Cause analysis of short circuit problem of tempering furnace and its solution

Many years ago, our company purchased a multi-purpose furnace heat treatment production line. After being put into use, the wiring terminal behind the tempering furnace and the shell of the tempering furnace have been short-circuited for many times, which brings inconvenience to the maintenance. At the same time, the fan motor shaft above the tempering furnace, the furnace door and the lead terminal behind the furnace also emit smoke at the beginning of the tempering process.

1. Reason analysis

This multi-purpose furnace production line is mainly used for carburizing, quenching and tempering of motorcycle engine gear, shaft, connecting rod and pin, as well as quenching and tempering of crank, etc. The quenching medium is oil. Although the parts should be degreased, cleaned and dried before quenching and tempering, it is hard to avoid a lot of oil and moisture on the workpiece due to the inaccuracy of degreasing and drying. As the temperature rises during tempering, the oil and water will evaporate. As the pressure in the tempering furnace is greater than that outside the furnace, the oil and water will spill out and turn into liquid on the outside surface of the furnace, thus reducing the resistance of the insulator between the wiring terminal and the shell. When low to the value of the short circuit occurred, the insulator was broken, the wiring terminal and the furnace shell burned together, because there is a lot of oil sludge behind the furnace, such short circuit sometimes caused fire, will be connected to the wire burned out.

2. Measures taken

From the above analysis, it can be seen that the furnace gas is emitted from the wiring because there is no dedicated exhaust duct. If the exhaust duct is added, the above problems will be reduced. Where is the exhaust outlet located? Although the gas goes up, but in order to tempering the temperature uniformity, to open the fan, in the fan's action, the furnace gas circulates, we think it is better to open the exhaust at the bottom of the workpiece shelf, so it is easy to operate. Later, we added a new exhaust system on another multipurpose furnace production line we purchased to divert the gas from the furnace to the outside. At the beginning, there is no valve part B, directly discharge the oil and water gas from the furnace to the outdoor. The existing problems are: 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 will turn into liquid, and the liquid will leak out from the joint of the pipe, polluting the indoor environment. Later, with the addition of part B, the valve at B will be opened regularly to discharge the accumulated oil and water. When tempering, open or close valve A.B as required. Valve A and B can be opened directly when tempering at low temperature. Production has proved that this has no adverse effect on quality.