Figure 4-13 ers, the part of the tip that fits into the torch head often shows the different styles of tips, their orifice arrange- differs in design. Because of the way the Navy pur- ments, and their uses. The tips and seats are designed to produce a even flow of gas and to keep themselves as cool as possible. The seats must produce leakproof joints. If the joints leak, the preheat gases could mix with the cutting oxygen or escape to the atmosphere, resulting in poor cuts or the possibility of flashbacks. To make clean and economical cuts, you must keep the tip orifices and passages clean and free of burrs and slag. If the tips become dirty or misshapened, they should be put aside for restoration. Figure 4-14 shows four tips: one that is repairable, two that need replacing, and one in good condition. Since it is extremely important that the sealing surfaces be clean and free of scratches or burrs, store the tips in a container that cannot scratch the seats. Aluminum racks, plastic racks, and wood racks or boxes make ideal storage containers.
TIP MAINTENANCE.— In cutting operations, the stream of cutting oxygen sometimes blows slag and molten metal into the tip orifices which partially clogs them. When this happens, you should clean the orifices thoroughly before you use the tip again. A small amount of slag or metal in an orifice will seriously interfere with the cutting operation. You should follow the recommendations of the torch manufacturer as to the size of drill or tip cleaner to use for cleaning the orifices. If you do not have a tip cleaner or drill, you may use a piece of soft copper wire. Do not use twist drills, nails, or welding rods for cleaning tips because these items are likely to enlarge and distort the orifices. Clean the orifices of the cutting torch tip in the same manner as the single orifice of the welding torch tip. Remember: the proper technique for cleaning the tips is to push the cleaner straight in and out of the orifice. Be careful not to turn or twist the cleaning wire. Figure 4-15 shows a typical set of tip cleaners. Occasionally the cleaning of the tips causes enlargement and distortion of the orifices, even when using the proper tip cleaners. If the orifices become enlarged, you will get shorter and thicker preheating flames; in addition, the jet of cutting oxygen will spread, rather than leave the torch, in the form of a long, thin stream. If the orifices become belled for a short distance at the end, you can sometimes correct this by rubbing the tip back and forth against emery cloth placed on a flat surface. This action wears down the end of the tip where the orifices have been belled, thus bringing the orifices back to their original size. Obviously, this procedure will not work if the damage is great or if the belling extends more than a slight distance into the orifice.
After reconditioning a tip, you may test it by lighting the torch and observing the preheating flames. flames are too short, the orifices are still partially blocked. If the flames snap out when you close the valves, the orifices are still distorted. If the tip seat is dirty or scaled and does not properly fit into the torch head, heat the tip to a dull red and quench it in water. This will loosen the scale and dirt enough so you can rub it off with a soft cloth. MAPP GAS CUTTING TIPS.— Four basic types of MAPP gas cutting tips are used: two are for use with standard pressures and normal cutting speeds, and two are for use with high pressures and high cutting speeds. Only the standard pressure tips, types SP and FS, will be covered here since they are the ones that Steelwork- ers will most likely use. SP stands for standard pressure and FS for fine standard. The SP tip (fig. 4-16, view A) is a one-piece standard pressure tip. It is used for cutting by hand, especially by welders who are accustomed to one-piece tips. SP tips are more likely to be used in situations where MAPP gas is replacing acetylene as the fuel gas. The FS tip (fig. 4-16, view B) is a two-piece, fine spline, standard pressure tip. It is used for cutting by hand as well as by machine. Welders accustomed to two-piece cutting tips will use them in hand cutting, especially when MAPP gas is replacing natural gas or propane as the fuel gas.
The FS tips will produce heavier preheating flames and faster starts than the SP tips; however, two-piece tips will not take as much thermal or physical abuse as one-piece tips. But in the hands of skilled Steelworkers, they should last as long as one- piece tips. Recommended tip sizes and gas pressures for use in cutting different thicknesses of steel using MAPP gas as a fuel are given in table 4-1.
本文转自：China Industry News