Dräger Review, Dräger, saturation divers, commercial ...€¦ · Dräger review 106 | 3/2012 9 SATUTrA iON DiviNg Focus Welding on the seabed wking at depths of several hundred

Dräger review 106 | 3 / 2012

Extreme Conditions: Safety systems safeguard the lives of saturation divers working at depths of several hundred meters

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9Dräger review 106 | 3 / 2012

SATUrATiON Div iNg Focus

Welding on the seabedworking at depths of several hundred meters below the ocean surface, commercial divers are exposed to extreme conditions. Sophisticated technology enables them to work in this hostile environment and helps safeguard their lives.

B eyond the blue pressurized door is a completely different world – a world of stainless steel, recliner

seats with white plastic covers mounted on the wall, and a high-pressure water-fog fire extinguishing system mounted just below the ceiling. Over to the left is a lad-der that leads down, through a narrow tube, to the level below. The lower level

is the mirror image of the setup above, except for the fact that bunk beds are mounted along the wall. This is how one might imagine a space station. Here too, the habitat is designed to support life un-der extreme conditions – but life deep un-der the sea, rather than in space.

For the divers on board the Norwe-gian vessel Seven Havila, this strange- P

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Deep-sea diving technology has changed comprehensively in recent decades

A closed system: Modern diving

support vessels like the seven

Havila (above) are built around the saturation suite.

During operation, divers live in pressurized

chambers (left)for up to four

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looking environment is home. They spend up to 28 days at a time in this con-fined system of chambers and tubes, which comprise of their living and sleep-ing quarters, with passages to lavatory facilities and the two diving bells. When the divers are inside, the pressure rises to many times above the atmospheric level. They breathe a mixture of helium and ox-ygen known as heliox.

In the North Sea, for example, the divers work six-hour shifts. The Seven Havila is certified for work at depths of up to 300 meters below sea level. But in order to dive for long periods, the human body needs to acclimatize to the condi-tions that exist at such depths. The greater the pressure the body is subjected to dur-ing a dive, the longer the time required to decompress afterward. In extreme cases, several days can be needed for decompres-sion. By way of comparison, only a couple of minutes are required to decompress af-ter sport dives near the surface.

Diving as a family tradition

“Three to four weeks in extremely cramped quarters is a long time, but you get used to it,” says Neil Ward, a deep-sea diver specialist. A Scotsman by birth, Ward has worked as a commercial diver for 22 years. The job is something of a family tra-dition: “My grandfather was a diver, and today my brother and I are following in his footsteps.” Ward has dived off the African coast, but apart from that, his workplace is in the North Sea – either off the Norwe-gian or the British coasts.

The jobs he does are often similar in nature – installation, construction, >

A Closed System: Modern diving

support vessels like the Seven

Havila (above) are built around the saturation suite.

During operation, divers live in pressurized

chambers (left)for up to four

weeks

Life ten kilometers below the surfaceThe original form of underwater diving is known as free-diving. This is where divers simply hold their breath during the dive. The world depth record for male free-divers currently stands at 200 meters. If human beings are to remain underwater for longer than a single breath, they require an artificial supply of compressed breathing gases.

Here we have some mammals – such as elephant seals or spearm whales: they can dive longer than an hour (see page 30f.). In fact, some animals are able to survive at much greater depths. In 2012 an expedition conduct ed by the University of Aberdeen, to the bot-tom of the Kermadec Trench off the coast of New Zealand discovered large amphipods (Alicella gigantea). They live at a depth of over ten kilometers, where the pressure is 1,000 times greater than at sea level.

The ancients were very interested in the use of technical aids that allowed them to stay underwater for long periods of time. Back in the fourth century BC, for example, Alex-ander the Great is said to have ex-plored the depths inside a diving bell. Similarly, there are contemporary accounts more than 2,000 years old of frogmen attacking enemy ships underwater, pearl divers collecting molluscs from the seabed, and divers salvaging sunken ships or carrying out underwater repairs to harbor walls.

Deep Diving: Sperm wales can reach up to 3,000 meters

maintenance, and repair – they can vary from straightforward to reasonably dif-ficult. The installations are almost al-ways in the oil and natural gas indus-try: the drilling platforms, pipelines, and other huge steel constructions that are required to bring these precious resources to the surface. Anyone who wants to work in this environment as a commercial or saturation diver must not only be an expert diver, but also be able to weld and install equipment according to industrial standards.

Ward’s employer is the UK company Subsea 7. He has been working on the Seven Havila, one of the most modern vessels of its kind, since 2011. “Up to six divers can work simultaneously on the seabed,” explains Shift Manager Peter Alexander. That’s currently the industry maximum, he adds. During such oper-ations, the vessel’s two diving bells are lowered with up to four divers each on board. One always remains in the bell for safety reasons.

“Saturation diving has advanced enormously in recent decades,” Alexan-der says. He should know, since he him-self once worked as a saturation diver. “I was there when this form of diving was first introduced in the North Sea over 35 years ago.” What hasn’t changed, Alexan-der explains, are the demands made on the people in the job: “You’ve got to be a total team player who can deal with stress and adapt to new situations.”

A fully automated diving system

At least the technology on board the vessel does relieve the diving crew of the com-

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12 Dräger review 106 | 3 / 2012

plicated business of having to manually regulate the gas pressure, mixture, and temperature. Indeed, saturation diving would be a lot more complicated without the fully-automated immersion system installed on the Seven Havila. The ves-sel was commissioned last year. The div-ing system, which was supplied by Dräger, was the largest of the key components to be delivered. It includes the hyperbaric chambers; a gas system with control tech-nology, pipes, and storage elements: in addition to fire and rescue equipment.

When the captain surrenders control

Whenever the divers are below the sur-face, the Seven Havila is completely op-erated from Dive Control on A Deck. Everything else is subordinate to it. “As soon as the diving bells enter the water, Dive Control takes over,” Alexander con-firms. “From that moment onward, the operating crew, rather than the captain, has complete control over the vessel. The vessel is therefore operated bottom-up, as it were, rather then top-down.” Most of the components of the diving system had to be manufactured indi-vidually. “There are very few standard parts,” says Per-Arne Spreemann. An air-craft engineer by training, Spreemann was one of the people at Dräger respon-sible for extending the automation soft-ware. In order to create a safe, robust, and comfortable system, Dräger intro-duced a number of innovative and cus-tomized solutions. “That’s also why we consulted at an early stage with the Nor-wegian classification society Det Norske

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Ready to dive: Two pressurized diving bells docked to the saturation suite in a diving support vessel. In them professional divers can be at overpressure, and let down up to several hundred meters work depth

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A basic principle emergesIn the early days of diving, a common solution for the problem of providing an underwater supply of oxygen was to run an air line to the surface. The snorkel principle, however, functions only in shallow waters. At a depth of 20 meters, the pressure is already three times atmospheric pressure. This demands a somewhat different approach. The first standard diving suits – equipped with helmets – were developed around 1800. These were supplied with respiratory air compressed by a pump and then delivered via an air line from the surface.

Along with the technology, the physiology of diving was developed. This includes in particular the prevention and treatment of decompression sickness. This occurs when the pressure falls too quickly as divers ascend. In this process, gases dissolved in the blood and body tissues – particularly nitrogen – form bubbles that can then block blood vessels and damage tissue and nerves. Other com plications that can result from diving include the “rapture of the deep”, the result of a too high nitrogen concentration in the body.

Portable devices that supply breathing gas for divers have been around for about 100 years. “We’ve been involved in the development of such apparatuses from the very start,” says Oliver Schirk, a diving expert at Dräger. As early as 1912, Dräger unveiled a closedcircuit breathing apparatus – now commonly known as a rebreather – which was worn with a traditional diving suit and a helmet. In modern rebreathers, soda lime is used to “scrub” carbon dioxide from the exhaled air before fresh oxygen is added. The milestones in Dräger’s development of rebreather apparatus range from the “Leutnant Lund” of 1953 to the current LAR 5000 and LAR 7000 for military use and mine clearance divers. In the 1930s, Dräger also began developing a compressedair breathing apparatuses. Today the company supplies the PSS Dive for professional users. Dräger has also been involved in diving research from the earliest days of this discipline. In 1913, for example, the company began operation of a deepsea diving simulator in Lübeck and then introduced a decompression apparatus in 1917.

In addition to scuba diving, there are also modern forms of helmet diving with the use of an external air supply and specialist fields such as saturation diving. Finally, there is the socalled atmospheric diving suit (ADS). This is more like a minisubmarine which protects the diver against the extreme water pressure while providing the required mobility to carry out work underwater. IL

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SATURATION DIV ING Focus

When divers are in action, Dive control has command over the ship

Escape route to the hyperbaric lifeboat

HyperbaricLifeboat

chamber 1:• Transfer chamber for

up to six people• Living, sleeping, and

lavatory area

Chamber 2: Living and sleeping area for six divers

chamber 4/5: • Transfer chamber to diving bells

• Lavatory area for chambers 2 and 3

Chamber 3: Living and sleeping area for six divers

Diving Bells

Living under pressure When they are not working deep underwater, saturation divers live in pressure chambers. These suites comprise of their living, sleeping, and sanitary areas. Diving bells and hyperbaric lifeboats complete the system

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Focus SATURATION DIV ING

Veritas – or DNV – which would later be responsible for approving the whole sys-tem,” Spreemann explains.

It’s a warm summer’s day, the 120-me-ter-long and 23.45-meter-wide Seven Havila is tied up to a fitting-out quay in the Norwegian port of Stavanger. There is a deafening screech of angle grind-ers – work is going on everywhere. The vessel is in port for recertification. The strict Norwegian regulations stipulate an-nual or even semi-annual inspection in-tervals, depending on the system in ques-tion. The divers’ quarters at this time are empty and spooky. But it is extremely busy in the diving center, because all the sys-tems are being checked. “In the past, the pressure, mixture, temperature, and var-ious other parameters were all controlled manually via different valves,” Alexander explains. Today everything is done with the click of a mouse.

Pressure increases with depth

According to Alexander, the principle of saturation diving has remained essen-tially unchanged. Used exclusively in com-mercial diving, this procedure involves divers living permanently, in an environ-ment pressurized to the level that exists, at the depth at where they work. As a rule of thumb, water pressure increases by one bar for every ten meters of depth. In other words, the water pressure at a depth of ten meters is twice the atmospheric pres-sure, at a depth of 100 meters over ten bar, and at 300 meters over 30 bar. The record depth reached by means of saturation div-ing is 534 meters. This was achieved in the 1980s. During trials in a pressurized

Peter Alexander (in a test run here) monitors operations while divers are below the surface. Now shift Manager on the seven Havila, since he himself once worked as a saturation diver

Working with historical equipment provides a highly realistic insight into diving heritage

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21st century helmet diver: Neil Wark is a saturation diver for subsea 7. His specialization is mostly in demand for jobs in the oil and gas industry. He relies on state-of-the art gas technology from Dräger during operations

chamber, a simulated depth of over 700 meters was reached.

To even breathe at such pressure cre-ates considerable strain on the human body. What must be avoided at all cost are the rapid changes of pressure. Even when ascending from minimal depths, divers need to make decompression stops in or-der to give the body time to get rid of ni-trogen dissolved in the tissues.

Regular decompression is no lon-ger possible in saturation diving. “When working at great depths for a number of hours, you need to allow up to an hour of decompression time per meter,” explains Wark. To avoid this problem, the divers live in an environment pressurized to the equivalent atmosphere which exists at the depth underwater where they are work-ing. At the same time, they breathe a spe-cial mixture of gas, principally a mixture of helium and oxygen known as heliox. This prevents the onset of nitrogen nar-cosis at greater depths.

99 Percent Recycled

The two pressurized diving bells con-nected to the living and sleeping quar-ters are also under the same high pres-sure. These bells are used to transport the divers from their hyperbaric environment on board the Seven Havila to their work sites deep under the sea. The vessel is also equipped with two hyperbaric lifeboats, which provide a refuge for the divers in the event of fire or an accident.

The gas mixture inhaled by the divers includes helium. The use of this noble gas requires the presence of sophisticated technology on board the Seven Havila. >

Diving history in actionWhen members of the UK’s Historical Diving Society (HDS) attend a harbor festival, the attendees hold their breath. At these performances, the diving enthusiasts climb into bulky diving suits and heavy metal helmets, some dating back to the very early days of commercial diving, and disappear into the murky depths. Yet it’s much more than just the equipment that people find fascinating about such demonstra-tions – after all, helmet diving equipment is still in common use today by commercial

divers. Equally appealing is the opportunity to experience the use of historical gear under real-life operating conditions. In fact, this expertise is increasingly being exploited these days by the film industry. “We often get requests for help with historical film and TV productions,” confirms HDS Secretary Mike Fardell.

The HDS was founded in 1990, and it now has around 200 members in the UK and an additional 100 around the world. According to Fardell, there are also historical diving societies in Australia, Denmark, Germany, Finland, France, Italy, Canada, Norway, Poland, Spain, Russia, Sweden, Slovenia, the Czech Republic, and the U.S.

The society does not concentrate on either a specific type of diving or a specific era of diving history. “Our members are interested in the complete history of diving, which ranges from people swim-ming underwater while holding their breath, to the early forms of diving equipment and right through to the very latest developments,” Fardell explains.

In recent years, the HDS has been able to realize its long-harbored dream of having its very own museum. This new museum is located in Gosport, Hampshire, on the coast of southern Eng-land. Opened in 2011, it is housed in a Victorian battery that forms part of the defenses of Portsmouth Harbor. The museum is run by HDS members, many of whom have a background in military, com-mercial, or recreational diving.www.thehds.comwww.divingmuseum.co.uk

Pioneer: A Dräger closed-circuit breathing apparatus from 1912. It was worn with a helmet

Research: Dräger equipment enabled prolonged diving trials at nine bar in 1914 P

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Living under pressure: Home to the divers for several weeks at a time, Dräger’s pressure chamber is installed in the belly of the Norwegian diving support vessel Seven Havila

The precise management of gas parameters is vitally important for diver safety and for the efficient use of resources

This is because helium is not only highly volatile, but also too expensive to be sim-ply released back into the atmosphere. “Instead, the gas mixture exhaled by the divers is reprocessed and 99 percent of it is recycled,” explains Spreemann, the ex-pert at Dräger.

Attached to the mother ship by an umbilical cord

When they are underwater, the diving bells are connected to the vessel by a bundle of lines and cables several hun-dred meters in length. This “umbili-cal cord” comprises of lines for inhaled and exhaled air, power and communica-tion cables, and a line for warm water, which is used to heat the diving suits in the icy temperatures that prevail at such depths. These multistrand bundles de-scend to each diving bell through “moon-pools” – two 4.80-meter diameter open-ings in the hull, through which the bells can be directly lowered into the water from inside the ship. In turn, the div-ers are connected to the diving bells by their very own um bilical cords, which are about 30 meters in length. By way of backup, both the bells and the diving suits are equipped with an emergency supply of breathing gas. For the divers be-low, it is vital to know not only that they can trust the crew on the surface vessel unconditionally, but also that all the vi-tal systems are maximally reliable and possess dual redundancy. Peter Thomas

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Interview: GTÜM President Dr. Karin Hasmiller about standards in diving medicine.www.draeger.com/106/diving




“For naval frogmen, diving is simply a means to an end”

Lieutenant Jens Höner has trained mine clearance divers and naval frogmen. He talked with the Dräger Review about the various diving units used by Germany’s Federal Armed Forces.

Lieutenant Höner, in what areas do the Federal armed Forces use divers?Most military divers are in the navy – ordinary divers, naval divers, mine clearance divers, and frogmen – but there are some in the army, too: the sapper divers, who are trained in Percha on Lake Starnberg, in Bavaria. What kind of work do the various navy diving units typically undertake?Ordinary divers are naval personnel who have completed a diving course. They sail on board naval vessels in another capacity, but they may also be required to undertake small repairs or inspections of the hull. Naval divers, by contrast, are specialists who are used for underwater salvage, maintenance, and repair operations, sometimes during the periods when the vessel is in port. As a rule, they work with surface air lines and are trained to use hydraulic tools and conduct various tasks underwater, ranging from flame-cutting and welding to drilling. Mine clearance divers are trained to clear ordnance of all kinds both underwater and on land – as in Afghanistan, for example. They are trained in all aspects of explosive ordnance disposal and are also capable of recovering and disposing of munitions from the two World Wars. As far as frogmen are concerned, diving is merely a means to an end, namely, to get them to a mission and back from it. Their tasks include reconnaissance, anti-piracy missions, and sometimes even land-based missions, occasionally in cooperation with the KSK, the Special Forces Command Unit.What qualifications do you need to have in order to work as a diver in the navy?In the first instance, you need no special qualifications at all, but you do need to have the right physical condition for diving. Prospective divers first of all have to pass the so-called TUVK test at the Naval Institute of Maritime Medicine. This test assesses their general suitability for employment as divers, submarine personnel, and frogmen. Potential users of closed-circuit breathing apparatuses are also tested for their oxygen tolerance. All of the candidates must also pass a fitness test before they can be admitted to the training program. During their training, maritime divers have the opportunity to take the Industry and Chamber of Commerce exam in order to qualify as commercial divers.

Diverse gases, stored in pressurized tanks, are transported by a network of lines on board the vessel. the whole system is controlled by state-of-the-art computer technology

Living under pressure: Home to the divers for several weeks at a time, Dräger’s pressure chamber is installed in the belly of the norwegian diving support vessel seven Havila

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Dräger Review, Dräger, saturation divers, commercial ...€¦ · Dräger review 106 | 3/2012 9 SATUTrA iON DiviNg Focus Welding on the seabed wking at depths of several hundred