Cause analysis and solution measures of short circuit problem in tempering furnace

Many years ago, our company purchased a multi-purpose furnace heat treatment production line. After it was put into use, the wiring terminals behind the tempering furnace and the tempering furnace shell had multiple short circuits, which caused inconvenience to maintenance. At the same time, smoke still emanates from the fan motor shaft above the tempering furnace, the furnace door, and the lead terminals behind the furnace during the early stages 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, as well as quenching and tempering of cranks. The quenching medium is oil. Although the parts need to be degreased, cleaned, and dried before quenching and tempering, due to the incompleteness of degreasing and drying, it is inevitable that a lot of oil and water will remain on the workpiece. During tempering, as the temperature rises, oil and water evaporate. Due to the pressure inside the tempering furnace being greater than outside, oil and water spill out and turn into liquid on the surface outside the furnace, resulting in a decrease in the resistance of the insulation between the wiring terminals and the casing. When a short circuit occurs when it reaches a fixed value, the insulation is broken down, and the wiring terminals are burned together with the furnace shell. Due to the presence of a lot of oil sludge behind the furnace, this short circuit can sometimes cause fire and burn out the connecting wires.
2. Measures taken
From the above analysis, it can be seen that the reason why the furnace gas emerges from the wiring is due to the lack of a dedicated exhaust duct. If the exhaust duct is increased, it will reduce the occurrence of the above problems. So where is the exhaust port located? Although the gas is moving upwards, in order to maintain uniformity during tempering, it is necessary to turn on the fan. Under the action of the fan, the gas in the furnace is in a circulating state. We believe that it is better to open the exhaust port at the bottom of the workpiece rack, which is also convenient for operation. Later on, we added an exhaust system on another multi-purpose furnace production line that we purchased, directing the gas inside the furnace to the outside. At the beginning, there was no valve in section B, and the oil, water, and gas in the furnace were directly discharged outdoors. The problem is that when the oil and water vapor inside the furnace flow through the pipes outside the furnace, due to the low temperature of the pipes, the oil and water vapor become liquid, and the liquid seeps out from the pipe interface, polluting the indoor environment. Later, part B was added, and the valve at part B was regularly opened to discharge the accumulated oil and water. During tempering, valve A can be opened or closed as needed B. During low-temperature tempering, valves A and B can be directly opened, and production has proven that this has no adverse effect on quality.