How to use the pipe natural frequency calculator
Piping tied to a pump or compressor drops in natural frequency as the support span grows, and once it falls near the running speed or a pulsation frequency the line resonates. Resonance drives fatigue cracks at welds and small-bore branches, and instrument tubing usually fails first, so span selection has to consider frequency as well as deflection.
The tool uses the first-mode beam equation f = (λ² ÷ 2π) × √(EI ÷ mL⁴). The end condition sets λ²: 9.87 pinned-pinned, 15.42 fixed-pinned, 22.37 fixed-fixed and 3.52 for a cantilever. Mass per unit length combines the pipe wall, the contents and any insulation, and the water-filled or product-filled case is the worst one, so enter operating rather than empty conditions.
General service piping is normally kept at 4 to 5 Hz or higher. The maximum span reported here is the span that just meets your target frequency, so treat it as the starting point for a support layout. Reciprocating compressor piping and other lines with strong pulsation need a separate study to avoid the excitation frequencies, and critical systems should be reviewed by a piping stress engineer.
Frequently asked questions
Standard hangers and roller supports behave close to pinned, while welded trunnions or clamps that restrain rotation approach fixed. When in doubt, run the pinned-pinned case because it gives the lowest and most conservative frequency.
Yes. Insulation and jacketing add almost nothing to stiffness but do add mass, so leaving them out overstates the natural frequency of an insulated line.