Which process is most commonly used for small pipe maintenance welding? D. Oxyacetylene gas welding What is the proper definition of an engine? B. It is machine designed to convert energy into useful mechanical motion What is wet stacking and how can it be prevented? C. Wet stacking is a condition in diesel engines in which unburned fuel passes on into the exhaust system. [1] The word "stacking" comes from the term "stack" for exhaust pipe or chimney stack. The oily exhaust pipe is th...