Dear MoverZ,

Again, thanks for you explanation. I quote this from Sam Kannnapan's Book. "The maximum allowable spans for horizontal piping system are limited by three main factors: bending stress, vertical deflection, and natural frequency. By relating natural frequency and deflection limitation, the allowable span can be determined as the lower of calculated supports spacing based on bending stress and deflection."

I would like to know the reference for the factor you mentioned. I don't know if Sam Kannapan already added in the new edition. I have the old one.

When I write assumption (1) end moment neglected; I do really understand that this will give most conservative result. For simply supported beam +Y support for both ends is the example which cause moments are zero at the both ends, higher deflection which will produces lower fn instead of ANCH.

If one day there is a equipment which imposed 1000 cps dynamic load to our piping system, do we need to revise tabulation of pipe span length?