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Standard diving dress (also known as hard-hat or copper hat equipment, or heavy gear) is a type of diving suit that was formerly used for all underwater work which required more than breath-hold duration, and included marine salvage, civil engineering, pearl shell diving and other commercial diving work, and similar naval diving applications, though has largely been superseded by lighter and more comfortable equipment.
Contents
- Early history
- Development of the standard diving dress
- Developments beyond the standard diving dress
- General description
- Suit
- Helmet
- Bonnet
- Corselet
- Air control valve
- Divers weights
- Weighted shoes
- Divers knife
- Manufacturers
- References
Standard diving dress consists of a diving helmet made from copper and brass or bronze, an air hose from a surface supplied diving pump, a waterproofed canvas suit, 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.
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. Standard diving dress is also sometimes known in the US as a Diver Dan outfit from the television show of the same name.
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 pants.
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.
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 from the discovered Mary Rose shipwreck timbers, guns, longbows, and other items.
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 the HMS Royal George, 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 Renayrouze 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 (1867). 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 600 feet (180 m) 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 20m, and the DM40 mixed gas rebreather which used an oxygen cylinder and an air cylinder for the gas supply for depths to 40m.
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 divers 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 over 80 kilos.
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 (bib) was made of the same material as the suit and pulled up inside the corselet and around the diver's neck. The wrist cuffs are also made of vulcanized rubber.
The twill was available as heavy, medium, and light grades, with the heavy having the best resistance to abrasion and puncture against rough surfaces like barnacles and rocks. 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. The legs may be laced to reduce 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.
Helmet
The helmet is usually made of two main parts: the bonnet, which covers the diver's head, and the corselet which supports the weight of the helmet on the diver's shoulders, and is clamped to the suit to create a watertight seal. The bonnet is attached and sealed to the corselet at the neck, either by bolts or an interrupted screw-thread, with some form of locking mechanism.
The helmet may be described by the number of bolts which hold it to the suit or to the corselet, and the number of vision ports, known as lights. For example, a helmet with four vision ports, and twelve studs securing the suit to the corselet, would be known as a "four light, twelve bolt helmet", and a three-bolt helmet used three bolts to secure the bonnet to the corselet, clamping the flange of the neck seal between the two parts of the helmet.
When the telephone was invented, it was applied to the standard diving dress for greatly improved communication with the diver.
Bonnet
The bonnet is usually a copper shell with soldered brass fittings. It covers the diver's head and provides sufficient space to turn the head to look out of the glazed faceplate and other viewports (windows). The front port can usually be opened for ventilation and communication when the diver is on deck, by being screwed out or swung to the side on a hinge. The other lights (another name for the viewports) are generally fixed. Viewports were glass on the early helmets, with some of the later helmets using acrylic, and are usually protected by brass or bronze grilles. The helmet has fittings to connect the air line and the diver's telephone.
Later helmets include a non-return valve where the airline is connected, which prevents potentially fatal helmet squeeze if the pressure in the hose is lost. The difference in pressure between the surface and the diver can be so great that if the air line is cut at the surface and there is no non-return valve, the diver would be partly squeezed into the helmet by the external pressure, and injured or possibly killed.
Helmets also have a spring-loaded exhaust valve which allows excess air to leave the helmet. The spring force is adjustable by the diver to prevent the suit from deflating completely or over-inflating and the diver being floated uncontrollably to the surface. Some helmets have an extra manual exhaust valve known as a spit-cock. This allows the diver to vent excess air when he is in a position where the main exhaust can not function correctly.
Corselet
The corselet, also known as a breastplate, is an oval or rectangular collar-piece resting on the shoulders, chest and back, to support the helmet and seal it to the suit, usually made from copper and brass, but occasionally steel. The helmet is usually connected to the suit by placing the holes around the rubberised collar of the suit over bolts along the rim of the corselet, and then clamping the brass straps known as brailes against the collar with wing nuts to press the rubber against the metal of the corselet rim to make a water-tight seal. An alternative method was to bolt the bonnet to the corselet over a rubber collar bonded to the top of the suit.
Most bonnets are joined to the corselet by 1/8th turn interrupted thread. The helmet neck thread is placed onto the neck of the corselet facing the divers left front, where the threads do not engage, and then rotated forward, engaging the thread and seating on a leather gasket to make a watertight seal. The helmet usually has a safety lock which prevents the bonnet from rotating back and separating underwater. Other styles of connection are also used, with the joint secured by clamps or bolts (usually three). Some helmets were made with the bonnet and corselet in one piece and secured to the suit in other ways.
Air control valve
Most divers have a screw-down air control valve on the air hose to control air flow rate into the helmet. The early helmets did not have air control valves and the diver signaled the surface with pulls on his rope or air line, indicating that he needed more or less air.
Diver's weights
There are two weight systems, both are still in use. The older helmet weights are used in pairs. The large horse shoe type weights hold the helmet down and are attached to the corselet with figure eight hooks that go over the breast plate weight studs. The Greek sponge divers simply joined the weights with ropes which went over the corselet like saddle bags. The other weight type is the weight harness, which is a weight belt that fastens around the waist with shoulder straps which cross at the back and go over the breast plate. The US Navy Mk V weight belt weighed 83 lb, but commercial belts were usually about 50 lb.
Weighted shoes
The helmet divers used heavily weighted shoes to steady them on the bottom. The weighted sole is bolted to a wooden insole, which in turn has a leather, canvas or rubber upper. Lead was the most common sole and a pair could weigh up to 34 lb. Brass soled shoes with canvas uppers were introduced in WWII and are still in use. Some early brass shoes were called sandals because they were a casting held to the diver's feet by simple straps. Japanese divers often used iron soled shoes. The diver tends to lean forward against the drag of the water when walking on the bottom, and could often not see where he was putting his feet, so the toes are capped, usually with brass.
Diver's knife
The diver's knife is a tool, not a weapon. The diver can pry and hammer with it as well as cut. It usually has one side of the blade serrated to cut heavy lines such as thick rope, and a sharper edge for fine lines such as monofilament fishing line and nets. There are two general styles of knife sheaths; one is flat with a spring retention and the other is tube-shaped and has an ajax triple thread, allowing the diver to insert the knife in it in any orientation. He then rotates the knife, to engage the threads and lock the knife into the sheath.