Cathodic Protection Part 1 – Pipelines

➢The amount of fluid flow through the pipeline is one of the first items of information required for design ➢ Different industries use pipeline for different purposes. requirements & types of pipe are different ➢ Petroleum industry & natural gas industry use steel pipe with welded joints. ➢ This allows the pipeline to withstand very high pressure, sometimes above 3000 psig ➢ High pressure allow the use of long pipelines, often more then 1000 miles with only a booster pump or station for each pipeline ➢ Some pipelines are designed with some excess capacity or design so capacity can be increased by the addition of compression or pumping horsepower

It is common practice worldwide for piping designers to route piping by considering mainly space, process and flow constraints (such as pressure drop) and other requirements arising from constructability, operability and reparability. Unfortunately, pipe stress analysis requirements are often not sufficiently considered while routing and supporting piping systems, especially in providing adequate flexibility to absorb expansion/contraction of pipes due to thermal loads. So, when “as designed” piping systems are handed-off to pipe stress engineers for detailed analysis, they soon realize that the systems are “stiff” and suggest routing changes to make the systems more flexible. The piping designers, in turn, make changes to routing and send the revised layout to the pipe stress engineers to check for compliance again. Such “back and forth” design iterations between layout and stress departments continue until a suitable layout and support scheme is arrived at, resulting in significant increase in project execution time, which, in turn, increases project costs. This delay in project execution is further worsened in recent years by increased operating pressures and temperatures in order to increase plant output; increased operating pressures increase pipe wall thicknesses, which, in turn, increase piping stiffnesses further. Such increased operating temperatures applied on “stiffer” systems increase pipe thermal stresses and support loads. So, it is all the more important to make the piping layout flexible at the time of routing.

• To ensure that piping is routed and supported so that no damage occurs to either the pipe or associated equipment due to the effects of thermal expansion or contraction, or loads resulting from weight, pressure, wind earthquake, pulsation, shock, foundation settlement, etc.