Diving works

The three-bolt diving gearThe diving works

DIVING WORKS (EN: diving operations; DE: Unterwasserarbeiten; FR: travaux de plongement; ES: trabajos bajo el agua; RU: водолазные работы) is the totality of the operations, which are performed underwater by the divers.

Within the mining craft, they use the diving works during the engineering surveys (during the oceanographic, geophysical, and geological exploration), and during the operation of the underwater built structures and equipment for the extraction of the petroleum and gas on the coastal shelf, namely, the mothballing, recommissioning, or liquidation of the boreholes, and during the monitoring of the condition of the built structures (see the Figure # 1), during the cleaning of the surfaces against the fouling, during the cinema, photo, and television recording, during the visual observations, during the construction of the underwater built structures (of the foundations and basements, during the laying of the pipelines and cables, during the welding and repairing-mechanical works, and so on), and also during the emergency rescue works.

There are used for the diving works the special diving gear (see the Figure # 2) and equipment.

According to the method of the delivery of the gas mixture, the diving gear is divided into autonomous (the gas mixture is located within the gas cylinders of the breathing apparatus), and hose-type, in case of which the breathing mixture is delivered from the surface through the hose from the gas cylinders on the deck of the vessel. They produce the diving gear with the continuous delivery of the gas mixture (the ventilated three-bolt gear, and GKS-3m injector-regenerative gear), and with the periodic delivery (only during the moment of the inhalation), namely, the aqualung. According to the method of the usage of the breathing mixture, they distinguish the gear with the open scheme of the breathing (all exhaled mixture is ejected into the water), with the closed scheme (all exhaled mixture is used repeatedly after the purification), or with the semi-closed scheme (the exhaled mixture is used partly repeatedly after the purification). During the diving works at the depth of up t o 20 metres, there is usually used the autonomous gear with the exhalation into the water, while at the depth of up to 60 metres, there is used the hose-type gear (of the three-bolt type, the aqualung of the hose-type variant), and at the depth of more than 60 metres, there is used the hose-type diving gear with the closed and semi-closed schemes for the breathing.

The diving equipment ensures the preparation and storage of the gas mixtures, the descent and ascent of the diver to the place of the work under the water, and the possibility of the performance of the underwater works by this diver. There belong to the structure of this equipment the decompression chambers, the hyperbaric chambers with the systems for the life support, the diving bell with the lowering-lifting device, or the underwater vehicle, the means for the underwater lighting and communication, the underwater tools for the work of the divers, and so on. The hyperbaric chambers usually have the dwelling and sanitary compartments, are equipped with the systems for the life support (gas supply, water supply, ventilation and purification of the gas medium, air conditioning, communications, lighting, television), and with the apparatuses for the monitoring-measurement and medical monitoring. The diving bell has the systems for the delivery of the gas mixture, of the hot water fo r the heating of the bell and clothing of the divers, the systems for the communications with the surface, for the lighting, for the emergency life support, and for the television. For the performance of the diving works, there are used the underwater tools with the electric and hydraulic mover (the jackhammers, grinding wheels, and others), and the welding aggregates (for the electric cutting and welding). For the technical inspection of the underwater structures, there are used the special apparatuses for the non-destructive monitoring, and the underwater photo, cinema, and television apparatuses.

They perform the diving works using the methods of the prolonged and brief submersion. In case of the brief submersion, the diver, under the conditions of the normal barometric pressure, puts on the diving gear, descends under the water, performs the work, and ascends onto the surface with the compliance with the regime of the decompression. During the work at the depth of up to 60 metres, there is used as the breathing mixture the compressed air, which is purified of the harmful admixtures, while at the depth of more than 60 metres, there is used the helium-oxygen or air-helium mixture. The divers descend with the speed of 10-20 metres per minute, and the staying on the ground amounts to, as a rule, at most 60 minutes. The more is the time of the work on the ground and the depth of the submersion, the longer is the time of the decompression. For example, in case of the descent to the depth of 60 metres, with the staying of the divers on the ground during 60 minutes, the duration of the decompression is approximately 6 hours, while in case of the descent to the depth of 200 metres, with the staying on the ground during 45 minutes, the duration of the decompression is 72 hours.

The diving works for the repair of the pipelinesThe effectiveness of the diving works using the method of the brief submersion decreases abruptly with the increasing of the depth of the descent, thus in case of the diving works at the great depths, they use the method of the prolonged submersion, in case of which the divers live during the long time (up to a month) within the hyperbaric chambers within the artificial gas medium, which is compressed to the pressure, which is corresponding to the working depth of the submersion, and these divers daily descend within the diving bell onto the ground for the performance of the underwater works. During the work under the water, the divers use the gear with the closed or semi-closed scheme for the breathing, the clothing with the water heating, and the telephone communications with the corrector of the speech of the diver within the helium-oxygen medium. Within the diving bell, there usually descend three divers, one diver remains within the bell and ensures the delivery of the breath ing mixture, and of the water for the heating, while other two divers exit to the place of the work. They conduct the decompression one time, after the termination of the entire complex of the works.

For the transportation of the divers to the place of the work, they also use the underwater vehicles with two compartments, namely, one compartment with the normal barometric pressure for the driver, and another compartment with the pressure, which is corresponding to the working depth of the diving descent. The usage of the underwater vehicles is more effective, than the usage of the diving bells, because the usage of the underwater vehicles permits us to perform the diving works at the significant distance from the place of the parking of the swimming means, and to deliver to the place of the work, together with the divers, the director of the works, and the representative of the customer. The admission to the diving works is performed by the diving-qualification commission, on the basis of the examination of the knowledge, and on the basis of the conclusion of the diving-medical commission.