In readying an auxiliary water-tube boiler for a routine hydrostatic test, which of the following procedures should be undertaken prior to filling the boiler with fresh water?（）
A. The safety valve escape piping should be disconnected from the valve body and a blank inserted
B. The boiler vent valves should be opened
C. All handhole/manhole covers should be tightened up as much as possible to preclude any leaks
D. All of the above
微信支付 
支付宝支付