Asset integrity

With the ageing infrastructure in most of the oil and gas plants in the Middle East maintaining asset integrity is a major challenge. How can we be prepared to deal with unforeseen major and complex breakdowns that would surely jeopardise safety and production?

Stanley Deighton. Looking into the future, a decision could be made to optimise the five-year business plans dealing with replacement or major overhauls. Reliability assessment using degradation data has become a significant approach to evaluating the reliability and safety of critical systems. A challenge for asset replacement is when to replace equipment without spending too early or jeopardising safety through late investment. Within the Oil and Gas industry, there are many reliability databases available to predict failures. However, these databases only supply acceptable reliability figures to make design calculations based on constant failure rates. When considering Remnant Life, the use of constant failure rates for any End of Life prediction is not valid.

Knowing the future will help to be prepared, but how can we predict the end of life situation?

SD.Comparable to weather prediction, any short-term prediction is likely to be more accurate then the long-term prediction. Short-term predictions are generally based on the actual status of the system, which is the result of the history of usage, maintenance and environment. The older a system is, the nearer the end of life moment will occur and so the better the end of life forecast can be. Combining initial life expectation with Physics of Failures and actual health status will deliver the best predictions for the end of life situation. The approach is based on the identification of potential failure modes, failure mechanisms and failure sites for the product at a particular lifecycle loading condition. The stress at each failure site is obtained as a function of both the loading conditions and the product geometry and material properties. Lifecycle loads of a product can arise from manufacturing, shipment, storage, handling, operating and non-operating conditions. The lifecycle loads (thermal, mechanical, chemical, electrical, and so on), either individually or in various combinations, may lead to performance or physical degradation of the product and reduce its service life.

Looking at the enormous sizes of the oil and gas plants, there is probably a lot of data to deal with?

SD. Yes, but basically there are two types of degradation: natural and forced degradation. Natural degradation is age or time-dependent. The term ageing refers to an internal process in systems where gradual degradation occurs, thus it brings the systems closer to failure. However, forced degradation that is external to systems, where its loading gradually increases in response to increased demand so that a point is reached beyond which the systems can no longer safely carry the load. To deal with all the relevant data we use our SIAS expert system. This system combines experienced-based approaches, model-based approaches, knowledge-based approaches, and data-driven approaches to determine the right prediction. The SIAS system includes the life calculation algorithms that are known and supported by many international standards. Using this system with an easy connectivity to the clients maintenance management systems most of the data can be treated automatically.

What benefit will knowing the remaining life of their asset bring for your clients?

SD. For the shareholders it will be the best basis for the calculation of the needed investment in the coming 20 years in order to make a proper analysis of their expected revenue. For the plant managers it will ensure that their asset base is fit for purpose for the next 20 years and beyond. It will minimise risk from unplanned production downtime, high-unplanned Capex, and negative impact on health and safety performance.

But the most important benefit will be the continuous assurance of the safety of all operational plant staff in the field.

Biography

Stanley Deighton has spent most of his working time in the Middle East dealing with issues around asset integrity. As a well known lecturer he is seen as one of the authorities in the field of IEC 61508 functional safety. He started his career as an integrity engineer and not long after started his consultancy job in Kuwait, Oman, Abu Dhabi, Dubai and Qatar. Now manager for Stork in the Middle East, all projects related to integrity for the coming 20 years are his ultimate challenges.