The latest generation of advanced maintenance technologies represents a quantum leap forward in plant safety. These technologies can strengthen your plant’s in-house safety program in ways that reduce risk associated with the monitoring, inspection, lubrication and installation of rotating machinery.
Monitoring electrical erosion
One such advancement involves the detection of electrical erosion. In some electric motor applications, variable frequency drives can induce shaft voltages to increase, causing electric currents to pass through motor bearings and frames. This can cause fluting damage to bearings and premature motor failure.
Previously, detecting electrical erosion required the use of direct-contact probes operated by experienced technicians. The latest technologies do not require direct contact with operating motors.
A recently introduced electrical erosion detector, for example, employs proprietary technology to monitor electrical pulses. Users hold the detector at a range of about 12 inches from operating motors. The detector counts electrical pulses for 10- or 30-second intervals, then displays the count on a built-in screen. When excessive electrical erosion is detected, the malfunctioning motor can be promptly removed from service and repaired in advance of failure.
Stroboscopes and thermography
Recently at a large paper mill, a technician employed a hand-held stroboscope to inspect a problem coupling in a dryer supply fan, a critical papermaking application. The inspection revealed that the coupling was loose and would soon have to be repaired. A decision was made to replace the coupling during an upcoming planned shutdown, averting a costly failure during operation.
Thermography detects radiated energy in the spectrum’s infrared band. Thermal cameras, which operate much like digital cameras, produce live thermal images of operating machinery, allowing users to monitor and gather data on machines located in inaccessible or dangerous locations. The cameras can detect temperature anomalies or “hot spots” from a distance and over a wide area. The thermal images can be saved and uploaded to a PC for in-depth analysis.
Traditionally, maintenance techs manually relubricated rotating equipment, sometimes as frequently as once a week. Manual relubrication, however, is laborintensive and requires workers to enter potentially dangerous areas and work close to operating machinery.
In certain applications single-point automatic lubricators provide a safer alternative. These self-contained lubricant canisters attach directly to machines and supply a consistent, regulated flow of grease to lubrication points, eliminating the need for manual relubrication. Although single-point automatic lubricators can operate for up to a year without replacement, they typically have a limited lubricant capacity and are not suitable for most heavy-duty applications.
The recent debut of higher-capacity, multi-point lubricators has extended the range of automatic lubricators. One system has a lubricant capacity of 420 milliliters. It distributes grease or oil to separate lubrication points through as many as eight feed lines. The feed lines measure up to 16 feet in length. These multi-point systems are specifically designed for heavy-duty applications such as hot gas fans and calendar rolls in paper mills.
To prevent failures due to lubricant deterioration, lubricant quality can be assessed with newly available devices such as hand-held oil check monitors. The instruments compare samples of used oil with fresh oil of the same brand and type, detecting changes in the used oil’s dielectric content. The changes are associated with factors such as mechanical wear, contamination and oxidation. Trends detected by oil check monitors can prompt an oil change in advance of failure.
Bearing installation and removal
New heavy-duty induction heaters are designed for installing large bearings in steel, mining and papermaking applications, and for components such as couplings, gear wheels and housings that form a closed circuit. The tools allow companies to eliminate the heating of bearings and other components in oil baths, which pose safety and oil disposal issues.
Some varieties of heavy-duty induction heaters can handle bearings having bore diameters of 7.2 inches or more and weighing up to 2,600 lbs. These heaters usually reduce energy consumption by approximately 50 percent compared with older induction heaters.
In applications having medium-size shafts, hydraulic tools can be used to safely mount bearings, couplings and other components. Hydraulic nuts employ a hydraulically powered piston to press components onto shafts, often replacing hammers, drifts and lengths of pipe as mounting tools.
When bearings or other components are removed, hydraulic nuts can be turned around and deployed as stoppers. This prevents components from exiting the shaft with excessive force, posing safety risks for workers. New varieties of bearing pullers are also designed for safe removal of rotating components without shaft damage.