Saturday, March 6, 2010

Comments from Jeffrey Pollack

I would like to submit my opinions on the pending revisions to SPO169 before the March 12th deadline. My comments will only pertain to Section 6 that deals with Criteria and Other Considerations for CP, since this seems to be the most contentious issue amongst the respondents. Reading the blog discourse is interesting, but it would be more valuable if the balloting rules compelled the folks who are voting “Yes” to also submit some commentary in support of their position. This would allow for a more diverse range of opinions to be expressed. Myself, I have cast a “Yes” vote in favor of the proposed changes, even though I can list a number of reasons to vote against the amendments. I guess this means that we have some sound science before us when we can have a near 50 / 50 split on the first ballot.
First, to state (and restate) some of the legitimately negative aspects of SPO169:
• Excessive polarization of steel structures coated with epoxy and other high density coatings can result in blistering of these coatings due to limited gas permeability when atomic hydrogen evolves out of steel that is protected by impressed current CP. This blistering can create areas on the surface of the structure that are effectively “shielded” from adequate CP due to the disbonding of the coating.
• Excessive polarization can result in cracking failures of high tensile strength steels from HIC and embrittlement. This could become a greater problem as industry increasingly moves towards the use of thinner wall steel pipe, of grades above API - X60.
• Interference problems will be exacerbated between adjacent operating companies in common rights of way where each operator tries to maintain differing levels of polarization.
• Operators and distribution companies that utilize galvanic and passive CP systems without shunted measuring stations will find it difficult to comply with requirements for IR correction.
• Operators will incur greater capital costs trying to achieve a higher threshold of compliance.
Secondly, to state some of the positive attributes and outcomes if SPO169 is adopted:
• There is nothing in the revised language of SPO169 that prohibits operators from using the methods and protocols for compliance that they currently employ, as long as they can document and substantiate that their methods are technically valid.
• Paragraphs 6.2.3.1.1 and 6.2.3.1.3 state that operators can utilize “ON” or “OFF” potential measurements, and that -850mv “ON” readings are acceptable, as long as the operator can demonstrate that valid techniques have been employed when accounting for voltage drops.
• Section 6, Paragraph 6.2.3.2.5 makes appropriate allowances for maintaining polarization levels more positive than -850mv in environments with higher soil resistivity’s.
• Paragraph 6.2.3.2.9 attempts to move polarized potentials out of the SCC susceptibility range of -575mv to -675mv @ operating temperatures of approximately 65°F.
• The emphasis on IR correction / voltage drops will force operators to acknowledge the impossibility of obtaining accurate p/s potentials when taking readings in proximity to linear anode systems, and within the voltage gradients of anodebeds, without the benefit of interrupting the primary current sources that are polarizing the structure that is being tested.
• Current interruption is a panacea for discovery of interference issues and isolation problems with other adjacent utilities and operators, that would have otherwise, gone on undetected.
• When current interruption is utilized during annual survey, and interference / isolation problems are discovered, 50% of standard interference testing protocol has already been satisfied in the act of obtaining p/s potentials on the operator’s facilities, as well as on the “foreign” utility.
• Absent the ability to obtain polarized potentials of -850mv “OFF”, operators will increasingly utilize 100mv criterion to demonstrate compliance. This will compel operators to perform native state / depolarization surveys. These surveys will yield valuable information about the condition of their coatings, and will define areas where stray current interference is a potential problem.
• Instrumentation is presently available that allows us to geo-synchronously interrupt all of our rectifiers. We have hand held data collectors that allow us to generate DC waveforms so we can verify uniform interruption. Those same data collectors can be set to capture “instant OFF” readings at any point in the “OFF” window, while avoiding the adverse effects of anodic spiking.
• There is a good article of reference from MP Magazine by Mark Mateer of Shell Pipeline, dated September of 2004. This document explains the use of Failure Probability Plots to evaluate the effectiveness of “OFF” vs. “ON” potential, CP criteria. It makes a compelling argument for the superiority of “OFF” criteria in the reduction of failures and leaks over time.
The word empirical is used three times in Section 6 of the SPO169 document. I think this word is the basis of the standard that this document attempts to achieve. Empirical is the opposite of anecdotal, and much of the arguments that have been offered in defense of the “NO” votes have been anecdotal. Empirical evidence is the only thing that will stand up when our data is challenged during an audit with regulatory agencies. Saying that methods that we have used for the past 40 years have been sufficient will not hold water after we have experienced a failure. Stating that costs are an insurmountable obstacle for us in our pursuit of compliance will not have any credence when this logic is challenged with the necessity for public safety.
There has been a lot of talk about our inability to identify and achieve that perfect “sweet spot” of optimum compliance. That “sweet spot” is a dynamic target that we may have to recalibrate for many times. In the end it is incumbent upon us stakeholders in this industry to be able to employ sound engineering practices that we can defend, and demonstrate proficiency at our craft.


Jeffrey Pollack Sr. Integrity Specialist Williams – NW Pipeline

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