Version 1 (CORROSION 2010)
A cathodic voltage of –850 mV or more negative across the structure to electrolyte boundary as measured with respect to a saturated copper/copper sulfate (CSE)reference electrode.
COMMENTS
Version 1 is the only technically corrrect version of the 850 criterion. Versions 2,3 and 4 do not eliminate the ambiguity between current-applied and polarized potential critera that the committee was charged to accomplish. Version 5 is better than versions 2, 3 and 4 but it is still technically incorrect because you can not correct for voltage drops by "Determining whether or not there is physical evidence of corrosion".Version 1: What is the definition of Cathodic Voltage? This term does not appear in the SP0169 versions I have.
1. Fails to address IR drop.
Version 1 is from 1969, and is no longer valid for modern pipelines given our understanding of sources of measurement error with well coated pipeliens.
The remaining versions are more or less acceptable, but the wording requires the CP practitioner to 'correct' or 'consider' IR drops. I think this is a messier way to treat the criteria issue, as 'correction' implies some mathematical treatment, and 'consideration' is subject to interpretation.
While I agree Version 1 is technically correct and simple, I think more information is necessary such as in versions 4 and 5.
V1 –agree
Version 1 - cannot measure the potential reasonably as stated.
Version1, is inpractical.
Version 2 (Committee E-mail Suggestion)
(1) A structure-to-electrolyte potential measured with the cathodic protection current applied. The current-applied potential criterion value shall be established by the owner through sound engineering practice and supported by empirical evidence that demonstrates the corrosion control objective of the owner is achieved.(2) A negative polarized potential (see definition in Section 2) of at least 850 mV relative to a saturated copper/copper sulfate reference electrode.
COMMENTS
2. (1) Fails to address IR drop.
2. (2) Is an excellent criteria and scientifically defensible.
Version 2 is most agreeable to me because it allows virtually any empirically supported CP criterion to be used - and it places the burden of proof on the owner. This is consistent with CSA OCC-1.
I really like Ver.2. It is concise and well written. However I can see some pipelines owners/operators trying to abuse of criterion #1.Maybe NACE should emphasize that the owner shall used proper skilled and trained personnel in the CP area. And that the effectiveness of the current-applied potential criterion value selected will be owner responsibility only.
Should have been maybe added to the choices. I hate to be like the ones that vote yes but i want some changes made. Version #2 and #3 are not bad but could not vote for them as they are written. Thanks for going the extra mile to make it right. I would like to be alble to support it this time.
V2,3,4 – disagree
Version 2 - This is a start, but needs more information for ON. Why would the polarized not have to meet the corrosion control objectives of the owner?
Version 2 would be a nightmare to comply and enforce.
Version 2, To what detail the Empirical evidence needs to be supported? Sometimes a collection of all data, ie, leak survey, cp reads and history, all taken together will suffice. The devil is in the detail.
In version 2 the use of empirical evidence is too broad and therefore is not as helpful/informative as the other options.
Version 3 (RP0169-1969)
(1) A negative (cathodic) voltage of at least 0.85 volt as measured between the structure surface and a saturated copper-copper sulfate half cell contacting the electrolyte. Determination of this voltage is to be made with the protective current applied. The Corrosion Engineer shall consider voltage (IR) drops other than those across the structure-electrolyte boundary for valid interpretation of the voltage measurement.
(2) A negative polarized potential (see definition in Section 2) of at least 850 mV relative to a saturated copper/copper sulfate reference electrode.
COMMENTS
Version 3 would have been my top selection but I do not like that they have used the title "Corrosion Engineer". It should read "Responsible Corrosion Person". I do not like that they specified that a Corrosion Engineer should make the determination. I have met several Corrosion Engineers that I was amazed how little they understood about CP. Conversely, I have met many Corrosion Technicians that put these engineers to shame. I would vote yes on version 3 if the term "Corrosion Engineer" were replaced with "Responsible Corrosion Person" or something similar.
Since Corrosion Engineer is capitalized in the wording I presume that means NACE certified corrosion engineer.
Sentence 2 of version 3 contains the destination of a Corrosion Engineer as the one to consider voltage drop. Is that on purpose or are other professionals able to "consider" voltage drop?
I would vote for version 3 and strongly agree with it if the destination of "Corrosion Engineer" was changed to reflect field personnel. This seems to say that a person with even as high as a CP3 certification is not qualified to consider voltage drop and we must consult a corrosion engineer to get IR drop measurements.
Version 3 - Rephrase to take corrosion engineer out. There is no definition for this professional in many countries. A technician or any other qualified person can make this consideration. 3 and 4 with affirmative with comments.
V3 could be improved by deleting the second sentence and add "with IR drop considered" to the end of the first sentence.
Version 3 - Does not give guidance as to ways to consider IR drop.
Version 4 (SP0169-2007)
(1) A negative (cathodic) voltage of at least 0.85 volt as measured between the structure surface and a saturated copper-copper sulfate half cell contacting the electrolyte. Determination of this voltage is to be made with the protective current applied. The Corrosion Engineer shall consider voltage (IR) drops other than those across the structure-electrolyte boundary for valid interpretation of the voltage measurement. NOTE: Consideration is understood to mean the application of sound engineering practice in determining the significance of voltage drops by methods such as:
• Measuring or calculating the voltage drop(s);
• Reviewing the historical performance of the CP system;
• Evaluating the physical and electrical characteristics of the pipe and its environment; and
• Determining whether or not there is physical evidence of corrosion.
(2) A negative polarized potential (see definition in Section 2) of at least 850 mV relative to a saturated copper/copper sulfate reference electrode.
COMMENTS
Version 4: Just the (2)Version 4 appears to leave Section 6 of the SP 0169 standard as is. I am in favor of this not only for the referenced criteria but for the section as a whole. Please see my detailed response for all the issues of concern within Section 6 provided during the last round of voting.
I like Version 4 but prefer using the .850 volt designation instead of 850 mV.
As no criteria can or should be an "absolute" for all situations, NACE should provide the best practical advice for an owner/operator to follow. I believe Version 4 accomplishes this and allows for good engineering practice to evaluate many highly variable environmental and field specific situations.
4. (1) Fails to define "considered" at all and thus is not scientifically defensible.
I feel that both the "CP On" and the "Polarized potential" should be in there own statements. I also like that in the Version 4 some guideance is given in "what must be considered for valid voltage drops"
Please consider the physical and electrical characteristics of the pipes coating in version #4.
In Version #4, bullet #3 the word pipe needs to be changed to structure.
In version 4 the integrity of application of the On criterion puts the emphasis squarely on the company's procedure. The proper aplication of a proper procedure is the key to any criterion, CP is no exception.
Version 4 I agree with the following reservation. With the current IMP regulations in the U.S. there is much useful data with regards to corrosion coming from metal loss smart pig runs. We should take advantage of this information when making decisions regarding "physical evidence of corrosion". I would suggest this data can be used to fulfill this caveat in Version 4.
Version 4 is a soft option for poorly designed systems. It is possible as it specifically draws the users attention to the issues required for consideration.
Version 4 - I would remove "Reviewing the historical performance of the CP system". This will be interpretated as a leak detection criteria that is really dangerous.
I would prefer to leave the criteria section the same as the current version - I believe that is V4.
Version 4 appears to leave Section 6 of the SP 0169 standard as is. I am in favor of this not only for the referenced criteria but for the section as a whole.
Version 4 - This version gives some guidance as to how to consider IR drop
Version 4 of the criteria represents no change from the existing standard SP0169 with regard to the -0.850 V criteria and I am in agreement with leaving Section 6 as currently written.
As stated above, cosideration of cathodic protection is already appropriately addressed in the existing standard. Version 4 appears to make no chage to the existing standard.
There should be a maybe. With some enhancement I could vote yes for version 2. Version 4 I could compromise and vote yes for it. Thanks for asking!
Version 4 appears to provide the broadest range of options, and provides detail regarding the interpretation of the work consider. It also recognizes the application of the polarized criteria.
Versions 4 and 5 are the most informative in my opinon.
Version 4 best represents my view.
Version 5 (current draft)
A cathodic voltage of –850 mV or more negative as measured with respect to a saturated copper/copper sulfate (CSE) reference electrode. This potential may be either a direct measurement of the instant-off potential, or a current-applied potential. Interpretation of a current-applied measurement requires correction for voltage drops in the earth or metallic paths.
NOTE: Correction is understood to mean the application of sound engineering practice in the determination of the magnitude and significance of voltage drops by methods such as:
• Measuring or calculating the voltage drop(s); or
• Determining whether or not there is physical evidence of corrosion.
COMMENTS
Version 5: What is the definition of Cathodic Voltage?5. First bullet: A scientific method of "calculating the voltage drop(s)" must be provided. Second bullet: There is no practical method of "Determining whether or not there is physical evidence of corrosion".
Version 5 would be better if instant-off was changed to polarized.
To much can be miss understood with the On and Off criteria in version 5. Regulators can go off in a tangent and require the Off potential.
Version 5 would be "neutral" & "yes" if "correction" was changed to "consideration".
We've got to stay with the word "considered" and stay away from "corrected". No way on Version 5.
Version 5 - Correction means off potential. There is no other way. "Determining whether or not there is physical evidence of corrosion" does not mean correction. Ohmic drop can be big, but soil corrosion rate is negligible.
V5 - neutral
Version 5 - basically the same as the polarized potential since you must "correct" for IR drop.
I favour somewhere between versions 4 and 5 such as version 5 with the 4 points itemized in version 4. The other 3 versions can only be valid if they have been validated at leats once using my modification of version 5 suggested above. That being said then version 5 is the most acceptable. In version 5 we do not feel we can support the term corrected at this time.
Other Comments (General):
Part of your problem is wording. How many ways can you basically say the same thing. It seems you are just word-smithing to cover all the bases. Say it one way and let that be it - don't confuse people. For instance the first sentence in item (1) for each version. Look at the different ways you say the same thing.This doesnt seem like a fair poll. Did everyone on the TG agree with this, or just a few individuals?
need to omit having two criteria that both say 850 is the magic number but each 850 is defined differental, this can not be correct. Just state control is achieved at some degree of polarization depending on environmental conditions... (period)
I agree with all so interpret the rankings as 1 = least prefer to 5 = most prefer
IN GENERAL: there is not even one of the proposals strongly asking for the negative polarized potentials as only possibility (of course including also the 100 mV of cathodic polarization). This will be the criterion that I will vote for. Meanwhile we are giving the chance for interpretations of the measured values beyond the simple measurement, people can use these
interpretations to their convinience.
Can only do the first part, not the second part.
Voltage applied - can do.
Voltage off - no can do
All of the above criteria are meaningless unless the temperature of the reference electrode is specified.
Guidance for correction of the reference electrode potential given elsewhere in previous drafts gave method for this correction but did not give a temperature that the potentials should be corrected to.
Why not simply define "polarzed potential" as:
Polarized Potential = A pipe-to-soil potential (excluding all IR or other possible sources of error in the measurement) more negative than -850 mV CSE.
Then the criteria becomes:
Protection is determined by demonstrating a polarized potential of more negative than -850 mV CSE.
Note that I used one choice for each ranking and didn't repeat any of them.
It seems to me that potential readings are essentially a conservative way of being reasonably confident about the structural integrity of a pipe without seeing it or otherwise testing it. It seems there should be an alternative such as sufficient visual inspection or testing that adequately proves there is no damage of sufficient size to compromise the structural integrity of the pipe before the next inspection or test. This alternative would say that any level of cathodic protection, or even leaving off cp, is adequate since service life can be safely
anticipated.
Over the years, on pipeline systems that I maintain, I have come to find that as long as there are no foreign cathodically protected structures in the near vicinity that the negative 850 millivolt "on potential" will result in a greater than 100 millivolt shift in cathodic protection current. This has been substantiated with many miles of close interval survey data. I have maintained lines in several of the western states and this has been true on all that I have been in charge of. Foreign cathodically protected structures nearby to my structures have been a concern due to interferance and groundbed gradients.
I strongly disagree with all statements as presented and believe the move should be made completely away from voltage potential measurements for "protective criteria". We all understand that -850 mV does not work in all cases and in fact we should be further focusing on applied current to prove that in fact we are protecting a structure. In the past voltage potential was an easy available way to prvide some proof that current might flow to the structure (emphasis on the might) and was in no way meant to be what it is today. Methods of measuring current (not voltage) must be included in criteria today. Once it can be demonstrated that current is in fact flowing to the structure, then a voltage potential measurement can be useful in montioring the situation. A voltage potential by itself can mean nothing at times without knowing about the current flow.
I'm not sure why the negative comments aren't being looked at. This seems like a way to push through a change that isn't wanted. Can you please add teh poll question: Do you feel additional requirements to SP0169 are being pushed by people who would profit from the changes? Do you feel this is right?
Please see my detailed response provided in the last round of voting that details the rationale for the negative response. I would vote affirmatively only if all the issues identified in my negative response were addressed appropriately. Version 4 of the criteria represents no change from the existing standard approved SP0169 standard with regard to the -0.850 V criteria and I am in agreement with leaving Section 6 as is.
Any criteria that is published must be based in the scientific method. Otherwise, failures will result and damage infrastructure, lives, and the reputation of NACE and our engineers.
Alterntaly why not adopt criteria given in ISO 15589-1 that is
(a) Protection potential applies at the metal/electrolyte interface, i.e. a potential which is free from the IR drop in the corrosive environment (IR-free potential)
(b) Prtoection potential is dependent on soil type / resistivity, as follows:
anerobic conditions or < -950 mV high resisitivty soils (10 to 100 kohm.cm) -750 mV very high resisitivty soils (> 100 kohm.cm) -650 mV
As you mentioned the wording of the above can be changed. So actually an affirmative volt depends on the wording. The no's on this questions is a maybe depending on the wording, but you did not give that choise.
My company, one of the largest energy transmission companies in North America, will continue to use the -850 polarized OFF potential regardless of how weakened the standard becomes through the lobbying efforts of certain individuals.
In canada, we are entitled to use alternate criteria where we can demonstrate the objective of corrosion prevention has been achieved (but we need to support it empirically).
To reiterate my position, voltage potential by itself should not be allowed as a criteria. One must prove out the current flow in the system and that it is in fact enough current to the steel to be cathodically protective. Until that occurs, voltage potential is only a hopeful way of measuring what might occur. I know some may think this is radical but today's technology (along with older technology) allows one to measure direct current on a pipeline (both through direct measurements and measurements from above the ground without touching the pipeline). Until NACE members recognize the failure of a voltage only criteria, we will not make progress in our world of cathodic protection. We must start measuring current again to prove if a structure is cathodically protection.
The format and content of this poll is a waste of time. If SurveyMonkey and hence NACE thinks that this survey "Surveys Made Simple" then this is all monkey business and belongs in a zoo. And, we need to rethink about NACE leadership qualifications and where it is taking us. This poll is worthless.
It is my opinion that the existing version of Section 6 of SP 0169 adequately addresses cathodic protection measurement and interpretation.
While I am not sure that we need to eliminate current applied measurements, I think the format presented actually would encourage that.
