Tray Manways

Partial vertical alignment of manways is recommended (211, 399) for easy passage of lights, hoses, and commvmications and to allow personnel to stand erect. Full alignment of manways is not recommended because it increases the distance that a worker or tools can fall freely down the column. 

For multipass trays, one tray manway is required for each tray pass because the central downcomers restrict access from one side to the other. 

Some manufacturers (140, 213) market quick-opening types of manways, in which a latch replaces bolting as a means of keeping the manway in place. These offer advantages of reducing shutdown time and labor (140), but little has been published about their field performance. 

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Trays to t>e dcsiqnisd for 1/8" Max. Deflection at Design Temp-Tray Manways to oe removable fron top and ootton... 

A tray spacing of 18 in is recommended for columns 2 V2 to 4 ft in diameter (48). Here crawling between trays is seldom required, because a worker can reach the column wall from the tray manway. For such columns, the recommended tray spacing is lowered to reduce the support problems associated with tall and thin columns (see item 8 below). 

Bolts, nuts, and clamps should be made from materials having good corrosion resistance so that they can be easily imfastened after being in service. This is particuleu-ly important for bolting at tray manways. Bolts, nuts, and clamps should be to the manufacturer s standards if... 

Contract maintenance workers often will not replace the tray manways unless the tray manway is adjacent to a tower external manway. They reason that once the tray manways that are visible from the tower manway are closed, there is no way for someone to inspect the other trays. This problem is not just common— it is imiversal. The maintenance force at the Good Hope Refinery pulled this nasty trick on me at the coker fractionator. Equipped with my crescent wrench, I opened the tray internal manway below the side tower manway. 1 discovered that the 12 trays below this point had their manways stacked in their downcomers. In 1990,1 worked on a project to improve fractionation at the Chevron Refinery crude distillation unit in El Segundo, California. When the tower was opened to implement my design, the tray manways were found lying on the tray decks below the diesel draw tray. The lesson is, inspect each tray and then witness the closure of each tray manway, separately. 

Manways left off trays. Poor separation. Everything looked good. Scan interpretation did not identify problem until after the tower was opened. In fact, the trays with properly installed manways were thought to be entraining. Installation error. 

If the absorber has aceess manways, blank off a portion of the bubble eaps or valve trays. 

Area between downcomer and inlet weir for up-flow of inlet liquid. All trays included access manway. 

Shell and 2 heads Nozzles and manways Skirt, base ring and lugs Tray supports Horizontal ... 

The openings in valve trays are covered with liftable caps that adjust themselves to vapor flow. Illustrations of two kinds of valves are in Figure 13.32(b). The caps rest about 0.1 in. above the floor and rise to a maximum clearance of 0.32 in. The commonest hole diameter is 1.5 in. but sizes to 6 in. are available. Spacing of the standard diameter is 3-6in. With 3 in. spacing, the number of valves is 12-14/sqft of free area. Some of the tray cross section is taken up by the downcomer, by supports, and by some of the central manway structure. 

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