Question 1 TK01 - Tank Vessel Assistant - Dangerous Liquids

The Correct Answer is A **Explanation for Option A (loss of suction):** When stripping a tank (the process of removing the final remnants of liquid cargo or ballast), the system is often operating near its limits. Excessive air introduced into the suction line (due to, for example, running the tank dry, improper venting, or a leaky gland/seal) will significantly increase the volume of compressible gas within the pipeline leading to the pump. Pumps, especially centrifugal or rotary pumps used for cargo handling, are designed to move incompressible liquids. When large amounts of air or vapor enter the pump, the pump becomes "vapor-locked" or "air-bound." The pump can no longer efficiently create the necessary vacuum to lift the liquid, leading to a breakdown of the hydraulic action and resulting in a complete **loss of suction**. **Explanation for Incorrect Options:** **B) back pressure:** Back pressure is resistance to the flow created on the discharge (output) side of the pump, often caused by restrictions in the discharge line, closed valves, or excessive lift height. Air in the suction line affects the inlet efficiency, not the resistance on the outlet side. **C) an over-pressurized line:** Air in the suction line actually causes the pressure on the suction side to drop severely (often leading to cavitation and loss of prime) and reduces the discharge pressure and flow. It does not cause an over-pressurized condition. Over-pressurization is typically a consequence of restrictions or excessive pumping capacity on the discharge side. **D) increase of suction:** An increase of suction would imply that the pump is pulling liquid more efficiently, creating a higher vacuum. Excessive air in the line does the opposite: it reduces the pump's ability to create a vacuum and lowers the suction efficiency dramatically, ultimately resulting in a loss of suction.