The cargo has to be loaded and discharged through these lines, so the types and grades of cargo the ship can carry are determined by the type of pipeline system fitted.¹⁾

Loading and discharging the cargo has to take place without the risk of contamination from any other grade of oil or sea water that may be in the ship. With a crude oil tanker this presents little problem, because these ships seldom carry more than two or three grades of oil.²⁾

It cannot be tolerated in product tankers because the cargo is delivered directly to the customer and even minor contamination can make the product unusable or perhaps unsafe. Thus, the product tanker has a more complicated and sophisticated pipeline system than the crude oil carrier.³⁾

Pipelines are costly to install and maintain, so shipowners will fit the simplest pipeline system that is suffìcient íortheir intended trade.⁴⁾

Pipelines are mostiy made of mild Steel and can suffer corrosion, particularly in the bailast system, which contains a mixture of air and salt water, creating ideal conditions for corrosion. Many cases of cargo contamination occur because a pipeline passing through a tank becomes corroded, which results in oii passing through holes in the pipeline into the tank.⁵⁾

Some ships have ballast or brine piping manuíactured from glass-reiníorced piastic (GRP) pipes.These vyịll not corrode and so wiíl last longer than coriventional rnild Steel pipes. In some specialised chemical trades, stainless Steel pumps and lines also exist.Very sophisticated chemical parcei tankers carrying such grades as propionic and nitric acids, both of which are harder to handle than sulphuric acid, will have stainless Steel pum ps and lines.⁶⁾

Types:

• Ring main
• Block system