In a Nutshell:
Today’s energy infrastructure means we need more, and more-reliable, ways of transporting energy. Pipelines being no exception to that need, it is vital to check post-construction that new pipelines were installed properly in order to ensures a healthy start to their operational lives. This case describes the geometry inspection and XYZ mapping of an extremely critical line – specifically a 42″, 245-km gas pipeline.
Nine-day-long in-line inspection
As far pipelines are concerned, 245 km is considered very long, meaning any in-line inspection would take quite some time. Regardless, every pipeline needs to be inspected, be it aboveground, belowground or subsea. It does not matter whether it is short or long – as was the case with a 42″, 245-km gas pipeline. The objective for ROSEN was to complete a high-resolution geometry inspection service (RoGeoXT) as well as XYZ mapping in order to create a baseline understanding of the pipeline’s integrity status. Due to this particular project’s critical importance in ensuring a reliable energy supply to the end user, the operator chose to survey 5 in-line inspection vendors before choosing ROSEN.
Once chosen, ROSEN was asked to conduct vigorous testing on the geometry inspection tool, which would need to travel at a consistent speed and continuously collect data for 9 consecutive days, the predicted run time of the tool. The customer was able to visit the ROSEN facility to review the tool in operation.
Additionally, the tool would need to sit in the subsea receiver for 45 days. This duration was used to dewater and dry the pipeline, giving the onsite crew to time to lift it out of the water safely. At that point, a ship would lift the pipeline and remove the temporary receiver trap.
Over 200 hours of pigging operations
When inspection time came, 2 cleaning pigs and 1 caliper (XT) tool were used. The tools were propelled using 2 transport mediums, batched first with seawater and then with air. Everything went according to plan, with a run duration of 213 hours and 20 minutes and an average tool velocity of 0.46 m/s (1.656 km/h).
Figure 1: When pipelines are deemed unpiggable (i.e., only accessible externally), a few options are available for integrity management.
Once completed, 700 kg of sediment had been collected from the cleaning tools, and the raw data was downloaded, processed and analyzed. The testing paid off, as the inspection delivered the following results:
- The data showed the launcher trap and receiving spool visible and installations in their correct o’clock positions; this determined that the tool recorded data along the entire pipeline during the run.
- Although the total recorded distance was less than the expected value reported by the operator, it was later corroborated by the actual construction length of the pipeline at the moment of the inspection.
- The mean internal diameter recorded by the caliper coincided with the information from the pipeline questionnaire.
- The average tool velocity registered during the survey was about 0.46 m/s (1.656 km/h), which is within the acceptance criteria of the tool (0.1 m/s ≥ V ≤ 5 m/s). However, the velocity was variable during the batching phase, with an average of about 0.1 m/s; the maximum tool velocity peak was about 0.62 m/s (2.232 km/h). Summing up all the velocity peaks the tool registered, it was determined that there were no velocities above the maximum specification of the tool, but there were areas in the beginning of the inspection where the velocity was at the lower specification limit.