errors in sampling/monitoring in an internal corrosion program
DESCRIPTION
Errors in Sampling/Monitoring in an Internal Corrosion Program. NACE Eastern Area Conference. Goals of Sampling/Monitoring. Identify potentially corrosive species that may be present in a pipeline system Determine corrosion rate Determine effectiveness of mitigation. - PowerPoint PPT PresentationTRANSCRIPT
Lynsay Bensman 06 October 2009
Errors in Sampling/Monitoring in an Internal Corrosion Program
NACE Eastern Area Conference
06 October 2009
2
Goals of Sampling/Monitoring
Identify potentially corrosive species that may be present in a pipeline system
Determine corrosion rate
Determine effectiveness of mitigation
06 October 2009
3
Errors in Sampling/Monitoring
Improper tests or equipment
Choosing the incorrect location
Poor timing
Improper sampling techniques
Improper sample preservation
Misinterpreting results
Missing sampling opportunities
SAFETY
06 October 2009
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Improper Tests or Equipment
Using the wrong equipment for what you are actually trying to test- Monitoring devices
Using a kit that is not the proper range
Using a kit that is expired or not properly working- Check prior to going out in the field
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Monitoring Devices
What are you trying to achieve?
Do you need real time monitoring?
Are you looking for pitting?
Is erosion playing a role in the corrosion process?
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6
Incorrect Sampling/Monitoring Locations
Representative or more severe than the corrosion in the system
Not necessarily- The easiest place- The closest place
Dilution effect
How many locations is enough?
Monitoring in conjunction with mitigation
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Monitoring Locations
Coupons/probes on stick off the top of the pipeline are not exposed to liquids laying alone the bottom of the line
Coupons/probes off the bottom are not in the gas flow but allow liquids to collect if present
Coupons in flow should be as close to the bottom of the pipe as possible
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8
Poor Timing
Liquid sample collection is not likely to yield optimum results- Right after drip blowing or removal from separators
At intervals that makes it difficult to interpret results- Consideration for injection withdrawal cycles- Consideration for chemical treatment
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Improper sampling techniques
Waiting to perform field testing
Performing analyses on samples that do not contain water
Not following instructions
Air
Sample contamination
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Waiting to Perform Field Testing
Reasons- Weather- Time- Training
Ramifications- Some data is unreliable if not collected immediately
- Dissolved gases- pH- Bacteria culture testing
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Air
Sample containers should be as full as possible to prevent reaction with air
Solid samples can react with oxygen in air leading to misidentification
4FeS + 3O2 2Fe2O3 + 4S + heat
Coupons that have been exposed to air should never be re-inserted
06 October 2009
12
Sample Contamination
Liquid Samples- Should not re-use sample bottles- Grabbing a bottle that is just ‘lying around’ - Not rinsing out test kit containers- Sampling from a common tank- Re-using bacteria inoculation syringes
Pipe Samples- External environment
Coupons- Should never install a coupon if it has been dropped on the ground- Need to make sure wearing gloves when handling the coupon- Coupons should not be re-inserted if they have been removed from the system- Coupons should not be analyzed if they have been removed from the system and not
properly stored prior to analysis
06 October 2009
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Bacteria Testing
Perform immediately after sample collection or pipe exposure- Prevent contamination
Serial dilution media should match the salinity of the water present in the pipeline
Should not expel any of the inoculation media
Swabs need to be taken over consistent area size
Proper labeling
06 October 2009
14
Gas Testing
What are you actually testing?
Need to purge sample container or testing container
Some measurements are better performed on-site
Storage containers for gas that may contain H2S
What are on-line instruments monitoring
Do you need to check for O2
06 October 2009
15
Improper Storage of Samples
Samples need to be properly labeled (if further analysis is to be performed)
Liquid samples should be stored in a cool environment until analyzed
Bacteria inoculation vials should be stored at similar temperature to pipeline operating temperature
Ok
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Misinterpreting Results
Garbage In = Garbage Out
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Misinterpreting Results
How do operating conditions affect the results?- Well work- Change in flow direction- Change in flow rate
Iron counts- Iron to Manganese ratios- Correlation to corrosion- Trending
Bacteria
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Misinterpreting Results - Bacteria
Planktonic- Free floating- Liquid sampling
Sessile- Attached to pipe wall- Solids or swab sampling
Correlation to MIC- No known correlation between planktonic bacteria levels and the presence of MIC!!!
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Misinterpreting Results
Do I have enough data to make a decision?- Trending
Do the data make sense?- Is further investigation needed? (e.g., no liquids are recovered from drips but leaks are still
occurring in the system)
Do the data support current monitoring/sampling and mitigation?
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Missing Sampling Opportunities
After pigging operations- Liquids- Solids- Swabs
As pipe is being removed from system- Liquids- Solids- Swabs
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SAFETY
Safety is of primary importance!!!
Sampling is always concern when collecting a sample from a live pipeline system
Questions???- Is there potential for projectiles?- Are isolation valves shut?- Are there concerns for being sprayed with liquids?- Are there any pyrophoric materials present?
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Safeguarding life, property and the environment
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