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An additional tool for integrity monitoring. (Optical Remote Sensing).

The current arsenal of integrity monitoring tools may not be adequate to successfully meet the requirements of the recently passed integrity monitoring legislation. Pipeline Integrity Management in High Consequence Areas This legislation potentially affects more than 650 natural gas transmission pipeline operators some of these companies have pipelines that are not easily tested with current techniques such as pigging el hydrostatic testing. The cost to dig up lines in high consequence areas (HCAs) for hydrostatic testing or direct assessment may be cost-prohibitive.

In addition, current inspection tools may not be adequate to effectively monitor all types of pipeline degradation. According to Bennie Barnes, Manager, West Pipeline and Corrosion Services, El Paso Pipeline Group, "conventional magnetic flux leakage (MFL) in-line inspection tools, the most prevalently used inspection tools, do not have an adequate ability to detect stress corrosion cracking or other longitudinal cracking due to the orientation of the magnetic field, and therefore, other technologies, including leak detection tools, are a must in the arsenal of integrity assessment tools."

This article introduces an additional tool for integrity monitoring--optical remote sensing. New technology is needed to effectively and non-destructively meet the requirements of the new integrity management legislation in terms of reduced cost and time required to validate the integrity of the nation's high consequence natural gas pipelines. The optical remote sensing system, duoThane, provides non-destructive, rapid and cost-effective natural gas integrity monitoring from ground-based platforms.

Ophir Corporation of Littleton, CO has developed the sensing system to independently and simultaneously detect methane and ethane, the primary constituents of natural gas. Ophir has developed this system to address the current and future demands of integrity monitoring. The system has sufficient speed and sensitivity to enable cost-effective stationary surveys over natural gas transmission pipelines. At a fence line monitoring distance of 600 meters, duoThane's detection sensitivity is 50 ppb for methane and 33 ppb for ethane.

The system was recently demonstrated on a transmission pipeline operated by Williston Basin Interstate Pipeline Co., Inc., a subsidiary of MDU Resources Group, Inc., in Glendive, MT. The test results demonstrated the ability of the sensor to independently detect and quantify methane and ethane in Class 1, 2 and 3 leaks. The system demonstration was performed for the Environmental Protection Agency, Phase II Small Business Innovation Research program. The system is shown in Figure 1. An example of the gas measurements is included in Figure. 2

A ground based demonstration of the sensor is slated for early this year for El Paso Pipeline Group. An Alaskan liquid pipeline services company is also interested in a field demonstration for the ground-based detection of ethane over crude oil pipeline.

The system is also being evaluated for airborne remote sensing of natural gas pipeline leaks through a Department of Energy grant. Ophir has teamed with Williston Basin Interstate Pipeline in the assessment and testing of the sensor using portions of its pipeline network for airborne flight test demonstrations.

Tire sensor employs the optical technique of Active Gas Correlation Radiometry (AGCR). AGCR is a method of detecting trace gases using an active source and an optical correlation detection method. The optical correlation hardware compares the spectra of the gas of interest to that of the gas in the region under inspection. The AGCR technique has the advantage of achieving a much longer measurement path length over that of ambient thermal gas correlation radiometers. More importantly, the AGCR technique does not require laser sources, but instead uses broadband illumination.

This makes the technology significantly cheaper to manufacture and caster to use. Moreover, a single broadband optical illumination source can he used for multiple trace gases. Typically, lasers that are sufficiently narrow to perform trace gas spectroscopy cannot he tuned over a broad spectral region. Thus, a different laser source is generally required to measure each trace gas species. This becomes very expensive and cumbersome. The AGCR technique does not suffer this limitation due to the broadband nature of gas correlation spectroscopy.

The benefits of this remote sensing system are twofold: improved pipeline safety, and reduced natural gas industry pipeline operating costs. The system provides a short term and cost-effective solution to costly integrity monitoring inspections necessary to comply with the newly legislated integrity management regulations. Optical remote sensing of high consequence areas (HCAs) is a cost-effective alternative to the current inspection and testing techniques.

Ophir's integrity monitoring sensor can effectively demonstrate in real time the integrity of lines in HCAs in a non destructive and non-invasive manner. Thus it provides another tool to supplement currently used techniques at a low cost.

The system reduces the number of "false positive" integrity compromises. A "false positive" compromise (or false alarm) is an indication of a leak which cannot he re-confirmed or detected by the integrity team. The current industry standard technology for verification of a leak (the flame ionization detector (FID), cannot distinguish between combustible gases. As a consequence, FIDs produce false alarms whenever they detect a combustible gas that is not natural gas. Numerous combustible gases exist in industrial and residential areas including: propane, butane, concentrations of automobile exhaust, and numerous volatile chemicals Ophir's system can separately and uniquely identify both methane and ethane. This technique can reject all other trace gas species.

The ability to uniquely identify methane and ethane significantly reduces the false alarm rate and provides the capability to verify the actual integrity compromise of a pipeline. Methane has natural and man-made sources. It is generally present within the free (and clean) atmosphere at the 1 to 2 parts-per-million (ppm) level Localized concentrations may he significantly higher due to vegetation, automobile exhaust, "swamp or sewer" gas, etc. Ethane, on the other hand, has no man-made sources. It exists in the free atmosphere at the 2 parts-per-billion (ppb) level. As a consequence. ethane is a superior indicator of the presence of natural gas since it comprises from 1 to 20 percent of natural gas, has no man-made sources, and has an extremely low natural background concentration.

The second benefit is that this inspection method offers a large cost savings to the natural gas industry. Optical remote sensing of the pipeline can be accomplished without excavating the pipe. Hydrostatic pressure testing and direct assessment both require that significant sections of pipe be excavated at a tremendous cost to the industry. In addition, much of the existing pipeline within the U.S. can not be pigged, Replacing this pipeline with newer, "piggable," pipeline is cost prohibitive. Thus, optical remote sensing offers a cost effective alternative means for pipeline integrity monitoring for vast sections of the U.S. natural gas pipeline infrastructure.

Furthermore, it is a system that can be left in place along the line and monitored remotely. This would reduce the man-hours spent in the field performing visual inspections. In addition, this method can be used to augment the current integrity monitoring tools where they cannot adequately detect longitudinal and stress corrosion cracking. This sensor can be used ill conjunction with current techniques to provide an additional level of certainty that a line is not compromised.

Authors: Lisa Spaeth is director of business development at Ophir Corpora-tion. has diverse work experience focused on technology development and transfer. Her industry focus areas have included a power and gas infrastructure engineering and design company, a contractor for the Department of Energy, the Colorado School of Mines and a major military/aerospace company. She has a BS degree in chemistry and an MBA from the University of California at Irvine. She call be reached at (303) 933-2200 or at lisas@ophir.com.

Martin O'Brien has been with Ophir for over 14 years and now serves as a vice president. He holds patents covering optical technologies, including: novel laser systems, optical remote sensing, infrared radiometers and optical methods for measuring atmospheric trace gas concentrations. He received his BS degree in engineering physics, with honors, and a minor in geophysics from the Colorado School of Mines. He call be reached at (303) 933-2200 or at martino@ophir.com.
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Title Annotation:Ophir Corp. develops optical remote sensing system to meet requirements of recently passed integrity monitoring legislation
Author:Spaeth, Lisa; O'Brien, Martin
Publication:Pipeline & Gas Journal
Geographic Code:1USA
Date:Mar 1, 2003
Words:1330
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