Standard diving dress
Standard diving dress, also known as hard-hat or copper hat equipment, deep sea diving suit, or heavy gear, is a type of diving suit that was formerly used for all relatively deep underwater work that required more than breath-hold duration, which included marine salvage, civil engineering, pearl shell diving and other commercial diving work, and similar naval diving applications. Standard diving dress has largely been superseded by lighter and more comfortable equipment.
Standard diving dress consists of a diving helmet made from copper and brass or bronze, clamped over a watertight gasket to a waterproofed canvas suit, an air hose from a surface-supplied manually operated pump or low pressure breathing air compressor, a diving knife, and weights to counteract buoyancy, generally on the chest, back, and shoes. Later models were equipped with a diver's telephone for voice communications with the surface. The term deep sea diving was used to distinguish diving with this equipment from shallow water diving using a shallow water helmet, which was not sealed to the suit.
Some variants used rebreather systems to extend the use of gas supplies carried by the diver, and were effectively self-contained underwater breathing apparatus, and others were suitable for use with helium based breathing gases for deeper work. Divers could be deployed directly by lowering or raising them using the lifeline, or could be transported on a diving stage. Most diving work using standard dress was done heavy, with the diver sufficiently negatively buoyant to walk on the bottom, and the suits were not capable of the fine buoyancy control needed for mid-water swimming.
History
Early history
In 1405, Konrad Kyeser described a diving dress made of a leather jacket and metal helmet with two glass windows. The jacket and helmet were lined by sponge to "retain the air" and a leather pipe was connected to a bag of air. A diving suit design was illustrated in a book by Vegetius in 1511.Borelli designed diving equipment that consisted of a metal helmet, a pipe to "regenerate" air, a leather suit, and a means of controlling the diver's buoyancy. In 1690, Thames Divers, a short-lived London diving company, gave public demonstrations of a Vegetius type shallow water diving dress. Klingert designed a full diving dress in 1797. This design consisted of a large metal helmet and similarly large metal belt connected by leather jacket and trousers.
Development of the standard diving dress
The first successful diving helmets were produced by the brothers Charles and John Deane in the 1820s. Inspired by a fire accident he witnessed in a stable in England, he designed and patented a "Smoke Helmet" to be used by firemen in smoke-filled areas in 1823. The apparatus comprised a copper helmet with an attached flexible collar and garment. A long leather hose attached to the rear of the helmet was to be used to supply air – the original concept being that it would be pumped using a double bellows. A short pipe allowed breathed air to escape. The garment was constructed from leather or airtight cloth, secured by straps.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 helmets were built, by German-born British engineer Augustus Siebe. In 1828 they decided to find another application for their device and converted it into a diving helmet. They marketed the helmet with a loosely attached "diving suit" so that a diver could perform salvage work but only in a full vertical position, otherwise water entered the suit.
File:Divers - Illustrated London News Feb 6 1873-2.PNG|thumb|left|upright|Siebe's improved design in 1873, from the Illustrated London News. The helmet's basic features can be seen: A helmet, supplied with air from the surface, and a waterproof suit. The [|corselet] of the helmet is clamped onto the suit with wingnuts, which can be seen being tightened by one of the support crew on the left of the picture.
In 1829 the Deane brothers sailed from Whitstable for trials of their new underwater apparatus, establishing the diving industry in the town. In 1834 Charles used his diving helmet and suit in a successful attempt on the wreck of Royal George at Spithead, during which he recovered 28 of the ship's cannon. In 1836, John Deane recovered timbers, guns, longbows, and other items from the recently rediscovered wreckage of the Mary Rose.
By 1836 the Deane brothers had produced the world's first diving manual, Method of Using Deane's Patent Diving Apparatus, which explained in detail the workings of the apparatus and pump, plus safety precautions.
In the 1830s the Deane brothers asked Siebe to apply his skill to improve their underwater helmet design. Expanding on improvements already made by another engineer, George Edwards, Siebe produced his own design: a helmet fitted to a full-length watertight canvas diving suit. The real success of the equipment was a valve in the helmet that meant that it could not flood no matter how the diver moved. This resulted in safer and more efficient underwater work.
Siebe introduced various modifications on his diving dress design to accommodate the requirements of the salvage team on the wreck of, including making the helmet be detachable from the corselet; his improved design gave rise to the typical standard diving dress which revolutionised underwater civil engineering, underwater salvage, commercial diving and naval diving.
In France in the 1860s, Rouquayrol and Denayrouze developed a single-stage demand regulator with a small low pressure reservoir, to make more economical use of surface supplied air pumped by manpower. This was originally used without any form of mask or helmet, but vision was poor, and the "pig-snout" copper mask was developed in 1866 to provide a clearer view through a glass faceplate on a copper mask clamped to the neck opening of the suit. This was soon improved to become a three-bolt helmet supported by a corselet. Later versions were fitted for free-flow air supply.
Later the standard helmet was modified for use with helium mixtures for deep work. This incorporated a carbon dioxide scrubber attached to the back of the helmet, with a venturi powered circulation system to recycle the gas, making it effectively a semi-closed circuit rebreather, much like the Dräger bubikopf helmet rebreather system.
Developments beyond the standard diving dress
More recent diving helmet designs can be classified as free-flow and demand helmets. They are generally made of stainless steel, fiberglass, or other strong and lightweight material. The copper helmets and standard diving dress are still widely used in parts of the world, but have largely been superseded by lighter and more comfortable equipment.General description
Standard diving dress can be used up to depths of of sea water, provided a suitable breathing gas mixture is used. Air or other breathing gas may be supplied from hand pumps, compressors, or banks of high pressure storage cylinders, generally through a hose from the surface, though some models are autonomous, with built-in rebreathers. In 1912 the German firm Drägerwerk of Lübeck introduced their own version of standard diving dress using a gas supply from an oxygen rebreather and no surface supply. The system used a copper diving helmet and standard heavy diving suit. The breathing gas was circulated by using an injector system in the loop. This was developed further with the Modell 1915 "Bubikopf" helmet and the DM20 oxygen rebreather system for depths up to, and the DM40 mixed gas rebreather which used an oxygen cylinder and an air cylinder for the gas supply for depths to.Another unusual variation was the "pig-snout mask" of Rouquayrol-Denayrouze, which used a copper full-face mask clamped to the diving suit, which was structurally similar to the front of a copper helmet, and functioned in much the same way. It tended to sit quite far forward, making it inconvenient except when looking down, but was quite popular among German amber divers, as they spent most of their time looking down at the bottom.
A continuous flow of compressed air is provided to the helmet and vented to the surrounding water at a pressure very close to the ambient pressure at the exhaust port, which lets the diver breathe normally. The helmet must have a non-return valve at the air inlet port of the helmet, to prevent massive and fatal squeeze, should the air line be cut at the surface. Diving helmets, while very heavy, displace a great deal of water and combined with the air in the suit, would make the diver float with his head out of the water. To overcome this, some helmets are weighted on the corselet, while other divers wear weighted belts which have straps that go over the corselet. Some helmets have an air inlet control valve, while others may have only one control, the exhaust back-pressure. Helmet divers are subject to the same pressure limitations as other divers, such as decompression sickness and nitrogen narcosis.
The full standard diving dress can weigh.
Suit
The earliest suits were made of waterproofed canvas invented by Charles Mackintosh. From the late 1800s and throughout most of the 20th century, most suits consisted of a solid sheet of rubber between layers of tan twill. Their thick vulcanized rubber collar is clamped to the corselet making the joint waterproof. The inner collar was made of the same material as the suit and pulled up inside the corselet and around the diver's neck. The space between the bib and corselet would trap most condensation and minor leakage in the helmet, keeping the diver dry. The sleeves could be fitted with integral gloves or rubber wrist seals and the suit legs ended in integral socks.The twill was available in heavy, medium, and light grades, with the heavy having the best resistance to abrasion and puncture against rough surfaces like barnacles, rocks, and the jagged edges of wreckage. Vulnerable areas were reinforced by extra layers of fabric. Different types of dress are defined by the clamping of the collar seal to the rim of the corselet or to the joint between bonnet and corselet, and the number of bolts used for this purpose. The legs of the suit may be laced at the back to limit inflated volume, which could prevent excess gas from getting trapped in the legs and dragging an inverted diver to the surface. In normal UK commercial diving activities, the legs often did not have the lace up option.
The rubberised fabric was waterproof, as was the seal to the helmet and the cuff seals, so the diver remains dry – a big advantage during long dives – and wears sufficient clothing under the suit to keep warm depending on the water temperature and expected level of exertion. The suit was usually a very baggy fit on the diver, and if over-inflated, would be too bulky to allow the diver to reach the control valves for air supply and exhaust. This contributed to the risk of suit blowup, which could cause an uncontrollable buoyant ascent, with high risk of decompression illness. To add to this problem, a runaway ascent could cause sufficient internal pressure to burst the seal at the corselet, which could result in a loss of buoyancy, and the injured diver sinking back to the bottom in a flooded suit. Consequently, divers would ensure that they remained sufficiently negative when underwater to minimise this risk. The bulkiness of fit, weighted boots and lack of fins made swimming impracticable. At the surface the diver could struggle a short distance using the arms, but underwater would normally walk on the bottom and climb up and down over obstacles, taking care to avoid passing under anything that could foul the air hose.