FieldEngineersKitEngineering Reference & ASME Code Basis
1. Formula & conversion factors
ANSI/ISA-75.01.01-2012 (IEC 60534-2-1 Mod) — Flow capacity equations · IEC 60534-8-3 — Aerodynamic noise prediction method · IEC 60534-8-4 — Hydrodynamic noise prediction method · ASME B36.10M / B36.19M — Downstream pipe ID and wall
Lp,1m ≈ LwA − ΔLTL − RAD
Wa = ηa · Wm · Wm = ½ · ṁ · Uv²
ΔLTL = 17 log10(tw/Di) + 36
IEC 60534-8-3 aerodynamic · IEC 60534-8-4 hydrodynamic · ISA-75.01.01 process context
Screening prediction of A-weighted sound pressure at 1 m from the downstream pipe for standard single-stage globe/butterfly trims. Acoustic power comes from jet mechanical power with regime-based acoustic efficiency; pipe-wall transmission loss uses t_w/D_i. Multi-stage low-noise trims need OEM attenuation tables.
- L_p,1m (External sound pressure level) — Predicted A-weighted level at 1 m from the downstream pipe wall (dBA).
- W_a (Acoustic power) — Sound power radiated by the valve trim (W).
- W_m (Mechanical jet power) — ½ · ṁ · U_v² stream power at the vena contracta (W).
- U_v (Vena contracta velocity) — Jet velocity from isentropic expansion (gas) or Bernoulli (liquid).
- ΔL_TL (Pipe transmission loss) — 17 log10(t_w/D_i) + 36 from downstream wall and ID.
- η_a (Acoustic efficiency) — W_a / W_m — regime-dependent screening factor.
2. Quick reference lookup table
| Quantity | Value | Unit | Notes |
|---|---|---|---|
| P1 / P2 | 10 / 2 | bar g | Gauge upstream / downstream |
| Mass flow | 15 000 | kg/h | Air / N₂-like gas |
| D_i / t_w | 102.26 / 6.02 | mm | B36 Sch 40 |
| L_p,1m | ≈ 84.6 | dBA | Safe band (< 85 dBA) |
Values are FEK IEC-style single-stage screening results. Manufacturer multi-stage or silencer packages override these levels.
3. How to use this calculator
- 1
Select downstream NPS and schedule
Wall thickness and ID set pipe transmission loss ΔL_TL.
- 2
Choose gas or liquid
Gas uses IEC 60534-8-3 aerodynamic path; liquid uses 8-4 hydrodynamic cavitation screening.
- 3
Enter Cv, P1/P2, temperature, and mass flow
Process conditions drive jet velocity, mechanical power, and acoustic efficiency.
- 4
Read L_p,1m and severity
Hero shows dBA with Safe / Caution / High badges; rows list W_a, ΔL_TL, U_v, Mach, and exposure time.
4. Engineering FAQ
A screening estimate of external A-weighted sound pressure near the downstream pipe using ISA-75.01 process context and IEC 60534-8-3 / 8-4 acoustic methods for standard single-stage trims.
L_p,1m ≈ L_wA − ΔL_TL − RAD with corrections for upstream pressure and pipe diameter. W_a = η_a · ½ ṁ U_v² and ΔL_TL = 17 log10(t_w/D_i) + 36.
Gas → aerodynamic IEC 60534-8-3. Liquid → hydrodynamic IEC 60534-8-4 (cavitation / flashing proxies from ΔP/P1).
Multi-stage low-noise trims, quiet plates, and diffuser silencers are outside this single-stage screening — use manufacturer attenuation tables.