Water hammer or natural freqency.

Hi
I've heard that one should choose the first natural frequency higher than 4-5Hz to reduce the risk of damage to the piping system. You must add dampers. We live in an area without risk of earthquake but we do have bad drainings and therefore big risk for water hammer.
Please let me know your opinion about this!! Thanks!
Peter Algotsson from Sweden.

Bad drainage is not the cause of and therefore not a risk for water hammer.

Look here for the definition and cause for Water Hammer]en.wikipedia.org/wiki/Water_hammer[/url]

Thanks, now I know what a water hammer is. I did a bad translation from Swedish and therefore the miss understanding.
Let me put it this way. When we start up steam pipe we start with cold pipes which generates condensat that should be drained. If water is not drained, the steam will send the water with at very high speed and when this water hit a bend it can cause a vibration. Do you agree?

What is your criterion for selecting the first natural frequency? Or do you do as we did 20 years ago?

I found these articles on the internet that may help answer your question.
turbolab.tamu.edu/proc/turboproc ... 19-134.pdf
turbolab.tamu.edu/proc/turboproc ... l28019.pdf

I'm most certainly no expert in these matters, but I do have some thoughts, so take the following as only the thoughts of someone who has been involved in piping design for many years and continue to seek expert advice.

It seems to me that there is a big difference between a natural frequency or harmonic vibration that occurs in piping connected to such as a reciprocating compressor and the violent and sudden vibration encountered by the piping ahead of such as a slug catcher; the former being uniform, constant and predictable, and the latter being non uniform and varying in frequency and intensity. I think you'll find that the design considerations for the two scenarios are quite different.

In short, I believe that you will find that your initial question about natural frequency can't be correlated to your subsequent example of condensate water hammer in a steam line during start-up.

Keep in mind that I’m speculating to generate further thought. We all live and learn, so please share your findings with us.