Inspection Solution for Water-Filled Vertical Cavern Storage Lines
Solution for corrosion and wall thickness measurement, detection of ovality and weld misalignment
After 10 years, a gas storage operator had to inspect their 150m (492ft), 4”-24” vertical casing pipes due to regulations. They were looking for more reliable and efficient technologies regarding coverage, resolution and accuracy. The top parts of the pipes were air-filled, the lower parts were filled with water. The operator needed to know the condition of the lines in terms of ovality, weld misalignment and internal and external corrosion, especially at the welds.
Our solution
Water filled vertical cavern pipelines need to be approached not differently than inspecting a vertical riser on an offshore installation. Therefore, ROSEN used the tethered bi-directional ultrasonic measurement inspection tool (TUM).
It was equipped with:
- Scanners with up to 320 UT wall thickness sensors
- A light system
- An explosion-proof video camera
The TUM tool was launched through an open bore and lowered into the pipes. To ensure the UT measurement in both parts of the pipeline, the tool was equipped with a flipping disc set in the front. The set sealed the TUM and carried a water column of 1-2m on the tool’s way down to ensure the UT sensor had the required coupling medium and preventing the UT electronic from contact with air. On the way up, the discs flipped, and the water column was released while the tool was switched off.
This approach ensured two sets of UT and camera data for the water-filled part and one set of UT data for the air-filled part of the pipes. Since the TUM tool allows real-time-data-evaluation from the odometer data and the visible girth weld the inspection team could see the exact movement of the tool. During the run, the team was able to check metal loss, internal and external or other material anomalies. The operator received a first report still on site, directly after the inspection.
Your benefit
The innovative approach of ROSEN ensured an efficient inspection of vertical cavern lines. Moreover, it provided the operator with reliable results regarding accuracy, resolution and reliability. The TUM method proved to be more cost-effective in comparison to conventional inspection methods when it came down to the technical results. These enabled the operator to calculate the service life of the pipelines more accurately than before.