Trays assembly

Horizontal Vessel, Horizontal Leaf Filters. These filters consist of a horizontal cylindrical vessel with an opening at one end (Fig. 19). A stack of rectangular horizontal trays is mounted inside the vessel the trays can usuaUy be withdrawn for cake discharge, either individuaUy or in the whole assembly. The latter case requires a suitable carriage. One alternative design aUows the tray assembly to be rotated through 90° so that the cake can faU off into the bottom part, designed in the shape of a hopper and fitted with a screw conveyor. 

Fig. 2 Bubble cap tray assembly. (Photograph courtesy of ACS Industries, Inc.)...

An alternative is to have the tray fabricated with all nuts welded to the tray pieces. This alternative saves both assembly costs and installation time, and the savings easily pay for the added fabrication costs (128, 274). It is estimated (274) that a loose-bolted tray takes 15 percent more time to install than one which has no loose bolting. Often, a loose-bolted tray assembly requires two assemblers (one to screw the bolt and the other to hold the nut), while only one assembler is required when the nuts are welded. Despite the cost and time disadvantages, loose-bolting is almost always preferred to welded nuts, because it enables easy removal of corroded or worn parts in the fiitme. Welded nuts are only justified in clean, noncorrosive services, and when installation time is critical. Sometimes, loose bolting is specified between the tray floor pieces, and welded nuts are specified for the downcomer and tray inlet areas (274). 

Failure sequence Tray assemblies, whenever possible shall be designed so that failure will occur in tbe following order ... 

The situation on a trayed tower is far more controllable. Even after the tray assembly is complete, the process engineer, using only a crescent wrench, can open a few tray deck manways and doublecheck the tower internals. But to pull 6 ft of packing out of a tower is a major undertaking. Also, trays can be stepped on without damage. Beam supports and 40-lb air guns can be dragged across a sieve tray... 

Cable tray routes as per drawing Cable tray suppoits adequate and secure Cable tray assembled and secured correctly Cable ttay earthing as per specification Cable tray earth continuity checks satisfactory Earth cables/bonds securely terminated Cables securely banded/shrouded Correct cable glands fitted Junction boxes and covers securely fitted Flameproof equipment fitted as per specification Lighting fittings correctly erected and secure Distribution boards installed and connected as per drawings... 

The situation on a trayed tower is far more controllable. Even after the tray assembly is complete, the process engineer, using only a crescent wrench, can open a few tray deck manways and double-check... 

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