DETECTION Professional Issue 3
A publication of SENSIT Technologies
DAMAGE PREVENTION UTILITY LOCATING:
EM, GPR AND ULTRA-TRAC APL
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President’s Message Welcome to 2016! Wow, it seems like just yesterday we were working to finish 2015. Last year was a fantastic year for SENSIT Technologies and I am truly grateful to both our long time, loyal customers as well as the many new ones that were introduced to SENSIT products last year. Everyone at SENSIT knows the importance of their job and how it ultimately can effect yours. I also know that regardless of every effort to build perfect products, there can still be surprises. Our dedicated team in Customer and Technical Services are ready to answer questions and provide product and application support. Equally important, they constantly communicate the trends they hear from you to our engineering team. This process insures continuous improvement to meet our objective of zero defects. 2016 looks to be another exciting year at SENSIT Technologies. We are adding resources toward the development of new innovative products as well as reviewing our legacy products to improve your field experience. Since last fall, we added four new engineers to our global staff as well as hired a new Director of Engineering, Kurt Stefans. These new resources will enable us to meet the pace of changes in deployable technologies for the future. J. Scott Kleppe President and Chief Executive Officer
Another recent hire is Adam Zeciri who is SENSIT’s new Product Manager for our growing Locating Products business. Adam brings more than 15 years of experience in underground utility locating and certifying utility and contractor locate personnel. Significant enhancements have recently been made to our Ultra-Trac APL (acoustic pipe locator). Adam will assist clients in understanding how to implement this unique product to find untraceable underground piping systems. He is also responsible for the feature article in this edition which compares the different technologies available today to locate underground utilities. Thank you again for your business and taking the time to read Detection Professional. We hope you find the information valuable. Please free to send this edition to others and of course, let us know if you have any suggestions or comments. All the best,
J. Scott Kleppe President and Chief Executive Officer
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Feature Article
Utility Locating: EM, GPR and ULTRA-TRAC APL
Introduction to Utility Locating No matter the technology used to locate buried pipes and cables today, there is no single tool that can do it all. Just as a carpenter’s tool box consists of application-based tools like the hammer, chisel and screwdriver, the role of the utility locator also calls for more than one tool to be effective in the field. To fully understand what sets these different tools apart and when a specific tool should be selected over another, one must first understand the applications and limitations of currently available locating equipment. Today, the most commonly used methods to locate buried infrastructure are electro-magnetic (EM), ground penetrating radar (GPR), and acoustic. This article will highlight the technical limitations of each technology and in the process, what sets the Sensit Ultra-Trac Acoustic Pipe Locator apart as a truly essential tool for the locator’s toolbox.
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DETECTION PROFESSIONAL • Issue 3
Electromagnetic Utility Locators In 1931, Gerhard Fischer invented the first handheld utility locator for commercial use, to primarily locate buried metallic pipes and cables. Electro-magnetic (EM) pipe and cable locators use electricity to create a magnetic field to trace the path of buried metallic pipes and cables. EM locators can only detect metallic pipes, cables and wire. They are commonly called conventional locators, due to their wide spread popularity and use. Conventional EM utility locators have 2 main parts: the transmitter and the receiver. The transmitter functions as a miniature power plant and is used to transmit alternating current to energize a metallic pipe, cable or wire. The byproduct of alternating current flowing on a metallic conductor is a magnetic field that may be detected by the receiver.
EM Limitations - Other metal present near the target line will cause
Los An ge les
Santa Fe
Alb uquerq
ue
AZ
San Diego
NM
Ph oeni
x
Yum a
Tu cson Las Cruces
distortion, causing error in the reading. This could be anything metallic; such as a parallel utility line, a metal building or a vehicle. - EM locating equipment can only be used to locate metallic utilities. It cannot be used to find non-metallic lines unless a tracer wire is present (for plastic or concrete-asbestos pipe, for example) and is metallically continuous. - EM locating equipment cannot tell what type of utility is being located. The operator must verify the utility type by either potholing or tracing the utility line structure to structure.
and finally clay. As shown in the map below, most areas of the United States do not have optimal soil conditions for the effective deployment of GPR. El Paso
Ground-Penetrating Radar Suitability Map Bellingh
am
Seattle Tacoma
WA Spokane
Yakima
Portlan
Great Falls Missoula
d
Grand Forks
MT
Salem
ND
ME Bangor
MN Bismarck
Eugene
Fargo
Duluth n
Billings
NH St. Cloud
d
Eau Claire
Minneapolis
Reno
Sacram
NE
Salt Lake City
NV
Bristol
Iowa City
Chicago
Cleveland
Topeka Lawrence
KS
Pueblo
100
150
Baltimore
n Washingto DC
Dover
DE
Parkersburg
WV
Columbia
Kansas City
VA
Huntington Charleston
St. Louis
Richmond Louisville
MO Evansville
Lexington
Lynchburg
Norfolk
Roanoke
KY
Owensboro
Las Vegas
Wichita
CA
Springfield
WinstonSalem High Point
Johnson City Clarksville
Santa Fe
OK
Albuquerque
AZ
San Diego
TN
Tulsa
Jackson
Fort Smith
Spartanburg
Huntsville Decatur
Columbia
Sumter
SC Atlanta
Gadsden
Pine Bluff
Rock Hill
Greenville
Chattanooga
Memphis
AR Little Rock
Lawton
Charleston
Birmingham
Macon
AL
MS
Dallas
Monroe
Shreveport
NC Fayetteville
Charlotte
Fayetteville
Oklahoma City
NM
Phoenix
Durham Raleigh
Knoxville
Nashville
Los Angeles
Las Cruces
Kilometers
n
Wilmingto
MD
Wheeling
Columbus Dayton
Cincinnati
Bloomington
Tuscaloosa
25 50
hia
Philadelp Pittsburgh
Muncie Anderson
Indianapolis
Terre Haute
St. Joseph
Colorado Springs
Lubbock
0
n
Trenton
Akron
OH IN
IL
Denver
Tucson
Environmental Factors The dielectric constant of the media or substrate being scanned determines the amount of signal that is absorbed by the substrate through attenuation. Because soil type determines this factor, soil conditions must be optimal for GPR to work. Soil moisture content greatly affects the GPR signal; in general, dry soil is better than wet. Also known as permittivity, the dielectric constant is frequency dependent for GPR. The higher the frequency, the better the resolution with shallower depth penetration. Conversely, the lower the frequency, the better the depth penetration with lower resolution. The size and material of the target line will also impact the ability to be seen using GPR.
Brockto nce
Newpor
NJ
PA
Fort Wayne
Davenport
Lincoln
Boulder
CO
Boston
RI New Bedford t
New York
Toledo
South Bend
Omaha
Fort Collins Greeley Longmont
UT
Fresno
ter
Provide
CT
ry Waterbu New Danbury Haven rt Bridgepo
Detroit Ann Arbor
Kenosha
Rockford
Cedar Rapids
Des Moines
Cheyenne
Provo
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Jose
Worces
ld Springfie
Buffalo
Flint Lansing
Racine
Janesville
Dubuque
Waterloo
IA
Grand Rapids
Milwaukee
Madison
Sioux City
San
MI
Sheboygan
La Crosse
MA
NY Rochester
Oshkosh Rochester
Sioux Falls
Casper
Logan
Ogden
San Francis co
Lowell
Green Bay
WI
Appleton
Rapid City
Pocatello
WY
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SD
Idaho Falls
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Portlan
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Portsmo
ID
Boise City
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Ground Penetrating Radar The first large-scale application for Radio Detection and Ranging (RADAR) was used during World War II by the British and American military, to detect electromagnetic pulses reflected by aircraft. Ground Penetrating Radar (GPR) was first used to determine the depth of a glacier in Austria in 1929. HAWAII Today, despite its common limitations due to soil conditions, modern use of GPR to locate buried utilities has increased in popularity, due to the ability to find both metallic and non-metallic lines.
Lewisto
VT
Burlingto
OR
GA
Columbus Montgomery
Jackson
El Paso
Albany
Dothan
TX
Hattiesburg
Alexandria
Jacksonville
LA
Mobile
Baton Rouge Austin
Lake Charles
Lafayette
Biloxi Pascagoula New Orleans
FL
Houston San Antonio
Orlando
Tampa
Corpus Christi Fort Lauderdale
Miami
HAWAII
GPR Index
25 50
100
Very High
2
High
Large Water Body
3
Moderate
Not Digitized
4
Low
Urban Areas
5
Very Low
International Border
6
Unsuited
Not Rated
Kilometers 0
1
150
USDA-NRCS. 2009. Ground Penetrating Radar Suitability - US (map). Using ArcGIS, Version 9.2 (Environmental Systems Research Institute, Inc., Redlands, Ca.). National Soil Survey Center, Lincoln, Nebraska. Scale 1:1,500,000. Map projection for continental U.S. using Albers Equal Area, North American Datum 1983 (NAD83). Map projection for Hawaii using Hawaii State Plane NAD83. Map projection for Puerto Rico and U.S. Virgin Islands NAD83.
Water
USDA-NRCS. 2008. Digital General Soils Map (GSM) version 2. Continental United States, Hawaii, Puerto Rico and U.S. Virgin Islands. Soil Data Mart Source (http://soildatamart.nrcs.usda.gov). December 2008 edition. Soil Survey Staff. 2009. NSSC DATA – Ground Penetrating Radar Suitability Index (GPRSI) [data file] - National Soil Information System (Evaluation Draft - 02/2009). USDA Natural Resource Conservation Service, National Soil Survey Center, Lincoln, Nebraska. (http://soils.usda.gov). Current State and Equivalent, TIGER/Line 2008 (cartographic boundary file, tl_2008_us_state.zip). 2008. U.S. Census Bureau. Available FTP: ftp://ftp2.census.gov/geo/tiger/TIGER2008/. [Accessed on February 20, 2009] Urban Areas (generalized cartographic boundary file, ua99_d00_shp.zip ). 2000. U.S. Census Bureau. Available FTP: http://www.census.gov/geo/cob/bdy/ua/ua00shp/. [Accessed on February 20, 2009]
State Line Interstate Highway
USGS. Analytical Hillshade computed from 1 kilometer National Elevation Dataset (NEDS) using the following parameters: 315 degrees altitude, 45 degrees azimuth, and z factor 1x. Prepared by USDA-NRCS-NSSC, Lincoln, NE.
0 25 50
100
150
200
250
Kilometers
200
GPR Index 1
Very High
2
High
3
Moderate
PUERTO RICO & U.S. VIRGIN ISLANDS
20
30
40
The majority of the United States offers moderate to Water low GPR feasibility. Large Water Body
Not Digitized
Source: USDA-NRCS. 2009. Ground Urban Areas Penetrating Radar Suitability - US (Map).
4
Low
5
Very Low
International Border
6
Unsuited
State Line
Not Rated
Kilometers 0 5 10
Interstate Highway
200
The soil type and moisture content definitely matter for GPR to successfully locate buried pipes. Ranked from best to worst: Air, solid ice, rock, sand, silt,
GPR Limitations - Soil type plays a major role in the ability to find pipes and cables using GPR. - The greater the depth, the greater the target utility size needs to be; smaller pipes and cables will not be found using GPR. - Certain types of pipe materials simply cannot be seen by GPR in any soil type, at any depth. - GPR cannot tell the type or material of the buried utility line. Must be verified by potholing or tracing the utility line structure to structure. Continued on next page
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Continued: Utility Locating: EM, GPR and ULTRA-TRAC APL Acoustic Pipe Locator (APL) Originally invented by Gas Technology Institute (GTI), SENSIT Technologies acquired the rights for commercialization and production in 2011. Since the first APL rolled off SENSIT’s production line, many advancements have been made based on input from end users. The latest advancement is the incorporation of a Windows-based tablet to create 3-D image maps of scan data. The APL can be used to find metallic and non-metallic pipes, in any soil type, to depths to 30 feet.
How APL Works With the push of the APL’s scan button, twenty-four pings are delivered into the ground at a single location, known as a slice. A series of slices is known as a scan. A scan must consist of at least 5 slices,
Ground Surface
Reflective Wave
Transmitted Wave
Obstacle (Pipe)
SENSIT Technologies ULTRA-TRAC® Acoustic Pipe Locator (APL) provides an alternative and supplemental method of locating buried pipes. The APL transmits and receives acoustic sound waves and then looks for differences in acoustic impedance in the soil caused by pipes, cables, ducts and other buried infrastructure using a process known as impedance mismatch. The APL is able to locate buried utilities, regardless of material type, broken tracer wire and soil conditions. The chassis, or foot of the unit, houses the battery, electronic components and send-and-receive sensors. Located near the front of the chassis, the actuator sends a series of sound waves, or ‘pings’ into the ground. To the rear of the chassis, dual matched accelerometers receive the sound waves once they have been reflected from a buried pipe, cable, or duct.
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DETECTION PROFESSIONAL • Issue 3
to allow internal software to calculate the location of a buried utility line. A pattern will emerge in the survey, identifying the possible location of a buried pipe. The tablet displays this information to the operator on-the-fly in 3-D. Survey data can also be stored for use as a client deliverable, emailed to a supervisor for verification, or stored for record keeping purposes.
APL Limitations - As with GPR and EM, the operator should have a ballpark idea of where the scan should be taken based on system knowledge and surface indicators - As with EM and GPR, the APL cannot tell what type of facility is being located. The operator must verify the utility type by potholing or tracing the utility line structure to structure.
This contour map, known as ScanView, can be viewed after every scan to better understand the ground profile. Though a single scan is not an adequate search, it can provide important insight based on the strength of the reflected sound waves.
Conclusion Given their inherent limitations, a toolbox consisting solely of conventional EM and GPR locating equipment simply cannot find everything on their own, unless the target utility is metallic, or has an unbroken tracer wire for EM, or soil conditions are optimal for the use of GPR. As the USGS soil map shows, in the contiguous United States, optimal soil conditions for effective use of GPR are few and far between. Pairing EM equipment with the APL enables the end user to find both metallic and nonmetallic utilities, in a broad range of soil types. The Sensit APL provides the operator with an essential tool to locate metallic and non-metallic pipes, cables and ducts, regardless of broken tracer wire and soil type. Its ease of operation, coupled with the ability to display and store scan data in 3-D, makes the APL an excellent choice for anyone trying to find buried pipes, cables and ducts. Utility locators, engineers, surveyors, energy companies and municipalities alike, are currently deploying acoustic locating technology with the Sensit APL. Find out more at GasLeakSensors.com or call us at 1-219-465-2700 to schedule a demo.
The APL’s state-of-the-art 3D Pipe Mapping feature allows users to stack several scans together to obtain a 3D map of the underground topography. This 3D map, including axis control and an interpolation feature, improves resolution and provides quicker and more accurate analysis of the surveyed area.
About the Author
Adam Zeciri Product Manager Utility Locating SENSIT Technologies
Since 1999, Adam has been mapping and locating subsurface utilities in North America. Utilizing conventional land surveying, GPS/RTK, thermal imaging (IR), subsurface and concrete scanning via ground penetrating radar (GPR), electromagnetic induction (EMI), conventional electromagnetic locating (EM), acoustic locating and SPAR utility surveying technologies, Adam has located and mapped buried infrastructure in the United States. He has trained utility locators in EM and GPR since 2007 and instructed locator certification courses since 2009. In addition, Adam has supervised and trained gas leak survey, utility locating, infrastructure mapping, corrosion, utility construction and gas leak repair field crews. He recently trained and qualified operators in over 29 different gas construction, maintenance and repair tasks as a senior technical instructor and OQ evaluator.
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Case Study
Damage Prevention Gas Line Locating with ULTRA-TRAC (APL) Acoustic Pipe Locator
The Client
SENSIT Solution
A Natural Gas utility company with 12,000 miles of natural gas pipelines, serving over 500,000 customers in the western United States.
ULTRA-TRAC® APL was deployed to the survey site. With the assistance of the client, we conducted an acoustic locator survey, in a series of eight foot scans.
The Challenge
To collect the most accurate data for the survey, sixteen acoustic readings were used for each scan. Each “pipe found reading” was marked with white paint
Locating a 3” PVC natural gas pipeline acquired from a railroad company. The line had received several hits from third parties near the survey area. The client needed to find and mark the line to avoid future incidents. Traditional locating equipment failed to find the line, as no tracer had been used during installation.
Results After completing a full series of scans covering a 32x23’ grid area, a pattern developed at 60”, along with an area known to contain fiber optic line. The client used a vacuum excavator to verify the natural gas line location. Conclusion As a result of this success and recognizing the savings they could realize through continued deployment of the APL, the client purchased one unit and expressed interest in several more.
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DETECTION PROFESSIONAL • Issue 3
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3D Pipe Mapping Software
ULTRA-TRAC速 APL (Acoustic Pipe Locator) finds piping systems with missing or broken tracer wire. No system access is required. Gas, water and sewer laterals are easily traced using state-of-the-art acoustic technology. ULTRA-TRAC速 APL is easy to use and locates systems in minutes. The locator works on asphalt, concrete, grass, gravel and soil and finds all types of pipe; metallic, concrete, and plastic. 3D Pipe Mapping Software allows users to access and view a comprehensive collection of data in a graphical format to clearly identify piping systems.
Innovative Detection Solutions www.gasleaksensors.com
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Awareness
Damage Prevention SENSIT Technologies is a proud member of the Common Ground Alliance. CGA is an association comprising approximately 1,500 members covering every facet of the underground utility industry. Founded in 2000, CGA is committed to saving lives and preventing damage to underground infrastructure by promoting effective damage prevention practices. CGA brings together all stakeholders in the industry with a shared responsibility for reducing damage to underground facilities in North America. Participants in CGA include: excavators, locators, road builders, railroads, public works, one call, electric utilities, telecommunications companies, oil and gas distribution and transmission, state regulators, insurance companies, emergency services, and equipment manufacturers.
The CGA provides a forum where these stakeholders can share information and work together to enhance safety, protect underground facilities, and address all aspects of damage prevention. Through its leadership, CGA is making significant, measurable progress in creating a damage prevention culture across North America. SENSIT Technologies actively participates in CGA events and forums and is viewed as a technology leader in the community through its development of the Ultra-Trac APL (acoustic pipe locator) and Ultra-Trac MJL (metallic joint locator).
The 811 Logo is a registered trademark of the Common Ground Alliance.
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DETECTION PROFESSIONAL • Issue 3
APWA UNIFORM COLOR CODE* Each color identifies a specific type of utility. WHITE PINK RED
YELLOW
Proposed Excavation Temporary Survey Markings Electric Power Lines, Cables, Conduit and Lighting Cables Gas, Oil, Steam, Petroleum or Gaseous Materials
ORANGE Communication, Alarm or Signal Lines, Cables or Conduit
BLUE
Potable Water
PURPLE
Reclaimed Water, Irrigation and Slurry Lines
GREEN
Sewers and Drain Lines
*These colors are close approximations of the industry standard.
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