CIS & DCVG Field Crews have to be Well Trained or the Field Data is Worthless

Wikipedia also states:

In theory, a standard analogue electronic multimeter could be used to perform a DCVG survey, but in practice it would be very difficult to take accurate readings and assess the direction of the voltage gradients correctly. A digital multimeter is completely unsuitable because of the difficulty in quickly assesing the direction of the voltage gradient. Specially designed DCVG meters are available, which have bespoke voltage ranges, specially designed transient response, rugged cases and (usually) a centre-zero meter movement for ease of use. The NACE method requires the measurements to be made using a pair of copper-copper(II) sulfate electrodes rather than simple metallic probes. In addition, the Cathodic protection is switched on and off repeatedly using an electronic switch commonly referred to as an "interrupter". Thus, two voltage readings (the "on" and "off" potentials) are taken at each fault position. Counter-intuitively, it is actually the "off" potential (measured with respect to remote earth) which is regarded as more indicative of the effectiveness of the CP applied to the pipeline. Standard surveyor's kits of DCVG equipment are available, together with training courses and software to organise and interpret the survey data.

Pipelines which do not have any form of CP may be surveyed by using a temporary DC supply and anode bed. Long pipelines frequently have more than one DC supply for their CP, requiring a number of synchronised interrupters to perform a survey. DCVG surveys are often combined with other techniques, such as CIPS and soil resistivity as part of a comprehensive corrosion protection program.

Performing a DCVG survey is relatively simple - students or recent graduates are frequently employed to collect the data. Interpreting the results is a little more complicated and this task is usually performed by a specially trained corrosion engineer.

DCVG surveys may be performed by pipeline companies themselves or, more usually, by independent specialists.

Retrieved from "http://en.wikipedia.org/wiki/DCVG"

Categories: Corrosion prevention

If one is doing the sloppy DCVG, then one doesn't need to have trained person collecting the field DCVG data. However, any Corrosion or Cathodic Protection Specialist knows that if the field data is sloppy then even the most experienced and well trained corrosion expert in an air conditioned office cannot make bad field data good. My guess is that the person that wrote this article maybe connected to Cath-Tech which is an Canadian manufacturer of I believe to be sloppy DCVG equipment. In CIS (close interval pipe to soil potential survey also referenced as CIPS) as well as DCVG the pipeline operator gets what is paid for. If the pipeline operator paids for sloppy CIS and DCVG, then the pipeline operator gets sloppy field data that is difficult to analyze and use to make sound pipeline integrity decisions. I have been asked in the past to analyze hundreds of miles of sloppy CIS data. I was doing nothing else during the analyze of the sloppy CIS data than making educated guesses as to what the field crew did wrong when they collected what was worthless data that couldn't be used to make any sound pipeline integrity decisions.

In order for the field data to be usable, the field personnel have to be well trained and experienced as any pipeline operator knows and NACE International does make it clear that one cannot take some college kid with no training and put him in the field and get any valid CIS and DCVG data that can be used to make sound engineering decisions on pipeline integrity.

The best CIS and DCVG field data comes from experienced personnel who are extremely highly trained in how to do CIS and DCVG field data collection. This remark in Wikipedia is not only not true but silly.