Tray ring

The peripheral stiffening zone (tray ring) is generally 25 to 50 mm (1 to 2 in) wide and occupies 2 to 5 percent of the cross section, the fraction decreasing with increase in plate diameter. Peripheiy waste (Fig. 14-28) occurs primarily with bubble-cap trays and results from the inabihty to fit the cap layout to the circular form of the plate. Valves and perforations can be located close to the wall and little dead area results. Typical values of the fraction of the total cross-sectional area available for vapor dispersion and contact with the liquid for cross-flow plates with a chord weir equal to 75 percent of the column diameter are given in Table 14-6. 

Mechanical tray layout details. Allow a total of 3H-in. on diameter for extension of tray ring-type support into the tower. This reduces available tray area. Other support details might make more area arail-able. Each must be examined. 

Whenever a product draw is taken from a collector pan, the liquid fiow through any orifice hole depends on the local height. This guarantees that some degree of liquid maldistribution will take place. Additionally, orifice-pan distributors are installed on tray rings welded to the tower wall. If the tray ring is not level, the orifice pan will have liquid maldistribution caused by the out-of-level installation. 

Minor beam -- - support clamp Peripheral ring clamps (Note Slotted tray is frictionally held to promote breathing) Subsupport tray ring (used with angle ring)... 

In order to minimize dead liquid pockets and irregularities at the wall, it has been recommended to internally blind unused nozzles (299a) in the packed zone. Item 6 in Sec. 10.4 describes techniques for removing tray rings. 

A leaking valve tray in trapout service was replaced by an aU-welded chimney trEQT, which was seal-welded to the tray ring. Leakage was eliminated. 

BEAM SUPPORT ON TRAY RING BEAM ABOVE LOS... 

The operating superintendent of a medium-sized crude unit obliterated all of the above difficulties. He tore out the valve trapout tray and drawoff pan. A new, all-welded pan was installed. Several large chimneys allowed for vapor passage. The pan was seal-welded to the tray ring and the problem was corrected. (Note, in large-diameter towers, a seal weld can fail due to thermal expansion.)... 

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. 

Eirill 14-inch holes through the tray and tray ring. This will also marginally increase tower capacity. 

Drilling holes through the edge of the tray and through the tray ring is an especially nice way to coax a bit more capacity out of small-diameter towers. 

Shear clips Weld the shear clip to the underside of the tray as shown in Fig. 5.8, but certainly not to the tray ring. 

Bolt the trays to the tray ring, or use back-to-back trays with shear clips (see my book. Process Design for Reliable Operations, for mechanical details). This will help to avoid tray failures due to pressure surges caused by high liquid levels. 

Fig. 8.9. Cutaway drawing of Crown/Schumacher desolventizer-toaster-dryer-cooler (DTDC). Note the stacked design of tray (ring) heaters-coolers with sweep arms, and steam-jacketed and perforated bottoms. Stack cookers generally have solid steam-jacketed bottoms for heating oilseeds. (By permission of Crown iron Works Company, Minneapolis, MN.)...

Underneath the tray, where the tray panels are bolted together, there is a narrow vertical strip of steel which is called the integral truss. This truss is not connected to the tray ring. Referring to Fig. 8.4,... 

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