Bypassing design rates

The PCU shaft speed response appears in Figures 18 and 19. There is an initial overshoot in the first second as the controller attempts to maintain 60 Hz. The overshoot dies out within three seconds and the speed returns to the set point value. The permissible magnitude and time rate of change of the overshoot is governed by mechanical design considerations. The constants in the PI speed controller can be modified as needed to reduce overshoot. Bypass flow rate shown in Figure 20 peaks at almost half of the full power PCU flow rate. 

For a properly designed and operated cyclone, the sharpness iadex is constant, typically 0.6. The cut size and apparent bypass are a function of the cyclone geometry, the volumetric feed rate, the material relative density, the feed soflds concentration, and the slurry rheology. The relationship for a standard cyclone geometry, where if is the cylinder diameter ia cm and inlet area = 0.05 vortex finder diameter = 0.35 ... 

For many years the usual procedure in plant design was to identify the hazards, by one of the systematic techniques described later or by waiting until an accident occurred, and then add on protec tive equipment to control future accidents or protect people from their consequences. This protective equipment is often complex and expensive and requires regular testing and maintenance. It often interferes with the smooth operation of the plant and is sometimes bypassed. Gradually the industry came to resize that, whenever possible, one should design user-friendly plants which can withstand human error and equipment failure without serious effects on safety (and output and emciency). When we handle flammable, explosive, toxic, or corrosive materials we can tolerate only very low failure rates, of people and equipment—rates which it may be impossible or impracticable to achieve consistently for long periods of time. 

Temperature ehanges for the flue gas to the expander produee the effeets shown in Figure 4-63. The expander inlet temperature at design is 1,200°F. As the expander inlet temperature rises, the expander horsepower eurve moves to the left and upward while the ehange in the blower eurve is insignifieant. The results are that the lower horsepower balanee point moves to the left and down, the peak of the expander eurve moves to the left and up, the peak generator load inereases to G, and the expander bypass valve opens at a lower feed rate. 

The limit stops or bypasses should be sized to pass at least 25% of the design flow rate to that pass. Likewise, the low flow alarm and fuel cut-out should be set to operate when the flow falls to 25% of the design flow rate. 

Schematic representation of hot hydrogen burning via the CNO tricycle. Branching is shown for four different temperatures designated using the symbol T9, which means 10 9 K. Widths of arrows are proportional to reaction rate. At temperatures >10 8 K, the proton reaction rates on 13C, 150,17F, and 1SF begin to compete effectively with the (,p+ v) reactions. Isotopes such as 13C and 1SN are bypassed and a different equilibrium is established. If this equilibrium is quenched, such as in a nova explosion, the unstable nuclei p-decay to their respective stable daughters, resulting in low 12C/13C and 14N/15N, and 12C/160 can be greater than one, very different from the outcome of normal CNO burning. After Champaign and Wiescher (1992).

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