Large diameter pipes experience significantly different flow patterns in
comparison to small diameter pipes. Previous studies have shown that the
ability to reproduce flow patterns similar to those in large diameter
pipelines diminishes greatly for pipelines with an internal diameter less
than 10 cm. All multiphase flow studies at the Institute are carried out in
4-inch or 10 cm I.D. pipelines for direct correlation to larger scale
systems.
1. Erosion Corrosion in Multiphase Flow
Material degradation in industrial pipelines occurs through two main
processes: corrosion and erosion. Corrosion is a chemical or
electrochemical degradation process by which electrons from the target metal
are lost to corrosive species in the process fluid and the remaining metal
cation is left to be dissolved into the fluid or to form a protective film.
Erosion occurs due to the impact of particles on the surface of pipe walls
which mechanically removes material from the target metal surface. Industrial
pipelines which transport corrosive species and solid particles are subject to
erosion-corrosion. If both erosion and corrosion occur at the same time
there is a chance that a synergistic effect
may cause the amount of metal loss to be greater than the sum of metal loss due
to erosion and corrosion. For highly used industrial materials such as carbon
steel it is important to know how the material will wear in erosion-corrosion
environments. Despite the extensive studies performed on pure corrosion and
pure erosion mechanisms there have been few studies in order to determine the
mechanisms that occur during erosion-corrosion processes. Text written by Josh
Addis.
2. Multiphase Flow in Hilly Terrain
A unique, 10-cm diameter,
18-m long pipeline has been constructed to simulate localized multiphase
oil/water/gas flow and corrosion in the vicinity of road and river crossings
and in hilly terrain topography with short, abrupt inclination changes. The
multiphase flow line involves flow over a horizontal distance of 6 m before
reaching the crossing section. Four 9D (nine-diameter radius) bends with
2-m pipelines for the riser, crossing, and downcomer sections make up the
crossing section. The multiphase mixture then flows through a 4-m
horizontal discharge section into a separation tank. This highly complex
system exhibits flow regimes from horizontal, inclined, and vertical flows.
At any given gas and liquid flow rate, this system can experience 9
different flow regimes in different regions at the same time. The
corresponding corrosion mechanisms and corrosion rates will vary
dramatically.
3. Inclined Multiphase Flows
Unlike single-phase
flows, multiphase flows are strongly influenced by the geometry of flow. Of
the many variations in pipe geometry, the strongest influence is from the
pipe inclination. Even an inclination of 0.5 degrees can dramatically alter
the flow patterns, the boundary layer structure, and the fundamental
transport mechanisms. Two separate pipelines, 30 m in length, are located
atop a 16,000 lb structure that is fully inclinable from horizontal to
vertical. The transparent pipe sections allow for flow visualization when
studying the effect of inclination on flow patterns in multiphase flows
containing sand, oil, water, gas, and/or drag reducing agents (DRAs).
