PRESERVATION

Preservation is carried out to maintain the pre-commissioning conditions of the installation until commissioning comes into force.

a) Preservation with Dry Air

If the initial gas filling is carried out later than six months after the installation works are completed, preservation of the piping takes place according to the dry air method. The main criteria for a dry pipeline are as follows:

  1. Dew point temperature must be ≤ −20°C measured at atmospheric pressure.
  2. Overpressure after sealing of the pipelines must be at least one bar.
  3. The acceptable minimum norm during the entire preservation period is a measured dew point temperature of ≤ −10°C (measured at atmospheric pressure and at an overpressure of one bar).

The dew point temperature and the pressure are measured and registered within the preservation period with stated intervals since the contractor as well as a neutral third party is involved.

b) Preservation with Nitrogen (N2)

If preservation is decided by using nitrogen, the criteria are as follows:

  1. Purge with nitrogen until achieving 100% N2.
  2. The overpressure after sealing must be at least two bars.

Measurement of the pressure at stated intervals during the preservation period is required.