Boosting machine productivity and preventing downtime are always key objectives of any manufacturer, but they become critical imperatives during periods of economic downturn. Advanced maintenance and lubrication practices, supported by a new generation of powerful digital technology, can assist productivity initiatives by keeping rotating machines running longer and more efficiently.
Upgrading Maintenance Practices
Improving maintenance practices, even in limited ways, can yield substantial productivity gains. Recently, a power-generating facility in the northeastern U.S. reduced machine failure rates by modernizing its shaft alignment procedures and utilizing a laser-equipped alignment tool. The new procedures generate “live” values of the type and degree of misalignment, allowing for easy adjustments. They provide a more accurate system of detecting and correcting misalignment than manual methods used previously.
The change in alignment methods affects 25 coal-, oil- and gas-fired machines involved in power generation. Following the changeover, the power plant registered a 10-hour annual decrease in misalignment-related downtime, resulting in increased availability, valued at $25,000. The mean time between failure rate for these machines jumped from 30 to 36 months, an increase of 20 percent. Also, since misalignment wastes energy, the plant expects to benefit from reduced energy consumption.
Maintenance audits can identify outmoded practices, such as using sections of pipe to mount bearings, which lead to premature failures. The audits, conducted by a consulting firm or a plant’s maintenance staff, provide a detailed overview of plant maintenance activities. They typically cover bearing handling and storage, bearing installation, shaft and belt alignment, lubrication, condition monitoring, and bearing dismounting. The use and availability of maintenance instruments and tools are also examined. Periodic audits can motivate maintenance departments to upgrade their procedures and train workers in new methods.
A technician employs a sophisticated non-contact detector to check an electric motor for electrical erosion. (Photo courtesy of SKF USA Inc.)
Lubrication management programs are also gaining in popularity as a means of boosting productivity. Designed to maximize a plant’s lubricating effectiveness and to cut costs, the programs generally cover lubricant selection, delivery methods, control and analysis, and improvement goals. Mapping software can be employed to document the lubrication status of every machine point in a plant, including lubricant type, quantity and relube intervals. The software maps out the most efficient lubrication routes and prompts operators to regrease when necessary. The software is particularly useful for small- and mid-size plants that may not have employees specifically responsible for lubrication.
Lubrication programs often utilize labor-saving lubricant dispensing technologies, including automatic lubricators. Lubricators are self-contained canisters that provide a consistent flow of grease to bearings, eliminating the need for periodic manual relubing. They can operate for up to a year without replacement.
One popular type of single-point lubricator features a gas cell that pushes grease from the canister at a predetermined rate when activated. Some lubricators even permit remote operation and are ideal for high-temperature or high-vibration applications. These lubricators are mounted at a safe distance from operating machinery and deliver grease through feed lines measuring up to 10 feet in length.
Advances in digital and condition-monitoring technologies place unprecedented capabilities in the hands of maintenance technicians and enable them to identify warning signs of machine failure earlier than ever before.
One such technology involves the detection of electrical discharges. Electric motors that power fans, pumps and gearboxes are usually equipped with variable frequency drives, which provide greater control and allow for operating speed adjustment. These drives, however, can induce motor shaft voltages to increase, occasionally causing electric currents to pass through the motor frame and motor bearings. This condition, called electrical erosion, can degrade the bearing lubricant and cause fluting damage to the bearings, leading to premature failure.
Previously, detecting electrical erosion required highly trained technicians and the use of direct-contact probes or oscilloscopes. New digital technologies, however, facilitate detection with lightweight, hand-held instruments that do not require direct contact with operating motors. No special training is needed to operate the detector. Once a malfunctioning motor has been identified, it can be removed from service and replaced prior to a bearing or machine failure.
Thermographic images of rotating machines, taken with a thermal camera, enable maintenance workers to practice predictive maintenance by identifying possible “hot spots.” (Photo courtesy of SKF USA Inc.)
A second example involves thermographic technology, which has improved and grown much more affordable in recent years. Thermography detects radiated energy in the spectrum’s infrared band. The latest thermal cameras resemble and operate much like digital cameras. They feature excellent thermal imaging capabilities, enabling maintenance workers to detect temperature anomalies in rotating machinery. Temperatures over large areas can be compared, revealing “hot spots” or problem sectors. The cameras are especially useful for monitoring machines in dangerous or inaccessible plant locations. After the thermal images are produced, they can be saved and uploaded to a computer for analysis.
Managers looking for ways to soften the effects of the current downturn, do more with less, and increase the value of their maintenance functions can put thermography, electrical detection and other recent technological advancements to productive use. With fewer resources and less margin for error, machine reliability takes on an increasingly important role.
Comments? Questions? Send them to Paul at Paul.Michalicka@skf.com .