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一九七二年我们从上海电炉厂购进一台SL70-90A型真空电阻炉,通过一段时间的使用,发现这台设备存在着一些严重问题而影响正常工作。这台电炉是用轻质耐火砖做炉衬,而耐火砖又处于真空环境内(见附图(1))。耐火砖表面附有大量的颗粒大小不同的粉尘,这些粉尘将随着空气一起被抽入机械泵内,又不能随着空气一起排出。而被机械泵油吸收,因而污染了机械泵油。被污染后的机械泵油粘度增加,使机械泵的抽气速率下降。要恢复泵的抽气速率就必须清洗并重新换油,一般情况下每开二到三次炉就必须清洗换油一次。另外还有一些颗粒正好存在于刮片与缸体之间,严重地擦伤了缸体表面使其精度下降。而每次开炉后通过加热冷却耐火砖的表面总要挥发出一些新的粉尘,所以粉尘是抽不完的。
In 1972, we purchased an SL70-90A vacuum resistance furnace from the Shanghai Electric Furnace Factory. After a period of use, we found that there were some serious problems with the equipment that affected its normal operation. The electric stove is made of lightweight refractory bricks, while the refractory bricks are in a vacuum environment (see figure (1)). A large number of dust particles of different particle sizes are attached to the surface of the refractory bricks, which will be pumped into the mechanical pump along with the air and can not be discharged with the air. And mechanical pump oil absorption, thus polluting the mechanical pump oil. Polluted mechanical pump oil viscosity increases, so that mechanical pump suction rate decreased. In order to recover the pumping speed of the pump, it is necessary to clean and re-change the oil. In general, every second to third time the furnace must be cleaned and oil changed. In addition there are some particles just exist between the blade and the cylinder, a serious abrasion of the cylinder surface to reduce its accuracy. And after each open by firing the surface of the fire-retardant refractory bricks always volatile some new dust, so the dust is endless pumping.