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Continued from The MP Blog, p. 13. The following items relate to cathodic & anodic protection. Please be advised that the items are not peer-reviewed, and opinions and suggestions are entirely those of the inquirers and respondents. NACE International does not guarantee the accuracy of the technical solutions discussed. MP welcomes additional responses to these items. They may be edited for clarity. Cathodic protection for road crossing with concrete sleeves carrier pipe is empty. Is carrier pipe pro- How many test stations should there be tection required with a zinc ribbon anode per mile (1.6 km)? I know the suggested number, but is there a rule requiring a in this case? minimum number of test stations for The annulus should be flled with compliance with rules? an inert casing fller or grout. The One of my clients has an old pipeline grout should be cement-based with very few test stations (most of the and should completely fill the others have been demolished over the annulus in order to ensure cathodic proyears). To meet DOT requirements, he tection of the carrier pipe. needs to put the pipe under cathodic protection (CP), which we will do, but I need a statement about the required number of test stations per government regulations, if there are any on this subject. It's expenIs there a requirement sive to install test stations on an existing by a governmental pipeline, so the client wants to put in as few as possible. A Cathodic protection test stations Q agency (such as the We have a road crossFor many years in Venezuela, we U.S. Department of ing where a carrier have installed one normal potenpipe runs through a Transportation [DOT]) retial test station at each kilometer. garding the minimum numAt critical areas test stations are concrete casing. The ber of test stations for a cath- installed before and after large river crosscasing is provided with end seals, but the annular space between the casing and the odically protected pipeline? ings; one at major creeks (with or without Q A water fow all year round); before and after asphalt-paved superhighway crossings; and one at asphalt and gravel roads, at sites near lagoons or lakes, at changes of geology or topography, changes in soil, at foreign or own crossings, or where paralleling other pipelines, and before and after buried isolating joints. At the drainage point of the CP rectifer station, we install a test point with a permanent reference electrode near the pipe. Other examples are garbage dumps near small cities, sites near plants where there might be discharges of products into the soil, or near foreign locations that have CP protecting their buried pipes. We design with two cables connected to the pipes (separated at least 5 to 6 in [130 to 150 mm]). Considering the cost of coming back to excavate if you have a cable failure, the cost of an extra cable is minimal. We never accept two cables connected with one shot of exothermic welds. At the crossings we connect the cables to all crossed pipes and take them above to the test box, but do not bond the cables if no representative of the other pipeline owner is present. Continued on page 43 40 MATERIALS PERFORMANCE May 2013 NACE International, Vol. 52, No. 5