Diving chamber
Encyclopedia
A diving chamber has two main functions:
, utilising an open bottom, the equivalent of a moon pool
, to equalise internal air pressure and external water pressure automatically without the need, necessarily, to measure and control it. An air compressor
or bottled compressed air
is required to maintain the volume of the air
as it becomes compressed with increasing depth, or to make up for oxygen
depleted by the occupants' breathing and for carbon dioxide
removed from exhaled air by a carbon dioxide scrubber
system. This type of diving chamber can only be used underwater, as the internal air pressure is directly proportional to the depth underwater and raising or lowering the chamber is the only way to adjust the pressure.
with hatches large enough for people to enter and exit, and an compressed breathing gas supply to raise the internal air pressure. This type is called a hyperbaric chamber whether used underwater or at the water surface or on land to produce underwater pressures, though some use submersible chamber to mean those used underwater and hyperbaric chamber to mean those used out of water. There are two related terms which reflect particular usages rather than technically-different types:
When used underwater there are two ways to prevent water flooding in when 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 commonly the hatch opens into an underwater airlock
, in which case the main chamber's pressure can stay constant, while it is the airlock pressure which shifts. This common design is called a lock-out chamber, and is used in submarine
s, submersibles, and underwater habitat
s as well as diving chambers.
Another arrangement utilises a dry airlock between a sealable hyperbaric compartment and an open diving bell compartment (so that effectively the whole structure is a mixture of the two types of diving chamber).
When used underwater all types of diving chamber are attached to a diving support vessel
by a strong cable
for raising and lowering and an umbilical cable
delivering compressed air, power, and communications, and all need weights attached or built in to overcome their buoyancy
. The greatest depth reached using a cable-suspended chamber is about 1500 m; beyond this the cable becomes unmanageable.
, breathing gas
cylinders to replenish scuba tanks, and communications and emergency equipment. It provides a temporary dry air environment during extended dives for rest, eating meals, carrying out tasks which can't be done underwater, and for emergencies. Diving chambers also act as an underwater base for surface supplied diving
operations, with the divers' umbilical
s (air supply, etc) attached to the diving chamber rather than to the diving support vessel.
A wet diving bell or open diving chamber must be raised slowly to 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.
for which the decompression times are very long.
A diving chamber based on a pressure vessel is more expensive to construct since it has to withstand very high pressure differentials. These may be both crushing pressures when the chamber is lowered into the sea and the internal pressure is kept less than ambient water pressure, or it may be an outwards pressure when it is out of the water and its internal pressure is set the same as water pressure at a certain depth.
Hyperbaric chambers also require more sophisticated systems to set and control internal gas pressure. However modern manufacturing techniques and control systems have reduced the cost and this type of diving chamber is now more common than the older dive bell type.
Hyperbaric lifeboat
s are specialized diving chambers or submersibles able to retrieve divers or occupants of diving chambers or underwater habitats in an emergency and to keep them in the required decompression phase. They have airlocks for underwater entry or to form a watertight seal with hatches on 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.
Hyperbaric chambers designed only for use out of water do not have to resist inward crushing forces, only outward expansion forces. Those for medical applications typically only operate up to two or three atmospheres, while those for diving applications may have to go to six atmospheres and above.
Lightweight portable hyperbaric chambers which can be lifted by helicopter
are used by commercial diving operators and rescue service
s to carry one or more divers requiring hospital
isation.
used in surface supplied diving
to allow the divers to complete their decompression stops at the end of a dive on the surface rather than underwater. This eliminates many of the risks of long decompressions underwater, in cold or dangerous conditions.
.
A recompression chamber is a pressure vessel
used to treat divers suffering from certain diving disorders such as decompression sickness
.
chamber is used in a hospital
or sporting context to treat patients whose condition might benefit from hyperbaric oxygen
treatment, including divers. Hyperbaric chambers capable of admitting more than one patient (multiplace) and an inside attendant have advantages for the treatment of decompression sickness and are preferred by the U.S. Coast Guard. Divers with serious complications or injuries may be attended to in this manner during recompression. In addition, multiplace chambers are generally capable of greater depth of recompression, should the need arise. For less seriously ill divers, the more common monoplace chamber is often used. A modified treatment regimen is then used.
- as a simpler form of submersible vesselSubmersibleA submersible is a small vehicle designed to operate underwater. The term submersible is often used to differentiate from other underwater vehicles known as submarines, in that a submarine is a fully autonomous craft, capable of renewing its own power and breathing air, whereas a submersible is...
to take diverUnderwater divingUnderwater diving is the practice of going underwater, either with breathing apparatus or by breath-holding .Recreational diving is a popular activity...
s underwaterUnderwaterUnderwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river. Three quarters of the planet Earth is covered by water...
and to provide a temporary base and retrieval system in the depths; - as a land or ship-based hyperbaric chamber to artificially reproduce the hyperbaric conditions under the seaSeaA sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...
(pressurePressurePressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
s above normal atmospheric pressureAtmospheric pressureAtmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
) for diving-related and non-diving medicalMedicineMedicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
applications such as hyperbaric medicine).
Basic types of diving chamber
There are two basic types of submersible diving chamber differentiated by the way in which the pressure in the diving chamber is produced and controlled.Open diving bell
The historically older open diving chamber, open diving bell or wet bell is in effect a large diving bellDiving bell
A diving bell is a rigid chamber used to transport divers to depth in the ocean. The most common types are the wet bell and the closed bell....
, utilising an open bottom, the equivalent of a moon pool
Moon pool
A moon pool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch...
, to equalise internal air pressure and external water pressure automatically without the need, necessarily, to measure and control it. An air compressor
Air compressor
An air compressor is a device that converts power into kinetic energy by compressing and pressurizing air, which, on command, can be released in quick bursts...
or bottled compressed air
Gas cylinder
A gas cylinder is a pressure vessel used to store gases at above atmospheric pressure. High pressure gas cylinders are also called bottles. Although they are sometimes colloquially called "tanks", this is technically incorrect, as a tank is a vessel used to store liquids at ambient pressure and...
is required to maintain the volume of the air
Gas laws
The early gas laws were developed at the end of the 18th century, when scientists began to realize that relationships between the pressure, volume and temperature of a sample of gas could be obtained which would hold for all gases...
as it becomes compressed with increasing depth, or to make up for oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
depleted by the occupants' breathing and for carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
removed from exhaled air by a carbon dioxide scrubber
Carbon dioxide scrubber
A carbon dioxide scrubber is a device which absorbs carbon dioxide . It is used to treat exhaust gases from industrial plants or from exhaled air in life support systems such as rebreathers or in spacecraft, submersible craft or airtight chambers...
system. This type of diving chamber can only be used underwater, as the internal air pressure is directly proportional to the depth underwater and raising or lowering the chamber is the only way to adjust the pressure.
Hyperbaric chamber
A sealable diving chamber, closed bell or dry bell is a pressure vesselPressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
with hatches large enough for people to enter and exit, and an compressed breathing gas supply to raise the internal air pressure. This type is called a hyperbaric chamber whether used underwater or at the water surface or on land to produce underwater pressures, though some use submersible chamber to mean those used underwater and hyperbaric chamber to mean those used out of water. There are two related terms which reflect particular usages rather than technically-different types:
- Decompression chamber, a hyperbaric chamber used by surface-supplied diversSurface supplied divingSurface supplied diving refers to divers using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel sometimes indirectly via a diving bell...
to make their surface decompression stopsDecompression (diving)Decompression in the context of diving derives from the reduction in ambient pressure experienced by the diver during the ascent at the end of a dive or hyperbaric exposure and refers to both the reduction in pressure and the process of allowing dissolved inert gases to be eliminated from the... - Recompression chamber, a hyperbaric chamber used to treat or prevent decompression sicknessDecompression sicknessDecompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
.
Moon pool
A moon pool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch...
chamber, and then its internal pressure must first be equalised to that of the moon pool chamber. More commonly the hatch opens into an underwater airlock
Airlock
An airlock is a device which permits the passage of people and objects between a pressure vessel and its surroundings while minimizing the change of pressure in the vessel and loss of air from it...
, in which case the main chamber's pressure can stay constant, while it is the airlock pressure which shifts. This common design is called a lock-out chamber, and is used in submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s, submersibles, and underwater habitat
Underwater habitat
Underwater habitats are underwater structures in which people can live for extended periods and carry out most of the basic human functions of a 24-hour day, such as working, resting, eating, attending to personal hygiene, and sleeping...
s as well as diving chambers.
Another arrangement utilises a dry airlock between a sealable hyperbaric compartment and an open diving bell compartment (so that effectively the whole structure is a mixture of the two types of diving chamber).
When used underwater all types of diving chamber are attached to a diving support vessel
Diving support vessel
A diving support vessel is a ship that is used as a floating base for professional diving projects.Commercial Diving Support Vessels emerged during the 1960s and 1970s when the need arose for diving operations to be performed below and around oil production platforms and associated installations in...
by a strong cable
Cable
A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...
for raising and lowering and an umbilical cable
Umbilical cable
An umbilical cable or umbilical is a cable which supplies required consumables to an apparatus. It is named by analogy with an umbilical cord...
delivering compressed air, power, and communications, and all need weights attached or built in to overcome their buoyancy
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
. The greatest depth reached using a cable-suspended chamber is about 1500 m; beyond this the cable becomes unmanageable.
Related equipment
In addition to the diving bell and hyperbaric chamber, related diving equipment includes the following.- Underwater habitatUnderwater habitatUnderwater habitats are underwater structures in which people can live for extended periods and carry out most of the basic human functions of a 24-hour day, such as working, resting, eating, attending to personal hygiene, and sleeping...
: consists of compartments operating under the same principles as diving bells and diving chambers, but fixed to the sea floor for long-term use. - Submersibles and submarines differ in being able to move under their own power. The interiors are usually maintained at surface pressure, but some examples include air locks and internal hyperbaric chambers.
- There is also other deep diving equipment which has atmospheric internal pressure, including:
- Bathysphere: name given to an experimental deep-sea diving chamber of the 1920s and 1930s.
- Benthoscope: a successor to the bathysphere built to go to greater depths.
- BathyscapheBathyscapheA bathyscaphe is a free-diving self-propelled deep-sea submersible, consisting of a crew cabin similar to a bathysphere, but suspended below a float rather than from a surface cable, as in the classic bathysphere design....
: a self-propelled submersible vessel able to adjust its own buoyancy for exploring extreme depths.
Diving chambers in use underwater
As well as transporting divers, a diving chamber carries tools and equipmentTool
A tool is a device that can be used to produce an item or achieve a task, but that is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose. Tools that are used in particular fields or activities may have different designations such...
, breathing gas
Breathing gas
Breathing gas is a mixture of gaseous chemical elements and compounds used for respiration.Air is the most common and only natural breathing gas...
cylinders to replenish scuba tanks, and communications and emergency equipment. It provides a temporary dry air environment during extended dives for rest, eating meals, carrying out tasks which can't be done underwater, and for emergencies. Diving chambers also act as an underwater base for surface supplied diving
Surface supplied diving
Surface supplied diving refers to divers using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel sometimes indirectly via a diving bell...
operations, with the divers' umbilical
Umbilical cable
An umbilical cable or umbilical is a cable which supplies required consumables to an apparatus. It is named by analogy with an umbilical cord...
s (air supply, etc) attached to the diving chamber rather than to the diving support vessel.
Use of open diving bell type
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. Secondly since internal air pressure and external water pressure on the bell wall are almost balanced, the chamber does not have to be as strong as a pressurised diving chamber (dry bell). (Actually if h is the distance between a point on the side of the bell and the air/water interface at the bottom, the air pressure at that point is higher than the water on the other side by a water head pressure equivalent to h, but this is a small and constant amount, and is not a structural problem).A wet diving bell or open diving chamber must be raised slowly to the surface with decompression stops
Decompression (diving)
Decompression in the context of diving derives from the reduction in ambient pressure experienced by the diver during the ascent at the end of a dive or hyperbaric exposure and refers to both the reduction in pressure and the process of allowing dissolved inert gases to be eliminated from the...
appropriate to the dive profile so that the occupants can avoid decompression sickness
Decompression sickness
Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
. This may take hours, and so limits its use.
Use of hyperbaric chambers
Submersible hyperbaric chambers can be brought to the surface without delay to allow divers to decompress since they can maintain the same pressure at which the divers were working. The divers can stay in the chamber on the support vessel to decompress. This flexibility makes them safer to use and more useful in an accident or emergency, including problems affecting the dive support vessel, such as sudden bad weather. They are used to support saturation divingSaturation diving
Saturation diving is a diving technique that allows divers to reduce the risk of decompression sickness when they work at great depth for long periods of time....
for which the decompression times are very long.
A diving chamber based on a pressure vessel is more expensive to construct since it has to withstand very high pressure differentials. These may be both crushing pressures when the chamber is lowered into the sea and the internal pressure is kept less than ambient water pressure, or it may be an outwards pressure when it is out of the water and its internal pressure is set the same as water pressure at a certain depth.
Hyperbaric chambers also require more sophisticated systems to set and control internal gas pressure. However modern manufacturing techniques and control systems have reduced the cost and this type of diving chamber is now more common than the older dive bell type.
Hyperbaric lifeboat
Lifeboat (shipboard)
A lifeboat is a small, rigid or inflatable watercraft carried for emergency evacuation in the event of a disaster aboard ship. In the military, a lifeboat may be referred to as a whaleboat, dinghy, or gig. The ship's tenders of cruise ships often double as lifeboats. Recreational sailors sometimes...
s are specialized diving chambers or submersibles able to retrieve divers or occupants of diving chambers or underwater habitats in an emergency and to keep them in the required decompression phase. They have airlocks for underwater entry or to form a watertight seal with hatches on 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.
Diving chambers in use on vessels and on land
Hyperbaric chambers are also used on land and at the ocean surface- to treat divers for decompression sickness (recompression chambers)
- to take surface supplied divers who have been brought up from underwater through their decompression stops (decompression chambers)
- to train and test divers to adapt to hyperbaric conditions and decompression routines
- to treat people using raised oxygen pressure in hyperbaric oxygen therapyHyperbaric oxygen therapyHyperbaric medicine, also known as hyperbaric oxygen therapy , is the medical use of oxygen at a level higher than atmospheric pressure. The equipment required consists of a pressure chamber, which may be of rigid or flexible construction, and a means of delivering 100% oxygen...
, HBOT - In saturation diving life support systems
- in scientific research requiring elevated gas pressures.
Hyperbaric chambers designed only for use out of water do not have to resist inward crushing forces, only outward expansion forces. Those for medical applications typically only operate up to two or three atmospheres, while those for diving applications may have to go to six atmospheres and above.
Lightweight portable hyperbaric chambers which can be lifted by helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
are used by commercial diving operators and rescue service
Coast guard
A coast guard or coastguard is a national organization responsible for various services at sea. However the term implies widely different responsibilities in different countries, from being a heavily armed military force with customs and security duties to being a volunteer organization tasked with...
s to carry one or more divers requiring hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
isation.
Decompression chamber
A decompression chamber is a pressure vesselPressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
used in surface supplied diving
Surface supplied diving
Surface supplied diving refers to divers using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel sometimes indirectly via a diving bell...
to allow the divers to complete their decompression stops at the end of a dive on the surface rather than underwater. This eliminates many of the risks of long decompressions underwater, in cold or dangerous conditions.
History
The decompression chamber was invented in 1916 by the Italian engineer Alberto GianniAlberto Gianni
Alberto Gianni was an Italian underwater diver and inventor.He invented the decompression chamber in 1916.-References:...
.
Recompression chamber
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
used to treat divers suffering from certain diving disorders such as decompression sickness
Decompression sickness
Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
.
Hyperbaric treatment chamber
A hyperbaric oxygen therapyHyperbaric oxygen therapy
Hyperbaric medicine, also known as hyperbaric oxygen therapy , is the medical use of oxygen at a level higher than atmospheric pressure. The equipment required consists of a pressure chamber, which may be of rigid or flexible construction, and a means of delivering 100% oxygen...
chamber is used in a hospital
Hospital
A hospital is a health care institution providing patient treatment by specialized staff and equipment. Hospitals often, but not always, provide for inpatient care or longer-term patient stays....
or sporting context to treat patients whose condition might benefit from hyperbaric oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
treatment, including divers. Hyperbaric chambers capable of admitting more than one patient (multiplace) and an inside attendant have advantages for the treatment of decompression sickness and are preferred by the U.S. Coast Guard. Divers with serious complications or injuries may be attended to in this manner during recompression. In addition, multiplace chambers are generally capable of greater depth of recompression, should the need arise. For less seriously ill divers, the more common monoplace chamber is often used. A modified treatment regimen is then used.
- Treatment is ordered by the treating physician (medical diving officer), and is usually in accordance with the U.S. Navy Diving Manual (U.S Navy Diving Tables). Other treatment tables have been developed, including the Catalina Tables, and others, including proprietary tables.
- Test of pressure. If the diagnosis of decompression illness is considered questionable, the diving officer may order a test of pressure. This typically consists of a recompression to 60 feet seawaterSeawaterSeawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
for up to 20 minutes. If the diver notes significant improvement in symptoms, or the operator can detect changes in the physical examination, a recompression algorithm is followed.
- Test of pressure. If the diagnosis of decompression illness is considered questionable, the diving officer may order a test of pressure. This typically consists of a recompression to 60 feet seawater
- Representative diving tables:
- U.S. Navy Table 6. This diving table consists of compression to the depth of 60 feet seawater with the patient on oxygen. The diver is later decompressed to 30 feet on oxygen, then slowly pushed 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. This diving table 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. This diving table consists of compression to 45 feet seawater with the patient on oxygen, with later decompression to surface pressure. This table is often used by monoplace hyperbaric chambers, or as a follow-up treatment in multiplace chambers.
Saturation diving life support systems
See also
- Hyperbaric medicine
- Byford DolphinByford DolphinByford Dolphin is a semi-submersible, column-stabilised drilling rig operated by Dolphin Drilling, a Fred. Olsen Energy subsidiary, and currently contracted by BP for drilling in the United Kingdom section of the North Sea. She is registered in Singapore...
(decompression accident) - Diving bellDiving bellA diving bell is a rigid chamber used to transport divers to depth in the ocean. The most common types are the wet bell and the closed bell....
- Moon poolMoon poolA moon pool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch...
- Saturation divingSaturation divingSaturation diving is a diving technique that allows divers to reduce the risk of decompression sickness when they work at great depth for long periods of time....
- Surface supplied divingSurface supplied divingSurface supplied diving refers to divers using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel sometimes indirectly via a diving bell...
- Decompression sicknessDecompression sicknessDecompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
- Hyperbaric stretcherHyperbaric stretcherA hyperbaric stretcher is a lightweight pressure vessel for human occupancy designed to accommodate one person undergoing initial hyperbaric treatment during or while awaiting transport or transfer to a treatment chamber....
External Links
- "Divers Go to Greater Depths With Aid of Chamber" Popular Mechanics, December 1930 first use of diving chamber by British Royal Navy divers -- detail drawings on subject
- Decompression Chamber in detail