單項(xiàng)選擇題灰漿輸送泵需連續(xù)運(yùn)轉(zhuǎn),短時(shí)間內(nèi)不用砂漿時(shí),可打開(kāi)回漿閥使砂漿在泵體內(nèi)循環(huán)運(yùn)行,如停機(jī)時(shí)間較長(zhǎng),應(yīng)每隔()泵送一次,使砂漿在管道和泵體內(nèi)流動(dòng),以防凝結(jié)而阻塞.

A.2-4min
B.3-5min
C.4-6min
D.5-7min