Wall stiffeners

Bracing of wall stiffeners to allow for possible jet force impingement on the vessel wall, and for intermittent buffeting and vibration if two-phase slug flow can occur. 

The peripheral stiffening zone (tray ring) is generally 25 to 50 mm (1 to 2 in) wide and occupies 2 to 5 percent of the cross section, the fraction decreasing with increase in plate diameter. Peripheiy waste (Fig. 14-28) occurs primarily with bubble-cap trays and results from the inabihty to fit the cap layout to the circular form of the plate. Valves and perforations can be located close to the wall and little dead area results. Typical values of the fraction of the total cross-sectional area available for vapor dispersion and contact with the liquid for cross-flow plates with a chord weir equal to 75 percent of the column diameter are given in Table 14-6. 

Abrupt changes of section cause poor flow and differential shrinkage, giving sink marks (Fig. 28.11 - you can find them on the surface of many small polymer parts), distortion, and internal stress which can lead to cracks or voids. The way out is to design in the way illustrated in Fig. 28.12. Ribs, which are often needed to stiffen polymer parts, should have a thickness of no more than two-thirds of the wall thickness, and a height no more than three times the wall thickness. Corners are profiled to give a uniform section round the corner. 

Thin to large wall Designing around TP problems is the joint responsibility of the product and mold designers. For example, one way to handle the problem of thin to large area walls is by the inclusion of long ribs into the product in the direction of plastic flow. These ribs are not a functional requirement of the product but they act as auxiliary runners attached to the product to facilitate plastic flow in difficult to fill areas. In some instances the ribs may be used as a surface decoration like a corrugation or they may be on the concealed side of the product where they are stiffeners. 

To determine wall thickness and stiffening requirements for straight pipe under external pressure, the procedure outlined in ASME BPV Code Section VIII, Division 1, UG-28 through UG-30 shall be followed, using as the design length, L, the running centerline... 

External pressure stresses. Stresses due to external pressure shall be considered safe when the wall thickness of the piping component, and its means of stiffening meet the requirements of the pressure design of components defined by the ASME B31.3 code. 

Cardiac patients need to be monitored closely when receiving these drugs because of their bradycardiac effects (which can lead to ectopic arrhythmias), and hypotensive effects resulting from prolonged vasodilation. In addition, the drugs stiffen the chest wall musculature, an effect reversed by naloxone. 

Plants use osmotic pressure to achieve mechanical rigidity. The very high solute concentration in the plant cell vacuole draws water into the cell (Fig. 2-13). The resulting osmotic pressure against the cell wall (turgor pressure) stiffens the cell, the tissue, and the plant body. When the lettuce in your salad wilts, it is because loss of water has reduced turgor pressure. Sudden alterations in turgor pressure produce the movement of plant... 

Supporting beams are used to stiffen the trays, and the trays must be fastened securely to prevent movement caused by gas surges. To allow for thermal expansion and to facilitate installation, slotted bolt holes should be provided in the supporting rings, and there should be adequate clearance between the tray and shell wall. 

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