Steels semi-killed

Make a preliminary mechanical design for the vertical thermosyphon reboiler for which the thermal design was done as Example 12.9 in Chapter 12. The inlet liquid nozzle and the steam connections will be 50 mm inside diameter. Flat plate end closures will be used on both headers. The reboiler will be hung from four bracket supports, positioned 0.5 m down from the top tube plate. The shell and tubes will be of semi-killed carbon steel. 

NOTE Good design practice should be followed in the selection of fabrication methods, welding procedures, and materials for vendor-furnished steel pressureretalning parts that may be subject to temperatures below the ductile-brittle transition temperature. The published design-allowable stresses for metallic materials in internationally recognised standards such as the ASME Code and ANSI standards are based on minimum tensile properties. Some standards do not differentiate between rimmed, semi-killed, fully killed hot-rolled and normalised material, nor do they take into account whether materials were produced under fine- or course-grain practices. The vendor should exercise caution in the selection of materials intended for services between 0 °C (-20 °F) and 40 °C (100 °F). 

Carbon steel boiler plate rimmed, semi-killed or killed. 30-35 50-60 BS. 1501-151 Grade 26B A42 C2 PN A36-205 DIN 17155 Hll Fe 42-1 UNI 5869 SIS 1430 ASTM A285 Grade C... 

Equation [3.1] was originally developed for semi-killed steels and it has been shown that, for C-Mn-Si steels, hardenability is better described by including in the equation an additional term, namely... 

Si/6. However, it is also found that C-Mn-Si steels show the sam risk of cracking as otherwise similar semi-killed steels when th risk is expressed as a function of cooling rate. The original form c... 

It should be noted that when [3.1] is used for semi-killed steels is relating composition to hardenability, and when it is used fo silicon-containing steels it is relating composition to hardenabilit-and likelihood of cracking. 

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