Effectively Using Utility Locating Tools Presented By: Eric Denslow from 2013 Fall Operations Conference
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Effectively Using
Utility Locating Tools
Presented By:
Eric Denslow
from
2013 Fall Operations Conference
1. READ THE STREET
2. DETERMINE BEST METHOD TO APPLY SIGNAL
3. VERIFY TRANSMITTER SIGNAL OUTPUT
4. SCAN THE SEARCH AREA FOR LINES CARRYING SIGNAL
5. IDENTIFY THE TARGET LINE BY EVALUATING ALL INDICATIONS
FROM THE RECEIVER
6. TRACE THE TARGET LINE TO A KNOWN END POINT FOR
VERIFICATION
THE SIX-STEP LOCATE PROCESS
Read the Street
• Begin by searching the job location for visible clues such as:
• Consult maps and drawings from utility companies.
• Understand the job at hand – why are you there?
Fire Hydrants Valve Box Covers Manhole Covers
Pedestals Splice Boxes Pad Mounted Transformers
Overhead Cables Utility Poles Dip or Riser Cables
Gas Meters Meter Pits UG Vaults
Electric Meters Network
Interface Devices
Utility Markers or
Existing Markings
4
The proliferation of power and radio technology has
caused many underground metallic pipes and cables to emit detectable magnetic fields.
Passive
5
Fast Easy Does not identify
Passive
6
However tracking lines to their source can also aid identification.
Passive
7
Passive
Ensure a full grid search is done to detect conductors laid in different directions.
Radiodetection
1. READ THE STREET
2. DETERMINE THE BEST METHOD TO APPLY THE SIGNAL
THE SIX-STEP LOCATE PROCESS
Applying Locate Signal to a Pipe
Direct Connection
• Can use Lower Frequency • Can apply More Power • Allows Better Identification • Allows Better Depth Reading • A Good Ground Makes a Good Locate • Can Control Interference • Can Control Signal Transfer to Nearby Utilities
Applying Locate Signal to a Pipe
Signal Clamp
• No Ground Required • Use Whenever you Can Clamp Around the Pipe • Simple, Fast and Effective • Works well with Different Frequencies and Power Settings
Applying Locate Signal to a Pipe
Induction
• Does not Require Access to the Pipe • Must use a High Frequency • The Closer the Transmitter is to the Pipe the Better • Transmitter Antenna is Directional • Must Keep Distance to Avoid Air Coupling • Risk of Signal Jumping to Other Nearby Lines
PUT A FIELD IN IT.
Alternatives for Non-Metallic Lines
• Detectable rods and Sondes can be pushed through the pipe
• Pinpoint Lines, Blockages or Obstructions
• Best Used in Non-Metallic Pipe
• Detectable by a Locator at Ground Level
1. READ THE STREET
2. DETERMINE THE BEST METHOD TO APPLY THE SIGNAL
3. VERIFY THE TRANSMITTER SIGNAL OUTPUT
THE SIX-STEP LOCATE PROCESS
Which frequency should I use ?
Very Low Less than 1khz Very Long Range No Induction Little "Spillage" Low 1-10khz Long Range Poor Induction Less "Spillage"
High 10-50khz Easy Induction Shorter Range More "Spillage" Very High 50khz+ Short Range Excellent Induction Severe "Spillage"
Characteristics of different frequencies.
Output Verification
A successful connection to the metallic pipe or cable will be indicated by a change in the
transmitter audio or visual indicator. Always make the best possible connection for reliable signal.
mA
mA
Some transmitters display a quality
ground with Solid and Blinking L.E.D. Lights.
Some transmitters display resistance to verify a quality ground.
Newer transmitters display a quality ground with a Volts and mA Reading
1. READ THE STREET
2. DETERMINE THE BEST METHOD TO APPLY THE SIGNAL
3. VERIFY THE TRANSMITTER OUTPUT
4. SCAN THE SEARCH AREA FOR LINES CARRYING SIGNAL
THE SIX-STEP LOCATE PROCESS
After making a connection, sweep a complete circle around a signal source; measure and mark all
occurrences of signal. Repeat to assure accuracy.
Scan Area
Scan Area
Ensure a full grid search is done to detect conductors laid in different directions.
Scan Area
Higher gain or sensitivity settings may show Multiple signals to analyze.
Scan Area
When scanning a low gain or sensitivity setting may result in detection of only the strongest signal.
1. READ THE STREET
2. DETERMINE THE BEST METHOD TO APPLY THE SIGNAL
3. VERIFY THE TRANSMITTER SIGNAL OUTPUT
4. SCAN THE SEARCH AREA FOR LINES CARRYING SIGNAL
5. IDENTIFY THE TARGET LINE BY EVALUATING ALL
INDICATIONS FROM THE RECEIVER
The Six-Step Locate Process
How Do Receivers Read Signal ?
Digital Strength and Bargraph
Digital Strength with Direction Arrows
Audible Tone Simple Meter
Whether the Method is Peak or Null – All Receivers Have a Way to Indicate the Strength of the Signal and Location of the Line
Aerial Responses
Different aerial orientations can be used for different responses.
1 2 3
Signal response
1 2 3
Signal response
PEAK: Receiver Indicates Line Location By Reading the Maximum Response to the Signal
NULL: Receiver Indicates Line Location By Reading No Response to the Signal
Null response in an area with congested plant is often useless and misleading.
Null
Peak response is more reliable. It enables you to measure depth.
Peak response is more accurate in congested areas.
Peak
When the conductors are close together, the magnetic fields can interfere with each other, causing a distorted field which is no longer cylindrical. This can lead to poor locate results and inaccurate measurements.
Distortion
For the most consistently accurate results, remember the 3 P's....
Put the Paint in Peak
1. READ THE STREET
2. DETERMINE BEST METHOD TO APPLY SIGNAL
3. VERIFY TRANSMITTER SIGNAL OUTPUT
4. SCAN THE SEARCH AREA FOR LINES CARRYING SIGNAL
5. IDENTIFY THE TARGET LINE BY EVALUATING ALL INDICATIONS
FROM THE RECEIVER
6. TRACE THE TARGET LINE TO A KNOWN END POINT FOR
VERIFICATION
THE SIX-STEP LOCATE PROCESS
Tracking lines to their source provides verification of utility
identification.
Verification
Verification
• Complete job by confirming visible clues such as:
• Did you consult maps and drawings from utility companies?
• Did you complete your assigned job task?
Fire Hydrants Valve Box Covers Manhole Covers
Pedestals Splice Boxes Pad Mounted Transformers
Overhead Cables Utility Poles Dip or Riser Cables
Gas Meters Meter Pits UG Vaults
Electric Meters Network
Interface Devices
Utility Markers or
Existing Markings
Electronic Marker Locators • Detects up to seven different color coded marker types Power - Red Water - Blue Sanitary - Green Telephone - Orange Gas - Yellow Cable TV - Orange/Black Non-Potable Water – Purple
• Scan mode provides simultaneous detection of all marker types
• Digital signal processor accuracy
Uni-Markers Omni-Markers
Electronic Marker Locators
When excited by any standard marker locator, these passive circuits produce a uniform,
spherical RF field in every direction.
Ground Penetrating Radar
- GPR is the electromagnetic equivalent to a sonar or a fish finder.
- A transmitter produces electromagnetic impulses which are transmitted through the subsurface.
- Reflections occur where the electrical properties of materials change
- These reflections are detected by the GPR receiver and displayed on a monitor.
Example of Radar Data in Receptive Soil Conditions (Gravel / Sand)
Example of Radar Data in Non-Receptive Soil Conditions (Clay)
Questions? Contact me at:
Eric Denslow
Eastcom Associates, Inc.
1214 Route 28 North Branch, NJ 08876
Ph: 908-722-7774
Cell: 609-290-6283
www.eastcomassoc.com
Email: [email protected]
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