Piping Vibration Screening Calculator

Formula overview

ρ in kg/m³, v in m/s, ρv² in Pa. For AIV: ΔP and P1 in the same absolute unit so the ratio is dimensionless, W in kg/s, T in K, M in kg/kmol; PWL in dB.

Energy Institute AVIFF guidelines — likelihood-of-failure screening:

  FIV:  ρ·v²                                       kinetic energy, Pa

  AIV:  PWL = 10·log₁₀[ (ΔP/P1)^3.6 · W² · (T/M)^1.2 ] + 126.1   dB

Each result maps to a likelihood-of-failure band, and the band drives
the level of assessment and mitigation required.

Worked example

FIV: water at 3 m/s, ρ = 998 kg/m³
  ρv² = 998 × 3² = 8 980 Pa

AIV: gas across a pressure-reducing valve, ΔP/P1 = 0.5,
W = 10 kg/s, T = 400 K, M = 18 kg/kmol
  (0.5)^3.6      = 0.0825
  W²             = 100
  (400/18)^1.2   = 41.3
  PWL = 10·log₁₀(0.0825 × 100 × 41.3) + 126.1
      = 25.3 + 126.1 = 151.4 dB

Both figures are then read against the AVIFF likelihood bands to set
the assessment level for the line.

Common mistakes

• Screening the main line and forgetting the small-bore connections. Vibration failures overwhelmingly occur at vents, drains, instrument tappings, and their welds — the main line survives while a half-inch branch fatigues off in days.
• Assuming AIV is a noise problem. The acoustic power level is a fatigue driver: broadband high-frequency energy excites shell modes and cracks welded discontinuities such as branch welds and supports downstream of the source, often within hours of start-up.
• Treating a screening pass as a clearance. These are likelihood-of-failure indicators for triage. A high band means detailed assessment and probably bracing or a design change; a low band still assumes competent support design and no resonance with an excitation frequency.

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