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High Performace Test & Measurement Solutions for Noise & Vibration Applications
High Performace Test & Measurement Solutions for Noise & Vibration Applications
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W E lCo m E to t h E I N S I D E R The Data Physics Internal Newsletter
April. 2013 | Volume 7 - Number 4
In this issue you will find some interesting information about several applications. A Matrix multishaker system was installed at China Lake to control a new six degree of freedom table. Hal- liburton received its first SignalForce shaker system and a Sig- nalStar controller for shock and vibration testing of their oil well service equipment. Visteon in France purchased a shaker for automotive testing. We also review turbomachinery used in the Power Generation industry covering steam, natural gas, nuclear and hydroelectric facilities where SignalCalc Turbo applications can be found. In line with a current web seminar topic, we ex- amine rotational vibration measurements on hard disk drives. Finally, there is a section leading you through calculations of displacement on a shaker specified by axial stiffness instead of load support to determine its suitability for a particular test.
Many of you, not directly working for a Data Physics company, have been wondering if there is any news about the performance for the last Fiscal Year. Yes, we can report that sales grew by 18% over the prior year. Due to some technical reasons, however, we were unable to ship approximately $1.5M worth of manufactured goods at January 31, leaving us with $21M in revenue for the year, only a mild increase of growth over the prior year. Regrettable as it was at the yearend, now that we are more focused on the current year, we like the advantage that we started with a $7.5m backlog. We are looking forward to a third year in a row with approximately 20% growth. The first couple of months have been on track and the sales funnel looks healthy. The worldwide economic outlook is better than at any time in the last three years. Let’s make every effort to ride this wave of success.
Corporate News
SignalCalc & SignalStar
Data Physics Matrix 6 DOF Control- ler Installed at NAWS China Lake
SignalCalc Turbo – A Review of Common Turbomachinery Appli- cations in the Power Generation Industry
Rotational Vibration Measurements for Better Hard Disk Drive Design
SignalForce & SignalSound
Visteon Selects SignalForce for Squeak and Rattle Test System
Axial Stiffness
openings
Data Physics is seeking qualified applicants for a number of positions in various functions at its offices in San Jose, California, Corona, California and Hamden, Connecticut. Please see listings in the Careers section of the Data Physics website for details. You are invited to refer suitable candidates with the promise of a monetary reward for the successful hiring of your referred candidates. The size of the reward will vary between $250 and $1000 depending on the position.
Upcoming Events
Web Seminars
Orbit and Shaft Centerline Analysis on Turbomachinery on Tuesday, May 14, 2013
Rob Bloomquist, Product Manager for SignalCalc Turbo, will present the seminar. Analysis of orbits and shaft centerline data are two aspects of vibration analysis unique to large turbomachinery supported by fluid-film bearings. This web seminar will focus on analysis and correlation of orbit and shaft centerline data, which can provide valuable insight into the effects of misalignment and other malfunctions on shaft vibrations.
Modal Impact Testing with SignalCalc Analyzers on Thursday, May 30, 2013
Raman Sridharan, Applications Engineer, will cover the basics of using a SignalCalc Dynamic Signal Analyzer for impact modal testing. Topics include a brief introduction to modal testing, choosing the proper equipment, important aspects of making accurate modal measurements and data management in modal testing. Register for upcoming Data Physics Web Seminars.
View Recordings of past Data Physics Web Seminars.
tradeshows
Visit the Data Physics website for a complete list of 2013 tradeshows.
ESTECH at San Diego, California on April 29 to May 2, 2013
The IEST 59th annual technical meeting will take place in the San Diego Marriot Del Mar Hotel. ESTECH has conference sessions and an expo covering a wide range of topics including design, test, and evaluation/product reliability; con- tamination control; aerospace; and nanotechnology. The event will have 6 parallel technical sessions. Data Physics is at booth 22.
MFPT at Cleveland, Ohio on May 13 to 17, 2013
Machinery Failure Prevention Technology (MFPT) 2013 and ISA’s 59th International Instrumentation Symposium are having a joint conference at the Wyndham Hotel at PlayhouseSquare, Cleveland, Ohio. This year’s theme is “Sensors and Systems for Reliability, Safety and Affordability”. Data Physics will be at booth E.
SAE Noise and Vibration Expo at Grand Rapids, Michigan on May 20 to 23, 2013
SAE NVH conference and trade show takes place at the DeVos Place Convention Center. This noise, vibration and harsh- ness event is a must in the industry and it occurs only once every two years. Leading automotive, commercial vehicle and aerospace companies and professionals come together to discuss the latest information about vehicle design, testing and engineering. Data Physics will be at booth 306.
SENSOR+TEST 2013 at Nürnberg, Germany on May 14 to 16, 2013
The Measurement Fair, SENSOR+TEST 2013, takes place in Nürnberg, Germany. The event offers a thorough overview of system expertise for testing, measuring and monitoring tasks in a wide range of industries. SENSOR+TEST prides itself on being an intensive innovation dialog between suppliers of sensors, measuring and testing technology. Data Physics (Deutschland) GmbH will be at hall 11 and stand number 11-434.
Spacecraft and Launch Vehicle Dynamic Environments Workshop at El Segundo, California on June 4 to 6, 2013
The workshop is an annual forum to confer about the best approaches for designing, modeling, analyzing, and testing modern space systems for loads, acoustics, vibration, and shock. The gathering is intended to be informal, enabling at- tendees from various US and non-US organizations to exchange ideas and information.
Automotive Testing Expo Europe 2013 at Stuttgart, Germany on June 4 to 6, 2013
Automotive Testing Expo is a leading event for every aspect of vehicle, motorcycle and components testing, validation, reliability assessment, quality evaluation and related data capture and analysis. Data Physics (Deutschland) will once again be on hand at booth 1754. The well attended event displays the latest technologies in the areas of vehicle, motorcycle and components testing, evaluation, quality engineering and validation.
ASME Turbo Expo at San Antonio, Texas on June 3 to 7, 2013
The well regarded turbomachinery industry event includes a technical conference and expo. This year the location is in San Antonio, Texas. ASME (American Society of Mechanical Engineers) Turbo brings together experts from various fields including gas turbines, steam turbines, wind turbines, fans and blowers, solar brayton and rankine cycle and supercriti- cal CO2. Rob Bloomquist, Data Physics’ Product Manager for SignalCalc Turbo, will be on hand at booth 412.
Vibration Institute at Jacksonville, Florida on June 19 to 21, 2013
The 2013 Annual Training Conference and Expo will cover topics such as identification, analysis, and correction techniques such as balancing and alignment. The focus will be on techniques used in vibration analysis, basic rotor dynam- ics, operating deflection shapes, time waveform analysis, machine isolation, and machine monitoring. Data Physics will be at booth 14.
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Data Physics matrix 6 DoF Controller Installed at NAWS China lake
A Data Physics Matrix multishaker controller was recently installed at the Naval Air Weapons Station, China Lake, CA. This Matrix system is used to control a new Team Tensor 18 kN six degree of freedom (DOF) table.
The mechanical design of the Tensor 18 kN vibration test system is similar to the system currently installed with a Data Physics Matrix controller at the Center for Advanced Lifecycle Engineering (CALCE) at the University of Maryland. It is an over-constrained system using twelve ED shakers for 6 DOF vibration excitation out to 2,000 Hz. Four 900 lbf RMS shakers are used in each axis to drive a 30 inch square table.
team tensor 18kN Vibration test System
The Tensor 18 kN has a system of hydrostatic bearings enabling 6 DOF vibration. The Matrix controller uses an advanced multiple-input, multiple-output (MIMO) control scheme to deal with the over constrained (more shakers than rigid body DOF) system.
Data Physics recently ran a series of successful 6 DOF random tests on this table. The control scheme used 4 triaxial control accelerometers with the 12 shakers for a 12 x 12 control matrix. Kinematic transformation was used to transform the 12 linear control accelerometer responses to the 6 rigid body DOF (X, Y, Z, Rx, Ry, Rz). Results of a basic random test can be seen below for each axis and rotational DOF.
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X-Axis Control Response
Z-Axis Response
SignalCalc turbo – A Review of Common turbomachinery Applications in the Power Generation Industry
Rotating machinery such as motors, pumps, turbines, generators, compressors, fans, and blowers play mission-critical roles in a wide variety of industries, especially Power Generation. Most of these machines utilize proximity type transducer systems mounted at each fluid-film bearing location, and often have permanently mounted Phase Trigger/ Tachometer sensors. Given both their design and criticality, these rotating machines make good candidates for the application of SignalCalc Turbo during factory testing and in-situ troubleshooting of vibration problems in the field.
Opportunities to apply SignalCalc Turbo are most prevalent in three types of power generation facilities: steam, natural gas and hydroelectric.
Steam Power Plants – Coal, Oil, and Nuclear
In a fossil fuel fired steam plant, steam is produced in a boiler by burning coal or fuel oil in a furnace. Steam at high pressure and temperature is admitted into the turbine, rotating the turbine by the energy imparted to the turbine blades. Coupled to the end of the steam turbine rotor is the electric generator rotor, occasionally accompanied by a rotating exciter.
low Pressure Steam turbine Section with top of Casing Removed
In a steam plant, auxiliary rotating equipment is also needed to support flow of steam, condensate, and cooling water, and to support the furnace which fires the boiler. Large centrifugal pumps, driven by electric motors or small steam turbines, provide feed water to the boiler. Additional centrifugal pumps are used to provide cooling water to a condenser where exhaust steam is converted back to water. To support air flow through the boiler, large motor-driven fans are used to force air into and draw air out of the furnace for the boiler.
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motor-Driven Fan motor-Driven Boiler Feed Pump
A nuclear plant also uses a large steam turbine generator to convert steam energy to electricity. But instead of using a coal or oil-fired boiler, a nuclear reactor is used to create the heat necessary to convert water to steam. Large motor-driven centrifugal pumps with vertical shafts circulate water through the reactor, and provide critical cooling for the reactor.
Reactor Coolant Pump for Pressurized Water Reactor type Nuclear Plant
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Main turbine generators in both fossil fuel and nuclear plants are typically single-speed, synchronized to line frequency (rotating at either 50 Hz or 60 Hz). Centrifugal pumps and fans supporting the processes are typically motor-driven at 1X line frequency (two-pole motor) and sometimes at 1/2X line frequency (four-pole motor). Variable frequency drive (VFD) motors are also sometimes used as drivers for centrifugal pumps, as are smaller steam turbines. Gearboxes are occasionally used between the driver and driven equipment to increase or decrease the speed of the driven equipment as dictated by the design.
Natural Gas Power Plants - Simple and Combined-Cycle
Gas turbine generators are being selected with increasing frequency for newly constructed natural gas power plants. In a simple cycle plant, natural gas fuel is used to power the gas turbine, and the exhaust is simply vented to atmosphere. Industrial gas turbines are similar in design to a jet engine; when air enters the gas turbine it is immediately compressed by a series of rotating blade sets before being combined with fuel and the mixture is ignited to generate thrust. To convert thrust to rotational energy, additional turbine blades are used to drive a power turbine rotor, which in turn is coupled to an electric generator. Some gas turbine designs, called “aero derivatives”, are actually aviation-type jet en- gines modified for land-based power generation service.
A combined cycle power plant is a combination gas and steam turbine facility. Heat from the gas turbine exhaust is captured and used to create steam for an accompanying steam turbine(s). Because of this capture of exhaust heat, overall efficiency of a combined cycle plant is much higher than that of a simple cycle plant. Similar to coal, oil-fired, and nuclear plants, combined cycle facilities require large centrifugal pumps to circulate condensed steam back into the heat recovery steam generator where it is converted to steam, and to circulate cooling water in a separate loop.
turbine Section of large Gas turbine Generator Unit
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Large gas turbine generators are typically single-speed, synchronized to line frequency (either 50 Hz or 60 Hz). Aero derivate gas turbines, however, often employ several rotors which rotate independently at much higher speeds, sometimes above 10,000 rpm. Because they are modified from aviation service, aero derivative gas turbine shafts usually rely on lighter weight roller element bearings for support unlike all the other rotating machines described here.
Hydroelectric Power Plants
Hydroelectric generating facilities are relatively simple. Water held in a reservoir, usually held at significant elevation above the turbine as potential energy, is fed to the hydro turbine through a long pipe called a penstock. At the inlet to the turbine, the energy in the high pressure water is imparted to the large vanes of the hydro turbine, which in turn rotates an electric generator, typically mounted at the top for vertical designs. By comparison to other types of turbines, they rotate quite slowly, typically less than 500 rpm.
hydro turbine Generator
Summary
Steam, natural gas, and hydroelectric power generation facilities utilize large, critical, rotating machinery in their processes for generating electricity. Because these rotating machines usually employ fluid-film bearing design and are fit- ted with proximity probes, they are ideal candidates for application of SignalCalc Turbo.
Manufacturers of the rotating machinery used in these facilities make excellent target customers for SignalCalc Turbo. These manufacturers often have test facilities capable of spinning up rotating shafts to full speed, sometimes even under simulated load conditions. Vibration and performance test requirements are often dictated by the end user customer. Rotating machinery manufacturers also typically have field service groups that travel to customer sites to trou- bleshoot equipment problems.
Power Generation companies are also excellent candidates for SignalCalc Turbo. Many have centralized, corporate reliability groups with expertise in rotating machinery diagnostics. These groups often support the needs of multiple sites with their specialty services and instrumentation.
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Rotational Vibration measurements for Better hard Disk Drive Design
A hard disk drive (HDD) goes through rigorous vibration testing. Performance and efficiency of hard disk drives may be hindered by poor vibration conditions. From a broad measurement perspective, vibration measurements on a HDD can be classified into the following:
1. Vibration Characterization Measurements 2. Modal Analysis Measurements 3. Rotational Vibration Measurements
In this article, we will focus on the last category, rotational vibration (RV) measurements. Rotational vibration is the angular acceleration movement experienced by a hard drive.
The moving elements inside a hard drive such as the spindle, platter, read/write head, arm mechanism, etc., all contrib- ute to the twisting and turning motion of a HDD. Not only does the hard disk drive generate vibration, but the drive’s performance is also susceptible to rotational vibration. Figure 1 illustrates the typical HDD components.
Figure 1: the hard Disk Drive
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To meet the constant need for more hard disk space and faster read/write times, hard drive manufacturers use multiple platters spinning at very high RPMs, which exacerbate the forced vibration and sensitivity to external vibration. Hard drive manufacturers such as Western Digital, Seagate, Toshiba, and Hitachi all rely on SignalCalc Analyzers to analyze and improve hard drive design that offer better resistance to RV problems.
Understanding the levels of RV is important to both hard drive manufacturers and the organizations that use mass storage, as high RV lowers the read/write times and affects the customer experience. Data centers utilize arrays of hard drives and servers that are typically arranged in cabinets for easy access by staff. This has a negative effect on HDD performance as the vibration is transmitted from one hard drive to another.
Consequently, understanding RV is important for data centers, mass storage integrators, and rack manufacturers. It be- comes critical for companies with mass storage requirements that are essential for their business success. This includes Data Physics’ customers such as Facebook, Apple, Microsoft, and Google.
Figure 2: Server Room at the U.S. National Archives and Record Administration
Measurement Procedure:
Angular acceleration experienced by a hard drive can be calculated by placing two accelerometers at a known dis- tance (D) on a hard drive in the axis of interest and using the formula2:
RV is measured in rad/sec2 and typically displayed in power units of (rad/sec2) 2/Hz.
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SignalCalc Analyzers can be configured to display the difference between the FFT of channel1 and channel2 by switch- ing a parameter in the ‘SignalCalc_240.ini’ file located under the installation directory shown in Figure 3.
Figure 3: SignalCalc_240.ini Configuration for RV measurement
SignalCalc software automatically does the subtraction from channels 1 and 2 and creates the following User Signals when the parameter WFMSUB is set to 1:
UX = X2-X1 (difference in time signals between channel2 and channel1) US = S2-S1 (difference between spectra between channel2 and channel1) US12 = Auto Power Spectrum of US12 UG12 = Average of US12
Figure 4: Signal map Showing RV measurement Signals
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The Engineering Unit (EU) table can be used to apply the term (1/D) to the difference between FFT of channels to complete the RV measurement. Users can define their own physical observation by identifying a metric equivalent and describing the new unit in terms of nine fundamental physical units, each with precise definition. The same technique is used to display any combination of signals subjected to linear operations such as differentiation or integration via the versatile EU table.
Figure 5: Rad/Sec2 Unit in the Engineering Unit Table
RV spectra are most often shown in normalized power spectral density view (PSD). Figure 6 shows a sample RV measurement in the SignalCalc user interface.
Figure 6: Rotational Vibration PSD
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While a relatively simple measurement, rotation vibration is very critical for hard disk drive users and manufacturers. With some simple steps, RV measurements can be made automatic in the SignalCalc environment. SignalCalc Ace on Quattro provides a highly accurate and cost effective solution for this low channel count measurement.
halliburton Commissions its First SignalForce Electrodynamic Shaker
Halliburton recently commissioned a SignalForce LE-816/DSA10-50K and SignalStar Scalar vibration test system to add local capabilities for shock and vibration testing of their oil well service equipment that is designed, tested and manufactured at the Duncan Oklahoma site. Included with the SignalForce shaker were a 48” Head Expander with a Guid- ance System and a 48” Monobase Slip Table Assembly.
Halliburton’s Duncan facility had some in-house testing capabilities and test equipment, but whenever they needed to do vibration testing on their products, they were forced to either outsource this or travel to a remote Halliburton site located in Houston. This meant moving the relatively large test articles and spending several days at the Houston site, along with the inconvenience and delays associated with working around the scheduling of the local test needs in Houston. They were interested not only in adding their own vibration test capabilities at the Duncan location, but also in upgrading the testing from a hydraulic to an electrodynamic shaker system, giving them broader frequency cover- age and potentially higher force levels.
Being able to test using Time History Replication, in addition to standard Sine, Random and Shock control profiles, was also important to the engineers at Halliburton. This provided the ability to use “road data” when testing their products, that are in fact used on vehicles and subject to this type of vibration.
Halliburton chose the Data Physics system over competitive hydraulic and electrodynamic vibration test systems because of better overall performance and value, and because Data Physics was able to work closely with them to ensure both a technical fit and a financial benefit. Data Physics interactive and consultative engagement along with strong service and support further supported Halliburton’s decision.
Halliburton and other global companies all have requirements for their products to survive both in transportation and use in harsh environments. In fact, failure of this type of equipment can cost millions of dollars per day in down time. Data Physics SignalForce shakers and SignalStar controllers provide compelling solutions for shock and vibration test applications in the oil and gas industry.
These applications have been traditionally serviced using hydraulic shakers, but comparable electrodynamic shakers often have a strong competitive advantage in both price and performance.
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Visteon Selects SignalForce for Squeak and Rattle test System
Recently, Data Physics received a unique request from Visteon’s technical center in Harnes, France. Engineers were looking to acquire a shaker for use under a climatic chamber for squeak and rattle testing of automotive dashboards and instrument clusters. The requirements for the system included mounting an isolated reaction mass similar to an existing vibration test system at Renault and a decoupling assembly to decouple the shaker from the chamber. Both of these requirements are unique and required additional design.
The test requirements are fairly basic. The shaker has to run sine profiles, random and time waveform replication from 5 to 250 Hz, with acceleration levels of 0.3 to 1.5 g with a 200 kg test fixture. Additionally, the system is integrated in a climatic chamber running from -30 ° C to +85 ° C.
The proposed solution from Data Physics and Actidyn included a LE-308/DSA10-20K vibration test system with a cus- tom reaction mass and support frame. The frame includes central guide bearings for precision guidance and cross-axis restraint, designed to protect the shaker armature. The LE-308 shaker is a very good shaker for this type of application due to its force range, armature weight and shaker size.
One of the principal factors influencing the selection of the SignalForce solution was the excellent presales technical support provided by both Actidyn and Data Physics. The high level of support helped to provide the customer with confidence in the proposed solution and future support.
Figure 1: System outline in Final Configuration
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Figure 2: Isometric View of System
Axial Stiffness
This brief example addresses mass limits on smaller shaker systems which do not have a specified load support but have a specified axial stiffness.
The only load support provided for many smaller shakers is the armature guidance. The flexible guidance that holds the armature in place supports the armature and keeps it at neutral position. With the armature guidance being the only load support in vertical orientation, adding mass to the shaker will result in static deflection of the armature assembly (Figure 1).
Figure 1: Static Deflection of Armature without load Support
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The total amount of deflection (d) depends on the axial stiffness of the guidance system. As a result of the one-sided deflection, the total peak to peak displacement available is limited by twice this amount.
Common Question 1: How do you determine the maximum displacement of the V55 with a load attached to the armature?
To determine displacement limits, first look up the static payload support. The static payload for the V55 is shown in Figure 2.
Figure 2: GW-V55/DSA5-1K Performance Characteristics
The axial stiffness of the V55 shaker is 1.79 kgf/mm. In other words, for every 1kg attached to the armature there is static deflection of 0.56 mm. Because static deflection limits the peak to peak displacement (stroke) by twice the deflection, the 0.56 mm static deflection results in a loss of 1.12 mm of total travel per kg.
To determine displacement limits, only the mass of the load and shaker’s axial stiffness (k) need be known. The following example illustrates a 2.0 kg mass on the V55 shaker.
Static Deflection = 2.0 / 1.79 = 1.1 mm Displacement Limitation = 2 * 1.1 = 2.2 mm pk-pk Available Displacement = 12.7 - 2.2 = 10.5 mm pk-pk
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The condensed formula for determining available displacement is:
Where: D is the available displacement after the load is applied DS is the maximum displacement of the shaker w is the weight of the load k is the axial stiffness
Common question 2: What is the maximum weight of a test article that can be put on the V55 shaker?
Because test article weight and displacement are related there is no one answer to this question. More needs to be known about the test requirements to understand if there is a good fit for the shaker. Displacement requirements become critical to determine if the shaker will be able to perform the test.
The shaker’s mass limit needs to be evaluated both with Newton’s second law (F=mA) to make sure acceleration requirements are met and with static deflection to make sure displacement requirements can be met. Assuming the required displacement and acceleration are known, the mass limit can be calculated. For sine testing, this can easily be calculated. Generally, the vibration controller will provide the maximum displacement for any given profile.
As an example of evaluating maximum load, look at test requirement of 10 Hz sine wave at 1 g on the V55 shaker. This controlled sine test requires 4.97 mm peak to peak displacement of the 12.7 mm total available displacement.
Mass from Acceleration: Maximum mass load = F/A - Marmature= 444 / (1 x 9.81) – 0.50 = 44.8 kg
Mass from Displacement: Total unused displacement = 12.7 - 4.97 = 7.73 mm Total available static deflection = 7.73 / 2 = 3.87 mm Maximum mass = 3.87 x 1.79 = 6.92 kg
This simple example illustrates how important the displacement can be in determining the shaker’s maximum load for a given test. It is also advisable to check that the velocity limits are not exceeded for any given test, and in this case the velocity is .159 m/s, well below the shaker limit of 1.53 m/s.
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