Close Interval Survey

Close Interval Survey Pipeline Locating
A Close Interval Survey is used to determine the effectiveness of the Cathodic Protection System by measuring the Pipe-To-Soil potentials along the pipeline between test stations, and to ensure they are performing up to NACE SP0169 specified standards. Close Interval Surveys are sometimes referred to as Close Interval Potential Surveys. When practical, interrupted surveys are use to measure the IR-drop free, Instant Off, potentials.

The primary steps taken when performing a Close Interval Survey are:

  1. Pipeline Locating

    Allied Corrosion Industries' field survey specialists utilize only the most modern pipe locating equipment when locating the centerline and depth of a pipeline. This includes the use of locators that have the capability of using both null and peak response locating technology. Allied's modern locating equipment routinely includes locators that permit both conductive and inductive signal reception, and which also incorporates multiple frequency propagation.

    This equipment insures comprehensively coverage of the entire spectrum of locating frequencies and their different associated responses. This permits Allied Corrosion Industries' engineers to accurately interpret the locator's responses prior to any excavation activities to insure excavation dollars are not wasted needlessly. The locating equipment responses are routinely stored in data logging storage devices, which includes the exact GPS location of the data being stored. This capability allows our engineering staff to properly analyze the data and to return back to a location if additional investigation is required.

    Allied Corrosion Industries is dedicated to providing the most accurate information possible to their pipeline clients. We makes every decision with the main thought process of optimizing the client's budget dollars so that wasteful spending is eliminated.

  2. Potential Measurement

    Close Interval Survey Potential Measurement

    Allied Corrosion Industries' field-proven pipeline Direct Assessment specialists are fully trained and Operator Qualified in the technology of taking and efficiently recording Close Interval Survey pipeline potential data.

    Some of the typical Close Interval Survey data sets that Allied Corrosion routinely collects are native (un-polarized) potentials, polarized "on" potentials, and instant "off" IR-drop free potentials. The potential data sets are tagged with sub-meter accurate GPS locations, along with major surface physical attributes, which are encountered along the pipeline route, i.e. roads, creeks, fences, power lines, etc.

    When rectifiers are to be interrupted, Allied Corrosion Industries' survey team can accommodate any timing specification that the pipeline owner may require. We are also well versed in handling telluric current interference that typically affects the accuracy of CIS potentials. Allied Corrosion owns and utilizes all the major potential data management software programs. This allows us to furnish potential data sets that can be directly imported into the customer's data base, thus eliminating the requirement of manually entry of data.

    Consequently, when accurate potential data is a primary consideration that can be easily imported into the customer's data base, Allied Corrosion Industries' Closed Interval Survey services are the first choice of the pipeline owner/operator.

  3. Clean Up

    Wire Picking
    Allied Corrosion Industries' personnel embrace the strategy that the job is not finished until the ROW is free of all survey materials. This includes the removal of all making flags, survey wire, crew trash, and/or any other materials used during the survey. Allied takes pride in ensuring that the ROW is left in a cleaner state than before the survey was initiated.

    Our crews have over 20 years experience and include NACE Certified CP Engineers, Technicians and Testers. We have performed Close Interval Potential Surveys on over 6,000 miles of pipelines throughout the United States. Our goals of quality, safety, and on time delivery are reflected in our work and performance.

Allied Corrosion provides a variety of field services and surveys.  These are an important component of a complete pipeline integrity program.

Find out about our other Field Services

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Voltage Range
Relative Position
Least Noble (More Anodic)
-1.60V to -1.67V
-1.00V to -1.07V
-0.93V to -0.98V
Aluminum Alloys
-0.76V to -0.99V
-0.66V to -0.71V
Mild Steel
-0.58V to -0.71V
Cast Iron
-0.58V to -0.71
Low Alloy Steel
-0.56V to -0.64V
Austenitic Cast Iron
-0.41V to -0.54V
Aluminum Bronze
-0.31V to -0.42V
Brass (Naval, Yellow, Red)
-0.31V to -0.40V
-0.31V to -0.34V
-0.31V to -0.40V
50/50 Lead/Time Solder
-0.29V to -0.37V
Admiralty Brass
-0.24V to -0.37V
Aluminum Brass
-0.24V to -0.37V
Manganese Bronze
-0.24V to -0.34V
Silicon Bronze
-0.24V to -0.30V
Stainless Steel (410, 416)
-0.24V to -0.37V
(-0.45V to -0.57V)
Nickel Silver
-0.24V to -0.30V
90/10 Copper/Nickel
-0.19V to -0.27V
80/20 Copper/Nickel
-0.19V to -0.24V
Stainless Steel (430)
-0.20V to -0.30V
(-0.45V to -0.57V)
-0.17V to -0.27V
70/30 Copper Nickel
-0.14V to -0.25V
Nickel Aluminum Bronze
-0.12V to -0.25V
Nickel Chromium Alloy 600
-0.09V to -0.15V
(-0.35V to -0.48V)
Nickel 200
-0.09V to -0.20V
-0.09V to -0.15V
Stainless Steel (302, 304, 321, 347)
-0.05V to -0.13V
(-0.45V to -0.57V)
Nickel Copper Alloys (400, K500)
-0.02V to -0.13V
Stainless Steel (316, 317)
0.00V to -0.10V
(-0.35V to -0.45V)
Alloy 20 Stainless Steel
0.04V to -0.12V
Nickel Iron Chromium Alloy 825
0.04V to -0.10V
0.04V to -0.12V
0.20V to 0.07V
0.20V to 0.07V
0.36V to 0.19V
Most Noble (More Cathodic)

Primary voltage range for material
Voltage range in crevices or stagnant and poorly aerated water