

3290-406: The free surface from the bottom of the container along the axis of rotation. If one integrates the volume of the paraboloid formed by the free surface and then solves for the original height, one can find the height of the fluid along the centerline of the cylindrical container: The equation of the free surface at any distance r {\displaystyle r} from the center becomes If

3360-412: The free surface will assume a parabolic surface of revolution known as a paraboloid . The free surface at each point is at a right angle to the force acting at it, which is the resultant of the force of gravity and the centrifugal force from the motion of each point in a circle. Since the main mirror in a telescope must be parabolic, this principle is used to create liquid-mirror telescopes . Consider

3430-406: The internal pressure is less than ambient water pressure, such as may be used for submarine rescue . Rescue bells are specialized diving chambers or submersibles able to retrieve divers or occupants of submarines, diving chambers or underwater habitats in an emergency and to keep them under the required pressure. They have airlocks for underwater entry or to form a watertight seal with hatches on

3500-409: The length of the craft and gives the bottom of the hull a "V" shape, imparting directional stability and additional shock absorption. A wooden "transom" board at the stern provides a mounting point for the outboard engine (s). The deck (floor) is composed of four interlocking aluminum plates, which are fixed to the "thrust board" at the bow end and the transom at the stern. This rigid structure, spanning

3570-503: The liquid; if not there would be a force along the surface, and the liquid would flow in that direction. Thus, on the surface of the Earth, all free surfaces of liquids are horizontal unless disturbed (except near solids dipping into them, where surface tension distorts the surface in a region called the meniscus ). In a free liquid that is not affected by outside forces such as a gravitational field, internal attractive forces only play

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3640-419: The local atmospheric pressure. A hyperbaric oxygen therapy chamber is used to treat patients, including divers, whose condition might improve through hyperbaric oxygen treatment. Some illnesses and injuries occur, and may linger, at the cellular or tissue level. In cases such as circulatory problems, non-healing wounds, and strokes, adequate oxygen cannot reach the damaged area and the body's healing process

3710-399: The longer ocean surface waves , because the surface is increased in area by the ripples and the capillary forces are in this case large compared with the gravitational forces. Capillary ripples are damped both by sub-surface viscosity and by surface rheology . If a liquid is contained in a cylindrical vessel and is rotating around a vertical axis coinciding with the axis of the cylinder,

3780-616: The main chamber for small items while under pressure. The small volume allows quick and economical transfer of small items, as the gas lost has relatively small volume compared to the forechamber. In the United States, the engineering safety standards is the American Society of Mechanical Engineers (ASME) Pressure Vessels for Human Occupancy (PVHO). There is a design code (PVHO-1) and a post-construction, or maintenance & operations, code (PVHO-1). The pressure vessel as

3850-479: The patient on oxygen, with later decompression to surface pressure. This table may be used by lower-pressure monoplace hyperbaric chambers, or as a follow-up treatment in multiplace chambers. A hyperbaric environment on the surface comprising a set of linked pressure chambers is used in saturation diving to house divers under pressure for the duration of the project or several days to weeks, as appropriate. The occupants are decompressed to surface pressure only once, at

3920-417: The pressure differential, but it may also be dogged for a better seal at low pressure. There is a door or hatch at the access opening to the forechamber, the main chamber, both ends of a medical or stores lock, and at any trunking to connect multiple chambers. A closed bell has a similar hatch at the bottom for use underwater and may have a side hatch for transfer under pressure to a saturation system, or may use

3990-464: The pressure in the diving chamber is produced and controlled. The historically older open diving chamber, known as an open diving bell or wet bell, is in effect a compartment with an open bottom that contains a gas space above a free water surface , which allows divers to breathe underwater. The compartment may be large enough to fully accommodate the divers above the water, or may be smaller, and just accommodate head and shoulders. Internal air pressure

4060-423: The recovery. Bell to bell transfer may be used to rescue divers from a lost or entrapped bell. A "lost" bell is a bell which has been broken free of lifting cables and umbilical; the actual position of the bell is usually still known with considerable accuracy. This will generally occur at or near the bottom, and the divers transfer between bells at ambient pressure. It is also possible in some circumstances to use

4130-431: The shape of a liquid 's free surface. On Earth, the flatness of a liquid is a function of the curvature of the planet, and from trigonometry , can be found to deviate from true flatness by approximately 19.6 nanometers over an area of 1 square meter , a deviation which is dominated by the effects of surface tension . This calculation uses Earth's mean radius at sea level, however a liquid will be slightly flatter at

4200-405: The submersible hyperbaric chamber's hatch is opened. The hatch could open into a moon pool chamber, and then its internal pressure must first be equalised to that of the moon pool chamber. More generally the hatch opens into an underwater airlock , in which case the main chamber's pressure can stay constant, while it is the airlock pressure that is equalised with the exterior. This design is called

4270-404: The support vessel off station. A diving chamber based on a pressure vessel is more expensive to construct since it has to withstand high pressure differentials. These may be bursting pressures as is the case for a dry bell used for saturation diving, where the internal pressure is matched to the water pressure at the working depth, or crushing pressures when the chamber is lowered into the sea and

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4340-442: The support vessel, or transferring them under pressure to a more spacious decompression chamber or to a saturation system , where they remain under pressure throughout the tour of duty, working shifts under approximately constant pressure, and are only decompressed once at the end. The ability to return to the surface without in-water decompression reduces the risk to the divers if the weather or compromised dynamic positioning forces

4410-488: The surface of the disturbed liquid back to its horizontal level. Momentum causes the wave to overshoot , thus oscillating and spreading the disturbance to the neighboring portions of the surface. The velocity of the surface waves varies as the square root of the wavelength if the liquid is deep; therefore long waves on the sea go faster than short ones. Very minute waves or ripples are not due to gravity but to capillary action , and have properties different from those of

4480-402: The surface with decompression stops appropriate to the dive profile so that the occupants can avoid decompression sickness . This may take hours, and so limits its use. Submersible hyperbaric chambers known as closed bells or personnel transfer capsules can be brought to the surface without delay by maintaining the internal pressure and either decompressing the divers in the chamber on board

4550-454: The target structure to effect a dry transfer of personnel. Rescuing occupants of submarines or submersibles with internal air pressure of one atmosphere requires being able to withstand the huge pressure differential to effect a dry transfer, and has the advantage of not requiring decompression measures on returning to the surface, allowing a more rapid turnaround to continue the rescue effort. Hyperbaric chambers are also used on land and above

4620-533: The treatment of decompression sickness (DCS) if the patient requires other treatment for serious complications or injury while in the chamber, but in most cases monoplace chambers can be successfully used for treating decompression sickness. Rigid chambers are capable of greater depth of recompression than soft chambers that are unsuitable for treating DCS. A recompression chamber is a hyperbaric treatment chamber used to treat divers suffering from certain diving disorders such as decompression sickness . Treatment

4690-417: The water when compared to the traditional open propeller. It also reduces the risk of the propulsion system being seriously damaged by submerged objects. A specially-trained coxswain sits at the stern (rear) of the boat and controls it via the tiller arm, attached to an outboard engine. The coxswain is considered the commander of the craft and is ultimately responsible for its operation, regardless of whether

4760-513: The water: Hyperbaric chambers designed only for use out of water do not have to resist crushing forces, only bursting forces. Those for medical applications typically only operate up to two or three atmospheres absolute, while those for diving applications may go to six atmospheres or more. Lightweight portable hyperbaric chambers that can be lifted by helicopter are used by military or commercial diving operators and rescue services to carry one or two divers requiring recompression treatment to

4830-855: The window (transparent acrylic), the window seat (holds the acrylic window), and retaining ring. Interior lighting can be provided by mounting lights outside the viewports. These are a pressure vessel feature specific to PVHOs due to the need to see the people inside and evaluate their health. Section 2 of the engineering safety code ASME PVHO-1 is used internationally for designing viewports. This includes medical chambers, commercial diving chambers, decompression chambers, and pressurized tunnel boring machines. Non-military submarines use acrylic viewports for seeing their surroundings and operating any attached equipment. Other material have been attempted, such as glass or synthetic saphhire, but they would consistently fail to maintain their seal at high pressures and cracks would progress rapidly to catastrphophic failure. Acrylic

4900-492: Was successfully used to treat a diver in 1915. That chamber is now in the Broome Historical Museum. The construction and layout of a hyperbaric diving chamber depends on its intended use, but there are several features common to most chambers. There will be a pressure vessel with a chamber pressurisation and depressurisation system, access arrangements, monitoring and control systems, viewports, and often

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