正常情况下，在工程机械的一个大修期内，进行三级保养2次、二级保养4～8次、一级保养12～34次较为合适。
Under normal conditions , it is suitable for us to carry out primary maintenance 12 times ~ 34 times , two-level one 4 times ~ 8 times and three-level one twice during an overhaul period .
二级保养