Anyone who’s operated a stacker-reclaimer knows that these machines rely on heavy-duty, counterweight-type tensioning devices for their boom-mounted belt conveyors. But when dealing with sticky, wet materials entering the plant, the non-working surfaces of the conveyor belts often accumulate significant amounts of fine mineral dust. As the belt passes over the counterweight-driven return rollers, this buildup is effectively "scraped off," yet it still tends to fall—sometimes even causing the belt to drift off course and leading to severe material spillage.

By 1970, the Eighth Ministry of Machinery (the Ministry of Agricultural Machinery) merged with the First Ministry of Machinery—retaining the name "First Ministry of Machinery"—to oversee the civilian machinery industry. Meanwhile, the Second through Seventh Ministries of Machinery were placed under the leadership of the General Staff Office Group, responsible for managing the military industrial sector. As a result, the number of major national ministries and commissions related to machinery was reduced to seven. However, in 1975, a new entity—the Eighth Bureau of the Ministry of Machinery—was spun off from the Seventh Ministry of Machinery (the Ministry of Aerospace Industry). This bureau took charge of the production, research, education, and development planning for tactical missiles. In 1979, it was officially upgraded to the Eighth Ministry of Machinery. This marked the second historical instance of an "eight-ministry coexistence," though this time the shift was particularly significant: the original focus on agricultural machinery had been replaced by a strong emphasis on tactical missile systems, representing a substantial cross-sectoral transition.