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Pipeline Current MapperPCM

Radiodetection PCM

Electromagnetic AC attenuation and ACVG

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PCM Application

• PCM will find:

– Coating defects (holidays)

– Shorts to other structures

Radiodetection PCM

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Transmitter

• High power output

(150 Watts)

• Very low frequency to – increase range– reduce coupling to other

services– reduce field distortion

Radiodetection PCM

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Transmitter

• Powered from a transformer/rectifier site.

• From either rectified DC (20 – 50 V) or 110/240 VAC.

Radiodetection PCM

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PCM Receiver• Identifies signal

from Transmitter• Converts to Current• Log to 400 records

and download to PC

• Connect to GPS

Radiodetection PCM

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A-frame

• Pinpoint holidays

• Known as ACVG

• ...but SAME results as DCVG.

Radiodetection PCM

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Transmitter Connection• Typical Transmitter

to pipe connection• Provides a perfect

pipe connection point

• Anode provides perfect ground connection point

Radiodetection PCM

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Transmitter Connection

• Disconnect Rectifier

• Use same connections to connect the PCM transmitter

Radiodetection PCM

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Transmitter Connection

Radiodetection PCM

• Always direct connect• Always use an independent ground

- Anode Bed- Ground Stake- Across an insulator?

• Always have a map of the facility• Never use another utility as the ground

return.• Never assume anything.

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Radiodetection PCM

• Locating Shorts

- First signal loss may not be the short.

- There may be more than one short.

- There may be an unknown source.• Locating Coating defects

- Take readings at the same intervals.

- Make sure PCM and boot is perpendicular to the pipe.

- Hold unit steady and upright when reading current.

• You do not always have to connect closest to the suspected short or coating defect.

• More is not always better.

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Setting the Transmitter• Three settings

available– ELF (4+98 Hz)– ELF + CD (8 Hz)– LF (512 H z) +

CD

• Normal set to ELF + CD

Radiodetection PCM

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Setting the Transmitter

• Set Current switch to desired current

Radiodetection PCM

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Taking Current Readings

• If ELF and arrows selected on Tx then select ELF on the RX

• Locate pipe in conventional way

Radiodetection PCM

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Taking Current Readings• Hold the

Receiver Steady on the ground and press the PCM Key.

• Current is displayed after ~ 4 s

Radiodetection PCM

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Taking Current Readings

Radiodetection PCM

• Unit automatically performs steps:1. narrow band signal processing measures

4 Hz signal (magnetometer);

2. proceed to calculate depth (twin aerials);

3. calculate current;

4. determine CD (using 4 Hz + 8 Hz shift).

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Current Direction• Indicates which direction the Current is flowing

– Aids fault analysis

Radiodetection PCM

Transmitter

short

target line

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Radiodetection PCM

Methodology using PCM for Current Surveys

• Use an independent ground and try to mimic your CP circuit when possible

• Make sure rectifiers are not influencing the signal (turn off AND disconnect if necessary)

• Isolate your circuit whenever possible (disconnect bonds for better surveys)

• Take readings at equal distances and record your distances• Every 50 feet is a good standard (others can be used dependant on

location)• Use it as a macro tool and depth of cover tool (use A-frame for micro)• Look for anomalies with more than a 5% change normally• Make sure unit is upright and perpendicular to the pipe• Use the peak mode. Check peak and null readings and verify depth

when readings are suspect.• Take multiple readings in one location if you suspect the accuracy.• Know what is in the area of your pipe and what it is connected to it

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Datalogging

• 400 records can be stored.

• Records can be:– reviewed on PCM – downloaded to a PC

• Records can be viewed on Excel

Radiodetection PCM

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Datalogging

Radiodetection PCM

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TransmitterA-Frame

A-frame

Radiodetection PCM

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A-frame

Radiodetection PCM

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Radiodetection PCM

PCM with A-frame for Alternating Current Voltage Gradient Surveys • Used as a micro and a macro survey tool

• Can be used in various soil conditions but ground contact of the probes will affect the readings

• Rectifiers generally do not influence the ACVG survey

• In areas of high interference or where current survey does not give you answers, ACVG can still be used with more success

• Know what is in the area of your pipe and what is connected to it

• Larger holidays can mask smaller ones until the larger holidays have been repaired

• PCM displays A-frame readings in db or decibels. Remember every 10 db higher is twice as large

• Metal to dirt contact and soil resistance (not necessarily size of holiday) is what affects the db readings

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ACVG Methodology

Radiodetection PCM

• Use an independent ground and try to mimic your CP circuit when possible

• Take readings parallel and along the pipe. When you see an arrow reversal go perpendicular to the pipe and make sure arrow reverses over pipe

• You do not have to be right on top of the pipe when surveying

• On concrete and asphalt use wet sponges or rags on the probes or wet the ground around the probes.

• Take readings at equal distances usually about every two to three steps

• Use the largest db reading seen around the anomaly for you records

• Record all faults seen with db readings and footages or GPS coordinates.

• Once done, anomalies can generally be categorized into 4 areas–80db – 100db – large

–65db – 80db – medium

–50db – 65db – small

–50db and below – very small

LOCAL CONDITIONS DETERMINE WHAT IS A DIG!

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Radiodetection PCM

Graphing in Excel and Data Interpretation

Corpoven Tacoa

0

500

1000

1500

0 200 400 600 800

Distancia (m)

Co

rrie

nte

(m

A)

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Radiodetection PCM

Tramo II - K 0+510 al K 0+

0

100

200

300

400

500

600

700

800

0 200 400 600 800 1000 1200 1400 1600 1800

Distancia en mts.

Co

rrie

nte

PC

M (m

A/d

B)

Datos de campo Variación en dB

Graphing in Excel and Data Interpretation

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Radiodetection PCM

Graphing in Excel and Data Interpretation

Current Attenuation & Depth

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100

200

300

400

0 200 400 600 800 1000

Distance (m)

PC

M C

urr

ent

(mA

)

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100

200

300

400

De

pth

(m

)

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Radiodetection PCM

Gas Industrial de Monterrey

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50

100

150

200

250

0 50 100 150 200

Distancia (m)

Co

rrie

nte

(m

A)

Graphing in Excel and Data Interpretation

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Radiodetection PCM

Graphing in Excel and Data Interpretation

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Radiodetection PCM

AC Current Drop

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500

1000

1500

0 20 40 60 80 100 120

Distance (yd)

PC

M C

urr

ent

(mA

)

Graphing in Excel and Data Interpretation

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Radiodetection PCM

Graphing in Excel and Data Interpretation

333”

1” copper water service

2” Gas Main

3”

2”

350ma

35m

a32

5ma

201m

a

95ma 265 ma

358ma

561m

a

Pipeline Current Mappertransmitter with an output of 600milliamps set-up across a gasmainline insulator

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0m

a95

ma

Wa

ter

Ma

in

N

location of gasmain andwaterline short

Pa

ve

d S

tre

et

Pa

ve

dS

tre

et

Paved Street

Paved Street

Typical PCM Mapping Survey

Radiodetection PCM