Transportadora de Gas del Sur (TGS) A.S. has analyzed the advantages and limitations of the continuous ground conductivity survey technique, compared this technique with other widely used techniques and implemented successfully the use of continuous ground conductivity data in the external corrosion direct assessment (ECDA) process and high pH stress corrosion cracking (SCC) model. Electromagnetic ground conductivity (EMGC) survey limitations: The resistivity exploration at different depths is more difficult with low range instruments than with the four pin method. AC induction can cause problems in the measuring electronics at certain frequencies. Linearity is valid with a lower limit of 100 ohm x cm. EMGC survey advantages: Measuring technique without contact issues improves accuracy. Coupled with ground positioning system (GPS) hardware provides easy data integration with geographic information system (GIS). At walking pace surveyor could survey 10 km of pipeline right of way (ROW) per day. Higher resolution than conventional methods. High pH SCC Model and ECDA implementation: The electromagnetic (EM) survey data are used in the ECDA pre-assessment step to define regions. Indirect inspection methods are selected to assess the coating condition and cathodic protection (CP) effectiveness. The EM survey data are used in the preliminary phase of analysis to select regions for further data collection in the SCC Model. ECDA Indirect Inspection step identifies deficiencies in either coating or CP, and then EM measurements of resistivity will probably suffice to identify locations prone to corrosion. Severe direct current voltage gradient (DCVG) coating faults and close interval survey (CIS) polarized CP levels more positive than -850 mVCSE in low resistivity soils are selected for direct examinations. Direct examination results are used to define corrosion rates for each region and inspections intervals. Soil sample results and root cause analysis are included in the pre-assessment step to refine the region definition criteria.
Electromagnetic ground conductivity survey technique in pipeline integrity
2009
10 Seiten, 11 Bilder, 2 Tabellen, 5 Quellen
(nicht paginiert)
Aufsatz (Konferenz)
Datenträger
Englisch
Auflösungsvermögen , Beschichtung (Überzug) , elektromagnetisches Messverfahren , Genauigkeit , GIS (Geoinformationssystem) , globales Navigationssystem , Inspektion , Korrosion , Korrosionsgeschwindigkeit , Leitungskontrolle , Messverfahren , pH-Wert , Pipeline , Risskorrosion , Software , Spannungskorrosion , Spannungsrisskorrosion , Überwachungstechnik , Vergleich
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