FEATURE FACILITIES MANAGEMENT
KEEPING THE FANS HAPPY I
Paul Dysiewicz, engineering manager at SKF, explains how choosing the right components and maintenance strategies can help eliminate fan system failure in industrial facilities
f you are reading this at your place of work the chances are that at least one
fan is operating near your right now - probably several. Listen carefully: you might even be able to hear them. Fans are an integral part of most
manufacturing processes, providing ventilation for operating personnel, delivering air or gases to processes or extracting hot or dangerous fumes. Their simplicity and pervasive nature
means fans often don’t receive the same attention as other items of production equipment. However, their integral role means that as companies work their production assets harder fans must work harder – handling hotter gases, faster operation to deliver higher flow rates, extended duty cycles or lengthier periods between maintenance interventions. Increasingly, tougher operating
conditions are taking their toll as fans are asked to do more than their conventional bearings and lubrication systems can handle. The result is an increase in failures, production downtime and maintenance costs.
Does that fan you can hear sound
noisier than it used to? Fortunately, the industry has responded to the challenge with the development of technologies and design approaches that can dramatically improve the reliability and longevity of critical fan components.
BETTER BEARINGS In many everyday fan applications it is problems introduced when fans are installed that sow the seed of their eventual demise. Poor bearing alignment can lead to excessive vibration in use for example, while insufficient, excessive, contaminated or incompatible lubricant can accelerate bearing failure. These issues can be avoided through
the installation of relubrication-free bearing units including the patented SKF ConCentra ball and roller bearing units. These are factory-filled in a clean environment with a long-lasting bearing grease and protected by durable double seals. Perhaps their biggest benefit in both installation and use is the SKF ConCentra locking technology based on two mating surfaces with precision- engineered inclined serrations on their contact surfaces. This provides a true concentric fit that is tight, accurate and
8 OCTOBER 2015 | FACTORY EQUIPMENT
approach can reduce bearing operating temperature by up to 10 ºC and double the lubricant service life at applications operating at 100 ºC. For high-speed operation the total fan
solution uses a contact seal design that can handle speeds of up to 13m/s compared to the 4-8m/s limits of conventional seal designs.
highly reliable even under the most difficult operating conditions.
SMARTER SYSTEMS Getting the best possible performance in more demanding fan applications requires an integrated approach to the selection of bearings, seals, housings and lubrication systems. This is particularly important when varying operating conditions lead to thermal expansion of shafts and other fan components which can greatly increase friction and vibration levels, leading to early failures. The SKF total fan solution for example, accommodates axial displacement caused by thermal expansion of the shaft using a single precision-machined housing containing a self-aligning CARB toroidal roller bearing in the non-locating bearing position and a spherical roller bearing in the locating bearing position. In grease-lubricated applications this
ConCentra locking technology provides a true concentric fit that is tight, accurate and highly reliable even under the most difficult operating conditions
HANDLING HEAT The highest performing fan applications including those used to handle hot gases require special measures to control the operating temperature of components. In grease-lubricated applications for example, specialist bearing housings such as the SE range from SKF include reinforcement ribs to maintain the roundness of the housing bore under high loads and temperatures while the base of the housing is designed with an increased surface area to better dissipate heat. Where high operating temperatures
preclude the use of grease, fans will need to adopt an oil lubrication regime instead. While oil lubrication is traditionally associated with higher costs and maintenance requirements modern systems include features like automatic oil levellers to maintain and adjust lubricant levels during operation and simple, reliable oil cooler cartridges that can be connected to any water supply.
Poor bearing alignment can lead to excessive vibration in use for example, while insufficient, excessive, contaminated or
incompatible lubricant can accelerate bearing failure
MASTERING MAINTENANCE The final vital ingredient in any program to improve fan performance and reliability is maintenance strategy. The right approach depends on the technology and operating conditions of the fan, its criticality to operations and the implications of degraded performance or failure. In some cases it makes sense to use a
full reliability centred maintenance (RCM) approach based on a full failure modes and effects (FMEA) analysis of the fan system to develop an appropriate condition monitoring, inspection and maintenance strategy. Where the fan is less critical simpler streamlined RCM or risk-based maintenance strategies may be more appropriate.
SKF (UK) T: 01582 490049
www.skf.co.uk
/ FACTORYEQUIPMENT
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