Velocity · Diameter · Flow Rate
Learn erosional velocity limits, sonic velocity, pressure drop, and API RP 14E criteria
Gas velocity is calculated by dividing the actual flow rate (at operating pressure and temperature) by the internal cross-sectional area of the pipe. Formula: V = Q_actual / A.
Erosional velocity (Ve) is the speed above which pipe wall erosion becomes a concern. Per API RP 14E, it is calculated as Ve = C / √ρ, where C is a service constant (typically 100) and ρ is the gas density.
A safe gas velocity is typically below 50% of the erosional velocity limit and well below sonic velocity (Mach < 0.3). For most transmission lines, velocities are kept between 10-40 ft/s.