單項(xiàng)選擇題
鐵路貨車(chē)零部件磁粉探傷時(shí),每班開(kāi)工前應(yīng)檢查磁懸液的濃度。取樣前應(yīng)對(duì)磁懸液進(jìn)行充分?jǐn)嚢瑁瞄L(zhǎng)頸沉淀管接取從噴嘴噴出的磁懸液(),靜置沉淀(),然后觀察并讀取長(zhǎng)頸沉淀管中沉積磁粉的體積,該體積讀數(shù)即為磁懸液濃度的數(shù)值(單位為mL/100mL)。
A.100mL,30min
B.100mL,40min
C.100mL,30min~40min
D.120mL,40min~50min