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.

Chuck Yung 
EASA Technical Support Specialist 

The problem:  We recently rebuilt a 2-pole motor and the centrifugal blower it drives. When the customer reinstalled them, he reported high vibration levels.  Everything runs smoothly for 10-15 minutes after a cold startup. Then the vibration starts to climb. We balanced the rotor and blower to G 1.0 tolerances. We even balanced each of the 7 blower impellers separately using a balancing mandrel. Shaft runout was less than 0.0002" on the motor and blower when we finished the job. The customer uses laser alignment. He is convinced that us to rebuild the blower again. What did we do wrong?

Gene Vogel
EASA Pump and Vibration Specialist

A quality repair in an EASA service center will yield a motor or pump that will meet just about any vibration spec­ification. And good EASA technicians could use their “finger vibrometer” to verify that. However, a large number of EASA customers demand a more formal means of verifying acceptably smooth operation. 

A few sophisticated customers have developed their own vibra­tion standards, but most depend on standards organizations such as the National Electrical Manufacturers As­sociation, or NEMA (electric motors), the Hydraulic Institute (HI) (pumps) and the International Organization for Standardization (ISO). There are also industry specific standards organiza­tions such as the American Petroleum Institute (API) for refineries and the Submersible Wastewater Pump As­sociation (SWPA). A working knowl­edge of the various standards will be beneficial for EASA service center technicians and managers.

Presented by Gene Vogel, EASA Pump & Vibration Specialist

When it comes to machine vibration, “how much is too much” depends on a number of factors. Knowing which standard and/or tolerance applies requires a working knowledge of the standards and some basics of vibration terminology. This  presentation provides an overview of where and how NEMA, IEC, ISO and Hydraulic Institute standards may apply to machines commonly encountered in EASA service centers.

• NEMA, IEC, ISO and Hydraulic Institute standards
• Basic vibration terminology
• What standard applies?

Target audience: Service center managers, engineers, in-shop and field service technicians can benefit from a clearer understanding of vibration standards and terminology.

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.

Chuck Yung 
EASA Technical Support Specialist 

When vibration problems occur, the magnitude and direction of the vi­bration can give a good indication of where to look for the cause. When vi­bration is higher in the vertical plane, one of the first things we should examine is the base/foundation of the motor. If the high vertical readings are compounded by indications of an eccentric airgap, such as high axial vibration and a predominant twice-line-frequency vibration, a “soft foot” or twisted frame is often to blame. 

Construction basics 
It is common practice for the align­ment technician to use prefabricated shims under the feet, sized to accept the hold-down bolt. The person perform­ing the alignment may not realize that a motor frame is not as solid as it appears. The fact that the foot itself might be over an inch (25 mm) thick, and the frame is cast iron or steel, causes the person to assume that it cannot distort. Nothing could be further from the truth. Because of that assumption, shims are often not placed to the greatest benefit. By understanding some construction basics, we can better place the shims to obtain the lowest vibration readings. 

Gene Vogel
Especialista de Bombas & Vibraciones de EASA

La herramienta más básica usada por los analistas de vibraciones son los espectros. Este es un gráfico que ilustra las frecuencias presentes en una señal de vibración y sus amplitudes relativas. Una buena forma de entender el espectro es como si se tratara de un “gráfico de barras” de las frecuencias, con cientos de “barras” verticales individuales a través de un rango de frecuencias. La mayoría de los espectros muestran la amplitud más alta en cada barra de frecuencia como un solo punto, por lo que el gráfico aparece como una línea escarpada que refleja las amplitudes más altas para cada una de las barras. La frecuencia más alta del gráfico se llama fmax y el número de barras del gráfico se conoce como “número de líneas de resolución”.

Gene Vogel
EASA Pump and Vibration Specialist

There are three fundamental parameters for machinery vibration data:  amplitude, frequency and phase. When testing machine vibration, amplitude and frequency are the two primary measurements for acceptance testing and for diagnostics. Both of these parameters have several units in which they can be recorded. 

Converting from one unit of measurement to another is not difficult if both amplitude and frequency data are available. In many cases, only amplitude measurements are available, without the needed frequency information, so conversion to other amplitude units is not possible. 

Knowing when conversion is possible and how to a apply conversion formulas is important when assessing customer specifications and analyzing diagnostic data.

Gene Vogel
EASA Pump & Vibration Specialist 

As we communicate internationally, language barriers persist. In the technical fields, the metric-imperial units clash is slowly diminishing. (It’s been said the U.S. is going to the metric system an inch at a time.) In the vibration analysis field, metric and imperial units for vibration amplitude both remain prolific. Many vibration analysts are “bilingual” in that respect and are comfortable using either system. But for more casual users who may only encounter vibration data in regard to meeting specs, unfamiliar vibration amplitude units can be a challenge. 

Complicating the situation is the fact that even within one of the systems (metric or imperial), conversion between different vibration amplitude parameters is often not understood. Common vibration amplitude parameters are displacement, velocity and acceleration, and the conversion between them requires applying a factor for the frequency of the vibration. Frequency itself has three different units: cycles per minute (CPM), cycles per second (Hz) and multiples of rotating speed (Orders). Throw in the issue of Peak to Peak (Pk-Pk), Peak (pk) and root-mean-squared (rms), and applying vibration amplitude specifications can be challenging even before one encounters a metric-imperial units situation. (For an easy solution skip to the end of this article.)

Gene Vogel
Especialista de Bombas y Vibraciones de EASA 

A medida que nos comunicamos internacionalmente, persisten las barreras del idioma y en el campo técnico, el choque entre unidades métricas y en pulgadas está disminuyendo lentamente. (Se ha dicho que Estados Unidos está adoptando el sistema métrico y en pulgadas al mismo tiempo). En el campo del análisis de vibraciones, las unidades métricas y en pulgadas para la amplitud de la vibración siguen siendo prolíficas. Muchos analistas de vibraciones son “bilingües” y se sienten cómodos utilizando cualquiera de los sistemas. Pero para los usuarios ocasionales que tal vez solo encuentren datos de vibración con respecto al cumplimiento de las especificaciones, las unidades de amplitud de vibración desconocidas pueden ser un reto.

Lo que complica la situación es el hecho de que incluso dentro de uno de los sistemas (métrico o en pulgadas), a menudo no se comprende como convertir los diferentes parámetros de amplitud de la vibración. Los parámetros comunes de amplitud de vibración son el desplazamiento, la velocidad y la aceleración, y la conversión entre ellos requiere aplicar un factor para la frecuencia de la vibración. La frecuencia en sí tiene tres unidades diferentes: ciclos por minuto (CPM), ciclos por segundo (Hz) y múltiplos de la velocidad de rotación (Órdenes). Si a esto le sumamos las medidas pico a pico (Pk-Pk), pico (pk) y raíz cuadrada media (rms), la aplicación de las especificaciones de amplitud de la vibración puede ser un desafío incluso antes de que uno se encuentre con una situación de unidades métricas-pulgadas. (Para encontrar una solución sencilla, vaya al final de este artículo).

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.

REVISED September 2022!

The EASA Technical Manual, containing more than 900 pages of information specific to electric motor service centers, is available FREE to EASA members as downloadable PDFs of the entire manual or individual sections. The printed version is also available for purchase. Each of the 13 sections features a detailed table of contents.

VIEW, DOWNLOAD OR PURCHASE

This 40-page booklet provides a great marketing tool for your service center! Use it to provide end users with information that will help them obtain the longest, most efficient and cost-effective operation from general and definite purpose electric motors with these characteristics:                                                                                                          

• Three-phase, squirrel-cage induction motors manufactured to NEMA MG 1 standards 
• Power ratings from 1 to 500 hp (1 to 375 kW)                                        
• Speeds of 900 to 3600 rpm (8 to 2 poles) 
• Voltages up to 1000V, 50/60 Hz 
• All standard enclosures (i.e., DP, TEFC, WPI, WPII) 
• Rolling element (ball and roller) and sleeve bearings

This booklet covers topics such as:

• Installation, startup and baseline information
  • Basic system considerations
  • Installation
  • Startup procedures
  • Baseline data
  • Total motor management
• Operational monitoring and maintenance
  • Application specific considerations
  • Preventive, predictive and reliability-based maintenance
  • Inspection and testing
  • Relubrication of bearings
• Motor and baseline installation data
• How to read a motor nameplate
  • Overview
  • Required information
  • Other terms
• Motor storage recommendations
  • Motor storage basics
  • Preparation for storage
  • Periodic maintenance

This resource is provided as a FREE download (use the link below). You can also purchase printed copies ready to distribute to your current or potential new customers. The cover of this booklet can also be imprinted with your company's logo and contact information (minimum order or 200). Contact EASA Customer Service for details.

READ MORE ABOUT THE FEATURES AND BENEFITS

Chuck Yung
EASA Senior Technical Support Specialist

One of the more mundane things we as repairers must be concerned with is motor storage. For many of us, storing large motors for major customers is its own profit center. For all of us, being aware of how our customers store the motors we repair and send to them is critical to customer satisfaction. A poorly stored motor is likely to suffer winding or bearing failure, and we don’t want unrealistic warranty claims over something outside our control.

Our primary concerns when storing motors, especially long-term, are windings, bearings and shaft sag.

Gene Vogel
EASA Pump & Vibration Specialist
and
Walter Barringer
Mobius Institute, Knoxville, TN

Temperature is hot or cold, pressure may be high or low and a tank may be full or empty. But vibration cannot be adequately described by a single parameter. Vibration is composed of amplitude, frequency and phase. Overall amplitude may be used as a simplistic indicator of machinery condition; much like a noise could be described as loud or soft, even though there is a big difference between the scream of a siren and the roar of a train. And so it is with vibration.

The siren sounds different than the train because they are different frequencies. In the same way, the vibration from a failing rolling element bearing can be distinguished from coupling misalignment. This combination of vibration amplitude and frequency is the most common and useful vibration data for determining machinery condition, and analyzing machinery vibration problems. The phase angle of the vibration plays an important role in dynamic balancing and advanced analysis. The analysis of vibration amplitude and frequency as represented in the vibration spectrum, is the topic of this paper.

This paper covers how to get the vibration spectrum and what it means, including:

• Wave form
• Displacement
• Velocity
• Demodulation

Gene Vogel
EASA Pump & Vibration Specialist

When machine vibration increases, one of the first questions asked is: "Is a failing bearing causing the vibration?" In the case of rolling element bearings, it is not difficult to separate vibration caused by a failing bearing from other common faults such as unbalance, misalignment, looseness, etc. But sorting out vibration from a failing rolling element bearing (here-after called "bearing vibration") from process sources such as flow induced and background vibration can be more demanding. The secret is to identify the frequency at which a flaw on a roller or raceway will impact the mating bearing component. These are commonly known as bearing fault frequencies.

Topics covered include:

• Simple to complex steps in identifying bearing vibration
• "Locate rpm" function
• Occurance of sidebands

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!

BUY COPIES OF THIS HANDBOOK

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

Chuck Yung
Especialista de Sénior de Soporte Técnico de EASA

Una de las cosas más mundanas de las que debemos preocuparnos como reparadores es el almacenamiento de los motores y para muchos, almacenar motores grandes para clientes importantes representa ganancias. Para todos nosotros, ser conscientes de cómo nuestros clientes almacenan los motores que les reparamos es crítico desde el punto de vista de la satisfacción del cliente. Es probable que un motor mal almacenado sufra fallos en el devanado o en los rodamientos, y no queremos reclamos por garantía poco realistas sobre algo que está fuera de nuestro control.

Nuestras principales preocupaciones al almacenar motores, especialmente a largo plazo, son los devanados, los rodamientos y el pandeo del eje.

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.

Tom Bishop, P.E. 
EASA Technical Support Specialist 

Mechanical resonance can be defined as the amplification of the vibration level of a mass or structure at its natural frequency, caused by excitation from an external source. For a rotating mass, this amplification occurs at the critical speed(s). Electrical resonance causes an amplification of the magnitude of voltage or current, or both. The increase in amplitude, whether mechanical or electrical, increases the stress on motor components and negatively affects operation, e.g., increased vibration, instability, increased energy consump­tion, and premature failure. 

By receiving energy from an external source, the resonant condition can cause the magnitude of the disturbance to continue to increase until a fault occurs. Mechanical resonance can lead to breakage of motor and drive compo­nents, and electrical resonance can result in winding failure. In this article we will discuss mechanical and electrical resonance associated with motors and drives, and provide some solutions to address them. 

Gene Vogel
EASA Pump and Vibration Specialist

When a motor is test run in the service center, the two most common vibration frequencies that occur are at 1x rotating speed (1x rpm) and at 2x line frequency (2x lf). High 1x rpm is often corrected by balancing, and the 2x lf is traditionally attributed to air-gap anomalies or voltage or winding unbalance. However, there are those cases where the traditional approaches are unsuccessful and technicians and managers are left scratching their heads. In these difficult cases, there is often a combination of electrical and mechanical vibration. Being able to separate electrical and mechanical vibration is necessary to efficiently arrive at a solution.

Anyone dealing with installed machinery, or even test running motors in the service center, will encounter instances where structural resonance is amplifying machine vibration. The machine may meet stringent specifications in one instance but exceed acceptable vibration levels in another. A good understanding of natural frequencies and the tests necessary to identify them will help solve these vexing situations.

This presentation covers:

• What is a natural frequency and why do they exist
• How to conduct a basic bump test with a single channel analyzer
• What is a modal analysis and what additional information does it provide
• Related tests and concerns

This webinar is useful for service center technicians, supervisors and managers.

​Este folleto de 40 páginas ofrece una gran herramienta de marketing para su centro de servicio! Lo utilizan para proporcionar a los usuarios finales con información que le ayudará a obtener la, operación más eficiente y rentable de propósito más larga de los motores eléctricos generales y definidas con estas características:

• Trifásica, motores de inducción de jaula de ardilla fabricados con las normas NEMA MG 1
• Los valores de potencia de 1 a 500 CV (1 - 375 kW)
• Velocidades de 900 a 3600 rpm (8 a 2 polos)
• Tensiones de hasta 1000 V, 50/60 Hz
• Todas las cajas estándar (es decir, DP, TEFC, WPI, WPII)
• Rodando elemento (bolas y ruedas) y los cojinetes de manguito

Este folleto cubre temas tales como:

• Instalación, puesta en marcha y la información de base
• monitoreo y mantenimiento operativo
• Datos del motor y la instalación de línea de base
• Cómo leer una placa de identificación del motor
• recomendaciones de almacenamiento del motor

Este recurso se ofrece como una descarga gratuita (utilizar el enlace más abajo). También puede comprar copias impresas listo para distribuir a sus actuales o potenciales nuevos clientes. La portada de este folleto también se puede imprimir con el logotipo e información de contacto de su empresa (pedido mínimo o 200). Póngase en contacto con Servicio al Cliente EASA para más detalles.

Tom Bishop, P.E.
EASA Senior Technical Support Specialist

We often hear the terms preventive maintenance (PM) and predictive maintenance (PdM) of electric motors. However, it’s far less often that we give consideration to the tasks associated with these methods of maintaining motor operation and extending operating service life. This article will address some of the more common activities associated with PM and PdM, with the focus on three-phase squirrel cage motors.

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

COMPRAR

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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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

Gene Vogel
EASA Pump and Vibration Specialist

Resonance is a property of all mechanical structures. It can be described as a sensitivity to a certain vibration frequency. For machinery such as electric motors, pumps, turbines, etc., it becomes a problem when small vibratory forces from the machine operation are amplified by mechanical resonance. The result can be very severe vibration levels, even when the exciting forces are small. Often resonance is encountered when a speed change has been implemented, as with retrofitting a VFD or operating a 50 Hz motor on 60 Hz power.

The most common example of resonance is when the structure supporting a machine is resonant at or near the rotating speed of the machine. Even slight vibratory forces from residual unbalance and misalignment will excite the resonant base structure, resulting in severe vibration. The machine components can also be resonant. There are many examples of 2-pole electric motors where a resonant endbracket caused very high axial vibration at 1 x rpm or 2 x rpm.

A second category of resonant conditions occurs when the resonant component is the rotating element of the machine. This is common with gas and steam turbines, centrifugal pumps and 2-pole electric motors. While the result is similar (high vibration when a certain operating speed is reached), this is a more complex phenomenon. When the operating speed reaches the resonant frequency of the rotating element, the rotating element actually distorts and the vibratory forces increase significantly.

There is a need to distinguish between these two types of resonance. The first, where a supporting structure or non-rotating machine component is resonant, is usually referred to as a “structural resonance.” The second, where the rotating element is resonant, is known as the “rotor critical speed.” This leaves the term “critical speed” (without the word “rotor”) somewhere in limbo.

Technically, a critical speed could be either a structural resonance or a rotor critical speed. For the sake of clarity it’s best to avoid using that term. The simple term “resonance” can be applied to both conditions to avoid confusion.

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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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.

Chuck Yung
EASA Senior Technical Support Specialist

The case study in this article demonstrates that EASA members have great opportunities to develop and improve customer relationships by helping them solve their application problems.

Several generators driven through gearboxes at a hydro site ran fine for years, until one excitor failed electrically. After being repaired and reinstalled, it performed well electrically but vibrated more than the other units. A few months later, a second generator experienced a bearing failure. The unit was repaired by the same service center, and it also vibrated after repair and reinstallation. By the time a third unit lost an excitor, the customer was looking for a different service center. Unfortunately, the results were the same. The customer pursued the issue.

All told, four shops worked on these generators, but none improved the vibration. Finally, the first shop got another try. This time, a new technician examined the problems encountered and listened to those who were involved previously. Just as important, he looked at the application itself: the generators had welded rib frames, covered by sheet-metal shrouds. They were a two-bearing style, with an overhung excitor. The generator was then repaired and installed using the procedures outlined by the technician - and ran smoothly. What did the technician do to correct the problems?

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

Gene Vogel
EASA Pump & Vibration Specialist

When machinery vibration becomes severe, resonance is often at work. Methods of testing machines for natural frequencies that cause resonance have been discussed in prior presentations. This presentation will first focus on identifying resonance and then move to methods that help visualize the vibratory motion, helping to identify solutions. Two methods will be discussed- traditional Operating Deflection Shape (ODS) analysis and video motion magnification.

Learning objectives:

• Review of testing methods
• How to visualize vibratory motion
• Operating deflection shape analysis
• Understanding video motion magnification

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Gene Vogel
EASA Pump & Vibration Specialist

Vibration is the most effective and well-recognized parameter for assessing the mechanical condition of electric motors. Generally, lower vibration levels are equated with improved reliability. However, arbitrarily reducing the vibration level specification for acceptance of new and repaired motors will not necessarily result in improved reliability, and it will definitely increase costs. Further, reliance on vibration levels at 2x line frequency (2xlf) as an indicator of electric motor reliability is not effective.

EASA service centers should be on the lookout for "tight" vibration acceptance requirements. Be prepared to work with your customer to ensure a cost effective and realistic approach to setting motor acceptance criteria.

Topics covered include:

• "Tight" specifications
• Cost of compliance
• Unbalance (1xRPM)
• Harmonics of 1xRPM
• 2x line frequency
• Bearing fault frequencies

By Jane Alexander
Managing Editor of Maintenance Technology

According to EASA’s technical experts, changes in motor/system vibration readings provide the best early warning of developing problems in a motor or system component. Other parameters to monitor may include operating temperature of critical components, mechanical tolerances, and overall system performance, including outputs such as flow rate, tonnage, and volume.

Motor-specific baselines incorporate records of electrical, mechanical, and vibration tests performed when units are placed in operation or before they’re put in storage. Ideally, baselines would be obtained for all new, repaired, and in situ motors, but this may not be practical for some applications. These baselines typically include some or all of the following:

• Load current, speed, and terminal voltage
• Motor current signature analysis (MCSA)
• Mechanical tests
• Vibration
• Infrared thermography
• New motor baselines
• Repaired motor baselines

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Dave Felten 
Mechanical Field Service Department 
L&S Electric, Inc. 
Schofield, Wisconsin 

Welcome to the age of predictive maintenance technologies. More and more of our customers are using tools such as vibration analysis to assess the health of their rotating equipment. 
Many of our customers are using this technol­ogy to assess new and rebuilt rotating equipment once it’s installed and running. 

This serves two main purposes: 

1. It demonstrates the quality of the newly acquired/repaired equipment (taking the burden off the supplier/service center should the equipment vibrate once it’s installed). 
2. It provides a baseline for trending. Unfortunately, these initial vibration readings can be pushed into an “alarm status” by many customer-related issues such as poor coupling alignment and/or machine installation. This is why it’s so important for today’s repair facility to provide the customer with “baseline” vibra­tion data gathered during its final test run, providing evidence that the rotating equipment ran within general vibration guidelines before being shipped. 

Gene Vogel
EASA Pump & Vibration Specialist

Vibration has three primary parameters; amplitude, frequency and phase. Previous presentations and papers have focused on the two most common parameters, amplitude and frequency. These two are the primary tools for determining if a machine vibration is a problem, and what the cause of the vibration might be. This paper, presented at the 2013 EASA Convention, focuses on the third parameter: phase angle.

While vibration phase angle has several perspectives, this paper focuses on the most straightforward aspect — the angular relationship between vibratory motions of two different locations on a machine. Inherently, then, phase angle is based on two different inputs and measuring phase requires two input signals. The two signals can be two vibration transducers, or a single vibration transducer and a reference pulse signal from a photo tach, laser tach, key phasor or such. For those who are familiar with using a strobe light and a single transducer to measure phase angle, your eye and the reference mark on the shaft provide the second input.

Phase angle is seldom used to detect when a problem occurs on a machine. But it is a powerful tool for diagnosing vibration in many common situations. It also provides necessary data for dynamic balancing. For phase to be useful in any situation, it must be coupled with the corresponding vibration amplitude. Together, phase and amplitude constitute a vector. A basic understanding of vectors is fundamental to vibration analysis.

This paper covers:

• Amplitude and phase concepts
• Shaft alignment vector analysis
• Planar shape sketches
• Animated Operating Deflection Shape (ODS)
• ODS instrumentation and software

Vibration data from field measurements can tell a great deal about the health of machine components and required follow-up action. Beyond acquired time waveform or spectral frequency pattern data, several tools are available in most portable vibration instruments to determine natural frequencies, shaft centerline motion, and the relative movement of machine components. Drawing on practical examples, this paper will also cover:

• Startup/coast down analysis
• Bump tests
• Cross-channel phase measurement
• Demodulation techniques
• Orbital plots

Tom Bishop, P.E.
EASA Senior Technical Support Specialist

For most service centers the traditional repair services such as electric motor rewinding have been and will continue to be in a state of decline over time. Among the factors leading to this reduction in business are conversions to more efficient motors, improved maintenance of existing motors, incentives to replace with more efficient motors and in some regions a reduction in the industrial customer base. A consequence of this is that there is more competition for a “shrinking pie”. Service center reaction can be to make a comparable reduction in size or become pro-active and seek new business. The objective of this paper is to suggest and detail some of these alternatives, namely value-added repair and service opportunities for service centers that carry with them the added benefit of contributing to optimizing motor reliability.

The opportunities for value-added repairs and services are ever-increasing. Topics covered here are:

• Bearing isolators, increased winding wire area, ball-to-roller/roller-to-ball bearing conversions
• Preventive and predictive maintenance (PM & PdM) services: vibration analysis, condition monitoring, bearing lubrication, electrical testing (IR, amps, volts, kW)
• Motor management
• New premium efficient motors vs. repair and retrofitting of existing motors

This 48-page manual was developed following EASA’s 12-part Vibration for Service Centers webinar series. It serves as an introductory training resource for service center technicians and supervisors involved in measuring, evaluating, and correcting vibration and balancing issues on machines under repair – as opposed to the in-plant predictive maintenance tasks covered in most general classes on the subject.

This document is intended as basic introductory training material for anyone who may be involved in evaluating or correcting vibration issues on machines repaired in the service center. Only certain sections may be of interest depending on the area and amount of involvement in vibration issues.

For a technician with responsibility for analyzing and correcting vibration and balancing issues, a general understanding of all of the information is essential. For technicians who will conduct field vibration and balancing services in customers' facilities, additional training is strongly recommended. A Level 1 vibration analysis class (usually 4 or 5 days) is a first step toward the competence needed for conducting field services. A Level 2 class is recommended. A number of providers offer ANSI-certified Level 1 and Level 2 vibration analysis classes, which normally include an opportunity for certification.

Major sections in the document include:

• Introduction and Overview
• Vibration Basics: Amplitude, Frequency and Phase
• Vibration Tolerances
• Basic Vibration Analysis
• Dynamic Balancing Basics
• Resonance
• Rolling Element Bearing Vibration
• Demodulation and High Frequency Band Measurements
• Field Analysis Techniques
• Field Balancing—Problems and Solutions

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Dan Patterson 
Flanders Electric Motor Service, Inc. 
Evansville, Indiana 
Technical Services Committee Member 

Few things in your business life can be more annoying than a large envelope marked CONFIDENTIAL that contains repair specifications from a potential “large” customer. Right? Well things may not be as bad as they seem. Vibration standards, properly written, not only benefit the customer by adding longevity to their equipment but also can equally benefit your business by reducing warranty claims. Vibration analysis has been determined to be the best indicator of rotating equipment mechanical faults. Identification of frequency components can be a valuable tool in determining if faults exist before returning the finished product to the customer.

A special discounted collection of 9 webinar recordings focusing on a wide variety of vibration, balancing and alignment topics.

Once purchased, all 9 recordings will be available on your "Downloadable products purchased" page in your online account.

Downloadable recordings in this bundle include:

An Overview of Vibration Tolerances
Presented August 2019

When it comes to machine vibration, “how much is too much” depends on a number of factors. Knowing which standard and/or tolerance applies requires a working knowledge of the standards and some basics of vibration terminology. This  presentation provides an overview of where and how NEMA, IEC, ISO and Hydraulic Institute standards may apply to machines commonly encountered in EASA service centers.

• NEMA, IEC, ISO and Hydraulic Institute standards
• Basic vibration terminology
• What standard applies?

Target audience: Service center managers, engineers, in-shop and field service technicians can benefit from a clearer understanding of vibration standards and terminology.

Basics of Machinery Foundations and Bases
Presented November 2012

A faulty machine foundation or base can lead to excessive vibration and premature failure. This presentation explains the fundamentals of machinery foundation construction and how to identify and troubleshoot machine base problems, including basic vibration techniques and ODS analysis.

Fundamentals of Shaft Alignment
Presented November 2012

Automatic alignment instruments are no substitute for the underlying process of aligning direct-coupled machines. This presentation explains the simple calculations that govern the alignment process. That understanding will allow technicians to use any alignment tool more effectively and deal with issues that confound the process.

Shaft Alignment
Presented March 2016

This webinar recording provies a straightforward look at the simple relationship between shaft centerlines that is known as shaft alignment. Bypassing the common discussion of laser and manual instruments, this presentation gets to the heart of the shaft alignment process. Topics covered will include:

• Fundamental concepts
• How to visualize machine case position
• Practical solutions for moving machine cases
• Applying tolerances
• The foot-base-foundation connection

ANSI's New Shaft Alignment Standard
Presented July 2018

This presentation introduces you to ANSI's new shaft alignment standard. Topics covered include:

• A discussion of alignment Quality grades, AL 1.2, AL 2.2, AL 4.5
• Shaft alignment tolerances
• Issues affecting measurements
• Conditions affecting alignment stability

Target audience: This presentation benefits service center technicians and supervisors looking to improve shaft alignment knowledge and skills. 

How to Balance Overhung Fans
Presented October 2011

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.

Vibration on Belt Driven Machines
Presented June 2013

This presentation focuses on:

• Identifying belt vibration
• Identifying pulley pitch line run-out vibration
• Other vibration sources
• ODS analysis

The FFT (aka Spectrum): What It Is and Ways to Use It
Presented July 2012

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

Vibration Problems on Vertical Motors and Pumps
Presented December 2010

When motors are installed on top of vertical pumps, high vibration is a common problem. The problem may be mechanical, hydraulic or structural.

This presentation provides an understanding of the nature of this style pump and the various forces essential to diagnosing and correcting vibration problems on vertical pump motors.

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

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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

Gene Vogel
EASA Pump & Vibration Specialist

The ability to measure machinery vibration is essential to machinery repair. But vibration is a complex phenomenon, with multiple parameters; specifically, amplitude, frequency and phase. So unlike temperature, pressure or other single parameter indicators, to use vibration as an effective machine condition indicator, technicians need more than simple meter and 5 minutes of instruction. The most common vibration related task for EASA service centers is acceptance testing for repaired machines. Even this basic task requires:

• Knowledge of vibration fundamentals
• Adequate vibration instrumentation
• Documented acceptance criteria
• Proper mounting methods
• An awareness of advance analysis techniques

This paper addresses the concerns related to insuring the service center has adequate vibration instrumentation. While needs vary among service centers, the basic instrument required is a portable vibration analyzer. In order to qualify as a vibration analyzer, the most basic instrument functions are the ability to measure vibration amplitude and frequency, and common tools for analyzing a vibration spectrum. There are a number of instruments that meet these basic requirements, and most offer additional useful capabilities. Choosing an instrument that meets a specific service center’s needs should involve all of the stakeholders, which includes owners, managers, engineers and technicians. For smaller service centers, it may be one person who wears all those hats, and the decision process is simplified. For larger service centers, input from a dozen people may be needed, and there will be trade-offs on costs vs. benefits. In either case, and those in between, it’s important that considerations include:

• Features and capabilities
• Cost
• Convenience
• Durability
• Support
• Training

This paper focuses on features and capabilities. Not to diminish the importance of the other components, but those are best left to discussion between the service center and the various instrument vendors.

This paper covers:

• Heritage instruments
• Spectrum analyzers
• Balancing instruments
• Online monitors
• Portable vibration level meters
• Proximity probes and instruments
• Accelerometer transducers

This presentation focuses on:

• Identifying belt vibrartion
• Identifying pulley pitch line run-out vibration
• Other vibration sources
• ODS analysis

Gene Vogel
EASA Pump and Vibration Specialist

When motors are installed on top of vertical pumps, high vibration is a common problem. The source of the problem can be a mechanical issue with the pump, motor or coupling, or it can be hydraulic forces from the pump. Often structural issues involving resonance amplify the vibration. An understanding of the nature of this style pump and the various forces is essential to diagnosing and correcting vibration problems on vertical pump motors.

There are quite a number of configurations of vertical pumps. Submersible pumps fall into this general category. This discussion, however, will omit submersibles and focus on those pumps that are surface mounted where the motor is bolted to a pedestal on top of the pump. See Figure 1. This is the style that most commonly exhibits high vibration conditions. An important contributing condition is resonance, and specifically “reed frequency” resonance. But an understanding of the vibratory forces is important also.

When motors are installed on top of vertical pumps, high vibration is a common problem. The problem may be mechanical, hydraulic or structural.

This presentation provides an understanding of the nature of this style pump and the various forces essential to diagnosing and correcting vibration problems on vertical pump motors.

Gene Vogel
EASA Pump & Vibration Specialist

The most basic tool a vibration analyst uses is the vibration spectrum. The spectrum is a graphic illustration of the frequencies present in a vibration signal and their relative amplitudes. A good way to understand the spectrum is that it is a “bar graph” of the frequencies, with hundreds of individual vertical frequency “bars” across a range of frequencies. Most spectra are displayed with only a single dot for the highest amplitude in each frequency bar, so the graph appears as a jagged line reflecting those highest amplitudes for each bar. The highest frequency in the graph is called the fmax and the number of bars in the graph is known as the “number of lines of resolution.”

Dan Patterson 
Flanders Electric Motor Service, Inc. 
Evansville, Indiana 
Technical Services Committee Member 

Ensure A Quality Product 
In the previous article referenced above, I covered methods and criteria for testing motors in the service center. Service centers make every effort to ship a quality rebuild. On occasion, the test-run data may have suspicious characteristics. Even though the motor meets the vibration standards, further investigation is warranted. The motor may exhibit a noise, rumble, or exces­sive bearing temperatures. Spectral data might contain harmonic families, or wave-form data contains impacting. In this circumstance, I will make the statement: “It will never be as close to a motor repair service center as it is now.” Accurate test-run docu­mentation can prove invaluable as a comparison tool when judg­ing the performance of a motor once it is installed. After all, you did ship a quality product, didn’t you?