Commercial Diving - Equipment
Inshore and Offshore commerical diving require a comprehensive panoply of equipment and surface level support. The equipments hallmarks tend to be functional, robust and task oriented.
Most commerical divers use the highly praised Kirby-Morgan superlight (KMsl.) as their breathing systems Head Unit. It has seen many revisions since being introduced in the 1960s and the current model 'in vogue' is the Mk 27b (pictured). The KM is normally connected via an umbilical which includes an airline to the surface. Aside from providing air/nitrox/heliox gas into the helmet the KMsl is also fitted with voice communication to the surface support team. There is a second inlet which allows a small 'bailout' bottle to be connected as well. The KMsl. seals at the neck with a yoke clamp-seal allowing the entire head to be kept dry. As added redundancy the nose and mouth are enclosed inside an inner mask which allows the KM to support life even if the face visor is compromised. It is from this and the earlier dive helmets that 'Hard-Hat' Diving takes its nick-name.
In the States a commercial diver often has to lug a KMsl from job to job!
The lifeline to which the commercial diver relies upon for his life-support, communications and often warmth. The umbilical is made up of up to five cables which are all bound tightly together The respective ends connect into a sophisticated compressor, Head Unit and drysuit if applicable. The outer material is normally very tough composite Kevlar/PVC with supporting inner layers. Note the reinforcing ring that takes the strain if the umbilical goes taut. At a pinch it is possible to use the umbilical to effect an evacuation!
Insulation & harness
As far as insulation goes wetsuits are rarely used. Rugged and hard wearing drysuits are more commonly seen with neoprene or membrane types being equally suitable. However even the insulation provided by a drysuit can be overwhelmed by the freezing conditions at greater depths and breathing highly conductive mixed gases (heliox). This in turn is overcome by the imaginatively named 'Hot Water Suit' (HWS). As the name suggests it is part of a highly effective 'radiator pump' that sucks sea-water into a heater at the surface and then pumps it down the umbilical into the HWS that can keep a diver cosy and warm for hours on end. Just don't mention any jellyfish that get sucked into the thing! Dry gloves can be vital for commercial work as dexterity required for awkward tasks will flag without them(note the pictured example where they have been gaffer taped to the HWS). The harness allows for a large number of weights to be attached as well as the bail-out bottle.
For dives on air down to 65 Meters the Wet Bell is usually deployed. Its a working platform which transports hard-hat divers to their work area. The umbilicals are often stored here and the communications and lighting are also housed in the bell. As the air pressure inside is equalised from the surface this creates an 'Air Pocket' allowing the upper body of the divers to be kept dry. This is useful as a psychological 'safe-zone' in an emergency. Compressed air is often stored outside the bell for emergency use. On the ascent after the works finished the wet bell stops at the required deco-stops (which can vary in time and depth).
For depths beyond 65 meters a dry bell is used. The Dry bell allows commerical divers who are saturation dive trained to operate at depths of up to 400 meters using exotic breathing gases. The Dry bell is exactly that, for its dry inside allowing divers to sleep and recover during down-time. The gas blend normally used used is Heliox (Helium and Oxygen) but there are others. The Heliox mix is and excellent blend for very deep operations but at extreme depth a small amount of nitrogen is added to counter an anomaly triggered by the water pressure. Divers working from a dry bell normally operate on a shift basis, one diver works outside the bell and the other rests whilst acting as a stand-by diver for any problems his co-diver may encounter. The Bell is pressurized to the depth the divers are working at and stays there for the duration of the job which can take days. This eliminates repeated and time consuming decompression trips and saves on cost. At the end of the operation the Dry Bell is winched back to the surface platform and hooked up to the main recompression chamber for a lengthy decompression which can last days!
The bread and butter of commercial diving is often considered the hyperbaric chamber. From here divers can be run on Surface Decompression Tables post-dive operations and monitored under the Life Support Technicians careful eye. Operating one of these devices takes experience and good training. Under an efficient and careful operator the divers will have nothing to worry about. Whereas an operator who isn't so good will have the divers voice their concerns through the intercom! Hyperbaric chambers otherwise known as recompression / decompression chambers are found:
In navy bases, Dive Support Vessels and commercial diver training establishments. Other places include hospitals and some wealthy health clinics.
Tools of the Trade
Depending on the country you work from in the commercial diving industry will dictate what personal tools you're required to bring with you to the job. A good quality knife is often considered essential for cutting through tough cabling and material. Top of the brand list is a 'Green River' brand of dive knife, though some divers make do with any old knife as they often end up blunt and rusty by the end of the job!
Specialised tools underwater machine tools are part and parcel of underwater work, without going ballistic on details the main ones are:
Welding tools, Cutting and burning tools, drilling tools and surveying tools.
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