Ensuring long-term integrity for high-pressure pipelines
The design standard for high pressure pipelines in the UK is IGE/TD/1 and the latter standard provides guidance on sleeve design. In relation to nitrogen filled sleeves it was standard practice in earlier times prior to about 1985 to install the carrier pipe within a sleeve at road or rail crossings. Once the carrier pipe was in a sleeve the pipeline is then shielded from the pipeline electrical corrosion protection (or Cathodic Protection (CP) system) and could suffer corrosion. To ensure that the pipeline within the sleeve was protected from corrosion the sleeve was filled with nitrogen to exclude air and since no oxygen was present corrosion could not take place.
A number of these nitrogen sleeves have now failed to retain the nitrogen pressure and are leaking. Thus, as a result air can enter the sleeve and atmospheric corrosion can occur on the gas carrier pipe.
It is often difficult to repair failed nitrogen sleeves and the UK gas industry has been looking at ways to over come the problem. If there is ongoing corrosion on the carrier pipeline within a sleeve then that can be a significant threat to the pipeline integrity.
Carr Civil Engineering Ltd has instructed IACS to provide technical assistance on the laboratory testing and an order has been placed with Aachen University to carry out various laboratory studies.
The information Carr Civil Engineering Ltd will gain from the laboratory studies will enable the Company to have a commercial advantage and position as preferred contractor for the installation process as there will be technical supporting data available to demonstrate to the pipeline operators that the grouts have the desired properties.