Tube rolling

This is a manual lay-up method, where prepreg tape is rolled onto a metal mandrel on a hot table. The mandrel can be truncated when required for fishing rod blanks, ski poles and aerials. When wrapping is complete, the lay-up is over-wrapped with shrink wrap tape, which contracts when heated and applies pressure to the assembly. The wrapped mandrels are suspended vertically in an oven for curing to ensure straightness of the component. 

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FIG. 11-39 Integrally finned tube rolled into tube sheet with double serrations and flared inlet. Wo-oetine Division, UOP, Inc.)... 

Welded Tube Joints When suitable materials of construc tion are used, the tube ends may be welded to the tube sheets. Welded Joints may be seal-welded Tor additional tightness beyond that of tube rolling or may be strength-welded. Strength-welded Joints have been found satisfactoiw in veiy severe seivdces. Welded Joints may or may not be rolled before or after welding. 

Tube e] ansion after welding has been found useful for low and moderate pressures. In high-pressure service tube rolling has not been able to prevent leakage after weld failure. 

The component materials comply with apphcable ASTM specifications, but alter manufacture the outer component may increase in hardness beyond specification limits, and special care is required during the tube-rolling operation. When the harder material is on the outside, precautions must be exercised to expand the tube properly. When the inner material is considerably softer, rolling may not be practical unless ferrules of the soft material are used. 

Shell and tube Rolled ends at tube sheet Open welds at tube sheet Beneath deposits Water box gaskets Bolt holes, nuts, washers Baffle openings Disbonded water box linings... 

A rolling mill drive motor failed in service. Investigation revealed the motor was short circuited by water in-leakage. This forced a prolonged shutdown, as the motor could not be replaced on site. High humidity was initially assumed to be the problem. Upon close inspection of the motor air coolers, however, it was determined that water leaked from headboxes into the air plenum spaces. Severe corrosion at tube rolls was observed (Fig. 2.9). 

Figure 8.6 Severe grooving by ammonia-containing condensate on an admiralty brass condenser tube. Condensate flowed down the tube sheet and collected at the tube end, cutting an annular groove. Note the perforation just outside the tube roll.

The tube bundle is an assembly of tubes rolled into tubesheets and assembled into headers. See Figures 10-175, 10-176, 10-178, 10-179 and 10-180. The usual headers are plug and cover plate but can accommodate U-bend types if the design so dictates. 

Enichem and DuPont are two suppliers of acrylic elastomers. It is estimated there are 9000 t/yr of these elastomers used in the United States. The principal uses of acrylic elastomers are in automotive applications requiring both oil and heat resistance. These include transmission, valve stem, crankshaft, pinion, and oilpan gaskets and seals. In addition hose, tubing, rolls, and belts are made from acrylic polymers. 

Testing for structural integrity and testing for tiny leaks sometimes require two different approaches. Sometimes it is necessary to find leaks in systems such as a heat exchanger, which has hundreds of tubes rolled into a tube sheet. Water drips from a hydrotest may be hard to see or correct. At other times you may need to test gasketed systems that will not tolerate moisture. 

A steel pen inserted, uib backward, in the end of a smail paper tube, rolled round tbe end of a pen holder, makes a neat little scoop. It may be fastened in with a little plaster of Paris. A scoop may also be made with a quill. 

Fourth paper towel was placed on top of them. Paper towel were rolled gently to form a tube. Rolled papers were placed in suitable container in upright position covered with polyethylene bags and kept in germinating chamber on recommended temperature 20-25°C (Jennifer and James, 1997). Germination was not observed in any of the species. These dormant seeds were subjected to different dormancy breaking treatments. 

Stephan and Mitrovic [29] Standard low-fin tubing rolled to form T-shaped fins Helical circumferential reentrant cavities... 

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