The Weymouth equation is one of the older equations but is still widely used for distribution and gathering systems. It was originally developed from data taken on small, low to medium pressure pipelines. When it is used for larger, high-pressure pipelines it is quite conservative, as it predicts values for Q which could be 8-12% low for gas transmission through long pipelines, the Weymouth equation is not recommended. The Weymouth equation is typically used for flow conditions:
𝐹 − Transmission Factor
𝐶𝑓 − 11.18
𝐷 − Internal Diameter (in)
𝑄 − Flow Rate (FT3/day)
𝐶𝑄 − 433.49
𝑇𝑏 − Temperature Base (°R)
𝑃𝑏 − 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝐵𝑎𝑠𝑒 (𝑝𝑠𝑖)
𝐷 − Internal Diameter (in)
𝑃1 − Upstream Pressure (psi)
𝑃2 − Downstream Pressure (psi)
𝐺 − Gas Specific Gravity
𝑍 − Compressibility Factor
𝐿𝑒 − Pipe Segment Length including Expansion (mi)
𝑇𝑓 − Gas Flowing Temperature (°R)
𝑠 − Elevation adjustment parameter
𝐶𝑆 − 0.0375
𝑍 − Compressibility Factor
𝑇𝑓 − Gas Flowing Temperature (°R)
∆𝐻𝐺 − Change in Elevation (ft)
𝐿𝑒 − Pipe Segment Length including Expansion (mi)
𝑠 − Elevation adjustment parameter
𝑉 − Velocity (ft/sec)
𝑄ℎ − Volumetric flow rate (scf/hr)
𝐷 − Internal Diameter (in)
𝑃𝑎𝑣𝑔 − Average Pipeline Pressure (psia)