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Sat 25 Jul 2009 04:00 AM

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Refinery maintenance

A critical aspect in petrochemical industry is plant maintenance. Petrochemicals Middle East investigates in the issue.

Refinery maintenance
Tube face of a vertical combined feed exchanger – often called a Texas Tower (Photo courtesy of Tubetech).
Refinery maintenance
Vertical combined feed exchanger (VCFE) before cleaning at one of the most productive refineries.
Refinery maintenance
Vertical combined feed exchanger (VCFE) after cleaning at one of the most productive refineries.
Refinery maintenance
Mike Watson, managing director, Tubetech International.
Refinery maintenance
Johan Claassen, business development manager Emerson.

A critical aspect in petrochemical industry is plant maintenance. Petrochemicals Middle East investigates in the issue.

Every business owner wants to increase production whilst reducing expenditure and within the oil, gas, petrochemical and energy industries an additional desire – or should we say necessity – is the reduction of CO2 emissions.

Within oil refineries, maintenance is about avoiding emergency critical path situations. It is about identifying problems before they become cause for concern and getting the large, difficult tasks finished so that shutdowns can be shortened. Often these problems are cleaning and inspection related.

“Maintenance is a pretty wide concept and normally consists of two types of maintenance: proactive and reactive,” says Johan Claassen, business development manager, PlantWeb services, asset optimisation group at Emerson.

Proactive maintenance is a maintenance strategy for stabilising the reliability of a refinery. Its central theme involves directing corrective actions aimed at root causes of failure, not active failure symptoms, faults, or machine wear.

Reactive maintenance is a form of maintenance in which equipment and facilities are repaired only in response to a breakdown or a fault. Because of the potential for loss of production, reactive maintenance is at odds with just-in-time production. “People call it fire fighting maintenance and it occurs only when there is breakdown,” says Claassen.

“People want to move from the reactive maintenance to proactive maintenance to avoid loss of money,” he adds.“Refinery maintenance presents challenges in various areas and one of those targets is the quick, efficient cleaning of heat exchangers and other plant assets. Often regarded as a ‘traditional’ procedure, it is crucial that clients encourage a more inventive approach to achieve successful de-scaling whether for performance or for integrity inspection,” says Mike Watson, managing director of the UK-based Tubetech International company.

Challenges

“Keeping the skilled people is the biggest issue, especially if you have the right people they stay for two years and then leave,” says Claassen. “Aging equipment and refineries are also a challenge that needs to be addressed,” he adds.

Communication of maintenance history is also a challenge. “It is rare that refineries possess accurate historical data on previous cleaning or inspection activities and what exists is often pitifully inadequate,” says Watson. “In our twenty year history, we have never once found a refinery that could provide archives on how something has been cleaned – ie: pressures, volumes used, technology applied or any other significant information which could hold the key to improving performance the next time around,” he adds.

Invariably, the comments from refinery personnel refer to ‘pressure jetting’ or ‘chemical flushing’ and very little else. A clear and precise information gathering strategy is crucial to understanding the details of the problem – information such as limitations of access, deposit characteristics – all of which help contractors to apply the best technology in the most efficient manner.

This information reduces the chance of ‘bottlenecking’ by preparing and understanding a cleaning problem before it occurs, planning for the best cleaning technology which benefits plant performance, reduces the cleaning time, increases energy savings and reduces the CO2 footprint.

“Refinery engineers really need to accurately record cleaning activities, ROT HIT values, and heat transfer co-efficient data i.e. new operational performance data, performance data prior to cleaning and performance data after cleaning,” says Watson. “This information is rarely, if ever, shared with the contractor or indeed the plant engineers, yet is crucial to motivate contractors and plant personnel alike to deliver best practice,” he adds. “Within our lengthy contract questionnaire, we request information about the units to be cleaned but also ask for detailed performance information. The reason for the comprehensive questionnaire is to ensure that refinery operators are able to record the increase in performance that a true conscientious specialist cleaning service will provide,” Watson says. Timing

“Marketing people have a term for the purchasing of things we have to buy but would rather not. It’s called ‘distress purchasing’. Maintenance and the cleaning of heat exchangers in particular fits firmly into the category of distress purchase,” says Watson.

No business wants to stop production in order to clean, or pay for it to be done. “When the plant returns to duty, it rarely shows the significant performance improvements expected. Given the frequently disappointing results of cleaning, it is understandable that businesses don’t want to pay any more for it than they have to, so they will invariably opt for the cheapest provider,” he says.

“That’s the way it has always been and maintenance budgets are geared to it, so why change?” he adds.

Globally, everyone still uses the same cleaning technology used since the 1940s and 50s, namely high pressure jetting. Nothing has changed, other than increasing the water pressure.

“The competition helps maintain downward pressure on prices. On the face of it, that can only be good news for the customer, but invariably excessive price competition means corner-cutting and reduced quality and safety,” says Watson. “Things never get better, because the cleaning contractors don’t have the money to re-invest in more advanced cleaning technologies,” he adds.

“Imagine if the job can be done five times faster and use 90% less water” says Watson.The best time to conduct refinery maintenance is sooner rather than later. Regular maintenance of heat exchangers, fin fans, furnaces and flare lines means that blockages and heavy scaling should not cause unplanned shutdowns, which end up costing refinery operators dearly.

The norm of refinery maintenance is between 10 to 14 days. “Normal maintenance requires between 10 and 14 working days, but if it is the full refinery maintenance where the full refinery is down, it takes between 20 to 30 days. This kind of maintenance happens generally every six years,” says Claassen.

Cost

“A typical quote for traditional high-pressure water jetting of a heat exchanger using 10,000 psi pressure could include an undertaking to do the job two days faster. It might save $350,000 over a 21 day shutdown. Imagine if the job can be done five times faster and use 90% less water: the savings now include huge reductions in water usage and disposal,” says Watson.

Classic high-pressure jetting of shell-side bundles uses around 250 gallons per minute, every hour, during every ten hour shift – that’s around 150,000 gallons per day, or over 3 million gallons in the course of a 21 day shutdown. A 90% reduction reduces that to just 315,000 gallons to be handled and disposed of and a corresponding reduction in chemicals used to treat the waste.

Everyone is aware of and mandated on the impact their industries have on the environment. The effective cleaning of heat transfer equipment can by default help refinery operators reduce their CO2 emissions.

The cleaner something is, the less CO2 emissions it will produce. One therefore has to question why refineries continue to use cleaning technology and practices that have not changed in the last 50 years. Predictive maintenance

Predictive maintenance (PdM) techniques help determine the condition of in-service equipment in order to predict when maintenance should be performed. This approach offers cost savings over routine or time-based preventive maintenance, because tasks are performed only when necessary.

“Plant predictive maintenance became a necessity where equipment can tell you when it needs maintenance and what is needed to be done. There is technology now that tells you there is maintenance to be done,” says Claassen.

The ultimate goal of PdM is to perform maintenance at a scheduled point in time when the maintenance activity is most cost-effective and before the equipment loses optimum performance.

This is in contrast to time- and/or operation count-based maintenance, where a piece of equipment gets maintained whether it needs it or not. Time-based maintenance is labour intensive, ineffective in identifying problems that develop between scheduled inspections and is not cost-effective.

Predictive mainatenance should be used as “prevention is better than cure.”

Predictive maintenance

Predictive maintenance (PdM) is the techniques which help to determine the condition of in-service equipment in order to predict when maintenance should be performed. This approach offers cost savings over routine or time-based preventive maintenance, because tasks are performed only when necessary.

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