Static equipment (e.g. pressure vessels and piping systems) used in process industries to contain hazardous fluids is subject to age-related, deterioration, such as corrosion and fatigue. The ageing phase of an asset's lifecycle begins at the point when age-related degradation, begins to significantly increase the equipment's underlying probability of failure. Depending on how well an asset has been managed, ageing may begin well before or after the end of its design life, which is typically a nominal 25 years. As a considerable proportion of, high-hazard sites are operating close to or beyond their original design life, managing the integrity of ageing assets present a challenge, to site operators due to the risks that equipment failure presents to people, the environment and property. Around a quarter of the, reported major accident losses of chemical plants in the EU are estimated to have been caused by the consequences of ageing, equalling, 11 fatalities and over €170m of economic losses over a 16-year period. Pressure vessel inspection is an important component of an, asset integrity management programme that, when executed effectively, provides an early warning of ageing issues. This paper analyses, a dataset of inspection records covering over 70 000 equipment items located on high-hazard sites across the UK. Changes in the, inspection interval and the number of actions raised per inspection indicate that the ageing phase begins on average at around 35 years from equipment installation.