Preface
When my son graduated from Texas A&M University, he was understandably eager to start working, and begin earning a livable salary. He accepted a maintenance engineering position at a large chemical complex, and embarked upon learning about process machinery. In the months and years that followed, he and his colleagues had many questions concerning a variety of machinery problems. From my perspective, most of these problems had been solved twenty or thirty years ago. However, it was clear that the new engineering graduates were devoting considerable effort attempting to unravel mysteries that had already been solved.
The obvious question that arises might be stated as: How come the new engineers cannot refer to the history files instead of reworking these issues? A partial answer to this question is that the equipment files often do not provide any meaningful historical technical data. Major corporations are reluctant to spend money for documentation of engineering events and achievements. Unless the young engineers can find someone with previous experience with a specific malfunction, they are often destined to rework the entire scenario.
Although numerous volumes have been published on machinery malfunctions, there are very few technical references that address the reality of solving field machinery problems. This general lack of usable and easily accessible information was a primary force in the development of this text. The other significant driving force behind this book was the desire to coalesce over thirty-three years of experience and numerous technical notes into some type of structured order that my son, and others could use for solving machinery problems.
This is a book about the application of engineering principles towards the diagnosis and correction of machinery malfunctions. The machinery under discussion operates within the heavy process industries such as oil refineries, chemical plants, power plants, and paper mills. This machinery consists of steam, gas and hydro turbines, motors, expanders, pumps, compressors, and generators, plus various gear box configurations. This mechanical equipment covers a wide variety of physical characteristics. The transmitted power varies from 50 horsepower, to units in excess of 150,000 horsepower. Rotational speeds range from 128 to more than 60,000 revolutions per minute. There is a corresponding wide range of operating conditions. Fluid temperatures vary from cryogenic levels of minus 150°F, to values in excess of plus 1,200°F. The operating pressures range from nearly perfect vacuums to levels greater than 40,000 pounds per square inch. Physically, the moving elements may be only a few feet long, and weigh less than 100 pounds — or they may exceed 200,000 pounds, and cover the length of a football field. In virtually all cases, these process machines are assembled with precision fits and tolerances. It is meaningful to note that the vibration severity criteria for many of these machines are less than the thickness of a human hair.
In some respects, it is amazing that this equipment can operate at all. When the number of individual mechanical components are considered, and the potential failure mechanisms are listed, the probabilities for failures are staggering. Considerable credit must be given to the designers, builders, and innovators of this equipment. They have consistently produced machines that are constantly evolving towards units of improved efficiency, and extended reliability.
The majority of machinery problems that do occur fall into what I call the ABC category. These common problems are generally related to Alignment, Balance, and incorrect Clearances (typically on bearings). Due to the continual appearance of these malfunctions, an entire chapter within this text has been devoted to each of these subjects. Machines also exhibit other types of failures, and a sampling of common plus unique problems are described within this book.
Some people might view this document as a textbook. Others might consider this to be a reference manual, and still other individuals might use this book for troubleshooting. It has also been suggested that this book be categorized as a how to do it manual. Since 52 detailed case histories are combined with numerous sample calculations and examples, each of these descriptions are accurate and applicable. In the overview, the contents of this book cover a variety of machinery malfunctions, and it engages the multiple engineering disciplines that are required to solve real world problems. Regardless of the perception, or the final application, this is a book about the mechanics, measurements, calculations, and diagnosis of machinery malfunctions. I sincerely hope that this text will provide some meaningful help for students, for new graduates entering this field, as well as provide a usable reference for seasoned professionals.
Finally, I would like to extend my deepest personal thanks to John Jensen of Hewlett Packard for the inspiration, encouragement, and opportunity to write this book. I am further indebted to John for his detailed and thorough review of much of the enclosed material. I would also like to thank Ron Bosmans, Dana Salamone, and Pamela Puckett for their constructive comments and corrections.
Robert C. Eisenmann, Sr., P.E.
October 1997
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