Erosion locations

In rheumatoid arthritis, chronic synovitis leads to hypertrophy and hyperplasia of the synovium (pannus), progressive thinning of the articular cartilage and exposure of the subchondral bone. In early disease, when the cartilage still retains a certain thickness, the pannus typically causes marginal bone erosions, located at the periphery of the joint. 

Other examples of government and military applications of laser-based profilometry include the evaluation of rocket thruster nozzles to locate and measure flame erosion remote inspection of hypervelocity test track and the measurement of sludge deposits on tube internal surfaces. 

Basic to establishing whether power recovery is even feasible, let alone economical, are considerations of the flowing-fluid capacity available, the differential pressure available for the power recovery, and corrosive or erosive properties of the fluid stream. A further important consideration in feasibihty and economics is the probable physical location, with respect to each other, of fluid source, power-production point, and final fluid destination. In general, the tendency has been to locate the power-recoveiy driver and its driven unit where dictated by the driven-unit requirement and pipe the power-recoveiy fluid to and away from the driver. While early installations were in noncorrosive, nonerosive services such as rich-hydrocarbon absorption oil, the trend has been to put units into mildly severe seiwices such as amine plants, hot-carbonate units, and hydrocracker letdown. 

Favored locations for erosion-corrosion are areas exposed to high-flow velocities or turbulence. Tees, bends, elbows (Fig. 11.5), pumps, valves (Fig. 11.6), and inlet and outlet tube ends of heat exchangers (Fig. 11.7) can be affected. Turbulence may be created downstream of crevices, ledges (Fig. 11.8), abrupt cross-section changes, deposits, corrosion products, and other obstructions that change laminar flow to turbulent flow. 

Figures 11.11 through 11.13 illustrate the type of metal loss responsible for a dozen tube leaks over a 3-month period. Note the highly localized character of the metal loss, as well as the unusual shapes and random orientations of the eroded sites. The sites were located at the inlet end and resulted from the lodgment of debris at the mouth of the tube. Highly localized turbulence created by this debris caused the erosion.

The lift pipe design was tapered to a larger diameter at the top. This minimized the effects of erosion and catalyst attrition, and also prevented the instantaneous total collapse of circulations when the saltation concentration, or velocity, of solids is experienced (i.e. the slump veloeity-that velocity helow which particles drop out of the flowing gas stream). In a typical operation, 2 % to 4 % eoke can he deposited on the catalyst in the reactor and burned in the regenerator. Catalyst circulation is generally not sufficient to remove all the heat of eombustion. This facilitated the need for steam or pressurized water coils to be located in the regeneration zone to remove exeess heat. 

Used to restrict reversal of flow, check valves should not be considered as positive shut-off valves when flow is reversed, since the seating element is always in the flow stream and subject to erosion (Figures 15-9 to 15-13). A section of a line should not be considered isolated if the only batrier to flow is a check valve. On the other hand, because they do restrict backflow to very low levels, check valves installed in appropriate locations can protect equipment and minimize damage in case of a leak in the upstream line. Some of the advantages and disadvantages of the various check valve configurations are as follows ... 

Let us now consider a chemical reaction whose initial and final states are different. Then the potential energy surface will not be symmetrical. This geological analogy will be helpful Suppose the valleys are formed by erosion. Then the valley that has eroded faster (or for a longer time) will be both deeper and longer than the less eroded valley, with the necessary consequence that the saddle between the two valleys is shifted toward the shallower valley. Figure 5-4 shows such a surface on which the reactant valley is longer and deeper than the product valley clearly the transition state is located closer to the final state than to the initial state as a result of this disparity in stabilities. 

Human respiratory functions may be impaired. Elevated levels of metals have been observed in some foods and drinking water in some locations. Masonry works, stone structures and heritage sculptures are subject to accelerated rates of erosion. 

The rationale for the development and application of the matrix was established 20 to 25 years ago and is discussed elsewhere (14,17). The location and density of land erosion and deposition features were identified through intensive analysis of stereoscopically paired color infra-red images at a scale of 1 130,000. The observations made from the color infra-red analysis were systematically noted and verified through field observation and low altitude imagery (14). 

The explanted devices were also examined by scanning electron microscopy and the results shown in Fig. 21 (18). The pictures clearly show a progressive diminution of a central uneroded zone and the development of voids around the periphery of the rod-shaped device. The presence of voids suggest that once erosion starts, generation of hydrophilic degradation products at that location accelerates further polymer hydrolysis. 

Erosion of liver abscesses can result in peritonitis. Liver abscesses that are located in the right lobe can spread to the lungs and pleura. Pericardial infection, although rare, may be associated with extension of the amebic abscesses from the liver. 

Tube erosion has been observed in both atmospheric and pressurized bed combustors. The scaling analysis presented earlier can be used to construct an accurate hydrodynamic simulation of the commercial bed. This can be used to qualitatively investigate factors related to tube wear such as the location of highest wear around the circumference of an individual tube and the location within the bed of the tube experiencing the highest wear. Quantitative wear rates cannot be obtained from model tests... 

Process locations containing large volumes or high pressure hydrocarbon gases which might be susceptible to extreme effects of erosion or corrosion from the process activity. 

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