Low-Pressure Fuel-Gas Pressure Drop (Spitzglass)
Pressure drop (in. w.c.) and velocity for low-pressure fuel gas via the Spitzglass equation, with a flag when the drop exceeds the low-pressure validity range.
Formula and source
Spitzglass low-pressure: Q = 3550 * K * sqrt((dH * D^5) / (SG * L)), K = 1/sqrt(1 + 3.6/D + 0.03*D). Solved for dH given Q (CFH), D (in actual bore), L (ft), SG. Velocity from Q and bore area.
Published Spitzglass low-pressure gas-flow equation (public engineering formula); the longhand alternative to the NFPA 54 / IFGC capacity tables, by name.
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