Studies of the damaging effect at various loads and hydrostatic test frequencies

This article develops the methodology given in Ref.1 to calculate hydrostatic re-testing intervals for a pipeline section with growing crack-like defects. It examines sections with both growing crack-like defects and corrosion defects. The actual pressure-cycling factor is taken into account for crack-like defects. Modern techniques employed for periodic hydrostatic testing have been analysed to ensure the integrity of existing pipelines, and the benefits and limitations of various methods are described. Examples are given for calculating the hydrostatic re-testing interval for pipeline sections with growing crack-like and corrosion defects. This paper shows that where hydrostatic testing pressure is selected according to the actual operating pressure-cycling factor, the corrosion rate, impact-toughness characteristics, and cycling cracking-growth resistance of the pipeline steel, and the operating pressure, the required re-testing interval can be guaranteed.