CLOSE INTERVAL SURVEYS

​Qualified, NACE certified, Infinity Corrosion personnel perform the close interval surveys and collect the data to be analyzed by certified experts in the corrosion engineering field. ICG prides themselves on an impeccable safety record, accurate data collection, clear graphical data presentation, timely final reports, professionalism, and building relationships that allow us to work closely with all levels of an organization. 

Why do Close Interval Surveys?

 

Annual surveys can be insufficient to judge the true condition and cathodic protection in a specific area. A measurement at a test station could indicate sufficient protection, but 10 feet away, another measurement distanced from the test station, could indicate poor coating or insufficient protection along the pipeline.

The Close Interval Survey (CIS) employs an above ground diagnostic test that can be used for identifying:

  • Protection levels

  • Pipe corrosion activity 

  • Interference

  • Galvanic corrosion cells

  • Coating damage

  • Influence of AC grounding/mitigation installations

ICG applies different close interval survey methods to assess a variety of utilities and industries, ensuring you get the maximum potential out of your system. The various survey types include:

 

  • Native/Depolarized Pipe-to-Soil Potential Survey - Can be used prior to the activation of a CP system for a new pipe and can later be used to evaluate the 100mV polarization CP criterion. These surveys also establish a baseline for assessing the performance of a CP system after it has been energized. 

  • "ON" Pipe-to-Soil Potential Survey - Useful in determining the effectiveness of a cathodic protection system along segments of the pipeline where CP current sources cannot be interrupted. 

  • "ON/OFF" Pipe-to-Soil Potential Survey - The interrupted CIS allows for cathodic protection "ON" and instant "OFF," or polarized potentials measurements, to be recorded. Cathodic protection in all areas surrounding the pipeline is interrupted at a pre-established interval using remote monitoring units. 

 

 

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Close interval surveys (CIS) are useful in identifying and assessing properties of different cathodic protection systems being used to protect your infrastructure. 

 

  • Galvanic Anodes

  • Distributed Linear Groundbed

  • Deep Well Groundbed

  • ​Surface Groundbed​

ICG uses data collected during a CIS to evaluate: 

 

  • Groundbed Influence

  • Different Coating Types

  • Coating Qualities

  • Insufficient Protection Levels

  • Interference from Foreign CP Systems or Shorts

  • ​Baseline for Assessing CP System​

AC Close Interval Surveys can be useful in determining if AC interference is present on a pipeline. 

 

Only doing annual test station monitoring as part of cathodic protection surveys may not give an accurate overview of AC voltage peaks, depending on where the test station is located. Doing a CIS allows us to capture those areas where voltage peaks may be present. Single annual measurements also miss the variability of measured AC voltages. AC voltages fluctuate throughout the day due to power line loading. When a CIS is completed over most of a day, the AC voltage fluctuations are able to be captured more effectively. 

 

AC Gradient Control Grounding Mat Assessment

AC surveys are also useful in examining test station AC gradient control grounding mats in use near EHV powerlines. These grounding mats protect technicians performing work at test stations located near a high voltage power line. 

Close interval surveys are effective at assessing different coating types from bare steel to mortar coated and lined concrete cylinder pipe. 

 

 

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