The surface-supplied dives are diving using equipment supplied with respiratory gas using surface diverges from either the shore or from the dive support vessels, sometimes indirectly through the diving bells. This is different from scuba diving, where the dive breathing apparatus is completely complete and has no bearing to the surface. The main advantage of dives supplied from conventional surfaces is a lower risk of sinking and a much larger supply of breathing gas than scuba, allowing longer working periods and safer decompression.
The standard copper free-flow dive gown is a version that makes commercial dives a decent job, and although still used in some areas, these machines have been replaced by lighter free-flow helmets, and for the most part, light-weight helmet, masks band and full face mask mask. The respiratory gas used includes air, heliox, nitrox and trimix.
The saturation saturation is the way the dive is provided on the surface where the diver lives under pressure in the saturation system or underwater habitat and is decompressed only at the end of the task journey.
Airline, or hookah diving, and "diving compressor" are lower tech variants also use respiratory air supply from the surface.
Video Surface-supplied diving
Variations
Several different settings exist to supply the respiratory gas to the diver from the surface:
- Standard or Heavy Equipment - Historical copper helmet, canvas suit, and weighted boots.
- Scuba Replacement - The arrangement provided by the surface where the main air supply and the reserve come from the high pressure cylinder. The remainder of the system is identical to the standard surface supply configuration, and full umbilical systems, bailout cylinders, communications and surface air panels are used. It is more portable than most compressors and is used by commercial submarine contractors instead of scuba with most of the advantages and disadvantages of regular compressor surface supplies.
- Hookah - The basic form of surface dive provided where the supply of air through a single hose is often referred to as an airline dive or Hookah (sometimes Hooka). It often uses the second stage of standard scuba as a delivery unit, but is also used with a full face mask of light. A gas bailout can be done, but this is not always the case. Commercial diamond dives working in shallow zones off the west coast of South Africa under the Minerals and Energy Department's practice code use half-mask and hookah valve demand, and no bailout as standard practice. Their security record is relatively poor.
- Snuba and SASUBA - A system used to supply air from cylinders mounted on buoys to recreational divers moored by short hose (about 6m) through scuba regulator.
- Compressor diving - The more basic system is the "Compressor diving" arrangement used in the Philippines and the Caribbean for fishing. This basic and extremely dangerous system uses a large number of small plastic tubes connected to a single compressor to supply a large number of divers simultaneously. The tip of the hose delivery is not burdened by a mechanism or a funnel, and is held only by the gear diver. Air supply flows freely and often unfiltered.
Maps Surface-supplied diving
Alternative
- Scuba, commonly used in recreational dives, is the ultimate alternative to submarine equipment provided on the surface. Scuba is available in open circuit and rebreather configuration.
- The atmospheric diving settings like the JIM and Newtsuit suits isolate the occupants from the surrounding pressure, but are large and very expensive.
- Submersible manned and unmanned (ROVs and AUVs) have their apps, but lacks the dexterity of today's divers (2011).
- Free diving, or immersion, is very limited in duration and relatively high risk.
Apps
The surface dive equipment and techniques used are primarily used in professional dives or military dives because of the greater cost and complexity of owning and operating the equipment. This type of equipment is used in dive saturation, because the gas supply is relatively safe, and the diver can not save to the surface, and to dive in contaminated water, where the diver must be protected from the environment, and helmets are generally used for environmental isolation.
There has been a development of low cost flight systems for shallow recreational diving, where limited training is balanced by physically restricting accessible depth.
History
The first submarine-supplied first-time submarine equipment produced by Charles and John Deane's brothers in the 1820s. Inspired by the fire accident he witnessed in a horse stables in England, he designed and patented the "Smoke Helmet" for use by firefighters in a smoke-filled area in 1823. The equipment consisted of a copper helmet with flexible collars and collars. The long leather hose attached to the back of the helmet will be used to supply air - the original concept is that it will be pumped using a double bellows. A short pipe allows breathing air to escape. The garment is made of leather or an airtight fabric, secured with a strap.
The brothers had insufficient funds to build the equipment themselves, so they sold the patent to their employer, Edward Barnard. It was not until 1827 that the first smoke helmet was built, by the German-born British engineer, Augustus Siebe. In 1828 they decided to look for another app for their device and turn it into a diving helmet. They market helmets with "wetsuits" loosely attached so that divers can do rescue work but only in full vertical position, otherwise the water goes into that suit.
In 1829, the Deane sailed from Whitstable to test their new underwater equipment, establishing a dive industry in the city. In 1834, Charles used his helmet and wetsuits in a successful venture in the Royal George ship wreck at Spithead, where he found 28 ship cannons. In 1836, John Deane recovered from logs, weapons, longbows, and other objects found on the ships of Mary Rose . By 1836, the Deane brothers had produced the world's first dive manual, the Method of Using Deane Patent Dancing Tools that explains in detail the workings of equipment and pumps, plus safety precautions.
In the 1830s the Deane brothers asked Siebe to apply his skills to improve the design of their underwater helmet. Extending the improvements already made by other engineers, George Edwards, Siebe produced his own design; helmet equipped with full length waterproof canvas diving suit. The real success of the equipment is the valve in the helmet.
Siebe introduced various modifications to his wardrobe design to accommodate the rescue team's requirements on the Royal George's HMS shipwreck, including making helmets removable from corselets; enhanced designs bring up standard standardized diving outfits that overhaul underwater civil engineering, underwater dives, commercial dives, and naval dives.
Tools
An important aspect of dives provided on the surface is that the respiratory gas is supplied from the surface, either from a special dive compressor, a high pressure cylinder, or both. In commercially and militarized dives, a source of gas reservoir must always exist if the primary supply fails. Divers may also use a cylinder called a "bail-out bottle," which can provide respiratory gas in emergencies. Thus, the diver supplied from the surface is much less likely to have an "out of the air" emergency than a scuba diver because there are usually two alternative air sources available. Submarine equipment provided on the surface usually includes the ability to communicate with the surface, which increases the safety and efficiency of working divers.
The equipment provided on the surface is required under the US Navy's operational guidance to dive in the heavily polluted environment created by the Navy's Experimental Diving Unit. Submarine equipment provided on the surface is required for most commercial dive operations conducted in many countries, either by direct law, or by a legitimate practice code, as in the case of IMCA operations.
Helmet light request
The lightest demand helmet is a rigid structure that completely covers the diver's head and supplies the "on demand" breathing gas. The gas flow from the supply line activated by inhalation reduces the pressure on the helmet to slightly below the ambient, and the diaphragm in the demand valve senses this pressure difference and moves the lever to open the valve to allow breathing gas to flow into the helmet. This flow continues until the pressure inside the helmet re-balances the surrounding pressure and the lever returns to the close position. This is the same principle as that used for scuba request valves, and in some cases the same components are used. The sensitivity of the lever can often be adjusted by the diver by turning the knob on the side of the demand valve. The light-weight helmet is available in open-circuit systems (used during standard air breathing) and closed-circuit (reclamation) systems (which can be used to reduce costs when inhaling mixed gases such as heliox and trimix: exhale gas, carbon dioxide scrubbing, oxygenation back, and back to the diver).
Helmet can be made of metal or plastic reinforced composite (GRP), and either connected to the neck dam or clipped directly to dry clothing. The neck putty is the underside of the helmet, which seals the diver's neck in the same way as the neck seal of a working dry shirt. The neck dam may have neoprene or latex seal, depending on diver preferences. Attachment to the neck dam is essential for safety diverters and reliable locking mechanisms are needed to ensure that it is not inadvertently released during the dive. When using a dry suit, the neck dam can be permanently removed and the bottom of the helmet assembly is attached directly to the suit.
The term "Light" is relative; Helmet is only mild when compared with old copper hat. They are only supported by head and neck divers, and are uncomfortably heavy (Weight KM 77 = 32.43 lb) out of the water, as they have to be ballasted for neutral buoyancy during diving, so they do not tend to lift the head of the diver with excess buoyancy. There is little difference in weight between the metal shell and GRP shell helmet because of this ballasting, and its weight is directly proportional to the total volume - smaller lighter helmet. To avoid fatigue, divers avoid wearing a helmet until before entering the water. Having a helmet supported by the head has the advantage that divers can change the helmet to face the job without having to rotate the entire upper body. This is very advantageous when looking up. This allows the helmet to have a relatively small faceplate, which reduces the overall volume and hence its weight.
Demanding a respiratory system reduces the amount of gas needed for adequate ventilation diver, as it only needs to be provided when the diver inhaling, but the slight increase in respiratory work caused by this system is a loss at the extreme level of exertion, where free-flow systems may be better. The demand system is also quieter than free flow, especially during the non-inhalation respiratory phase. This can make voice communication more effective. The breath of divers can also be heard by the surface team through a communication system, and it helps to monitor the condition of the diver and is a valuable safety feature.
Open circuit request helmet
The open circuit demand system exhausts the gas to the environment at ambient pressure (or a very small difference from the ambient pressure required to open the exhaust valve). As a result, all the exhaled gas is lost to its surroundings. For most of the surface-oriented commercial dives in which air is the respiratory gas used, it does not matter, because it is cheap and freely available. Even with nitrox it is generally more cost-effective to use open circuits, because oxygen is a gas that is readily available and relatively cheap, and mixing nitrox in a simple technology, both to mix and analyze.
Retrieve the helmet
In the case of compressed air, or a mixture of Nitrox, the exhaled gas is not worth enough to justify the recycling cost, but the helium-based mixture is much more expensive, and as the depth increases, the amount of gas used (in terms of mass, or number of molecules) increases the proportion directly to ambient pressure. As a result, the cost of gas is a significant factor in deep open dive circuitry with a helium-based mix for a long time. By using the back line for exhaled gas, it can be recompressed and reused, almost indefinitely. Needed to remove carbon dioxide from reclaimed gas, but this is relatively inexpensive and uncomplicated. It is generally removed by scrubbers, which are filters that are packed with chemicals that react with and remove carbon dioxide from the gas. Reclaimed gases are also filtered to remove odors and microorganisms, and oxygen is added to the required concentrations. Gas is compressed for inter-usage storage. There is a technical problem with the recovery of exhaled gas. Only by channeling it back through the valve will not work, because the hose must be maintained at ambient pressure just inside the helmet, otherwise the gas from the helmet will flow freely under pressure, or not flow at all due to back pressure. This constraint is overcome by using the exhaust valve acting on the same principle as the demand valve, which opens the exhaust valve by using a diaphragm lever that feels the pressure difference between helmet interior pressure and ambient pressure. It requires only pressure in the reclaimed hose lower than the ambient in the diver function. The same principle is used in the respiratory system Built-in breathing system (BIBS).
Free flow helmet
Free flow helmets supply continuous airflow to the diver, and he breathes as it flows past. Breathing work is minimal, but the flow rate should be high if the diver works hard, and this is noisy, affects communication and requires hearing protection to avoid damage to the ear. This type of helmet is popular where divers have to work hard in relatively shallow water for a long time. It is also useful when diving in contaminated environments, where the helmet is sealed to a dry suit, and the whole system is kept at a slight positive pressure by adjusting the exhaust valve back pressure, to ensure that there is no leakage into the Helmet. This type of helmet is often large in volume, and because it is attached to the suit, it does not move with the head. Divers must move his body to face whatever he wants to see. For this reason, the plates are large and there are often upper windows or side windows to improve the field of vision.
Standard dive helmet (Copper hat)
Helmets are usually made of two main parts: the hood, which covers the diver's head, and the porcelain that holds the weight of the helmet on the shoulder of the diver, and is clamped into a suit to create a watertight seal. The hood is attached and sealed to a corselet on the neck, either with bolts or screw-off threads, with some form of locking mechanism.
Helmet can be depicted with the number of bolts that hold it to the setting or to the corselet, and the number of vision ports, known as lights. For example, a helmet with four vision ports, and twelve buttons securing its setting to the corselet, will be known as "four twelve-edged helmets", and a three-bolt helmet using three bolts to tighten the bonnet to the corselet. , clamping the neck flanges between the two halves of the helmet.
When the phone was invented, it was applied to standard wetsuits for excellent communication with divers.
Bonnet
Bonnet is usually a copper shell with soldered brass fittings. It covers the diver's head and provides enough space to turn the head to look out of the glass faceplate and other viewport (windows). The front port can usually be opened for ventilation and communication when the diver is on the deck, with either sideways or swung sideways on the hinges. Other lights (another name for viewports) are generally fixed. Viewports are glass on the initial helmet, with some helmets then using acrylic, and usually protected by brass or bronze lattices. Helmets have fittings for connecting air ducts and dive phones.
The helmet then includes a non-return valve in which the airline is connected, which prevents deadly fatal helmets if the pressure in the hose is lost. The difference in pressure between the surface and the diver could be so great that if the air duct breaks off the surface and no valve does not return, the diver will be partially compacted into the helmet by external pressure, and injured or possibly killed.
The helmet also has a spring exhaust valve that allows excess air to leave the helmet. The spring style is adjusted by the diver to prevent the suit from completely deflated or over-inflating and the diver floating uncontrollably to the surface. Some helmets have an extra manual exhaust valve known as spit-cock. This allows the diver to vent the excess air when he is in a position where the main exhaust can not function properly.
Corselet
The corselet, also known as the breastplate, is an oval or rectangular collar piece on the shoulders, chest and back, to support the helmet and seal it into a suit, usually made of copper and brass, but sometimes steel. Helmets are usually associated with the suit by placing a hole around the collar of the suit jacket over the bolts along the edge of the corselet, and then clamp a brass rope known as brailes against the collar with a wing nut to press the rubber against the metal. from corselet rim to make waterproof seal. An alternative method is to attach the hood to the corselet on the rubber bound to the top of the suit.
Most bonnet join the corselet with 1/8th round interrupted thread. The helmet neck thread is placed to the corselet neck facing the left front of the diver, where the yarn is not interested, and then rotated forward, pulling the thread and sitting on top of the leather gasket to create a watertight seal. Helmets usually have a safety lock that prevents the hood from rolling back and separating underwater. Other connection styles are also used, with connections secured with clamps or bolts (usually three). Some helmets are made with hood and corselet in one piece and secured to the suit in another way.
Band Mask
Mask band is a heavy duty full face mask with many characteristics of light-weight helmet. In the structure it is the front of the lightweight helmet from the top of the face plate down the request valve and the exhaust port, including bailout blocks and communication connections on the sides. This rigid frame is attached to the neoprene hood by a metal clamp band, hence its name. It is provided with a padded sealing surface around the edge of the frame held firmly against the diver's face by a "spider" rubber, setting the double strap with a pad behind the diver's head, and usually five ropes connecting to the pin on the ribbon. The rope has several holes so the voltage can be adjusted to get a comfortable seal. Mask bands are heavier than other full face masks, but lighter than helmets, and can be worn faster than helmets. They are often used by divers to prepare for this reason.
Full-face mask
Full face masks cover the mouth and nose, which reduces the risk of divers losing air supply compared to half the mask and the demand valve. Some models require bailout blocks to provide alternative gas supply from umbilical and bailout cylinders, but are unsuitable for receiving alternative air supply from rescue divers, while some models receive secondary request valves that can be fitted to port accessories (Draeger, Apex and Ocean Reef). The unique Kirby Morgan 48 SuperMask has a removable DV pod that can be removed to allow the diver to breathe from the standard scuba request valve with the funnel.
Despite the increased safety of the dives provided by safer attachments from the respirator to the diver's face, some models of full face masks can fail haphazardly if the front plate is damaged or detached from the skirt, as there is no way to breathe from the mask. This can be reduced by bringing the second standard secondary stage, and preferably also a half-spare mask.
Full face masks are lighter and more comfortable to swim than helmet or band masks, and usually provide better, but less secure, field of view and do not provide the same level of protection as heavier and stronger. equipment. Both types of equipment have different application ranges. The most complete facial mask can be adapted for use with scuba or surface supply. Full face masks are usually not equipped with bailout blocks, and these are usually installed on the diver's harness, with a single hose to supply the mask from the main gas or bailout selected on the block. Arrangement of a rope for a full face mask is usually quite safe, but not as secure as a bandmask or helmet, and it is possible to be unplugged in the water. But it's also quite practical for trained divers to replace and clean a full face mask under water without help, so this is more of an inconvenience than a disaster unless the diver is unconscious at the same time.
Diver's umbilical
The umbilical cord contains a hose to supply the respiratory gas and usually some other components. These usually include strength members, which may be a hose or rope, a communication cable (comms wire), and a pneumofathometer hose. Where necessary, hot water supply lines, helium reclamation canals, and/or video cameras and lighting cables may be included. These components are neatly arranged into multistrand cables, and placed as a single unit. The tip of the diver has an underwater connector for the power cord, and the air hose is usually connected to a helmet, mask band, or block bailout by JIC equipment. A carabiner of similar gates or connectors is provided to the power member to be installed on the diver's harness, and can be used to lift the diver in an emergency. Similar connections are provided for installation on a diving bell, if used, or to a surface gas panel and communications equipment.
Harness diver
Harness divers is a strong wicker item, and sometimes a cloth, which is fastened around the diver above the exposure suit, and allows the diver to be lifted without the risk of falling out of the harness. Several types are being used.
Jacket harness
The harness of the jacket is a vest (style) vest suit with customized woven ropes that are adjusted and securely curled over the shoulders, across the chest and waist, and through the crotch or around each thigh, so the diver can not slide under predictable circumstances. Harness is equipped with some heavy D-ring duty, fixed on the webbing in such a way that the full weight of divers and all its equipment can be safely supported. The minimum strength of 500kgf is recommended or required by some practice codes. A harness jacket is usually provided with a woven strap or cloth sack on the back to support a bailout tube, and may have a variety of pockets to carry equipment, and may also carry an unused or permanent main load. There are usually some powerful D-rings to secure umbilicals and other equipment.
Bell harness
The bel harness has the same function as using a jacket, but it does not have a fabric jacket component, and is entirely made of woven, with similar rope configurations. It may also have the means of carrying a bailout cylinder, or a bailout cylinder can be done on a separate backpack.
Utilize floating compensation
The AP Valves Mk4 Jump Jacket is a harness with an integral floating jacket specially designed for commercial diving work with helmets and bells. There is a direct feed into the jacket from the main air supply, from the pneumo line and from the bailout, and a system that allows the pneumo diver to directly connect to another dive helmet as an emergency air supply.
Airlines
Hookah, Sasuba and Snuba systems are categorized as "airline" equipment, as they do not include communication characteristics, lifeline and pneumofathometer hoses from full umbilical divers. Most hookah dives use demand systems based on the second phase of standard scuba, but there are special purpose-filled special-flow masks specifically for hookah diving (see photo). The bailout system, or emergency gas supply (EGS) is not an inherent part of the airline's diving system, although it may be required in some applications.
Their application field is very different from the full surface dives provided. Hookahs are commonly used for shallow waterworks in low-danger applications, such as archeology, aquaculture, and aquarium maintenance, but are sometimes also used for open water hunting and gathering seafood, gold mining and diamonds in shallow rivers and rivers, and bottom-down and lower maintenance other sea from the ship. Sasuba and Snuba are mainly shallow water recreation applications for low hazard sites. Sasuba Hookah diving equipment is also used for yacht or boat maintenance and gastric cleaning, pool maintenance, shallow underwater inspection.
The system used to supply air is a compressed air system that pushes air down the hose to the respirator of the diving regulator, either a 12 volt electric air pump, a gasoline engine powered engine, or some floating system of scuba tank with a flight to a diver. This hookah diving system usually limits the length of the hose to allow less than 7 meters. An exception is the gasoline engine unit, which requires a much higher level of training and supervision at the top for safe use.
An important exception to this trend is the beach-shore diving operation on the west coast of South Africa, where the hookah is still the standard equipment for gravel pebbles in surf zone hostility conditions, where water temperatures are usually about 8 to 10 Ã, Â ° C, the visibility is usually low, and spikes are often strong. The diver takes about two hours of work with crowbars and suction hoses, weighs heavily to stay in place while working, and the standard climbing method is to throw the harness and the regulators weighted and make the climb swimming freely. The next diver will be free to dive on the airline, adjust the regulator and thrashing into the harness before continuing the work. Until South African abalone fishery is closed, hookahs are the only means of dive allowed to harvest wild abalone, and some aspects of this practice are in direct conflict with diving rules at the time. Abalone Divers are not allowed to have divers ready on board.
Gas Panel
The gas panel or gas manifold is a control device to supply the respiratory gas to the diver. Primary gas and reserves are supplied to the panel via the closing valve of a low pressure compressor or high pressure storage cylinder ("bomb", "quadriceps", or "kelly"). The gas pressure can be controlled on the panel by the industrial pressure regulator, or it may be set closer to the source (on the compressor, or in the storage cylinder outlet). Supply gas pressure is monitored on the gauge on the panel, and the over-pressure valve is installed if the supply pressure is too high. The gas panel may be operated by a dive supplier if the respiratory gas or premix is ​​fixed ratio, but if the composition must be controlled or monitored during the dive, it is usually for a special gas panel operator, or "gas man" to do this work.
There is a set of valves and gauges for every diver to be supplied from the panel. These include:
- The main supply valve with a non-return valve, which supplies gas to the main umbilical gas supply hose. This is usually a quarter-turn valve, because it must be fast operating and clear whether it is open or closed.
- Pneumofathometer supply valve, which supplies gas to pneumofathometer for divers. This valve is usually near the main supply valve but with different handles. This is usually a needle-type valve because it must be well regulated, but must also be large enough to allow for a reasonably high flow rate, since air can be used as an alternate respiratory air source, or to fill a small lift bag./li>
- The pneumofathometer gauge is connected to the pneumo line. This is a high-resolution, calibrated pressure meter in seawater (fsw) and/or sea water meters (msw). and is used to measure the depth of the diver by allowing air to flow through the pneumo hose and out the ends attached to the diver. When the air supply is off, and the flow stops, the gauge shows the pressure on the open end on the diver.
- Each pneumofathometer meter has an overpressure valve to protect it against the gas supply at a higher pressure than it is designed to take. This is important because the main supply pressure is significantly higher than the maximum depth pressure on the pneumo gauge. There is also often an inhibiting valve or a hole between the pneumo line and a gauge to limit the flow to the gauge and ensure that the excess pressure valve can adequately relieve the pressure.
- Some gas panels have separate inventory gauges for each downstream dive of the supply valve, but this is not a standard practice.
The gas panel may be large enough and mounted on the board for convenient use, or may be compact and installed in a portable box, for ease of transportation. The gas panel is usually for one, two or three divers. In some countries, or under some practice codes, a surface standby diver must be supplied from a separate panel to a working diver.
Low pressure air compressor
The low-pressure compressor is often an air option for dives provided on the surface, since it is almost unlimited in the amount of air that can be provided, provided that the volume and delivery pressure are adequate for the application. Low-pressure compressors can run for tens of hours, requiring only refueling, periodic filter drainage, and occasional running checks, and therefore are more comfortable than high pressure storage cylinders for main air supply.
However, it is important for safety divers that the compressor is suitable for breathing air delivery, using the appropriate oil, adequately filtered, and taking clean and uncontaminated air. The opening position of the intake is important, and may have to be changed if the wind direction is relatively unchanged, to ensure that no exhaust gases enter the intake. National standards for inhaling air quality may apply.
Power for a portable compressor is usually a 4-stroke gasoline engine (gasoline). Larger compressor and mounted on a caravan, possibly diesel powered. Compressors installed permanently on dive support vessels are likely to be powered by a 3-phase electric motor.
The compressor shall be provided with accumulator and release valve. The accumulator serves as an additional water trap, but the main purpose is to provide a volume of pressurized air reserves. The relief valve allows excess air to be released back into the atmosphere while maintaining proper supply pressure in the accumulator.
High pressure gas reserves
An alternative to low-pressure compressors for gas supplies is a high pressure storage cylinder through a pressure regulator that will be adjusted to the required supply pressure for the depth and equipment used. In practice, HP storage can be used for backup gas supply or primary gas supply and reserves to the gas panel. High pressure bulk cylinders in quiet operation and provide gas of known quality (if tested). This allows the use of a relatively easy and reliable mixture of nitrox in the provided surface dives. Bulk cylinders also operate quietly compared to low-pressure compressors, but have limited gas available. The usual configuration for bulk gas storage provided on the surface is a large single cylinder with a capacity of about 50 liters of water, often referred to as "J" or "bomb", "quadriceps", which is a group (sometimes, but not necessarily four numbers ) similar cylinders mounted on a frame and connected together to a common supply supply, and "kellys" which are a group of "tubes" (large long volume pressure vessels) are usually installed in a container frame, and are usually connected together to a common connection connection.
Communications system
Both hard-wired and through-water electronic voice communications systems can be used with surface-supplied dives. Cable systems are more popular because there are physical connections to divers for gas supplies in any case, and adding cables does not change the handling characteristics of the system. Cable communication systems are still more reliable and more manageable than systems through water. Communication equipment is relatively easy and may be of type two wire or four wire. Two wire systems use the same wiring for surfaces for divers and divers to surface messaging, while four wire systems allow diver messages and surface operator messages to use separate wiring pairs.
In a standard two-wire system the default setting for diver communication is to have the usual diver side, so the surface team can hear anything from the diver at any time except when the surface sends the message. In a four-wire system, the side of the diver is always on, even when the surface operator is talking. This is considered an important safety feature, as the surface team can monitor dive breathing sounds, which can provide early warning of developing problems, and confirm that the diver is still alive. In a four-wire system, the diver to the surface channel can be on all the time.
Helium divers may require a decoder system (unscrambler) that reduces the frequency of sound to make it easier to understand.
The closed-circuit video is now also popular, as it allows surface personnel to see what the diver does, which is very useful for inspection work, as non-dive specialists can see the underwater equipment in real time and direct the diver to look at certain features interesting.
The dry bell may have a water-based communications system installed as a backup.
gas supply bailout
The bailout gas is usually carried by a diver in a scuba cylinder, mounted on the back of the harness in the same position as used with recreational scuba. The size of the cylinder will depend on the operational variable. There should be enough gas to enable the diver to reach a safe place in the bailout gas in an emergency. For surface-oriented dives, this may require gas to decompress, and bailout sets generally start at about 7 liters of internal capacity and can be larger.
Bailout rescue options: For bell diving there is no requirement for gas decompression, because the bell itself carries a bailout gas. But at the extreme depths the diver will use fast gas, and there are some cases where two liters of 300 bar sets are needed to supply sufficient gas. Another option that has been used for extreme depths is the rebreather bailout set. The limitation to this service is that divers should be able to get in and out of the bell while wearing bailout equipment.
Installation options: The bailout tube can be fitted with a valve at the top or bottom, depending on the local practice code. The commonly used arrangement is to install the cylinder with the valve upward, as it is better protected when sitting, and the cylinder valve is left fully open when the diver is in the water. This means that the regulator and supply hoses to the bailout block will be pressed during the dive, and ready for immediate use by opening the bailout valve on the harness or the helmet.
The bailout block is a small manifold that fits well into the harness where it is in a comfortable but sheltered position, usually on the right side of the waist strap, or on the helmet, also usually on the right side of the temple, with the sideways button valve to distinguish it from the free flow valve or defogging that is usually forward. The bailout block has a connection for the main gas supply from the umbilical through the non-return valve. This route can not be closed and supplies helmet request valves and free flow valves under normal circumstances. The bailout gas from the cylinder mounted behind the first stage of the conventional scuba in the cylinder valve, to the bailout block, where it is usually isolated by the bailout valve. When a diver needs to switch to a gas bailout he just opens the bailout valve and the gas is supplied to the helmet or mask. Since the valve is usually closed, leaks in the first stage regulator seat will cause the interstage pressure to rise, and unless the excess pressure relief valve is installed to the first stage, the hose will break. Aftermarket overpressure valves are available that can be fitted to standard low-pressure ports in most of the first stage.
Choice of bailout supply pressure: If the interstage pressure for the bailout regulator is lower than the main supply pressure, the main supply will override the bailout gas, and continue to flow. This can be a problem if the diver switches to the bailout because the main supply is contaminated. If on the other hand, the bailout pressure is higher than the main supply pressure, the bailout gas will override the main gas supply if the valve is opened. This will result in the gas bailout used if the valve leaks. Divers should periodically check that the bailout pressure is still sufficient for the remainder of the dive, and cancel the dive if not. For this reason, the bailout regulator must be equipped with a traceable pressure gauge that can be used by divers to check pressure. This is usually cut off or inserted into the harness on the left side, where it can be easily reached to read, but it is impossible to tear anything.
Floating control
Surface-supplied dives may be required to work in the water or below. They should be able to survive without effort, and this usually requires weighting. When working in the water, the diver may want to float neutrally or negatively, and while working at the bottom he usually wants to be a few pounds negative. The only time a diver may want to positively float is when on the surface or during a limited range of emergencies where uncontrolled ascent is less life-threatening than remaining under water. The surface-supplied diver generally has a safe supply of breathing gas, and there are very few opportunities where weight has to be discarded, so in many cases the dive weighing arrangements provided on the surface do not provide rapid release.
At times when the diver supplied on the surface requires variable buoyancy, it may be provided by inflation of a dry suit, if used, or by a floating control device that is essentially similar to that used by scuba divers, or both.
System weight
Divers should stay downstairs to work some time, and may need to have a neutral buoyancy over time. Diving suits are usually light, so it's usually necessary to gain weight. This can be given in several ways. Undesirable positive buoyancy is harmful to divers who may need to spend significant decompression time during the climb, so the weights are usually installed safely to prevent accidental loss.
Load belts
The belt for the provided diving surface is usually equipped with a buckle that can not be accidentally removed, and a heavy belt is often worn under the harness jacket.
Weight harness
When a large amount of weight is required, the armor can be used to carry the load on the diver's shoulder, rather than around the waist, where it may tend to slip into an uncomfortable position if the diver works in a vertical position, which often occurs. Sometimes this is a separate harness, worn under a safety harness, with a bag on the side to carry the load, and sometimes it is an integrated system, which carries a load in an installed or externally mounted bag to the safety harness.
Crop weight
If a diver needs to adjust trim for greater comfort and efficiency while working, various trim weights can be added to the harness.
Weighted shoes
Multi-style boot boots can be used if the diver will work hard. Some in the form of a clogs propped on top of boots, and the other using the tip in the lead. Ankle weights are also an option, but less comfortable. This weight gives the diver a better stability when working upright at the bottom, which can significantly improve productivity for some types of work.
Thermal protection
Economical and diving diets are used where water temperatures are not too low - more than about 65Ã, Â ° F (18Ã, Â ° C), divers will not spend too long in the water, and the water is clean enough.
Dry suits are better thermal protection than most wetsuits, and isolate divers from the environment more effectively than other exposure clothing. While diving in contaminated water, dry clothing with shoe separated, sealed dry gloves and helmets sealed directly into the suit provide the best environmental insulation. The material of the suit should be selected to fit the expected contaminants. Thermal undersuits can be matched with expected water temperatures.
The hot water suit provides an active heating which is particularly suitable for use with helium respiratory gas. Warm water is provided from the surface through the umbilical hose, and the water flow can be adjusted to meet diver needs. The heated water keeps flowing into the suit and is distributed by a hollow internal tube on the front and back of the torso and along the limbs.
Equipment maintenance and testing
All of the surface components provided by the dive system must be maintained in good working conditions and may need to be tested or calibrated at specific intervals.
Diving procedure
There are a large number of standard procedures associated with surface-supplied dives. Some of them are equivalent in scuba, and others are very different. The details will vary depending on the equipment used, because the manufacturer will specify some checks and procedures in detail, and the order may vary to some extent.
The working diver
Diving dives that work for diving are very routine, but details depend on diving equipment and tasks, and to some extent on the site, especially accessibility aspects.
Preparation for diving
Prior to the dive operation, it is usually necessary to prepare surface supply equipment. There are a number of components that need to be connected in the correct order, with checks at various stages to ensure that there are no leaks and everything is working correctly. Most dive contractors will have a comprehensive checklist that is used to ensure that the equipment is connected in the proper order and all checks are performed. Some checks are very important for the safety of divers. The compressor must be adjusted so that air is not contaminated to the intake. Filters should be checked if they need to be changed. Air supply hose will be connected to air panel and checked for leakage, umbilical connected to panel and helmet, and communications equipment connected and tested. Before the umbilical is connected to the helmet or full face mask, the umbilical should be detonated to ensure there is no impurities in it, and the non return valve on the bailout block should be tested. This is important, as it exists to prevent airflow back into the umbilical if the line is cut off, and if the diver fails may experience firing of the helmet, or flood of the neck dam.
Compared to scuba diving, dressed diver is a relatively tiring process, because the equipment is large and heavy enough, and some components are connected together by the hose. This is more so with a helmet, and less so with a light-filled face mask. It is not unusual for divers to do all the dressing without the aid of diver divers, who will also manage the umbilical during the dive.
- Exposure settings - Divers will wear appropriate exposure settings for planned dive times, gas and water temperatures, and are also affected by expected deployment levels during dives.
- Harness - After wearing an exposure suit and checking the seals and zippers, the diver will wear a suit of armor. The upper crew will usually help because the cylinder bailout will already be installed, and usually also attached to the helmet, making this a complicated procedure, easiest if the diver sits.
- Weight - The weights will be put into the diver at some time during the dressing procedure, but the stage in which this is done depends on what weighting system is used.
- Bailout - The cylinder bailout is usually tied to the harness and connected to the helmet before the diver is dressed.
- Helmets - Helmets are usually placed last, because they are heavy and uncomfortable out of the water. Some divers can wear their own helmets, but it is usually for the upper crew to do most of the locking on the neck dam, and check that there are no obvious errors with the seals.
There's a series of pre-dive checks done after the diver is locked inside the helmet, and before he's committed to the water. This must be done whenever the diver is prepared for diving.
- Command checking - Divers and comms operators check that voice communications systems work properly and can hear each other clearly. It also ensures that the operator is sure which communications channel is connected to a special diver.
- Respiratory examination - Divers inhale the main air supply to ensure that the demand valve exerts gas at low-breathing work, without free flow, and the umbilical is connected to the correct valve on the panel.
- Bailout check - Diver operates a bailout system to ensure that he/she can reach and operate the valve and that changes smoothly, the pressure in the cylinder is sufficient for the planned dive profile and ready for immediate use, and reports the bailout's readiness to the supervisor by "Active on knock on, off in hat, Pressure... blade "or equivalent.
Surface checks are performed after a diver enters the water, but before he is allowed to descend. They are checks that can not be done effectively, or at all, in the air.
- Examination of wet comms - Once in the water, comms should be checked again to make sure they are still working properly. It is possible that water will cause the coms to fail or worsen as contact becomes wet.
- Helmet seals - The helmet and neck seals should not allow water to enter the helmet. It can only be checked when in the water.
- Pneumo Bubble - Divers call the air-conditioning operator to open the pneumofathometer valve to ensure that the channel is not blocked, and connected to the correct place on the panel.
Emergency procedures
Divers should be able to handle the following emergencies. Some are life-threatening, others are more uncomfortable.
- Bailout to support gas, in case of gas supply failure from umbilical, or if main air supply is contaminated.
- Lung flame, if the main air supply is cut off, but the pneumo tube is intact. Pneumatic gas can also be supplied by a standby diver
- Voice communication failure is usually not an emergency, but it can affect the effectiveness of the work and expose the diver to a higher risk if something goes wrong. The ability to communicate with line signals can be helpful here, especially to assist in deciding whether dives should be canceled, and if there are other more urgent issues.
- Helmet flood. Depending on the severity of the flood, this may range from disruption to an emergency. The slow leak can be controlled by opening the free flow valve, which will push the flow of water out of the exhaust valve. Neck damage usually has this effect.
- The cover plate is broken. This is a real emergency, but highly unlikely because the plate is usually a crash-resistant polymer and should not break. This can be reduced by opening the free flow valve and holding the level of opening, facing down, and breathing very carefully. Small holes or cracks can be covered by hand to slow down the leak.
- Failure of the request valve. This is a minor problem if there is a free flow valve, but the dives will usually be stopped, because the bailout will not last long if necessary.
- The failure of the exhaust valve, such as the failure of the demand valve, can be handled by opening the free flow valve and ensuring a constant flow of air.
- Vomiting on the helmet. This can be a real and life-threatening emergency if it is not handled effectively, as divers can breathe in vomit and shortness of breath. Again, the action is to open the free flow valve, preferably before vomiting, and inhale as carefully as possible. If there is no free flow valve, such as a full face mask, the cleaning button should clear the request valve and oro-nasal mask, and the mask can be rinsed by lifting the lower edge of the face to let water in, before cleaning again.
- Failure of hot water supply. It can be life-threatening to dive in a heliox, and there is not much a diver can do, but soon go back to the bell.
Bell procedure and wet emergency stage
Emergency procedures for wet bells and diving stages include:
- loses the main gas supply to the bell
- Recovery of a depressed diver into a bell
- Abandon bell or stage
- Application of surface standby divers
- Loss of hot water supply (for hot water settings)
- Voice communication failure
- Positional runoff: Yellow and Red.
Standby diary
Stand by diver will be prepared in the same way as a working diver, but will not get into the water until needed. He will usually be ready for the stage of readiness to enter the water, and then will take off his mask, or remove his helmet and then will sit in a comfortable place as can be found, so that in an emergency he can get ready to act in the shortest time possible. This often means arranging some form of protection from the weather, and heat and sunlight are usually more of a problem than cold and wet. It is often necessary to cool the diver on standby to avoid overheating, and dehydration can also be a problem. When a diver works on a helmet, the diver is ready to use a full face mask or bandmask, as this makes it quicker to enter the water in an emergency. Stand by the job of the diver is to wait until something goes wrong, and then sent to finish it. For this reason, a diver must be one of the best diver on the team about the skills and power of diving, but not necessarily an expert in job skills for a particular job. When deployed, ready divers will usually follow umbilical diver in difficulty, because unless it has been disconnected, it will be reliable to lead to the right divers. The idle diver should maintain communication with the supervisor during the dive and is expected to comment on ongoing progress so that the superintendent and the surface crew know as much as possible what is happening and can plan accordingly, and must take the necessary steps to resolve the incident, which may involve emergency air supply or seek and save the wounded or unconscious divers. In bell diving, the bellman is a ready-made diver, and may have to recover a depressed diver to the bell and provide first aid if necessary and possible.
The rescue auction is a short or woven strap with a clip on one or both ends, used by a stand-by diver to trace an unresponsive diver into his belt to free both hands during recovery. This can be useful if he needs to climb structures, shotlines or topographic features, and umbilicals can not be used safely to lift the diver due to obstacles or sharp edges.
Occupational health and safety issues
Divers face certain physical and health risks when they dive underwater with scuba gear, or use high-pressure breathing gas.
Hazard is any agent or situation that poses a level of threat to life, health, property, or the environment. Most hazards remain inactive or potential, with only theoretical danger risk, and when the dangers become active, and produce unintended consequences, it is called an incident and may culminate in an emergency or accident. Hazards and vulnerabilities interact with the likelihood of occurrence to create risks, which can be the probability of undesirable special consequences of a particular hazard, or the possible combination of unintended consequences of all the dangers of a particular activity. Understood and recognized hazards may pose lower risks if appropriate precautions are taken, and the consequences may be less severe if mitigation procedures are planned and in place.
The presence of a combination of several hazards simultaneously is common in diving, and the effect generally increases the risk for divers, especially when an incident occurs because one danger triggers another with a cascade generated from the incident. Many dive victims are the result of a cascade of incidents that plagued divers, who must be able to manage any predictable incidents. The use of respiratory gas provided on the surface reduces one of the most significant dangers in dives, namely loss of gas supply, and reduces the risk by using appropriate emergency gas supplies, usually in the form of scuba bailout sets, intended to provide divers with respiratory gas enough to reach a relatively safe place with more gas breathing available.
The risk of a lost or ineffable diver is also dramatically reduced compared to most scuba, because the diver is physically connected to the umbilical surface control point, making it relatively easy for the diver to go to the diver in distress, and the standardized application of preprogrammed voice communications allows the surface team to continuously monitor the dive breathing sounds.
The rated dive risk will generally be deemed unacceptable if the diver is not expected to address a predictable incident with the possibility of significant events during the dive. Exactly where the line is drawn depends on the circumstances. Professional dive operations tend to be less tolerant of risk than recreation, especially technical divers, which are less restricted by workplace health and safety laws and guidelines. This is one of the factors driving the use of equipment provided on the surface where it is practical enough for professional work.
Diving disorder is a special medical condition arising from underwater diving. These signs and symptoms may be present during the dive, on the surface, or up to several hours after the dive. The surface-supplied diver must breathe a gas that has the same pressure as the environment (ambient pressure), which can be much larger than the surface. Underwater ambient pressure is increased by 1 standard atmosphere (100 kPa) for every 10 meters (33 feet) depth.
The main disruptions are: decompression disease (which includes decompression disease and embolism of arterial gases); nitrogen narcosis; high-pressure nerve syndrome; oxygen toxicity; and pulmonary barotrauma (lung burst). Although some of these may occur in other settings, they are of particular concern during diving. Long-term diverting disorders include dysbaric osteonecrosis, which is associated with decompression disease. This disorder is caused by the high-pressure breathing gas encountered at depth, and the diver can breathe different gas mixtures from the air to reduce this effect. Nitrox, which contains more oxygen and less nitrogen, is commonly used as a respiratory gas to reduce the risk of decompression disease in depths up to about 40 meters (130 feet). Helium may be added to reduce the amount of nitrogen and oxygen in the gas mixture while diving deeper, to reduce the effects of narcosis and to avoid the risk of oxygen toxicity. It's complicated at an outer depth of about 150 meters (500 feet), because a mixture of helium-oxygen (heliox) then causes a high-pressure nerve syndrome. More exotic mixtures such as hydreliox, a hydrogen-helium-oxygen mixture, are used at extreme depths to counteract this.
Dive compressor
Compressor diving is the surface dive method used in some tropical marine areas including the Philippines and the Caribbean. Divers swim with half masks covering the nasal fins and (often made at home) and supply air from boats with plastic hoses from low-pressure industrial air compressors of a kind commonly used to supply jackhammers. There is no reduction valve; the diver holds the end of the hose in his mouth without the valve or the request funnel. Excess air spills out through the lips. If several people dive the compressor from the same vessel, some tender lanes are needed inside the ship to stop the airline from being caught and flexed and obstructed.
Compressor diving is the most common method used for fish for Caribbean spiny lobsters ( Panulirus argus ) in the Caribbean. However, it is illegal because it contributes to overfishing, damaging the environment, and harmful to the health of fishermen. When fishing with compressors, fishermen either use gaffs or spears to spear lobster immediately after seeing, killing or injuring lobsters before they can be checked for eggs or assessed as legal size. Compressors allow fishermen to catch fish in deeper waters for longer periods of time, facilitating reef damage as fishermen search for lobsters hidden beneath corals and spots
Source of the article : Wikipedia
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