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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoPlainText><span style='color:#1F497D'>Dear Peter in Auz<o:p></o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>Thanks for the shout.<o:p></o:p></span></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>>I think the nozzle of an oxygen-acetylene cutting torch is identical to a propane-oxygen ditto. The ring of small premixed flames serves to preheat the workpiece (steel) to a temperature where the central jet of oxygen can begin to burn, heat, melt and disperse the molten steel.<o:p></o:p></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>They ‘work' in the same way but the flame pattern is different. The Oxy-Acet has perhaps 6 holes and the propane-oxy has perhaps 10-20 little ones. There is a great picture of the two at</span><span style='color:black'> <a href="http://www.cousesteel.com/AndysPlace/PropaneAcetylene.html">http://www.cousesteel.com/AndysPlace/PropaneAcetylene.html</a> <o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>That is the smallest number of holes I have seen for propane. And the shape is odd to. Usually the whole circumference is like a W bent around in a circle: wwwwwwww like that.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>The explanation about cutting and welding with propane is incorrect but the pictures are good.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>I am including a small portion of a zoomed photo from </span><span style='color:black'><a href="http://www.alibaba.com/product-gs/433428317/Cutting_Torch_Welding_Torch/showimage.html">http://www.alibaba.com/product-gs/433428317/Cutting_Torch_Welding_Torch/showimage.html</a><o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><img border=0 width=132 height=153 id="Picture_x0020_1" src="cid:image001.png@01CCD592.7AA077A0"><span style='color:black'><o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>The left part is a sleeve and the right part is the brass core. There are linear grooves cut perhaps 40mm long leading to the tip. The sleeve closes over the grooves providing a number of high velocity jets of propane around the central O<sub>2</sub> hole. I think the reason for them is that the flame speed of the propane is higher than the acetylene and the increased velocity through small holes prevents flashbacks when hot.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>Starting a cut with propane is more difficult because of the higher velocity gas stream (more than double the air is needed) so localising the heating at the beginning is important. The multi-jet approach might assist that.<o:p></o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoPlainText><span style='color:#1F497D'>Crispin the (long suffering) welder<o:p></o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p><p class=MsoPlainText><span style='color:black'><o:p> </o:p></span></p></div></body></html>