Age concern

How can you tell when a plant asset has reached the end of its working life?

The ‘ageing plant’ label is generally applied when core equipment and systems display a level of wear or obsolescence that raises the prospect of failure.

If an HSE inspector comes along and sees a hanger missing, it can get awkward

DC White MD Doug White

But while the care of this older equipment generally falls to the maintenance crew tasked with keeping it working, a flawed decision to keep an asset running can have ramifications well beyond the factory floor.

Research conducted by the Health & Safety Executive (HSE) showed that 50% of European major hazard ‘loss of containment’ events caused by technical plant failures were mainly “due to ageing plant mechanisms such as erosion, corrosion and fatigue”.

For this reason, the HSE names asset integrity management in ageing assets as one of the key issues to be addressed in its plant inspection programmes.

While making a call on the viability of older assets is not always straightforward, they should not automatically be consigned to the scrapheap.

Appropriate inspection and maintenance regimes can allow some equipment to be pushed well beyond its retirement date, say experts.

“Keeping old equipment working safely makes a lot of sense,” says Doug White, managing director of consulting engineers, DC White.

“It is sometimes the best way for a company to respond to a resurgence of business.”

However, many maintenance staff find themselves too busy firefighting to develop a long-term strategy, with the result that some less visible areas of the plant can be overlooked.

This is often when external experts such as DC White are called in.

To determine the viability of ageing plant assets, the first stage of any inspection is the ‘walk down’, says White, which involves walking around the plant, and talking to engineers to gather a history of past problems.

This is followed up with further inspections of potential problem areas.

“This might be suspected corrosion underneath insulation, or [assessing] missing pipe hangers,” he says.

“Then we ask: ‘is it a problem we can live with and make a safety case for’? For example, we have a technique for analysing pipe supports to determine their safety.

“If an HSE inspector comes along and sees a hanger missing, it can get awkward. But if we can show a safety case that demonstrates it can be operated safely then that is what we are striving for.”

At the end of the investigation, DCWhite presents plant owners with a report that highlights areas of concern as well as “substantiation for those areas getting on in years that can still be operated safely or with provisos”.

“We have seen a wide range of failures over the years and have learned how to recognise the warning signs before failures happen,” says White.

Bosch Rexroth, which supplies electronic drives to the process sector, is seeing more and more companies “opting to upgrade and retrofit rather than investing in new technology,” says Richard Chamberlain, the company’s UK sector service manager.

“In industries affected by cost down pressures, such as food and packaging, we are seeing more small to medium-sized businesses utilising older equipment for longer periods of time,” he says.

“With large end users however, there is more of a willingness to invest in new innovations and technologies in order to stay ahead of the competition.”

One of these is a new service from Bosch Rexroth that enables the company to remotely link to customer plant IT systems, flagging and correcting any potential issues as they arise.

The decision to keep ageing plants open in the oil and gas industry generally comes down to economics, says Alan D’Ambrogio, oil and gas consultancy manager for ABB.

Investment in equipment often depends on the reserves that remain at the site, he says.

“The big question is how do they invest in their assets to ensure another five years of production,” asks D’Ambrogio.

To determine the condition of the asset, he says most operators will use time-based or preventative maintenance strategies.

“But the industry is increasingly moving to condition-based strategies that use technologies such as thermography, vibration monitoring, oil analysis of lubricants.”

One of the key drivers of obsolescence within plant control systems is the fast pace of change says John Rudolph, vice president of lifecycle solutions at Honeywell Process Solutions.

“Technology today is moving extremely fast and things go obsolete every day,” says Rudolph.

Even those systems that are well maintained and routinely upgraded can run out of options, he says, citing the example of Windows XP operating system, which Microsoft recently ceased supporting.

Power plants in particular are likely to have distributed control systems (DCS) nearing the end of their useful lives, says Matt Sigmon, director of DCSNext at Maverick Technologies.

They were leaders in implementing DCS technology, starting in the 1980s with systems based on mini-computers, and many of these are still in place, says Sigmon.

“To keep costs down and reduce downtime, power plants tend to shy away from changes to the automation system, preferring to keep things as is and opting for low-risk solutions,” he says.

However, many are forced to reconsider when they encounter reliability issues with their system, discontinued technical support and spare parts.

“Though replacement may cost more upfront, the far-reaching benefits often make it more economical than attempting to upgrade or retrofit an aging system,” adds Sigmon.

David Humphrey, director of research at ARC Advisory says a strong need to conserve cash in recent years has meant many companies have delayed investments in upgrade projects.

“The delay in upgrades means that ageing, maintenance-intensive assets are being kept in service longer,” says Humphrey.

“At the same time, budget constraints drive the business to cut costs, including maintenance activities.

“Many sites continue to use manual methods to notify maintenance when a repair is needed. Delays and inconsistencies can cause a simple preventive maintenance task to escalate into a failure with high repair costs.”

One solution is to integrate control systems with Enterprise Asset Management (EAM) so preventive maintenance can be scheduled based on actual usage and operating conditions, rather than a fixed time period, says Humphrey.

“Our most recent study on Enterprise Asset Management and Field Service Management software sees high single-digit annual market growth over the next five years,” he says.

“That’s a fairly high growth rate and reflects the need and willingness of process users to invest in maintenance management.”