Cables excavation

Where there is available ground and the specific resistivity of soil in the upper layers is low, the anodes are laid horizontally [3]. A trench 0.3 to 0.5 m wide and 1.5 to 1.8 m deep is dug with, for example, an excavator or trench digger (see Fig. 9-2). A layer of coke 0.2-m thick is laid on the bottom of the trench. The impressed current anodes are placed on this and covered with a 0.2-m layer of coke. Finally the trench is filled with the excavated soil. No. IV coke with a particle size of 5 to 15 mm and specific gravity of 0.6 t m" is backfilled at a rate of 50 kg per meter of trench. The anodes are connected in parallel and every three to four anode cables are connected to the anode header cable by a mechanical cable crimp encapsulated in an epoxy splice kit to give an economical service life at high current output. 

The need for metrics is particularly important in process safety, in no small measure because the hazards may not be readily evident. Unlike some other safety risks where dangerous situations are more apparent—such as unsafe scaffolding, unsecured cables, trenches, and other excavations—information on the status and safety of hazardous containment systems (e.g., internal corrosion, an improperly sized relief valve) is not generally visible. Without a constant and reliable flow of information on process safety performance and management systems, leaders may, in essence, be flying blind. 

Marking or physically protecting (with creosoted boards, for example) electrical cables and process piping that is laid within an excavation, for protection against future excavations. 

Typical applications of GPR surveys include, mapping depth to bedrock, and mapping interfaces including changes in soil type, geologic formations, and depth to water table. Buried objects and excavations may also be located and in some cases identified, as well as buried cultural features including pipes, cables, and conduits (13). 

Animal fat and oil processors Animal manure removers Artificial-flavour makers Asphalt storage workers Barium carbonate makers Blast furnace workers Brewery workers Bromide-brine workers Cable splicers Caisson workers Carbon disulphide workers Cellophane producers Chemical laboratory workers (lecturers, students, technicians) Cistern cleaners Citrus root fumigators Coal gasification workers Coke oven workers Copper-ore sulphidisers Depilatory makers Dye-makers Excavators Felt makers... 

Most cables used in oil industry plants are installed for at least part of their length in exposed machinery areas or on trays or ladders. This exposure can permit mechanical damage to occur to the cables e.g. objects falling on to them or impacting into them. Even buried cables are at risk from excavation mistakes, e.g. digging machines. 

Excavation work Excavation and digging work with the hazard of damaging buried pipelines, cables, sewage etc. Opening of pavements... 

Shovel An excavating or coal-loading machine that uses a bucket mounted on and operated by means of a handle or dipper stick that moves longitudinally on gears and is lifted or lowered by cable. The entire machine is mounted on crawlers for mobility, and the upper structure is mounted on rollers and rail for swing or turn. 

The percentage of notifications is equal to 100%. The new one-caU system makes notification compulsory and sanctions are also introduced. It is estimated that a total of 270,000 activities per year take place near cables and pipelines. As 40,000 times a year a cable or pipeline is hit by an excavator (NEN 2004) it is not very likely that an excavator can perform digging activities systematically without a notification, even if enforcement is done only at random. In addition, not legally prescribed measures such as hehcopter patrols will locate digging activities that have not been notified. 

Underground services, and in particular buried electrical cables, must be identified before any excavation is made. 

Diego was using the vmderground sensing device to detect and mark the presence of fiber optic cables, natural gas and water pipelines, electric transmission lines, or sewer lines. He had to finish the task by midmorning when the excavation crew was going to begin work. 

Later that morning the excavation crew broke ground. Five minutes later, in the area that Diego wasn t able to get checked, they struck a fiber optic cable. Two minutes after that the utility crew arrived to identify and mark the underground installations. 

Cable Cover. A fired clay (in this context generally, but erroneously, known as earthenware ) or concrete conduit for covering underground electric cables these covers warn of the cable s presence and protect it from excavating tools. For specification see B.S. 2484. 

There are several major accidents caused each year by contact with buried services during excavation work. In a recent case, a man was digging a hole with a spike when he struck a high voltage electrical cable causing a massive explosion and serious injuries for him. 

Much excavation work is needed to repair mains (water or gas), piped services or cables (electrical power or telecommunications) which are feeding occupied buildings. It is crucial that there is effective communication between the excavation contractors and the building occupants throughout all stages of the project. The pipe or cable must be isolated before work begins. If the work... 

Excavations will be supported as appropriate. Where flooding risk exists, cofferdams/caissons will be installed with pumps of suitable capacity. Substantial barriers will be erected around excavations. Where poor ventilation is identified the atmosphere will be continually monitored. A permit to work will be used. Stop barriers will be used to prevent vehicle entry. Spoil and materials will be stacked at least 1.5 m from the edge of excavations. Ladders will be provided for safe access/egress. Cable location devices and local authority drawings will be used to trace buried services prior to commencement of work. Suitable signs and barriers will be provided to warn of the work. 

Supervisors must have received training in COSHH appreciation, general site safety, theory and practice of excavation work. Operatives must have received training in excavation support procedures and use of cable location devices. This applies to sub-contractors as well as direct employees. 

Street works present particular hazards to pedestrians and many of these hazards are discussed in Chapters 7, 8, 9 and 10. Work on a pavement or road is hazardous for both members of the public and the construction workers. Pavements should be kept clear of tripping hazards, such as trailing cables. The site must be well lit at night. Road traffic past the site may also need to be controlled to protect the workforce. Members of the public and traffic vehicles must also be protected from the elbows of loaders, excavators and cranes which may swing into their path. More detailed advice is available from the Code of Practice Safety at street works and road works related to the New Roads and Street Works Act 1991. The following points for the protection of pedestrians should be considered when work in streets or similar areas is being planned ... 

The trend in loading machines in the last ten years has been steadily away from cable-operated face shovels and towards the increasing use of wheel loaders and hydraulic excavators. The diagram in Fig. 4 illustrates this development, which is representative of about 65% of German cement production. 

Mechanization of loading in quarries started with the introduction of the cable-operated excavator, more particularly the face shovel, which is still on the market and available from many manufacturers and in many sizes. With its bucket fixed immovably to the arm, the diesel or electrically powered face shovel is purely a loading machine. Its relatively high capital cost can be justified by long service life, often twenty years or more. Larger machines generally last longer than smaller ones. 

On the other hand, hydraulic excavators are usually at a disadvantage in having a shorter service life and a lower degree of operational availability than the cable-operated excavator. Although the drive and hydraulic units are generally so designed as to be readily exchangeable and renewable, repairs nevertheless require more skill and care. 

---