Leakage cracks

Feb. 1975 Another steam generator leakage sodium/water reaction (800 kg) and sodium fire for 2 h, no explosion effects. Cause of leakage cracks on tube surfaces had not been detected during inspection... 

Where the LBB approach cannot be applied effectively, a determination of pipe break locations and dynamic effects is made. These are identified in CESSAR-DC, Section 3.6.2. The criteria used to define pipe break and/or crack locations and configurations are given in CESSAR-DC, Section 3.6.2.1. Postulated ruptures are classified as circumferential breaks, longitudinal breaks, leakage cracks, or through wall cracks. Each postulated rupture is considered separately as a single postulated initiating event. 

Real materials, particularly polymers, exhibit complex phenomena, such as hysteresis, electrical leakage, crack growth, and others. Later chapters in this section will explore the detailed characterization and modeling of realistic dielectric elastomer... 

Sizing of 3-D Surface Cracks with Complex Cross-Sections and Different Orientations Using Leakage Field. 

The algorithm contains five minimisation procedures which are performed the same way as in the method " i.e. by minimisation of the RMS between the measured unidirectional distribution and the corresponding theoretical distribution of die z-component of the intensity of the leakage field. The aim of the first minimisation is to find initial approximations of the depth d, of the crack in the left half of its cross-section, die depth d in its right half, its half-width a, and the parameter c. The second minimisation gives approximations of d, and d and better approximations of a and c based on estimation of d,= d, and d,= d,j. Improved approximations of d] and d4 are determined by the third minimisation while fixing new estimations of d dj, dj, and dj. Computed final values dj , d/, a and c , whieh are designated by a subscript c , are provided by the fourth minimisation, based on improved estimations of d, dj, dj, and d . The fifth minimisation computes final values d, , d, dj, d while the already computed dj , d/, a and c are fixed. 

The reason for these results is that the intensity of the leakage field and the RMS error used depend strongly on the parameter c and the crack width, and to a lesser extent on the depth profile of the crack. Also, the distribution of the density of the leakage field is measured over the centre of the crack and correspondingly changes more by varying of dj and dj rather than of d, dj, dj and d . 

It is suggested though that even more precise sizing of cracks with complex cross-sections and unknown shapes could be achieved using the distribution of the leakage magnetic field along two lines positioned above the surface of the sample and parallel to the direction of the applied field at the same distance from the centre of the crack and from its closer end. 

Fig. 1. Schematic of magnetic flux leakage tests where H,B represents an external appHed magnetic field. See text, (a) Saturated material having no crack,...

Tlie indi ddual cells are assembled into batteries after a leakage test to check for faulty welding joints in steel containers or cracks and improper seals in the plastic encased cells. Cells that are to be delivered without electroltye are emptied after the fomiation cycles. Tlie steel-cased cells hav e to be separated by mechanical means to prevent intercell shorts and are often assembled into wooden crates. Tlie cells in plastic cases can be cemented together or strapped with tape. 

Tubes were almost plugged with deposits (Fig. 4.30A and B). The deposits contained almost 40% sulfur by weight. Hydrocarbon in-leakage had occurred through small cracks that originated on internal surfaces beneath deposits. 

Cracking imposes an additional penalty in a vacuum unit in that it forms gas which cannot be condensed at the low pressures employed. This gas must be vented by compressing it to atmospheric pressure. This is accomplished by means of steam jet ejectors. Ideally, it would be possible to operate a vacuum pipe still without ejectors, with the overhead vapors composed only of steam. In practice, however, leakage of air into the system and the minor cracking which occurs make it necessary to provide a means of removing non-condensibles from the system. In addition to the distillation of atmospheric residuum, the lube vacuum pipe still is also used for rerunning of off specification lube distillates. 

The VPS overhead consists of steam, inerts, condensable and non-condensable hydrocarbons. The condensables result from low boiling material present in the reduced crude feed and from entrainment of liquid from the VPS top tray. The noncondensables result from cracking at the high temperatures employed in the VPS. Inerts result from leakage of air into the evacuated system. Steam and condensable hydrocarbons are condensed using an overhead water-cooled condenser. The distillate drum serves to separate inerts and non-condensables from condensate, as well as liquid hydrocarbons from water. Vacuum is maintained in the VPS using steam jet ejectors. 

Limited information is available on values of for industrial buildings. The effective leakage area, CjA, can be determined by means of a building pressurization or depressurization test.-7 A range of values of for cracks formed around closed windows are given in Table 7.33. These should be used with a value of P = 0.67. 

Door air leakage The leakage due to pressure differences through the crack around a door. 

INCIPIENT a. Wall Thinning b. Embrittlement c. Cracked or Flawed d. Internal Leakage ... 

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