PUMPING CARGO PART 2

Code No: 502

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This is part of a series of five videos that uses computer graphic techniques with animated sequences to produce concise, visually effective and informative training material. A full voice commentary describes and reinforces the highly detailed visual images.

The videos take as an example a 170,000 dwt segregated ballast tanker (no double bottom) with 7 cargo tanks, 2 slop tanks and 3 cargo pumps. The capacity of the cargo pumps is 4000 m3/hour.

Part 2 - This video concentrates on how to handle the pumps during the end of the discharge cycle phase. The task is to maintain maximum manifold pressure for as long as possible. Again the explanation starts with basics. Working in your favour are the gravity forces of the cargo and pressures from atmosphere and inert gas. But working against you are friction, vapour pressure and Net Positive Suction Head Required (NPSHR). Balancing these factors is the secret of a successful discharge, this is achieved by reducing pump speed at low tank levels then throttling the discharge valve to discharge the maximum amount of cargo. The operation of an automatic priming system is described. The next operation uses the eductors to strip empty the tanks. Emptying the slop tanks and stripping the pumps and lines completes the discharge. The delicate operation of taking in ballast using the cargo pumps is also described in detail.