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Pre-contoured Contact Wheel for In-line Inspection Tool

IP.com Disclosure Number: IPCOM000250555D
Publication Date: 2017-Aug-02
Document File: 9 page(s) / 656K

Publishing Venue

The IP.com Prior Art Database

Related People

Baker Hughes, a GE company, LLC: OWNER [+2]

Abstract

The current cathodic protection current measurement tool utilizes the contact wheel of the same defined dimensions. The contact wheel features contact elements or probes along the circumference, which can be in a form of bristles, spokes, and other contact elements. There are 8 wheels total installed on most tools. The tool electronics measures the difference in voltage between the front and rear wheels.

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            Pre-contoured Contact Wheel for In-line Inspection Tool

Background

This idea for a Pre-contoured Contact Wheel for In-line Inspection Tool was proposed in the previous research project to mitigate the background noise in voltage of direct current (VDC) measurements associated with induced tribology effect. The novelty of this idea is that the wide contact wheel with pre-contoured outer diameter is proposed for measuring the CP voltage signal inside the pipe wall by establishing the electric contact with the inner pipe wall surface.

Abstract

The current cathodic protection current measurement tool utilizes the contact wheel of the same defined dimensions. The contact wheel features contact elements or probes along the circumference, which can be in a form of bristles, spokes, and other contact elements.

There are 8 wheels total installed on most tools. The tool electronics measures the difference in voltage between the front and rear wheels.

Figure 1: General Idea – Wide Pre-contoured Contact Wheel (left to right – current contact wheel utilized on the tool and proposed pre-contoured wide wheel)

Increase the number of sensors in contact with pipe wall by widening wheel and pre-countering it to the internal pipe wall curvature may potentially reduce the background noise of VDC measurements. This is supported by the well-established rule of time-averaging, which is a simple and efficient method of increasing the signal-to-noise ratio (SNR) of a signal (1) (2). This method is applicable to all situations where the signal is stable over several hundred measuring cycles. The signal is registered repeatedly and summed up. Since noise contributes in a probabilistic manner, whereas the net signal always contributes to a signal in the same direction, noise will finally cancel out.

It can be shown that the noise decreases with the square root of the number of repeated measurements (or number of contact elements) that are used to measure the voltage signal at the same time; thus the SNR ratio increases accordingly (3). In other words, if the measurements are repeated 36 times, for example, the SNR increases by a factor of 6.

Figure 2: Improvement in SNR Relative to Number of Measurements (1)

Below are the examples from the literature of a signal obtained from a single measurement and the averaged signal with 36 repeated measurements.

Figure 3: Single from a Single Measurement

Figure 4: Averaged Signal from 36 Measurements

As it can be seen from Figure 3 and Figure 4, the background noise has reduced and the true signal has become more apparent.

In the dry gas environment, the wheel’s contact elements are not surrounded by the natural lubricant, which is present in the liquid pipelines (flowing medium such as oil or refined products). This induces the tribology or triboelectric effects.

Noise is any unsteady component of a signal which causes the instantaneous value to differ from the true value. In electrical signals, noise o...