Pipe Relationships

Pipe Relationships

In some industries, such as nuclear energy and shipbuilding, a com- mon need is to align mating sections of pipe in order to calculate and lay off cut planes so that the pipes can be adjoined with a high-quality weld. In general, the goal is for these adjacent pipe sections to be as coaxial as possible and to share enough material overlap such that a valid cut plane can be calculated that enables a quality weld joint.

Consider the example of replacing a steam generator that has reached the end of its service life at a nuclear power plant. A nuclear steam generator typically has a number of nozzles or pipe openings—one variant design has a “hot leg” pipe for hot water, a “cold leg” pipe for cold water, and a pipe for steam.

These piping interfaces are critical to the safety and performance of the nuclear power plant, and since they provide a direct barrier be- tween the radioactive and non-radioactive sides of the plant, they must be aligned and cut with optimal precision.

Since a nuclear reactor must be shut down in order to replace the steam generator—and since downtime at a nuclear power plant is enormously costly—anything that minimizes this downtime is extremely beneficial. Historically, cut planes were calculated manually and refined with the steam generator in its final alignment. However, this proved to be a time-intensive and therefore expensive process. Instead, the steam generator can be digitally assembled and resulting pipe cuts can be calculated before the steam generator is in its final location. As a result, the pipes can be cut prior to installation—pipe relationships play a critical role in this process.