Erosional velocity

Erosional velocity

Erosional velocity is a velocity of the multiphase flow at which pipe erosion occurs.

Erosional velocity equation

Pipe erosion begins when velocity exceeds the value of

$v=\frac{C}{\sqrt{\rho}}$

C/SQRT(ρ) in ft/s, where ρ = gas density (in lb/ft3) and C = empirical constant (in lb/s/ft2) (starting erosional velocity). We used C=100 as API RP 14E (1984) suggested C=100 for continuous and 125 for non continuous service.

This is the empirical relationships for estimating whether erosion will occur in a system at a certain velocity used at PQplot.

Erosion

Erosion is normally expressed as a rate of metal loss, usually mm/year. It usually occurs in turns or protrusions; or with solids content.

One can relate Erosional velocity to a metal loss rate (see RP O501).

Nomenclature

$C$ = empirical constant, lb/s/ft2

$J_D$ = dimensionless productivity index, dimensionless

$kh$ = permeability times thickness, md*ft

$\bar{P}$ = average reservoir pressure, psia

$P_{\bar{P}}$ = average reservoir pseudopressure, psia²/cP

$P_{wf}$ = well flowing pressure, psia

$P_{P_{wf}}$ = average well flowing pseudopressure, psia²/cP

$q$ = flowing rate, stb/d

$q_g$ = gas rate, MMscfd

$T$ = temperature, °R

Greek symbols

$\rho$ = gas density, lb/ft3

References

• Mokhatab S, Poe WA, Speight JG (2006) "Handbook of Natural Gas Transmission and Processing", Section 11.6 - Design Considerations on sales gas pipelines, subsection 11.6.1 - Line Sizing Criteria, Elsevier, 2006.

• RECOMMENDED PRACTICE RP O501 EROSIVE WEAR IN PIPING SYSTEMS. REVISION 4.2 - 2007. DET NORSKE VERITAS (pdf)