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DCVG Surveys Training Manual

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1. or Max mV OFF Magnitude and Polarity gt Max mV Max mV ON Max mV OFF Magnitude always positive gt Total mV Magnitude gt IR Magnitude II 9 Polarity Considerations By noting the polarities of the maximum soil to soil potential difference recorded with rectifier current ON and rectifier current OFF at a defect site we can determine the corrosion condition of the defect with the CP system current flowing ON state and without the CP system s impressed current flowing OFF state A positive value for delta V given the polarities of the data probes and their positioning relative to the pipe indicates that net current is flowing to the pipe which is a cathodic condition Whereas a negative value for delta V indicates that net current is flowing away the pipe which is an anodic condition Since we are able to record the polarity of Max mV ON and Max mV OFF we can determine the corrosion condition of the defect both when the CP current is impressed and when the CP current is not flowing to the defect The best case scenario is cathodic cathodic however cathodic anodic is also acceptable since in this case the CP system s impressed current is doing its job ie it is preventing corrosion taking place at the defect site The worst case scenario would be anodic anodic since in this case the defect is not protected even with CP current flowing II 10 In Line Parallel DCVG Survey Technique There is a
2. 6 SECTION HI HOW TO SETUP THE Gx DATA LOGGER FOR DCVG SURVEYS Your Gx data logger will arrive from MCM with the Windows operating system and our pipeline survey application program Gx_ PLS pre installed The survey application will remain installed unless the batteries are allowed to fully discharge Application re installation is an automatic process however during a Cold Boot process please see the Gx Pipeline Survey Data Logger User s Manual for details However your pipeline survey data will always be safe regardless of battery status as these data are stored in a non volatile Flash memory on the Gx HI 1 Gx Data logger Setup for DCVG Surveys Step 1 Double tap on the Gx_PLS icon on the Gx desktop The screen shown below will be displayed Survey Survey Options Help yojvn Wel ce Station Total Dist Last Ref Dist estat lf TBM 22m Step 2 Tap on the Survey button located on the menu bar The screen shown below will be displayed 20 STAA Survey Options Help New Survey Ctri N Continue Previous Survey Ctrl C Finish Survey Ctrl F GUAR Exit Ctr x Beate STW EH zam Under Survey there are several options If this is a new survey not a continuation of a previous survey tap on New Survey The screen shown below will be displayed Enter New Survey Filename 0 500 0 000 Lx J start fe 2 A 251P 21 Step 3 Enter a filename for the
3. Data Dist 0 00 2 50 1 2 5 00 tone Location On Max Y 0 011 0 012 0 012 0 0 013 0 00 2 50 3 00 7 90 ere bone J toe PET 10 47 am 2 The data to be viewed can be selected by entering values in the From and To fields and tapping on the Retrieve button Using the horizontal and vertical scroll bars you can scroll through the collected data A row of data can be deleted by highlighting the row and tapping on the Delete button Multiple rows can also be deleted at the same time Pictures can be viewed and or deleted by first highlighting the location see screen below and tapping on the Pictures button 47 Edit Survey Data Data Alt Quality Ce a Once highlighted the picture can be deleted by tapping on the Delete button or viewed by tapping on the Pictures button Delete Last Readin By selecting the Delete Last Reading option from the menu you can have your last reading deleted without having to go through the Edit Survey Data option Alternatively you can use the Ctrl and D keys to access the function Add Comments You can add remarks comments at anytime on your survey by selecting the Add Comments option and manually entering data on the screen shown below 48 Add Coments f Note asta fe SoA 11 59 4m Alternatively you can use the Ctrl and O keys to access the function Tap on the OK
4. GPS data will be logged automatically at survey flags when either the flag button is tapped directly on the Survey screen or when the push button switch on the designated flag cane is pressed Log GPS at DCP Features If this box is checked GPS data will be logged automatically at Devices or Geo Features when either the Device button is tapped on the Survey screen and a Device reading is logged or when the Geo Feat button is tapped on the Survey screen and a geo feature is registered Log GPS at Sidedrain Anomaly If this box is checked GPS data will be logged automatically when DCVG anomalies are marked as described in our DCVG Training Manual Gx Version Auto Log GPS By tapping on the menu button in the Auto Log GPS field the selections available will be displayed By selecting one of these options you can elect to have GPS data logged automatically at every DCVG reading at every second DCVG reading at every fifth DCVG reading at every tenth DCVG reading or not at all never at DCVG readings 28 DCVG Anomaly Max mV Total mV Ist Reading The last check box on the above screen is actually not related to GPS Options If this box is checked the Max mV voltage recorded at an anomaly location will automatically become the first voltage value used by the data logger s software to calculate the Total mV total voltage gradient Otherwise if this box is un checke
5. a pair of canes reference electrode data probes is illustrated the left hand cane RED handled cane and the right hand cane GREEN handled cane These canes which will be placed on the soil above the pipeline in either the Perpendicular or the In Line configuration see Section II have push button switches on top of the handles so that the operator can trigger voltage recordings on his command at each of the pipeline survey measurement locations as well as at Devices and Geo Features depending on the selections made for cane button functionality during the survey setup process see Section II 1 The canes data probes are connected as shown to the input terminals of the dual probe adapter and the output terminal of the adapter is connected to a 5 pin Data Probe connector on the top side of the Gx 51 Note The left hand reference electrode red handled cane is connected to the dual probe adapter via a black band cable while the right hand reference electrode green handled cane is connected to the dual probe adapter via a red band cable This is important since the right hand reference electrode connects to the positive side of the data logger s voltmeter while the left hand reference electrode connects to the negative side of the voltmeter The terminals on the Gx data logger are illustrated in the figure below Top Side of Gx Data logger Screen Side GPS Antenna
6. another case you might decide to change the Distance Per Readings interval from 2 5 feet to 5 0 feet for example To change survey settings tap on Settings and tap on Change Global Settings View Settings To simply view your setup selections you can tap on View Settings on the above menu Alternatively you can use the Ctrl and S keys Voltmeter To run the stand alone voltmeter either tap on the Voltmeter option on the menu or use the Ctrl and M keys Wave To run the stand alone waveprint generator either tap on the Wave option on the menu or use the Ctrl and W keys Please see section IV 6 below for more information on running the stand alone voltmeter Take Pictures You can run the integrated camera program by either tapping on the Take Pictures option on the menu or by using the Ctrl and A keys Note Several seconds are required to open and close the camera program The Pictures screen shown below will be displayed 40 Pictures No Pictures H Take Pict settings Rename Delete start c ADE 141a To take a photograph tap on the Take Pict button The camera will go through a focusing process and you will see a Ready to Take indication at the top of the screen when you can take a picture as indicated below Ready to Take Auto Day E3 Start k e E ge Y TE 12 47 PM ej 41 At this point press and release the camera
7. automatically If the connection is not established automatically make sure that the connection option on the Gx is USB_ Serial which it should be by default To do so tap on the Start button on the Gx screen tap on Settings tap on Control Panel and double tap on PC Connection If USB _ Serial is not indicated tap on the Change Connection button and select USB _ Serial from the drop down menu Repeat the connection process Step 3 Double click on the ProActive icon on your PC s desktop screen This will open up ProActive s main menu window A window labeled Entire Database will also be seen here The suggested organization of your database is discussed in the ProActive Training Manual Step 4 Click on the Surveys speed button on the main menu bar This will open a window labeled Data Logger Get Pipeline Survey 70 By clicking on the menu button in the Data Logger field you can select the data logger from which you are copying the survey file The various data loggers currently supported by ProActive are offered as choices in the menu list Step 5 Select the Gx Data logger Option Highlight GX in the menu list and make the appropriate Survey Type selection CIS in this case Next click on the Go button This will open up a window labeled Gx Driver Pipeline Survey Note It may take a few seconds for the Dri
8. available NMEA This means that an external NMEA compatible GPS receiver is being used such as a Trimble unit Manual This means that location data will be entered manually when the GPS button is tapped on the survey screen during a CIS MCM Internal This means that the Gx s internal GPS unit will be used a u blox NEO WAAS enabled receiver Select the appropriate choice by tapping on your selection Com Ports When using an external GPS unit NMEA option connected via a serial cable select the COM 1 option which represents the built in serial port located under the flap on the bottom left hand side of the Gx data logger The COM 4 option will be automatically selected when the MCM Internal GPS receiver option is selected 27 Step 13 Select GPS Data Logging Options Only Log Corrected GPS This box should be checked if you only want differentially corrected GPS data to be logged by the Gx data logger on the survey Leaving this box un checked will result in standard GPS data being logged in cases where differentially corrected data are not available Note If this boxed is checked and the unit is not receiving a differential correction message no GPS data will be logged Use GPS Altitude If this box is checked altitude data will be logged in addition to the Lat Long data whenever GPS data are logged Note Altitude data on some GPS units are not particularly accurate Log GPS at Flags If this box is checked
9. button located at the top right hand corner of the keypad You will have the choice of saving the picture or deleting it as indicated by the 4 to Save 1 to Delete indication on the screen below To save the picture press and release the 4 key An example of a saved image is shown below on the Picture screen 42 Pictures 07_13_201008_27_01 Beale oenas As indicated in the above screen the image is given a filename by default which represents the date time stamp for the image The above image for example was recorded on July 13 2010 at 8 27am You can rename the image if you prefer by highlighting the image tapping on the image and tapping on the Rename button You can then enter a new name for the image For example the image above has been renamed Office Desk on the screen shown below 43 Pictures e You can view a larger version of the image by highlighting the image tapping on the image and tapping on the View button You can take multiple photographs at a test site by repeating the process outlined above For example the Picture screen shown below shows two renamed images 44 Pictures Gx Data logger So gt fe D 12 53 Pm If you would like to adjust the camera settings from their default settings you can do so via the Settings button on the Pictures screen For example you can change the size and resolution of the image to be captured t
10. button on the above screen to return to the Survey screen after entering your comments Restart Flags You can reset survey flags by selecting the Restart Flags option from the menu This action will establish your current location as the new zero reference as far as flagging is concerned and zero should be entered automatically in the Last Reference Distance field on the Survey screen Set Graph Scale Rather than having the software auto scale the graph on the Survey screen to accommodate the actual data values logged you can establish the maximum and minimum values for the graph scale in order to restrict the data values to be displayed on the graph To do so you would un check the box labeled Auto Scale on the window shown below and enter specific values for maximum and minimum 49 Maximum 0 500 Minimum ar GPS Status Standard GPS tak PoaBi nsa Tapping on the OK button will return you to the Survey screen SECTION IV TEST EQUIPMENT HOOK UPS FOR DCVG SURVEYS IV 1 How to make Cable Hook Ups for DCVG Surveys The cable connections for DCVG surveys employing MCM test equipment are illustrated in the figure below 50 Pipeline GPS Antenna Dual Probe Adapter z Right Hand Left Hand Cane Use Cane Use Red Band Black Band Cable Cable Cable Connections for Hook Up of MCM s DCVG Survey Test Equipment As can be seen from the above figure
11. of sensitivity compared to the 5 7V Range since DCVG voltages tend to be only in the tens of milli volts range You would then tap on the Save button to record the data at the first test station As an alternative you could press the push button switch on either one of your data probes canes to record the data assuming that you selected the save option for the canes at D C P s during the survey setup process When the data are saved you will be given the opportunity to take a photograph at the Device location as indicated by the question displayed on the screen shown below 61 Single Test Station goats DW 729 4m Answering Yes on the above screen will take you to the Pictures screen as described in Appendix 3 of the Gx Data logger Pipeline Survey User s Manual Note Several seconds are required to open the picture program How to Position the Camera for a Picture Since the camera on the Gx is located on the underside of the handheld unit it is necessary to remove the unit from its mounting platform by grasping the unit around its mid section and pulling in an upward motion The unit should snap out of its retaining brackets You can now position the camera to take your photograph since the coiled cable connecting the Gx to the dual probe adapter provides a considerable degree of flexibility The unit can then be snapped back into position on the platform after picture taking by l
12. on Single Test Station to highlight this selection Optional By checking off the box labeled Device Name you can manually enter a descriptive name for the test station The name you enter here will be associated with this device as opposed to a default name Also by checking off the box labeled Known Location you have the opportunity to manually enter the actual stationing for the test station if known if it is different from the location entered during survey setup for the Start Location You should then tap on the Next button The screen shown below will be displayed depending on the previous settings 59 Device Readings Sinale Test Station Pipe To Soil on 1 2546 v of 0 9365 v Reading OnfOfF DSP v Reading 5 7 YDC 400 MOhm v Use reading for DCYG signal strength stat fe ey BB 10 28 am The On and Off pipe to soil potentials measured per cycle at the starting test station will be displayed on the above screen assuming that one of the On Off pairs voltmeter reading modes has been selected see the Reading field on the screen Make sure that the box labeled Use reading for DCVG signal strength is checked This will mean that the software will have its first value for IR drop to use in its IR calculations see Section II The above procedure should be performed at each pipe connection opportunity so that the software will be able to apply appropriat
13. polarity will be negative Finally as the operator continues down the line the magnitude of the DCVG voltage measured will decrease quickly near the defect and then decrease more gradually moving further away from the defect Voltmeter Response p otential Difference Increasing and Positive O Potential Difference zero when straddling defect SSE es pS ea ses Potential Difference Decreasing and Negative _ BS RSE E M eee eee Figure 7 In Line DCVG Survey Technique Consequently the DCVG voltage profile recorded in the vicinity of a defect will be considerable different in appearance from that observed in the case of a Perpendicular DCVG survey see Figure 5 Figure 8 represents an illustration of the type of DCVG voltage profile that is recorded during an In Line DCVG survey when a defect is encountered Position along Pipeline of Center Point between Electrodes Survey Direction Defect Location Figure 8 DCVG voltage in the vicinity of a coating defect as a function of the position along the pipeline of the center point between the electrodes with the electrodes configured as shown in Figure 7 In Line or Parallel It should be noted that once a defect has been located during an In Line DCVG survey the critical parameters noted above in Section II 8 for defect size determination need to be determined using the Perpendicular DCVG technique illustrated in Figure
14. the Downbeat field you can select the downbeat schedule associated with the particular current interrupters you are using for the survey The three options are Each Minute Each Hour and Midnight For example if Each Minute is applicable to your interrupters and you select this option for the Downbeat schedule you are indicating to the data logger software that at the top of each minute there will be an On to Off transition the rectifier current will switch from On to Off at the top of each minute This would mean in this example that the software would only have to count back to the top of the last previous minute to have a timing reference Cycle Start Finally if your interruption cycle starts with the current in the ON state the first transition is from ON to OFF check off the box labeled Start Cycle un check this box if the opposite is true Click on the OK button on the GPS Settings screen in order to return to the Voltmeter Settings screen Screen 5 of 5 Cycle On amp Off Times The specific On and Off times setup on the current interrupters should be entered in the On and Off fields respectively on the Setup 5 of 5 Screen Note The On and the Off times should be entered in milli seconds Note Consequently the rate at which DCVG voltages can be captured and saved depends critically on the interruption waveform period This is a particularly important issue in th
15. with the particular voltmeter Range selected codi station O 0 0 1 2 mvocve Total Dist Last Ref Dist e Geo Feat GPS Data GPS Status Standard GPS Estat fe Poa TEE 63 Note The arrow on the Survey screen indicates the polarity of the DCVG voltage reading For positive values the arrow points to the left and for negative values the arrow points to the right This behavior is utilized to locate anomalies using the in line approach see Figure 7 in Section I 10 If you set up the cane push button functionality as indicated in Section HI 1 ie with the right hand cane set to trigger voltage recordings and the left hand cane set to designate the location of survey flags you would trigger the right hand cane every 5 feet or whatever recording interval you selected during the set up process see Section III 1 As discussed in Section II 2 if you are outside of the voltage gradient field of a coating defect the DC VG voltages will essentially be zero However as you enter a defect s voltage gradient field you will observe an increase in the DCVG voltage values displayed on the Survey screen see Figure 5 in Section II 2 When you observe a peak maximum value in the DCVG voltage readings you would interrupt the triggering to perform the Mark process To do so you would tap on the Mark button on the Survey screen The screen shown below will be displayed depending on pre
16. DCVG Training Manual Gx Version MICMILLER co M C Miller Co Inc 11640 U S Highway 1 Sebastian FL 32958 MANUAL CONTENTS SECTION I INTRODUCTION o SECTION II PHYSICAL PRINCIPLES IL IL Il 1 Potential Voltage Gradients cece cece cece ee eeeeeeeees II 2 Perpendicular DCVG Survey Technique 000e I 3 Definition of DCVG Voltage eccesiescace eds cei I 4 Definition of Total MV 033 aceeutiet coer tntnaaean renee II 5 Procedure to Determine Total MV c cece cece e eee es I 6 Detect Size Considerations 4 scivonassesavccrm eemeeeeeee I 7 Definition of IR idt cx sleicnt ides be teda ner kneedtedie ealeotons tarnie ess II 8 Summary of DCVG Parameters at Defect Locations 9 1 SECTION III HOW TO SETUP THE Gx DATA LOGGER FOR DCVG SURVEYS Ill 1 Gx Data Logger Setup for DCVG Applications II 2 Survey Options Menu including Picture Taking Options and Editing Options accuses recnceaacamuntreinas eg cuow ae eeaemualens ons SECTIONIV TEST EQUIPMENT HOOK UPS FOR DCVG SURVEYS IV 1 How to Make Cable Hook Ups for DCVG Surveys Continued Over Polarity Considerations gt aus padoceednenrtees oly ai lea taaeenies 0 In Line Parallel DCVG Survey Technique SECTION V HOW TO PERFORM DCVG SURVEYS V 1 How to Carry Test Equipment During a DCVG Survey V 2 How to View and Save a Pi
17. Note The ProActive program is required to actually view the survey data If you do not have ProActive installed on your PC and you cannot bring your Gx to a PC that has ProActive installed on it you can copy survey files manually from your Gx to your PC and you can subsequently send the copied files to a recipient who is a ProActive user If this situation applies you would proceed to Section VI 2 VI 2 The Manual Approach Step 1 Establish a connection between the Gx and your PC Gx Data loggers can be connected to a PC using the USB cable supplied with the unit 67 Connection via the USB Cable The requirements and procedures with regard to Gx Data logger PC connectivity depend on the operating system of the PC Case 1 Windows XP or earlier PC Operating System The Microsoft ActiveSync communication program is required on the PC If not currently installed the application can be installed from the CD provided with the Gx Data logger Once installed make sure that the Allow USB Connections option is selected in the Connection Settings window of the ActiveSync application Next connect the USB cable from the Gx Data logger to the PC and switch ON the Gx via the RED power button The connection should be automatic and you will be asked if you d like to set up a partnership or not between the Gx and the PC Answer NO to this question as the ability to transfer file data is all that 1s required as opposed to
18. O O Terminal 3 Terminal 2 Terminal 1 Red Banana Plug Black Banana Plug 5 Pin Data Probe Terminal Terminal Connector Terminal USED TO TEMPORARILY NOT USED CONNECTS TO DUAL CONNECT TOATS PROBE ADAPTER The red banana plug jack on the Gx is used to temporarily connect a test lead from the Gx to a pipe connection in order to record pipe to soil potentials for IR drop determination by the software see Section II The GPS Antenna illustrated on the top side of the Gx represents the antenna employed by the data logger s internal GPS receiver An extension antenna is recommended for pipeline survey work External GPS receiver units if employed would be connected to the data logger via its built in serial port Com 1 Port assuming that connection is made via a serial cable to the Gx 52 With either the internal GPS receiver or an external GPS receiver being used the location of items such as flags devices geo features and anomalies can be recorded during the performance of a DCVG survey either manually by tapping on the Log GPS button on the survey screen at each critical location or automatically by pre programming the data logger as described above in Section III 1 SECTION V HOW TO PERFORM DCVG SURVEYS V 1 How to Carry the Test Equipment During a DCVG Survey With the MCM test equipment connected as shown in Section IV 1 and the Gx data logger setup as described in Section II 1 you are ready to perform a DC
19. On Off Pairs Min Max is not a option here since DCVG surveys require a measurable difference between On and Off voltages i e they require a significant IR drop On Off Pairs DSP mode In this mode the voltmeter uses digital signal processing techniques to determine the flat portions of the waveform for both the On and Off parts of the cycle AV values please see the DC VG Training Manual Gx Version are then determined for the On and the Off portions of the cycle from which the DCVG voltage is calculated AV On minus AV Off 33 For these measurements to be successful the data probes must remain in good electrical contact with the soil for at least one full waveform period following the initial contact of the probes with the soil for a stable DCVG voltage value to be displayed On Off Pairs GPS Sync This voltmeter reading mode can only be selected if you are using the built in MCM Internal GPS receiver AND GPS current interrupters With this reading mode elected you can select the recording times on the waveform for both the On and Off readings with respect to the On to Off transitions and the Off to On transitions of the waveform as opposed to the software determining appropriate locations on the waveform for you as in the case of the On Off Pairs D S P reading mode see above With this voltmeter reading mode selected the screen shown below will be displayed revealing an additional button GPS
20. Settings Setup 5 of 5 Voltmeter Setting Read Mode on off Pairs GPS sync mode Range 5 7 YDC 400 MOhm Cycle ms On roo off fod maj Sie E GPS Settings By tapping on the GPS Settings button the screen shown below will be displayed depending on the previous settings 34 GPS Sync On Off Settings On Delay fiso mS GPS Port com 4 z Off Delay fiso mS GPS Type mam Internal v Downbeat Each Minut Cycle Start On gt Off Cancel aystat le eS OB 425 PH GPS Type Select the type of GPS receiver being used Currently only the MCM Internal GPS Receiver can be used with the GPS Sync reading mode On Delay amp Off Delay By tapping in the fields labeled On Delay and Off Delay you can enter specific times in milli seconds for these parameters For example if 150 ms was selected for the Off Delay the data logger would record the voltage value sampled 150 ms after the rectifier current was switched from the ON to the OFF state Also if 150 ms was selected for the On Delay the data logger would record the voltage value sampled 150 ms after the rectifier current was switched from the OFF to the ON State The delay times selected should be based on knowledge of the waveform particularly in terms of any transition spiking The idea is to select sampling times that will avoid any spiking 35 Downbeat By tapping on the menu button in
21. Survey This should be a descriptive name that will help you identify the survey at a later stage Perhaps the name of the section of pipe you are surveying could be part of the filename DCVG and the survey date do not have to be part of the filename as these tags are incorporated with the survey on the ProActive side assuming that you will be downloading the survey data to the ProActive application Note You will not be permitted to use invalid characters such as slashes or as part of a filename You will be alerted if you try to use any invalid characters Step 4 Once you have entered a filename tap the OK button on the above screen The screen shown below will be displayed The specific selections indicated on the screen will reflect the selections made for the previous survey Setup 1 0f 5 Survey Trigger CIS Rect Mode Cycle ON OFF Cane Button s Allowed To D C P Survey D None Left Right Save Flag Read Survey Locations Increasing Decreasing DCG Sidedrains in CIS Surveys _ Use Metric teal Ebie Step 5 Select the survey type by tapping on the menu button in the Survey Type field and highlighting the survey type of your choice 22 aT trigge CIs Cane Button tir D C P sstart f SD WB 1144 am By tapping on the DCVG option the screen shown below will be displayed depending on the previous survey selectio
22. VG survey The Gx Belt Pack allows the Gx data logger to be carried around the waist area in a hands free fashion allowing the surveyor to be able to position the reference electrode data probes canes on the ground every 5 0 feet or so down the length of the pipeline and to be able to trigger the push button switches when appropriate to do so With the Belt Pack option the Gx data logger mounts onto a platform at waist level allowing the operator to view the screen at all times and to make any selections required by tapping on the screen Also the dual probe adapter shown in Section IV is mounted on the underside of the platform allowing convenient 5 pin cable connection of the adapter s output to the data logger V 2 How to View and Save a Pipe to Soil On Off Waveform When you are performing a DCVG survey it is recommended that you examine the pipe to soil voltage waveform at your starting location starting test station and it is suggested that you make a recording of the waveform using your Gx data logger 53 With the red handled data probe making good electrical contact with the soil above the pipe at the starting test station and a test cable temporarily connected from the pipe connection to the red banana plug terminal on the Gx either tap on the WAVE button located at the top of the Survey screen or tap on Survey Options and then tap on Wave The screen shown below will be display
23. a synchronized partnership You can then exit the Activesync application If the connection is not established automatically make sure that the connection option on the Gx is USB_ Serial which it should be by default To do so tap on the Start button on the Gx screen tap on Settings tap on Control Panel and double tap on PC Connection If USB _ Serial is not indicated tap on the Change Connection button and select USB Serial from the drop down menu Repeat the connection process Case 2 Windows Vista or Newer such as Windows 7 PC Operating System The Gx Data logger connects to these systems via the Mobile Device Center which replaces the Activesync program on the PC side Make sure that the USB connection option is set up via the Mobile Device Center Connect the USB cable between the Gx Data logger and the PC and switch ON the Gx The connection should be established automatically If the connection is not established automatically make sure that the connection option on the Gx is USB_ Serial which it should be by default To do so tap on the Start button on the Gx screen tap on Settings tap on Control Panel and double tap on PC Connection If USB _ Serial is not indicated tap on the Change Connection button and select USB _ Serial from the drop down menu Repeat the connection process 68 Step 2 Follow the procedures
24. amed Test Station 1 57 Save As 3J S stemCF GX_Data ccc 2 fox x Name Test Station 1 Type Waveform Files x Baj oeeo Alternatively you could just enter a name of the waveform data file in the Name field and tap on the OK button In this case the waveform data file will be saved directly to the Gx_Data folder Regardless of your target folder you should tap on the OK button to save the waveform data file Load By tapping on the Load button on the Waveform screen and highlighting a particular waveform data file displayed you can have the previously saved waveprint displayed by tapping on the OK button on the screen V 3 How to Record the Pipe to Soil Potential s at a Starting Test Station It is required that you record the pipe to soil potential s at the starting test station This will represent the first Device Data Collection Point associated with the survey To do so tap on the Device button on the survey screen The screen shown below will appear 58 Device Readings Bal Single Test Station Recon ia Single Test Station Test Station wf AC Line Crossing w No Bond Line Crossing w Bond ine Casing Test Station onsumer Purchase Sales Tap POD Device Name C Known Location fo 0 0 Boat le DBM saan As can be seen from the above screen you can choose from a number of Devices In this case you would tap
25. ax mV recording as this is typically the maximum DCVG voltage that will be recorded for this defect This Max mV value becomes the first component of the Total mV determination Once the Max mV has been recorded a DCVG voltage recording 1s made by placing the left hand reference electrode in the previous position of the right hand electrode and moving the right hand electrode to the location of the second black dot along the green line all black dots shown in Figure 6 are spaced at 4 to 5 feet intervals Once a DCVG voltage recording has been made with the electrodes in this position the electrodes are moved in the same fashion to the next measurement positions and a third DCVG voltage recording is made This process is continued typically 3 or 4 measurements are required for a significant defect until the soil to soil potential difference is basically zero ie you have reached remote earth The MCM data logger s software will calculate the sum of these DCVG voltage recordings to generate the Total mV This will represent the voltage gradient on the surface of the ground associated with this defect II 6 Defect Size Considerations Since Total mV represents the voltage gradient on the surface of the ground associated with CP current flowing to a defect if we can relate the Total mV to a measure of the magnitude of the CP current we can obtain a measure of the size of the defect Since the CP current is b
26. d you will have to repeat the Max mV recording a second time as part of the Total mV determination process See our DCVG Training Manual Gx Version Step 14 Tap on the Next button on the above screen The screen shown below will be displayed depending on the selections made on the previous survey Name of P L Valve Segment Starting Location j0 0 0 Station Number Flag Dist Error Limit Dist Per Reading 5 ft Distance Between Flags fico Ft Danenwcencencenccccencencccssccscesececensesed CE ST Bec Dist Per Reading By tapping in the field on the above screen labeled Dist Per Reading you can type in the interval distance in feet or meters for the metric case expected between reading Typically in DCVG work this expected interval distance is 5 0 feet or 2 meter in the metric case 29 Distance Between Flags By tapping in the field labeled Distance Between Flags you can type in the survey flag interval distance between survey flags for the section of pipeline being measured assuming that survey flags have been laid out Typically survey flags are located at 100 feet intervals In such a case you would have a new reference a stationing correction every 100 feet Note If survey flags are not in use enter zero in this field In this case tapping accidentally on the Flag button will not adversely impact your stationing Flag Dist Error Limit Select the maximum
27. detailed below Double click on My Computer on your PC Double click on Mobile Device Double click on SystemCF Double click on Gx_ Data Right click on the survey file you wish to copy amp select Copy Paste the file into a local folder on your hard drive Create a compressed zipped version of the file You would now be in a position to send the compressed file via email for example to a recipient who has access to the ProActive software program Note Do not rename the survey file prior to sending the file to the recipient as the survey file must have the same name as the survey itself VI 3 Using the Driver in the ProActive Software Program Step 1 Create a folder on your PC s hard drive perhaps in your My Documents folder that will be used to permanently save files copied from your data logger You might choose to name this folder something like Surveys Step 2 Establish a connection between the Gx and your PC Gx Data loggers can be connected to a PC using the USB cable supplied with the unit Connection via the USB Cable The requirements and procedures with regard to Gx Data logger PC connectivity depend on the operating system of the PC Case 1 Windows XP or earlier PC Operating System The Microsoft ActiveSync communication program is required on the PC If not currently installed the application can be installed from the CD provided with the G
28. e and dropping off rapidly with distance away from the pipe The potential at remote earth is zero and the potential gradient is the potential difference between the pipe potential negative potential at the pipe and remote earth Line of Constant Potential Cathodically Protected Buried Pipeline Figure 1 Potential Gradient Associated with a Cathodically Protected Pipeline Equipotential Lines are closer together near the pipe indicating that the potential drops quickly initially with distance away from the pipe In the case of a well coated section of pipeline the potential at ground level in the vicinity of the pipe will be close to zero close to remote earth potential However when coating defects holidays are present the local potential at the defect locations increases significantly since the impressed current flows through the soil primarily to the defects This situation is illustrated schematically in Figure 2 below Large Impressed Current Flowing Directly to Holidays Defects Rectifier Anode Figure 2 The Influence of Coating Defects on Impressed Current Flow Distribution along a Pipeline locally high potentials occur at defect locations due to locally large currents flowing to the defects A small amount of current will also flow to the pipeline through the coating the coating will not be a perfect electrical insulator however this current will be negligible compared to that flowing t
29. e IR drop values for each marked anomaly Note A significant IR drop value is necessary in order to be able to detect DCVG anomalies as the IR drop value represents the signal strength for the process For example for the 5 7V 400M9 voltmeter setting a minimum IR drop value of 200mV is suggested for the following reason 60 If it is assumed that you would like to mark defects having as a minimum a 10 IR size the minimum Total mV value in the example case of a 200mV IR drop would be 20mV This means in turn that the minimum Max mV value that you d be measuring would only be 10mV or so since typically about 50 of the total voltage gradient is accounted for in the first side drain reading the Max mV reading Since the noise level associated with the 5 7V 400MQ voltmeter setting is around 5mV you can see why 200mV would be a suggested minimum IR drop value An IR drop value around 500mV would make small size anomaly detection significantly easier Alternatively a lower noise level voltmeter setting could be used For example the 400mV 10MQ setting has a noise level around ImV and the 40mV 10MQ setting has a noise level around 0 5mV For the 400mV Range for instance the minimum IR drop value required to reasonably detect a 10 anomaly would be around 40mV by the above reasoning as compared to 200mV for the 5 7V range The 400mV and the 40mV Ranges would also provide a higher level
30. e ball of concentric spheres spherical surfaces of constant potential The slice would represent the surface of the ground with the distance from the epicenter of the concentric spheres to the slice being the distance from the defect to the ground ie the depth of the pipeline Figure 3 illustrates the in plane potential gradient voltage gradient associated with the surface of the ground in the vicinity of a coating defect on a buried pipeline The defect location is indicated by the X symbol on the buried pipeline and the voltage gradient on the surface of the ground arising as a consequence of the defect is represented by the concentric circles of constant potential The separation between constant potential circles is small in the vicinity of the defect indicating a rapid drop off in potential near the defect while the separation between constant potential circles increases with distance from the defect indicating a less rapid drop off rate with distance as the remote earth potential is approached In order to illustrate this point the constant potential circles have been labeled as percentages It is assumed that the potential on the surface of the ground directly above the defect is 100 of the maximum potential ie the largest potential measurable for this defect 5 10 A0 A Buried xX Pipeline Remote Earth Figure 3 Potential Voltage Gradient at the Surface of the Ground associated with a Coating Defect on a Bu
31. e case of larger waveform periods For example if a 10 second On 2 second Off waveform is employed 12 second waveform period stabilization times between 12 and 24 seconds could be possible at each measurement location before each DCVG voltage reading can be made In contrast the stabilization period would be only on the order of 1 to 2 seconds for a 700ms On 300ms Off interruption cycle Range By tapping on the menu button in the Range field you can select the voltmeter range and associated input impedance setting for your application from the full list of available options 36 Note Use the scroll bar to view all options Note Since all of the voltmeter DC ranges DC channels on the Gx data logger are fast response channels each DC range is an option for DCVG surveys However since DCVG survey readings are typically small either tens of mV or hundreds of mV only with respect to sensitivity the most appropriate DC ranges are the 5 7V 400mV and 40mV ranges depending on the size of the gradient fields that you encounter Another issue is the signal to noise ratio with respect to being able to find and mark anomalies For small signals small gradient fields the voltmeter s noise level is the limiting factor The noise levels associated with the 5 7V the 400mV and the 40mV ranges are approximately as follows 5mV 1mV and 0 5mV respectively Step 17 Tap on the OK button on the Setu
32. e software will generate an average IR drop value to use in the equation based on the defect s location relative to the locations of the two test stations For example if the two test stations bracketing a defect are mile apart and the defect is located as shown below and if the IR drop values are lt 1 3 mile gt lt 2 3 mile gt TS1 X Ce TS2 300mV Defect 500mV IR drop IR drop recorded as shown at the two test stations 300mV and 500mV the software will determine the IR drop value for the IR calculation to be 300mV 1 3 x 500mV 300mV 366 67mV Consequently if the Total mV has been determined and the IR drop has been determined a value for the size of the defect ie the IR can be calculated by the software For example if the Total mV for the above defect was determined to be 100 mV the IR for the defect would be calculated by the software as follows IR 100mV 366 67mV x 100 27 27 I 8 Summary of DCVG Parameters at Defect Locations Assuming that IR drop recordings were properly made at bracketing test stations and that the appropriate DCVG voltages were recorded at each anomaly location with reference to Figure 6 above the software determines the following important parameters for each marked anomaly gt Maximum delta V ON or Max mV ON Magnitude and Polarity gt Maximum delta V OFF
33. ection I 5 and you should Accept the second reading You should proceed in this fashion until you are outside of the defect s voltage gradient field ie the DCVG voltage reading is essentially zero typically DCVG voltages less than about 5mV would be considered essentially zero on the 5 7V 400MQ voltmeter setting At this point you should tap on the Save button which will save all of the data associated with this defect When the data are saved you will be given the opportunity to take a photograph at the Anomaly location as indicated by the question displayed on the screen shown below 65 Single Test Station goats DW 729 4m Answering Yes on the above screen will take you to the Pictures screen as described in Appendix 3 of the Gx Data logger Pipeline Survey User s Manual Note Several seconds are required to open the picture program How to Position the Camera for a Picture Since the camera on the Gx is located on the underside of the handheld unit it is necessary to remove the unit from its mounting platform by grasping the unit around its mid section and pulling in an upward motion The unit should snap out of its retaining brackets You can now position the camera to take your photograph since the coiled cable connecting the Gx to the dual probe adapter provides a considerable degree of flexibility The unit can then be snapped back into position on the platform after pictu
34. ed depending on the previous settings Waveform 5 7 DC 400 MOhm OnfOFF DSP estat fe Pa B s 03 am Read By tapping on the Read button on the above Waveform screen you can view the pipe to soil voltage waveform at the test site A typical waveform would be as shown in the screen below Note The example waveprint shown is not a real waveprint it is only presented for illustrative puposes 54 Waveform SystemCF GX_Data wfm1 wfm Bal 5 7 DC 400 MOhm Single 1 169 0 00 1 00 Sec esate MM 8 07 ay Waveprints are very useful with regard to confirming switching synchronization of current interrupters for example and with regard to checking for On to Off and Off to On transition spikes Settings By tapping on the Settings button on the Waveform screen the screen shown below will be displayed depending on the previous settings 55 Waveform Settings Voltage Range 5 7 DC 400 MOhm Display Mode Single x Waveform Time s fid ia Dooe Since all of the DC channels on the Gx data logger are fast response channels you can select any Voltage Range setting amongst the DC options regardless of the interruption cycle rate The main issue with regard to optimum Range selection is sensitivity in terms of the magnitude of the voltages being measured You can also change the Display Mode selection by tapping on the menu button in the Displa
35. eing switched ON and OFF we can measure the IR drop associated with the CP current flowing in the soil primarily to the defect which is just the difference in the pipe to soil voltage measured during the ON portion of the cycle and the pipe to soil voltage measured during the OFF portion of the cycle Consequently we can have a measure of the current flowing to the defect through the IR drop determination which we can relate to the voltage gradient Total mV II 7 Definition of IR The magnitude of the voltage gradient on the surface of the ground Total mV arising as a consequence of ionic current flowing to the pipe in the vicinity of the defect CP current magnitude I expressed in relationship to the IR voltage drop in the soil due to the CP current flowing is a quantity known as the IR IR Total mV IR drop x 100 In order to determine the IR drop value to use in the above equation pipe to soil voltages are recorded at the test stations bracketing a defect location The software then calculates the difference between the ON and the OFF pipe to soil voltages IR drop values at each of the test stations If the IR values recorded at both test stations are essentially the same the software uses this IR drop value to calculate the IR value for the defect using the above equation If on the other hand the IR drop values recorded at the two test stations bracketing the defect are significantly different th
36. erpendicular configuration see Figure 4 II 3 Definition of DCVG Voltage DCVG surveys are performed in the rectifier current ON OFF mode ie the rectifier current is switched ON and OFF in a cyclic fashion This allows soil to soil potential differences to be recorded during the ON portion of the current cycle and also during the OFF portion of the current cycle For DCVG surveys the MCM data logger s software calculates the difference between the soil to soil potential difference recorded during the ON part of the cycle delta V ON and the soil to soil potential difference recorded during the OFF part of the cycle delta V OFF The polarities of both delta V ON and delta V OFF are also recorded at defect sites more on these polarities later Since delta V ON represents the soil to soil potential difference with current contributions from the pipeline s CP system as well as from all other sources stray interference foreign pipelines etc and since delta V OFF represents the soil to soil potential difference with only the other current sources contributing a DCVG reading will represent the soil to soil potential difference with only the pipeline s CP system contributing to the current flow to the defect For the remainder of this manual the term DCVG voltage will be taken to mean the difference between the CP current ON soil to soil voltage reading and the CP current OFF soil to soil voltage read
37. he lighting conditions under which the image will be captured and the focusing method to be used for example By tapping on the settings button the screen shown below will be displayed 45 eyeSEEsetup gx_ss_image File Options Help Save File Viewfinda 4f gt Image Format Lighting ISxGA 1280x960 Daylight Focus Mode a Ej Near Limit Auto v so En Far Limit POE As indicated on the above screen there are a number of page tabs labeled Camera Accessories Save etc For information on the selections available via the various tabs please see Appendix 3 Camera Settings of the Gx Pipeline Survey Data logger User s Manual Note For the default picture size SXGA 1280x960 the Flash light is not available However you can turn on the LED Lamp which is turned OFF by default if direct light is required You can do so via the Accessories tab on the above screen Also please note that the Flash light is available for the largest picture size highest resolution setting QSXGA 2048x1944 You can return to the Survey screen after the picture taking process by tapping on the X button on the Picture screen Edit Survey Data Collected survey data can be edited by tapping on the Edit Survey Data button or by using the Ctrl and E keys The screen shown below will be displayed depending on the readings values and reading interval etc 46 Edit Survey Data
38. here Step 7 Make Survey Locations selection Once a value has been entered for the Distance between Readings see the Setup 3 of 5 screen that distance for example 5 0 feet can be added to each successive station number each time a reading 1s triggered or it can be subtracted from each successive station number each time a reading is triggered Your selection of Increasing or Decreasing will depend on your walking direction over the pipe with respect to the pipe s stationing 24 You would select Increasing if the station number will be increasing as you perform the survey and you would select Decreasing if the station number will be decreasing as you perform the survey Step 8 Make selection of Metric units if required By checking off the box labeled Metric the reading interval distance between triggered readings and the flag internal survey flag spacing will be displayed on the Setup 3 of 5 screen in meters as opposed to feet Step 9 Make Rectifier Mode selection By tapping on the menu button in the Rectifier Mode field on the above screen the screen shown below will be displayed mak fSauieiea As can be seen from the above screen there are 3 choices for Rectifier Mode However only the Cycle On Off option should be selected for DCVG surveys as rectifier current interruption is a requirement for this survey type 25 Step 10 Ta
39. ing II 4 Definition of Total mV The so called Total mV is the difference between the maximum potential at a defect location and the potential at remote earth arising due to the CP system s contribution to the current flow to the defect Since as shown in Figure 4 a typical electrode spacing is 4 to 5 feet and the voltage gradient field associated with a defect typically extends a significant distance beyond the right hand reference electrode location several measurements are actually required in order to determine the total voltage gradient Total mV associated with a defect II 5 Procedure to determine Total mV When the defect location has been identified as described above ie the location where a maximum DCVG voltage reading has been observed a set of DCVG voltage readings is made by moving in a straight line perpendicular to the pipeline direction Left Hand Electrode to Negative Side of Data Logger 5 10 4 or 5 feet Spacing Right Hand Electrode to Positive Side of Data Logger Direction of Survey Remote Earth Figure 6 Reference Electrode Positions black dot locations along green line for Total mV Determination With reference to Figure 6 above a recording is first made with the left hand reference electrode positioned over the defect and the right hand reference electrode positioned at the first black dot location along the green line The DCVG voltage recorded here is known as the M
40. ining up the groove on the bottom orange bumper with the registration post on the platform and pressing in a downward motion Note By tapping on the X button on the Pictures screen top right hand corner after taking a photograph you will be returned to the Survey screen Answering No on the above screen will return you directly to the Survey screen 62 You are now ready to proceed with the walking portion of the DCVG survey V 4 Howto Locate and Mark Defects Once you have recorded the pipe to soil voltages and observed the magnitude of the signal strength IR drop you should disconnect the test cable from the red banana plug jack on the Gx and re introduce the positive green handled cane You are now ready to record DCVG voltages down the length of the pipeline For Perpendicular DCVG surveys you would place the canes data probes about 4 to 5 feet apart as indicated in Section II with the left hand cane negative cane directly over the pipe and the right hand cane positive cane off to the right hand side The survey screen will be displayed as indicated below and the DCVG mV reading value displayed in the field labeled mV DCVG will depend on whether or not you are inside of a voltage gradient field If not the DCVG reading should be around zero Note Since the Gx s voltmeter is digital a true zero is never displayed and the reading will be somewhere in the noise level associated
41. lectrodes canes on the surface of the ground perpendicular to the pipeline direction with the left hand cane red handled cane positioned ideally over the centerline of the pipe and the right hand cane green handled cane spaced typically 4 or 5 feet from the left hand cane With this cane spacing maintained the operator walks down the length of the pipeline triggering readings every 2 5 feet or some other length interval typically 5 to 10 feet Since the left hand cane connects to the negative side of the voltmeter data logger s voltmeter and the right hand cane connects to the positive side of the voltmeter the voltage recorded at each triggering location is the difference between the soil potentials at the two reference electrode positions in each case Left Hand Electrode to Negative Side of Data Logger 5 10 4 or 5 feet Spacing Right Hand Electrode to Positive Side of Data Logger Direction of Survey Remote Earth Figure 4 Reference Electrode Positioning for a Perpendicular DCVG Survey Potential difference measured at the green line will represent the maximum voltage recorded As can be seen from Figure 4 prior to encountering the coating defect the potential difference measured between the reference electrodes will be essentially zero since we are currently outside the voltage gradient field As we enter the voltage gradient field walking towards the defect the difference between the soil p
42. me for the DCVG survey that you used to setup the survey file Valve Segment optional By tapping in the field labeled Valve Segment you can enter the name or number of the valve segment to be surveyed if known Starting Location very important Provide the Starting Location for the survey by tapping in the field labeled Starting Location and entering the location You can select to have location information displayed on the survey screen as station number feet or milepost station number meters or kilometer post for the metric case Whichever selection you make here will determine how you enter your starting location information For example if your pipeline locations are represented by station numbers you would select Station Number from the menu list and you would enter a starting location for the survey in the form of a station number If you do not know the station number associated with the beginning your survey enter 0 0 0 Step 15 Tap on the Next button on the above screen A version of the screen shown below will be displayed depending on the current Date amp Time and also the filename entered for your survey 31 Set up 4 of 5 Work Order Technician Name Comments Description Survey Date 7 8 2010 6 42 30 Survey Name fisystemCF Gx_Dataljk jk mem Previous Next Cancel camel maj Perie Work Order optional By tapping in the field labeled Work Order
43. n nature i e survey data are recorded every 2 5 feet or every 5 feet for example they can be considered complementary to close interval potential surveys CIPS or CIS and both types of surveys are typically performed on the same pipeline as part of the ECDA External Corrosion Direct Assessment protocol regarding Indirect Inspections With regard to the ECDA protocol at least 2 types of close interval Indirect Inspection surveys are required to be performed on all sections of a buried pipeline and typically DCVG and CIS surveys are employed to satisfy this requirement on well coated pipelines The physical principles associated with DCVG surveys are discussed in Section II and the procedures to setup the data logger for a DCVG survey are detailed in Section II Sections IV and V outlines the equipment hook up requirements for DCVG surveys and how to actually conduct a DCVG survey respectively Finally Section VI describes how to copy DCVG survey files to a PC SECTION II PHYSICAL PRINCIPLES II 1 Potential Voltage Gradients When a buried pipeline experiences impressed current cathodic protection the DC rectifier current that flows in the soil to the pipeline causes the pipeline to be polarized with respect to the surrounding soil As illustrated in Figure 1 below a potential gradient exists between the pipeline and the surrounding soil in such a case the potential being largest at the pipe itself largest negative valu
44. ns Survey DCYG Rect Mode Cyce ON OFF Cane Buttons Allowed To D C P Survey Left Right Fiag Read 5 Sar 7stat fe Soe WB 11 44 am 23 Survey The functionality of the data probe push button switches during a survey is selected by tapping on the menu button in the Survey field Read Read means that both switches can be used to trigger readings Flag Read means that the left hand switch will designate the location of a survey flag and the right hand switch will be used to trigger readings Read Flag means that the left hand switch will be used to trigger readings and the right hand switch will designate the location of a survey flag Flag Flag means that both switches can be used to designate survey flags and neither switch can be used to trigger readings D C P D C P stands for Data Collection Point and on a DCVG survey usually would represent a test station where the IR drop is determined by connecting the voltmeter temporarily for pipe to soil readings The data probe switches can have no functionality at these devices the none selection or they can be used to save the D C P readings such as Pipe to Soil On Off readings at a test station the Save selection Note When Marking DCVG anomalies see Section V the data probe switch functionality becomes accept regardless of whether save or none is selected
45. o the coating defect areas Since the pipe potential can be high at the site of a defect due to large impressed current flow to the defect the potential at ground level above the pipe above the defect site can be significantly higher than zero the remote earth potential Consequently the measurement of a significant above the defect soil potential voltage with respect to remote earth is a good indication that a coating defect has actually been located especially if the soil potential above the pipe away from the defect location is essentially zero with respect to remote earth Since the defect site is surrounded by soil a voltage gradient will exist between the defect site and the soil A voltage gradient will actually exist in 3 dimensions Consider the defect site as being the center of a series of concentric spheres with the surface of each sphere being a surface of constant potential Near the defect the concentric spheres will be closely spaced which means that the potential will drop off quickly with distance from the epicenter the defect site The spheres constant potential surfaces will be spaced further and further apart implying a slower potential drop off rate with distance away from the defect site If we consider the surface of the ground above the pipeline to be a plane the ground will have an in plane potential gradient in the region above the site of the defect Imagine taking a slice through th
46. otentials at the reference electrode positions will begin to increase in magnitude and reach a maximum value when we are level with the defect the green line location in Figure 4 As an example if the maximum potential at the defect is 100mV with respect to remote earth the potential difference measured by the data logger s voltmeter at the green line location defect location would be 80mV since the right hand reference electrode would be positioned on the 20 constant potential line 10 The 80mV reading would occur since the voltmeter would subtract 100mV from 20mV to give 80mV 20mV 100mV 80mV Remember that the right hand electrode is connected to the positive side of the voltmeter and the left hand electrode is connected to the negative side of the voltmeter If we continue walking past the location of the defect the difference between the soil potentials at the reference electrode positions will begin to decrease in magnitude and eventually will be zero again as we exit the voltage gradient field Consequently a profile such as that shown below in Figure 5 will be observed in the case of Perpendicular DCVG surveys as a coating defect is encountered P m Electrode Position Survey Direction gt gt y Along Pipeline Defect Location Figure 5 DCVG Voltage as a Function of Electrode Position along Pipeline in the vicinity of a Coating Defect as measured with electrodes in p
47. p 5 of 5 screen A version of the screen shown below will be displayed depending on the start location entered previously and the location type entered previously station number feet or milepost or station number meters or kilometer post for the metric option Ses station O 0 0 42 5 mvocve Total Dist Last Ref Dist eae Geo Feat Device GPS Data Log GPS Undo Flag Flag Mark GPS Status Standard GPS Eystan fe ee WB 11 09 am 37 In the above active DCVG survey screen the direction of the arrow pointing to the left or pointing to the right depends on the polarity of the DCVG voltage being measured In the above case the voltage being measured was positive which produced an arrow pointing to the left The opposite would be true if the DCVG voltage reading had been negative 1 e the arrow would point to the right Note With the reference electrodes data probes properly positioned the polarity of the DCVG voltage will always be positive above the noise level in the case of perpendicular DCVG surveys In this case the arrow on the survey screen will always point to the pipe However a change in arrow direction will be evident when performing parallel or in line measurements in the vicinity of a DCVG anomaly coating defect In this case the arrow will always point in the direction of the defect location on the pipe with respect to where you are currently standing As you a
48. p on the Next button on the above screen The screen shown below will be displayed depending on the selections made for the previous survey Setup 2 0f 5 GPS Type mcm Intern 7 Only Log Corrected GPS Use GPS for Altitude GPS Port com 4 k Log GPS at Flags Auto Log GPS Never Auto Log GPS at DCP Featur Log GPS at Side Drain JAnomaly DCVG Anomaly Max mv Tot mV 1st read AC Cycle 60 He Bsa TD BB 2 B Step 11 Select Local Electricity AC Frequency By tapping on the menu button in the AC Cycle field on the screen shown above you will have the choice of 60Hz or 50Hz AC Select 60Hz for all U S applications This is an important select with regard to the AC filtering system that s applied to all of the DC voltage channels Step 12 Select the Type of GPS Receiver Being Used If Any By tapping on the menu button in the GPS Type field on the above screen the screen shown below will be displayed 26 Setup 2 0f 5 Only Log Corrected GPS Use GPS for Altitude GPS Port mcm External Log GPS at Flags Auto Log GPS NMEA Log GPS at DCP Featur anual Log GPS at Side Drain MCM Internal Anomaly DCVG Anomaly Max mY Tot mV 1st read AC Cycle feo Hz Baj Caia As can be seen from the above screen there are 5 choices for GPS Type None This means that a GPS receiver is not being used MCM External This means that an external MCM GPS Accessory is being used currently not
49. pe to Soil On Off Waveform V 3 How to Record the Pipe To Soil Potentials at a Starting OSE UAE ON 52 5 ds Sees A EET E E E EE E V 4 How to Locate and Mark Defects 0 cc cece cee cence ceeeeee SECTION VI HOW TO COPY SURVEY FILES FROM THE Gx TO YOUR PC Nile Introd ction seriene yay dan ehneteewesmntey ep haaneal cae EE een sew VI 2 The Manual Approach 966243 oitsy dcth iad ties ieanedoaeasd sin accabedeudabe VI 3 Using the Driver in the ProActive Program eeeeee APPENDIX 1 How to Delete Survey Files from the Gx 173 SECTION I INTRODUCTION Unlike Close Interval Potential Surveys CIPS or CIS Direct Current Voltage Gradient DCVG surveys do not involve an electrical connection to the pipe other than temporarily to determine IR drop values at pipe connection locations please see Section II for details Instead readings on DCVG surveys involve soil to soil potential difference measurements as opposed to pipe to soil potential difference measurements DCVG surveys are typically performed on well coated pipelines with a view to determining the location of coating related anomalies In addition to locating coating related anomalies data collected specifically at anomaly locations side drain data are integrated with the survey data and are used by the software to determine size factors severity factors for the anomalies Since DCVG surveys are close interval i
50. permissible error between the actual number of readings logged between 2 survey flags and the expected number of readings By tapping in the field labeled Flag Dist Error Limit you can type in the maximum permissible error For example the maximum permissible error is indicated as 20 on the above screen If the reading interval is expected to be 2 5 feet and the survey flag separation is 100 feet this means that 40 readings are expected If however only 30 readings are actually logged between survey flags an error window will appear on the screen since there is a 25 difference between the expected and actual number of reading in this example No error window will appear if the difference is less than 20 For this example you could have a minimum of 32 readings and a maximum of 48 readings between survey flags to stay within the 20 max error allowance Auto Pacing Mode optional Select whether or not you would like the readings to be uniformly spaced between any two survey flags regardless of the actual locations of the readings between the two flags By checking the box labeled Auto Pacing Mode you will enable the data logger to automatically adjust the reading locations in order to evenly space the readings between two survey flags Name of P L optional By tapping in the field labeled Name of P L you can enter the pipeline name 30 Note This is not necessarily the same name as the filena
51. pproach the defect the arrow will point towards the upcoming defect location and when you are past the defect the arrow will point back to the defect location Consequently performing in line measurements in the vicinity of a defect can be a good way to pin point its precise location by monitoring the arrow s polarity switches When you are actually straddling a defect location with the reference electrodes in line with the pipe the DCVG voltage will be zero although a true zero is not possible with a digital voltmeter You are now ready to perform a DCVG Survey HI 2 Survey Options Menu including Picture Taking Options and Editing Options By tapping on the Survey Options button on the Survey screen the Survey Options menu will be displayed as indicated below 38 Tapping on the down arrow on the above menu will reveal additional options as illustrated in the screen shown below 39 Settings Once you ve setup the Gx data logger for a particular pipeline survey you can make changes to your setup selections with the exception of your Survey Type selection and the currently indicated Station If you have selected a DCVG survey type for example you cannot change to a Surface Potential type without setting up a new survey You can however make other selection changes mid stream For example you might decide to switch to a more sensitive voltmeter channel Range say 5 7V to 400mV Or in
52. re taking by lining up the groove on the bottom orange bumper with the registration post on the platform and pressing in a downward motion Note By tapping on the X button on the Pictures screen top right hand corner after taking a photograph you will be returned to the Survey screen Answering No on the above screen will return you directly to the Survey screen 66 You would then pick up the survey where you left off and continue triggering DCVG voltage readings until you encounter the voltage gradient field associated with another anomaly SECTION VI HOW TO COPY SURVEY FILES FROM THE Gx DATA LOGGER TO YOUR PC VI 1 Introduction Survey data are stored in independent files one file for each survey on the Flash memory card on the Gx data logger and you can copy survey files to your PC using one of two approaches manually or via the driver in the ProActive software program The ProActive software program represents MCM s CP data management system and this program allows integration of pipeline survey data in a database system and offers extensive reporting both textual and graphical capabilities on the survey data If you have the ProActive software program installed on your PC or you can bring your Gx to a PC that has ProActive installed on it you can use the ProActive program to automatically access survey files on the Gx If either of these situations applies you would proceed to Section VI 3
53. ried Pipeline concentric circles represent constant potential lines The X symbol represents location of coating defect If we imagine pushing a pole vertically from the surface of the ground directly above the defect down to the defect itself and then walking on the surface of the ground away from the pole we ll encounter lower potentials with respect to our maximum potential at the pole as we move further and further away from the pole The percentages indicated in Figure 3 would represent percentages of the maximum potential measured at the pole location Since such surface potential voltage gradients exist above pipeline defects we can perform soil to soil potential difference surveys to detect the defects Such surveys are know as DCVG surveys Direct Current Voltage Gradient surveys DCVG surveys can be performed in two different ways Perpendicular Mode and In Line or Parallel Mode In the case of Perpendicular DCVG surveys an imaginary line drawn between the reference electrodes on the surface of the ground would be perpendicular to the direction of the pipeline and in the case of In Line DCVG surveys an imaginary line drawn between the reference electrodes on the surface of the ground would ideally be in line with the center of the pipeline directly above the pipeline II 2 Perpendicular DCVG Survey Technique As illustrated in Figure 4 below this technique involves placing a matched pair of reference e
54. second method of performing DCVG surveys known as In Line or Parallel Mode In this case DCVG voltages are recorded in a close interval fashion by placing the reference electrodes in line with the pipeline directly over the pipeline as opposed to placing the reference electrodes perpendicular to the pipeline direction This technique is illustrated in Figure 7 below As can be seen from Figure 7 as the operator enters the voltage gradient field associated with the defect and places the reference electrodes as indicated with the right hand electrode connected to the positive side of the data logger s voltmeter and the left hand electrode connected to the negative side of the voltmeter the DCVG voltage measured will begin to increase and have a positive polarity As the defect location is approached the DCVG voltage will increase more sharply since the circles of constant potential are spaced closer together A maximum DCVG voltage will be measured when the left hand reference electrode is directly over the defect As indicated in Figure 7 however the DCVG voltage will drop to zero when the operator is straddling the defect since in this position the reference electrodes will be measuring the same potential and hence the potential difference between them will be zero Continuing down the line with the right hand electrode directly over the defect the DCVG voltage will again have a maximum value however this time the
55. ver Window to appear Step 6 Identify the Survey File to be Copied The Get Pipeline Survey from Gx field on the Gx Driver window will list all of the survey files currently stored on your Gx s Flash memory card Highlight the survey file that you would like to be copied to your PC Also check off the box labeled Copy to Local Folder and identify the target folder s location on your hard drive in the field underneath using the browse button This is the folder that you set up previously Step 1 above in which to save all of your survey files copied from your Gx Also if you used the metric system on the data logger check off the box labeled Use Metric Finally click on the Go button on the Gx Driver window Step 7 Examine the Survey Data Prior to Posting the Data to the ProActive Database 71 You will have actually completed the process of copying a survey file to a local folder on your PC by this point using the Driver in ProActive However before exiting the Driver it is recommended that you examine your survey data prior to posting the data to the ProActive database The process of posting the pipeline survey data to the ProActive database is detailed in the ProActive Training Manual and is beyond the scope of this manual To examine the survey data in the Gx Driver you can click on the various page tabs now appearing on the Gx Driver Pipeline Survey window Surve
56. vious settings Mark DCVG Anomaly 97 5 y Read Max mY p m Read Total my Log Pos Max mY Accept Total mY Save Range 5 7 VDC 400 MOhm Clear asta fe SAD 11 142 eel 64 If you selected automatic logging of GPS position data at Sidedrains Anomalies during the survey setup process see Section III the Gx data logger will log the GPS data for the DCVG anomaly site when you accept the first side drain reading see below If you did not select this option during survey setup you should tap on the Log Pos button if you would like to have GPS data logged for the anomaly location You would record the Max mV reading first side drain reading by tapping on the radio button labeled Read Max mV and tapping on the Accept button do not tap on the Save button at this time Alternatively you could use either push button switch to accept the reading which is actually more convenient You will notice that the software automatically applies the Max mV value as the first value in the Total mV determination for the case where this option was selected during the survey setup process see Section III 1 If this were not the case for your survey setup you would Accept the Max mV reading a second time and this would become the first voltage used in the Total mV determination You should then proceed to move the electrodes to their second positions see S
57. x Data logger Once installed make sure that the Allow USB Connections option is selected in the Connection Settings window of the ActiveSync application 69 Next connect the USB cable from the Gx Data logger to the PC and switch ON the Gx via the RED power button The connection should be automatic and you will be asked if you d like to set up a partnership or not between the Gx and the PC Answer NO to this question as the ability to transfer file data is all that is required as opposed to a synchronized partnership You can then exit the Activesync application If the connection is not established automatically make sure that the connection option on the Gx is USB _ Serial which it should be by default To do so tap on the Start button on the Gx screen tap on Settings tap on Control Panel and double tap on PC Connection If USB Serial is not indicated tap on the Change Connection button and select USB Serial from the drop down menu Repeat the connection process Case 2 Windows Vista or Newer such as Windows 7 PC Operating System The Gx Data logger connects to these systems via the Mobile Device Center which replaces the Activesync program on the PC side Make sure that the USB connection option is set up via the Mobile Device Center Connect the USB cable between the Gx Data logger and the PC and switch ON the Gx The connection should be established
58. y Mode field In the case of the Single reading mode option you can select the number of waveform periods to be displayed viewable via the horizontal scroll bar by tapping inside the Waveform Time box and entering a value manually for number of seconds For example if the interruption cycle period is 5 seconds 4 seconds On 1 second Off and you entered 10 seconds you would have 2 waveform cycles displayed Save To record a waveprint tap on the Save button on the Waveform screen The screen shown below will be displayed Note The specific folders presented on the screen will reflect the contents of the Gx_Data folder on your Flash memory card SystemCF The Gx_Data folder is used to store all of your survey files 56 Save As 2462SU01_2110 chuch bcd cnT1 hgg cab ddd hh eee ik Franks SU101 Name Untitled Type Waveform Files agstart fe 2 1 SM i 8st am You have a number of options regarding saving the waveform data The recommended option if you are recording waveform data in the context of a pipeline survey is to save the waveform data file inside the actual pipeline survey file To do so you would double tap on the survey file folder and enter a descriptive name for the waveform data file in the Name field For example the screen shown below would be displayed for the case of selecting the ccc survey file for storage of the waveform data file n
59. y Settings Readings Device Readings Graph By clicking on these page tabs you can view information on the Survey settings or you can view the actual survey and device data please see the ProActive Training Manual for details 72 APPENDIX 1 How to Delete Survey Files from the Gx Once you have copied your survey files to your PC see Section VI you can if you wish delete the files from your Gx s Flash memory card Since your survey files are stored on the Flash card you will have to access this memory SystemCF in order to delete selected survey files The procedure would be as follows Tap on the Start button on the Gx Tap on Programs Tap on Windows Explorer Double tap on SystemCF Double tap on Gx_ Data Tap and hold on the Survey File you wish to delete until a menu pops up e Tap on the Delete option This will delete the highlighted survey file 173
60. you can enter the work order number associated with the survey if known Technician Name optional By tapping in the field labeled Technician Name you can enter the name of the surveyor Comments Descriptions By tapping in the field labeled Comments Descriptions you can enter any general comments you might have regarding the survey perhaps weather conditions soil conditions etc Also shown on the above screen are the survey filename Survey Name field and the Start Date and Start Time for the survey Survey Date field Note The survey files are stored in the Gx_Data folder on the Gx data logger s CompactFlash memory SystemCF a non volatile memory Note These data cannot be changed manually 32 Step 16 Tap on the Next button on the above screen A version of the screen shown below will be displayed depending on the settings selected for the previous survey Setup 5 of 5 Voltmeter Setting Read Mode on off Pairs DSP mode Range 5 7 VDC 400 MOhm Cycle ms On roo off fs00 foals season E Read Mode DCVG surveys are performed with the rectifier current switched ON and OFF in a cyclic fashion and as can be seen by tapping on the menu button in the field labeled Read Mode there are only two choices available for the reading mode of the voltmeter The choices are On Off Pairs DSP mode and On Off Pairs GPS Sync Note

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