先启动张紧位置，使输送带满足启动和运转的张紧力，令其指示器压力值达到（）MPa后，方可启动空载试运转。
参考答案：6．5～8．0
At our school, we have to wear ______ every day. [ ]
A. glasses
B. uniforms
C. hats
D. coats
防火防爆安全装置分为哪几类？所起作用是什么？
