Asset Protection Cathodic Protection Testing of Insulating Joints. Work Instruction No.:

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1 Asset Protection Cathodic Protection Testing of Insulating Joints Approved by: Manager Pipeline Standards 1 PURPOSE This work instruction describes the requirements and process for testing the integrity of an insulating flange or monolithic insulating joint. All tests shall comply with APT O&MS Health, Safety and Environmental Management Systems and meet the requirements of all relevant statutory gas supply legislation. 2 REFERENCES 9019 Cathodic Protection System Maintenance and Testing Procedure 3 GENERAL INFORMATION Insulating flanges and monolithic insulating joints are installed in metallic pipelines and networks for corrosion control purposes and to isolate pipelines from earthing systems. Checks of insulating flanges and monolithic insulating joints are carried out to verify the ability to insulate by using one of the following methods. Simulated Failure of an Insulating Joint. Basic Potential Difference. Interruption of CP Current. High Voltage Application. Model RF-IT Pipeline Insulator Tester Method. Periodic inspection of an insulating joint is usually not required. However, inspections may be required when investigating Cathodic Protection problems both upstream and downstream of an insulating joint. of the magnetic field induction ring then touch the test lead probe on the adjacent side of the magnetic field induction ring, but on the same side of the insulation joint. Hold both probes onto the pipeline as shown in Figure 1. (Scratching through any painted surfaces will ensure a good contact between the test probes and the pipeline). With the two test probes connected to the pipeline depress the trigger switch located underneath the handle of the A.C. Generator. This will allow current to flow from the fixed test probe on the A.C. Generator to the test probe located on the other side of the Magnetic Field Induction Ring. As the trigger switch is depressed, observe the A.C. Generator Meter and the Magnetic Field Induction Ring Meter. Both indicating needles should deflect, simulating a fault condition and demonstrating that the equipment is working correctly. 4 PROCEDURE 4.1 Simulated Failure of an Insulating Joint Method Equipment Pre-Test Place a magnetic field induction ring around a section of pipe approximately 300mm-400mm away from the insulating joint being tested. Using an A.C. Generator touch the pipeline with the fixed probe one side Equipment Configuration, Pre-Start Test Set Up Figure Testing an Insulating Joint Leave the Magnetic Field Induction Ring in the same location as for the pre-start test. Touch the pipeline with the fixed probe on the A.C. Generator then Issue 2 October 2007 Page 1 of 5

2 touch the pipeline with the test lead probe ensuring that the Magnetic Field Induction Ring and insulating joint are in between the two probe connections, as shown in Figure 2. Hold both probes onto the pipeline. (Scratching through any painted surfaces will ensure a good contact between the test probes and the pipeline). Insulating Joint Test Set Up Configuration Figure 2 With the two probes connected to the pipeline depress the trigger switch located underneath the handle of the A.C. Generator. Observe one of the following conditions: Both the Magnetic Field Induction Ring and the A.C. Generator meter needles deflect, indicating that the insulating joint is faulty and requires repair. The A.C Generator meter indicating needle deflects, but the Magnetic Field Induction Ring Meter indicating needle does not, proving the integrity of the insulating joint and therefore no action is required. Record the Test Results on the Insulating Joint Test Report Form. A sample form is shown in Appendix A. 4.2 Basic Potential Difference method This method is used when conducting an integrity check of an insulating joint protecting a facility such as a district, field regulator or gate station by monitoring ON potential measurements using a Digital Volt Meter and a Cu/CuS0 4 Half Cell. The protected side of the insulating joint will have a negative potential in the range of -1500mV to - 850mV. The facility side of the insulating joint will also exhibit a negative voltage but should be less negative than that of the protected side. If the facility side of the insulating joint is earthed then the potential should be between -500mV and - 700mV. This will be consistent with the natural potential with respect to the Cu/CuS0 4 of the earthing structure. If the facility piping is either unearthed or disconnected from the earth then that pipe could have zero potential. This should never be the case and further investigation will be required. Studs and nuts of insulating flanges in good condition should be independent of earth and pipeline potential and at the same potential as the Cu/CuS0 4 half cell. Underground insulating joints installed protecting facilities have a cross bond connected for electrical continuity and to reduce Cathodic Protection attenuation. Removal of the cross bond to test the Insulating Joint using the Potential Difference method may not be as effective as the method where the Cathodic Protection current is interrupted. Record all details as required on the Insulation Joints Test Report Form as shown in Appendix A. 4.3 Interruption of Cathodic Protection Unit - current method This method applies to assets cathodically protected by a Cathodic Protection Rectifier unit. It does not apply to sites Cathodically Protected using sacrificial anodes. Issue 2 October 2007 Page 2 of 5

3 This method is employed during an ON/OFF potential survey or where a fault has been detected and further testing is warranted. Connect an interrupter in series with the output of the site Cathodic Protection Unit. Set the interrupter to switch at intervals. Typical intervals are 13 seconds ON and 2 seconds OFF. Note: If a Cathodic Protection Unit is fitted with an interrupter package, the portable interrupter will not be required. Measure the potential shift on either side of the insulating joint being tested with respect to a Cu/CuSO 4 half cell. The interrupted (cathodic protection unit) side of the insulation joint should have a significant shift in potential, whilst the other side of the insulation joint should have a negligible shift in potential. This would indicate the insulation is sound. If a significant shift is detected on both sides of the insulation joint, this would indicate the insulation is faulty. Where an underground insulating joint is being subjected to this test any permanent cross bond shall be removed from the associated test point and potential shifts on either side of the insulating joint are to be measured. The side that is no longer connected to the local Cathodic Protection Unit should experience a potential much lower than the side still connected, if any. Record all details as required on the Insulation Joints Test Report Form as shown in Appendix A. Replace all permanent cross bonds after testing has been completed. Where fitted remove the portable interrupter and replace the Cathodic Protection Unit output link. 4.4 High Voltage Application Method This test method is used for testing individual bolts or insulating flanges. Remove any surge diverting device installed across the insulating joint. Connect a high voltage test instrument set on the 500Vdc setting to the unprotected side of the insulating joint or to one side of a stud and bolt assembly. Caution: This method subjects the insulating joint to a much higher than normal voltage. Extreme care must be exercised when conducting this type of test. The instrument probe shall be placed directly across the item under test. The minimum resistance reading should be 5MΩ. Record all details as required on the Insulation Joints Test Report Form specified by your manager or supervisor. A sample form is shown in Appendix A. 4.5 Model RF- IT Pipeline Insulator Tester Method The Model RF-IT Insulator Tester consists of a portable battery powered electronic instrument with detachable probes for making positive electrical contact across an insulator. The RF-IT works using radio frequency. The radio frequency signal is applied to one side of an insulator by one of two probes. The second probe then receives a high frequency signal. If the received signal is almost as strong as the applied signal, the insulator is shorted. The RF-IT has an internal band-pass filter which will filter out all frequencies above and below 221kHz. This allows the taking of measurements on pipelines that are under cathodic protection or have other induced or impressed currents or signals. Note: As the RF-IT uses radio frequency to measure the effectiveness of an insulator, the measurement results cannot be displayed in ohms. Newer model RF-IT units use a digital meter that mimics an analogue needle type meter. Older RF-IT units use a digital bar graph meter. Both units sweep from left to right. The RF-IT Insulator Tester is factory calibrated and needs no field adjustments. Calibrations Issue 2 October 2007 Page 3 of 5

4 are made using the probe wire conductors supplied with the unit. Note: Do not make changes or substitutes for probes and wires. When the battery output becomes too low to power the instrument (below 7 volts DC), the black lines on the LCD meter will flash on and off. Replace with 6 AA size alkaline batteries. Older model RF-IT units with the bar graph do not show battery condition. The display will grow faint and fade as the battery output falls below 7 volts. Push the red button on the panel to turn the tester On. Push again to turn the tester Off Note: if the tester is not turned off manually, it will turn off automatically after 10 minutes. If the tester seems to fail during testing, firstly check the On off switch. Pre Operation Check of the RF-IT Tester Insert the black probe into either port locator on the front end of the tester. Insert the red probe into the other port locator on the front of the tester. Turn the unit On. Observe the LCD meter. The meter should show black lines across the entire meter face. Note: Older model RF-IT units show solid black square dots completely across the top and bottom of the meter face. Between the bars at each side, two black arrows should flash slowly. The tester is now ready to operate. Operation to Check Single In-Line Insulator Place the solid black probe s steel point on one side of the insulator, making positive contact to the metal pipe. Place the flexible cable (or solid) red probe s steel point on the opposite side of the insulator, making positive contact to the metal pipe. If the insulator is shorted, (low electrical resistance), the LCD meter will be down low (left side of the meter) towards the 0. The older models will show only one or two black square dots on both the top and bottom rows on the LCD meter. If the LCD meter reads 100%, all the way to the right hand side of the meter, the insulator is performing well. The Older model RF-IT units will show solid black square dots completely across the top and bottom rows. LCD readings between these extremes, gives the operator the degree of quality of the insulator. The lower the LCD reading, the lower the electrical resistance of the insulator. A low resistance reading may be cause to watch for impending failure. Operation for Checking Insulated Flange Bolts On single insulated pipeline flange type insulators (where the bolts are insulated only halfway through the flange) make positive contact with the fixed probe of the tester to the insulated flange and make positive contact with the flexible probe to each bolt on the same side of the flange. Read the meter for every bolt. Meter readings will be the same as described in the previous operation. On double insulated pipeline flange type insulators, make positive contact with the fixed probe of the tester to one side of the double flange and the flexible probe to each bolt, individually on the opposite side of the flange. Read the meter for every bolt. The meter readings will be as described as when checking single in-line insulators. Note: In the event of an insulated flange indicating a definite electrical short, but all bolts indicate they are insulated properly, the electrical short exists across the flange insulator. Issue 2 October 2007 Page 4 of 5

5 Appendix A Insulation Joint Test Report Date Joint Number Location IJ Resistance (MΩ) Potential Shift (mv) Upstream side Downstream side TESTER CP SUPERVISOR Tested by. Received by Signature Signature. Date Date.. Issue 2 October 2007 Page 5 of 5