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Chris Zielewski retired recently from ExxonMobil where he last worked as a Machinery Section Group Leader. He has over 35 years machinery engineering experience with pumps, compressors, turbines and other petrochemical equipment.

Chris served on the Texas A&M Turbomachinery Advisory Panel, and currently is an executive committee member of the Gulf South Rotating Machinery Symposium. His specialty areas include machinery reliability improvements and incident investigations.

Chris holds a B.S. degree in Mechanical Engineering from Rutgers University, New Brunswick, New Jersey.

Your pump's Mean Time Between Repairs (MTBR) is what?...Or what should it be...

Your pump's Mean Time Between Repairs (MTBR) is what?...Or what should it be...
Many of the tourist spots around the world have panhandlers. Some of the more creative ones stand on street corners advertising that they will tell you where you got your shoes, for a dollar. Of course it turns out that “you got your shoes” at the corner of Bourbon and St. Peters - or wherever you happen to be standing at the moment. It’s a play on words. However, being able to predict your pump Mean Time Between Repairs (MTBR) is not a play on words. Indeed it can be done quite accurately. I am often asked to do a facility rotating equipment reliability audit. After all, the plant’s management has heard that top tier plants have pump MTBR’s in excess of 100 months. They would be happy to have half that number. Hence the need to understand the major MTBR influencing factors. The main broad reliability categories that determine what...
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“Speed Kills” – An Empirical Association of Antifriction Bearing Behavior When Things Go From Bad to Worse

“Speed Kills” – An Empirical Association of  Antifriction Bearing Behavior When Things Go From Bad to Worse
Machinery and reliability people have for a long time observed that when it comes to long life and high reliability, operating at higher speeds compares poorly to operation at lower speeds. One of the primary reasons for having high-speed devices is economics. With high speed you can have smaller equipment sizes with fewer stages. While capacity and pressures developed do improve, this often occurs at the cost of increased wear, vibration, noise and maintenance. There are some limits as to how fast and large we can practically go. At some point even the required lubrication systems become very complex. While smaller equipment can use antifriction/rolling element bearings, their application is typically limited by manufactures to a certain speed. When combined with the bearing size, this limit becomes known as a DN number limit, a product of the mean bearing diameter (ID+OD in mm divided by 2) and the RPM. This DN...
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