Don't wait for failure Part I

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Don't wait for failure Part I

August 08, 2010 - 16:00

BRUSSELS, Aug. 9, 2010 (RISI) -Pulp and paper mills are under ever-increasing pressure to meet shareholder expectations of increased profitability through improved plant efficiency. Machinery problems can make it harder to meet this challenge, not only by affecting product quality but also by causing mill downtime. To minimize this downtime, maintenance must be carefully scheduled so that it occurs prior to a machine failure - but not so often as to incur unnecessary maintenance costs. Today, more and more mills are upgrading their maintenance programs by adding condition-based monitoring activities. Using equipment with predictive diagnostic capabilities enables these mills to identify potential problems in critical machines before they fail. The machine can then be allowed to continue performing within acceptable parameters until it can be repaired at the most economically convenient time.

Monitoring the health of rotating machines and bearings is fundamental to predictive maintenance programs within paper mills. Rolling bearings and gearboxes can be found throughout every mill and are critical to the smooth running of the plant. Simple process changes like misaligning a stretch roll can destroy bearings and result in significant downtime. Barring or chatter can cause variation in caliper or basis weight, which leads to poor product quality. A single bearing or asset malfunction can result in a significant machinery failure. A proven and highly reliable solution for monitoring the condition of bearings is therefore crucial.

Predictive maintenance of rotating assets including bearings is best practiced using information gathered through vibration monitoring. Sometimes these data signal big trouble down the road, enabling analysts to make a judgement as to when a failure may occur. Based on their prediction, immediate repairs may be necessary to avoid a catastrophic failure or it may be possible to delay repairs until a scheduled plant shutdown - or let them go altogether.

Ultimately, vibration monitoring technology helps the plant and maintenance managers make business decisions about what to do - and when and how to do it. The result is generally a far less expensive proposition than reacting after something breaks.

Yet, according to a Deloitte & Touche study, more than 50% of industry maintenance man-hours are spent fixing equipment after a failure has occurred, and only 18% determining when equipment might fail and fixing it before that happens. Those numbers will improve as more maintenance departments implement solid predictive maintenance programs based on online vibration monitoring of key machines. The "most critical" category of these key machines usually involves only about 5% of rotating assets, but this small number of machines represents an easy target for a complete online monitoring solution - with potentially enormous financial returns on a single "find" before any failure affects production.

Overall vibration levels are displayed so the operator can immediately see any effects process changes may have had on machinery

Online monitoring

Vibration data collection and analysis are traditionally performed periodically using handheld portable equipment. The effectiveness of this type of analysis is very much dictated by the frequency that the data is collected and is particularly important for "balance of plant equipment" such as motors and pumps. The catastrophic failure of many rotating machines can often occur with little warning, so even with regular analysis a failure could occur between two analysis periods.

It is therefore preferable to undertake continuous online monitoring where practical. Which machines get this level of scrutiny will depend on the value of the device and how critical it is to the running of the plant.

Continuous online monitoring of rotating machinery uses technology well beyond systems that provide only periodic snapshots of a machine's condition. Data from automated monitoring systems enable plant personnel to predict with greater accuracy when a machine will need maintenance to prevent consequential damage and avoid lost production. At the click of a mouse, spectral/waveform data from any asset being monitored can be viewed and analyzed. Machine faults such as imbalance, alignment, and looseness are very quickly identified so the maintenance team can determine the locality of the fault and how to repair it.

Critical equipment can be watched automatically for changing vibration patterns and rising temperatures - sure signs of impending trouble. The latest continuous monitoring solutions offer exception-based reporting and event-driven collection to ensure that maintenance personnel are only alerted of real problems, not overwhelmed by time-based data collection. This helps keep highly trained analysts focused on problems resulting in valuable time savings.

This is Part I of the "Don't wait for failure article". Part II can be readhere