High pressure water stress

PWRs operate differendy from BWRs. In PWRs, no boiling takes place in the primary heat-transfer loop. Instead, only heating of highly pressurized water occurs. In a separate heat-exchanger vessel, heat is transferred from the pressurized water circuit to a secondary water circuit that operates at a lower pressure and therefore enables boiling. Because of thermal transfer limitations, ultimate steam conditions in PWR power plants ate similar to those in BWR plants. For this reason, materials used in nuclear plant steam turbines and piping must be more resistant to erosion and thermal stresses than those used in conventional units. 

Equipment may get washed with a steam jenny and allowed to air dry on plastic in a more remote area. We need to keep in mind that steam cleaners have the potential to cause substantial physical harm. The combination of high-pressure water and high temperatures can be dangerous. Wlien this is coupled with a worker standing on visquine or plastic, it becomes a slip, trip, and fall situation. Situations compounded with respiratory and whole-body protection, such as saranex or rubber suits and gloves, add in the potential for poor vision, heat stress, and the lack of physical dexterity. Keep these issues in mind prior to steam cleaner activity. 

High-pressure water can adso be used to water-jet cut mamy plaistic materiads. A fine jet of water (either pladn or with abrasive added) is directed at the paut at pressures of 60,000 Ib/in fi-om a fine nozzle. Automated robotic equipment is avadlable to water-jet cut intricate patterns. This method is very attractive for mamy hard to cut materials such as aramid fiber-reinforced composites. The water jet cuts most materials quickly without a burr and does not introduce stresses in the material. 

Zhang Wei, Huang Licai. Design of tunnel with high pressure water based on coupled analysis of seepage field and stress field [J]. Journal of Water Resources and Architectural En eering, 2007 5(2) 41-44. 

Laminates ensure reliable protection in long, complex procedures where there is a high incidence of liquid and high-pressure mechanical stress related activity. The pore size is customised so that bacteria, viruses and liquids cannot penetrate the membrane, yet the passage of water-vapour molecules is possible. The laminate must be liquid-tight at high pressures and display greater liquid resistance than other liquid-repeUent materials. 

Austenitic stainless steels will exhibit stress-corrosion cracking in hot aqueous chloride solutions, in acid chloride containing solutions at room temperature, in hot caustic solutions and in high-temperature high-pressure oxygenated water. 

NOTE Water hammer is caused by sudden interruptions in flow as when steam meets draining condensate. The steam produces instantaneous surges of pressurized water that hits valves, elbows, and tees at high velocity. This produces a hammering sound and leads to metal stress and possible failure. 

A more serious threat to the materials compatibility of CNG fuel systems is condensed water vapor. Water can cause steel and cast iron to rust and aluminum to corrode. Any corrosion of components that must withstand high pressures is a concern, since corrosion stress cracking can occur which can result in failure of the component with disastrous results. The presence of water greatly accelerates the corrosion properties of the hydrogen sulfide that might be found in the natural gas. For these reasons it has been recommended that the way to control corrosion in CNG systems is to remove sufficient water vapor to prevent it from condensing in the system under static conditions [3.13]. Natural gas dryers have been developed to help reach this goal. 

To appreciate the osmoregulatory problems faced by bacteria and, therefore, the particular strategies they use when faced with water stress, it is important to realize that, unlike most eukaryotic cells, bacterial cells typically must maintain a high positive turgor pressure. 

Figure 9.7. BF micrographs showing the strrun associated with high-pressure clusters of molecular water in as-grown wet synthetic quartz (crystal W2). (a) Region with a water content corresponding to 2(X)H/10 Si. (b) Region with l,600H/10 Si. No strain is associated with the arrowed clusters because they intersect the foil surface the water escapes, and the stress is relaxed. The strmn field of the circled cluster is characteristic of a lens-shaped inclusion whose plane is normal to the foil surface. (From McLaren et al. 1983.)...

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