Throw over weir

Liquid throw over weir...60% downflow width, maximum... 

Uncorrected A /row caps = approx. 7. Throw over weir ... 

To ensure unobstructed vapor passage above the froth and liquid in the downcomer from a tray, the liquid mixture must not throw against the shell wall. The distance of throw over the weir is given by Reference 5. See Figure 8-63. 

Criteria for determining downcomer area are described below. The author recommends that the downcomer area be set large enough to satisfy all of these criteria except for liquid throw over the weir. 

In early designs, downcomer width was set so that the liquid throw over the weir does not reach the column wall (48, 73, 88, 172, 257, 371). The purpose of this practice was to provide a pathway for vapor disengaged in the downcomer to the tray above. Design criteria for adequate liquid throw are presented in the literature (48, 73, 88, 172, 257,371). Since then, it has been demonstrated (396-398) that even at very low liquid flow rates and wide downcomers, the liquid throw hits the column wall, and that the above criteria were ineffective. These criteria were based on clear liquid, while the downcomer liquid is aerated, and therefore travels longer horizontal distances. 

Thomas et al. (396-398) observed that even when the liquid velocity exceeded the design criterion, the downcomer inlet was not completely closed. They pointed out that it may even be advantageous for the aerated liquid to hit the column wall, as it assists in breaking up the froth, thus reducing the quantity of vapor entering the downcomer. On this basis, liquid throw over the weir is not considered a limiting factor (246, 371, 396-398), and is normally omitted from downcomer sizing calculations. 

In early designs, criteria for including emtjjump baffles were based on the liquid throw over the weir (48, 73, 88, 371). More recent publi-... 

Liquid throw The horizontal distance traveled by the liquid after flowing over a weir. 

The liquid throw is the horizontal distance travelled by the liquid stream flowing over the downcomer weir. It is only an important consideration in the design of multiple-pass plates. Bolles (1963) gives a method for estimating the liquid throw. 

Liquid throw. Liquid throw (or jump) over the weir is the horizontal distance the liquid travels from the outlet weir before reaching the main body of liquid in the downcomer (Fig. 6.15). 

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