Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/704613
32 July - August 2016 | www.machinerylubrication.com MAINTENANCE AND RELIABILITY Converting to the Prevention Paradigm The "Seen" Situation A Change of Methods The "Unseen" Situation • Record all breakdowns. Analyze and group by area. Track by computer. • Find the 20 percent that are causing 80 percent of the effort. • Assign each as a project. Put someone in charge. • Start a kaizen project of continuous improvement ideas. • Chart breakdown time to show progress. • Do you standardize on maintenance material such as lubes, pumps, valves and filters? • Do you use a CMMS? • Do you train personnel regularly? • Do you computerize lube lists to reduce errors? • Is equipment tagged with the proper lube? • Do lube technicians have routing sheets to maximize effectiveness? • Do managers attend conferences for new ideas? • Do you repair everything or do you send out some items? • Do you continually ask, "Why do we do this?" or "Why do we do it this way?" • Do you ask, "What causes most of our crises?" • Do you employ regular PM inspections? • Do you perform condition monitoring or lab tests? • Do you require routine checks of temperature, pressure and flow that might catch incipient problems? Are these numbers recorded? • Do you recognize the value of people who prevent bad things from happening? • Has anyone diagnosed where your mainte- nance dollars are going? • Do you set goals for downtime reduction? sounded, maintenance personnel knew they had only a few minutes to switch the three-way valve to the clean side before a shutdown occurred. A clean filter element was always on standby. The result was that the servo-valve failures virtually ceased. Once again, a simple design change prevented a serious problem. However, the difference with the servo-valve issue was that production was being affected as well as repair costs. Excessive Oil Losses Oil losses were becoming excessive in the mill's hydraulic and lubrication systems. The millwrights dutifully kept the systems filled and operating but did not report all the oil additions as they were made. When additions were reported, there was no good method for determining the amount. Therefore, it was difficult to establish where the bad leaks were and to schedule repairs. Prevention or reduction of these oil losses was the goal, but they could only be attacked when they occurred. The decision was made to mount small water meters on the fill lines to each system. These meters had some internal friction, but since the oil was being pumped in as makeup oil, the pressure required was adequate. In cases where the oil flowed by gravity from an upper to a lower floor, low-friction meters were required. Each day, an inspector read the meters to deter- mine if any leaks had gone unreported. If so, action was taken. This was an example of taking preventive action (reading the meters) to prevent further losses. No action could be taken without proper information supplied by the meters. Rapid Motor Burnouts The plant's coke oven doors are approxi- mately 20 feet tall and 4 feet wide. They are made of steel, lined with firebrick and weigh about 1,000 pounds. Each is mounted verti- cally on each end of the oven and must be lifted off by a huge machine so the red-hot coke can be pushed out. The doors are held in place by two steel arms that are rotated into place behind vertical "buckstays." In the center of the arms is a hexagonal nut that is 5 inches in diameter. The arms are rotated by a large socket that fits the hexagonal nut and is oper - ated by a motor and gear reducer mounted on the machine. The arms often become wedged behind the buckstays, so an electrician must hold in the overload relays to get the motor to turn. Frequent motor burnouts were attributed to this practice. Rather than increase the size of the motors, the decision was made to convert the opera - tion to hydraulic motors due to the inherent overload protection in such a system. Relief- valve adjustment serves this purpose. Because of the large amount of dirt inherent in the coke plant and the dirt sensitivity of the hydraulic motors, the hydraulic systems were redesigned. This redesign was so successful that no hydraulic motor failures occurred for the first five years. The improved cleanliness also increased pump life. This case was an example of prevention involving a radical design change with which not everyone agreed. Unchecked Oil Temperatures At another hot mill in the Pittsburgh area, the challenge was determining the cause of losing several back-up bearings. It seemed to be a case of the oil overheating, but when the