Tray layout spacing

Summary. Following the flooding checks, the column diameter remains at 6 ft. The tray layout remains- as specified at the beginning of this section. However, the tray spacing in the top section is extended from 18 to 21 in, so that the tower has 24-in tray spacing in the bottom section and 21-in tray spacing in the top section. 

The layout for this trial is the same for the second trial except for the above changes in weir heights and clearances. Also, the tray spacing in the top section changed from 13 to 21 in. Throughout this trial, vapor and liquid loads and physical properties are taken from Table 6.10. Tray layout parameters are shown in Table 6.11. Some variables that remain unchanged from the previous trial are... 

The number of valve caps that can be fitted on a tray is at best an estimate unless a detailed tray layout is prepared. However, a standard has evolved for low- and moderate-pressure operations a 3 x 2 y2 in pattern that is the tightest arrangement available, accommodating about 14caps/ft2 (150 caps/m2). The active area does not take into account liquid-distribution areas at the inlet and outlet, nor edge losses due to support rings, nor unavailable space over tray-support beams. In smaller columns, it is possible that as much as 25 percent of the active tray area may not be available for functioning valves. For this column, which operates at low pressure, select the standard 3 x 2 /2 in pitch. 

The hardware design proceeds In two phases primary (basic) and secondary (detailed layout). The primary phase sets column diameter, type of tray, and split of tray area Into bubbling and downcomer areas. This phase also provides a preliminary (and usually close) estimate of tray spacing, number of passes, and other features of tray and downcomer layout such as weir height, fractional hole area, hole diameter, and clearance under the downcomer. These estimates are later firmed up in the secondary phase. 

Layout. First, determine downcomer areas. The calculation in Sec. 6.5.5 shows that the area for the top section downcomers is about right On the other hand, the bottom section downcomers appear somewhat oversized. Table 6.5 suggests that for the depropanizer (high foaming tendency, 18- and 24-in tray spacing) up to 110 gpm/ft2 is an appropriate velocity. Resize the downcomer for 110 gpm/ft2. 

The preparation area should provide sufficient counter space for preparation of samples and layout of sample trays. The area should provide refrigerated and frozen storage, electrical ranges and microwave ovens for heating, and sinks and dishwashers for cleaning purposes. Installation of distilled or filtered water should be considered for panelists rinsing water and preparation of solutions if tap water imparts a flavor and odor. Ventilation hoods with exhaust fans should be installed to remove odors in order to prevent the odors from spreading to the booth area. 

All necessary materials should then be placed in the cabinets, segregating clean items, cultures, and receptacles for contaminated items. The worker should organize the materials so that contaminated materials do not need to pass over clean items (remember, the air flow direction is downward). A good layout of materials would place cultures, clean pipets, flasks, etc. toward the front on either side of the work area, and a discard tray for culture plates and pipets towards the rear of the work space, as shown in Figure 9.9. Avoid placing items within ten centimeters of the cabinet front. The cabinet must not be overloaded with materials. Overloading will disrupt the air stream and interfere with proper cabinet performance. 

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