Surge effects

Flow instabilities or even pipeline blockage during start-up procedures due to surge effects caused by the initial high pressure drop across the blow tank (and hence high instantaneous flow rate of material),... 

Pipeline blockage during shutdown procedures due to surge effects caused by the sudden venting of high pressure air down the pipeline (and hence, acceleration of product towards the end of the pipeline). 

Currents ean be described over a given time-scale by a time-mean magnitude, direction, and spatial and turbulent variability. Tidal currents, like astronomical tidal levels are predictable but can be particularly influenced by less predictable components such as wind, river discharge and surge effects. When wind and wave influences are important in current generation, it is rare for the resulting, albeit less predictable, currents to be a governing construction consideration when compared with the direct wind and wave effects. 

These pipe walls are adequate for the rated working pressure plus a surge allowance of 100 Ihf/in . For the effect of laying conditions and depth of hiiry, see ANSI A21.51. 

Fibrous or particulate filters are not important anymore because membrane filters are relatively compac t and perform veiy well. For filtration by straining, there is an intermediate air velocity at which filtration efficiency is a minimum because different collec tion mechanisms predominate at different ranges of velocity. At low velocities, diffusional and elec trostatic forces on the particle are important, and increased velocity shortens the time for them to operate. At high velocities, inertial forces that increase with air velocity come into play below a certain air velocity, their effect on collection is zero. Surges or brief power failures could change velocity and collection efficiency. 

Install surge pot between feed vessel and reactor to minimize effects of inadvertent mixing... 

These are mainly due to atmospheric disturbances as noted below. The effect of such surges is totally different from that of switching surges, and the amplitude is independent of the system voltage. 

Figure 17.5 Oscillograms showing the effectiveness of a surge arrester on a 6.6 kV motor...

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