Many years ago, our company purchased a multi-purpose furnace heat treatment production line, since the use of the furnace, the terminal behind the tempering furnace and the tempering furnace shell many times short circuit, which brings inconvenience to maintenance. At the same time, the fan motor shaft above the tempering furnace, the furnace door and the lead terminal behind the furnace are still smoking out in the early stage of the tempering process.
1. Cause analysis
This multi-purpose furnace production line is mainly used for carburizing, quenching and tempering of motorcycle engine gears, shafts, connecting rods and pins, and tempering of crank, etc. The quenching medium is oil. Although the parts should be degreased, cleaned and dried before tempering after quenching, it is inevitable that a lot of oil and water will remain on the workpiece due to the incompleteness of degreasing and drying. During tempering, as the temperature rises, the oil and water evaporate, because the pressure inside the tempering furnace is greater than the outside of the furnace, the oil and water spill out and become liquid on the outside surface of the furnace, thus reducing the resistance of the insulator between the terminal and the shell. When it is low to a certain value, a short circuit occurs, the insulator is broken down, the wiring terminal is burned together with the furnace shell, because there is a lot of sludge behind the furnace, so that the short circuit sometimes causes a fire, and the connecting wire is burned.
2. Measures taken
From the above analysis, it can be seen that the reason why the furnace gas emerges from the wiring is because there is no special exhaust duct. If the exhaust duct is increased, the above problems will be reduced. So where is the exhaust port located? Although the gas goes up, but in order to temper the temperature uniformity, to open the fan, under the action of the fan, the gas in the furnace is in a circulating state, we think that the exhaust port is open at the bottom of the workpiece shelf is better, so it is easy to operate. Later, we added a new exhaust system to another multipurpose furnace production line that we purchased to divert the gas from the furnace to the outside. At the beginning, there is no valve part B, and the oil and water gas in the furnace are directly discharged to the outside. The problem is that when the oil and water gas in the furnace flow through the pipe outside the furnace, due to the low temperature of the pipe, the oil and water gas become liquid, and the liquid oozes from the pipe interface, polluting the indoor environment. Later, the B part is added, and the valve at B is opened regularly to discharge the accumulated oil and water. When tempering, the valve can be opened or closed as required A.B. Valve A and B can be opened directly during low temperature tempering, which has no adverse effect on quality.