Design barrier

Since competent manufacturers can accurately predict the susceptibility for the formation of the corrosive scale Ni3S2 for any gas analysis, it is possible to implement preventive measures. The preventive measure that is presently being used by Elliott and others is the use of a steam barrier. The principle of the steam barrier design is to inject steam into the inlet and exhaust chambers of the disc/blade area. The injection of steam into both these chambers creates a barrier of... 

Subsurface drains are essentially permeable barriers designed to intercept the groundwater flow. The water must be collected at a low point and pumped or drained by gravity to the treatment system (Figure 8). Subsurface drains can also be used to isolate a waste disposal area by intercepting the flow of uncontaminated groundwater before it enters into a contaminated site. 

Interstate Technology and Regulatory Council (ITRC), Regulatory Guidance for Permeable Reactive Barriers Designed to Remediate Chlorinated Solvents, December 1999. 

Garside, Robin, "Modular Zener Barrier Design Simplifies IS Installations", page 45, Control and Instrumentation, Vol II, No. 1, Jan 1979... 

All three wedge barrier designs have a high crash rating, thereby allowing them to be employed for higher-security applications. ... 

At the startup of the line, the extruder was operated at 91 rpm to produce the required rate of 148 kg/h for a specific rate of 1.63 kg/(h-rpm). The temperature of the extrudate was measured through the transfer line wall at 232 °C. Due to process safety constraints the extrudate temperature could not be measured using a handheld temperature sensor. The extrusion rate was required in order to maintain the downstream take-away equipment at its maximum rate. At first the extruder appeared to be operating well except that the specific rate was lower than predicted. That is, the screw was rotated at an rpm that was higher than expected to produce the 148 kg/h. At 91 rpm, the rotational flow rate was calculated at 228 kg/h the specific rotational flow rate was calculated at 2.51 kg/(h-rpm). Thus, the line was operating at only 65% of the rotational flow rate. A barrier design... 

On an industrial scale, operations are commonly carried out by remote control (Ref 10) and the considerations of quantity-distance (Ref 48) and barrier design (Refs 13 75) apply. On a lab scale, remote weighing, mixing and pressing are usually not practical, and the protection of personnel must take the form of shielding for eyes, face and hands, as well as thru protection for the hair and the choice of suitable clothing. 

Because reaction rates vary widely among contaminants, Fe barrier design should be dependent on the least reactive contaminant. Some... 

Tratnyek, PG. T.L. Johnson, M.M. Scherer, and G.R. Eykholt. 1997. Remediating groundwater with zero-valent metals Kinetic considerations in barrier design. Ground Water Monit. Rem. 108-114. 

Most of the technologies available for mitigating the nation s scrap tire problem are limited by both economic and noneconomic barriers, and it is often difficult to separate the two. For example, the use of retreaded or used automobile tires is limited by competitive new tire prices, an economic barrier, as well as consumer concerns about safety and reliability, a noneconomic barrier. Designing tires to last 100,000 miles or more would cost considerably more and also would likely result in rougher rides and more tire noise. 

Tratnyek PG, Johnson TL, Scherer MM, Eykholt GR. Remediating ground-water with zero-valent metals kinetic considerations in barrier design. Ground Water Monit Remediat 1997 17 108-114. 

Thermal barrier designed to prevent excessive heat transfer from hot combustion products to case of rocket. 

Experimentally found energy of activation SN2 of replacement of bromine in methylbromid and benzylbromid by anion (II) and aniones (V a), (V b) (tables 3, 6) according to equation Arrenius correlate with sizes of the power barriers designed by a method ab-initio (rice 1). 

Conventional control of termites is heavily reliant upon prophylactic application of liquid insecticides to form a soil barrier around and beneath a structure to termite entry. These barriers, designed to repel or kill termites, degrade over time and must be reapplied every 5-10 years. A barrier termiticide application requires significant quantities of active ingredient, 5-10 kg, carried in 300 to 600 liters of water. Conventional products used as soil termiticides include organophosphates such as chlorpyrifos and isofenphos. 

Further discussion of nuclear reactor control problems resulting from water leakage is beyond the scope of the present paper, and the discussion presented hereafter is on the effects of the chemical reaction between sodium and water. As a corollary of this discussion, the necessity for the use of a double-barrier heat exchanger in systems where nuclear control problems are absent has been examined. The desirability of eliminating the double-barrier design where feasible is obvious. The double-barrier results in a more complex design with associated fabrication and operational problems, requires additional heat transfer area due to the increased thermal resistance of the double barrier, and requires external equipment to handle the third-fluid system. All these factors increase the size and cost of the heat exchanger. 

The second unit in which a failure resulted in the mixing of water and sodium occurred in a superheater unit which was part of a steam generator with a per hour capacity of about 10 X 10 B.t.u. being tested at the MSA (8). This superheater, shown in Figure 6, was a tube and shell heat exchanger with sodium on the shell side and steam on the tube side. The unit was of double-barrier design with mercury as the third fluid. The third fluid was normally maintained at a pressure intermediate between the sodium and steam system pressures. 

Additional consideration should be made when the pin and shoulder are made of one material, while the tool shank (portion of tool within the spindle) is a different material. One way to mitigate this situation is with a thermal barrier designed to prevent heat removal from the tool into the shank. An example of this is used with PCBN tools where a thermal barrier prevents heat from moving into the tungsten carbide shank (Ref 5). The CTE differences between the tool and workpiece are not found to have a significant influence on friction stirring. 

In addition, immersion and removal speeds play a definite role in LB depositions because they disturb equilibrium of charges at the electrical double layer. When the solid is immersed, the double layer begins to form and ions must diffuse toward and away from the solid surface before equilibrium is reached. When the solid is removed, the double layer is partially wiped out by the flow but metal cations are retained on the film deposited on the solid substrate. On the other hand, during film deposition, the mechanical barriers designed to keep the surface pressure constant move the film on the air-water interface and disturb the double layers under the film. At this point, we do not have a quantitative way to estimate the disturbance to the double layer caused by the movement of the solid substrate, but we can introduce the following assumptions ... 

The failure of non-structural elements such as block walls, stairs and scaffolding could have consequences for SSCs. External hazards (such as earthquakes, high winds, explosions or impacts of aircraft) could be the cause of such a failure and they are usually evaluated on the basis of Ref [5]. However, there may be situations in which the failure of non-structural elements may be caused by internal initiating events such as operator error or accidents during maintenance. The consequences for SSCs should be evaluated in these cases. Care should be taken either to avoid such failures or to minimize the potential damage to SSCs by means of proper location and adequate barrier design. 

Fig. 11.7. Barrier design involving a leachate collection system, a natural clayey deposit and downward advective-diffiisive transport (Rowe et al. 1995)...

Multiple barriers designed into the power plant provide containment of radioactive products at three fundamental levels ... 

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