Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
ROTATING MACHINERY This third volume in a broad collection of current rotating machinery topics, written by industry experts, is a must-have for rotating equipment engineers, maintenance personnel, students, and anyone else wanting to stay abreast with current rotating machinery concepts and technology. Rotating Machinery Fundamentals and Advances represents a broad category of equipment, which includes pumps, compressors, fans, gas turbines, electric motors, internal combustion engines, etc., that are critical to the efficient operation of process facilities around the world. These machines must be designed to move gases and liquids safely, reliably, and in an environmentally friendly manner. To fully understand rotating machinery, owners must be familiar with their associated technologies, such as machine design, lubrication, fluid dynamics, thermodynamics, rotordynamics, vibration analysis, condition monitoring, maintenance practices, reliability theory, and others. The goal of the "Advances in Rotating Machinery" book series is to provide industry practicioners a time-saving means of learning about the most up-to-date rotating machinery ideas and best practices. This three-book series covers industry-relevant topics, such as design assessments, modeling, reliability improvements, maintenance methods and best practices, reliability audits, data collection, data analysis, condition monitoring, and more. Readers will find a good mix of theory and sage experience throughout this book series. Whether for the veteran engineer, a new hire, technician, or other industry professional, this is a must-have for any library. This outstanding new vcolume includes: * Machinery monitoring concepts and best practices * Optimizing Lubrication and Lubricant Analysis * Machinery troubleshooting * Reliability improvement ideas * Professional development advice
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Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Series Page
Title Page
Copyright Page
Dedication Page
Preface
Acknowledgements
Part 1: CONDITION MONITORING
1 An Introduction to Machinery Monitoring
DCS Systems
2 Centrifugal Pump Monitoring, Troubleshooting and Diagnosis Using Vibration Technologies
Introduction
Vibrations Particular to Various Centrifugal Pump Types
Conclusions
Nomenclature
References & Bibliography
Acknowledgements
3 Proximity Probes are a Good Choice for Monitoring Critical Machinery with Fluid Film Bearings
Proximity Probe Benefits
References
4 Optimizing Lubrication and Lubricant Analysis
Introduction
Optimum Reference State
Lubrication Excellence and the Ascend Chart
Bringing Awareness to Lubrication, Contamination, and Oil Analysis
What You Might Not Know About Lubrication
The Lubricant Film
Film Strength
Unlubricated Surface Interactions
Friction and Wear Generation
Mitigating Surface Interactions
Physics and Chemistry
Contamination: The Antagonist to Lubrication
Contamination Control and Condition Monitoring is More Often about Training than Advanced Technology
Contamination Control
Don’t Leave It to Instinct
Creating a Balance Between Exclusion and Removal
Why Perform Oil Analysis
Fluid Properties Analysis
Contamination Analysis
Wear Debris Analysis
Achieving Oil Analysis Success by Looking Holistically
Obtaining a Representative Oil Sample
Clean and Correct Sampling Containers and Extraction Tools
Correctly Located Sampling Ports
Proper Sampling Frequency
Proper and Consistent Sampling Procedures
Forward Samples Immediately to the Laboratory
Ensuring Reliable Testing
Optimized Selection of Tests
Onsite Oil Analysis
Determining the Optimum Course of Action
Accurate Data Interpretation by the Laboratory
Enhanced Data Interpretation by the End-User
Take Corrective Action and Determine the Root Cause
Continuous Improvement and Key Performance Indicator (KPI)
Oil Analysis Tests
Viscosity
Acid Number and Base Number
FTIR
Elemental Analysis
Particle Counting
Moisture Analysis
Interpreting Oil Analysis Reports
Following the Data Trends
Looking Back at the Past
Inspection 2.0: Advances in Early Fault Detection Strategy
Low-Hanging Fruit
Inspection Frequency Trumps High Science
Beware of Short P-F and Sudden-Death Failures
Inspection Windows and Zones
Inspection 2.0 is a Nurturing Strategy
Final Tips to Help Error-Proof Your Lubrication Program
References
5 Troubleshooting Temperature Problems
Temperature Assessments
Bearing Temperature Trending
Compressor Discharge Temperature Assessments
Why Compression Ratio Matters
Reciprocating Compressor Temperature Monitoring
Summary
References
6 Assessing Reciprocating Compressors and Engines
Overview of Reciprocating Compressors
How Accurate are Rotating Equipment and Reciprocating Equipment Analyst Findings?
References
7 Managing Critical Machinery Vibration Data
Beware of False Positives and False Negatives
Vibration Analysis Strategies
Part 2: TROUBLESHOOTING
8 Addressing Reciprocating Compressor Piping Vibration Problems: Design Ideas, Field Audit Tips, and Assessment Methods
Bolt Torque Tables
Chapter Glossary
9 Remember to Check the Rotational Speed When Encountering Process Machinery Flow Problems
10 Troubleshooters Need to be Well Versed in the Equipment They are Evaluating
11 Precise Coupling Properties are Required to Accurately Predict Torsional Natural Frequencies
Introduction
Case Study
Final Thoughts
12 Is Vibration Beating on Machinery a Problem?
What is Vibration Beating?
Field Case Study: “Beating” Effect Caused by Two Closely Spaced Mechanical Frequencies Observed on Two-Shaft, Gas Turbine Drive
Background Information
References
Part 2: RELIABILITY
13 Using Standby Machinery to Improve Process Reliability
Introduction
Raptor Modeling Software
References
14 Gas Turbine Drivers: What Users Need to Know
Overview
Typical Conditions Inside an Industrial Gas Turbine
Effect of Atmospheric Conditions
Protection
Fuel and Fuel Treatment
Gas Fuels
Degradation and Water Washing
Advanced Materials for Land Based Gas Turbines
Condition Monitoring Approaches
Gas Turbine Maintenance Inspections
Final Words of Advice
References
15 Reliability Improvement Ideas for Integrally Geared Plant Air Compressors
Integrally Geared Plant Air Compression Packages
Reliability Concerns
16 Failure Analysis & Design Evaluation of a 500 KW Regeneration Gas Blower
Introduction
Conclusion
17 Operating Centrifugal Pumps with Variable Frequency Drives in Static Head Applications
References
18 Estimating Reciprocating Compressor Gas Flows
19 Use Your Historical Records to Better Manage Time Dependent Machinery Failure Modes
Part 4: PROFESSIONAL DEVELOPMENT
20 Soft Skills and Habits that All Machinery Professionals Need to Develop
21 Developing Rotating Machinery Competency
Part I: Preparing Students to Work with Rotating Machinery
Part II: Steps to Improving Rotating Machinery Competency: Study-Practice-Share
About the Editor
About the Contributors
Index
Also of Interest
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Summary of frequency capabilities of various sensors.
Chapter 2
Table 2.1 ISO vibration evaluation zones.
Table 2.2 ISO Vibration Velocity Limits, Units of mm/s RMS, for Centrifugal ...
Table 2.3 Motion magnified video characteristics.
Table 2.4 ODS vs. motion magnified video. Accelerometer-ODS-Based Pros and C...
Chapter 3
Table 3.1 Where proximity probes and seismic sensors are best used.
Chapter 4
Table 4.1 The optimum reference state avoids waste and excess.
Table 4.2 Possible sources for common elements.
Table 4.3 Assigning particles ISO codes.
Table 4.4 Example oil analysis report
¹.
Table 4.5 Main differentiators between convention inspections and inspection...
Table 4.6 Acronym list.
Chapter 5
Table 5.1a Bearing temperatures guideline (
Celsius
).
Table 5.1b Bearing temperatures guidelines, (
Fahrenheit
).
Table 5.2 Dropping points for various greases.
Table 5.3 The ratio of specific heats.
Table 5.4 Effect of discharge pressure on theoretical discharge temperature....
Table 5.5 Discharge valve temperature valves.
Chapter 8
Table 8.1 Recommended anchor bolt lengths.
Table 8.2 Recommended target torque values for low-alloy steel bolting.
Table 8.3 Torque values for lubricated and IMF coated threads for: ASTM A-19...
Chapter 9
Table 9.1 Affinity laws for centrifugal compressors, centrifugal pumps, and ...
Chapter 12
Table 12.1 Summary of gas turbine vibration levels before and after field ba...
Chapter 13
Table 13.1 Here are the typical Weibull parameters for common process ma...
Table 13.2 Summary of three simulations.
Table 13.3 RAPTOR results from two analysis cases.
Chapter 14
Table 14.1 Typical conditions inside a gas turbine (see Figure 14.16).
Table 14.2 Recommended sensor configurations for gas turbines.
Table 14.3 Hypothetical gas turbine inspection and replacement schedule.
Chapter 15
Table 15.1 Summary of recommended package design improvements to the API-672...
Chapter 21
Table 21.1 Rotating machinery training matrix.
List of Illustrations
Chapter 1
Figure 1.1 As a machine begins to fail, it begins showing signs of distress....
Figure 1.2 Mechanical vibration levels are commonly used to assess the condi...
Figure 1.3 Most monitoring systems are composed of a sensor, signal processo...
Figure 1.4 This hypothetical vibration spectrum illustrates some possible fr...
Figure 1.5 Complex dynamic waveform decomposed into sine wave components.
Figure 1.6 Here is a hypothetical vibration spectrum for an electric motor, ...
Figure 1.7 It is recommended that both horizontal and vertical vibration dat...
Figure 1.8 Control room operators depend on a distributive control system to...
Figure 1.9 Examples of trend plots.
Chapter 2
Figure 2.1 Cyclic nature of vibration considered as waveform.
Figure 2.2 How vibration vs. Time can relate to vibration vs. frequency.
Figure 2.3 Illustration of common forms in which vibrational motion is quant...
Figure 2.4 Types and locations of instrumentation in high value centrifugal ...
Figure 2.5 Typical Uniaxial (left) and Triaxial (right) Accelerometers (appr...
Figure 2.6 Typical eddy current proximity probe construction and implementat...
Figure 2.7 Rolling element bearing defect frequencies.
Figure 2.8 Illustration of lomakin effect stiffness KL in Annular sealing pa...
Figure 2.9 Acoustic modes in constant diameter piping the conventional speed...
Figure 2.10 Common vibration frequencies and their sources.
Figure 2.11 Illustration of natural frequency “fn” resonance and effects of ...
Figure 2.12 Impact test exciters and principle: A brief impact force excites...
Figure 2.13 Using a campbell diagram to predict resonance problems.
Figure 2.14 Typical excitation force sources in centrifugal pump.
Figure 2.15 Description of reason for imbalance and 1x RPM frequency associa...
Figure 2.16 Imbalanced example of orbit and FFT.
Figure 2.17 Illustration of angular and offset misalignment.
Figure 2.18 Misalignment example of shaft orbit and FFT spectrum.
Figure 2.19 Vane pass vibration.
Figure 2.20 Effects of vibration on Off-BEP operation.
Figure 2.21 Subsynchronous vibration.
Figure 2.22 Example of Field Data (waterfall plot) from inboard proximity pr...
Figure 2.23 Fluid whirl/whip example: data from multistage turbomachine.
Figure 2.24 (a) Negative pressure amplitude clipped-off below vapor pressure...
Figure 2.25 Typical torsional critical speeds and typical worst case per-uni...
Figure 2.26 Vertical pump lineshaft rotor behavior example.
Figure 2.27 Example of how vibration of equipment depends upon interplay bet...
Figure 2.28 Example of force vs. displacement phase angle.
Figure 2.29 Bode and Nyquist Plots.
Figure 2.30 Example of data acquisition locations for ODS test on vertical p...
Chapter 3
Figure 3.1 The barrel-type, centrifugal gas compressor shown here is a typic...
Figure 3.2 A vertical (x) and horizontal (y) probe, oriented 90 degrees apar...
Figure 3.3 Proximity probe calibration curve.
Figure 3.4 A centrifugal barrel compressor like the one shown here is an exa...
Chapter 4
Figure 4.1 Ascend
™
chart.
Figure 4.2 Example of optimum reference state on two identical centrifugal p...
Figure 4.3 40 Ascend
™
factors.
Figure 4.4 Three levels of ascend
™
.
Figure 4.5 Circles represent asperity contact during sliding conditions.
Figure 4.6 Sliding and frictional heat.
Figure 4.7 Holistic approach steps.
Figure 4.8 Machine Criticality Factor (MCF) (Relates to the consequences of ...
Figure 4.9 Sample locations for splash/bath lubricated machines.
Figure 4.10 Graphs in an oil analysis report can help illustrate notable tre...
Figure 4.11 Moisture trend approaching a level limit.
Figure 4.12 World population growth.
Figure 4.13 Condition monitoring and time domains of machine failure.
Figure 4.14 Failure detectability technique and inspection periodicity influ...
Figure 4.15 Zone inspections for early problem detection.
Figure 4.16 Modern bottom sediment and water (BS&W) Bowl Sight Glass.
Chapter 5
Figure 5.1 Infrared temperature gun.
Figure 5.2 Typical temperature trend.
Figure 5.3 Tilting pad bearing.
Figure 5.4 Recommended location for temperature sensors in titling pad thrus...
Figure 5.5 Air fin cooler, which is located on the far right of the skid, pr...
Figure 5.6 Schematic of a two-stage reciprocating compressor with an interco...
Figure 5.7 Reciprocating compressor performance can be approximated using th...
Figure 5.8 Pressure versus stroke diagram for reciprocating compressor.
Figure 5.9 Centrifugal compressor performance can be approximated using the ...
Figure 5.10 Reciprocating compressor.
Figure 5.11 How discharge pressure affects compressor’s discharge temperatur...
Figure 5.12 Typical reciprocating compressor temperature measurement. Note: ...
Figure 5.13 Hypothetical compressor valve temperatures.
Chapter 6
Figure 6.1 Six throw reciprocating gas compressor coupled directly to 8000 H...
Figure 6.2 Reciprocating compressor cylinder cross section.
Figure 6.3 Reciprocating gas compressor.
Figure 6.4 Typical pressure volume plot.
Figure 6.5 Comparison of healthy crank-end (CE) valve and leaking CE valve....
Figure 6.6 Multiple ultrasonic sensor outputs for multiple engine analysis l...
Figure 6.7 Reciprocating compressor cylinder.
Figure 6.8 Typical air-cooled, skid mounted natural gas reciprocating compre...
Figure 6.9 Four throw gas compressors (left) driven by natural gas engine (r...
Chapter 7
Figure 7.1 Regularly monitoring machinery condition is a vital part of any m...
Chapter 8
Figure 8.1 Operators must remain vigilant around reciprocating compressors a...
Figure 8.2 If fundamental (1x) or harmonics (2x, 3x, etc.) pulsation frequen...
Figure 8.3 (a) Pipe clamp with liner material on clamp ID and pipe wedges. (...
Figure 8.4 This valve represents an unsupported concentrated mass, so is sho...
Figure 8.5 The failure surface on this bolt is indicative of fatigue due to ...
Figure 8.6 Some typical small-bore piping designs that can result in excessi...
Figure 8.7 This chart defines when a piping branch can be considered small-b...
Figure 8.8 Ways that flanged and welded cantilevered valves can be supported...
Figure 8.9 Pipe clamp with integral spacers using cap screws.
Figure 8.10 Keys to ideal pipe clamp installation.
Figure 8.11 A properly installed pipe clamp bolted to a concrete pier. Notic...
Figure 8.12 Correctly installed pipe clamps on concrete footing.
Figure 8.13 An incorrectly installed pipe clamp. Notice that with the clamp ...
Figure 8.14 There is insufficient clamping force on this clamp due to the lo...
Figure 8.15 A vibration spectrum is a mathematical process where a time wave...
Figure 8.16 Mag-mounted tri-axial accelerometer on a pipe.
Figure 8.17 Mag-mounted tri-axial accelerometer on a valve.
Figure 8.18 Waterfall display of piping vibration.
Figure 8.19 Piping assessment chart.
Chapter 9
Figure 9.1 Multistage centrifugal gas compressor installed in processing fac...
Chapter 10
Figure 10.1 Troubleshooters must understand the operating characters of all ...
Figure 10.2 A process machine’s performance cannot be understood without und...
Figure 10.3 Knowing process machine construction details provides insight in...
Figure 10.4 A reciprocating compressor cylinder’s compression ratio (r) cont...
Figure 10.5 A centrifugal compressor performance map, like the one seen here...
Figure 10.6 A hypothetical piping diagram two centrifugal pumps installed in...
Chapter 11
Figure 11.1 Schematic of torsional vibration model depicting the electric mo...
Figure 11.2 Photo of disc pack coupling (the electric motor is on the left a...
Figure 11.3 An internal flywheel was added to the back end of the compressor...
Figure 11.4 Typical disc pack damage.
Figure 11.5 Typical coupling bolt damage.
Figure 11.6 Series of torsional strain spectrums at different speeds recorde...
Chapter 12
Figures 12.1a and 12.1b Image “a” shows how signals with different frequenci...
Figure 12.2 In a zoom configuration, signals with similar frequencies will a...
Figure 12.3 The two shaft gas turbine mentioned in this case study is seen h...
Figure 12.4 Cross section of similar two-shaft gas turbine.
Figure 12.5 Zoom analysis results from PT speed sweep.
Chapter 13
Figure 13.1 Process designers know that there are always tradeoffs between p...
Figure 13.2 This image depicts the three types of beta (β) Weibull distribut...
Figure 13.3 Typical twin pump installation.
Figure 13.4 Simple raptor block diagram with 3 parallel elements.
Figure 13.5 Inputs for example 1.
Figure 13.6 Raptor results from running Example 1.
Figure 13.7 Block diagram of main and spare compressor installation.
Figure 13.8 Raptor results from running Example 2.
Figure 13.9 Block diagram of three compressors in parallel.2 out of the 3 ...
Figure 13.10 Raptor results from running Example 3.
Figure 13.11 Example of less reliable compressors operating in parallel.
Figure 13.12 Raptor results from running Example 4.
Figure 13.13 Raptor results from examples 1 and 2.
Chapter 14
Figure 14.1 This is a schematic of a two-shaft gas turbine (on the left) dri...
Figure 14.2 Single shaft gas turbine cross section.Notice that the gas pro...
Figure 14.3 Cross section of two shaft gas turbine.Notice that the gas pro...
Figure 14.4 Schematic of two shaft gas turbine.HP is the high pressure exp...
Figure 14.5 Gas turbine view showing the inlet air volute on the left, air c...
Figure 14.6 On the far left is a typical gas turbine configuration. In the m...
Figure 14.7 Inside the air compressor, air moves through a series of station...
Figure 14.8 Close-up of axial compressor blades which rotate between sets of...
Figure 14.9 Gas turbine combustor.
Figure 14.10 Gas turbine transition piece.
Figure 14.11 Single stage gas turbine.
Figure 14.12 Gas turbine firing temperature trend.
Figure 14.13 Cross section of hot section of gas turbine.Flow arrows (blue...
Figure 14.14 Gas producer blades and power turbine blades in two shaft gas t...
Figure 14.15 Power turbine wheel.
Figure 14.16 Locations listed in Table 14.1 are defined in this image.
Figure 14.17 How temperature and pressure change inside a gas turbine. The l...
Figure 14.18 Gas turbine control variables.
Figure 14.19 High quality air filtration system for a gas turbine.
Figure 14.20 Hot corrosion on first stage power turbine nozzle.
Figure 14.21 Combustion inspections are required to inspect combustion liner...
Figure 14.22 Some common inspection findings during a major inspection. (a) ...
Figure 14.23 Industrial gas turbine in the field.
Chapter 15
Figure 15.1 Typical integrally geared, instrument air compressor.
Figure 15.2 Major rotating components in an integrally geared compressor.
Figure 15.3 Schematic of an integrally geared air compression system.
Figure 15.4 Signs of corrosion in the compressor inlet.
Figure 15.5 Signs of impeller damage from liquids and solids.
Figure 15.6 Rub and seizure: HS shaft impeller with part of broken shaft ins...
Figure 15.7 The
top image
shows the configuration of the high speed pinion a...
Figure 15.8 Auto drain trap DM-2500B electric actuator SS ball valve type.
Figure 15.9 Pinion damage due to poor lubrication bearing.
Chapter 16
Figure 16.1 Centrifugal gas blower in a CCR reformer.
Figure 16.2 Modified bearings by OEM Year 2007 using new cylindrical roller ...
Figure 16.3 Lubricant oil viscosity selection chart for NTN bearings.
Figure 16.4 A typical cross sectional drawing of a flush-mounted, multiple c...
Chapter 17
Figure 17.1 Due to their simplicity and reliability, motor-driven centrifuga...
Figure 17.2 Friction only system curve superimposed on series of centrifugal...
Figure 17.3 Centrifugal pump moving liquid in system with static elevation h...
Figure 17.4 Superposition of systems curve and centrifugal pump speed curves...
Chapter 18
Figure 18.1 Single stage reciprocating compressor.
Figure 18.2 Typical pressure-volume diagram for reciprocating compressor.
Chapter 19
Figure 19.1 A reliability technician uses an infrared camera to inspect an e...
Chapter 20
Figure 20.1 We can learn a lot by simply walking around and observing the pl...
Figure 20.2 Keep an eye on your equipment.
Figure 20.3 Look for teaching opportunities.
Chapter 21
Figure 21.1 Rotating machines, similar to those seen here, are highly engine...
Guide
Cover Page
Series Page
Title Page
Copyright Page
Dedication
Preface
Acknowledgements
Table of Contents
Begin Reading
About the Editor
About the Contributors
Index
Also of Interest
WILEY END USER LICENSE AGREEMENT
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Rotating Machinery Fundamentals and Advances
Scope: Rotating machinery represents a broad category of equipment, which includes pumps, compressors, fans, gas turbines, electric motors, internal combustion engines, etc., that are critical to the efficient operation of process facilities around the world. The objective of the “Advances in Rotating Machinery Series” book series is to provide industry practitioners a time-saving means of learning about the most up-to-date rotating machinery ideas and best practices. To meet this intent, this series covers industry-relevant topics, such as design assessments, modeling, reliability improvements, maintenance methods and best practices, reliability audits, data collection, data analysis, condition monitoring, and more.
About the Series Editor:
Robert Perez is a mechanical engineer with more than 40 years of rotating equipment experience in the petrochemical industry. He has worked in petroleum refineries, chemical facilities, and gas processing plants. He earned a BSME degree from Texas A&M University at College Station, an MSME degree from the University of Texas at Austin and holds a Texas PE license. Mr. Perez has written numerous technical articles for magazines and conference proceedings and has authored 5 books and coauthored 4 books covering machinery reliability. He is also the technical editor of Kane’s Rotating Machinery Dictionary.
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Condition Monitoring, Troubleshooting and Reliability in Rotating Machinery
Volume 3
Edited by
Robert X. Perez
This edition first published 2023 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2023 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
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For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Limit of Liability/Disclaimer of WarrantyWhile the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchant-ability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials, or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read.
Library of Congress Cataloging-in-Publication Data
ISBN 9781119631545
Cover images: Left to rightNatural gas compressor station, GTS Productions I Shutterstock.comGas turbine burner, Red_Shadow I Shutterstock.comTech using thermal imaging camera, Joyseulay ILubricant and Gears, Andrey VP I Shutterstock.comCover design by Kris Hackerott
Dedication
This book series is dedicated to rotating machinery professionals around the globe who have devoted their careers to repairing, evaluating, and optimizing their equipment. It is through their diligence that critical machines are able to operate safely, efficiently, and reliably between scheduled outages.
Preface
“Good reliability engineering is not the search for perfection—rather, it is the search for pragmatic solutions to business problems.”
H. Paul Barringer, Reliability Consultant
Rotating machinery represents a broad category of equipment, which includes pumps, compressors, fans, gas turbines, electric motors, internal combustion engines, etc., that is critical to the efficient operation of process facilities around the world. These machines must be designed to move gases and liquids safely, reliably, and in an environmentally friendly manner. To fully understand rotating machinery, owners must be familiar with their associated technologies, such as: machine design, lubrication, fluid dynamics, thermodynamics, rotordynamics, vibration analysis, condition monitoring, maintenance practices, reliability theory, etc.
The goal of the three volumes of the “Advances in Rotating Machinery Book Series” is to provide industry practicioners a time-savings means of learning about the most up-to-date rotating machinery ideas and best practices. This three-book series will cover industry-relevant topics, such as design assessments, modeling, reliability improvements, maintenance methods and best practices, reliability audits, data collection, data analysis, condition monitoring, and more.
In my 40 year career in the industry, I have trained myself to keep H. Paul Barringer’s quote (shown above) in mind when dealing with real-world machinery issues. I approach every reliabililty problem as a business problem. I begin by asking: What is the cost of the problem? Then, I ask: What are the possible practical solutions to the problem? Hopefully, we can find a solution that is both effective and economically justified, but this is not always the case. This book series’ mission is to offer proven, cost effective solutions and best practices that can help users manage their machinery problems.
Volume 1 begins the series by focusing on machinery design and analysis. Volume 2 in the series covers machinery reliablity concepts and practical machinery reliability improvement ideas. Volume 3 continues the series by covering:
Machinery monitoring concepts and best practices
Lubrication best practices
Machinery troubleshooting
Reliability improvement ideas
Professional development advice
Readers will find a good mix of theory and sage experience throughout this book series. My hope is that practicioners of machinery reliabilty technologies will use the wisdom contrained in this book series to achieve best in class reliablity performance at their facilities.
Robert X. Perez, EditorSummer 2022
Acknowledgements
I would like to thank all the contributors for their expert advice and their clear and insightful prose. Without them, this book series would not have been possible. I would also like to thank the publisher for believing in me and allowing me to develop this comprehensive book series. Finally, I would like to thank my wife for reviewing my drafts and for her encouragement.
Part 1CONDITION MONITORING
1An Introduction to Machinery Monitoring
By Robert X. Perez
The aim of employing predictive maintenance technologies in process facilities is to assess the condition of equipment by performing periodic inspections such as vibration analysis, temperature monitoring, oil analysis, ultrasonic analysis, etc. or by using permanently installed equipment, such as vibration or temperature sensors. The primary tenant of the predictive maintenance philosophy is that it is more cost-effective to perform maintenance when degradation or distress is detected than to risk running equipment until it loses performance capability and adversely affects the process (Figure 1.1). Operating personnel hope to identify and address machinery issues in the primary state before costly secondary damage is experienced.
Figure 1.1 As a machine begins to fail, it begins showing signs of distress. First, vibration levels increase and then noise is detected. In the final stages of failure, heat and smoke are experienced before a catastrophic failure occurs. It makes economic sense to invest in condition monitoring technology that can detect early signs of failure before secondary damage can occur.
There are two types of data collected by condition monitoring systems: a) Dynamic data which is composed of electrical signals that rapidly change versus time, as seen in Figure 1.2. Dynamic data requires some type of signal processing to convert it into a user-friendly format. b) Static data which are signals that do not change rapidly versus time, therefore signal processing is not required. The most common condition indicators used for monitoring machines and piping in critical processes are:
Vibration
—This is dynamic data is collected by measuring the motion of a vibrating surface, such as a bearing housing or shaft. Analysis of this type of data requires complex signal processing and pattern recognition. More on vibration analysis later. (RTD’s) are often inserted into a fluid stream or on or below bearing metal surfaces to measure temperature. Portable infrared temperature guns and contact thermometers can also be used to monitor machine surface temperatures. In some applications, thermography is employed to visualize temperature distributions across a machine in order to identify component issues such as failing bearings, etc. Thermography can also be used to spot electrical problems in the field on motors and control panels.
Pressure
—This can be either in the form of static or dynamic data collected by inserting a pressure traducer into a fluid stream. Trending static field pressure data can be used to spot changes in rotating machinery performance or to ensure operating conditions are normal.
Temperature
—This is usually in the form of static data. Thermocouples (TC) or resistance temperature devices
Figure 1.2 Mechanical vibration levels are commonly used to assess the condition of vital process machinery. Complex vibration waveforms measured in the field are a combination of multiple machinery phenomena such as unbalance, looseness, etc.
Oil Analysis
—Oil analysis requires that oil samples be collected in the field and then sent off-site for lab testing. Although most oil properties are usually determined by lab testing, some oil properties can be monitored in real time.
Piping, Duct Work, and Structural Vibration
—The vibration of piping, vents, duct work, and supporting structures connected to machinery can signal problems, such as critical speeds issues, resonances, and unwanted flow conditions. On new installations, excessive piping vibration may be indications of poor installation and/or design practice.
Vibration Analysis
In the simplest terms, mechanical vibration in rotating machinery is simply the back and forth movement or oscillation of machines and components, such as drive motors, driven devices (pumps, compressors, and so on), and the bearings, shafts, gears, belts, and other elements that make up mechanical systems. Vibration in industrial equipment can be both a sign and a source of trouble. With a basic understanding of vibration and its causes, the maintenance professional can quickly and reliably determine the cause and severity of most machine vibration and provide recommendations for repair.
Elements of Vibration
Machinery vibration as a repetitive movement around a point of equilibrium characterized by its variation in amplitude and frequency. Vibration can be the dynamic motion of a bearing housing or piping system or the dynamic motion of a rotor relative to a bearing or stator. Both the amplitude and the frequency are used to assess and analyze vibration issues. Amplitude is the maximum extension of the oscillation and it is measured from the lowest point to the highest point of the waveform. We can say the amplitude is the total movement of a surface or object during a cycle which is used to quantify the intensity of the vibration. Frequency measures the rate at which movements in vibration occur per second (Hz) or cycles per minute (CPM). For example, every piano note is tuned to a unique frequency. If you examined the vibration waveform of each note, they would each have a unique frequency corresponding to a defined note. The piano frequencies and amplitudes of each note are combined to create a complex signal. Similarly, vibration can be a composition of multiple frequencies that are the result of different machinery phenomena (Figure 1.2). Every machine will have its own vibration signature related to many factors such as its construction, installation, and condition. It is the job of the monitoring system to faithfully detect and display the vibration that is occurring. The vibration analyst must have complete trust in the vibration monitoring system before they can begin the vibration analysis process.
When Vibration is a Problem
Most industrial devices are engineered to operate smoothly and avoid vibration, not produce it. In these machines, vibration can indicate problems or deterioration in the equipment. If the underlying causes are not corrected, the unwanted vibration itself can cause additional damage. In critical process machinery, smoother operation is generally better and a machine running with vibration levels close to zero is ideal.
Effects of Vibration
The effects of excessive vibration can be severe. If unchecked, machine vibration will accelerate wear rates in mechanical seals, internal seals, and bearings and potentially lead to catastrophic equipment failures. High machine vibration levels usually lead to a shortened machine life and a higher probability of catastrophic failure.
Vibrating machinery will also:
Create more background noise
Create safety issues due to flammable product leaks to the atmosphere
Lead to degradation in plant working conditions due to external product and oil seal leaks
Lead to excessive power consumption due to the wear of internal seal clearances
Affect product quality by damaging seals and allowing oil, water, and other contaminates to enter the process
In the worst cases, vibration can damage equipment so severely that it will fail rapidly and potentially halt plant production. Yet, there is a positive aspect to machine vibration. Measured and analyzed correctly, vibration can be used in a preventive maintenance program as an indicator of machine condition and help guide the plant maintenance professional to take remedial action before disaster strikes.
Monitoring Systems
Predictive maintenance programs rely on either portable or permanently installed monitoring systems that can accurately sense and report one or more key equipment condition and performance indicators. For example, vibration monitoring systems, which are commonly used to assess the mechanical condition of process machinery, have several distinct components (Figure 1.3) that work together to deliver a useful output. Other examples of monitoring systems are those that measure bearing temperature by using embedded resistance temperature detectors (RTDs) or thermocouples (TC) with outputs that are connected to temperature monitors. The role of a temperature monitor is to convert the input from a temperature sensor into an output voltage proportional to the temperature that can then be displayed, monitored, or stored for later use. Pressure monitoring systems employ pressure transmitters to measure vital pressures, such as suction and discharge pressures, oil and seal system pressures, and process pressures. The intent of every monitoring system is to sense physical measurements occurring in the field and display them in real time so that it can be analyzed and acted upon as required.
Vibration monitors all have some type of motion sensitive sensor that detects and transmits a motion signal, usually a current or voltage, to the signal processor. To select the proper sensor, the user must ask: What am I trying to measure? To answer this question, you need to know the expected amplitude and frequency range of the vibration phenomena. For example, Figure 1.4 shows spectral analysis bands from a machine with rolling element bearings. Notice there are various potential vibration issues identified based on experience, such as imbalance, alignment, etc. By inspection, we can see that to adequately monitor the vibration phenomena shown in Figure 1.4, we would need a sensor capable of detecting vibration in the range from 0 to 20,0000 cycles per minute (CPM). The lesson here is: The expected machinery defects expected will dictate the type of sensor used. If we look at the various sensor options listed in Table 1.1, we see that we should use velocity measurements to monitor this machine. (Velocity would be measured using an accelerometer with single integration.)
Figure 1.3 Most monitoring systems are composed of a sensor, signal processor, and a local or remote display of some kind. Critical machinery measurements can have one or more protection schemes, which contain local or remote alarms and trip settings.
Figure 1.4 This hypothetical vibration spectrum illustrates some possible frequency content. Notice that the various machine issues show up in different frequency bands.
The next element in a monitoring system is a signal processor that receives the signal and converts it to a usable output format. Signal processing can include filtering out unwanted portions of the input signal, converting the signal to a digital set of values, or calculating the average, maximum, or minimum value of a series of inputs. One key parameter of the signal processor is that it must be capable of sampling data at a higher rate than the highest frequency transmitted by the sensor. To avoid aliasing, the type of signal distortion and signal processor must be capable of sampling at more than twice the highest frequency contained in the input of the signal. The designs of signal processors are numerous and varied in purpose. In the end, you want the output of the signal processor to be free of processing errors and in a usable format that that can be displayed and/or used in a protection scheme.
Signal processors are designed to handle both static and dynamic signals. An example of a static signal is temperature. If you plot a temperature over time, you typically get a gradually changing series of points that can visually be studied and analyzed. Static signals, such as temperature and pressure signals, do not carry any rapidly changing, i.e., dynamic, components. On the other hand, dynamic signals can vary rapidly with time, as seen in Figure 1.5. Dynamic signals, also called dynamic waveforms, require more complex signal processing to determine their properties. Typical waveform properties are frequency, peak amplitude, root mean square amplitude, and phase. In some cases, both static and dynamic information are extracted from the raw sensor data.
Table 1.1 Summary of frequency capabilities of various sensors.
Frequency Range
1
0-10 Hz
10 to 1000 Hz
1000+ Hz
Measurement ofType
Displacement (accelerometer with double integration)
Detection of common mechanical defects in low speed machines
Displacement (accelerometer with double integration)
Piping vibration analysis
2
Displacement (proximity probes measuring relative motion between bearing and shaft)
Detection of common mechanical defects in high speed machines with fluid film bearings
Velocity (accelerometer with single integration)
Detection of common mechanical defects in 1800 to 3600 rpm machines
Velocity (accelerometer with single integration)
Piping vibration analysis
2
Accelerometer (case mounted)
Detection of high frequency phenomena, i.e., Impacts, rolling element bearing defects, gear defects
1) Notice that an accelerometer with single integration can be used to detect most common mechanical defects in the 1800 to 3600 rpm machines. 2) Proximity probes are used to detect common mechanical defects in high speed machines with fluid film bearings.
A spectrum analyzer can deconstruct a complex input waveform (A) into its fundamental sine waves (B1, B2, B3). These constitute that sine waves provide insight into the mechanical condition of a machine being analyzed.
Most in-depth analysis of machinery vibration is done in the frequency domain or using spectrum analysis. Spectral analysis is the process of transforming a signal from the time domain to the frequency domain (see Figure 1.6). It is often done using a spectrum analyzer. The signal is analyzed to determine any substantial frequencies coming from the machine’s components. Where there is a peak in frequency signal, that is the likely source of vibration. Common applications for spectral analysis include the rotational speed of a shaft or how often tooth meshing occurs on a pair of gear wheels.
Care must be taken to ensure all vibration measurement locations provide a true indication of bearing vibration. On larger machines, horizontal and vertical bearing housing vibration data collection is recommended (Figure 1.7). A comparison of horizontal and vertical vibration levels can be used to identify machine specific problems related to support stiffness, bearing loading, bearing fits, etc.
Figure 1.5 Complex dynamic waveform decomposed into sine wave components.
Figure 1.6 Here is a hypothetical vibration spectrum for an electric motor, gearbox, and compressor machine train. By transforming vibration signals from the time domain into the frequency domain, characteristic machinery phenomena can be identified. Notice that the spectrum here contains several discrete frequency components. Every machine has a set of unique spectrums or signatures that are based on their construction and operating conditions.
Figure 1.7 It is recommended that both horizontal and vertical vibration data be collected on critical machines.
DCS Systems
It is common that critical field machine parameters such as overall vibration levels, bearing temperatures, field pressures, and flows are relayed to a control room for real-time monitoring and display (see Figure 1.8). If properly conceived and installed, key machinery data is displayed in ways that is easy to observe and interpret. Displays can use dials, scales, simple numerical displays, or other visual interfaces to communicate the status of variables being measured. Today, most plants have DCS, or distributed control systems, that allow field vibration and temperature information to be easily transmitted from the field to a centralized computer for monitoring. Most DCS systems also have storage capabilities that provide a means of trending and comparing the present status with the past, which is a must in critical machinery applications.
Figure 1.8 Control room operators depend on a distributive control system to provide them with vital real-time process information in a visual format.
Data Presentation
Figure 1.9 illustrates two trend plot examples. One plot is that of a gradually increasing value, whereas the other shows a step change in a measured value. Trend plots are useful because they provide visual representations of the measured parameter over time and this representation can help in the troubleshooting process. Suppose a step change occurred at the same time as a change in the process, there may be a correlation between the two events that should be investigated. A gradually increasing trend plot may indicate either a deteriorating internal or external component.
Critical monitoring systems may also have built-in protection schemes, which can be configured to serve the unique needs of specific machine trains. These systems can provide either remote or local alarms whenever an undesirable condition has been detected. However, it is recommended that all safety critical trip points, such as machine speed, be handled with independent, dedicated instrument loops to ensure their reliability. To ensure reliable machinery monitoring systems, they must be regularly calibrated and maintained to ensure all monitoring points are working properly.
Figure 1.9 Examples of trend plots.
Finally, for a monitoring program to be complete, assessment criteria are required to determine when the machine owner should be concerned or if action must be taken immediately. Without assessment criteria, there would be no need for monitoring systems because their outputs would be meaningless. If assessment criteria are set too low, then time and money are wasted. However, if assessment criteria are set too high to avoid nuisance alarms or trips, then human, environment, and equipment health may be placed in jeopardy.
2Centrifugal Pump Monitoring, Troubleshooting and Diagnosis Using Vibration Technologies
By William D. Marscher
Introduction
This chapter outlines the current and developing practice of condition monitoring and diagnostic troubleshooting for centrifugal pumps and their systems through application of vibration-related technologies. Key concepts and methods will be described in understandable terms. Modern vibration-based data acquisition and data analysis options are presented, along with physics-based pump condition evaluation strategies. There will be discussion concerning the reasoning behind international guidelines and standard available from HI, ISO, and API and their vibration acceptance requirements.
Circustances for which test results should be augmented by rotordynamics analysis or structural finite element analysis will be discussed in the context of what information these analyses can provide to an End User or OEM that could be informative to reliable and trouble-free operation. Mechanical reliability problems typically involve either tribology (friction and wear) or metal fatigue (crack formation and possible fracture). The likelihood and severity of these tribological and fatigue problems will be considered in terms of physical phenomena and forces associated with them, so that by applying techniques to detect these phenomena and their forces the problems they may cause can be avoided or at least delayed.
The most common sources of force that may result in excess vibration include the rotor being out of balance, the presence of excessive misalignment between the pump and its driver and excessive hydraulic off-design-flow forces such as those from inlet recirculation, stall, or surge. Other common vibration-causing hydraulic forces that may be excessive include the stator vane or impeller blade pass pressure pulsations that are present at some level at all flow rates.
When forces such as these become large, vibration will increase more or less in proportion to any force increase until running clearances are used up. Once radial clearance is gone, vibration will increase at some frequencies such as integer harmonics of 1x and maybe 1/2x, but ironically may sometimes instead actually decrease at 1x rpm, because the vibrating rotor is jammed against the much stiffer and massive casing. Like many vibration-related phenomena, this situation can be very confusing unless a systematic investigation is followed. The best troubleshooting methods will include as much key information as possible, rather than focusing on only one type of data. This chapter will discuss how x is typically the most important vibration component but should be evaluated in the context of other frequencies, as well as process information, bearing temperature, and (if available) oil monitoring analysis information.
Like many other aspects of rotating machinery, evaluating vibration is often about perceiving “wheels within wheels”, in that the end result may not be from a single cause but rather a combination of several factors. One example is the amplifying phenomenon known as resonance, which can result in high vibration even if exciting forces are reasonably low. This is due to motion being magnified by the presence of a rotor or structural natural frequency, which occurs when a machine operates at a “critical speed”, as will be explained later. Another example is subsynchronous vibration due to rotordynamic instability, in response to which the rotor vibration becomes unbounded, with radial motion limited only by rubbing at the clearances. If circumstances are right, such unstably high vibration can occur even if the rotor had been nearly perfectly balanced and aligned. To understand what can lead to phenomena such as resonance and instability, as well as unexpectedly high excitation forces, it is important to be familiar with key vibration concepts, as presented below. In support of this, the instrumentation and data analysis options to best monitor and evaluate vibration will be presented.
Vibration Definitions
The reader may be familiar with vibration concepts and term definitions from other references, but for convenience some of the most important issues are defined or illustrated below:
The foundational concept of vibration is oscillating motion, such that there is at least one complete back-and-forth cycle of a mass supported relative to another mass (or to a reacting “ground”, such as a foundation) by a flexible element, typically behaving like some form of spring. If energy is not removed from the oscillation, typically by some form of “damping” (like an automobile shock absorber), then the vibration oscillation “wave-form” (motion in space over a single oscillation period of time) becomes a forever repeating “cycle”, vibrating without end. A typical waveform over the “period” of one cycle is shown in Figure 2.1, along with several measure numbers for vibration waveform amplitude.
Key terminology concerning the vibration waveform or cycle is as follows:
Vibration: The oscillation of an object about its position of rest
Cycle: Movement of a mass through all its positions back to its point of rest, on an oscillatory basis
Period: The time it takes for one cycle to complete
Frequency: Number of cycles in a given amount of time (e.g., 1 cycle/s, known as a “Hertz”, Hz), which is also the inverse of the vibration’s period
CPM: Number of cycles in one minute
CPS: Number of cycles in one second (Hz)
RMS: Root Mean Square, which is the square root of vibration level squared, summed over calculations step-by-step throughout a selected time interval, covering one or more complete cycles
Figure 2.1 Cyclic nature of vibration considered as waveform.
Courtesy Mechanical Solutions, Inc.
Fourier Transform: the mathematical relationship between an overall waveform and the component waveforms at differing frequencies that add together to form the overall waveform
FFT: Fast Fourier Transform, a computer method to quickly determine a vibration vs. frequency “spectrum” from a vibration vs. time waveform however complicated it may be
How Vibration vs. Time Relates to a Vibration vs. Frequency “Spectrum”
The relationship between vibration is considered as a function of time versus vibration which is considered as a function of frequency, is illustrated in Figure 2.2. The figure shows how each approach is presenting the same actual total vibration. If the vibration is plotted only in the time domain, the waveform can become quite complicated, as seen in the upper right figure. However, as shown in the left view of the left figure, when considered one frequency at a time, the vibration breaks into simple sine waves of different frequencies and amplitudes. Seen in the right view of the left figure, the amplitudes are straight vertical lines, each line being of a given height (the amplitude) at a given frequency, with frequency increasing left to right. This is called a frequency spectrum. The math that relates the left view with the right view for Figure 2.2 is what is known as the Fourier Transform, with its calculations simplified by the so-called Fast Fourier Transform, FFT, as performed by modern vibration signal analyzers.
The following are some considerations about whether it is best to display vibration in the “time domain” or the “frequency domain”:
Using the frequency domain, specific defects show up as peaks at discrete frequencies, which gives important clues concerning what is causing the vibration
Small (but maybe important for diagnostics!) repetitive signals typically are not hidden in the frequency domain, even among stronger signals at other frequencies
The time domain is ideal for observing and quantifying a one-time event (a “transient”) or an impulsive excitation, which can occur during cavitation Some structural vibration may also be caused directly by fluid pressure pulsations or “acoustics”
Figure 2.2 How vibration vs. Time can relate to vibration vs. frequency.
Courtesy Mechanical Solutions, Inc.
What are Reasons for Excess Vibration?
A wise man once said, “If a pump is not vibrating, it’s not running!” Any operating machine produces some degree of waste energy and this waste energy shows up primarily as vibration, noise, and heat. So, the issue is not whether or not the presence of vibration is acceptable, but rather how much is acceptable. More will be discussed about how to determine this when we discuss vibration standards below.
In preparing to evaluate vibration, it is useful to consider the physical reasons why some of a machine’s energy ends up as vibration. An outline of the process of how a pump’s operation will lead to some level of vibration is as follows:
Forces internal to the pump due to the process of pressurizing and moving fluid react against the pump rotor and together with imbalance forces (no rotor is perfectly balanced) and misalignment forces (no pump and driver are perfectly aligned), cause motion (“response”) of the rotor.
The force leads the response in time
There is a phase lag (timing delay) between force and response
The rotor response is an oscillating motion that we call vibration (called “rotordynamics”, for a rotor) that causes the rotor to react against the pump casing through its bearings and bearing housings to transfer some of the vibration from the rotor (such that it now becomes “structural vibration”).
The vibration of either the rotor or the stationary structure may be amplified by a natural frequency “resonance”, in which the natural unforced oscillation of the vibrating component (like a guitar string after it is plucked) is at or near to the forcing frequency
Based on what potential damage issue is being evaluated, the vibration may be considered in terms of the direct motion (“Displacement”), the motion’s rate of change during an oscillation cycle (“Velocity”), or the rate of change of the velocity (“Acceleration”). Displacement emphasizes lower frequency components of vibration, acceleration emphasizes high frequency components, and velocity is in the middle. Most vibration standards are in terms of, or at least emphasize, velocity.
If either the rotor or structural vibrations, and thereby their differential, are excessive, then rubbing or fatigue damage can occur. The most important factor in rubbing is rotor vs. bearing housing or seal interface and relative displacement.
Relationship of Vibration to Centrifugal Pump Acceptability and Reliability
Pumping machinery vibration provides diagnostic information, particularly relevant for the bearing and seal failure problems that vibration or excessive displacement may cause. These and other problems typically associated with vibration are responsible for a significant amount of the maintenance budget and lost-opportunity cost at many refineries, chemical plants, electric utilities, water/wastewater plants, and other facilities where industrial pumps are used. Applying effective vibration-based condition monitoring and troubleshooting methods therefore makes not just technical, but also financial sense. This chapter will leverage industry standards such as ISO 10816-7 (ISO, 2009), API-610 (API, 2021), and API-684 (API, 2010) and the combined HI 9.6.4 (HI/ANSI 2017), 9.6.5 (HI/ANSI 2017), and 9.6.8 (HI/ANSI 2019), so that the reliability-conscious End User or his consultant can use them as a guide, and at least a starting-point in setting up a condition monitoring program and its criteria for alarm and trip. It will be emphasized that when specific vibration values are compared to the values in the industry standards, this must be in the context of where a centrifugal pump is operating on its head versus capacity curve, as well as its speed. Lowest vibration will occur during operation close to the Best Efficiency Point “BEP” for any given speed. In addition to this, as already mentioned, it is also very important to determine how close the rotor critical speeds and rotor-support structural natural frequencies are to running speed or other strong forcing frequencies, such as not only 1x running speed, but also (often but with lesser effect) 2x running speed and vane or blade passing frequency. The vibration levels allowed should also account for machine maximum power level, relative stiffness of the machine mounting, and how much radial clearance is available within bearings and annular seals or the thrust balance device, as will be discussed in some detail. In certain circumstances (such as vertical pump “reed” frequency vibration discussed later), height of the measurement location above the foundation is also a factor, such that higher vibration levels may be permitted at locations farther above the foundation, as discussed in ISO 10816-7.
Vibration Standards, Informal and Formal: Intent and Basis
The fundamental basis for international vibration standards is that experience and intuition each indicate that increased vibration is likely associated with diminished life of a pump. This principle has two complementary aspects to it. The first aspect is that more vibration implies higher hydraulic and/or mechanical (e.g. imbalance) forces within the pump. A large portion of these forces must be reacted through bearings, which can only tolerate limited load, and the forces also lead to relative motion of the rotor versus the casing, thereby utilizing radial clearances (e.g. at wear ring seals, mechanical seals, and balance drums), resulting in likely increase in rubbing wear and therefore loss of some portion of the pump’s remaining useful life.
