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Designing an Internal
Corrosion Program
NACE Eastern Area Conference
Roy D. Fultineer Jr.
Introduction
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Plans and Procedures
Training
Know the system
When do we get involved
Understand Corrosion Mechanisms
Identify the right monitoring locations
Monitor and Trend data
Possible Mitigation
Follow-up
Plans and Procedures
• Internal Corrosion Plans
– Generic
• Potential Treats – Acid Gases, Bacteria, Erosion, etc.
• Types of monitoring
– Gas samples
– Liquid samples
– Coupons
• Requirements for internal corrosion monitoring
• Parameters to monitor and trend
Plans and Procedures
• Internal Corrosion Plans
– Generic
• Basic Decision Criteria
– If indications are found, what is the next step.
Plans and Procedures
• Internal Corrosion Plans
– Specific
• Location of facility
• Specific location of monitoring locations
• Specific timing of monitoring
• Specific water control methods
– Pigging
– Drips
– Dehydration
• Schedule of these control methods
• What action has been taken?
Plans and Procedures
• Internal Corrosion Plans
– Specific
• What action is planned?
• How will action be evaluated?
Plans and Procedures
• Procedures
– Procedures go into specific action of how to
conduct sampling and monitoring
– Important aspect of internal corrosion plan
– Procedures go hand-in–hand with training
Training
• Properly trained personnel is critical to the
success of any internal corrosion program
– In house training
– On the job training
– NACE and other professional organizations
• Collecting accurate data is critical
• The better the data, the better the decisions
When do we get involved
• Internal corrosion should be considered in the
initial design phase of any project
• Things to consider:
– Water content and water removal
– Elevation profile
– Inlets and outlets to the system
– Gas Quality
– Flow regimes
Know your system
• Operation Factors
– Direction of flow
– Flow rates
– Flow regime
– Pressures
– Product
– Upsets
– Elevation Profile
Elevation Profile
Understand Corrosion Mechanisms
• Causes
– Water
– CO2 Influenced
– H2S Influenced
– MIC
– O2
– Velocity/Flow Related
Understand Corrosion Mechanisms
• Water
– Necessary for internal corrosion
– Temperature
• Reaction rates double for every 10 degree Celsius rise
– pH
• Less then 5 can result in increased corrosion
– Carbonates
• Acts as a acid buffer
Understand Corrosion Mechanisms
• CO2 Corrosion
– Carbon Dioxide + water = Carbonic Acid
– Carbonic Acid + iron = iron carbonate + hydrogen
– Carbon dioxide is in the gas
– Carbonic acid creates corrosion
– Generally mild corrosion except when with other
corrodents
Understand Corrosion Mechanisms
• H2S Corrosion
– Hydrogen Sulfide + iron + water =
– Iron Sulfide + water + hydrogen
– From sour gas operations or from SRB’s (MIC)
– Corrosion pitting occurs where FeS forms on
the metal
surface and creates a local
corrosion cell
Understand Corrosion Mechanisms
• MIC
– Acid Producers - APB’s
– Sulfate Reducing Bacteria - SRB’s
– Controlled with a clean system and
bacteriacides/biocides
Understand Corrosion Mechanisms
• Oxygen
– Oxygen + iron + water = Iron oxide + water
– Oxygen creates an oxidizing effect and with
other corrodents = accelerated corrosion
– Oxygen concentration cells create corrosion due
to oxygen depletion areas
Understand Corrosion Mechanisms
• Velocity/Flow related attacks
– High surface fluid or particle velocities
– Erosion
• High Energy with or without particles
• Removes metal
• Leaves smooth surface
– Erosion Corrosion
• Erosion removes protective film or scale
• Exposes metal surface to environment
Pick the right monitoring locations
• Representative of system
• Right location
– Know what your looking for and put monitoring
devices in right location.
– Top of the line versus bottom of line corrosion
• Right device
– Pick the monitoring device that is designed for the
application
Monitor and trend data
• Collect the data you need and compare it to all
other data
• Be careful not to add to much weight to any
one data set
• Determine if action is required
Possible Mitigation Methods
• Do nothing
– Sometimes the best answer is to continue to
monitor and study
– More information will lead to better decisions
– More technical or sophisticated analysis may be
appropriate
– Chemicals can actually make the situation worse
Possible Mitigation Methods
• Liquid removal
– Drip Blowing
• Drip should be monitored and blown on frequencies that
ensure no free liquids
• Used to monitor for corrosion parameters
– Pigging
• Ran on frequencies that ensure no free liquids
• Thought should be given to the type of pigs used
• Speed of pigging can influence
Possible Mitigation Methods
• Dehydration
– Removal of water through dehydration can greatly
reduces possibility of internal corrosion
– High initial cost and added O&M cost
– Does not necessarily remove the need for chemical
Possible Mitigation Methods
• Control Inlet Product Quality
– Monitor product quality entering system
– Have control to shut in suppliers
Possible Mitigation Methods
• Chemical Treating
– Batch
– Slug
– Continuous
– Squeeze
Possible Mitigation Methods
• Design
– One of the most effective means of control
• Use of proper materials
• Size pipeline properly (oversized = liquid hold-up)
• Modeling and/or flow regime will dictate location
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and/or need for drips, pigging, etc.
Material selection can be key
– Steel is not always the best solution
– Example: Fiberglass piping in acid gas environment
Follow-up (Did it Work?)
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Coupons
Liquid Sampling
Residuals Monitoring
In Line Inspection (ILI)
Gas Monitoring
Coupons
• Weight Loss
– Compare previous rates to new rates
– Compare pretreated versus post-treatment
– CID – Copper Ion Displacement – monitoring
chemical distribution
Liquid Sampling
• Monitor effects on water chemistry
– pH (increasing or decreasing)
• Increase – Scaling
• Decrease – Corrosion
– Metals (increasing decreasing)
• Mn/Fe ratio
• Trending
– Bacteria levels
Residual Monitoring
• Are chemicals getting where you need them
• Are the residuals adequate
• If not,
– Adjust existing facilities
– Add new injection points
– Change application (continuous to pigging)
ILI Inspection
• Need base line
• Follow-ups
– Monitor corrosion growth
– Monitor for new corrosion.
Gas Monitoring
• Monitor Quality
– CO2
– H2S
– Water
– O2
• Monitor for changes
Questions?