Richard,
I totally agree with you and I feel that 0.850 V "ON" criteria has proven to be good enough for many years...
But if they refuse to accept the 0.850 V "ON" criteria anymore for whatever reason, has anyone thought about just increasing the ON potential up to maybe 0.950 or even 1.000 V "ON" to add additional protection yet not requiring as much additional labor/expense?
This might be an acceptable option or also worth evaluating...
Monday, February 8, 2010
Comments from Paul Nichols
Richard,
Of course you know there is nothing to prevent someone from using -850 mV On now, if the data is available to support that it is effective. SP0169 permits it, it just takes a bit of work, like collecting the data you ask for in your note. A combination of operator data on soil, coating and CP conditions, some ECDA and/or ILI data, plus the previous PRCI study would be sufficient to show if -850 On is effective. I think the same sort of, or substantially similar, data would be required anyway even in a revised SP0169; some data to show that the conditions are appropriate for -850 On and to show that it works.
Regards,
Paul
Paul Nichols
Senior Materials and Corrosion Engineer; Mechanical, Materials and Integrity - East
Projects and Engineering Services
Shell Projects and Technology
Of course you know there is nothing to prevent someone from using -850 mV On now, if the data is available to support that it is effective. SP0169 permits it, it just takes a bit of work, like collecting the data you ask for in your note. A combination of operator data on soil, coating and CP conditions, some ECDA and/or ILI data, plus the previous PRCI study would be sufficient to show if -850 On is effective. I think the same sort of, or substantially similar, data would be required anyway even in a revised SP0169; some data to show that the conditions are appropriate for -850 On and to show that it works.
Regards,
Paul
Paul Nichols
Senior Materials and Corrosion Engineer; Mechanical, Materials and Integrity - East
Projects and Engineering Services
Shell Projects and Technology
Sunday, February 7, 2010
Message from Jim Chmilar
Richard: I would like to thank you for your contribution in submitting comments for the STG 35 Ballot last August in the review of the TG 360 revision of SP0169-2007. I know you are aware that the ballot did not get the 2/3rd affirmative vote necessary to proceed and the document was sent back to the task group for revision. I believe that your comments along with the others have now been reviewed and discussed and revisions have been made during at least one of the SIX web-conference call meetings held by the task group members since CTW 2009 (in addition to many e-mail exchanges).
The task group is down to making the final revisions and we will hopefully be out for a four week ballot period during February with a ballot close before San Antonio so we can be discussing ballots results at the Tuesday March 16, 2010 TG 360 meeting.
I trust you will find your comments and views have been addressed in the ballot draft when it comes out. Be assured that if you have any comments or concerns about the document that your negative or affirmative vote will be addressed during Corrosion 2010 or following meeting(s) if necessary. Please consider that if you do submit a negative vote that you must provide a suggested resolution that can be printed in the document, a number of negative voters did not do this last time.
Thank you for your contribution to technical committee activities
Jim Chmilar
The task group is down to making the final revisions and we will hopefully be out for a four week ballot period during February with a ballot close before San Antonio so we can be discussing ballots results at the Tuesday March 16, 2010 TG 360 meeting.
I trust you will find your comments and views have been addressed in the ballot draft when it comes out. Be assured that if you have any comments or concerns about the document that your negative or affirmative vote will be addressed during Corrosion 2010 or following meeting(s) if necessary. Please consider that if you do submit a negative vote that you must provide a suggested resolution that can be printed in the document, a number of negative voters did not do this last time.
Thank you for your contribution to technical committee activities
Jim Chmilar
Comments from Jim Jenkins
Richard:
In addition to all of your comments, most of which I agree with, any potential measurement using a reference electrode where the absolute potential is to be determined needs to include the temperature of the reference electrode at the time of measurement. This is a bigger problem for the Cu/CuSO, than for the Ag/AgCl reference, but is a problem for both. In fact, I actually made the statement at an early RP-0169 revision meeting that "any absolute potential reading using a reference electrode where the temperature of the reference electrode is unknown is meaningless". I don't even think that using a reference electrode for potential rise or decay is valid unless the temperature of the reference electrode is known, or known not to change significantly during the measurement.
I hate zinc reference electrodes as I have found that the potential of even a freshly polished zinc reference can vary on soil by over 200 mV. It is closer for a freshly polished zinc reference in seawater ( about -1.05 V vs Ag/AgCl ) but the main problem in seawater is that the zinc always becomes more electropositive which indicates a more protected potential than would be measured when using a real reference electrode such as an Ag/AgCl. I am currently working on a project where using a zinc reference (even after I warned the owner that this is not satisfactory) to monitor a C.P. system has resulted in several millions of dollars of damage to a marine structure. Why risk structural integrity to save $ 100.00 on a reference electrode?
I plan to remain a voice in the wilderness on this and will continue to vote negative on SP-0169 until this is included. I have given my comments to NACE previously on this with my negative vote with no success.
Jim Jenkins
In addition to all of your comments, most of which I agree with, any potential measurement using a reference electrode where the absolute potential is to be determined needs to include the temperature of the reference electrode at the time of measurement. This is a bigger problem for the Cu/CuSO, than for the Ag/AgCl reference, but is a problem for both. In fact, I actually made the statement at an early RP-0169 revision meeting that "any absolute potential reading using a reference electrode where the temperature of the reference electrode is unknown is meaningless". I don't even think that using a reference electrode for potential rise or decay is valid unless the temperature of the reference electrode is known, or known not to change significantly during the measurement.
I hate zinc reference electrodes as I have found that the potential of even a freshly polished zinc reference can vary on soil by over 200 mV. It is closer for a freshly polished zinc reference in seawater ( about -1.05 V vs Ag/AgCl ) but the main problem in seawater is that the zinc always becomes more electropositive which indicates a more protected potential than would be measured when using a real reference electrode such as an Ag/AgCl. I am currently working on a project where using a zinc reference (even after I warned the owner that this is not satisfactory) to monitor a C.P. system has resulted in several millions of dollars of damage to a marine structure. Why risk structural integrity to save $ 100.00 on a reference electrode?
I plan to remain a voice in the wilderness on this and will continue to vote negative on SP-0169 until this is included. I have given my comments to NACE previously on this with my negative vote with no success.
Jim Jenkins
Friday, January 1, 2010
DEADLINE EXTENSION - PLEASE RESPOND - TG 020 Ballot
For those of you who signed up to vote on the proposed revision of the "NACE Standard TM0497-2002 - Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems" the deadline for voting has been extended to January 11, 2010. NACE has not received the 50% response from the STG voters necessary to close this TG 020 Ballot.
Please respond to the ballot if you have not. I have attached my negative response below.
COMMENTS ON SPO497 REVISION
Forward
Third Paragraph - Second Sentence
It includes methods for voltage drop considerations when pipe-to-electrolyte potential measurements are made and provides guidance to prevent minimize incorrect data from being collected and used.
Change “prevent” to “minimize”. This document can not prevent someone from taking incorrect data, but if followed, can minimize the problem.
Definitions
Coating: A liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film.
Definition needs to be changed to below since pipeline coatings are much more than the proposed definition.
Coating: (1) A liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film; (2) (in a more general sense) a thin layer of solid material on a surface that provides improved protective, decorative, or functional properties. For the purposes of this standard, “Coating” is defined as an electrically insulating material applied to the surface of a metallic structure that provides an adherent film which protects a metallic structure from the surrounding electrolyte.
Section 4: Instrumentation and Measurement Guidelines
4.1 Valid cCathodic protection electrical measurements require proper selection and use of instruments. Pipe-to-electrolyte potential, voltage drop, potential difference, and similar measurements require instruments that have appropriate voltage ranges. The user should must know the capabilities and limitations of the equipment, follow the manufacturer’s instruction manual, and be skilled in the use of electrical instruments.
Change second sentence to read –
The user should must know or be directed by someone who knows the capabilities and limitations of the equipment, follow the manufacturer’s instruction manual, and be skilled in the use of electrical instruments.
Reason: Someone just starting in CP work will need to be under the direction of someone who is experienced in the use of these instruments.
4.3.1 To measure pipe-to-electrolyte potentials accurately, a digital voltmeter must have a high input impedance (high internal resistance, for an analog instrument) compared with the total resistance of the measurement circuit.
To what “accuracy” do we make these measurements? Delete the word “accurately” unless the level of accuracy is defined.
4.3.1.1 An input impedance of 10 MΩ or more should be sufficient for a digital meter. An instrument with a lower input impedance may produce valid data if circuit contact errors are considered. One means of making accurate measurements is to use a potentiometer circuit in an analog meter.
Delete the second and third sentence. The first sentence is all that is needed. The rest is confusing and would need much more detail.
4.3.2 Some analog-to-digital converters used in digital and data logging instruments operate so fast that the instrument may indicate only a portion of the input waveform and thus provide incorrect voltage indications.
Why include such meters if they are incorrect? Delete this sentence and all other references to these type meters or add more definition to clarify which instruments are not acceptable.
4.3.3 Parallax errors on an analog instrument can be minimized by viewing the needle perpendicular to the face of the instrument on the centerline projected from the needle point.
Define “Parallax”.
4.3.4 The accuracy of potential measurements should be verified by using an instrument having two or more input impedances (internal resistance, for analog instruments) and comparing potential values measured using different input impedances. If the measured values are virtually the same, the accuracy is acceptable. Corrections need to be made if measured values are not virtually identical. Digital voltmeters that have a constant input impedance do not indicate a measurement error by changing voltage ranges. An alternative is to use a meter with a potentiometer circuit.
In 4.3.1.1 indicates if a digital meter of 10 MΩ of impedance or more is used, then this should not be a problem for digital meters. Why complicate the matter. 4.4 tells how to check for the accuracy of the meter.
Information like this if needed should be placed in Appendix.
5.5 A pipe-to-electrolyte potential is measured using a DC voltmeter having an appropriate input impedance (or internal resistance, for an analog instrument), voltage range(s), test leads, and a stable reference electrode, such as a saturated copper/copper sulfate (CSE), silver/silver chloride (Ag/AgCl), or saturated potassium chloride (KCl) calomel reference electrode (SCE). The CSE is usually used for measurements when the electrolyte is soil or fresh water and less often for salt water. When a CSE is used in a high-chloride environment, the stability (lack of contamination) of the CSE must be determined before the readings may be considered valid. The Ag/AgCl reference electrode is usually used in seawater environments. The saturated KCl calomel electrode is used more often for laboratory work. However, more rugged, polymer body, gel- filled saturated KCl calomel electrodes are available, though modifications may be necessary to increase contact area with the environment.
Where is the reference for zinc? Some still use zinc for reference electrodes and we teach it in the CP classes. We should have guidance in this document for zinc also.
5.7 Valid The pipe-to-electrolyte potential measurement of a buried pipe should be are made with the reference electrode placed close to the metal/electrolyte interface of the pipe. The common practice, however, is to place the reference electrode as close to the pipe as practicable, which is usually at the surface of the earth above the centerline of the pipe. (See Figure 1[a].) This measurement includes a combination of the voltage drops associated with the:
Change last sentence:
This measurement includes, but is not limited to, a combination of voltage drops associated with the:
Reasoning: There could be other possible voltage drops that may affect these potential readings such as contact resistant of reference electrode contact to the electrolyte, etc.
5.8 The pipe-to-electrolyte potential measurement as described above is a resultant of the:
(a) Voltage drop created by current flowing through the electrical resistances of the items listed in Paragraph 5.7; and
(b) For coated pipe, the influence of coating holidays, depending on their location, number, and size.
Remove part “b”. We have already mentioned that coating has an affect on the reading. The holidays in the coating are part of the circuit, but there are many others that also affect it. Do we list all of them? If needed make a separate section or add it to the 7.1.4 section. Make one statement:
5.8 The pipe-to-electrolyte potential measurement as described above is a result of the voltage drop created by current flowing through the electrical resistances of the items listed in Paragraph 5.7.
5.9 (d) Parallel coated pipelines, electrically connected and polarized to different potentials;
Restate:
(d) Parallel pipelines (coated or bare) and other metal structures, electrically connected and polarized to different potentials;
Reasoning; All metal structures connected to the circuit will affect the potentials.
(i) Unknown, inaccessible, or direct connected galvanic anodes;
Restate;
(i) Galvanic anodes, known or unknown, connected to the pipe;
Reasoning; Galvanic anodes are going to affect the potentials whether they are known or not and whether they are inaccessible or direct connected.
5.10 Voltage drops other than those across the pipe metal/electrolyte interface shall be considered for valid interpretation of pipe-to-electrolyte voltage measurements made to satisfy a criterion. Measurement errors should must be minimized to ensure reliable pipe-to-electrolyte potential measurements.
Reword or remove the last sentence. The first sentence should be sufficient since we say the voltage drops shall be considered.
5.12 When voltage drops have been evaluated at a test location and the pipe-to-electrolyte potential found to be satisfactory, the ―on‖ pipe-to-electrolyte potential value may be used for monitoring until significant environmental, structural, or cathodic protection system parameters change.
5.12.1 Significant environmental, structural, or cathodic protection system parameter changes may include:
(a) Replacement or addition of piping;
(b) Addition, relocation, or deterioration of cathodic protection systems;
(c) Failure of electrical isolating devices;
(d) Effectiveness of coatings; and
(e) Influence of foreign structures (bonded or not).
Do we need to further define significant?
Section 6: Causes of Measurement Errors ????????
Are these really errors? Change to:
Causes of Measurement Inaccuracies
6.1 Factors that contribute to faulty inaccurate potential measurements include:
Add:
‘’’’’’’ potential measurements include, but are not limited too:
6.1.2 (e) Reference electrode placed in the potential gradient of an anode;
When we take potentials on a cathodically protected pipeline are we not always in a potential gradient of an anode? If not, we will not be protected.
(e) Reference electrode placed in the potential gradient of too close to a galvanic or impressed current anode;
(f) Reference electrode positioned in the potential gradient of a metallic structure other than the one with the potential being measured;
Again this is a statement that can not be measured or defined easily. How can we prevent this when in a ROW with multiple pipelines and CP systems? Either explain and define this better or leave it out!
(g) Electrolyte between pipe and disbonded coating causing error due to electrode placement in electrolyte on opposite side of coating;
This does not cause an error in the potential as related to the cathodic protection at that location.
Suggested change:
(g) Electrolyte between pipe and disbonded coating causing error due to electrode placement in electrolyte on opposite side of coating; can be shielded by certain coatings from the cathodic protection current and if shielded will not be in the same circuit as the electrolyte external to the disbondment and will not have the same potential as the surrounding electrolyte;
6.1.6 Instrument having an analog-to-digital converter operating at such a fast speed that the voltage spikes produced by current interruption are indicated instead of the actual “on” and “off” values.
How is any one going to know this? When did we get equipment that can actually measure the “actual” ON and Instant Off potentials?
6.1.8 Cathodic protection current-carrying conductor used as a test lead for a pipe potential measurement.
Please be more descriptive. All wires we use to measure potentials have carry current or we could not make voltage measurements. Suggestion:
6.1.8 Cathodic protection current-carrying conductor, such as the negative lead of the rectifier, used as a test lead for a pipe potential measurement.
Or make a list of such current carrying conductors.
6.1.9.1 Electromagnetic interference or induction resulting from AC power lines or radio frequency transmitters inducing test lead or instrument errors. This condition is often indicated by a fuzzy, fluctuating, or blurred pointer movement on an analog instrument or erratic displays on digital voltmeters. A DC voltmeter must have sufficient AC rejection capability, which can be determined by referring to the manufacturer’s specification.
Is “Fuzzy” a technical word to be used in this document? If so, define it!
What is “sufficient” AC rejection? Terms like these need to be defined or acceptable limits placed on them.
6.2.1 Soil moisture—If the surface soil is so dry that the electrical contact of the reference electrode with the electrolyte is impaired, the soil around the electrode may be moistened with water until the contact is adequate.
How do we know when “contact is adequate”? Once again this must be defined or better explained.
6.2.4 Concrete or asphalt paved areas— All readings shall be taken with reference electrodes that are in contact with the electrolyte. Readings shall not be taken through concrete or asphalt. Soil contact may be established through at-grade openings or by drilling a small hole through the concrete or asphalt., or by contacting a seam of soil between concrete and asphalt.
Remove “, or by contacting a seam of soil between the concrete or asphalt.” How wide should this seam be? Soil may only be in a surface crack that does not extend completely through the concrete or asphalt and there is not a way too determine this.
7.1.1 Measurement Circuit— The voltage drop other than across the pipe metal/electrolyte interface in the measurement circuit is the sum of the individual voltage drops caused by the meter current flow through individual resistances that include:
Change to “voltage drops caused by the meter current flow through individual resistances that include, but are not limited to:
Reason: The “current” in this circuit is not from the meter, but from the CP system.
Add: voltage drops caused by the current flow through individual resistances that include, but are not limited to:
A measurement error occurs if the analog meter internal resistance or the digital meter internal impedance is not several orders of magnitude higher than the sum of the other resistances in the measurement circuit.
Should this not be 7.1.2 or if it is a part of 7.1.1 then it should be 7.1.1.1? Suggest replacing “error” with “inaccuracy”.
7.1.2 Pipe—Current flowing within the pipe wall creates a voltage drop. This voltage drop and the direction of the current shall be considered when the reference electrode is not near the pipe connection and significant current is conducted by the pipe. Consideration is needed because an error in the pipe-to-electrolyte potential measurement will occur if the pipe current causes a significant voltage drop. Current directed to the pipe connection from the reference electrode causes the measured potential to be more negative by the amount of the pipe current voltage drop (see Figure 2[a]). Conversely, the potential is less negative by that amount if the pipe current direction is from the pipe connection to the reference electrode (see Figure 2[b]).
The use of the word “significant” in sentence 2 and 3 needs to be defined or deleted. Replace “error” with “inaccuracy” in the third sentence.
(b) A voltage drop caused by large voltage gradients in the electrolyte that occur near operating anodes (sometimes termed “raised earth” effect).
Remove (sometimes termed “raised earth” effect) or define it.
7.1.4 Coatings—Most coatings provide protection to the pipe by reducing the pipe surface contact with the environment. Due to the relative ionic impermeability of coatings, they resist current flow. While the insulating ability of coatings reduces the current required for cathodic protection, coatings are not impervious to current flowing through them. Current flow through the coating causes a voltage drop that is greater than when the pipe is bare, under the same environmental conditions.
7.2 Specialized equipment that uses various techniques to measure the impressed current waveform and to calculate a pipe-to-electrolyte potential free of voltage drop is available. This equipment may minimize problems resulting from spiking effects, drifting of interrupters, and current from other DC sources.
Do these instruments actually give a potential “free” of voltage drop or just minimize the affect? There are too many variables in taking potentials to say any method would truly eliminate all voltage drops.
Restate: Specialized equipment that uses various techniques to measure the impressed current waveform and to calculate a pipe-to-electrolyte potential free to help minimize the of voltage drop is available.
8.2.2 Test Method 1 measures the pipe-to-electrolyte potential as the sum of the polarized potential and any voltage drops in the circuit. These voltage drops include those through the electrolyte and pipeline coating from current sources such as impressed current, galvanic anodes, and telluric effects.
Restate first sentence: Test Method 1 is the “ON” potential which is a sum of the native potential, polarization caused by the CP and voltage drops in this circuit.
Restate second sentence: These voltage drops include, but are not limited to those through the electrolyte and pipeline coating from current sources such as impressed current, galvanic anodes, and telluric effects.
8.4.1 Voltmeter with adequate input impedance. Commonly used digital instruments have a nominal impedance of at least 10 MΩ. An analog instrument with an internal resistance of 100 kΩ/V may be adequate in certain circumstances in which the circuit resistance is low. A potentiometer circuit may be necessary in other instances.
Restate the second sentence:
Commonly used digital instruments should (or shall) have an nominal impedance of at least 10 MΩ.
Reasoning: It has been established that there is a need for the digital meters to have at least this much impedance.
8.5.1 Before the test, verify that cathodic protection equipment has been installed and is operating properly. Time should be allowed to pass for the pipeline potentials to reach polarized values.
Restate the second sentence and additions:
If the CP system is newly installed, allow sufficient time for the pipeline to polarize to stable potentials before recording the potentials. If the CP system current output has been recently adjusted, time should be allowed for the changes in polarization, before recording potentials. Polarization should be established on existing CP systems, therefore no time should be allowed to pass before recording potentials.
Reasoning: Each of these situations must be understood by those taking potentials.
8.5.2 (d) Known location of an ineffective coating when the pipeline is coated;
Define ineffective coating. Is this coating that has disbonded, deteriorated, or just does not stop CP current.
8.5.2 (e) Location of a known or suspected corrosive environment.
Delete this statement. What environments are not corrosive or suspected to be? We can not take potentials at all corrosive or suspected corrosive environments.
8.6.1 The significance of voltage drops can be considered by several methods, including:
Restate:
The significance of voltage drops can be considered by several methods, including, but not limited too:
Reasoning these are not all the possible ways to consider voltage drops.
8.6.1.1 Comparing historical levels of cathodic protection with physical evidence from the pipeline to determine whether corrosion has occurred.
8.6.1.2 Comparing soil corrosiveness with physical evidence from the pipeline to determine whether corrosion has occurred.
Add:
8.6.1.3 Measuring or calculating the voltage drop(s).
8.6.2 Physical evidence of corrosion is determined by evaluating items such as:
(a) Leak history data;
(b) Buried pipeline inspection report data regarding locations of coating failures, localized conditions of more corrosive electrolyte, or substandard cathodic protection levels have been experienced; and
(c) Verification of in-line inspection tool metal loss indications by follow-up excavation of anomalies and inspection of the pipe external surface.
Add:
(d) Proper evaluation of external corrosion, if found, to ensure the corrosion that has occurred was not caused by disbonded CP shielding coatings, other shielding materials or corrosion that existed before adequate CP was applied.
9.32.2 To avoid significant depolarization of the pipe, the off period should be limited to the time necessary to make an accurate potential measurement. The off period is typically less than 3 seconds.
If the typical “Off period” is given, why not the typical “on period”?
9.32.3 The magnitude and duration of a voltage spike caused by current interruption can vary, but the duration is typically within 0.5 second. After the current is interrupted, the time elapsed until the measurement is recorded should be long enough to avoid errors caused by voltage spiking. On-site measurements with appropriate instruments may be necessary to determine the duration and magnitude of the spiking.
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
9.32.4 Current sources that can affect the accuracy of this test method include the following:
Restate:
Current sources that can affect the accuracy of this test method include, but are not limited too, the following:
(a) Unknown, inaccessible, or direct connected galvanic anodes;
Restate:
(a) Unknown, inaccessible, or direct connected galvanic anodes or unknown impressed current systems;
(h) Parallel coated pipelines, electrically connected and polarized to different potentials;
Restate:
(h) Parallel coated pipelines (bare or coated), electrically connected and polarized to different potentials;
9.54.1 Voltmeter with adequate input impedance. Commonly used digital instruments have a nominal impedance of at least 10 MΩ. An analog instrument with an internal resistance of 100 kΩ/V may be adequate in certain circumstances in which the circuit resistance is low. A potentiometer circuit may be necessary in other instances.
Restate as above in 8.4.1.
9.54.3 Sufficient current interrupters to disengage influential cathodic protection current sources simultaneously.
Define “influential” and “simultaneously” as related to this statement. These surveys are difficult enough to perform to get somewhat accurate data without using these type words. Please define or restate.
9.65.1 Before the test, verify that cathodic protection equipment has been installed and is operating properly. Time should be allowed for the pipeline potentials to reach polarized values.
Restate as in 8.5.1.
9.65.2 Install and place in operation necessary interrupter equipment in all significant DC sources protecting the pipe at the test site, and place in operation with a synchronized or known off and on cycle. The off cycle should be kept as short as possible but still long enough to read a polarized pipe-to-electrolyte potential after any spike as shown in Figure 3(a) has collapsed.
Again this is vague in the description of what is expected. Nice words, but do they really give the user the guidance they need to perform these tests? The problem of course is that we do not know how long any of this should truly be since each situation is different. Suggest we are at least consistent with what we do and provide more specific values of times at which to set the on/off readings.
(d) Known location of an ineffective coating when the pipeline is coated; and
See statement as in 8.5.2 (d) above.
(e) Location of a known or suspected corrosive environment.
Delete as in 8.5.2 above.
9.65.5.1 If spiking may be present, use an appropriate instrument, such as an oscilloscope or high-speed recording device, to verify that the measured values are not influenced by a voltage spike.
How do you know if spiking is present unless you use one of these instruments? Either require use of these meters or delete the statement. Does not the spiking change along the pipeline? The accuracy of these instruments needs to be given. Why not just require meters that using a time cycle to determine what the potential is at that particular time and record this value. At least it is consistent!
10.2 Other current sources that can affect the accuracy of this test method include the following:
Restate as in section 8 and 9.
Current sources that can affect the accuracy of this test method include, but are not limited too, the following:
(a) Unknown, inaccessible, or direct connected galvanic anodes;
(a) Unknown, inaccessible, or direct connected galvanic anodes or unknown impressed current systems;
(h) Parallel coated pipelines, electrically connected and polarized to different potentials;
Restate:
(h) Parallel coated pipelines (bare or coated), electrically connected and polarized to different potentials;
10.2.2.310.3.2.2 The magnitude and duration of a voltage spike caused by current interruption can vary, but the duration is typically within 0.5 second. After the current is interrupted, the time elapsed until the measurement is recorded should be long enough to avoid errors caused by voltage spiking. On-site measurements with appropriate instruments may be necessary to determine the duration and magnitude of the spiking.
Restate as in section 9.2.3
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
(b) This method is advantageous when corrosion potentials may be low (for example, 500 mV
or less negative) or the current required to meet a polarized potential criterion would be considered excessive.
Restate:
(b) This method is advantageous when the “ON” corrosion potentials may be more positive than -850 mV low (for example, 500 mV or less negative) or the current required to meet a polarized potential criterion would be considered excessive.
10.23.4.1 Voltmeter with adequate input impedance. Commonly used digital instruments have a nominal impedance of at least 10 MΩ. An analog instrument with an internal resistance of 100 Ω/V may be adequate in certain circumstances in which the circuit resistance is low. A potentiometer circuit may be necessary in other instances.
Restate as in 8.4. 1
10.23.4.3 Sufficient current interrupters to interrupt influential cathodic protection current sources simultaneously.
10.3.3.2 As shown below contradicts the statement above when we say that we can just interrupt the “influential” CP current sources.
(c) Test results are difficult or impossible to analyze when direct connected galvanic anodes or
foreign impressed current devices are present and cannot be interrupted, or when stray currents are present.
These statements need to be resolved and restated.
10.23.5.1 Before the test, verify that cathodic protection equipment has been installed and is operating properly. Time be allowed for the pipeline potentials to reach polarized values.
Restate as shown in 8.5.1 above.
10.23.5.2 Install and place in operation necessary interrupter equipment in all significant DC sources protecting the pipe at the test site, and place in operation with a synchronized or known off and on cycle. The off cycle should be kept as short as possible but still long enough to read a polarized pipe-to-electrolyte potential after any spike as shown in Figure 3(a) has collapsed.
Again this is vague in the description of what is expected. Nice words, but do they really give the user the guidance they need to perform these tests? The problem of course is that we do not know how long any of this should truly be since each situation is different. Suggest we are at least consistent with what we do and provide more specific values of times at which to set the on/off readings.
(d) Known location of an ineffective coating when the pipeline is coated; and
See statement as in 8.5.2 (d) above.
(e) Location of a known or suspected corrosive environment.
Delete as in 8.5.2 above.
10.23.5.5.1 If spiking may be present, use an appropriate instrument, such as an oscilloscope or high-speed recording device, to verify that the measured values are not influenced by a voltage spike.
How do you know if spiking is present unless you use one of these instruments? Either require use of these meters or delete the statement. Does not the spiking change along the pipeline? The accuracy of these instruments needs to be given. Why not just require meters that using a time cycle to determine what the potential is at that particular time and record this value. At least it is consistent!
10.23.5.6 Measure and record the pipe-to-electrolyte on and instant off potentials and their polarities with respect to the reference electrode.
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
10.23.5.6.1 The instant off pipe-to-electrolyte potential is the baseline potential from which the polarization decay is calculated.
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
10.2.5.7.310.3.5.7.2 When extended polarization decay time periods are anticipated, it may be desirable to use recording voltmeters to determine when adequate polarization decay or a corrosion potential has been attained.
Add 10.3.5.7.2.1
Ensure there are no interference problems with foreign CP systems and other DC power sources that will affect the depolarizing pipeline during the time the CP is off.
Make the same adjustments and comments in Test Method 3B as mentioned above in Test Method 3A.
Thank you very much for your very hard work and effort to make this document better. I hope my comments and suggestions help.
Richard Norsworthy
214-912-9072
richnors@flash.net
Please respond to the ballot if you have not. I have attached my negative response below.
COMMENTS ON SPO497 REVISION
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Third Paragraph - Second Sentence
It includes methods for voltage drop considerations when pipe-to-electrolyte potential measurements are made and provides guidance to prevent minimize incorrect data from being collected and used.
Change “prevent” to “minimize”. This document can not prevent someone from taking incorrect data, but if followed, can minimize the problem.
Definitions
Coating: A liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film.
Definition needs to be changed to below since pipeline coatings are much more than the proposed definition.
Coating: (1) A liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film; (2) (in a more general sense) a thin layer of solid material on a surface that provides improved protective, decorative, or functional properties. For the purposes of this standard, “Coating” is defined as an electrically insulating material applied to the surface of a metallic structure that provides an adherent film which protects a metallic structure from the surrounding electrolyte.
Section 4: Instrumentation and Measurement Guidelines
4.1 Valid cCathodic protection electrical measurements require proper selection and use of instruments. Pipe-to-electrolyte potential, voltage drop, potential difference, and similar measurements require instruments that have appropriate voltage ranges. The user should must know the capabilities and limitations of the equipment, follow the manufacturer’s instruction manual, and be skilled in the use of electrical instruments.
Change second sentence to read –
The user should must know or be directed by someone who knows the capabilities and limitations of the equipment, follow the manufacturer’s instruction manual, and be skilled in the use of electrical instruments.
Reason: Someone just starting in CP work will need to be under the direction of someone who is experienced in the use of these instruments.
4.3.1 To measure pipe-to-electrolyte potentials accurately, a digital voltmeter must have a high input impedance (high internal resistance, for an analog instrument) compared with the total resistance of the measurement circuit.
To what “accuracy” do we make these measurements? Delete the word “accurately” unless the level of accuracy is defined.
4.3.1.1 An input impedance of 10 MΩ or more should be sufficient for a digital meter. An instrument with a lower input impedance may produce valid data if circuit contact errors are considered. One means of making accurate measurements is to use a potentiometer circuit in an analog meter.
Delete the second and third sentence. The first sentence is all that is needed. The rest is confusing and would need much more detail.
4.3.2 Some analog-to-digital converters used in digital and data logging instruments operate so fast that the instrument may indicate only a portion of the input waveform and thus provide incorrect voltage indications.
Why include such meters if they are incorrect? Delete this sentence and all other references to these type meters or add more definition to clarify which instruments are not acceptable.
4.3.3 Parallax errors on an analog instrument can be minimized by viewing the needle perpendicular to the face of the instrument on the centerline projected from the needle point.
Define “Parallax”.
4.3.4 The accuracy of potential measurements should be verified by using an instrument having two or more input impedances (internal resistance, for analog instruments) and comparing potential values measured using different input impedances. If the measured values are virtually the same, the accuracy is acceptable. Corrections need to be made if measured values are not virtually identical. Digital voltmeters that have a constant input impedance do not indicate a measurement error by changing voltage ranges. An alternative is to use a meter with a potentiometer circuit.
In 4.3.1.1 indicates if a digital meter of 10 MΩ of impedance or more is used, then this should not be a problem for digital meters. Why complicate the matter. 4.4 tells how to check for the accuracy of the meter.
Information like this if needed should be placed in Appendix.
5.5 A pipe-to-electrolyte potential is measured using a DC voltmeter having an appropriate input impedance (or internal resistance, for an analog instrument), voltage range(s), test leads, and a stable reference electrode, such as a saturated copper/copper sulfate (CSE), silver/silver chloride (Ag/AgCl), or saturated potassium chloride (KCl) calomel reference electrode (SCE). The CSE is usually used for measurements when the electrolyte is soil or fresh water and less often for salt water. When a CSE is used in a high-chloride environment, the stability (lack of contamination) of the CSE must be determined before the readings may be considered valid. The Ag/AgCl reference electrode is usually used in seawater environments. The saturated KCl calomel electrode is used more often for laboratory work. However, more rugged, polymer body, gel- filled saturated KCl calomel electrodes are available, though modifications may be necessary to increase contact area with the environment.
Where is the reference for zinc? Some still use zinc for reference electrodes and we teach it in the CP classes. We should have guidance in this document for zinc also.
5.7 Valid The pipe-to-electrolyte potential measurement of a buried pipe should be are made with the reference electrode placed close to the metal/electrolyte interface of the pipe. The common practice, however, is to place the reference electrode as close to the pipe as practicable, which is usually at the surface of the earth above the centerline of the pipe. (See Figure 1[a].) This measurement includes a combination of the voltage drops associated with the:
Change last sentence:
This measurement includes, but is not limited to, a combination of voltage drops associated with the:
Reasoning: There could be other possible voltage drops that may affect these potential readings such as contact resistant of reference electrode contact to the electrolyte, etc.
5.8 The pipe-to-electrolyte potential measurement as described above is a resultant of the:
(a) Voltage drop created by current flowing through the electrical resistances of the items listed in Paragraph 5.7; and
(b) For coated pipe, the influence of coating holidays, depending on their location, number, and size.
Remove part “b”. We have already mentioned that coating has an affect on the reading. The holidays in the coating are part of the circuit, but there are many others that also affect it. Do we list all of them? If needed make a separate section or add it to the 7.1.4 section. Make one statement:
5.8 The pipe-to-electrolyte potential measurement as described above is a result of the voltage drop created by current flowing through the electrical resistances of the items listed in Paragraph 5.7.
5.9 (d) Parallel coated pipelines, electrically connected and polarized to different potentials;
Restate:
(d) Parallel pipelines (coated or bare) and other metal structures, electrically connected and polarized to different potentials;
Reasoning; All metal structures connected to the circuit will affect the potentials.
(i) Unknown, inaccessible, or direct connected galvanic anodes;
Restate;
(i) Galvanic anodes, known or unknown, connected to the pipe;
Reasoning; Galvanic anodes are going to affect the potentials whether they are known or not and whether they are inaccessible or direct connected.
5.10 Voltage drops other than those across the pipe metal/electrolyte interface shall be considered for valid interpretation of pipe-to-electrolyte voltage measurements made to satisfy a criterion. Measurement errors should must be minimized to ensure reliable pipe-to-electrolyte potential measurements.
Reword or remove the last sentence. The first sentence should be sufficient since we say the voltage drops shall be considered.
5.12 When voltage drops have been evaluated at a test location and the pipe-to-electrolyte potential found to be satisfactory, the ―on‖ pipe-to-electrolyte potential value may be used for monitoring until significant environmental, structural, or cathodic protection system parameters change.
5.12.1 Significant environmental, structural, or cathodic protection system parameter changes may include:
(a) Replacement or addition of piping;
(b) Addition, relocation, or deterioration of cathodic protection systems;
(c) Failure of electrical isolating devices;
(d) Effectiveness of coatings; and
(e) Influence of foreign structures (bonded or not).
Do we need to further define significant?
Section 6: Causes of Measurement Errors ????????
Are these really errors? Change to:
Causes of Measurement Inaccuracies
6.1 Factors that contribute to faulty inaccurate potential measurements include:
Add:
‘’’’’’’ potential measurements include, but are not limited too:
6.1.2 (e) Reference electrode placed in the potential gradient of an anode;
When we take potentials on a cathodically protected pipeline are we not always in a potential gradient of an anode? If not, we will not be protected.
(e) Reference electrode placed in the potential gradient of too close to a galvanic or impressed current anode;
(f) Reference electrode positioned in the potential gradient of a metallic structure other than the one with the potential being measured;
Again this is a statement that can not be measured or defined easily. How can we prevent this when in a ROW with multiple pipelines and CP systems? Either explain and define this better or leave it out!
(g) Electrolyte between pipe and disbonded coating causing error due to electrode placement in electrolyte on opposite side of coating;
This does not cause an error in the potential as related to the cathodic protection at that location.
Suggested change:
(g) Electrolyte between pipe and disbonded coating causing error due to electrode placement in electrolyte on opposite side of coating; can be shielded by certain coatings from the cathodic protection current and if shielded will not be in the same circuit as the electrolyte external to the disbondment and will not have the same potential as the surrounding electrolyte;
6.1.6 Instrument having an analog-to-digital converter operating at such a fast speed that the voltage spikes produced by current interruption are indicated instead of the actual “on” and “off” values.
How is any one going to know this? When did we get equipment that can actually measure the “actual” ON and Instant Off potentials?
6.1.8 Cathodic protection current-carrying conductor used as a test lead for a pipe potential measurement.
Please be more descriptive. All wires we use to measure potentials have carry current or we could not make voltage measurements. Suggestion:
6.1.8 Cathodic protection current-carrying conductor, such as the negative lead of the rectifier, used as a test lead for a pipe potential measurement.
Or make a list of such current carrying conductors.
6.1.9.1 Electromagnetic interference or induction resulting from AC power lines or radio frequency transmitters inducing test lead or instrument errors. This condition is often indicated by a fuzzy, fluctuating, or blurred pointer movement on an analog instrument or erratic displays on digital voltmeters. A DC voltmeter must have sufficient AC rejection capability, which can be determined by referring to the manufacturer’s specification.
Is “Fuzzy” a technical word to be used in this document? If so, define it!
What is “sufficient” AC rejection? Terms like these need to be defined or acceptable limits placed on them.
6.2.1 Soil moisture—If the surface soil is so dry that the electrical contact of the reference electrode with the electrolyte is impaired, the soil around the electrode may be moistened with water until the contact is adequate.
How do we know when “contact is adequate”? Once again this must be defined or better explained.
6.2.4 Concrete or asphalt paved areas— All readings shall be taken with reference electrodes that are in contact with the electrolyte. Readings shall not be taken through concrete or asphalt. Soil contact may be established through at-grade openings or by drilling a small hole through the concrete or asphalt., or by contacting a seam of soil between concrete and asphalt.
Remove “, or by contacting a seam of soil between the concrete or asphalt.” How wide should this seam be? Soil may only be in a surface crack that does not extend completely through the concrete or asphalt and there is not a way too determine this.
7.1.1 Measurement Circuit— The voltage drop other than across the pipe metal/electrolyte interface in the measurement circuit is the sum of the individual voltage drops caused by the meter current flow through individual resistances that include:
Change to “voltage drops caused by the meter current flow through individual resistances that include, but are not limited to:
Reason: The “current” in this circuit is not from the meter, but from the CP system.
Add: voltage drops caused by the current flow through individual resistances that include, but are not limited to:
A measurement error occurs if the analog meter internal resistance or the digital meter internal impedance is not several orders of magnitude higher than the sum of the other resistances in the measurement circuit.
Should this not be 7.1.2 or if it is a part of 7.1.1 then it should be 7.1.1.1? Suggest replacing “error” with “inaccuracy”.
7.1.2 Pipe—Current flowing within the pipe wall creates a voltage drop. This voltage drop and the direction of the current shall be considered when the reference electrode is not near the pipe connection and significant current is conducted by the pipe. Consideration is needed because an error in the pipe-to-electrolyte potential measurement will occur if the pipe current causes a significant voltage drop. Current directed to the pipe connection from the reference electrode causes the measured potential to be more negative by the amount of the pipe current voltage drop (see Figure 2[a]). Conversely, the potential is less negative by that amount if the pipe current direction is from the pipe connection to the reference electrode (see Figure 2[b]).
The use of the word “significant” in sentence 2 and 3 needs to be defined or deleted. Replace “error” with “inaccuracy” in the third sentence.
(b) A voltage drop caused by large voltage gradients in the electrolyte that occur near operating anodes (sometimes termed “raised earth” effect).
Remove (sometimes termed “raised earth” effect) or define it.
7.1.4 Coatings—Most coatings provide protection to the pipe by reducing the pipe surface contact with the environment. Due to the relative ionic impermeability of coatings, they resist current flow. While the insulating ability of coatings reduces the current required for cathodic protection, coatings are not impervious to current flowing through them. Current flow through the coating causes a voltage drop that is greater than when the pipe is bare, under the same environmental conditions.
7.2 Specialized equipment that uses various techniques to measure the impressed current waveform and to calculate a pipe-to-electrolyte potential free of voltage drop is available. This equipment may minimize problems resulting from spiking effects, drifting of interrupters, and current from other DC sources.
Do these instruments actually give a potential “free” of voltage drop or just minimize the affect? There are too many variables in taking potentials to say any method would truly eliminate all voltage drops.
Restate: Specialized equipment that uses various techniques to measure the impressed current waveform and to calculate a pipe-to-electrolyte potential free to help minimize the of voltage drop is available.
8.2.2 Test Method 1 measures the pipe-to-electrolyte potential as the sum of the polarized potential and any voltage drops in the circuit. These voltage drops include those through the electrolyte and pipeline coating from current sources such as impressed current, galvanic anodes, and telluric effects.
Restate first sentence: Test Method 1 is the “ON” potential which is a sum of the native potential, polarization caused by the CP and voltage drops in this circuit.
Restate second sentence: These voltage drops include, but are not limited to those through the electrolyte and pipeline coating from current sources such as impressed current, galvanic anodes, and telluric effects.
8.4.1 Voltmeter with adequate input impedance. Commonly used digital instruments have a nominal impedance of at least 10 MΩ. An analog instrument with an internal resistance of 100 kΩ/V may be adequate in certain circumstances in which the circuit resistance is low. A potentiometer circuit may be necessary in other instances.
Restate the second sentence:
Commonly used digital instruments should (or shall) have an nominal impedance of at least 10 MΩ.
Reasoning: It has been established that there is a need for the digital meters to have at least this much impedance.
8.5.1 Before the test, verify that cathodic protection equipment has been installed and is operating properly. Time should be allowed to pass for the pipeline potentials to reach polarized values.
Restate the second sentence and additions:
If the CP system is newly installed, allow sufficient time for the pipeline to polarize to stable potentials before recording the potentials. If the CP system current output has been recently adjusted, time should be allowed for the changes in polarization, before recording potentials. Polarization should be established on existing CP systems, therefore no time should be allowed to pass before recording potentials.
Reasoning: Each of these situations must be understood by those taking potentials.
8.5.2 (d) Known location of an ineffective coating when the pipeline is coated;
Define ineffective coating. Is this coating that has disbonded, deteriorated, or just does not stop CP current.
8.5.2 (e) Location of a known or suspected corrosive environment.
Delete this statement. What environments are not corrosive or suspected to be? We can not take potentials at all corrosive or suspected corrosive environments.
8.6.1 The significance of voltage drops can be considered by several methods, including:
Restate:
The significance of voltage drops can be considered by several methods, including, but not limited too:
Reasoning these are not all the possible ways to consider voltage drops.
8.6.1.1 Comparing historical levels of cathodic protection with physical evidence from the pipeline to determine whether corrosion has occurred.
8.6.1.2 Comparing soil corrosiveness with physical evidence from the pipeline to determine whether corrosion has occurred.
Add:
8.6.1.3 Measuring or calculating the voltage drop(s).
8.6.2 Physical evidence of corrosion is determined by evaluating items such as:
(a) Leak history data;
(b) Buried pipeline inspection report data regarding locations of coating failures, localized conditions of more corrosive electrolyte, or substandard cathodic protection levels have been experienced; and
(c) Verification of in-line inspection tool metal loss indications by follow-up excavation of anomalies and inspection of the pipe external surface.
Add:
(d) Proper evaluation of external corrosion, if found, to ensure the corrosion that has occurred was not caused by disbonded CP shielding coatings, other shielding materials or corrosion that existed before adequate CP was applied.
9.32.2 To avoid significant depolarization of the pipe, the off period should be limited to the time necessary to make an accurate potential measurement. The off period is typically less than 3 seconds.
If the typical “Off period” is given, why not the typical “on period”?
9.32.3 The magnitude and duration of a voltage spike caused by current interruption can vary, but the duration is typically within 0.5 second. After the current is interrupted, the time elapsed until the measurement is recorded should be long enough to avoid errors caused by voltage spiking. On-site measurements with appropriate instruments may be necessary to determine the duration and magnitude of the spiking.
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
9.32.4 Current sources that can affect the accuracy of this test method include the following:
Restate:
Current sources that can affect the accuracy of this test method include, but are not limited too, the following:
(a) Unknown, inaccessible, or direct connected galvanic anodes;
Restate:
(a) Unknown, inaccessible, or direct connected galvanic anodes or unknown impressed current systems;
(h) Parallel coated pipelines, electrically connected and polarized to different potentials;
Restate:
(h) Parallel coated pipelines (bare or coated), electrically connected and polarized to different potentials;
9.54.1 Voltmeter with adequate input impedance. Commonly used digital instruments have a nominal impedance of at least 10 MΩ. An analog instrument with an internal resistance of 100 kΩ/V may be adequate in certain circumstances in which the circuit resistance is low. A potentiometer circuit may be necessary in other instances.
Restate as above in 8.4.1.
9.54.3 Sufficient current interrupters to disengage influential cathodic protection current sources simultaneously.
Define “influential” and “simultaneously” as related to this statement. These surveys are difficult enough to perform to get somewhat accurate data without using these type words. Please define or restate.
9.65.1 Before the test, verify that cathodic protection equipment has been installed and is operating properly. Time should be allowed for the pipeline potentials to reach polarized values.
Restate as in 8.5.1.
9.65.2 Install and place in operation necessary interrupter equipment in all significant DC sources protecting the pipe at the test site, and place in operation with a synchronized or known off and on cycle. The off cycle should be kept as short as possible but still long enough to read a polarized pipe-to-electrolyte potential after any spike as shown in Figure 3(a) has collapsed.
Again this is vague in the description of what is expected. Nice words, but do they really give the user the guidance they need to perform these tests? The problem of course is that we do not know how long any of this should truly be since each situation is different. Suggest we are at least consistent with what we do and provide more specific values of times at which to set the on/off readings.
(d) Known location of an ineffective coating when the pipeline is coated; and
See statement as in 8.5.2 (d) above.
(e) Location of a known or suspected corrosive environment.
Delete as in 8.5.2 above.
9.65.5.1 If spiking may be present, use an appropriate instrument, such as an oscilloscope or high-speed recording device, to verify that the measured values are not influenced by a voltage spike.
How do you know if spiking is present unless you use one of these instruments? Either require use of these meters or delete the statement. Does not the spiking change along the pipeline? The accuracy of these instruments needs to be given. Why not just require meters that using a time cycle to determine what the potential is at that particular time and record this value. At least it is consistent!
10.2 Other current sources that can affect the accuracy of this test method include the following:
Restate as in section 8 and 9.
Current sources that can affect the accuracy of this test method include, but are not limited too, the following:
(a) Unknown, inaccessible, or direct connected galvanic anodes;
(a) Unknown, inaccessible, or direct connected galvanic anodes or unknown impressed current systems;
(h) Parallel coated pipelines, electrically connected and polarized to different potentials;
Restate:
(h) Parallel coated pipelines (bare or coated), electrically connected and polarized to different potentials;
10.2.2.310.3.2.2 The magnitude and duration of a voltage spike caused by current interruption can vary, but the duration is typically within 0.5 second. After the current is interrupted, the time elapsed until the measurement is recorded should be long enough to avoid errors caused by voltage spiking. On-site measurements with appropriate instruments may be necessary to determine the duration and magnitude of the spiking.
Restate as in section 9.2.3
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
(b) This method is advantageous when corrosion potentials may be low (for example, 500 mV
or less negative) or the current required to meet a polarized potential criterion would be considered excessive.
Restate:
(b) This method is advantageous when the “ON” corrosion potentials may be more positive than -850 mV low (for example, 500 mV or less negative) or the current required to meet a polarized potential criterion would be considered excessive.
10.23.4.1 Voltmeter with adequate input impedance. Commonly used digital instruments have a nominal impedance of at least 10 MΩ. An analog instrument with an internal resistance of 100 Ω/V may be adequate in certain circumstances in which the circuit resistance is low. A potentiometer circuit may be necessary in other instances.
Restate as in 8.4. 1
10.23.4.3 Sufficient current interrupters to interrupt influential cathodic protection current sources simultaneously.
10.3.3.2 As shown below contradicts the statement above when we say that we can just interrupt the “influential” CP current sources.
(c) Test results are difficult or impossible to analyze when direct connected galvanic anodes or
foreign impressed current devices are present and cannot be interrupted, or when stray currents are present.
These statements need to be resolved and restated.
10.23.5.1 Before the test, verify that cathodic protection equipment has been installed and is operating properly. Time be allowed for the pipeline potentials to reach polarized values.
Restate as shown in 8.5.1 above.
10.23.5.2 Install and place in operation necessary interrupter equipment in all significant DC sources protecting the pipe at the test site, and place in operation with a synchronized or known off and on cycle. The off cycle should be kept as short as possible but still long enough to read a polarized pipe-to-electrolyte potential after any spike as shown in Figure 3(a) has collapsed.
Again this is vague in the description of what is expected. Nice words, but do they really give the user the guidance they need to perform these tests? The problem of course is that we do not know how long any of this should truly be since each situation is different. Suggest we are at least consistent with what we do and provide more specific values of times at which to set the on/off readings.
(d) Known location of an ineffective coating when the pipeline is coated; and
See statement as in 8.5.2 (d) above.
(e) Location of a known or suspected corrosive environment.
Delete as in 8.5.2 above.
10.23.5.5.1 If spiking may be present, use an appropriate instrument, such as an oscilloscope or high-speed recording device, to verify that the measured values are not influenced by a voltage spike.
How do you know if spiking is present unless you use one of these instruments? Either require use of these meters or delete the statement. Does not the spiking change along the pipeline? The accuracy of these instruments needs to be given. Why not just require meters that using a time cycle to determine what the potential is at that particular time and record this value. At least it is consistent!
10.23.5.6 Measure and record the pipe-to-electrolyte on and instant off potentials and their polarities with respect to the reference electrode.
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
10.23.5.6.1 The instant off pipe-to-electrolyte potential is the baseline potential from which the polarization decay is calculated.
Is this the so called “instant off” potential? If so, there are many folks who use a faster cycle than 0.5 second for CIS. How do we actually measure “instant”? What about all the other variables mentioned above in section 8.6? Seems as if this is a very difficult procedure with many variables that must be properly addressed and not just mentioned.
10.2.5.7.310.3.5.7.2 When extended polarization decay time periods are anticipated, it may be desirable to use recording voltmeters to determine when adequate polarization decay or a corrosion potential has been attained.
Add 10.3.5.7.2.1
Ensure there are no interference problems with foreign CP systems and other DC power sources that will affect the depolarizing pipeline during the time the CP is off.
Make the same adjustments and comments in Test Method 3B as mentioned above in Test Method 3A.
Thank you very much for your very hard work and effort to make this document better. I hope my comments and suggestions help.
Richard Norsworthy
214-912-9072
richnors@flash.net
Very good comments from Kerry Morgan
Yes Richard we have a lot more work to do. As I have done research over the past few months I am becoming quiet disturbed regarding the direction NACE and PHMSA are going.
I have anecdotal evidence from people who have taken NACE corrosion courses over the past few years that -.850 with current applied is not even discussed in the classes. I was under the impression that the purpose of organizations like NACE and its various committees was to research, discuss, and propose revisions to existing standards. I would contend that until a standard has been revised it should be taught as written without preference to one part or another. I for one am not ready to throw Peabody under the bus. There is too much practical and empirical data to support his theories.
I would also contend that PHMSA stands poised to incorporate the SPO169 revision by reference into Federal code. I hope everyone involved understands the implications of incorporation by reference. I am neither a parliamentarian nor an expert on Federal codes and rule making procedures. But if I understand what I read on PHMSA’s website correctly , Congress gave complete authority to the Director of the Federal Register to determine whether a proposed incorporation by reference serves the public interest and approve the agency's IBR request. Does this mean there will be no opportunity to comment on the change to the Federal code?
Further research on PHMSA’s website shows that since 1989 196 significant incidents related to external corrosion were reported. Further research to ascertain if these incidents also involved a violation of current code will take much more time, but I would suggest that significant incidents related to external corrosion were also in violation of existing code.
Revising SPO169 to require -.850 without current applied will not magically prevent violations of code. The costs associated with complying to the revised standard when PHMSA incorporates it will in effect be prematurely fining the pipeline industry before an incident occurs.
Kerry L. Morgan
Senior Corrosion Technologist 5037
NACE 133125
I have anecdotal evidence from people who have taken NACE corrosion courses over the past few years that -.850 with current applied is not even discussed in the classes. I was under the impression that the purpose of organizations like NACE and its various committees was to research, discuss, and propose revisions to existing standards. I would contend that until a standard has been revised it should be taught as written without preference to one part or another. I for one am not ready to throw Peabody under the bus. There is too much practical and empirical data to support his theories.
I would also contend that PHMSA stands poised to incorporate the SPO169 revision by reference into Federal code. I hope everyone involved understands the implications of incorporation by reference. I am neither a parliamentarian nor an expert on Federal codes and rule making procedures. But if I understand what I read on PHMSA’s website correctly , Congress gave complete authority to the Director of the Federal Register to determine whether a proposed incorporation by reference serves the public interest and approve the agency's IBR request. Does this mean there will be no opportunity to comment on the change to the Federal code?
Further research on PHMSA’s website shows that since 1989 196 significant incidents related to external corrosion were reported. Further research to ascertain if these incidents also involved a violation of current code will take much more time, but I would suggest that significant incidents related to external corrosion were also in violation of existing code.
Revising SPO169 to require -.850 without current applied will not magically prevent violations of code. The costs associated with complying to the revised standard when PHMSA incorporates it will in effect be prematurely fining the pipeline industry before an incident occurs.
Kerry L. Morgan
Senior Corrosion Technologist 5037
NACE 133125
Tuesday, November 24, 2009
We have more work to do!
WE HAVE MORE WORK TO DO!!!!
As we approach the end of the year please keep in mind there may be a NEW ballot from the TG 360 committee for the NEW SP0169-2007 revision in early January 2010. I am not sure what changes have been or will be made at this time, but we will see. The TG 360 committee would like to have the vote as early as possible next year so they can address any negatives at CORROSION 2010 in San Antonio, TX (next March).
You can log on to the Technical Committees Online Balloting Web page on the NACE.org website to see how many people responded and joined the voting pool as well as the individuals who submitted a vote with comments. Go to the NACE International.org website, then chose “Committees”, then “Online Balloting”, then Log in with your NACE number and Password. Once on this page, go to “TCC Balloting Results” and find the TG 360 group (page 9 when I looked). If you click on results you will get the voting information from the last ballot. A sample is below showing the number of folks who have signed up to vote and the number that actually voted.
Total Eligible Voters Number Voting Percent Voting
All Voters 391 270 69.1 %
STG Voters 313 222 70.9 %
If you click on the “Comments” you will be able to see those who voted to affirm, negative or abstain. You can also see all comments from those who made them. Reading these comments helps you to understand why many voted the way they did, as well as the concern expressed by some voters. These comments may help with your vote and how to make technical comments if your vote is negative. Please make “good” technical comments and arguments if you vote negative. If you vote for affirmation, you do not have to provide comments, but are welcome to do so. Abstaining votes do not count on the final pass/fail criterion, but you can provide comments if you wish.
Those who are on the voting list (391) can vote on the next ballot. You did not have to vote on the first ballot to vote on this one, but you must have signed up on the original voting list. So if you did not sign up on the “Balloting List”, you can not vote on the next ballot. See the Post below from Daniela Matthews at NACE.
If there is a doubt of whether you are on the balloting list, you should be able to contact daniela.matthews@nace.org.
To me there is so much evidence to show that the use of the “ON” -850 mV or more negative criterion (even without IR drop consideration) is valid. I will be posting some reports from the 1990 revision effort discussing many of the test site results for the PRCI report as well as some information from other companies. Basically, they show that if you can achieve a -850 mV “ON” potential (even without IR drop consideration) you can also achieve the 100 mV of polarization. I have also sent this information to Neil Thompson of DNV who is involved in the new PRCI study and report on whether the -850 mV “ON” criterion is valid. If you company is a member of the PRCI, please get involved.
I think we all understand that nothing is 100% and we can still have external corrosion in some cases even if we meet or exceed all criteria. Please pass along any data that may help the PRCI or TG 360 committee on their important missions. You can send it directly to the committee(s) or you can send it to me and I will forward it.
Many countries around the world will be relaxing this time of year because of the various holidays, especially in North America, but we must keep alert and provide the needed information to help this committee provide the industry with the best documents and reports possible. Without your help, they will not achieve that goal.
I am hoping that the changes to this new ballot will be allow us to all feel much more comfortable with what is written. Many are concerned about the regulatory implications in the various countries of the original proposed criteria. We will see what changes, if any, are in the new revision.
We need everyone who signed up to vote to vote! This is a critical document to the pipeline industry. No matter what your vote, please vote. Those who are not on the voting list, but have comments or issues you can pass those along to me and I will post them on the blog. I will also help anyone who is not sure how to word their comments with suggestions if there is a need.
I will pass along my thoughts of the new revision after it comes out for balloting. We also encourage others to make comments, no matter what your vote may be. We need to hear everyone’s opinion! Not just mine. Not just negative voters. Sharing information and concerns is how we are going to learn and make an educated decision.
Again, I will think the committee and all others who have worked so hard on this matter. We all want the same thing, a reasonable, sound document that works to provide the industry with guidance to provide safe, economical and environmentally friendly pipelines for the world’s future energy needs.
Richard Norsworthy
Polyguard Products, Inc.
As we approach the end of the year please keep in mind there may be a NEW ballot from the TG 360 committee for the NEW SP0169-2007 revision in early January 2010. I am not sure what changes have been or will be made at this time, but we will see. The TG 360 committee would like to have the vote as early as possible next year so they can address any negatives at CORROSION 2010 in San Antonio, TX (next March).
You can log on to the Technical Committees Online Balloting Web page on the NACE.org website to see how many people responded and joined the voting pool as well as the individuals who submitted a vote with comments. Go to the NACE International.org website, then chose “Committees”, then “Online Balloting”, then Log in with your NACE number and Password. Once on this page, go to “TCC Balloting Results” and find the TG 360 group (page 9 when I looked). If you click on results you will get the voting information from the last ballot. A sample is below showing the number of folks who have signed up to vote and the number that actually voted.
Total Eligible Voters Number Voting Percent Voting
All Voters 391 270 69.1 %
STG Voters 313 222 70.9 %
If you click on the “Comments” you will be able to see those who voted to affirm, negative or abstain. You can also see all comments from those who made them. Reading these comments helps you to understand why many voted the way they did, as well as the concern expressed by some voters. These comments may help with your vote and how to make technical comments if your vote is negative. Please make “good” technical comments and arguments if you vote negative. If you vote for affirmation, you do not have to provide comments, but are welcome to do so. Abstaining votes do not count on the final pass/fail criterion, but you can provide comments if you wish.
Those who are on the voting list (391) can vote on the next ballot. You did not have to vote on the first ballot to vote on this one, but you must have signed up on the original voting list. So if you did not sign up on the “Balloting List”, you can not vote on the next ballot. See the Post below from Daniela Matthews at NACE.
If there is a doubt of whether you are on the balloting list, you should be able to contact daniela.matthews@nace.org.
To me there is so much evidence to show that the use of the “ON” -850 mV or more negative criterion (even without IR drop consideration) is valid. I will be posting some reports from the 1990 revision effort discussing many of the test site results for the PRCI report as well as some information from other companies. Basically, they show that if you can achieve a -850 mV “ON” potential (even without IR drop consideration) you can also achieve the 100 mV of polarization. I have also sent this information to Neil Thompson of DNV who is involved in the new PRCI study and report on whether the -850 mV “ON” criterion is valid. If you company is a member of the PRCI, please get involved.
I think we all understand that nothing is 100% and we can still have external corrosion in some cases even if we meet or exceed all criteria. Please pass along any data that may help the PRCI or TG 360 committee on their important missions. You can send it directly to the committee(s) or you can send it to me and I will forward it.
Many countries around the world will be relaxing this time of year because of the various holidays, especially in North America, but we must keep alert and provide the needed information to help this committee provide the industry with the best documents and reports possible. Without your help, they will not achieve that goal.
I am hoping that the changes to this new ballot will be allow us to all feel much more comfortable with what is written. Many are concerned about the regulatory implications in the various countries of the original proposed criteria. We will see what changes, if any, are in the new revision.
We need everyone who signed up to vote to vote! This is a critical document to the pipeline industry. No matter what your vote, please vote. Those who are not on the voting list, but have comments or issues you can pass those along to me and I will post them on the blog. I will also help anyone who is not sure how to word their comments with suggestions if there is a need.
I will pass along my thoughts of the new revision after it comes out for balloting. We also encourage others to make comments, no matter what your vote may be. We need to hear everyone’s opinion! Not just mine. Not just negative voters. Sharing information and concerns is how we are going to learn and make an educated decision.
Again, I will think the committee and all others who have worked so hard on this matter. We all want the same thing, a reasonable, sound document that works to provide the industry with guidance to provide safe, economical and environmentally friendly pipelines for the world’s future energy needs.
Richard Norsworthy
Polyguard Products, Inc.
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