dear all,
i want a little clarrification about how we have generalized the natural frequency of average piping is 4hz, steamlines and lines containing a flashing medium is 10hz and for lines connected to machines which give rise to vibration(ex. compressors, pump) is 8hz.please i request you all to throw some light on this issue.

regards
shravan

Sounds about right, this is best practice. So what are you asking?

dear sir,

i want to know on what basis they have generalized???

No one seems to have a clear basis for minimum acceptable NF as they are rule of thums approach. We are using 10hz for two phase and 8 hz for hydrocarbon and 4 hz for rest of lines for our offshore and LNG existing project. When these criteria can't be achieved, a formal risk assessment is recommended for the high velocity lines (5m/s for liquids and 20m/s for gases). I also want to know the basis for minimum acceptable NF.

Regards
SC