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possible if the right maintenance tech- nologies and people are chosen and supported with investment in training. In terms of maintenance phi-

losophies, running to fail is the most expensive, followed by scheduled, periodic maintenance. Not all mainte- nance can be performed on a periodic basis, so a condition-based component can be added to a dominant periodic maintenance program. A next step in maintenance is to use a predictive maintenance plan with a condition- based component. Te longer you can extend the time

to failure on the equipment, the better the ROI becomes. Te bathtub curve in Fig. 1 shows that the sooner a failure mode is detected and corrected, the cost of the repair will be lower and the need for replacement will be delayed. Aarrowcast Inc. (Shawano, Wiscon- sin) uses various forms of work requests or work instructions that form the inputs and outputs of its computerized main- tenance management system. Operator- based maintenance is ordered, per- formed and tracked just like scheduled maintenance. Predictive maintenance procedures are scheduled, performed, and tracked as well. When any of the processes are reviewed, the CMMS is updated to the desired change. Retaining the processes in this way

protects Aarrowcast and its customers against the loss of intellectual assets. If a technician leaves, a training docu- ment is available to sustain the process. Aarrowcast’s predictive maintenance system involves equipment operators working closely with maintenance technicians to make sure the processes are working as defined. Maintenance and production supervisors are the first level of quality assurance, while the predictive maintenance group is the second level. Te operators are given periodic training on predictive main- tenance because they are the ones who do most of the routine operational inspections and lubrications. Every time a new asset comes

online, Aarrowcast performs baseline monitoring and equipment commis- sioning. Te testing processes and equipment qualifies Aarrowcast to make sure the equipment performs as specified in the purchase order. Te

Table 1. Estimated Investment in Data Collectors


IR Thermography Ultrasound DCA Vibration DCA

Motor DC/Analyzer Power Logger

Misc. Other Electrical Misc. E/M Test Equip.

Cost 4,000

11,000 22,000 25,000 6,000 5,000 5,000

to a proportional range of frequen- cies humans can hear. Certain noises, based on their origin, can be tuned in and given a decibel value. A bearing’s noise level, for example, is trended using a 25 kHz frequency. As this level is tracked, the technician can moni- tor whether it needs lubrication or is entering a fault condition. Aarrowcast uses ultrasonic analysis

metalcaster can test the equipment’s performance before the supplier leaves the premises, preventing costly returns and contract disputes.

Predictive Maintenance Technologies At Aarrowcast a number of predic-

tive maintenance technologies are used, including vibration analysis, thermal imaging, ultrasonic analysis, oil analysis, and power condition and monitoring. Aarrowcast’s vibration analysis database includes more than 1,600 data points with 87-91% updated weekly or bi-weekly. Te remaining are updated as opportunity or needs arise. Te detection of problems has improved and increased as training and experi- ence has grown. Ultrasonic shock pulse monitoring recently has been added to its suite of automatic vibra- tion tests if the device being tested is rotating at less than 600 RPM. Infrared cameras perform thermal imaging of electrical components and check the bearing, gearbox, refrac- tory and bin levels temperatures for hotspots. Te detection of an unde- sired temperature (either too hot or too cold) has long been used to find problem areas. Tis technology assists others, such as vibration and ultra- sound, to provide additional infor- mation about what stage of failure the device being tested may be in. Temperature loggers attached to the process enables Aarrowcast to calcu- late trend values for time/load/func- tion correlations. Friction and turbulence produce

ultrasonic noise the human ear cannot hear. Ultrasonic instruments are tuned to frequencies as high as 100 kHz. Te unit processes the signal down

in conjunction with infrared imaging on electrical apparatus because ultra- sound can “hear” a fault condition that infrared may not “see” and vice versa. Ultrasonic analysis can be used

to test valve functions and pump operations. Te detection of airborne ultrasonic turbulence generated by a compressed air leak can be used to reduce energy losses from a com- pressed air supply. Oil analysis, which Aarrowcast

outsources to the oil supplier, is conducted on samples taken during scheduled maintenance or as a special sample taken to back up vibration or ultrasonic technologies. Results are reviewed and work orders generated to respond to needs as determined. Routine online and offline motor

tests on critical equipment through- out the plant can be used to evaluate power supply problems and monitor motor conditions. Offline motor test procedures

include gathering inductive, capacitive and resistive values in the de-energized motor circuit. Te motor’s insulation properties are evaluated and trended along with the levels of imbalnance that exist among the components. Other testing and data collecting

procedures include stroke monitor- ing of vibratory conveyors, dew point monitoring, laser alignments, precision lubrication, fan wheel balancing, root cause failure analysis and continuous process improvement. Stroke monitoring can be used to

monitor the wear in drive compo- nents and how it effects the stroke of the conveyor. Dew point monitoring of the air discharging from com- pressed air driers helps in scheduling desiccant material changes when it’s necessary, instead of on a time-based schedule. Te testing procedures also involve making sure the unit

October 2016 MODERN CASTING | 27

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