Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1005929
www . machinerylubrication.com | July - August 2018 | 35 ML ical in this application? Because the MOVs are tested by measuring the force of the motor through power signal analysis. By looking at the power signature of the motor, the closing force of the valve was inferred. is is only valid when the coefficient of friction for the stem and stem nut interface is properly accounted for. If a stem is not fully lubricated, and the friction is higher than the calculations assume, then the force (and thus the power signature) normally sufficient to fully seat the valve is suddenly inadequate. Knowing the challenge at hand, I returned to the lab to try out some solutions for relubricating the stem. Our first efforts failed, as we were unable to design a fixture that could be connected to the valve stem and deliver the high pressure of new grease required to displace the old and provide a new, reliable layer of lubricant. It was at a picnic where I got the chance to discuss this problem with my uncle. Roy Leitz had a long career as a welder and pipefitter. He was also used to solving difficult problems. One such challenge he had was in sealing the high-vacuum valves of NASA's space simula- tion vacuum chamber in Sandusky, Ohio. As he told me the story of how his team had overcome the challenges of sealing out the atmosphere to produce the world's largest vacuum chamber for simulating the conditions of space, we came upon a design solution for fixing the leaking fixture to relubricate the valve stem. e result was a new way to lubricate valve stems in critical appli- cations like the MOV by taking a completely different experience and applying what had been learned. Not only had we developed a way to relubricate the valve stem, but in the process had created a new sample of the grease that had been in service, offering the potential for new condition data from the grease. It took a long and painful experience in analyzing hundreds of meaningless samples to help me realize the importance of lubricant sampling. e best analysts at the top laboratories in the world cannot produce meaningful results from samples that have been taken incorrectly. It is essential that we focus not only on the task of gener- ating analysis data but also in ensuring that the data will have value. is can only be achieved with accurate and representative samples from motor-operated valves and all other critical grease-lubricated machines. ML