What is meant by the term“luffing the boom”of a crane().
The boom stops on a pedestal crane prevent the boom from().
A tackle by which the outer end of a boom is raised and lowered is the topping().
The parts of the derrick are: derrick boom rest, gooseneck, center guy, stay, topping lift, topping lift block and so on.()
The pivot pin at the base of a sheath-screw boom davit must be().
A tackle by which the outer end of a boom is raised and lowered is the topping().
It is hard to tell whether the country is going to have an economic boom or a ______.
Stress on the topping lift of a swinging boom can be reduced by().
It is hard to tell whether the country is going to have an economic boom or a ______.
Our starboard derrick boom of hatch No.4 is badly cracked()that it has become entirely useless.