单项选择题
A.prevent the passage of flammable gases B.prevent the passage of poisonous vapors C.delay the spread of heat and flames D.maintain watertight integrity
Limit switches are used on which davits?（）A.Sheath-scre...
单项选择题Limit switches are used on which davits?（）
A.Sheath-screw davits B.Gravity davits C.Radial davits D.Quadrantal davits
In the piping systems of a vessel，what type of valve gi...
单项选择题In the piping systems of a vessel，what type of valve gives the least resistance to fluid flow when fully open?（）.
A.Globe valve B.Butterfly valve C.Gate valve D.Packless valve
In ship operations，hoisting and lowering pipe in and ou...
单项选择题In ship operations，hoisting and lowering pipe in and out of the drilled hole is the main function of the（）.
A.swivel B.cathead spool C.drawworks D.stand pipe
