Low Pressure Flow Oliphant and Spitzglass Formula and Calculator

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Low Pressure Flow Oliphant and Spitzglass Formula and Calculator

Gas gathering often involves operating pressures below 100 psi. Some systems flow under vacuum conditions. For these low pressure conditions, equations have been developed that give a better fit than the Weymouth or Panhandle equations. Two such formulas are Oliphant and Spitzglass:

The Oliphant Formula for gas flow between vacuum and 100 psi:

Eq 1
Q = 42 (24) ( d^2.5 + d³ / 30 ) ( 14.4 / P_b ) ( T_b / 520 ) [ ( 0.6 / S ) ( 520 / T ) ( ( P₁² - P₂² ) / L_m ]^0.5

The Spitzglass Formula for gas flow below 1 psig at 60° F:

Eq 2
Q = (24) (3,550) [ ( 27.69 ( P₁ - P₂) d⁵ / ( S L ( 1 + 3.6 / d + 0.03 d ) ]^0.5

Where:

Q = flow rate of gas, cubic feet per day at base conditions
d = internal diameter of pipe, in.
T_b = base absolute temperature, °R (ANSI 2530 specification: T_b = 520°R)
T = absolute temperature of flowing gas, °R
P_b = base absolute pressure, psia (ANSI 2530 specification: P_b = 14.73 psia) longitudinal weld joint factor from ANSI B31.3,
P₁ = inlet pressure, psia
P₂ = outlet pressure, psia
S = specific gravity of flowing gas (air = 1.0)
L_m = length of pipe line, miles
L = length of pipe line, feet

Reference:

Gas Processors Suppliers Association, FPS Version Engineering Data Book, 2004
F.N. Oliphant, “Production of Natural Gas,” Report of USGS, 1902.
“Steady Flow in Gas Pipelines,” American Gas Association, IGT Technical Report 10, Chicago, 1965.