For all pipeline projects, a method must be chosen to select the pipe diameter. These methods range in complexity from someone’s “gut feel” to transient multi-phase optimization studies. Regardless of the project’s complexity or scope, pipeline sizing calculations require some common decisions. The pipeline designer must decide what fluid flow rates or ranges of fluid flow rates to use in the design. The designer must also determine what criteria to use to select the pipe size (usually fluid velocity, pressure loss, and/or pressure loss gradients).
More complex and rigorous analyses of pipeline projects have some significant advantages. On some projects they may save money by avoiding over-sizing that can occur due to conservative assumptions that are often used in less rigorous analyses. More rigorous analyses typically have the advantage of being run by a very experienced engineer, who is likely to understand the fundamental principles of the calculations better than a less experienced engineer who might run a less rigorous analysis.
There are also disadvantages to the more rigorous design approaches. The software required is often expensive, and training required may also have a significant cost in time and money. The pool of users capable of performing such studies may also be very limited. Complex, rigorous design studies also require more extensive assumptions, which may lead to wider variations in results from one engineer to another. The increased complexity of the analysis makes it more difficult to convey the assumptions to management—limiting the transparency of the design process.
This paper describes a standardized approach to the pipeline sizing process. This approach allows the pipeline designer to delegate portions of the design work to personnel who are not experienced hydraulics engineers. For more complex projects, the standardization is limited to recommended pipe sizing criteria based on velocity, pressure loss, and pressure gradient. For less complex projects, two spreadsheet-based tools have been developed to further standardize the process and allow delegation of design tasks to those not familiar with more complex pipeline design tools.