Machinery Lubrication

Machinery Lubrication July - August 2018

Machinery Lubrication magazine published by Noria Corporation

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24 | July - August 2018 | www . e outcome of the investigation led to the U.S. Navy implementing a new program to address submarine safety. is program was known as "SubSafe." The SubSafe program required detailed written procedures and checklists to be developed and followed to the letter by all personnel engaged in maintenance of specified components of all systems affecting submarine safety. To date, the Navy has not lost a submarine due to a maintenance mistake under the SubSafe program. is shows the impact that a robust procedure-based maintenance program can have on reliability and safety. Later in the 1960s, there was a focus on improving the reliability of commercial aircraft. is study, which was published by Nowlan and Heap, brought to light that most failures were not induced by time or wear but were either random or triggered by improper maintenance or installation. Looking at the six failure patterns, it was observed that failure pattern six, which experi- ences a high level of infant mortality followed by a random, consistent failure rate, was more prevalent at 68 percent. is indicates that the highest probability of failure is when the equipment is new or just over- hauled. So, what led to the spike in the probability of failure? e causes could be related to design, manufac- turing defects, installation defects, improper commissioning, improper routine maintenance, and mainte- nance workmanship. Considering the causes of the high probability of failure for new or recently overhauled equipment, it was determined that more main- tenance was not the answer. e solution was related to controlling the variation in activities. ese activities included such things as design reviews, supplier quality and certif ication programs, and the development of procedures for operating and maintaining equip- ment. ere was a conscious effort to move away from relying upon on-the-job training, intuition, etc., toward the use of detailed, technical procedures. As a result of these changes, along with the move to condition-based maintenance from time-based maintenance, world- wide aircraft incident rates have fallen from nearly 40 incidents per 1 million takeoffs in the early 1960s to just one or two incidents per 1 million takeoffs in 2016. Importance of Procedures Procedure-based maintenance serves to address two key issues when performing maintenance activities. First, it reduces the variation that occurs when many craftspeople are conducting the same work. Consider how many ways there are to rebuild a pump. How does the disassembly happen? Does the disassembly occur with a precision torch and hammer, or does it take place with the proper tools? Does the rebuild happen in a clean room or in a dirty shop which can contribute to contamination? Are the parts inspected according to a standard or left to the experience of the rebuilder? Is there a standard list of parts that are replaced, or is it left to the inspection? Is a thread- locking component used during reassembly? A re the clearances checked based on experience or tech- nical specifications? Are fasteners tightened using a torque wrench or the strength of the rebuilder? How is the pump tested before being put back into stock or service? If you were to ask a group of craftspeople these questions, you likely would get a wide range of answers, and two people would not have the same process for rebuilding and commissioning a pump. is variation makes it virtually impossible to establish a root cause of a prema- ture failure or poor performance of a rebuilt pump. A procedure based on the experience of the staff can capture the collective knowledge and put it into a repeatable and consistent method, eliminating this variation. S ec ond ly, proc edu re-ba sed maintenance minimizes the odds of an individual making a mistake. ere are various types of factors that can contribute to an error, and it is important to understand these factors to ensure that procedures are written to address them. For example, anthropometric factors are those related to the size or strength of the person performing the activity. These are primarily addressed through a redesign or tools and not with procedures. Human sensory factors are those concerned with the ease in which people can see, hear, feel and even smell what is going on around them. ese are also mainly addressed by redesigning or with tools and not through procedures. Physiological factors refer to environmental stresses, such as high or low temperatures, excess noise, humidity, etc. Once again, these cannot be addressed through procedures. Psychological factors are related to the causes of which mistakes are made. Psychological errors are divided into two types: unintended errors, which occur when someone does a task incorrectly, and intended errors, which happen when someone MAINTENANCE AND RELIABILITY

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