26.6.2 Design and Engineering Process
As shown in Figure 26.38, project concepts typically are developed by other groups. Those groups usually lead the concept development and feasibility study phases, asking the engineering department for assistance as needed.
Front-End Engineering and Design (FEED). Put the key words front-end engineering and design into any search engine, and hundreds of hits show up. The process details vary, but in general, these front-end processes seek to accomplish the same end: Solidify the design basis and key project variables early in the project’s development while the ability to influence design changes is relatively high and the cost to make these changes is relatively low, and identify key project risks so that they can be managed effectively. The design decisions made during FEED typically are captured and communicated through the use of a design-basis document and a preliminary processflow diagram (PFD).
Design Basis. While there is no universal standard as to what must be contained in a designbasis document, most pipeline operating companies and engineering design firms have their own requirements and format. At a minimum, the following parameters normally are captured and communicated in the design basis
- Design capacity—a point value to which the design is optimized; for pipelines, pump stations, or truck loading or unloading facilities, the design capacity is normally quantified as a volumetric flow rate
- Operating range—the range of operating flow rates anticipated by the design and for which equipment is to be sized to accommodate
- Identification of fluid properties (density, viscosity, specific heat)
- Operating temperature range
- Applicable codes and standards
- Process control philosophy
- Preliminary route, including topography, and receipt and delivery locations with volumes
- Sensitivities regarding customers, regulators, public opinion, geologic, environmental, or other considerations that would affect line design or routing
- Project economics and economic sensitivities
- Special operating considerations
Process-Flow Diagram. Prior to starting detailed design, engineers prepare a process-flow diagram, a schematic representation of the major equipment components, flow direction, and receipt and delivery locations (Figure 26.39). The amount of detail contained on the process-flow diagram varies between companies, but whatever the level of detail, it must be sufficient to convey to the design engineer what is expected.
With the overall flow and specific parameters defined, it is time to get down to the business of detailed design and engineering, an often iterative process. Engineering design tasks often are divided between design of the cross-country pipeline and design of the stations—pump, compressor, and receipt and delivery.
FIGURE 26.39 Process-flow diagram. This process-flow diagram of a receipt station provides the piping designer with detailed information regarding the intent of the facility. (Courtesy Vanderpool Pipeline Engineers Inc.)