Underground systems

Critical Equipment Equipment, instrumentation, controls, or systems whose malfunction or failure would likely result in a catastrophic release of highly hazardous chemicals, or whose proper operation is required to mitigate the consequences of such release. (Examples are most safety systems, such as area LEL monitors, fire protection systems such as deluge or underground systems, and key operational equipment usually handling high pressures or large volumes.)... 

Modern-day designs are more sophisticated than the early, simple separators of a few decades ago that were introduced by the petroleum industry. Commercial systems are comprised of cylindrical vessels, rectangular vessels, above and underground installations. Figure 29 shows an underground system advertised by Tank Direct. 

Electric Drainage means of electric protection of an underground system against the corrosive action of stray currents arising from a d.c. electric traction system employing one or more connections (drainage bonds) made between the system to be protected and the return circuit of the traction system (rail, return current feeder, negative busbar of the sub-stations). 

Sufficient sectional block valves should be provided so that sections of the underground system can be taken out of service for repairs without undue interruption of the fire water protection. For example, the sectional block valves should be located so that a combination of no more than five resources, such as hydrants, monitors, water spray systems, etc. would be out-of-service at any given time. Sectional block valves should be provided at no more than 800 ft (243 m) intervals for long runs of pipe. 

Note that the production facility declared by Japan was Satyam 7, located at Kamikuishiki, formerly used by the religious cult Aum Shinrikyo which released the nerve gas sarin on the Tokyo underground system on 20 March 1995. 

This method uses a more active metal than that in the structure to be protected, to supply the current needed to stop corrosion. Metals commonly used to protect iron as sacrificial anodes are magnesium, zinc, aluminum, and their alloys. No current has to be impressed to the system, since this acts as a galvanic pair that generates a current. The protected metal becomes the cathode, and hence it is free of corrosion. Two dissimilar metals in the same environment can lead to accelerated corrosion of the more active metal and protection of the less active one. Galvanic protection is often used in preference to impressed-current technique when the current requirements are low and the electrolyte has relatively low resistivity. It offers an advantage when there is no source of electrical power and when a completely underground system is desired. Probably, it is the most economical method for short life protection. 

As discussed earlier, NFPA 13011 is another important document, because it is used for the regulation of train and underground system, by authorities having jurisdiction over local rail systems in some U.S. systems, some Canadian ones, and some Asian ones. Table 21.6 shows the reaction-to-fire requirements for rail cars. NFPA 130 also includes requirements for stations and trainways as well as rail vehicles. The key issues to be considered in stations are the same as in other assembly occupancies, namely electrical, interior finish, upholstered furniture, decorations, and trash disposal. With regard to trainways, the standard looks at the effect of areas that are potentially concealed spaces and considers that factor. 

A catastrophic explosion and major fire occurred within a major refinery as operations prepared a system for valve maintenance. This refinery stored a flashing flammable fluid (isobutane with a boiling point of 11° F or —12° C) in two spherical tanks. The spheres connected to an alkylation unit via a 10-inch (25 cm) line. Operating line pressure was about 50 psig (345 kPa gauge) and one of the valves in this underground system was in an open pit. [9]... 

Hydrogen gas is sometimes naturally found in geological structures recently, crushed basalt and H20 in the dark under anaerobic conditions was found to generate H2. This would account for natural emissions and explain the energy source for bacteria growing in underground systems.3... 

Traced pipe performs better with a nonwicking insulation which has low thermal conductivity. Underground systems are very difficult to keep dry permanently. Methods of insulation include factory-preinsulated pouring types and conventionally applied types. Corrosion can occur under wet insulation. A protective coating, applied directly to the metal surface, may be required. 

The inherent disadvantages of the underground system are high first cost, inconvenience, and excessive cost of maintenance. Overhead construction is often used since it can be installed at about one-third the cost of the underground system, and repairs can be quickly made. However, such lines are exposed to impairment by weather, lightning, trucks, cranes, and corrosion, so that overhead construction should be avoided in congested areas where a reliable and safe electrical system is necessary. 

Ants are a comparatively minor contributor to soil formation and organic matter decomposition. The common ants of the temperate climates construct an extensive underground system of galleries that may extend several feet into the soil. They live as a colony and sometimes entertain aphids as guests in their nest. They feed largely on living and dead insects. Their chief role in soil formation lies in their transport of subsoU to the surface. 

Portland cement, invented in 1892 by Joseph Aspdin of Leeds, was so called because it resembled expensive Portland stone (at least to the eye of the inventor). It is made from about 80 % limestone and about 20 % clay. It was widely adopted because it possessed superior qualities to the older quicklime-based material, including the especially important property of being able to harden in damp conditions. This latter property was especially valuable at a time when tunnel constmction was widespread, including amongst other projects, the London underground system. 

System provides WEB data (Deng Wei 2007) query function users can query real-time underground monitoring equipment on the Internet, to facilitate the timely understanding of the operation situation of the underground system. 

Figure 6. Operational Managerial interdependence between the Power supply Metro underground systems.

MODERNISATION OF DISTRIBUTION SUBSTATIONS WITHIN MUNICIPAL UNDERGROUND SYSTEMS... 

The practical utilization of MCA8 software application is demonstrated on the following multi-criteria decision-making task, which consists in determination of the order of distribution substations (DSs) in municipal underground systems. 

To illustrate the implementation of remote-controlled systems within electrical distribution networks and their contribution to improvement in reli-abftity of electric energy supply to customers, we conducted an analysis of effects produced by the remote-controlled devices (Distribution substations within municipal underground system. Section switch-disconnectors and circuit-breakers in over-head hnes) to operation parameters of a selected section of the electrical distribution network in the Northern Moravia (Czech Republic). 

Control valve— wall post indication valve (PIV) or open screw yoke (OS Y) if control valve is not provided in underground system for each inside system. 

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