English Abstracts

Here are the abstracts of the CMVA technical papers. Members of CMVA are able to view and download the abstracts through the members section of the website.

 

Natural Frequencies Of The Hand-Arm System Using Finite Element Method And Arma- Surajudeen Adewusi , Marc Thomas, Vu Viet Hung and Li Wenchao

Natural Frequencies Of The Hand-Arm System Using Finite Element Method And Arma

 

Added Mass Effect on the Dynamic Response of Structures – A Study on a Hydro Runner

Any vibrating structure submerged in fluid experiences the opposing force of the fluid opposing vibration. The effect of the fluid on structural dynamics is known as “added mass”. Runners of
hydroelectric turbine generators are subjected to various excitation mechanisms. The natural
frequencies and mode shapes of a runner are important parameters which determine its behavior
and response to these various excitations. Added mass effect lowers natural frequencies of a system
while submerged in water as compared to in air. This paper outlines the concept of added mass
and compares the natural frequencies of a runner in air versus water as calculated via Finite
Element Analysis (FEA). The FEA model was initially validated through experimental modal
analysis (EMA) performed on the runner removed from the turbine generator. FEA and EMA
results are compared and discussed.

 

Testing for Resonance- Dora Orchard

Structures and equipment exposed to mechanical vibrations as well as ambient vibration are susceptible to resonances. Predicting resonance or potential resonant amplification is a desirable thing to achieve for many reasons. Operation of equipment at or near resonance can result in catastrophic failure, reduced reliability and functionality. Knowing the natural frequency characteristics of equipment will assist in the successful design and /or modification and operation of mechanical components and structures. This presentation will explore what resonance is, conditions that lead to recommendations for performing this testing, and test methods with analysis you can perform.

 

Using Acoustic Imaging Defect Detection- Gilles Lanthier

Exploring the use of Acoustic Imaging to discover and evaluate leaks as well as electrical and mechanical defects.

 

Vibration control of a piezoelectric cantilever smart beam by ℒ1 adaptive control system- Ali Tirtashi

In this project, the modeling and design of an L1 state feedback adaptive control system applied for vibration control of a smart piezoelectric Euler–Bernoulli cantilever beam is presented. For a Single-Input Single-Output (SISO) case by considering the first two dominant vibratory modes, the dynamics of the system are presented. Three Piezoelectric patches, two as actuators and the other as a sensor are bonded to the structure at the support of the beam and along the length of the beam. L1 adaptive control law, with time-varying parameters and in the presence of disturbance, is employed to suppress the vibration of the beam. The beam structure is modeled in the state space form using the concept of piezoelectric theory, the Euler–Bernoulli beam theory, and the Finite Element technique. The proposed controller is also compared with PID and LQR control systems.

 

Reciprocating Compressor High Frame Vibration – Case Study- Nisarg Talati & Alexandre Gauthier

This case study tells the story of a one-of-a-kind reciprocating compressor failure mode captured with a Prognost protection and condition monitoring system. The compressor tripped suddenly on a high crankcase vibration event without any leading indicator. A systematic analytical approach will be presented from the trip event that trigger the protection system, through a complete compressor vibration signature analysis and risk review that led to an adequate decision-making process. Plausible failure modes hypothesis will be presented based on compressor dynamic and load characteristics. A targeted scope of works based on data and fact will be presented. Mechanical inspection findings with analysis of primary component failure mechanism and secondary damage propagation will be reviewed. A failure mode timeline will be reconstructed based on sound mechanical engineering concepts and asset operation understanding. A final discussion on protection system effectiveness and optimization will be done to reduce the consequence on health & safety, environmental, regulatory and financial receptors on up coming issues. Asset reliability is a journey, we must learn from asset failures to improve system effectiveness and improve operational safety.

 

Condition Monitoring of Deep Draft Vertical Centrifugal Pumps- Jesse Lapaire

A presentation consisting of guidelines and suggestions for the condition monitoring of deep draft vertical centrifugal pumps, as well as two case studies:

Case Study 1: Reviewing the root cause and lessons learned behind a raw service cooling water pump which had shaft whipping resulting from loss of the suction bell end and its interference with the with impeller.

Case Study 2: Tracking the story (detection of fault to correction/overhaul) of a 395 RPM single stage 7.55 cubic meter/second centrifugal cooling water pump with an impeller rub at the end of its 40 foot shaft.

 

Hydraulic Turbine Generator

As the world shifts from carbon based energy production so does the reliability focus on existing and new green technology. In the hydraulic energy production space, there is renewed focus on ISO and CEATI standards to establish balance quality and operating vibration amplitude limits. Additional stresses are placed on assets with expanding operation envelopes, requiring generators to operate anywhere from synchronous condensing to maximum load. This presentation will review experiences with creating a return-to-service test plan based on ISO 20816-5 (limits) and ISO-21940 (balance quality) for a full operating range. Experiences with mechanical and load dependent (electrical and thermal forces) balancing options for a full operating range will also be discussed.

 

Case Study of a Power Turbine- Gary Zhang

A power turbine had been experiencing vibration trips during normal operation. During the event, a one-half (1/2X) vibration component emerged in the spectrum. This usually a good indication of that a light rubbing may have been developed at a seal area. Data analysis helped understand its vibration behavior and locate the rubbing area. The understanding was rather helpful for maintenance and operation teams going forward.

 

Using Mobile Phone Camera’s and Slow-Motion Video Recording- Dr. Thierry Erbessd

High resolution mobile phones with slow-motion recording capability provide an amazing resource for reliability professionals. We’ve already seen slow-motion mobile phone camera’s used in place of strobe lights to visualize and identify common faults like broken keyway’s, material build up on fans and more.

In this case study we will explore and evaluate the effectiveness of utilizing mobile phone video recordings for vibration analysis of rotating equipment to identify common machine health faults that previously required the use of hard-wired sensor technology in a non-contact method video post processing method.

Several different examples will be used to clearly identify misalignment, imbalance, looseness, phase related issues, and more.

Learning Objective: Understand the power of mobile phone camera technology available to nearly every reliability professional as they already have the phone available as a tool.

 

How to financially justify investment in your PdM program- Vincent Bédard, Arnaud Deziel-Richer

(PdM) program is simple: to prevent catastrophic failures. These failures have negative effects by impacting machine availability, reducing production, maintenance costs, and thus decreasing overall plant profitability. An efficient PdM program can help mitigate these issues, and quantifying the potential savings is an important part of this to help justify investment in tools, training, manpower, etc.

This presentation will show the approach Laurentide Controls uses to help their clients achieve a quantifiable business approach using online Spartakus software, all while helping optimize the efficiency of their program. A few technical examples of vibration cases, from route-based data collection, problem detection, signal analysis and reporting will also be presented.

 

Accurate Condition Monitoring of Ultra-low and Low Speed Machines- Ron Kittle

HD ENV is a novel approach to the task of detecting gear and bearing deterioration in very early stages. By combining low noise hardware design and patented algorithms for digital signal processing with a standard vibration transducer (accelerometer), it is possible to extract relevant gear and bearing information from a noisy environment with exceptional clarity. Historically, gear and bearing damage detection using standard velocity readings (i.e. overall velocity values) could – in the best of cases – reveal severe damages in very late stages, thus resulting in very limited planning horizons. At best, a trend of increased velocity RMS values could be used to avoid unplanned stops.

Adding spectrum analysis based on velocity readings could reveal gear and bearing damages earlier than in the very late stages, but it was still a rather crude tool. When vibration enveloping was introduced several decades ago, it became possible to detect damages in earlier stages than before, and it then became relevant to talk about realistic pre warning times. With vibration enveloping, it was possible to extract information coming from gears or bearings even if the transducer signal was dominated by low frequency content typically originating from unbalance forces.

HD Technology (HD = High Definition) was introduced for the first time in 2010, when the SPM HD method (Shock Pulse Method High Definition) was launched. One of the goals of SPM HD was to detect bearing and gear damages on applications running at low or ultra-low rotational speeds (from 60 down to below 1 RPM). At these low RPMs, traditional vibration technologies were difficult – in most cases even impossible – to use with success, while SPM HD produced meaningful and generally excellent results. Since then, a large number of successful application cases utilizing the SPM HD method, especially low RPM applications, have been documented.

 

Computers in Vibration Analysis – The Past 50 Years and What’s Ahead.

Over the past 50 years, computers have changed from something that few people personally interacted
with, or knew much about, to becoming a pervasive part of everyday life. This has also occurred in the
field of vibration analysis. I’ll review some of the ideas, major challenges, accomplishments, and
changes that I’ve experienced while applying and using computers in my work as a vibration analyst from
the early 1970’s to present. Many vibration analysts got on board this journey at various points on this
timeline, and we have all arrived here in 2023 with much talk, both positive and negative, on the future.
With the advent of things like ChatGPT, and other applications of artificial intelligence affecting all
aspects of society, the impact in our world of machinery will certainly not be benign. What should we
expect? How do we deal with this? And how do we remain relevant and valuable as vibration analysts
and reliability engineers? Let’s take a look and do our best to prepare.

 

Louis Lavallée 2022 ATC Keynote address

Included in this presentation are 4 case studies:

1. Commissioning of a New Motor on a Hoffman Blower
   • An electrical contactor remains closed after starting the motor. This has the effect of leaving an undesirable circuit impedance.
2. High vibration readings from a mining main hoist
   • When gears are getting worn out, we can find sub harmonics of the gearmesh in the common factor.
3. Abnormal condition of the bearings of the recently installed motor of a hoist.
   • Wrong grease used in motor. Thicker grease causes the roller to slip on the bearing race instead of turning.
4. Small blower with pillow blocks, repetitive failures.
   • Wrong bearing used for this application.

 

An Infrared Camera Must Be Considered A Vital Maitenance Tool. – Paul Frisk

The basic intent of a well-designed maintenance program is to reduce the risk of premature failure
and insure the continued operations of components and/or assemblies. The success of the
maintenance system is based on the seamless integration of multiple diagnostic disciplines, of
which infrared scanning is definitely an integral part of. An infrared camera, along with a
properly trained thermographer, can determine the “current health/condition” of a component or
system that is being monitored. The camera provides vital information in a non-contact, non destructive real-time imagery methodology.
The infrared camera has become a vital diagnostic tool in the monitoring of mechanical,
electrical, and building systems. Long, costly downtimes can be reduced, if not illuminated. It is
the superior capabilities and features of an infrared camera that make it a “must” in any
maintenance program. This presentation will explore these features.

 

Wireless sensor technology- A New Era For Data Security

As wireless sensor technology begins to take the leading edge within the industrial internet of things community, a new era of data security has emerged that requires diligent thought and consideration on the part of end users, system integrators and key stake holders. Critical machine health and process data being transmitted wirelessly and hosted internally as well as externally creates an entirely new series of security concerns that must clearly be understood to maximize the value of the technology.

This presentation will focus on the key security tools available to end users to ensure the security of their data when deploying wireless sensor networks and hosting data internally as well as externally to their organizations.

 

The Electric Motors and Their Vibration

Most of the equipment that we monitor every day is driven by an electric motor. All these motors may look similar but, they are different. Each motor has been selected for a specific application. When looking inside the motor, we can see that the rotor and the stator are different from one motor to another one. This will modify the behavior of the motor. A motor design for driving a compressor will not necessarily fit for a water pump or a conveyor. Theses difference in their construction will have an important influence on their own vibration. In this presentation we will examine different types of motors and their vibration.

 

Primary Heat Transport pressurizing pump –commissioning problems Findings and resolution

This case study summarizes the problem of repeat thrust bearing failures encountered during the commissioning of the primary heat transport (PHT) pressurization pumps and the resolution of the issue.

The PHT pressurizing pumps is an Ingersoll Rand – HMTA, 10 stage pump designed with impeller suction facing the same direction creating a resultant thrust which is absorbed by the balance drum and thrust bearings. The pumps were initially commissioned in the 1970’s.

The PHT system is a closed loop that removes heat from the reactor fuel and transports to the boilers, the PHT pressurizing pumps is used to maintain the system pressure of the system.

U2 was in laid up state and had undergone a major refurbishment. During the pump start up of 2-33310-P2, the thrust bearing failed within 20 seconds.

 

WANTED – VIBRATION ANALYST

Personal thoughts on where we have been and where we are going with vibration analysis.

 

Examination of the FFT Batch Process With Calculation of the RMS Energy- Jack D. Peters

The Fast Fourier Transform (FFT) is used in vibration analysis. It is well known that Window
Filters (Hanning, Flat Top, etc.) can be applied to the time waveform during the batch processing
of the FFT, and as a result, decrease the resolution of the FFT. The resolution is decreased by a
numerical Window Factor based on the applied filter. It is not well known that the Window Factor
(WF) can also be described as the Equivalent Noise Bandwidth (ENBW) or Noise Power
Bandwidth. This paper will explain how to calculate the RMS Energy of the FFT when the WF or
ENBW used to process the FFT has a numerical value greater than one.

 

Added Mass Effect on the Dynamic Response of Structures – A Study on a Hydro Runner- Hassan Kazi, Neil Tugby, Alexey Koval

Any vibrating structure submerged in fluid experiences the opposing force of the fluid opposing
vibration. The effect of the fluid on structural dynamics is known as “added mass”. Runners of
hydroelectric turbine generators are subjected to various excitation mechanisms. The natural
frequencies and mode shapes of a runner are important parameters which determine its behavior
and response to these various excitations. Added mass effect lowers natural frequencies of a system
while submerged in water as compared to in air. This paper outlines the concept of added mass
and compares the natural frequencies of a runner in air versus water as calculated via Finite
Element Analysis (FEA). The FEA model was initially validated through experimental modal
analysis (EMA) performed on the runner removed from the turbine generator. FEA and EMA
results are compared and discussed.

 

Case study of a Power Turbine

A power turbine had been experiencing vibration trips during normal operation. During the event, a one-half (1/2X) vibration component emerged in the spectrum. This usually a good indication of that a light rubbing may have been developed at a seal area. Data analysis helped understand its vibration behavior and locate the rubbing area. The understanding was rather helpful for maintenance and operation teams going forward.

 

A Proven Approach to Condition Monitoring for Reciprocating Machinery

Traditional Vibration Analysis (VA) or Spectrum VA is widely utilized on rotating machinery in all types of industrial applications to diagnose and troubleshoot machinery issues. In conjunction with other technologies, VA allows predictive maintenance personnel to pinpoint machinery failures like unbalance, misalignment, bearing issues, etc. This diagnosis is completed by analyzing the vibration frequency spectrum of an event and its correlation to the machine and conditions. For reciprocating machinery, however, spectrum analysis is not the most effective tool for determining defects as the expected mechanical events and the failure modes are best identified in a time-based waveform and referenced to a known point on each cylinder such as Top Dead Center (TDC). In the reciprocating analysis world, this is known as crank angle-based data, which does not utilize the frequency spectrum, but rather examines events relative to crankshaft positions. By combining vibration in different frequency ranges with in-cylinder pressure data and utilizing basic thermodynamic and combustion principles, it is possible to determine defects in reciprocating machine equipment such as compressor cross head damage and cylinder leakage (valves, rings, and packing) as well as engine valve train and cylinder-related issues. This paper will provide an overview of engine and compressor analysis and explain how crank angle-based data can pinpoint issues as compared to traditional VA. A review of ISO Guidelines for reciprocating compressors will also be discussed.

Online vibration monitoring system selection and installation – trials, tribulations and successes

The selection and installation of an online vibration monitoring system can be a complicated task with many variables and potential problems to be aware of. Considerations include cost, availability of components and replacement parts, warranties, ease of installation, configuration and maintenance. The least or most expensive system may not be the ‘best’ for your reliably program goals, and those goals may not be clearly defined. This paper discusses some of the experiences of the authors’ observations over the last 20+ years of being involved with online vibration systems, including the more recent and increasingly popular wireless systems. Pricing, physical characteristics, long term considerations including maintenance and software evolution will be included in the discussion.

 

Hight Vibration on Hydroelectric Headgate Hoist During Commissioning

During commissioning of a new headgate hoist, high vibration levels were noted on the
break fan bearings during emergency drop. The vibration levels were significantly higher
than those measured during the factory acceptance test (FAT). In depth measurements
indicated higher than expected running speed during the emergency drop, leading to
excitation of shaft critical speed in additional to possible structural resonance. A detailed
analysis will be presented on the vibration measurements and the findings including
assembly issues of the entire hoist.

 

Pickering  Emergency Low Pressure Service Water (ELPSW) Pump Vibration Case-Study

There are 4 ELPSW vertical pump-motor sets per Unit (5/6/7/8-71310-P1/2/3/4) for a total of 16 across Pickering B units. Although the Pickering B ELPSW pumps were intended to provide backup cooling water flow, they are commonly used for continuous service with the unit at power.

There has been elevated vibration levels at the motor locations and this was addressed by a dynamic absorber mass installed at motor non-drive end to eliminate resonance at running speed. However, recently there has been increases in vibration levels at the motor locations that required further troubleshooting to determine the cause.

 

Hydro generator Vibration Troubleshooting Case Study

This paper follows the case study of troubleshooting elevated and unstable upper guide bearing
vibrations on a 120 MW Pelton hydro unit following a recent rotor major inspection. Inconsistent
responses during testing were observed based on the rate of change of turning speed during start up, bearing and stator temperatures, generator field excitation and therefore magnetic unbalance,
as well as generator active and reactive power loading. A single plane field balance procedure was
employed near the upper guide bearing to minimize turning speed frequency excitation forces at
this location. Additional testing was performed to confirm that vibration levels were successfully
reduced to within acceptable limits for normal operating regimes allowing for unrestricted release
to operations. However, this only addressed the symptoms and not the root cause which is believed
to be related to early indications of fitment issues, namely the generator rotor rim to spider due to
aging.

 

Detecting and Correcting the Roadblocks in Machinery Installation

Poor machinery installation practices is the biggest killer of machines 65%.
This includes:
Misalignment
Twisted/distorted bases
Softfoot/Distorted Foot Mountings
Imbalance
Static stress ie . pipe strain
Dynamic Stress ie . thermal growth
Coupling/shaft runout
Mechanical Looseness
Other
•Improper lubrication 20%
•Operational/Design 10%
•Other 5%

 

Performance Driven Engineering & The Digital Twin

The Industrial Evolution
Siemens has been at the forefront of every phase

Phase 1 – Mechanical Production
Phase 2 – Electrification
Phase 3 – Automation
Phase 4 – Industrie 4.0, Digitalization

 

Optical Encoder Applications for Vibration Analysis

The application and use of an incremental optical encoder to measure torsional
vibration or the instantaneous changes in machine speed will be discussed. Basic encoder
operation, conversion from frequency to voltage, and engineering units will be explained.
Illustrations and examples in the time waveform and FFT will provide additional understanding
for this technology

 

Reliable Assets are driving YOUR Business Results

The Business Case for Reliability (2 KPIs)
•Where are you VS the leaders in your industry (2 KPIs)
•The impact of a reliable plant on the share value
Evolution of condition Monitoring
•Evolution of condition monitoring since 1950’s
•Condition Based Monitoring is the cornerstone of a reliable plant
Condition Monitoring Must Integrate Information from Many Different Sources
•Breaking the silos of information
•Sending Relevant Data to the Appropriate Persona
Asset Health Information to Reduce Operating Risk

 

Evaluate your current performance by comparing it to the best performers in your industry.

• Benchmarking & KPI Development
• Developing ROI – Establishing where a company or facility stands among the pacesetters in their industry
• Emerson’s “Benchmarking System” was developed over 9 years of analysis of published & private survey data from sources such as:
  –SMRP – CMA
  –Townsend – Solomon
  –AISE – SAE
  –PIMA – TAPPI
  –EPRI – AT Kearny
• 4 Quartiles of Performance
• Benchmarks for 11 different industries
• Standards of excellence that provide a comparison

The Importance of Standards

If you are involved with Maintenance and
Reliability, MAAD is a method or process you are
probably already following right now.

It is a an acronym we developed that stands for
Measure, Analyze, Act and Document and they
are all equally important during a measurement
process.

This is something we recommend that you be
doing throughout your condition monitoring
program, or for any type of measurement.

 

ADDRESSING LOW PRESSURE STEAM TURBINE BLADE
RESONANCE CONCERN THROUGH EXPERIMENTAL MODAL
ANALYSIS, FINITE ELEMENT ANALYSIS, AND ROTOR DYNAMIC
ANALYSIS

A study was conducted on a low pressure (LP) steam turbine last stage (L-0) blades to determine
if the free-standing blades were susceptible to any resonance conditions. The study was based on
in-situ Experimental Modal Analysis (EMA) of the blades, Finite Element Analysis (FEA), and
Rotor Dynamic Analysis (RDA) of the turbine-generator (T-G) train. This paper presents the
results of such study

 

Monitoring of Uneven Magnetic Pull (UMP) for Controlling Vibration of Rotating Machinery

Monitoring of Uneven Magnetic Pull (UMP) for Controlling Vibration of Rotating Machinery

 

Balancing IIoT with Predictive
Maintenance Programs

 How remote monitoring integrates with route-based vibration monitoring
 Case study:
 How remote monitoring was used for a troubled asset
 How multiple assets can be covered using remote monitoring
 How Koontz Wagner helped their customer achieve 53 days of extra uptime with a troubled asset
 How to use remote monitoring and alarms to know when to act
 Where to start a remote monitoring program in your facility

 

Strain Gauge Testing for Various Applications

A Strain gauge is a sensor whose resistance varies with applied
force; It converts force, pressure, tension, weight, etc., into a
change in electrical resistance which can then be measured. …
Thus, strain gauges can be used to pick up expansion as well as
contraction.

 

Current and voltage monitoring

Current and voltage
monitoring

 

Vibration Suppression Case Study With the Aid of Motion Amplification

Vibration Suppression Case Study With the Aid of Motion Amplification

 

New hydroelectric unit trips on high vibration during cold start-up

New hydroelectric unit trips on high vibration during cold start-up

 

Evolution of IIoT & Condition Monitoring

The industrial internet of things (IIoT) is the use of smart sensors and actuators to enhance manufacturing and industrial processes. Also known as the industrial internet or Industry 4.0, IIoT leverages the power of smart machines and real-time analytics to take advantage of the data that dumb machines have produced in industrial settings for years. The driving philosophy behind IIoT is that smart machines are not only better than humans at capturing and analyzing data in real time, they are better at communicating important information that can be used to drive business decisions faster and more accurately.

 

Identification and Evaluation of Rolling Element Bearing Failures Using Fluid, Filter and Material Analysis Techniques

•50-80% of rolling element bearing failures related to lubrication issues
•Variety of common fluid, filter and material analysis techniques available; however limitations on sensitivity to fluid condition, fluid contamination and wear debris exist
•Implementation of a fluid, filter and material analysis program has been proven to:
•Aid in identifying conditions leading to rolling element bearing failure
•Aid in early identification of rolling element bearing failures
•Successful implementation dependent on knowledge of rolling element bearing failure modes, along with capabilities of measurement technique

 

Fluorescence Spectroscopy for Online Condition Monitoring of Machinery Lubricants

Oil Condition Monitoring
Fluorescence Spectroscopy
Test Approach and Results

 

VIBRATION CHARACTERISTICS OF THERMALLY CYCLED GRAPHENE NANOPLATELET (GNP) REINFORCED 3D-FIBER METAL LAMINATES (3D-FML)

Harsh environmental conditions may cause materials to degrade and eventually fail, or even worse,
it can be coupled with undesirable vibrations in mechanical systems, resulting in premature failure
of the system. Such combined loading scenarios are often encountered by transport vehicles (i.e.,
airplane cabins, and train and automobile components). Today, fiber metal laminates (FMLs) and
sandwich composites are often used in the fabrication of various components of transport vehicles.
Therefore, it is of paramount importance to study the static and dynamic characteristics of such
materials under combined loading scenarios and ensure their durability and safety. A recently
introduced class of 3D fiber metal laminate (3D-FML) in our research group has shown exemplary
mechanical response characteristics; however, the vibration characteristic of this novel hybrid
material system under harsh environmental conditions has not been studied. Therefore, exploring
the effect of environmental parameters on the frequency response of this class of materials shapes
the main objective of this research. Specifically, the main goals of this research are to characterize
and understand the frequency response of 3D-FMLs under thermal fatigue and attempt to improve
their vibration response by incorporation of an effective solution. To do so, 3D-FMLs specimens
are exposed to combined thermal and humidity cycles. Subsequently, the vibration characteristics
of the system are experimentally evaluated. An attempt is also made to improve the damping
characteristics of the material system by incorporation of graphene nanoplatelet within
the interface layers of the hybrid system. It is also demonstrated that recently developed
nondestructive techniques can be effectively used to assess the influence of environmental
conditions on the static and dynamic behavior of 3D-FMLs and evaluate their potential degradation
under thermal fatigue.

 

Case Studies in Vibration Diagnostics and Correction

There are many techniques available for diagnosing probable root-cause of vibration that
adversely affects the reliability of an asset, including time waveform and frequency analysis,
natural frequency testing, operating deflection shape (ODS), vibration video amplification
(VVA), and finite element analysis (FEA). Once the source of a vibration problem has been
diagnosed, a Corrective Action Plan must be developed and implemented. Vibration control
methods include force reduction/elimination, resonance tuning, damping and dynamic vibration
absorbers. Case studies are used to illustrate the use of these diagnostic and control methods in
reducing vibration, increasing fatigue life, and increasing the reliability of mechanical equipment
and structural supporting systems.

 

Motion Amplification: Innovations in Shaft Rpm, Runout and Inspection with case studies

Technology Overview
• Measure movement not
visible to the human eye.
• Technology turns every
pixel in the camera’s view
into a sensor
• The results lend
themselves to a
visualization of the motion.
• We can measure and
quantify any structure or
assets that a camera can
see.

 

SOLVING THE DIRICHLET PROBLEM FOR VIBRATION OF PARALLELOGRAM-SHAPED MEMBRANE USING METHOD OF PARTIAL DOMAINS

In this study, the Dirichlet boundary problem for vibration of a parallelogram-shaped membrane
is solved. The simplicity and transparency of the proposed procedures allow one to clarify the
specific features of some state-of-the-art approaches to solve similar problems of mathematical
physics. For many types of domains, including a wide range of non-canonical ones, the use of the
concept of a general solution of the boundary value problem makes it possible to construct a
numerical-analytical solution to the problem. In this case, sets of partial solutions for the basic
equations of mathematical physics are used. The main idea is to indicate effective ways to
determine arbitrary coefficients and functions that are part of a general solution. The conventional
approach for deriving numerical-analytical solutions is used based on the mean square deviation
minimization and collocation methods.

 

EFFECT OF BOUNDARY FORM DISTURBANCES ON THE FREQUENCY RESPONSE OF PLANAR VIBRATIONS OF PIEZOCERAMIC PLATES. EXPERIMENTAL INVESTIGATION

Experimental results for forced planar vibrations of parallelogram-shaped piezoceramic plates are
presented. The concept of this study is to evaluate the potentials of controlling the spectrum of
natural frequencies and electromechanical coupling coefficients of plates by changing their shape.
The results permit of supporting the data on analytical and numerical investigations of dynamics of
piezoceramic plates and establishing the consistency between the physical properties of a real plate
and the assumptions of the ideal computational model in the solution of practical problems.
Comparison of calculated and experimental data for the spectrum of natural frequencies of the plate
over their rather wide range can demonstrate this consistency. The experimental procedure was
tested in studying the vibration behavior of SM111 ceramic square and parallelogram-shaped
plates with different side slopes. The frequency range of investigations is limited from above with
140 kHz, which provides effective excitation of a sufficient number of natural vibrations. The
structure of an experimental complex and excitation mode of vibrations at actual values of the
quality factor permit of considering the external voltage source as the infinite power one. The
excitation of asymmetric vibration modes on the change in geometry of a rectangular plate is
natural. As was shown, high-order modes (very low electromechanical coupling coefficients in
rectangular plates) can be effectively excited in parallelogram-shaped plates with maintaining a
uniform electrode coating. It needs the traditional estimates of electromechanical coupling coefficients
in piezoelectric plates to be refined with regard to inhomogeneous stress and strain fields.

 

Large Synchronous Electric Motor

It is one of the first electric motor with alternating current.
It was patented in 1888 by Nikola Tesla.
These motors are generally used in heavy industry
mainly in the mining to power ball mills and crusher. In
refineries for reciprocal compressors. It is also used for
electricity generation around the world.
These high-powered motor have a very large torque
even at low speeds. It eliminates the use of speed
reducer.
It is also used to maintain the power factor of a plant. It
is then called synchronous compensator.
This motor requires a complex start-up system.
It has a unique speed and no slip. It can work with a
VFD with modifications.
Its stator is powered by AC current and CC for the rotor.

 

Condition Monitoring of Deep Draft Vertical Centrifugal Pumps

Brief overview of general pump components
•Considerations for Condition Monitoring
•Considerations for Online Monitoring with respect to Vibration Analysis
•Case Study 1 – RSW Pump Shaft Failure
•Case Study 2 – CW Pump Suspected Impeller Rub

 

Case Histories Low speed dryer bearing analysis DC motor bearing problems

We use vibration to detect low frequency problems such as unbalance, misalignment and looseness.
We use ultrasound to detect high frequency problems such as air leaks, lubrication issues, and steam traps.
When used together, they complement themselves.
The following two case histories demonstrates their effectiveness when used together.

 

Rotor Bar Failures in Induction Motors

As a general rule, motors below 200 HP are limited by stator design
and above 200 HP by rotor design. That is to say if a motor smaller
than 200 HP is stalled the stator will fail before than the rotor.
Designers will often build larger motors with a copper bars, however
due to the added manufacturing cost aluminum bars are becoming
more common in larger motors. In this situation, one must rely on
motor protection to preserve the rotor.

 

How to Balance IIoT Systems with Existing Predictive Maintenance Programs

Condition monitoring based on industrial Internet of things (IIoT) networked sensors can greatly improve operational efficiency, increasing productivity and reducing catastrophic failures. Many maintenance departments would love to switch from route-based readings to IIoT condition monitoring. The problem is that most companies have hundreds, if not thousands of assets to track, far more than they could possibly afford to equip with IIoT sensors. How do they gain the benefits of IIoT condition monitoring without excessive capital outlay? The answer is by not replacing their existing route-based monitoring programs but by augmenting them with strategically installed IIoT sensors. This hybrid approach places IIoT condition monitors where they provide the greatest increase in productivity while maintaining the benefits of existing route-based programs and expertise.
Learn how the two approaches complement each other, techniques for succeeding with IIoT systems like online condition monitoring, and how to start a pilot program that will demonstrate the benefits of the system to your organization.

 

NOT ALL PROBLEMS ROTATE – USING ULTRASOUND TO ENHANCE YOUR PREDICTIVE PROGRAMME

The use of contact and airborne ultrasound as a predictive maintenance tool has grown steadily
over the course of the last two decades.
It has its supporters – people who admire the simplicity of the technique.
It also has its detractors – people who say that the technology lacks the discipline of vibration in
terms of a route-based structure and diagnostic capabilities.
This presentation explores the ways in which modern ultrasonic technology can square the circle
of maintaining simplicity for those who need it while at the same time providing sophistication
for those that want it

 

Review of API 617 8th Edition Dynamics

API 617 8th Edition Dynamics

API 612 Dynamics

API 684 Task Force

 

Application of squeeze-film dampers to a large centrifugal compressor – Technical paper

Application of squeeze-film dampers to a large centrifugal compressor

 

Induction Motor Testing and Evaluation

As energy costs rise, more emphasis is being placed on determining the health of large inductive
motors.
Motor Current Monitoring and Analysis (MCSA) is a straight forward tool to diagnosing problems
with
large inductive motors. This technique along with standard vibration analysis, voltage monitoring,
and temperature monitoring provides a complete diagnostic perspective of motor health and
condition,
power consumption, and overall efficiency.

 

Optimizing Lubrication Film Thickness in Rolling Element Bearings

Typically there are two options of maintenance concerning bearings, one is to lubricate them the
other is to change them. Monitoring bearing condition is critical to insure reliability. The
equipment in your plant is an asset that must be managed and prolonging its life will insure a
positive contribution to your plants operating efficiency. By incorporating a condition monitoring program that involves monitoring both equipment condition and bearing lubrication
film thickness, issues such as secondary damage and excessive operating costs are avoided.
The following paper will identify some of the condition-monitoring methods used today. Factors
that affect the quality of the film thickness will be discussed followed by real life case studies.
The case studies will present issues that are common in all industries followed by solutions.

 

Variable Frequency Drive and Rotor Resonance Case Study

A newly installed motor indicated a 1980 Hz fault. The fault was not a known bearing fault
frequency, not related to operating speed, and not a multiple of line frequency. The installation
did not have a loose base or soft foot condition. Upon further investigation, the default switching
frequency for the variable frequency drive which is associated with that motor was determined to
be 2000 Hz. Tests were conducted where the switching frequency was varied and vibration was
recorded. Results were conclusive, the switching frequency of the variable frequency drive was
responsible for resonant amplification of the motor rotor.

 

Applications for Energy Savings and Reliability Improvement using Infrared Thermography

Justification of infrared programs

Electrical Applications

Mechanical Applications

Building Envelope Applications

Other applications

Infrared 101

 

How Vibration Analysis Works – The Importance of Trending

This paper begins with the energy being put into a piece of rotating machinery and
ends at the vibration graph displayed on the computer screen, taking into account each
step this energy passes through from start to finish. We begin with inputs such as
speed and load, the rotating shaft, the other sources of forcing frequencies, their
journey from component to component, through the shaft, the bearings, the sensor
mounting, the sensor, the electronics of the data collector, the filter and data collection
setups etc. until they result in a piece of data that is ready for analysis. This paper will
then posit that the data one analyzes at this last step may in fact be nearly meaningless
if all the variables along the way are not controlled from test to test and the data
trended. Ever wonder why sometimes the machine with really high vibration levels
rarely fails but the one with low levels does? If you or someone you know has had bad
luck with a vibration analysis program, this paper may explain why and describe an
easier route to success.

 

Vibration Mythologies

Usually the word “myth” or “mythologies” refers to beliefs that seem to be perfectly true or
immutable. Although machinery vibration understanding is not a religion, it certainly has its beliefs that are usually true, but also beliefs that the writer has found to be “not true.” Those that are strongly held and not too often questioned, are by the writer called “mythologies” – vibration related. This presentation is not based on a play with words. Instead, the myths to be questioned were chosen, based on the harm it creates for those trying to either solve machinery vibration-related problems or attempts towards greater machinery reliability and improvement

 

Telemonitoring of Wind Turbines

Condition-based maintenance on wind turbines not only involves maintenance, but also
encompasses servicing, inspection, measurement and evaluation of the current condition of the
unit. As a condition-based maintenance tool, Condition Monitoring is a component of long-term
service packages offered by some wind turbine vendors and essential for operating offshore wind
farms. Several thousand wind turbines are presently equipped with Condition Monitoring
systems (CMSs). CMSs record the running and operating conditions of a wind
Turbine and send the measurement data to a certified monitoring center, e.g. as an eMail. The
center monitors changes in the running and operating behaviour of the unit (TeleMonitoring,
Level 1), identifies the causes of changes (TeleDiagnosis, Level 2), makes statements on the
machine condition (Level 3), and looks for opportunities for improvement.

 

TROUBLE-SHOOTING BEARINGS AND GEARS

Vibration generated from rolling element bearings and gears can lead to complex signals which sometimes can be masked by several other machine components, processes or operating conditions in the machine. This can obscure their detection and diagnostic, hence the need sometimes for more advanced methods of analysis. In this paper, many such cases will be presented, taken mainly from rolling-mills in the steel industry and the mining and transportation industries. A comprehensive summary of bearing fault detection and diagnosis will be discussed in line with upcoming ISO standards on the diagnostic methods for rolling element bearings.

 

Understanding Electrically Induced Vibrations in Electric Motors

Understanding Electrically Induced Vibrations in Electric Motors

 

Paper Winder Rider Roll Problem

Paper Winder Rider Roll Problem

 

Application of squeeze-film dampers to a large centrifugal compressor 

Application of squeeze-film dampers to a large centrifugal compressor

 

TIME WAVE ANALYSIS MINI COURSE

Analysis of the time wave form is often critical to the identification
of certain classes of problems. Analysis of the spectrum is common, whereas
looking at the time based plots, which was common practice in the past, has at
times not been emphasized as a technique for the identification of problems.
Spectrum analysis works well, but viewing and studying time waves adds another
dimension to the analysis process. The identification of rubs, looseness, beats,
modulation and in particular impacts can be improved significantly by viewing
time based data. Looking for the presence of multiple impacts when performing
resonance testing, the presence of leakage or visualization of what the
application of widows does to the data absolutely requires the analyst to look at
the data in the time domain. The determination of damping through the use of the
log decrement calculation provides a method of accurately computing the
damping ratio. In addition, viewing the decay of the response of a resonance
allows the analyst to get a true feel for what damping actually represents.
The purpose of this course is to revisit the techniques that can be used in
the study of time waveform as they relate to determining the presence of
particular equipment problems, structural response issues or digital processing
anomalies.

 

TWO TECHNEQUES FOR AUTOMATIC FAULT DIAGNOSIS OF ROLLING ELEMENT BEARING

Envelope analysis is popular and effective for bearing fault diagnosis. Traditionally, the frequency band
enclosing a structural resonance is selected manually for envelope analysis. In this paper, a method determining this band automatically is developed. Wavelet packet transform is applied to decompose bearing signal into different frequency bands with equal bandwidth. RMS values of these bands are calculated and the band with the biggest RMS is picked up for envelope analysis. Further, cepstrum is used to process modulating signal to acquire bearing fault signature automatically. Experimental results confirm the satisfactory performance of these two techniques.

 

Vibration monitoring of wind turbines

What is the ideal scenario for vibration monitoring?

Review the technical challenges related to WTGs

Variable speed machines

Bearing faults

Gearbox faults

Resonance

 

From condition monitoring to condition management

Reactive maintenance

Preventive maintenance

Traditional condition monitoring. What is it? What is it missing?

Two steps to deliver greater value

Going further – improving reliability

Going further still – defect elimination

The roadmap to complete reliability.  A quick walk through the roadmap

NOTE: We are dealing with the very important discussion of reliability improvement through defect elimination inside-out

Condition based maintenance is a key part of a maintenance cost reduction, downtime reduction, safety improvement program.

But it is just one part! And it does not improve reliability!

We will explore how to improve your condition monitoring program, then how to take advantage of CM skills to extend machine life, and then how to implement a defect elimination program

 

Bearing fault detection and prevention

Why do bearings fail?

How do we know if they are failing? Simple and advanced techniques.

How do we prevent them from failing? Precision maintenance techniques.

 

NEW TECHNOLOGY KEEPS THE ASSETS RUNNING AT ENMAX

The volatile and ever changing market puts more stress on increasing production and decreasing
maintenance costs. As today is more stringent than ever to have good performing assets, every
company strives to achieve better results than did in the past.
World class competitiveness is required to set you above the rest but this is not achieved easily.
Often a good start can continue into failure if the program is not followed through and not been
able to see and identify the benefits.
Like many companies out there, Enmax looked at what can be done to improve the asset
reliability and thus reducing costs of operation and maintenance. Predictive technologies come to
mind immediately as being a successful tool used by the world-class companies proving their
effectiveness. However the wide spread usage does not set-up you for success immediately after
a new predictive tool is implemented.

 

STRUCTURAL DYNAMIC EFFECTS ON THE VIBRATION & RELIABILITY OF MACHINERY

The level of care extended to the specification, design and manufacture of mechanical equipment
is rarely matched in the design of the structural support system. For machinery that is critical to
plant operation, detailed specifications are written to insure the quality of the design of the
machinery. Inspections are made during the manufacturing stage to insure compliance with the
specifications. However, the design of the structural systems that support the machinery is generally
less scrutinized. This can result in a structural support system that is too flexible or resonant and can
lead to a machine that operates at an excessive vibration level, thus, adverselyaffecting the reliability
of the machine .
This paper deals with the dynamic response characteristics of the major types of supporting systems
including:
* Machines on Rigid Concrete Foundations
* Machines on Flexible Concrete Structures
* Machines on Elastic Metal Frames
* Machines on Isolation Springs
The design requirements for each type of support system are discussed. Case Histories are presented
to illustrate problems that occurif the supporting system is not designed properly. General Rules-of Thumb are presented that provide initial evaluation criteria relative to structural dynamic adequacy.

 

OPERATING DEFLECTION SHAPES PRINCIPLES, TEST PROCEDURES & CASE STUDIES

Operating deflection shape (ODS) analysis is a vibration testing and analysis procedure that is
capable of producing animations of the deformation characteristics of a vibratingmechanical system
at any discrete frequency. The ODS analysis provides information regarding movement during
operation that can be made into an animation. The animations can be extremely helpful in defining
areas of structural weakness or identifying areas of mechanical “looseness”. In cases of resonant
excitation, the operating deflection shape animation will provide an estimate of the mode shape for
the natural frequency that is being excited. A general overview of ODS testing techniques, analyzer
set-up and model development is presented along with case studies to illustrate the benefits of
operating deflection shape animations in root-cause vibration analysis.

 

A TESTIMONIAL ON THE ADJUSTMENT OF TREND ALARMS

In many cases, the alarm levels for the trends in a vibration route are not adjusted past some
standard default values. This testimonial shows one method to get this done and the benefits of
having site-specific alarms.
The method shows how to group similar machines and measurement points, examine the
historical data and make a stab at good alarm levels while keeping the process efficient and not
too time-consuming. Finally, the alarms need to be maintained, refined and kept up-to-date.

 

 

RESONANCE – MACHINERY ROCK & ROLL

VIBRATION MONITORING & ANALYSIS IS RECOGNIZED AS A KEY COMPONENT OF A WELL-FOUND RCM (Reliability Centered Maintenance) PROGRAM. MACHINERY HEALTH AND LONG-TERM RELIABILITY IS INTERPOLATED FROM TRENDS IN VIBRATION AMPLITUDE, HOWEVER, OFTEN THESE LEVELS INCREASE TO DANGEROUSLY HIGH VALUES WITH LITTLE OR NO WARNING! RESONANCE IS FREQUENTLY IDENTIFIED AS THE ROOT CAUSE, AND UNDERSTANDING THE PHYSICS OF NATURAL FREQUENCY, AND THE TOOLS AND METHODS USED TO RECOGNIZE AND CONFIRM A RESONANT CONDITION ARE ESSENTIAL SKILLS FOR THE VIBRATION ANALYST.

 

Multi-plane, Multi-speed, Dynamic Balancing of a Multi-stage High Speed Pump

This paper illustrates in a practical non-mathematical manner, important aspects
of vibration analysis and resonance. The paper is based on work done in 1978, using a soft bearing
balance stand with seismic velocity transducers, single plane tracking filter, X-Y plotter, and shaft
stick. Today, such balancing is generally done using multi-plane computerized instrumentation, in a
high-speed, vacuum “balance pit”. Topics include:
• Mode shape, Resonant speed, Critical speed – examples
• Operating Deflection Shape – at speeds other than resonance
• Bearing stiffness – effect on the orbit
• Amplification factor – a practical example
• Phase relationship – force vs. response at various speeds
• Phase measured at the bearings:
o Dynamic imbalance
o Static imbalance
o Quasi-static imbalance
The paper discusses the usefulness of these concepts.
Data is derived from work done balancing long, slender shafted, 3570-rpm, motor driven, multi-stage
pumps, which operate above first bending mode critical.

 

Noise Emission Study of Small Wind Turbine Structure using Operational Modal Analysis and Wave Equation

A major barrier to the acceptance of small wind turbines is that they are perceived to be noisy particularly
when mounted on monopole towers rather than traditional guy-wired ones. Noise emission from a 2.4kW downwind turbine due to its 10.2m monopole tower was investigated. Tower vibration was measured using 24 accelerometers. A finite-element tower model combined with simple assumptions for the turbine and wind loads allowed the noise to be obtained from solution of the wave equation. The measured vibration levels were matched to the tower model amplitudes. Sound pressure level produced by the fluid-structure interaction reached 30dB at about 11m from the tower and decreased to 5dB one kilometer away. Propagation switched from cylindrical to hemispherical when the distance was about 200 times larger than the tower height.

 

Dynamic Analysis of Compressors and Supporting Structure

Liquid Zone Control (LZC) compressors were experiencing high levels of vibration.

Asked to re-visit the design of the compressors and the supporting structure due to ongoing operation and maintenance issues. These compressors exhibited high vibration levels.

 

UNDERSTANDING VIBRATION PROPERTIES OF A PLANETARY GEAR SET FOR FAULT DETECTION

This paper investigates the vibration properties of a planetary gear set in a dynamic view. An
improved two-dimensional lumped mass model is used to simulate the vibration signals of a
planetary gear set in the sound or crack situation. Through dynamic simulation, the vibration
signals of each individual component are obtained, such as the acceleration of the sun gear,
planet gear. By incorporating the effect of the transmission path, resultant vibration signals of the
gearbox at the sensor location are acquired. Results show obvious fault symptoms in the signals
of the individual components. After going through the transmission path, the fault symptom
attenuates and reveals new patterns. A bigger increase of the signal energy in some mesh periods
is observed when the crack tooth is in meshing. Based on this finding, one indicator is proposed
to detect the crack fault. The performance of this indicator is experimentally validated.

 

Vibratory cavitation erosion monitoring of hydraulic turbines

Introduction on cavitation erosion.

Historical review of vibratory cavitation detection system

Data transfer and cumulative erosion calculation

Degradation data base of the turbine

Cavitation erosion modeling

 

Optimizing low speed, low amplitude vibration measurements:
A comparison of 100 mV/g and 500 mV/g accelerometers

A comparison of 100 mV/g and 500 mV/g accelerometers.

 

Wonderful World of Vibration Analysis

The predictive maintenance industry was created in order to meet the need to keep these vital machines in operation. Vibration specialists are the doctors and thus the keepers of the large machines that make modern life possible.

 

Full Spectrum Analysis

Don Bently was responsible for the “…development and commercialization of full spectrum data
presentation format, showing forward and reverse precession components…” as stated on the Bently
Pressurized Bearing web site (http://www.bpb-co.com). The data format is a standard display used by
many vibration analysts to evaluate data captured from a pair of orthogonal probes.
Although the information in the plot is informative and helpful in evaluating some machinery faults, it
can also be difficult to interpret and apply without full understanding of the physical characteristics that
the plot represents. It is also is sensitive to probe orientation and rotation direction configuration, so
that improper setup of the plot can result in very misleading results. With good understanding of the
meaning of the plot display, full spectrum analysis can be helpful in analyzing a variety of different
machinery faults.

 

Wind Turbine Blade Flapwise Vibration Control through Input Shaping

The wind turbine blade vibration is a serious problem not only because it reduces the life span of blades,
it can also pass undesirable disturbance frequencies to the tower, which causes tower to vibrate. The aim
of this paper is to develop a model for wind turbine flapwise vibration and reduce blade vibration caused
by pitching command. Lagrange’s method is used to establish the governing equations and input shaping
method is used to reduce the residual vibrations caused by the change of pitch angle input. The model we
developed is compared with the model in FAST and the effectiveness of input shaper is verified by
comparing the response of the model with input shaper and without input shaper.

 

Generator Compromise Balancing for Thermal Sensitivity due to Rotor Shorted Turns

Generator Compromise Balancing for Thermal Sensitivity due to Rotor Shorted Turns

 

OVERALL VIBRATIONS: HISTORY AND PRESENT DAY USES

The history of overall vibration measurements in North America and Europe goes back to the
1950s. Over the decades, there have been many misunderstandings related to this subject. The
sources of the misunderstanding will be described.
Currently, there is a trend to try to use overall vibration measurements for screening vibrations in
selected areas, such as reciprocating compressors and piping. One such guideline has been
developed and published by the European Forum for Reciprocating Compressors (EFRC). It will
soon be an ISO Standard.
A new standard for high speed reciprocating compressors is nearing completion, and will be
discussed. It will also provide guidance for using overall vibrations as a screening tool

 

Wireless Monitoring of Critical Assets

Wireless condition monitoring for critical assets can play an important role in
plant management. In Section (1), this paper explores the practical issues
surrounding the use of wireless sensors by reviewing the types of wireless sensors
and standards available, and by considering range, power, bandwidth, capacity
and security. 900MHz wireless is shown to have strong advantages in certain
areas, particularly range. In Section (2), a field test is described where multiple
sensors are deployed throughout a large industrial facility and used to monitor
assets. The results of this test demonstrate the practical aspects of installing and
maintaining a wireless monitoring network, and the advantages of operating the
system.

 

HELICOPTER TAIL ROTOR SMOOTHING

Tail rotor smoothing is preformed on helicopters to reduce vibrations of the airframe
induced by slight imbalance of the tail rotor assembly. These vibrations are a leading
cause of structural fatigue and also induce increased wear on the rotating components of
the tail rotor and associated drive train. We will examine the case history of CH124 Sea
King helicopter 124412, which reveals what can go wrong with a fairly basic and well
documented procedure. Numerous problems were encountered such as equipment
failure, incorrect assumptions, crew changes and poor inspection procedures. Success
was eventually achieved and many lessons were learned through the mistakes that were
made. This case history is used to train new personnel and will hopefully prevent these
same errors from happening again and reduce any delays when performing tail rotor
smoothing.

 

Development of a Physics-based Model for Machine Condition Monitoring

Condition monitoring of rotating and reciprocating equipment is an important means of ensuring
the long-term health and optimal operation of these types of machinery. Many current condition
monitoring systems use what may be described as a “data-driven model” to create a performance
model for the machinery. In other words, the real machinery will be run over the widest possible
range of performance conditions, while sensors are used to pick up various outputs such as RPM,
cylinder pressures, temperatures and vibration levels. This data is then processed to create a map
of the expected normal sensor outputs for a given performance condition.
This method of condition monitoring has some shortcomings when it comes to providing a
predictive model of the machinery being monitored. One disadvantage is that creation of a datadriven model requires a significant amount of time to work directly on the equipment to cover
the full operating range. If a part of the machine is modified, such as the replacement of an
existing cylinder with a different-sized one, the process would have to be repeated for the new
configuration, resulting in further machine down-time. In addition, the data-driven model cannot
be used to predict the expected operating condition of the machinery under various faults, since
attempting to do so by re-creating faults in the machine and then running it would likely damage
the equipment.
The development of “physics-based models” is aimed to the solution of these shortcomings that
data-driven models have. The idea behind a physics-based model is simply to use the values of
certain key input variables such as inlet conditions, run speed, and geometry, to predict the
expected machine operating parameters using physical laws. These may include principles of
mechanical motion, thermo-fluid dynamics, electro-magnetics and others.
In this paper, we will present the concept of physics based monitoring and the challenges
presented by its practical implementation. We also present a preliminary thermodynamic
compressor model which is been used in the condition monitoring of a test unit. Additionally, a
mechanical model of a recip compressor system using the bond graph modeling method is
described following the work of Mollasalehi et al. [1] is . We expect that a physics-based model
will allow for more flexibility in the prediction of machine performance, which will include both
the ability to make predictions for a larger range of machine parameters and conditions, and the
modeling of failure scenarios, without requiring lengthy periods of testing on the equipment.

 

VFD Induced Torque Pulsations Cause of Mine Exhaust Fan Coupling Failures

After their start-up in 2008, the two mine exhaust fans at Vale’s Coleman Mine experienced a
history of unexplained vibration problems. The fans in question were 2,600 kW (3,500 hp)
centrifugal double inlet design and controlled by variable frequency drives (VFDs). The
vibration problems culminated in the catastrophic failure of the disc pack spacer coupling on one
of the fans. Initial investigations into the root cause of the vibration problems were unsuccessful.
A theoretical analysis of the drive train at the design stage had identified torsional natural
frequencies in the system; however, these were not deemed problematic since it was believed
that they would not be excited during operation by the torque oscillations that are normally
associated with VFDs.
Using wireless strain gauge technology in situ, the excitation of a torsional natural frequency
above fan running speed was identified as the root cause of the failure. Strain gauge testing
demonstrated that very low amplitude inter-harmonic torque oscillations generated by the VFDs
were exciting the lowest torsional natural frequency of the drive train during fan speed changes.
As a result of the analysis, the fan vendor proposed larger couplings, which have been installed,
and modifications to the fan shaft keyway. These changes show promise for resolving the
coupling failure problem.
This technical paper discusses the steps that were taken during the investigation into the
problem. This includes the site testing, the analysis of the data and the analysis of the remedial
options that became identified. The paper concludes with recommendations concerning the
approach that should be taken on similar projects to ensure that this type of problem is avoided.

 

Rotating Equipment Torsional Vibration Concepts & Applications

1.General Concepts: Torsion, Torsional Vibration & Twist; Torsion in Rotating Machines; Free & Forced Torsional Vibration, Torsional Stress, Static Torque.
2.Free Undamped Torsional Vibration
3.Torsional Natural Frequency Calculations
4.Shaft Line Torsional Modeling
5.Torsional Natural frequencies & Mode Shapes
6.Torsional Modal Stresses
7.Frequency Interference (Campbell) Diagram
8.Torsional Damping
9.Steady State Torsional Excitations
10.Static Torsional Response Analysis

11.Steady State Torsional Forced Response Analysis
12.Transient Torsional Excitations
13.Transient Torsional Analysis
14.Shaft Stresses
15.Fatigue Failure in Shaft
16.Shaft Cracks Due to Torsion
17.Torque Measurements
18.Torsional Vibration Measurements
19.Torsional Vibration Measurement Techniques
20.Shaft Encoding Method Samples
21.Differences Between Torsional & Lateral Vibrations

 

Orbit and Shaft Centerline Analysis on Turbomachinery

Critical Rotating Machinery and Fluid-Film Bearing Review
The Orbit – Definition and Construction
Orbit Information
Average Shaft Centerline – Definition and Construction
Shaft Centerline Information
Correlating Orbits and Shaft Centerlines

 

Blade Tip Clearance Monitoring

The sixteen unit hydroelectric generating station, opened in 1958, has a capacity of 1,045 MW. This
run-of-the river station is one of the most inexpensive power producers in North America. The station
successfully completed a major rehabilitation program of the generating equipment and powerhouse
in 2002. The concrete powerhouse experiences the effects of concrete expansion due to alkali
aggregate reaction (AAR) that has impacted operation of the generating units. A number of actions
have been implemented to mitigate the effects of concrete expansion including the installation of an
online air gap monitoring system. This system was expanded during the major rehabilitation program
with an additional monitoring system.
In 2009, Unit 1 was removed from service due to an unusual noise emanating from the scroll case.
The resulting inspection revealed damage to the throat ring liner and runner blades. An assessment
of the Fast Fourier Transform (FFT) plots revealed a substantial increase in the displacement at the
runner blade frequency. A blade tip monitoring system was added, in order to continuously monitor
runner blade / throat ring liner clearances.
This paper discusses the repairs to Unit 1, vibration results, installation of the blade tip monitoring
system, and how valuable the collected information is when verifying generating unit integrity under
all operating conditions.

 

Unusual Case Histories

Unusual Case Histories

 

Compressor Case Histories

Large centrifugal compressors that are utilized in the process of producing
compressed gases or liquid nitrogen, oxygen and argon are located all over the world.
There are thousands of these large compressors in operation. These machines are unique
in design and thus have some interesting problems. This paper presents some case
histories of problems that can occur in this category of rotating equipment. These cases
illustrate how advanced analysis equipment can be utilized to capture amplitude and
phase deviations, compressor surge and torsional responses from both start up transients
and the torsional magnetic pole slip stimulus from synchronous motors.

 

AN INVESTIGATION INTO THE VALUE OF USING BALANCING CORRECTION ON GENERATOR WITH THERMAL BOW

Bearing vibrations are seen as major indicators for the dynamic performance and safe and
reliable operation of a turbine-generator set. When a vibration alarm is received, efforts are
concentrated to reduce the vibration at the bearing. The most common method used to reduce the
fundamental (1xRPM) vibration is field balancing (weight correction). If the vibration is caused
by mass unbalance of the rotor, weight correction on this rotor would be the most appropriate
way to reduce the dynamic forces and stresses on the rotor and bearings. However, weight
corrections are sometimes used to compensate generator thermal bow, bow due to uneven rotor
temperature distribution often seen on generators with shorted turn(s). In this case, the bearing
vibrations would be reduced, but the dynamic forces and stresses may not be, and thus a better
dynamic performance and safe operation may not be achieved. This paper investigates into the
value of using balancing weight to reduce bearing vibrations due to thermal bow with a case
study on a 4-pole generator with a suspected shorted turn. The paper evaluates not only the end
result vibrations, but also the shear forces, moments and stresses on the rotors. The evaluations
are based on the results of a comprehensive rotor dynamic study, validated by field data.

 

Reduction of high vibration on an air compressor

Vane type unit which is driven via a coupling and stub shaft splined to
diesel. The stub shaft is support by an antifriction bearing.