Bypassing for

Determining which accident sequences lead to which states requires a thorough knowledge of plant and process operations, and previous safety analyses of the plant such as, for nuclear plants, in Chapter 15 of their FSAR. These states do not form a continuum but cluster about specific situations, each with characteristic releases. The maximum number of damage states for a two-branch event trees is 2 where S is the number of systems along the top of the event tree. For example, if there are 10 systems there are 2 = 1,024 end-states. This is true for an "unpruned" event tree, but. in reality, simpler trees result from nodes being bypassed for physical reasons. An additional simplification results... 

Answer Use the plant s PSA to determine the risk of accidents that include containment failure from overpressurization. Then make a preliminary design of a vented containment that has sufficiently low impedance to the gas at the pressure predicted for the most severe accident sequences such that the containment is not damaged. This containment bypass will include iodine and HEPA filters as well as scrubbers and a discharge through a stack. Estimate the dose that the population would get using this bypass for comparison with the PSA result for ruptured containment sequences. 

As long as pressure, level, and temperature control devices are operating correctly, the safety system is not needed. If the control system malfunctions, then pressure, level, and temperature safety switches sense the problem so the inflow can be shut off. If the control system fails and the safety switches don t work, then relief valves are needed to protect against overpressure. Relief valves are essential because safety switches do fail or can be bypassed for operational reasons. Also, even when safety switches operate correctly, shutdown valves take time to operate, and there may be pressure stored in upstream vessels that can overpressure downstream equipment while the system is shutting down. Relief valves are an essential element in the facility safety system. 

Nagata S, Fujii K, Matsushima T, Fukui M, Sadoshima S, Kuwabara Y, Abe H. Evaluation of EC-IC bypass for patients with atherosclerotic occlusive cerebrovascular disease clinical and positron emission tomographic studies. Neurol Res 1991 13 209-216. 

Unavoidable loss of gas is compensated via a feed valve for supplying virgin nitrogen into the circulation pipe. The exhaust gas of the process has to be bypassed for purification. After the separation of dust by a filter, the gas is heated to 400 °C for the catalytic combustion of the side products. The gas is then cooled down, and the excess oxygen is catalytically converted to water by using hydrogen. For economic reasons, the gas flow will recover the heat via a heat exchanger and then be cooled down by a gas cooler. 

Very little data exist on the separation efficiency of multilayer diffusion and capillary condensation. Asaeda and Du (1986) used a thin modified alumina membrane to separate alcohol/water gaseous mixtures at high relative pressures (near 1). The azeotropic point could be bypassed for water/ethanol and water/isopropanol mixture by employing eapillary condensation as a separation mechanism at a temperature of 70°C. By deereasing the pore size to the microporous range (pore diameter < 2 nm by plugging the pores with hydroxides), the separation faetors were inereased to above 60 (Asaeda and... 

In 1974, 28 people died in an explosion resulting from a large release of cyclohexane in Flixborough, U.K. The source of the hydrocarbon release was a failed expansion joint in a section of 20-inch (508-mm) diameter pipe. Investigation revealed the pipe had been designed with little technical input as a temporary bypass for a reactor that had been removed after it cracked. 

As research has progressed in this area, many systems have been shown to follow a similar behaviour. Such phenomena are important in the production of enzymes and metabolites. In industrial applications, these very important control mechanisms usually have to be bypassed for the reliable generation of high concentrations of enzymes. Good examples may be seen in carbohydrase production systems,... 

An additional general method to reduce bypass is through vacuum deaeration. Miller9 performed experiments on a low-density active blend with and without vacuum deaeration, while holding all other parameters constant, and quantified the bypass for each trial. With the vacuum deaeration engaged, the bypass rate was 2% as compared to the control rate of over 20%. He also observed that the powder feed was uneven and the compact quality was not uniform. Most units are equipped with this capability and it should be considered to minimize bypass for low-dose products. However, vacuum deaeration can cause potency loss, unless the collected material is recirculated to the feed system. 

Figure 20.11 is a sketch of a once-through Claus process using a hot gas bypass for reheat. Sufficient air is used to bum one-third of the H2S and all hydrocarbons. Steam... 

In principle technical development and standardization go side by side, the latter, however, shows a certain time delay of months or even some years. So it is quite common that regulations (directives drawn up by national or international authorities, standardization) open a bypass for technical solutions which do not comply (in full or in part) with established standards. 

Bypassing for 470 K Economizer Output Gas While Input Gas Temperature is Varying... 

Also, the bypass flue and control valve should be large enough to give sufficient bypassing for the smallest anticipated cooling duty. 

PCV - 34 Malfunction Flow releasee to flare, including recycle froai compressors 1natall check valve downstreaai of ESV to prevent back flow of gas froai the compressors tilth block valve and one-inch bypass for starting end purging NOTE Check valve and one inch bypass Installed refer to revised PtIO Rev. 0 Recycle on compressor will open - system will not shut down... 

Short bowel Intestinal resection (e.g. for Crohn s disease, volvulus, intussusception or infarction) Jejunoileal bypass for obesity... 

A ruptured middle cerebral artery aneurysm originating from the site of anastomosis 20 years after extracranial-intracranial bypass for moyamoya disease case report. Surgical Neurology 64 261-265... 

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