Multiphase flow line and Trunk line Basic Hydraulics and Flow Assurance

A: The hard boundary is erosion onset, not regulatory coverage. API 14E exists to limit metal loss driven by particle impact and droplet impingement in multiphase flow; it's a screening tool, not a slugging control or a legal shield under COMAH.

A: The threshold is free water presence. Bulk removal first limits liquid holdup, and drying to a defined dewpoint before hydrocarbons avoids hydrate conditions; reversing the order traps water and builds slug volume.

A: The tipping point is holdup, not friction. At lower velocities, liquid accumulates in low spots, raising hydrostatic head and upstream pressure; terrain slugging assessment comes before aggressive valve moves or chemical shots.

A: The anchor number is cross-sectional area times elevation-driven fill length. A 12" line holds about 0.07 m²; 20 m of effective liquid column gives roughly 1.4 m³ per low point, and multiple low spots push the total into the tens, not single digits or full-line fill.

A: The hard boundary is MAWP margin. When measured behavior contradicts datasheet assumptions, the model must move to measured roughness to confirm pressure integrity and downstream operability before operational tweaks.

A: The threshold is free water presence with H2S. Even trace aqueous phases in wet gas create cracking risk; phase fraction doesn't remove the metallurgical mechanism addressed by MR0175.

A: The boundary condition is GVF tolerance. Coriolis accuracy collapses outside its multiphase envelope; confirming operating regime comes before chasing control or scaling issues.

A: The trigger is crossing the hydrate curve. Chemical inhibition per plan addresses the phase equilibrium directly; hydraulic tweaks may lag and a shutdown is disproportionate without confirmation.

A: The scale-setter is gas dominance. At high GVF and moderate velocities, friction tracks closer to gas-phase behavior; liquid holdup adds head but not an order-of-magnitude jump into tens of bar for typical trunklines.