German carburizing production oil cooling pump technology

German carburizing process 2020 - line oil cooling pump 02 - 27 Ren Guihu ( Tianjin auto works Xiali Automobile Co. , Ltd. , the internal combustion engine manufacturing branch) Tianjin auto works Xiali Automobile Co. , Ltd. , the internal combustion engine manufacturing branch carburizing heat treatment production line is introduced from Germany in 1995, the production line is double row push-rod type, quenching tank is closed oil tank, oil tank temperature with bi-directional temperature control. Heating up, use the insertion type electric heater, cooling by the oil suction pipe cooling plate heat exchanger ( See figure 1) , quenching cooling medium for tap water. Figure 1 tank cooling system heat exchanger heat exchange system existence question and the oil cooling pump are installed in the main body between the furnace and the tempering furnace in the pit, the pit depth of 2800 mm, the pipe layout is compact, the internal maintenance pit space is small, and the operation of the equipment, in the pit environment temperature above 60 ℃, working condition is bad. The heat exchanger in the system a long service life, use cycle (in a 3 months) Rarely fails, but oil cooling pump for bearing damage and often mechanical seal damage due to stop line maintenance, because the space is narrow, the environment temperature is high, the maintenance work progress is slow, the average need to stop line 1 ~ 2 h, cause certain influence to the quality and production. At the same time, because the area of the pit work belongs to the confined space work, overflow of exhaust gas in furnace and the carbon dioxide easily enriched in the pit, the risk of suffocation, heatstroke. Comprehensive above factors, the existing heat exchange system needs modification to eliminate due to impact of the stop line oil cooling pump failure, reduce the maintenance staff labor intensity and to eliminate the risk of confined space operations. Retrofit scheme mentioned above, because a heat exchanger tube plate structure, when the design considered the characteristics of the water, the seawater corrosion of 316 l stainless steel, basic can satisfy the whole cycle use don't leak and oil-water mixed fault, so it's not our eyes. We focus on the key is to try to pump oil cooling from the pit to, above the ground through the bypass design at the same time, realize fault line maintenance, maintenance and the safety of the equipment operation to eliminate personnel. , this pump is horizontal centrifugal pipeline pump lift 90 m, the flow rate of 740 m3, no self-priming function itself, so the arrangement of the position of the low of a hole in the ground below the bottom of the tank in order to realize automatic suction row, if purely from the pit to install above the ground, may be due to reduced flow cooling speed slow, even for not resulted from automatic control on the oil absorption. In general, if in order to realize automatic repeat start centrifugal pipeline pump, usually installed to bottom valve or low, but the tank in order to guarantee will be heat oil in a timely manner when the quenching cooling, oil suction mouth up in high level, so the bottom valve installation is not possible, this is the original design will pump installed in the cause of the low. The arrangement of each element of the cooling system parameters of the center line of the oil cooling pump is located in the bottom of above 132 mm; To bottom relative to the ground to - Present situation of 2800 mm, oil cooling pump axis relative to the ground to - 2668mm； Oil suction mouth is located in the 390 mm above the ground. So, the center line of the oil suction mouth and oil cooling pump height difference of 390 + 2668 = 3058 mm. Considering the parameters of the oil cooling pump up to the ground for installation: the center line of the oil cooling pump is located in the 132 mm above the ground; Oil suction mouth is located in the 390 mm above the ground; Oil suction mouth and oil cooling pump centerline height difference of 158 mm. Consider tank liquid level in the work at the same time should maintain in 490 ~ 590 mm above the ground, so the ground installation oil suction mouth and oil cooling pump centerline height difference in 258 ~ 358 mm, this pump can achieve installed above the ground. Concrete plans to be on the safe side, does not destroy the original system, we will be at the bottom of the tank unicom oil cooling pump vent pipe cut-off valve, normally closed state formation, using the oil cooling oil pump the front-end interface in the vent pipe lead to a vertical pipe, received the above the ground, in addition to install an oil cooling pump, oil outlet into the original pipeline, completed the bypass system arrangement, the new pump motor fuses in the electrical enclosure by adding circuit breaker manual switch, two road by field operation personnel rearrangement of valve opening and closing of circuit breakers and related two pump control switches. But the pump cavitation allowance, parameters such as suction on the manual does not provide, relevant calculation could not be combined with the experience, we fear that because of the decrease of height difference and pump capacity is too big, may in the process of pulse control start-stop for discharge and suction quantity does not match the causes between the pump body and vertical pipe cavity, repeated accumulation may cause the damage of the pump, so we on the riser is lower than stainless steel check valve installed on the position of the oil tank, the reverse blocking, ACTS as the valve, the pump stops, the transverse residual oil in the pipeline will be added in the riser, ensure the pump impeller has been immersed in the oil, so as to realize repeatedly start-stop ( See figure 2) 。 Figure 2 pipeline renovation process, considering the launch tube without oil for the first time, started to eliminate gas resistance, so the pre-installed the mouth filling with relief port, at the same time in order to be completely recycled at replacing heat exchanger heat exchanger in the residual oil, its lowest level in pipe installed oil drain valve, so as to realize the maintenance process without leakage, without waste. After the completion of the system reform, through oil, deflated, switch, etc, a new pump start-up success, cooling capacity compared to the original installation low pump, about the same, so as to succeed. After half a year or so of observation after operation, another line on the basis of this, also more than two pump are arranged on the ground, at the same time will switch valve are arranged above the ground, eliminated under operation in the pit of homework. Source: the metal processing ( Hot working) Magazine,