Cased pipes are generally believed to be very safe. However, external corrosion caused by electrolyte does exist. Due to metal loss, any CP benefit could be completely ignored. There is corrosion risk on carrier pipe. However, many ECDA tools may not be used effectively on cased pipes at crossing. Therefore ECDA procedure can not deal with the inspection and integrity assessment problem of cased pipes. This paper describes test methods of insulation between casing and carrier pipe, and corrosion inspection method of carrier pipe. Using PCM and potential test, the electrical insulation between casing and carrier pipe is assessed. Corrosion of carrier pipe is tested through GWUT. The CP status is checked by CIPS. And sealing condition is inspected at both sides of casing. The result is that there is no metallic short or electrolytic contact between casing and carrier pipe, no corrosion on carrier pipe, CP works well at both sides. It is also concluded that test methods are effective. Test methods can assess cased pipe integrity which is difficult to assess at ECDA procedure.
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