Erosion Vs Corrosion

[chimieindustrielle]

Dear friends ;

I'm wondering if anyone could explain what's the difference between erosion and corrosion in a pipeline ?

I'm wondering also if the erosion occurs when we have two phase fluid or it can occur when we have one phase fluid (

liquid for example ) ?

Thanks a lot !


Regards !

 

[bimr]

Erosion corrosion is generally related to high velocity of fluids. See the paper:

http://gekengineering.com/Downloads/Free_Downloads/Corrosion_Overview.pdf

 

[chimieindustrielle]

Dear BIMR ;
In this article they said in page 38

Erosion - All Liquid Flow
• Described by API Equation 14E
Vc = C (density)1/2
where: Vc = critical flow velocity, ft/sec
density = fluid density in g/cc
C = 100 for long life projects
C = 150 for short life project
C = >200 for peak flows

But Aas I read the API 14 E , they just talk about erosional velocity for liquid / gas mixture

 

[LittleInch]

Erosion is the wearing away of the pipe material by means of particles in the fluid (gas, liquid or two phase) due to abrasion.

Tends to only occur in lines with particles (dirt) at high valocities. The API 14E equation is widely recognized as being highly conservative and the C factor difficult to evaluate, but goives you some idea of whther it is a problem or not.

Corrosion on the other hand is a chemical reaction between a substance in the fluid and the pipe material which results in the pipe material being essentially dissolved over time. Temperature can have a big effect as well as the concentration of the chemical substance.

This all sounds very basic....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[moltenmetal]

The two processes can be combined. There is such a thing as erosion-corrosion, where the passive layer of the metal is stripped away by erosion faster than it can be chemically re-formed, leading to rapid corrosion failure of the parent metal. The classic example is concentrated sulphuric acid on carbon steel, where a passive layer of iron sulphate forms but which can be stripped away leading to RAPID corrosion by local areas of even very modest fluid velocity.

As LittleInch correctly states, erosion by clean fluids rather than slurries, at velocities anywhere nearly economic in piping, is pretty much a figment of imagination rather than a real problem- until you get into very long design lives. If clean fluid erosion were a real problem, most control valve trims or pump impellers wouldn't last a month.

 

[bimr]

Yes, erosion occurs with gas, liquid or two phase due to abrasion.

 

[chimieindustrielle]

Dear friends
thanks a lot for your replies!

I'd like to add that my fluid stream is DIESEL

 

[LittleInch]

Then you shouldn't have either as an issue unless you've got a lot of water in your diesel.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.