Piping & Instrumentation Diagrams

Several kinds of pipe flow calculations can be made with the Darcy- Weisbach equation and the Moody friction factor. These calculations can be conveniently carried out with an Excel spreadsheet. Many of the calculations require an iterative solution, so they are especially suitable for an Excel spreadsheet solution. This course includes discussion of the Darcy- Weisbach equation and the parameters in the equation along with the U.S. and S.I. units to be used. Example calculations and sample Excel spreadsheets for making the calculations are also included. This course is intended primarily for civil engineers, mechanical engineers, chemical engineers, and environmental engineers. After completing this course you will be able to make calculations with the Darcy Weisbach equation and the Moody friction factor equations to calculate several different unknown parameters when sufficient input data is provided. You will also be prepared to use Excel spreadsheets to efficiently make the calculations.

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.