Is there any fomurmla for corrision calculation in piping?

Question

Is there any fomurmla for corrision calculation in piping?

Answer 1

Estimate the corrosion rate:

R = K * { [mb - ma] / A * Δt *ρ }                                                    

where:

                         R = penetration rate (mil/y or mm/y)

                         mb = mass before exposure (gram)

                         ma = mass after exposure (gram)

                         A = total exposed surface area (in2 or mm2)

                         Δt = total exposure time (hours)

                         ρ = density (g/cm3)

                         K = constant for unit conversion

Answer 2

mpy * years = lost wall thickness in the time period

now go find mpy (mills per year), typically done in the field under actual condition.

Answer 3

While I agree that corrosion can cause a reduction in flow area, it can cause more insidious things to happen.  The two most important are:

1.  Increase in the absolute roughness

2.  Insulating properties of the deposits inhibit heat transfer

The first phenomena listed has a compounding effect.  Increased roughness can cause an otherwise laminar flow piping design to degrade to a point where the flow becomes transitional or even turbulent.  While turbulence is good when you desire mixing of the fluid, a turbulent boundary layer will not only inhibit heat transfer, but will also increase head losses in the system.  If encountered on the suction side, it can cause pump cavitation!

As far as data goes, the absolute roughness is basically the average height of the asperities on the pipe wall, usually in units of inches or millimeters.  All of the tabulated data is empirical (experimental) in nature, so no real theory exists for practical applications.  You may want to try the Engineering Toolbox.  Link is included.

Good Luck!