Gene Vogel
EASA Pump & Vibration Specialist

A customer specifies that the rotor is to be balanced to 4W/N. Is that the 4W/N Military specification, or the 4W/N API specification?It could make a big difference. And, how do they compare to the ISO 1940/1 specification (G2.5, G1, etc.)? Fortunately, for symmetrical rotors, comparing the various standards is only a matter of a bit of easy algebra. For non-symmetrical rotors, the process gets a little more difficult because each of the specifications handles these cases differently. The other good news is that there are on-line references that provide graphic and tabulated comparisons.

Gene Vogel
EASA Pump & Vibration Specialist

La especificación ISO para balancear rotores rígidos (ISO 1940-1) fue innovadora cuando fue introducida hace varias décadas. Esta norma estableció los Grados de Calidad de Balanceo basada en la velocidad teórica que el centro de masa de un rotor se encontraría en espacio libre, girando a la velocidad de funcionamiento normal del rotor. Esta es terminología técnica difícil de expresar, pero un entendimiento práctico de la naturaleza de las fuerzas de desbalanceo es importante para aplicar las tolerancias de balanceo en rotores de diversas máquinas. Esto también ayuda a entender el impacto de los cambios fundamentales en la reciente norma de reemplazo: 21940-11: 2016.

Primero, vamos a clarificar la diferencia entre desbalanceo y vibración. Si una máquina tenía cierta cantidad de desbalanceo y fue asentada sin restricciones sobre un acolchado suave (una almohadilla de caucho), existirá cierta cantidad de vibración a 1x rpm. Atornille esa misma máquina a una fundación maciza y la vibración a 1x rpm será mucho menor. Así que no hay conversión directa de desbalanceo a vibración y viceversa.

Por consiguiente, para maquinaria en funcionamiento, las unidades de amplitud de vibración comunes de desplazamiento y velocidad no son medidas directas del desbalanceo, La cantidad de desbalanceo del rotor se puede describir como una cantidad de masa (peso) en un radio determinado.

El artículo continúa cubriendo:

• Unidades de desequilibrio
• Dos posibles aproximaciones para el uso de planos de cojinetes para evaluar la tolerancia de equilibrio
• Desplazamiento del centro de gravedad

Gene Vogel
EASA Pump & Vibration Specialist

The ISO balancing specification for rigid rotors (ISO 1940-1) was innovative when it was introduced decades ago. It established Balance Quality Grades based on the theoretical velocity the mass center of gravity of a rotor would encounter in free space, spinning at the rotor’s normal operating speed. That’s a mouthful of technical jargon, but a practical understanding of the nature of unbalance forces is important in applying balance tolerances to various machine rotors. It is also helpful in understanding the impact of fundamental changes in the recent replacement standard, 21940-11: 2016.

First, let’s clear up the difference between unbalance and vibration. If a machine had a certain amount of unbalance and was sitting unrestrained on a soft pad (a durometer pad), there would be a certain amount of vibration at 1x rpm. Bolt that same machine to a massive foundation and the vibration at 1x rpm would be much less. So there is no direct conversion from unbalance to vibration or vice versa.

Consequently, the common vibration amplitude units of displacement and velocity are not direct measures of unbalance for operating machinery. The amount of rotor unbalance can be described by an amount of mass (weight) at a certain radius.

The article goes on to cover:

• Unbalance units
• Two possible approaches to using bearing planes to evaluate balance tolerance
• Displacement of center of gravity

Gene Vogel
Especialiste de Bombas y Vibraciones

Al igual que con la mayoría de las otras máquinas reparadas comúnmente en los centros de servicio de EASA, el balanceo dinámico de los impulsores de las bombas es una cuestión importante. El desbalanceo excesivo imparte fuerzas sobre los rodamientos, reduciendo su vida útil y sometiendo los soportes de las máquinas a una energía vibratoria que deteriora las fundaciones.

Desde la perspectiva del balanceo dinámico, los rotores de las bombas difieren mucho de los de los motores eléctricos más populares. La masa del rotor de un motor eléctrico se encuentra entre los rodamientos y la longitud de los rotores exceden a sus diámetros. Muchos impulsores de las bombas se encuentran montados en voladizo y es probable que sean más angostos que sus diámetros. Los componentes angostos pueden requerir reglas especiales para asignar el desbalanceo residual permisible (según ISO 21940-11), y pueden ser necesarias técnicas especiales para un balanceo eficiente en la máquina balanceadora.

Gene Vogel
EASA Pump & Vibration Specialist

This paper covers:

• How to set a balance tolerance
• Balancing machine setup, special fixtures and choice balancing speeds
• When to use single-plane, two-plane or static-couple methods
• Is it unbalance?
• How to get the right transducer and phase measurement setup
• Safe balance weight attachment techniques
• The ABCs of calculating balance corrections

Tom Bishop, P.E.
EASA Technical Support Specialist 

This article describes machine balancing of the rotating components of motors and generators, primarily rotors and armatures. The methods described here, in general, can be applied to on-site balancing if the rotating component is accessible. The intent is to describe the methods of attaching balance weights, not determining acceptable balance level or the location and amount of correction weight. 

The advent of computerized balancing machines has made the latter steps rather straightforward. However, the challenge of how to attach a weight in such a way that it will remain secure and not negatively affect machine operation remains at times a vexing problem. 

What is the purpose of dynamic balancing a rotating part? It is to reduce unbalance and consequently to bring vibration to acceptable levels to allow for normal bearing and other component life. The acceptable levels of vibration are described in EASA Tech Note 32, “Standards For Dynamic Balancing,” thus we won’t explain them here.

Gene Vogel
EASA Pump & Vibration Specialist

As with most other machines commonly repaired in EASA service centers, dynamic balancing on pump impellers is an important concern. Excessive imbalance imparts forces on bearings, reducing their lives and subjecting machine mountings to vibratory energy that deteriorates foundations.

Pump rotors are quite different than more familiar electric motor rotors from a dynamic balance perspective. The mass of an electric motor rotor is between the bearings, and the rotors are longer than their diameters. Many pump impellers are mounted in an overhung configuration, and the impellers will likely be narrower than their diameters. Narrow components may require special rules for allocating allowable residual imbalance (per ISO 21940-11), and special balancing techniques may be needed for efficient balancing in the balancing machine.

Chuck Yung
EASA Senior Technical Support Specialist

Most service centers balance rotors routinely, with few surprises in the process. There are even technicians who balance rotors so well that the highest velocity readings on the test bed are normally under 0.01 inch/second. It is a great indication of quality when a customer swears that a motor has never run that smoothly. Most of us do not balance fans nearly as often as rotors. The fan balancing tips in this article should be helpful. We'll start with a basic explanation of balancing and then get into balancing tips for fans. Many of these are also applicable to impellers, large sheaves and other rotating parts our customers may ask us to balance.

Topics covered include:

• Balancing basics
• Differences when balancing fans
• Building a balancing mandrel
• Alternative solutions
• Other factors that affect balancing

En toda reparación mecánica, la capacidad para desmontar, reparar y volver a montar el motor de forma apropiada sin dañar innecesariamente ninguna de sus piezas es fundamental. Esto suena sencillo, sin embargo, durante el proceso de desarme se cometen demasiados errores costosos.

Si todos los motores entraran “como nuevos”, la tarea sería más simple, aunque esto no sería garantía de que el montaje del motor fuera adecuado.

Cuando un centro de servicio recibe un pago por reparar un equipo, quiere que este permanezca en funcionamiento, ya que, si el equipo falla dentro del período de garantía, deberá asumir el costo de volver a repararlo. Por lo que tiene sentido realizar la reparación correcta la primera vez.

Los procedimientos de reparación, así como los propios motores, son afectados por los cambios en la tecnología. Este libro intenta incluir las últimas tecnologías comprobadas. En muchos casos, los métodos de reparación tradicionales aún pueden ser la alternativa más práctica. Las opciones presentadas a lo largo de este libro están destinadas a ayudar a los técnicos a seleccionar el método de reparación correcto, reconociendo que la decisión final recae en el propietario del equipo.

Algunas veces los métodos de reparación pierden popularidad, no porque aparezcan métodos mejores sino debido a técnicas deficientes. Otros métodos de reparación son adecuados para algunas aplicaciones, pero no para otras. Es trabajo del reparador decidir cuál será el mejor método para cada caso.

Este libro se encuentra dividido en secciones para los componentes básicos del motor con métodos de reparación y consejos dispersos por todas partes. Donde resulte práctico, se discuten también las causas de fallo. Esto ayudará a los técnicos a seleccionar el método de reparación más apropiado para cada aplicación en particular. La información presentada se basa en publicaciones de EASA y en revistas técnicas y literatura suministrada por fabricantes de motores, proveedores y centros de servicio establecidos.

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Tabla de contenido

• Terminología del motor
• Aplicaciones del motor y encerramientos
• Procedimientos de inspección y prueba
• Consejos para desmontar motores
• Rodamientos
• Alojamientos de rodamientos, orificios de eje, sellos y ajustes
• Ejes
• Rotores
• Ensamble del motor
• Accesorios y cajas de conexiones del motor
• Dinámica del motor
• Vibración y geometría del motor
• Corrientes por el eje/rodamientos
• Consideraciones especiales para motores a prueba de explosión
• Fallos en las componentes mecánicas
• Reparaciones misceláneas

Esta obra contiene muchas sugerencias sobre el manejo apropiado de las diferentes partes de un motor para minimizar los daños durante el proceso de reparación. Sin embargo, es imposible desarrollar un listado que las incluya todas.

En cambio, el principio básico de tomarse el tiempo para usar la herramienta adecuada y por lo general el procedimiento apropiado guiará a los técnicos por el camino correcto.

Often an overhung fan is balanced in a single plane, only to find that the vibration has shifted to the outboard bearing. Attempts to use standard two-plane techniques may result in calculated correction weights that are very large and produce poor results. There are more effective ways to approach this common problem. This presentation shows a methodical approach and techniques for tackling this difficult balancing problem.

Target audience: This presentation is intended for field service balancing technicians, supervisors and managers.

Tom Bishop, P.E., and Chuck Yung
EASA Senior Technical Support Specialists

The typical service center repairs at least 300 motors per technician annually. Saving 8 minutes (0.133 hours) per job equates to: 300 x 0.133 = 40 man-hours per year—a full week of labor per employee. It is not unrealistic to expect twice that much savings, just by implementing some of these timesaving tips.

We all know that seemingly small time savings can significantly improve the bottom line. For a service center with a 12% return on investment (ROI), shaving a few minutes off each job is the equivalent of adding 2 manmonths of billing per productive employee.

For a 10-man service center, with a shop rate of $75 per hour, 20 man-months times 75 = $258,000. To add a quarter-million dollar account usually means adding personnel, sales maintenance, and risk of bad debt/warranty expense. However, steps that streamline efficiency continue to pay dividends.

Topics covered include:

• Layout and workflow
• Time killers
• Time: Is every hour on the job billable?
• Time-saving equipment
• Attitude and productivity
• Communicating effectively
• Training
• Lighting
• Calibration
• Storage/handling/procurement
• Parts storage
• Examples from real service centers

DESCRIPTION
This 94-page handbook (3.5" x 6", 9cm x 15cm) contains carefully selected materials designed to assist repair firms in their everyday work. Just as important, your customers and potential customers can use this pocket handbook as a handy reference for mechanical data for motors and driven equipment. Buy this great resource as is OR custom brand your company logo and information on the cover to turn it into a great marketing piece for your salespeople!

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TABLE OF CONTENTS

Alignment
Alignment Information
Suggested Alignment Tolerances
ANSI/ASA Alignment Quality

Balancing And Vibration
Single-Plane Versus Two-Plane Balancing
Vibration Tests
Unfiltered Housing Vibration Limits
FFT Vibration Analysis
Vibration Constants
Vibration Conversion Factors
Electric Motor Vibration Diagnostic Chart

Motor Application Forumlas
Output
Shear Stress
Speed–AC Machinery 
Affinity Laws–Centrifugal Applications

Conversion Factors, Equivalencies & Formulas
Conversion Factors
Temperature Conversion Chart
Common Fractions Of An Inch–Decimal & Metric Equivalents
Prefixes–Metric System
Formulas For Circles

Bearings
Nominal Dimensions For Radial Ball Bearings
Nominal Dimensions For Cylindrical Roller Bearings
Radial Ball Bearing Fit Tolerances
Cylindrical Roller Bearing Fit Tolerances
Lock Nuts And Lock Washers For Ball Bearings

Motor Bearing Lubrication
Lubricating Oil Viscosity Conversions
NLGI Grease Compatibility Chart
Grease Classifications
Grease Relubrication Intervals

Metals And Alloys
Properties Of Metals And Alloys
Weight Formulas For Steel
Thermal Linear Expansion

Bolts
ASTM And SAE Grade Markings For Steel Bolts And Screws
Precautions For Tightening Bolted Joints
Bolt Tightening Torque Values
Tap Drills And Clearance Drills For Machine Screws

Keys And Keyseats
NEMA Keyseat Dimensions–Foot-Mounted AC & DC Machines
IEC Shaft Extension, Key And Keyseat (Keyway) Dimensions
Square And Flat Stock Keys
Standard Keyseat Sizes
Metric Keys–Standard Sizes

Belts And Sheaves
Pulley Formulas For Calculating Diameters and Speeds
Belt Installation
Belt Tensioning
Belt Deflection Force And Elongation Ratio
Standard V-Belt Profiles And Dimensions
V-Belt Sheave Dimensions
V-Belt Sheave Dimensions For AC Motors With Rolling Bearings
Application Of V-Belt Sheave Dimensions To AC Motors With Rolling Bearings
Mounting Of Pulleys, Sheaves, Sprockets, And Gears On Motor Shafts
Minimum Pitch Diameter For Drives Other Than V-Belts

Welding, Brazing And Soldering
Recommended Copper Welding Cable Sizes
Types Of Weld Joints 
Brazing
Basic Joints For Brazing
Soldering
Melting Temperatures Of Tin-Lead-Antimony Alloys
Flux Requirements For Metals, Alloys And Coatings

Slings, Wire Rope, Shackles and eyebolts
Types Of Slings
Typical Sling Hitches
Wire Rope
Spreader Bars
Lifting Capacity
Forged Shackles
Eyebolt Strength

Common Signals For Crane

Fundamental to every good mechanical repair is the ability to disassemble, repair and reassemble the motor correctly without unnecessary damage to any of the motor parts. This sounds simple, and yet too many costly mistakes are made in this process of taking things apart. If every motor repaired was in “as new” condition, the task would be much simpler. But this would be no guarantee that the reassembly would be correct.

​There is usually an easy way and a hard way to remove and install parts. Brute force is seldom the easiest or the correct way. The old saying of “don’t force it, get a bigger hammer” is seldom the best way.

When a service center is paid to repair equipment, the service center wants it to stay in operation. If the equipment fails again—within the warranty period—the service center pays to repair it again. It makes sense to repair it correctly the first time.

In order to improve equipment, it is important to know how and where it operates. Without understanding why a motor fails, it is impossible to deliberately improve its mean time between failures.

To do this, there must be communication between the service center and the motor user. Not only does this help the repairer decide the best course of action, but it helps the user appreciate the professionalism of the service center.

Repair procedures, like motors themselves, are affected by changes in technology. This book attempts to include the latest proven technologies. Time-honored methods of repair, in many cases, may still be the most practical option. Options presented throughout this book are intended to help the technician select the appropriate repair method, recognizing that the ultimate decision rests with the equipment owner.

Repair methods sometimes fall into disfavor, not because better methods are introduced, but because of poor techniques. Other repair methods are well-suited to some applications but not to others. It is the job of the repairer to decide what is the best method for each case.

This book is divided into sections for basic motor components with repair methods and tips dispersed throughout. Where practical, reasons for failures are also discussed. These will aid the technician in selecting the most appropriate method of repair for each unique application.

The information presented draws from EASA publications, IEEE publications, technical journals and literature supplied by vendors, motor manufacturers and established service centers.

This book contains many suggestions on how to correctly handle the various parts of a motor during the repair process so as to minimize damage. However, it is impossible to develop an all-inclusive list. Instead, the basic principle of taking the time to use the correct tool and correct procedure will usually lead the technician down the right path. Always remember, if it has to be forced beyond reason, it might be that neither the proper tool or procedure is being used or something is wrong with the parts. Step back and ask “What am I overlooking?”

Table of Contents

1. Motor Nomenclature
2. Motor Applications and Enclosures
3. Test and Inspection Procedures
4. Motor Disassembly Tips
5. Bearings
6. Bearing Housing Repair, Shaft Openings, Seals and Fits
7. Shafts
8. Rotors
9. Motor Assembly
10. Motor Accessories and Terminal Boxes
11. Motor Dynamics
12. Vibration and Motor Geometry
13. Shaft/Bearing Currents
14. Special Considerations for Explosion-Proof Motors
15. Failures in Mechanical Components
16. Miscellaneous Repairs

This book is available as part of EASA's Fundamentals of Mechanical Repair seminar.

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BOOK DOWNLOAD CD-ROM BOOK & CD-ROM

Eugene Vogel
EASA Pump & Vibration Specialist

On occasion, service centers are asked to balance fan blades that are designed for an overhung mounting. The fan blade may be received mounted on the shaft, or without any shaft. The decision has to be made about how to mount the rotor in the balancing machine. One solution is to fabricate a mandrel to balance the fan blade between the machine pedestals. The other alternative is to mount the fan blade on the end of the shaft in an overhung configuration, with the fan blade outboard of both balancing machine pedestals. This would be the more expedient method if the fan blade is already mounted on the shaft in the overhung configuration.

As long as the fit of the fan blade to the shaft doesn’t change (when using a mandrel), it can be mounted in either configuration for balancing without affecting the results. If the fan blade is balanced in one configuration, it is balanced for the other. 

How the fan blade is mounted doesn’t change the balance, as long as the fit to the shaft doesn’t change. So the question is, “Which is easiest?” Often it is easiest to mount the rotor in the overhung configuration, but balancing in that configuration presents some challenges. Those challenges are addressed here.

Las versiones impresas y en forma de descarga del valioso manual didáctico / recurso de EASA, “Principios de Motores C.A. Medianos y Grandes”, se encuentran ahora disponibles en inglés y en español. El manual incluye gráficos e ilustraciones, fotografías y mucha información técnica sobre máquinas C.A., incluyendo como funcionan, información específica sobre los tipos de encerramientos, fabricación de componentes y aplicaciones.  Muchos de los principios incluidos en el libro aplican a todos los motores C.A., especialmente a aquellos accesorios que fueron asociados en el pasado con las máquinas más grandes (como encoders, RTDs, termostatos, calentadores de espacio, sensores de vibración, etc.).

Las versiones  forma de descarga ofrecen funciones prácticas ya que contienen toda la información que contiene el manual impreso, pero en formato PDF, fácil de usa, ya que contiene marcadores que permiten a los lectores navegar rápidamente por el documento y “saltar” a la página deseada.

Las secciones del manual incluyen:

• Terminología y Definiciones del Motor
• Tipos de Encerramientos de Motores
• Aplicaciones Típicas para Motores
• Consideraciones de Manejo y Seguridad
• Teoría Básica del Motor
• Normas para Motores
• Estatores
• Rotores de Jaula de Ardilla
• Ejes
• Lubricación y Rodamientos
• Accesorios del motor & Cajas de Conexiones
• Procedimientos de Inspección y Prueba
• Alineamiento del Motor, Vibración y Ruido
• Procedimientos de Almacenamiento
• Máquinas Sincrónicas

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This version of Principles of Medium & Large AC Motors manual is now available to address applicable IEC standards and practices. This 360-page manual was developed by industry experts in Europe along with EASA's engineering team. (The "original" version of this book based on NEMA standards remains available as a separate document.)

This manual includes drawings, photos and extensive text and documentation on AC motors, including how they work, information on enclosures, construction on components and applications. Many of the principles included apply to all AC motors, especially those with accessories that are associated with larger machines in the past (such as encoders, RTDs, thermostats, space heaters and vibration sensors).

While the manual covers horizontal and vertical squirrel-cage induction motors in the 37 to 3,700 kW (300 to 5,000 hp) range, low- and medium-voltage, most of the principles covered apply to other sizes as well. 

This valuable instructional/resource manual is available in printed and downloadable versions, and focuses primarily on IEC motors.

Sections in the manual include:
(Download the PDF below for the complete Tables of Contents)

• Motor nomenclature & definitions
• Motor enclosures
• Typical motor applications
• Safety & handling considerations
• Basic motor theory
• Motor standards
• Stators
• Squirrel cage rotors
• Shafts
• Bearings & lubrication
• Motor accessories & terminal boxes
• Test & inspection procedures
• Motor alignment, vibration & noise
• Storage procedures
• Synchronous machines

BUY A COPY FOR YOUR OFFICE

PRINTED BOOK DOWNLOADABLE PDF

This book is also available focusing on NEMA Standards — in both English and Español.

NEMA - English NEMA - Español

This valuable instructional/resource manual is available in printed, downloadable and CD-ROM versions.

For this second edition, this 320-page manual has been reorganized, updated with new information, including revised standards and published articles, and edited extensively. The manual includes drawings, photos and extensive text and documentation on AC motors, including how they work, specific information on enclosures, construction of components and applications. Many of the principles included apply to all AC motors, especially those with accessories that were associated with larger machines in the past (such as encoders, RTDs, thermostats, space heaters, vibration sensors, etc.).

While the manual covers horizontal and vertical squirrel-cage induction motors in the 300 to 5,000 horsepower range, low- and medium-voltage, most of the principles covered apply to other sizes as well.

This manual focuses primarily on NEMA motors.

Sections in the manual include:

• Motor nomenclature & definitions
• Motor enclosures
• Typical motor applications
• Safety & handling considerations
• Basic motor theory
• Motor standards
• Stators
• Squirrel cage rotors
• Shafts
• Bearings & lubrication
• Motor accessories & terminal boxes
• Test & inspection procedures
• Motor alignment, vibration & noise
• Storage procedures
• Synchronous machines

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BOOK DOWNLOAD CD-ROM BOOK & CD-ROM

This book is also available focusing on IEC Standards ... IEC VERSION

We’ve covered how to assess impeller damage in a previous presentation. Now learn how to fix that damage. This presentation covers: 

• Replacing/repairing wear rings
• Repairing cavitation damage
• Impeller replacement options
• Dynamic balancing impellers

This book was developed to help electric motor technicians and engineers prevent repeated failures because the root cause of failure was never determined. There are numerous reasons for not pursuing the actual cause of failure including:

• A lack of time.
• Failure to understand the total cost.
• A lack of experience.
• A lack of useful facts needed to determine the root cause.

The purpose of this book is to address the lack of experience in identifying the root cause of motor failures. By using a proven methodology combined with extensive lists of known causes of failures, one can identify the actual cause of failure without being an “industry expert.” In fact, when properly used,  this material will polish one’s diagnostic skills that would qualify one as an industry expert.

The book is divided into the various components of an electric motor. In addition to a brief explanation of the function of each component and the stresses that act upon them, numerous examples of the most common causes of failure are also presented.

For this second edition, the manual has been reorganized and updated with new information including a new approach to methodology, new case studies and a new section covering synchronous machine failures. This could not have been done without many contributions from EASA members and the Technical Education Committee. 

The all new “Root Cause Methodology” section goes into great detail explaining that effective root cause failure analysis must take place within the context of a practical problem-solving methodology or framework. It covers a modified Plan-Do-Check-Act process that emphasizes the importance of planning and the related problem-solving methodology components. This section also explains A3, a high-level reporting tool that is very effective for problem solving.

In addition, besides a systematic approach to problem solving, root cause failure analysis of motors and motor systems requires familiarity with contributing factors attributable to various kinds of applications, environments and industries. This includes how various stresses can affect motor components and the reciprocal impact the motor system may have on the motor. This section includes a table with a detailed summary of motor stresses. 

There also is a new section on “Synchronous Machine Failures” and an expanded “Case Studies” section. Readers are guided through eight case studies.

With 328 pages, the book provides extensive information, including a wide range of failures, the likely causes listed, and the methodology for confirming the probable cause of each failure. 

Members may purchase a printed manual and/or a PDF download. The printed manual is in black and white, while the download shows most of the failure photos in color.  

Sections in the manual include:

• Root Cause Methodology (all new)
• Bearing Failures
• Stator Failures
• Shaft Failures
• Rotor Failures
• Mechanical Failures
• DC Motor Failures
• Synchronous Machine Failures (all new)
• Accessory Failures
• Case Studies (expanded)
• References

This book is available as part of EASA's Root Cause Failure Analysis seminar.

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PRINTED COLOR BOOK DOWNLOADABLE PDF PRINTED COLOR BOOK & PDF

DISCOUNTED BLACK & WHITE BOOKS!
Prices are now DISCOUNTED on remaining black & white books while supplies last! If you have already purchased a black & white manual and are interested in the color version, please contact EASA Customer Service (+1 314 993 2220).

B&W BOOK B&W BOOK & DOWNLOAD

By Gene Vogel
EASA Pump & Vibration Specialist

High vibration is a common problem for motors that are installed on top of vertical pumps. Its source can be a mechanical issue with the pump, motor or coupling or even hydraulic forces from the pump. Structural issues involving “reed frequency” resonance often amplify the problem, but effective diagnosis must begin with an understanding of the underlying vibratory forces. Although the general vertical pump category includes submersibles, this article focuses solely on the ones that most commonly exhibit high-vibration conditions: surface-mounted pumps with the motor bolted to a pedestal on top.

Topics covered in this article include:

• Mass unbalance
• Coupling type and alignment
• Mechanical action of pump shaft & impeller
• Hydraulic action of fluid
• Resonant frequencies
• Basic frequency analysis
• Trim balancing
• Other possibilities
• Vertical pump troubleshooting checklist

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Presented by Gene Vogel
EASA Pump & Vibration Specialist

Static-couple balancing has been addressed in prior EASA technical training sessions on balancing. This focused introduction will explain the what, how and why from a practical point of view. Knowing when this balancing technique works best will improve balancing results for both balancing machine operations and for in-place or field balancing. 

Topics include: 

• An explanation of single plane balancing  
• Two plane vs. static-couple balancing 
• When to use static-couple balancing 
• Simple static-couple vectors 
• Static-couple and balance tolerances 

Balancing is essential to machinery repair. Static-couple balancing is another tool to help technicians achieve positive results with the least effort.  

Vibration and balancing technicians, supervisors and engineers will benefit from this practical perspective.

Gene Vogel
EASA Pump & Vibration Specialist

Many EASA service centers conduct vibration-based machine condition monitoring programs for their customers. This is a valuable revenue source that aligns the service center as a team member with the customer to provide uptime on their machinery and control maintenance costs. It also puts some of the responsibility for predicting machine failures on service center personnel who may be managing vibration data for hundreds of machines in multiple customer facilities. Given that vibration data is complex, composed of amplitude, frequency and phase, that can be a daunting task.

It is generally impractical to conduct a proper vibration analysis on every machine for every route data collection event. Even simple four-bearing machines will have 3 to 12 measurement points with spectra data and waveform data on each point. Some measurement points will have multiple parameters recorded including velocity, acceleration and some special bearing band parameters. 

It is important to be able to use the proper software tools to screen data from routine data collection routes, identifying those machines that likely have developing faults. Then valuable analysis time is spent on machines that may have incipient faults, which if identified can allow repairs to avoid more extensive machine damage and downtime.

The first line of screening may be an overall vibration amplitude level which is known to be inordinately high. But overall vibration alarms will miss many incipient faults. Commonly, acceptable vibration levels from imbalance, flow turbulence on pumps and fans and background vibration will mask low amplitude vibration from bearing and other critical machine components. By the time the fault becomes evident in overall vibration levels, the fault is far advanced or a failure has already occurred.

There are several techniques for a more detailed screening of vibration data. The most common are frequency band alarms and enveloping. In addition, rule base “intelligent” algorithms can be implemented to screen for known fault patterns. 

A service center technician or engineer responsible for the success of a vibration based condition monitoring program should have a good understanding of these data screening techniques.

Also discussed in this article:

• Band alarms
• Enveloping or spectra alarms
• Rule based "intelligent" alarms
• Trending
• Concerns

Gene Vogel
EASA Pump & Vibration Specialist

Muchos centros de servicio llevan a cabo programas de monitoreo por condición basado en la vibración de las máquinas para sus clientes. Esta es una fuente valiosa de ingresos que integra al centro de servicio como miembro del equipo del cliente para garantizar el tiempo de funcionamiento de su maquinaria y controlar los costos de mantenimiento. Esto también pone parte de la responsabilidad de predecir fallos en las máquinas, en el personal del centro de servicio que puede estar gestionando los datos de vibración para cientos de máquinas en múltiples instalaciones del cliente. Dado que los datos de vibración compuestos por amplitud, frecuencia y fase son complejos, esta puede ser una ardua tarea.

En general no es práctico llevar a cabo un buen análisis de vibraciones en cada máquina para cada evento de recopilación de datos de la ruta. Incluso máquinas simples con cuatro rodamientos tendrían entre 3 y 12 puntos de medición, con datos de espectros y formas de onda en cada punto. Algunos puntos tendrán grabados múltiples parámetros, incluyendo velocidad, aceleración y algunos parámetros especiales de banda de frecuencia de rodamiento.

Es importante poder usar las herramientas de software apropiadas para filtrar los datos de las rutas de recolección de datos de rutina, identificando aquellas máquinas que probablemente tengan fallos en desarrollo. Después, se invierte valioso tiempo de análisis en máquinas que pueden tener fallos incipientes que, si son identificados, pueden permitir reparaciones para evitar tiempos improductivos y daños más graves. La primera línea de filtrado puede ser un nivel de amplitud general que se sabe es excesivamente alto. Pero las alarmas de vibración generales pasarán por alto muchos fallos incipientes. Por lo general, los niveles de vibración aceptables por desbalanceo, turbulencias de flujo en bombas y ventiladores y la vibración de fondo, enmascararán las vibraciones de baja amplitud de los rodamientos y de otros componentes críticos de la máquina. En el momento que el fallo se vuelve evidente en los niveles generales de vibración, el fallo se encuentra muy avanzado o ya ha ocurrido.

Existen varias técnicas para filtrar con más detalle datos de vibración. Las más comunes son alarmas de banda de frecuencia y el enveloping. Además, para filtrar patrones de fallo conocidos se pueden implementar los algoritmos “inteligentes” basados en reglas.

El técnico o el ingeniero del centro de servicio responsable del éxito del programa de monitoreo por condición basado en vibración, debe comprender bien estas técnicas de filtrado de datos.

This presentation examines:

• How the spectrum is generated from the vibration signal
• The effect of f-max ad resolution settings
• Averaging techniques
• Scaling and demodulation

This 12-part recording (15 hours) covers a wide range of topics on vibration.

Members rely on EASA to provide technical assistance and training in all areas related to machinery repair. In the area of machinery vibration, there are training providers that offer general classes in vibration analysis and balancing, but the content is geared to plant maintenance personnel who would be conducting in-plant predictive maintenance services. Some key areas important to EASA service center technicians is not covered adequately, and much of the content does not apply to vibration testing conducted in the service center. This course is designed to address those shortcomings and provide fundamental training in vibration analysis and balancing that directly applies to technicians working in the service center.

Main goals of the series
This webinar series was designed to:

• Provide EASA service center technicians with the technical knowledge they need to effectively measure and diagnose vibration on machines being tested in the service center.
• Provide the foundation understanding necessary to use vibration data as an indicator of machinery condition
• Provide the fundamental knowledge of dynamic balancing necessary to use common balancing instruments in the service center

LEARN MORE ABOUT THE COMPANION BOOK

Who would benefit from watching this series?
Service center technicians who measure and analyze machinery vibration, and those who must evaluate the vibration data will benefit greatly from the fundamental understanding and knowledge provided by this training series. Service center engineers who may be involved in writing, interpreting and applying vibration and balancing specifications and tolerances will gain a practical understanding of the terms, definitions and parameters encountered in those specifications.

As with any technical subject, fundamental math skills will allow attendees to quickly comprehend concepts and apply techniques. Vibration results from the mechanical and electrical forces at work in machinery, and a fundamental understanding of those forces, and machine components that cause them, will aid in the understanding and application of the subject matter.

Price
Downloadable version - $745 for members, $1,885 for non-members
DVD-ROM version (for viewing on a computer) - $795 for members, $1,985 for non-members