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Managing process safety in ageing plants to limit risk

9th June 2015


Most industrial plants in the UK and Europe were built between 1960 and 1980 and were expected to operate for no more than 40 years. However, many are still operating today - several years past their expected life span.

A lot of equipment is being still used in accordance with the initially selected design specification, but may not now be capable of functioning as intended.

The UK’s Health and Safety Executive (HSE) suggests that 50% of European major hazard ‘loss of containment’ events arise from technical plant failures due to ageing mechanisms such as erosion, corrosion and fatigue.

Many production sites have changed their processes to suit product developments over time, but not adapted the configurations of components being used within the process to cope with these variations.

For example, some process plants have grown in capacity by increasing operating pressures, which is having a strain on equipment such as safety relief valves and rupture (bursting) discs. It is believed that around a third of relief valves fail to operate as intended because of changing process conditions. The back pressures that were not present when the original design was specified are often not considered by those currently running the plant.

Now in their 'Lifetime extension' period, more intensive monitoring is required to ensure plant equipment is still fit for purpose, and that its safety integrity remains at a sufficient level. Rather than taking a reactive approach, where maintenance spends often exceed production, a longer-term strategy is required to limit the risk of regular equipment failure and safeguard the future of the plant.

According to the HSE, recognising the ageing mechanisms that affect each process and then introducing and maintaining a structured management system approach can mitigate the potential for failure and significantly reduce the incidents of major accidents in the industry.

Rupture disc manufacturers like Elfab support customers in managing this change and assist with the implementation of the latest pressure relief equipment as part of an efficient system. Risk is being limited through the installation of new rupture disc technology and ongoing maintenance costs are being saved as a result. Through joint site surveys to review existing rupture disc specifications, recommendations are made to rationalise stock parts. The replacement of old rupture discs with the latest designs enables obsolete stock to be removed and ensure all installations are kept up to date.

Due to high operating ratios and tighter tolerances offered by the latest  rupture disc designs, multiple old specifications can be replaced by a single disc solution. Less disc variety and greater batch quantities mean that customers are benefitting from greater economies of scale with their pressure relief devices.

Elfab’s Opti-Gard reverse-acting rupture disc offers an industry-leading 3% tolerance and 97% operating ratio. By making the most of these latest improvements in rupture disc technology, stock variety can be reduced by up to 60%.







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