The question of whether waterhammer analysis on new pipe systems is optional or required does not have a definite answer. In some cases it is clear - such as when the pipe system is being designed in compliance with ASME code (see How AFT Impulse Can Help Engineers Comply With ASME Codes). But in many cases it is up to experience and judgment whether or not to perform waterhammer analysis.
One of the issues complicating this question is that waterhammer events have a tendency to be non-intuitive. Thus even experienced engineers using intuition can be led astray.
I am reminded of a story one of our AFT Impulse customers told us about ten years ago. The engineer was an experienced waterhammer engineer and was fairly new to using AFT Impulse. They had a project which had 11 pipe systems. They decided to model ten of them with AFT Impulse and not model the 11th because of their previous experience which led them to believe it was not necessary. After construction one of the 11 systems had a waterhammer accident. Guess which one? That's right - the one they did not model. That experience led this customer to mandate waterhammer analysis of all future piping systems.
This whole topic is fresh in my mind as I was teaching a training seminar on AFT Impulse a couple weeks ago. There I talked with some managers who told me they had made a policy decision to offer waterhammer analysis as a standard part of their pipe design service rather than as an optional add-on. This seems to be a growing trend.
There are some industries that historically have taken waterhammer very seriously. In my experience these include nuclear power, aerospace, and the pipeline industries. A couple decades ago waterhammer was viewed as a niche area for highly trained specialists running esoteric software or (pre-computers) using complicated manual calculations. This led to a situation where some industries did not pay as much attention to waterhammer as maybe they should have for the simple reason that it was too complicated. Instead engineers relied on overdesign.
It has always been the purpose of Applied Flow Technology to make engineering software more accessible to the mainstream engineer rather than just to specialists. We have put forth a great deal of effort to develop a well organized graphical interface which in essence lowers the bar for learning to perform waterhammer analysis. With this lower barrier to entry many companies using AFT Impulse are bringing waterhammer analysis inhouse for the first time.
So getting back to the original question of this article, a practical answer is that waterhammer analysis should be performed on any system whose failure would cause significant risk to life, property or the environment. Further, systems whose failure would cause significant economic or societal impact should also be analyzed.
Many systems carrying relatively harmless fluids such as water may not require waterhammer analysis if the impact should they fail is minimal.
Engineers and their companies need to assess which category their system fits into and proceed accordingly.