8.1.2 Ring Main Piping System
greatly increases the possibility of cross contamination; however, it also allows for the maximum capacity use of all cargo pumps. This arrangement uses crossover valves for interconnection of systems, and it is here that cargo contamination is most likely to occur.
8.1 Introduction
Also referred to as a circular system. This type of piping system provides for the handling of several different types of product. This system is more versatile than direct main and has many more crossover valves; therefore, a greater chance of contamination due to the condition of internal lines. A particular tank can be pumped out either by a direct suction line or through another line by use of a cross-over.
A tanker will typically have seven to fifty cargo tanks and the function of pumps, valves and piping is to connect these tanks together. There are numerous types of piping arrangements and almost as many variations in systems as there are ships themselves. Some are relatively simple, and others are very complex, depending upon the type and variety of cargoes that the vessel was designed to carry and the level of flexibility and sophistication that the ship owner was willing to pay for. The types of piping systems that a petroleum inspector is likely to be interested in are:
• Cargo and stripping systems
• Ballast system
• Crude oil wash/fixed Butterworth system
• Inert gas and vent systems
• Heating or cooling systems
8.1.1 Direct Main Piping System
This is the simplest type of pipeline system which uses fewer valves than the others. A triple system with three pumps is the most popular of this design.
Tank valve
Master valve
Cross over valve
Tank valve
Optimum cargo handling is one grade per pump system. Additional grades can be carried but this
Master valve
Cross over valve
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