Gas transmission · PIR & Potential Impact Circle · 49 CFR 192.903
Potential Impact Radius (PIR)
Computes PIR = 0.69·√(p·d²) and the Potential Impact Circle area per 49 CFR 192.903, plus the Class 1/2 660-ft building trigger and HCA-overlay guidance. The 0.69 factor is for natural gas.
Pipe & Pressure
in
psig
Gas & Context
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Engineering Basis
PIR (ft) = 0.69 · √(p · d²) = 0.69 · d · √p; p = MAOP (psig), d = OD (in). 0.69 is the natural-gas factor (49 CFR 192.903).
Potential Impact Circle = circle of radius PIR; area = π · PIR², reported in acres, ft², hectares and m².
660 ft is the Class 1/2 Method-(1) trigger: PIR > 660 ft + ≥20 occupied buildings in the PIC ⇒ HCA (192.903(1)(iii)).
HCA extends axially from the first qualifying PIC through the last contiguous qualifying PIC — assess the full run.
For gases other than natural gas, substitute a heat-of-combustion factor per C-FER/PHMSA TTO-13 / GPTC Z380.1 (those factors are not validated).