1. Heavy weights exceed Crane's rated weight.
2, heavy weight is unknown.
3. The signal is unknown.
4. Heavy weights are not securely tied.
5. The open operation meets the severe weather such as gale and heavy rain and fog in the six grade (beam above five).
6, Night work lighting is not good.
7, oblique pull.
8, the steel wire rope serious wear broken stock and some people in the crane or the engine room overhaul.