Fixed valve

Figure 8-70. Nutter V-Grid fixed valve for trays. Used by permission, Nutter Engineering, Harsco Corp., Bui. N-2.

For a discussion of this important performance control topic, refer to Cylinder Unloading, later in this chapter and Figure 12-27. A reasonable average range is 7-22% with fixed valve pockets. ... 

Fixed-roof tanks, 24 288-289 Fixed surface aerators, 26 159, 160 Fixed valve plates, 3 763-764 Fixing agents color film, 19 261 photographic, 19 213 Fixolide, 24 494 Flake... 

Fixed valve trays (Fig. 14-18i>) have the perforations covered by a fixed cover, often a section of the tray floor pushed up. Their performance is similar to that of sieve trays. 

Fixed valve and sieve trays prevail when fouling or corrosion is expected, or if turndown is unimportant. Valve trays prevail when high turndown is required. The energy saved, even during short turndown periods, usually justifies the small additional cost of the moving valve trays. 

Sieve trays Fixed valve tray Moving valve tray... 

Similar considerations apply to fixed valves. Small fixed valves have a slight capacity advantage, but are far more prone to plugging than larger fixed valves. 

Fractional Hole Area Typical sieve and fixed valve tray hole areas are 8 to 12 percent of the bubbling areas. Smaller fractional hole... 

For Sulze s fixed valve trays, Summers and van Sinderen (Distillation 2001 Topical Conference Proceedings, AIChE Spring National Meeting, p. 444, Houston, April 22-26, 2001) provided the following equation for K ... 

Low dry tray pressure drop. On sieve and fixed valve trays, this means high (>11 percent) fractional hole area. On moving valve trays, this means venturi valves (smooth orifices) or long-legged valves (>15 percent slot area). On all trays, the channeling tendency and severity escalate rapidly as the dry pressure drop diminishes (e.g., as fractional hole area increases). 

Not all trays are fouling-resistant. Floats on moving valve trays tend to stick to deposits on the tray deck. Fouling-resistant trays have large sieve holes or large fixed valves, and these should be used when plugging and fouling are the primary considerations. 

Figure 8-71 A. Nutter high performance fixed valve tray with...

The mass-transfer devices may be sieves (holes), fixed valves, moveable valves, or bubble caps. Fig. 2 shows a selection of mass-transfer devices. The purpose of the device is intimate mixing of the vapor and liquid on the tray deck. An ideal device has high capacity, high flexibility, low leakage, low pressure drop, and low cost. 

FIGURE 12.37 Views of a rectangular, movable valve and a rectangular fixed valve (the V-grid). (Courtesy of Sulzer Chemtech USA, Inc.)... 

Figure 10.8 Active control experiments to realize full tube fills in the Stanford PDE (a) indicates fuel filling duration, and (b) indicates cycle impulse for the cases of fixed valve opening duration and variable opening for active control 1 — fixed duration and 2 — active control.

K = constant which depends on the valve size p = specific gravity of the flowing liquid (relative to water) fix) = valve flow characteristic curve The valve flow characteristic curve, fix), depends on the geometrical shape of the plug s surface. Figure 13.10 shows the most common types of plugs while Figure 13.11 shows the flow capacity characteristics for the various valves. 

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