Damaged trays

Whatever the cause of the tray damage, however, it is often hard to prove tray damage without column shutdown and inspection, especially if damage is slight. Besides poorer fractionation, a damaged tray section will experience a decrease in temperature difference because of the... 

If a tower does become flooded in the bottom section, a common operator error is to try to pump the level out too quickly. This can easily damage trays by imposing a downward acting differential pressure produced by a large weight of liquid on top of the tray and a vapor space immediately below the tray. To eliminate the flooding, it is better to lower feed rate and heat to the reboiler. It is important to be patient and avoid sudden changes. 

Gravity cycles tend to be most severe in column bottom lines. These cycles can be quite violent, can dislodge and damage trays and packing support plates, and in some cases, even pull a vacuum deep enough to collapse a vessel (158). Gravity outlet lines should be surveyed with special care to ensure no gravity cycle can form. 

The mechanism of transforming the above fluctuations into vibrations capable of damaging trays is not clear. Amplification by acoustic or mechanical resonance is commonly postulated (62, 108, 329, 425). Some predictive models and correlations have been proposed (62,108, 329, 330, 425). 

If the liquid layer is deep (i.e., several of the lower trays may be flooded), vapor may travel through the liquid in the form of slugs. These can loosen bolting and other fasteners, damage trays, or lift trays off their supports (61,150a, 192, 207, 295), collapse packing supports (237), and cause column vibration and structural damage. 

A shutdown column contained flammable gas. Work was performed on a ground-levd exchanger in the column product line. The product line was purged by inert gas pumped backward into the column, and out throu the t<9 of the coliunn. Air managed to get into the coltmm, and an explosion whidi damaged trays occurred. 

Actually, the tray decks are not ripped away from the support ring. Inspection of damaged trays indicates the decks have been bent at the ring. The trays are not bolted to the tray ring they are clipped to the support ring (see Fig. 3—5). In the course of bending, the tray pulls the tray clips away from the support ring. 

However, the largest operating cost for many process units is the energy supplied to the reboilers. We should therefore avoid high reflux rates, and try to achieve the best efficiency point for distillation tower trays at a minimum vapor flow. This is best done by designing and installing the tray decks and outlet weirs as level as possible. Damaged tray decks should not be reused unless they can be restored to their proper state of levelness, which is difficult, if not impossible. 

Damaged tray decks should not be reused unless they can be restored to their proper state of levelness, which is difficult, if not impossible. 

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