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FAC in oxgenated environment
- Thread starter maxer64
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How? I have seen FAC for a boiler that has been converted to OT (oxygenated treatment). The typical location for FAC was within the deareator vessel itself (where oxygen and other gases are removed within the deareator) and oxygen is added downstream. We are evaluating replacing the deareator vessel with feedwater heaters because this is a once-through unit with polishers.
EdStainless
Materials
FAC hinges on two issues
The shear at the surface due to local flow velocity;
and how robust the surface film is.
Of course the flow shear is much greater in turbulent two phase flows, but even in single phase it can be rather high.
The surface film is dictated by more than just oxygenation. The pH, temperature and other species in the water can have a strong influence on the composition and morphology of the film. Just having plenty of oxygen does not assure that you will have the strongest surface films.
Carbon steels with little or no Cr can be very sensitive to this.
Metengr, your concept in in line with best practices these days. Many plants with DA between the LP FWHs and the HPs are running them differently than they used to. Your condenser should be your primary control on dissolved gasses and oxygen content in an OT system.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
The shear at the surface due to local flow velocity;
and how robust the surface film is.
Of course the flow shear is much greater in turbulent two phase flows, but even in single phase it can be rather high.
The surface film is dictated by more than just oxygenation. The pH, temperature and other species in the water can have a strong influence on the composition and morphology of the film. Just having plenty of oxygen does not assure that you will have the strongest surface films.
Carbon steels with little or no Cr can be very sensitive to this.
Metengr, your concept in in line with best practices these days. Many plants with DA between the LP FWHs and the HPs are running them differently than they used to. Your condenser should be your primary control on dissolved gasses and oxygen content in an OT system.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
Corrosion Vol 63, (8), 2007 pp770-780
In an oxygenated environment, FAC should be reduced but not eliminated as the factors outlined by Ed (who may have read the same paper) are still present.
Steve Jones
Materials & Corrosion Engineer
In an oxygenated environment, FAC should be reduced but not eliminated as the factors outlined by Ed (who may have read the same paper) are still present.
Steve Jones
Materials & Corrosion Engineer
WHAT IS FLOW ACCELERATED CORROSION?
Flow accelerated corrosion (FAC) may be defined as a process whereby a normally protective oxide coating dissolves into a rapidly moving water, or a water/steam mixture.? In the case of plain carbon steels, this process occurs under very specific, well-defined environmental parameters. Principal among these parameters are temperature, pH, oxygen content, and water velocity.
i suggest u to read this article. i think you can also dowload it from NACE:
98721 FLOW ACCELERATED CORROSION
S
Corrosion Prevention & Corrosion Control
Flow accelerated corrosion (FAC) may be defined as a process whereby a normally protective oxide coating dissolves into a rapidly moving water, or a water/steam mixture.? In the case of plain carbon steels, this process occurs under very specific, well-defined environmental parameters. Principal among these parameters are temperature, pH, oxygen content, and water velocity.
i suggest u to read this article. i think you can also dowload it from NACE:
98721 FLOW ACCELERATED CORROSION
S
Corrosion Prevention & Corrosion Control
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