Buried cables

Elastomers based on PTMEG have excellent microbial and fungus resistance. Their hydrolytic stabiUty make these elastomers prime candidates for use ia ground-contact appHcations, for example, as jacketing material for buried cables. Because of their good biocompatibiHty, they have also found uses ia medical appHcations, such as catheter tubiag. 

The switching-off method for 7/ -free potential measurement is, according to the data in Fig. 3-5, subject to error with lead-sheathed cables. For a rough survey, measurements of potential can be used to set up and control the cathodic protection. This means that no information can be gathered on the complete corrosion protection, but only on the protection current entry and the elimination of cell activity from contacts with foreign cathodic structures. The reverse switching method in Section 3.3.1 can be used to obtain an accurate potential measurement. Rest and protection potentials for buried cables are listed in Table 13-1 as an appendix to Section 2.4. The protection potential region lies within U[[Pg.326]

Laying and burying cable, including cable and earthworks (58 DM m ) DM 600... 

Buried sensors are electronic devices that are designed to detect potential intruders. The sensors are buried along the perimeters of sensitive assets and are able to detect intruder activity both aboveground and belowground. Some of these systems are composed of individual, stand-alone sensor units, while other sensors consist of buried cables. 

Automation equipment at the metering sites generate production volume information, indicate alarm and other equipment status, and provide some control capability. This equipment is connected to remote terminal units (RTU) at optimum points within the field by individual wire pairs of buried cable. The RTU s store the information generated and, on request from the computer, transmit it to the computer center by means of microwave or wireline. RTU s also receive messages from the computer for transmittal to appropriate equipment for execution. 

During the consolidation period, all conventional operations in the unit were placed on CDC to allow reservoir surveillance and accounting allocation. As meter sites were constructed, conventional operations were discontinued and automatic well testing was made available by CPC. Sixteen meter sites, four RTU s, and one I/O device were added to the existing automation system. Approximately 9.S miles (1S.3 km) of buried cable were installed to connect meter sites and RTU s. 

Because of its chemical inertness, lead has also been popular as a covering for underground cables, such as buried cables that carry telephone messages, and for pipes through which liquids are transported. For many years, lead was the material of choice in the construction of water pipes since it was inert to most chemicals occurring in nature and easily shaped. With the recognition of lead s threat to humans, however, many of these applications have been discontinued. 

Metallic lead is occasionally used as an extruded sheath to provide protection against chemical corrosion where it is necessary to bury cables in polluted or aggressive soils. Examples of these are found in chemical plants, refineries, storage tank farms and areas that have high water tables. 

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. 

Machinery, including cranes, hoists, and forklifts Public access and perimeter fencing Adjacent facilities Buried cables Overhead cables... 

Detecting cables can be more difficult due to their smaller size. A surface laid cable should be detectable with a high resolution sonar survey. Buried cables may be located with a magnetometer if the cable carries electrical current or has steel armouring. Otherwise specialised cable tracking techniques would need to be employed. For further information, it is recommended that the user contact a specialist marine survey company to advise on the best option to use. 

Specialized cable installation vessels and underwater cable installation equipment are also used to bury cable from the ESP to the onshore connection point. Once the installation process is complete and before normal operations of the wind farm can begin, the turbine must be commissioned. For financial reasons, on larger wind farms the turbines are... 

Even the schematic diagrams of Figs. 11.1a and b indicate that a leak monitoring system comprises components for which various durability requirements are valid. Buried cables and sensors under the geomembrane can only be repaired at very great expense if at all. Cables and sensors... 

There are three operations that carry the highest risk of electrocution use of portable tools, striking a buried cable, and cranes and diggers making contact with overhead power lines. 

Health and Safety Executive, Guidance Notes GS6, Avoidance of Danger from Overhead Electric Lines (1977) GS33, Avoiding Danger from Buried Cables. HMSO, London... 

In trenching installations, a trench is dug in the earth to an appropriate depth, usually 75 cm or more, and the cable or cables placed into it. The minimum depth of the trench used depends on a number of factors, but deeper is generally better from a protection standpoint. However, deeper trenches are also proportionally more expensive to make. The trench is then backfilled with a variety of materials to protect the cable, such as clean sand or soil. Direct buried installations are typically marked with tapes laid parallel to the cable, but placed closer to the surface, and markers located visibly above the surface, in an effort to prevent dig-ups. Buried cables are typically connected to one another via hermetically sealed closures located in buried hand holes or manholes along the route. These closures house and protect the splices or connectors used to connect sections of cable. 

Direct buried cable experiences fewer environmental extremes than aerial cable. This cable is usually laid into a trench or potentially plowed into the soil. Primary dangers to underground cable are dig ups and rodent damage. Rodent resistance of the cable is provided by a coated steel tape armor. Installation in a duct offers additional protection from rodents, as well as dig ups. Some guidelines follow ... 

When planning a direct buried cable route, locate and avoid existing utilities. 

Impressed Current Cathodic Protection for Corrosion Control of Underground and Buried Cable Plant," Bellcore, LP-RPES-COR, Bellcore, Livingston, NJ, 1987. 

The preparation of a site requires the complete removal of some trees and the de-branching of others. An overhead power line crosses the site and buried cables may be present. Describe a safe system of work for ... 

Electrocution from striking an underground cable can be spectacular when it occurs and the most effective precaution is to obtain clearance from the local Electricity Board or the location s electrical engineer that the ground is clear of cables. If doubt exists, locating devices are available that enable underground cables to be traced. Excavations near buried cables should be by hand. 

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