This document discusses various equations that can be used to model single-phase gas flow in pipelines depending on factors like pipe diameter, length, pressure, and flow characteristics. The Weymouth, Modified Panhandle, AGA, Spitzglass, and general flow equations are each described in terms of their applicable pipeline parameters and assumptions. References and notes provide additional context on recommended practices and limitations.

1. e.g., 24” Gas Export Line
e.g.,6” Gas Line
e.g., 8” Gas Line
e.g., 8” Gas Line
Weymouth Equation
 For Smaller Dia, <=10” &
Shorter Piping of the order
of ‘feet’
 Reynolds number of the
order of > ~11x106
 Moody friction factor is a
function of relative
roughness ()
 Though, P calculated is
over estimated, it is used for
a conservative design
Modified Panhandle
Equation
 For Larger Dia, >10” & long
pipelines (> ~20 miles)
 Reynolds Numbers of the
order of (4x106 to 40x106)
 Moody friction factor is
independent of relative
roughness ()
 Condensation in Pipelines is
not accounted.
AGA Equation
 For Partially Turbulent & Fully
Turbulent flow
 Applicable when internal pipe
roughness is known accurately
 Von Karman Transmission
factor is used instead of
friction factor to estimate P
Spitzglass Equation
 For Smaller Dia, <10”
 Low pressure Vent Lines
 P < 0.1 x Pinlet
General Flow Equation
 For pressures < 7 barg
 Assumes Isothermal Flow.
i.e., no heat transfer
 Pipeline is horizontal
 No mechanical work done by
gas
CHOOSING SINGLE PHASE GAS FLOW CORRELATIONS
References
 Recommended Practice for Design and Installation of Offshore
Production Platform Piping Systems, API Recommended Practice
14E (RP 14E) Fifth Edition, Oct,1991
 Sizing of Gas Pipelines, Mavis Nyarko, International Journal of
Energy Engineering, Dec. 2015, Vol. 4 Iss. 6, PP. 202-205
Notes
 Weymouth Equation is suitable for piping within production
facility (API 14E, 5th Edition)
 API 14E does not suggest applicability of Erosional velocity
criteria for Single Phase flow, but for 2 Phase (Gas/Liquid)