Errors in Sampling/Monitoring in an Internal Corrosion Program

1. Errors in Sampling/Monitoring in an Internal Corrosion Program NACE Eastern Area Conference

2. Goals of Sampling/Monitoring • Identify potentially corrosive species that may be present in a pipeline system • Determine corrosion rate • Determine effectiveness of mitigation

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

4. 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

5. 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?

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

7. 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

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

9. Improper sampling techniques • Waiting to perform field testing • Performing analyses on samples that do not contain water • Not following instructions • Air • Sample contamination

10. Waiting to Perform Field Testing • Reasons • Weather • Time • Training • Ramifications • Some data is unreliable if not collected immediately • Dissolved gases • pH • Bacteria culture testing

11. 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

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

13. 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

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

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

16. Misinterpreting Results • Garbage In = Garbage Out

17. 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

18. 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!!!

19. 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?

20. Missing Sampling Opportunities • After pigging operations • Liquids • Solids • Swabs • As pipe is being removed from system • Liquids • Solids • Swabs

21. 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?

22. Safeguarding life, property and the environment www.dnv.com