Support beam tray column

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. 

In large-diameter (> 10 to 12 ft) columns, one or more mqjor support beams (Fig. 7.1) are required, and these also support the minor support beams. In smaller-diameter (< 10 to 12 ft) columns, major support beams are often omitted, and trays are entirely supported by the support rings and minor support beams. In some cases, tie-rods are used for minimizing tray deflection. 

Support beams should be located parallel to the liquid flow on the tray. This is recommended in order to minimize vapor crossflow (86, 88, 138). In large columns (> 10 to 12 ft), the major support beams... 

Support beams must be installed level, or tray levelness may be difficult to achieve, especially in large columns. Support beams are often equipped with levelling screws (288) to permit on-site levelling. A less satisfactory alternative is using slotted holes on the joint of a major support beam to its shell support brackets. Slotted holes, however, are often used on the joints of minor beams to the major support beam to allow levelling. 

Rgure 8.6 Maldistribution caused by I-beam support, (o) At column base (6) at a chimney tray. (Part a based on Process Design for Reliable Operation, second edition, by Norman P. Lieberman. Copyright 1988 (May) by Gulf Publishing Company, Houston, Texas. Used with permission. All rights reserved. Part b courtesy of D. W. Reay (BP Oil), private communication.)... 

Work crews must be warned to support themselves on the support beams rather than on tray sections if the column has been in operation in corrosive service. Some of the corroded tray sections may have not retained sufficient mechanical strength to support the crews. 

Flow-induced vibrations at gas rates dose to the weep point caused damage to trays, support beams, and beam to column siqiparts, at times within hours of operaticm at the damaging vapor rates. 

Defect mechanisms also affect the internals of process columns. This book is a handy guide to the assessment of vessel internals and practical solutions. Tray support rings and catalyst bed support beams are some examples of vessel internals discussed. 

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