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Pipeline tests

Weld tests of the internal service pipe are performed by X-ray imaging. Welds must correspond to the 1st and 2nd class according to the ČSN standard. 100 % of welds are tested.

Weld tests of the outer casing pipe are carried out:

  • by capillary method or vacuum goggles
  • by spark test with a test voltage of 25 kV
  • by pressurizing with air of at least 0.5 bar (or other gas) and by coating the welds with foam solution

After the pipe is installed and the sand backfilling plus the compaction of the excavation at least 100 mm above the casing pipe are completed, the vacuum-insulated pipeline can be put into operation.

Before starting the vacuuming process, we recommend opening the plugs on the end caps and running the pipe for at least 14 days to allow it to dry naturally. This significantly reduces the vacuuming time. Extra caution is required during drying to avoid flooding of the pipes while the end valves are open. After drying, the space between the service and casing pipe is evacuated by a mobile vacuum pump to a pressure of 1 - 20 mbar absolute pressure.