Earthing joint

The Dong Pao Mine is jointly operated by Lai Chau-VIMICO Rare Earth Joint Stock Co. and the Japanese Dong Pao Rare Earth Development Company (Talk Vietnam 2012). 

The following equations are derived from Figure 3.8. Here, sheath grounding at earthing joints is ignored, but sheath grounding at substations can be considered through Vj ... 

The proposed formulas are known to have a satisfactory accuracy for planning and implementation studies. An acceptable level of error is introduced by the impedance matrix reduction discussed earlier. Owing to the matrix reduction, unbalanced sheath currents that flow into the earth at earthing joints are not considered in the proposed formulas. 

Calculate zero- and positive-sequence currents using EMTP for the sample cable in Section 3.2.4. For this calculation, assume that the lengths of a minor section and a major section are 400 and 1200 m, respectively. As the total length of the cable is 12 km, the cable will have 10 major sections. Grounding resistance at earthing joints should be set to 10 Q. 

Since the three-phase sheath conductors are short-circuited and grounded in every major section as illustrated in Figure 3.6, the sheath voltages of three phases are equal at each earthing joint. Assuming sheath currents are balanced among three conductors, the sheath currents do not flow into the earth at each earthing joint ... 

The resistance of graphite to thermal shock, its stabiUty at high temperatures, and its resistance to corrosion permit its use as self-supporting vessels to contain reactions at elevated temperatures (800—1700°C), eg, self-supporting reaction vessels for the direct chlorination of metal and alkaline-earth oxides. The vulnerabiUty of cemented joints in these appHcations requires close tolerance ( 0.10 mm) machining, a feat easily accompHshed on graphite with conventional metal machining equipment. 

There are four commonly occurring states of stress, shown in Fig. 3.2. The simplest is that of simple tension or compression (as in a tension member loaded by pin joints at its ends or in a pillar supporting a structure in compression). The stress is, of course, the force divided by the section area of the member or pillar. The second common state of stress is that of biaxial tension. If a spherical shell (like a balloon) contains an internal pressure, then the skin of the shell is loaded in two directions, not one, as shown in Fig. 3.2. This state of stress is called biaxial tension (unequal biaxial tension is obviously the state in which the two tensile stresses are unequal). The third common state of stress is that of hydrostatic pressure. This occurs deep in the earth s crust, or deep in the ocean, when a solid is subjected to equal compression on all sides. There is a convention that stresses are positive when they pull, as we have drawn them in earlier figures. Pressure,... 

Fractures, fissures, and joints are openings in sedimentary rocks formed by the structural (mechanical) failure of the rock under loacls caused by earth crust tectonics. This form of porosity is extremely hard to evaluate quantitatively due to its irregularity. 

Portable electrical hand tools and equipment shall be properly grounded and wound to operate on llOV a.c. center tapped to earth supply, and shall only be connected to the system by permanent joints or proper connections. 

Patterson s extraordinary polar studies, published with Murozumi and Chow in 1969, provided the first clear evidence that air pollution reaches even the most remote areas of the Earth. As he often did, Patterson listed his colleagues names before his own on the article s list of authors in some joint projects, he did not include his name at all. It will be better for your career, he told one young man. Years later, he listed some of those articles in a geology department brochure describing faculty accomplishments. The flier was an unobtrusive way of stating for the record that those research projects had been his work too. 

McCormick, P.G., Alonso, T., Lincoln, F.J., Parks, T.C. and Schaffer, G.B. (1992) Rare earths, science, technology and applications. Proceedings of an International Symposium held jointly by TMS and AusIMM during the TMS Annual meeting, eds. Bautista, R.G. and Jackson, N., San Diego, California, March 1-5, p. 247. 

Dike walls should be constructed of compacted earth, concrete, or solid masonry, and designed to be liquid tight. The dikes should be designed to withstand full hydrostatic head, fire, earthquake, wind, and rainfall exposure. Piping penetrations should be provided with liquid-tight expansion joints and sleeves or packing. 

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