Session 13: Tank Cleaning Operations

Question 1

What are four reasons for tank cleaning?

Answer 1

-change grade or change cargo
-reduce potential for pollution
-control the build up of sludge and scale
-allow entry for inspection and repair

Question 2

What are some method of tank cleaning

Answer 2

-Bottom flushing with water, petroleum or chemical solvents
-water washing using tank cleaning machine
-crude oil washing

Question 3

what are the two types of washing used on tankers?

Answer 3

-Open cycle tank washing
-Closed cycle tank washing

Question 4

What should master do before the crude oil washing of tanks?

Answer 4

-Master must inform the terminal 24 hours in advance for COW

-Ship must have a COW plan in accordance with COW manual

Question 5

What are the 5 stages of crude oil wahsing?

Answer 5

stage 1: Completely discharge slop tanks and wet bottoms from cargo tanks

Stage 2: Refill slop tanks with dry crude. Commence bulk discharge of cargo tanks. Stagger tank levels to develop a trim

Stage 3: A tank levels fall sufficiently, commence top washing, wash as many tanks together as possible

stage 4: As tanks levels near the bottom, commence bottom washing. Wash as many tanks together as possible equivalent with good stripping. It is essential to keep the bottom dry during Bottom Washing

Stage 5: When there is no longer sufficient oil remaining to allow bleeding off the discharge, suspend discharge ashore and recirculate from the slop tank