AVSpare cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are, therefore, not all inclusive. If a tool, procedure, work method, or operating technique that is not specifically mentioned by AVSpare is used, you must satisfy yourself that it is safe for you and for others. Make sure the product or machine will not be damaged or be made unsafe by any operation, lubrication, maintenance, or repair procedures that you choose.
If any doubt arises about the correct, safe method of performing any steps of these procedures, DO NOT proceed. Seek out expert assistance from a qualified person.
NOTE: AVSpare reserves the right to make technical changes for product improvement. This manual may contain illustrations and photographs, for demonstration purposes, which slightly deviate from the actual product design.
Vibration Analyzer Group
Illustration 1. 169-0720 Vibration Analyzer Group.
This Tool Operating Manual is meant to supplement the existing operating manuals for the CSi analyzer. It is not a stand-alone document. It is meant to be a Quick Guide to get started and for the unique AVSpare applications.
The 169-0717 Vibration Analyzer is a microprocessor-based device for collecting, analyzing, and displaying dynamic data. With the 169-0735 Field Balance Group, it also is a complete stand-alone balance analyzer with up to four plane capability. In addition to linear vibration data, torsional vibration data can be acquired with the 4C-9021 Torsional Vibration Measurement Group.
The 169-0717 Vibration Analyzer is produced for AVSpare by Computational Systems Inc. of Knoxville, TN. It is essentially a CSi Model 2117 and the software is derived from a CSi predictive maintenance program called "MasterTrend". Although completely compatible with MasterTrend, the software has been customized for application to AVSpare engines and vehicles. None of the software is copy protected but it IS copyrighted and must be treated accordingly.
The 169-0717 Vibration Analyzer is a single channel, 400 line (max.) FFT (Fast Fourier Transform) spectrum analyzer. Processing is done digitally which allows communication of the Analyzer with a host PC (personal computer) and directly to IBM graphics or Epson compatible printers for hard copies of the data (spectra and other data).
The normal data acquisition method is to use "routes" supplied on the LIN33.DAT disk. A route is a set of predefined measurement points arranged in a sequence for efficient data collection. The routes, when loaded into the analyzer, also set a number of key parameters in the analyzer to insure that the measurement units and sensor sensitivities are properly set. The measurement frequency range is also predetermined on each route point, usually as a function of rpm. The exceptions are some velocity points and the acceleration routes.
In addition to the "route" method of data collection, the user also has the option to acquire data with user defined setup parameters (OFF ROUTE and ANALYZE modes).
The many features of the vibration analyzer are accessed through the various function keys which bring menus to the back lit LCD display.
The linear routes software custom tailors the analyzer to specific applications. Each route contains a number of suggested measurement points organized in a logical measurement sequence. Routes are available for Marine, EPG, Industrial, Truck, and Captive Vehicle applications as well as Accelerations (the acceleration routes require the optional 4C-3032 Accelerometer). Each measurement point, in addition to suggesting a measurement location, also sets the sensor sensitivity, determines the units of the data, sets the frequency range (usually a function of rpm), defines 6 key variables of the data which are stored as a "parameter set", and sets other measurement parameters (number of samples, window type, etc.). The routes also specify which data is stored automatically.
Routes are generated by AVSpare using the "MasterTrend" software and can not be modified by the user. It is possible to rename the database file using the DOS "rename" command after the file LIN33.DAT contains data "dumped" from the analyzer.
Illustration 2. 169-0735 Balance Group.
Illustration 3. 169-0717 Vibration Analyzer.
Accessory for 169-0720 Analyzer Group
4C-9021 Torsional Vibration Measurement Group
The 4C-9021 Torsional Vibration Measurement Group contains a battery powered signal conditioner to convert voltage obtained from a magnetic pickup sensing gear teeth to a signal representing torsional vibration. Originally for 3600 Engines but can be used on any rotating machine which has a proper gear and magnetic pickup installed. Software included customizes the analyzer for torsional vibration measurements.
Accessories for 4C-3030 Vibration Analyzer (Only)
9U-5616 Adapter Cable
The 9U-5616 Adapter Cable permits charging a spare 4C-6729 Battery Pack outside of the 4C-3030 Analyzer (no longer available). See Illustration 4.
Illustration 4. Adapter Cable.
9U-5836 Adapter Cable
The 9U-5836 Adapter Cable permits connecting the 4C-3030 Analyzer to the battery charger while using the speed pickup in the cancelled 4C-6920 Balance Group. See Illustration 5.
Illustration 5. 9U-5836 Adapter Cable.
4C-3032 Accelerometer Pickup
The 4C-3032 Accelerometer Pickup is useful for higher frequency measurements where acceleration units are needed. The response is flat between 6 and 6000 Hz (± 5%, 3 to 10000 Hz). Sensitivity is 10 mV/g.
Initial Setup of PC and Analyzer
The analyzer is an electronic tool that uses various firmware and software programs to collect, analyze, display, and print vibration data. Some programs are loaded into the analyzer and some are loaded onto the PC. Here is a brief summary of the included disks. Additional information is contained in the CSi manuals.
FIRMWARE: A term referring to the software that controls or instructs the functions of the vibration analyzer. This must be loaded into the analyzer from the PC and is done only once unless there is an upgrade version needed or in the rare case that the analyzer memory is corrupted.
CSICOMSA: 3 disks of a stand-alone version of a component of MasterTrend that allows the analyzer to communicate with the PC. This is required to transfer routes and data from the PC to the analyzer using the computers serial port.
WIN Install: WIN Install is the software that installs CSICOMSA on the PC. (Make a work copy of the disk and keep the original as a backup. This program erases itself when install is complete and will not be available if you change computers.)
LIN33.DAT: AVSpare specific routes that are loaded from the PC into the analyzer as needed using the program CSICOMSA using the computer's serial port.
Fast Bal 1: Fast Bal 1 is a downloadable program that is loaded into the analyzer from the PC as needed to perform 2 plane first order balancing.
Firmware is the brain of the analyzer and must be loaded before you can do anything. Complete instructions are in the CSi manual shipped with the analyzer. A quick way to load the firmware is outlined below.
Quick Load of Firmware
If the firmware is lost from the analyzer or to update it quickly, follow the steps below:
1. Place the firmware diskette in the "a" drive of the computer.
2. Connect the analyzer to the computer with the communication cable.
3. At the "a" prompt in a DOS window type "download" <enter>.
4. With the download program running, configure the serial port (COM 1, COM 2).
5. On the analyzer, hold down the UTILITY (tool box) and ENTER keys while turning on the analyzer.
6. The firmware will start loading immediately.
NOTE: This will completely erase all routes along with the FASTBAL if loaded.
If, when loading, a password is needed for the Analyzer, the password is "CSI".
Installing CSICOMSA Communications Software
Make a backup copy of the disk: "WIN install" that is part of the "CSICOMSA" package.
Use the MS-DOS "DISKCOPY" Command!
The "WIN install" disk erases itself when installed.
Use the copy to install the CSICOMSA software.
CSICOMSA is a communications software that runs under Windows (TM) 3.1, 95, or 98. This software is required to load the AVSpare specific routes into the analyzer. Instructions for installation are listed in the manual "Install and Configure-Quick Start for CSi Software".
Typical Setup Screens for the 169-0717 Vibration Analyzer
(Recommended for most AVSpare Applications.)
1. Press the "UTILITY BUTTON". Toggle to "CHANGE SETUP" and press "ENTER".
2. Continue to toggle through the remaining screens and set as follows.
NOTE: To print directly to an Epson or IBM Graphics printer, use the 4C-3040 Printer Adapter and toggle "PRINT MODE" to "720 IF". The CSi Model 2117 manual also contains additional information.
NOTE: The settings above result in the best data compatibility with the 169-0717 Vibration Analyzer. There may be instances when setting "SIGNAL INTERGER MODE" to "ANALOG" results in more usable data. The CSi Model manual also contains additional information.
Loading Routes into the Analyzer
The route database file, LIN33.DAT is supplied on a 3.5 inch diskette. It must be copied to the subdirectory where the CSICOMSA program is located. The default subdirectory is "MTWIN".
The file LIN33.DAT can be copied to the MTWIN subdirectory either from the DOS prompt or through File Manager (Windows 3.1),or "Windows Explorer" (Windows 95 or 98).
After LIN33.DAT is copied, launch CSICOMSA by selecting Start>>CSI RBM Applications>>C.S.I. Screen 1 will appear, as shown in Illustration 1.
Illustration 1. Screen 1.
After screen 1 appears, Click on File>>Open database and screen 2 will appear, as shown in Illustration 2.
Illustration 2. Screen 2.
After screen 2 appears, click on Add Database and screen 3 will appear over screen 2. Refer to Illustration 3.
Illustration 3. Screen 3 Appears Over Screen 2.
Select lin33.dat and click on OK. Screen 4 will appear with the Lin33.dat added to the list. Select Lin33.dat and click OK.
Illustration 4. Screen 4.
Illustration 5. Screen 5.
Screen 5 will appear with LIN33.dat in the upper left hand corner. This indicates that the database LIN33.DAT is active.
Click on the analyzer icon (Analyzer Communications) and Screen 6 will appear. Make sure that the numbers in the Setup Com window (Screen 7) agree with the analyzer settings. 9600 baud is the preferred setting. When these settings are the same as the analyzer settings, click on the Initiate button and Screen 8 will appear.
Power up the analyzer and push the utility button in the upper left hand corner. Select COMMUNIAVSIONS>>CONFIGURE PORT. Make sure that the settings are the same as set up on Screen 7.
Select LOAD ROUTE from the communications menu and proceed to load the desired routes. Follow the directions on the analyzer screens.
Selecting CLEAR MEMORY will erase all routes and data stored in memory!
Selecting a Route 1.
1. Press "On".
2. Press "Reset".
3. Press "Utility".
4. With cursor select "(2) Select Route".
5. Press "Enter".
6. Cursor to desired Route.
7. Press "Enter".
8. Press "Reset".
Take a Route Data Point
To take a measurement on a route point, place the velometer at the desired location. Adjust engine RPM and LOAD to the desired levels.
1. Press "On".
2. Press "Reset".
3. Cursor to desired Route Point.
5. Type in correct LOAD from the keypad.
6. Press "Enter".
7. Type in correct SPEED from the keypad.
8. Press "Enter".
After the analyzer has taken 6 averages the LED on the front panel flashes the analyzer is finished taking data and the Spectrum and Parameter Set are stored in memory.
9. Proceed to the next route point or display data.
10. Press "Utility".
11. Cursor to "(2) Select Route".
12. Press "Enter".
13. Press "Enter".
14. Press "Reset".
Displaying Route Data
1. Press "On".
2. Press "Reset".
3. Cursor to desired route.
4. Press "Analyze".
5. Cursor to "Display Spectrum".
6. Press "Enter".
When finished, the RESET key will return to the Route Point Data collection screen.
Using Virtual Printer
Data and all screens can be printed to your computer printer through the Windows program "Virtual Printer". The program must first be installed as indicated in the Virtual Printer manual.
After the Virtual Printer program is installed, the analyzer is connected to the computer with the same communication cable that is used to load routes. The analyzer must be set to use the virtual printer program as indicated on the included section labeled "TYPICAL SETUP SCREENS". This option is under UTILITIES>>CHANGE SETUP>>DISPLAY CONTROL.
Using the 4C-3040 Printer Adapter
The 4C-3040 Printer Adapter will print to an IBM or Epson dot matrix printer without a PC. This is for older analyzers but it still works on new analyzers. Virtual Printer is still the method of first choice.
If the screen is a route point that contains data, the Parameter Set and Notes will be included. The parallel printer should be turned off.
1. Connect the 40 Printer Adapter to the RS232 port on the analyzer.
2. Connect a parallel printer cable to the 40 Printer Adapter (25 pin connector).
3. Connect the opposite end of the printer cable to the printer (36 conductor connector).
4. Turn on the analyzer.
5. Press "On/Off".
6. Press "Reset".
7. Cursor "to desired route point".
8. Press "Analyze".
9. Cursor "Display Spectrum".
10. Press "Enter".
11. Turn on printer.
12. Press "0" key and hold for 2 seconds.
NOTE: Changes to the display can be made at this point. Use of the cursor keys, display expansion, and harmonic markers can be added for additional details.
NOTE: Always turn the printer on last.
Pressing the ENTER key starts the printing. Any data stored on a route point will be printed including data stored using the ANALYZE MODE.
Data acquired in the OFF ROUTE mode can also be printed with the GENERATE REPORT function.
A typical printout of a route point is shown in Illustration 18.
1. Press "On".
2. Press "Reset".
3. Press "Utility".
4. Cursor "(2) Select Route".
5. Press "Enter".
6. Cursor to desired Route.
7. Press "Enter".
8. Press "Reset".
The only downloadable program for the 169-0717 Vibration Analyzer is the CSi FastBal 1 two plane balancing program.
Loading Balance Software
The FASTBAL 1 software version must match the firmware version and the serial number of the analyzer.
CSi Fast Bal 1 turns the analyzer into a single or multiplane balancing tool. For engines, this would be the front and rear of the engine at the crankshaft damper and flywheel.
After the program is transferred to the analyzer, it is still not usable. To start the balance routine, you must enter the downloadable program. (This starts the balance program.)
Enter Downloadable Program
To enter Fast Bal 1:
1. Press "UTILITY" cursor to select "(2) ENTER DWNLD PROG".
Illustration 19. Select "(2) ENTER DWNLD PROG".
2. Press "ENTER".
3. Press "ENTER".
The analyzer is now a 2 plane balancer. Follow the instructions in the CSi Fast Bal 1 manuals.
There is a complete menu tree showing the nested menus published in the CSi Fast Bal 1 manual (page 4 and 5) for quick reference. Refer to the References section of this manual for more information.
Exit Downloadable Program
To exit the balance mode:
1. Press the "UTILITY" key and cursor to select "(3) EXIT DWNLD PROG".
Illustration 22. Select "(3) EXIT DWNLD PROG" To Exit.
2. Press "ENTER". This will return you to the route point.
The CSi Fast Bal program remains in the analyzer memory and the analyzer can now be used in the normal route mode.
General Application Guide
This portion of the manual is intended to be a practical guide to help in a number of situations. Covered are balancing using the 169-0717 Vibration Analyzer along with Fast Bal software, general vibration troubleshooting, a discussion of the various limits and guidelines currently used for AVSpare equipment, a guide to interpreting spectral data, and a list of common procedural problems with solutions to them. The section on balancing contains both the primary manual for using the Balance Group plus some practical tips for difficult situations. Some of these tips have come from the experience of users in the field.
Routine vibration measurement and analysis with the 169-0717 Vibration Analyzer can be broken down into three parts:
- 1. Selecting and loading routes
- 2. Acquiring data (measurement)
- 3. Data analysis and interpretation
- 2. Acquiring data (measurement)
Each of these parts requires a certain amount of planning because each part affects the final results. Problem solving requires a slightly different approach than simply documenting the vibration of a new installation or vehicle.
The routes included as part of the 169-0717 Vibration Analyzer have been designed to cover many common situations. A description of the routes is included in the Route Documentation section of this manual and will not be repeated here.
For Marine applications, any of the routes in the "market" called MARINE PROPULSION ENGINE can be used. All five routes have the same structure and suggested measurement points. They are for the engine's driving mechanical gears and not marine EPG. The marine routes can be used for either problem solving or documentation.
The market called EPG ENGINES contains two sets of routes with each set of five having the same route structure. The first five on the list (labeled EPG NO1 through EPG N05) have a route structure similar to the routes from previous analyzers. They can be used for general documentation or problem solving.
The second five routes in the EPG ENGINES market have a completely new route structure and new Analysis Parameter and Alarm Limit Sets. These routes are specifically set up to evaluate vibration relative to new limits which have been published for GENSETS (Form LEKX1 113, 3600 Generator Set Application and Installation Guide). The GENSET-NL1 through GENSET-NL5 have the eight specified measurement locations with Parameter Sets defined to provide exactly the data needed. Alarm limits signal the user when any of the parameters meet or exceed a limit. The new limits, measurement locations, and conditions are shown in the Route Documentation section.
The route structure of the two On-Highway Truck routes is identical. Either route can be used for any type of truck work.
The same is true of the Industrial Engine routes.
Routes for Captive Vehicle Engine/Cab have several measurement points specifically set up to help resolve operator vibration complaints. Vibration guidelines for operator comfort are usually expressed in terms of velocity. Measurement points for inside the cab are set up to measure velocity and signal the user if a guideline is exceeded. The potentially troublesome frequency (expressed as an order) is highlighted in the Parameter Set to assist in pinpointing the root cause of the problem. Alarm limits for the operator measurement points are based on the Route Documentation section.
ACCELERATION TO 10K HZ are for use with the 4C-3032 Accelerometer Pickup for high frequency measurements up to 10000 Hz. The routes must not be used with the 4C-5629 Velometer. A high vibration alarm will show on the LCD any time one of the specified parameters equals or exceeds 2 G's.
The accurate measurement of vibration requires not only the proper tools but also proper techniques. How the pickup is attached, where it is located, and how it is placed there are all important. This part of the manual will provide guidance on these factors.
The 4C-5629 Velometer Pickup is supplied attached to a 4C-3042 Magnetic Base. This is an adequate attachment for most engine-related vibration measurements where a flat ferrous surface is available. The pickup must attach solidly to the surface with no rocking noted after attachment.
For curved or non-ferrous surfaces, the 9U-5933 Probe must be used. The magnetic base is removed from the pickup and the probe installed in its place. The pickup can then be hand held in place. Care must be used so that pressing the probe against the object to be measured does not change the vibration to be measured. In other words, apply enough force on the probe to insure that the pickup follows the vibration of the object but not so much as to change the vibration.
Most vibration measurements will probably be taken on various locations on rotating machinery such as engines, generators, or marine gears. As a general guideline, the axis (centerline) of the pickup should point through the center of rotation of the machine in a purely vertical or horizontal direction. If these conditions cannot be completely met, the vertical and horizontal orientation must be maintained and the axis of the pickup should pass as nearly as possible through the center of rotation.
Axial measurements are to be taken where possible so the axis of the pickup is parallel to the center of rotation of the machine. Caution should be exercised when measuring attachments or sheet metal. Localized resonances can cause large displacements which may or may not indicate a problem.
Measurements inside of operator compartments should be taken to best define what the operator feels. For example, if a complaint is registered about foot pedal vibration, the pickup should be oriented to best measure what the foot feels. Apply normal foot pressure while taking the measurements.
Steering wheel vibration should be measured on the rim of the wheel in two directions. One measurement should parallel the axis of the steering column and the other should be at 90 degrees from the first with the axis of the pickup passing through the axis of the column. Grip the steering wheel as if steering the vehicle during the measurements.
Seat vibration can best be defined by measuring on an attachment point near the floor. Due to various mounting configurations, good judgment dictates the best location. Sit in the seat while acquiring data.
The manner in which the pickup is placed onto the measurement location can have a significant effect on the readings. This is particularly true when using the magnetic base. Allowing the magnet to "snap" onto the surface causes a shock to the pickup which creates a transient voltage to be generated.
The proper technique is to carefully place one edge of the magnet against the surface, then gently rock the pickup into place. After placement, try to gently rock the pickup side to side to make sure that it is solidly attached. If any motion is felt, seat the magnet solidly before proceeding to acquire data.
If it is suspected that a transient has been created, wait 45 seconds before acquiring data. If the first average shown on the LCD of the analyzer is significantly larger than the remaining five, the measurement should be retaken.
Using the Photo Pickup
By connecting the photo head to the analyzer as shown, engine (or other) speed will be read directly into the analyzer while collecting data on a route point. This assures that parameter set data is accurate.
Illustration 1. Using Photohead As Tachometer.
Attaching the Photo Pickup
To use, place a 1 inch long piece of the reflective tape on the OD of the damper. Attach the photohead to a suitable location with the magnetic base. Aim the photohead so that the red beam strikes the reflective tape. The photohead is aimed properly if the red LED on the back of the photohead lights as the tape is aligned with the beam. The analyzer must be turned on for power to be supplied to the photohead.
An extension cable for the photohead is included in the case.
Acquiring Data in Route Mode
Acquiring data in the route mode is the simplest and most common method of acquiring dynamic data. After the routes have been loaded into the memory of the analyzer, four simple steps are required:
- 1. Select the appropriate route.
- 2. Select the appropriate point on the route.
- 3. Attach the sensor to the object being measured at the location specified on the LCD screen.
- 4. Acquire data.
- 2. Select the appropriate point on the route.
An additional optional step is creating a descriptive note (or notes) to attach to the data.
Selecting A Route
Turn on the analyzer and press the UTILITY key. Highlight "(2) SELECT ROUTE" and press ENTER. With the up and down arrow keys, move the highlight to the desired route as shown Illustration 2. If more than six routes have been loaded into the analyzer memory, the down arrow key will cause the available routes to scroll upward until the desired route is visible.
With the desired route highlighted, press ENTER and that route is active. The LCD will return to the UTILITY FUNCTIONS main menu. Press the RESET key and the point number one will appear on the LCD. Illustration 3 shows a typical route point screen prior to acquiring data.
Line one on the LCD shows the point number, the name of the route and a three letter designation of the point (e.g., EFH means Engine Front Horizontal). Line two shows an additional description of the route and line three shows a description of the route point. The blank space in the center of the screen will display the overall level of the quantity being measured as the samples are being acquired and display the averaged overall level at the completion of the measurement.
NOTE: The "overall" value displayed is a number calculated from the spectrum by taking the square root of the sum of the all of the squared values in the spectrum.
The STATUS= NOT MEASURED indicates that no data has been stored in the analyzer memory for this data point.
The bottom line shows several important pieces of information. The first quantity is the percent of unused memory in the analyzer. As data is acquired, this number will decrease in 1 percent steps. The second item shown is the bandwidth currently set by the route point (e.g., BW=8.ORPM indicates that the current highest frequency to be processed by the analyzer is eighth order of the RPM input to the analyzer). DATA=NONE also indicates that no data has been stored on this route point.
When the screen in Illustration 4 is on the LCD, the analyzer is ready to acquire and store data.
Attach the sensor to the object being measured and insure that conditions (speed, load, temperatures) are as desired. It is good measurement practice to wait at least 15 seconds after attaching the sensor to a ferrous object with the magnet before beginning the data acquisition.
Press the ENTER key and the screen in Illustration 4 will appear on the LCD.
As the screen suggests, the load can be changed if the programmed value does not apply. Load should be input as a percent of rated or maximum. This is reference only and does not in any way influence the calculations made by the analyzer. It is not printed out on the screen prints or reports so the user may want to also create a note using the NOTES and KEYPAD keys.
After the load has been entered, pressing the ENTER key brings the screen in Illustration 5 to the LCD.
The screen, shown in Illustration 5, has a message ENTER SPEED IN RPM. It is important that the user enter the correct RPM because the analyzer uses the value on this screen to create and store the Parameter Set. This value is shown on all of the screen prints and generated reports.
If changing the RPM is required, the numbers can be entered from the keypad. When complete, press the ENTER key to begin the data acquisition process.
If the photo pickup is connected, the speed will be set automatically.
As data is being acquired, the LCD will first show that the analyzer is autoranging. Then the current averaged value of the overall level is displayed along with the number of averages remaining. Pressing the RESET or ENTER key aborts any measurements in progress.
Note that the time to complete the six averages depends on the upper frequency of the measurement. Lower frequencies require longer times.
When the averaging is complete, the screen shown in Illustration 6 will appear.
The final averaged overall value is shown along with the units. The STATUS= OK message indicates that the data has been stored, no Alarm Limits have been met or exceeded, and the overall value is high enough to indicate that the system is functioning properly. At the bottom of the screen, the percent memory left value is updated and an indication given that both Trend (a Parameter Set) and Spectral (a spectrum) data have been stored (DATA= TS).
This completes acquisition of data for this route point.
If the user is satisfied with the data indicated on the screen, the next route point can be selected by pushing the up or down arrow and the process repeated. Pressing the ENTER key at this point causes the current data to be overwritten.
Any route point can be selected at any time as determined by the user and only those points needed have to be used.
Additional data can be stored along with the route point data by using the ANALYZE mode of data acquisition.
Acquiring Data in Off Route Mode
The "OFF ROUTE" mode can be used to define data points with either the same characteristics as "route" points or with different characteristics. If routes are loaded, offroute points can be set up identically including an Analysis Parameter Set. If no routes are loaded, no Analysis Parameter Set can be created for the offroute points.
The OFF ROUTE mode is useful for unusual situations or in the case where an operator is at a job site and discovers that the route points were not loaded or accidentally erased.
Offroute data can be dumped to floppy disk or printed on a printer similar to the route data.
When offroute points are defined while using a route, they must be accessed from that same route.
If multiple offroute points are to be defined with similar parameters but different labels, "copies" can be made by selecting an existing point and selecting "DEFINE POINT" and modifying only those parameters (labels) as desired.
NOTE: Defining offroute points prior to loading routes into the analyzer from the host computer can allow a situation where the "MEMORY IS EMPTY" message is displayed on the LCD at power up of the analyzer. However, the route points can still be accessed through the UTILITY, SELECT ROUTE menu. Offroute points are accessed by entering the OFF ROUTE mode.
Defining Offroute Points
Before defining an offroute point, you must decide whether it is to be attached to a route already in the analyzer memory or part of a LOCAL ROUTE made up only of offroute points. If routes are already in the analyzer memory, a LOCAL ROUTE cannot be created.
To define an offroute point, press the OFF ROUTE function key. The screen shown in Illustration 7 will appear on the LCD.
Adding Notes to the Data
Notes can be created and attached to either route or offroute points by pressing the NOTES key to bring the NOTEPAD screen to the LCD as shown in Illustration 7.
Shown on the screen is the name of the current database along with its date code. Pressing the KEYPAD key brings the screen in Illustration 8 to the LCD.
Notes up to 32 characters long can be created by typing in letters or numbers from the keypad. When the note has been typed in, pressing the ENTER key records it in the notepad and the NOTEPAD screen again appears. Once entered, notes cannot be removed from the Notepad except by clearing the memory of all data.
Notes can be attached to route points before or after data is acquired. To attach a note that has been created, press the NOTEPAD key. Move the number highlight up or down with the up and down arrow keys until the number highlighted is for a note you want. Press the enter key to highlight the entire note then press the RESET key to attach the highlighted note (or up to 12 per point) to the route point. Notes can be removed from the route point by the same process.
Any notes attached to route or offroute points will be printed any time printing of the data is called for by the user.
Troubleshooting Vibration Problems
Solving vibration problems (troubleshooting) can be a frustrating exercise. An understanding of a few principles of vibration along with knowledge of AVSpare engines, however, can go along way in solving a large percentage of the problems encountered with AVSpare equipment.
This brief section is an attempt to help in that understanding. It is not intended to be all encompassing but merely a starting point.
What Vibration Is
Vibration is the periodic motion of an object. The key word is "periodic". It means that the motion repeats it self over a period of time. It can do that in a very simple pattern or one that is very complex.
An example of a simple vibration is one with a single frequency. The vibration can be described as having a given displacement at that frequency. If the displacement and frequency are known, the vibration is totally defined. If an object is moving up and down a total of one inch and it does so once each second, it would be said to be vibrating with a displacement of one inch at a frequency of one hertz (Hz).
If the same object, while moving up and down one inch at one hertz is also moving up and down one eighth of an inch at 3 hertz, is now vibrating in a complex pattern and the definition has become more difficult. The motion must be described in terms of the combination of the two motions-"OVERALL DISPLACEMENT" and the motion at each frequency.
Although the overall displacement may be the arithmetic sum of the two frequencies, in most cases it is not. This is because vibration is what is called a "vector quantity" and has associated with it another term called "phase". The overall displacement will vary depending on the phase relationship of the motion at individual frequencies.
Vibration can be categorized as "free vibration", "forced vibration", or "resonant vibration" all of which are still described in terms of displacement and frequency.
Free vibration is that which has no sustaining force associated with it but occurs when an object with mass is connected to something else with a spring. For example, if a block of steel is mounted to a large foundation through a spring and the spring is compressed and then released suddenly, the mass will vibrate at some frequency determined by the size of the mass and the stiffness of spring. The vibration will begin with a half displacement equal to the amount of compression of the spring but decay to zero after a number of cycles of vibration.
The number of cycles the vibration lasts is determined by the energy lost (due to system damping) as the mass vibrates on the spring.
Forced vibration is the result of a varying force acting on an object. The frequency of the vibration will be the same as the frequency of the force and the displacement will depend on the amount of the force and the mass of the object. This assumes that the object is not connected with springs to another object and the force acts directly on the object. Although in the real world this condition rarely exists, it is approached when the object is mounted on very soft springs and the frequency of the varying force is much higher than the natural frequency of the spring-mass system.
If the object above is mounted on springs, the result may be a resonant vibration. This occurs when the frequency of the varying force is the same as the "natural frequency" of the object mounted on the springs. Resonant vibration can also occur when a number of objects are interconnected with springs. In this case, a number of natural frequencies exist and resonant vibration can occur whenever a varying force matches one of the natural frequencies of the system.
Vibration problems in AVSpare equipment are always forced and usually resonant. In other words, troublesome vibration is the result of some varying force which is either varying more than normal or varying at a frequency which is the same as a natural frequency of some component or system. The path to solving a vibration problem, then, is to determine what is causing the varying force and either reducing the varying force or, if resonant vibration is occurring, changing the component or system which is vibrating.
In either case, the first step (the KEY) is to know the frequency of the problem vibration. Once the frequency is known, the source of the varying force can be determined by examining the possible causes at that frequency.
In other words, knowing the frequency of the vibration is the key to solving vibration problems.
Orders of Vibration
In the analysis of vibration problems occurring in rotating machinery such as engines and vehicles, almost all vibration can be related to the rotating speed of the machine. Although vibration is still defined by displacement and frequency, the frequency is expressed in terms of multiples of speed. A vibration which occurs at exactly the rotating speed is called "first order". Likewise, a vibration at twice rotating speed is called "second order", and so on.
A four stroke cycle engine can produce varying forces at both half and whole orders, therefore, there can be both half and whole order vibration. Vibration at frequencies other than half and whole orders can also be produced by driven equipment which is rotating at some multiple of engine speed. For example, a gear driven compressor operating at 1.1 times engine speed could produce vibration at "1.1 order" (and multiples of 1.1) relative to engine speed.
Internal combustion engines are by their nature a system of varying forces. In most cases, the varying forces are contained within the structure of the block (internal) with the amount of varying force acting on the engine mounts (external) controlled to acceptable limits. Only when a problem exists do the external forces reach a value which causes a vibration problem.
NOTE: Some small engines do have, by design, external forces which must be isolated by soft mounts.
For most engine configurations, the internal forces are naturally neutralized but in some, special devices are required to "balance out" certain of the varying forces. These devices rotate at either engine speed (first order) or twice engine speed (second order) depending on the forces which must be counteracted.
Two types of engine balancing devices are used on AVSpare engines. One type is a set of rotating shafts turning at twice engine speed to counteract second order forces. The other type is a set of gears on either end of the engine which have a designed amount of unbalance and rotate at either engine speed (first order) or twice engine speed (second order) depending on the engine configuration.
For these balancing devices to neutralize the intended forces, they must be properly "phased" to the crankshaft. When excessive vibration is associated with an engine with balancing devices and the vibration frequency (order) is the same as devices are designed for, phasing of the devices is a logical place to look for the cause of the problem. If the phasing is determined without a doubt to be correct, then manufacturing defects in the balancing devices should be investigated.
Some AVSpare engines, because of their design, are susceptible to a condition known as "flywheel orbit". This condition is somewhat dependent on the mass of rotating parts connected to the flywheel and is corrected by intentionally "unbalancing" the flywheel. In other words, a flywheel balanced to correct for orbit will be unbalanced if checked by itself removed from the engine.
If a solid disk of homogeneous steel is mounted on bearings and rotated, it will produce no varying forces and no vibration will result. However, if a hole is drilled near the outside diameter of the disk, the disk will produce a varying force on the bearings in any given direction perpendicular to the shaft. The disk is said to contain "rotating unbalance". Vibration produced by rotating unbalance will occur at the same frequency as the rotating speed (first order).
Because of manufacturing inaccuracies (tolerances) and material non-homogeneity, most rotating components have some rotating unbalance. This is normally controlled at the factory by careful machining or by balancing of the component. Rotating unbalance can occur if damage occurs, pilot bores become worn, corrosion occurs, or mismatched components are assembled into a rotating assembly.
Experience has shown that most vibration problems on AVSpare equipment are caused by rotating unbalance. When a vibration problem exists and the vibration is at first order, rotating unbalance is the first thing to investigate. (The exception could be if the engine has balancing devices for first order.)
In the absence of resonance, unbalance causes a constant level (displacement) of vibration, which is independent of speed. In other words, this condition is approached when an engine is mounted on extremely soft springs.
Although rare, vibration may occur at half engine speed (half order). This is usually caused by some problem in the fuel system. Any problem with the fuel delivery system which causes an unevenness in the combustion process can cause half order vibration. In addition, a burned or leaky valve can also cause unevenness and cause half order vibration.
Any time the displacement of the half order vibration is larger than the first order vibration, the fuel system or components affecting the combustion process should be checked.
NOTE: Some engines produce significant half order vibration at idle conditions. Contact AVSpare for specific guidance if high half order is measured at idle conditions.
Very often, the engine is considered the source of vibration when, in fact, the exciting forces originate in attached equipment.
If the vibration is first order, the source can often be determined by running the engine with the driven equipment detached from the engine. If the vibration still exists, investigate the engine. If the vibration does not exist, the source is either in the attachment (coupling, clutch) or in the driven equipment. Balancing of the appropriate component is the most likely solution.
If the vibration is not at an integer or half order of the engine, the source can be identified by determining what the rotating speeds associated with the driven equipment are and relating the vibration frequency to one of those speeds.
Vibration exists on a towboat with an engine running at 1800 rpm driving a 5 blade prop through a marine gear with a 3:1 reduction. Vibration is 50 HZ.
CONCLUSION: The vibration source is related to the propeller. Once again, note that the key to determining the source is the frequency.
Vibration Problem-Solving Flowchart
As stated at the start of this section, solving vibration problems can be time consuming and frustrating. Most problems, however, do lend themselves to an orderly thought process. This thought process is summarized in flow chart format in Illustration 1.
Interpreting Spectral Data
For many years, vibration has been measured using instruments which were simple tuneable filters. The raw vibration signal was passed through the filter such that the vibration at only one frequency would register on a calibrated meter. Although that was a completely acceptable and accurate way to measure vibration and pinpoint troublesome vibration, the FFT Analyzer accomplishes the same task in a fraction of the time.
Instead of presenting one frequency of vibration at a time on a meter, the FFT Analyzer presents the vibration at all frequencies present over a specified frequency range on a plot. This plot is called a spectrum (more than one plot are spectra).
The horizontal axis shows the frequency and the vertical axis shows the magnitude (displacement, velocity, or acceleration). The top of the spectral component (called a "spike" for simplicity) at each frequency is the magnitude of the vibration at that frequency. A typical spectrum as displayed on the LCD of the 169-0717 Vibration Analyzer is shown in Illustration 2.
This section of the manual will provide an approach to looking at a spectrum and determining what information is contained in the spectrum as it relates to the machine being tested. The best time to study the spectral data is while it is still in the analyzer memory and the cursor function of the analyzer is available to study the data.
The first step is to place the cursor on the spike where the frequency corresponds to the engine speed (Hz = RPM/60). Pressing the "." key sets the cursor exactly on the top of the spike. This identifies the first order vibration and provides a reference for the other spikes on the spectrum.
The spectrum in Illustration 2 is for a genset running at 1800 (nominal) RPM. Placing the cursor on the first order spike and pressing the "." key produces the screen shown in Illustration 3.
Pressing the "." key a second time places boxes (harmonic markers) across the screen at integer multiples of the first marked spike. This identifies 2, 3, 4, 5, 6, 7, and 8th orders as shown in Illustration 4.
After the first order and the integer multiples of first order have been identified, the next step is to identify 1/2 order and the integer multiples of 1/2 order. Previous markers are removed by pushing the ANALYZE key and repeating the process. This time place the cursor on the spike where the frequency is equal to half engine speed. Again, use the key to center the cursor and bring the harmonic markers to the screen. With the cursor on the 1/2 order frequency, the harmonic markers will now identify 1,1-1/2, 2, 2-1/2, 3, 3-1/2, etc., up to the 8th order. This is shown in Illustration 5.
With the cursor on 1/2 order and the harmonic markers in place, ALL VIBRATION AT ENGINE RELATED FREQUENCIES HAS BEEN IDENTIFIED. Any spikes not marked with the cursor or a harmonic marker identify vibration coming from a source other than the engine. This could be any driven equipment including the engine fan (if so equipped).
If a spike occurs as noted above, remove the cursor and harmonic markers and locate the cursor on the spike which is not an integer multiple of 1/2 order and center it with the "." key. The exact frequency of the spike can then be noted. If the vibration level is unacceptable, the source of the vibration can be determined by looking for an attachment which is rotating at that frequency or which can produce that frequency. Knowing the rotating speeds of driven equipment, number of blades on a propeller or fan, gear ratios, etc. are helpful in identifying the source.
Spikes shown at very low frequencies may or may not represent real data. If the frequency is above the low cutoff frequency as set by the routes, the data may be real. If the level is of concern further study may be worth while. If the levels are low, this data should be ignored.
Two spikes very close together (e.g., 1/2 and 1 order) are the result of the characteristics of the LCD display and in most cases do not indicate two frequencies close together. Where two frequencies may be very close together (e.g., a marine gear ratio of 4.08 driving a 4 blade prop.) the vibration source may have to be determined by selectively disconnecting driven equipment.
Running A Speed Sweep
One of the most valuable tests that can be run to determine the cause of vibration problems is the "speed sweep". These tests are also called "run ups", "coast downs", and PEAK/PHASE measurements. Vibration at a given frequency, usually first order, is recorded along with RPM and phase angle. The results are plots of displacement vs. RPM and phase angle vs. RPM which indicate any speeds where resonant conditions occur.
Measurements required are vibration level (4C-5629 Velometer Pickup) and a once-per revolution signal into the TTL-TACH port of the analyzer. The once-per-revolution signal is provided by the 4C-6918 Photohead Pickup. Also required are the 4C-6916 Magnetic Base Group, the 4C-6917 Adapter Group, 4C-6919 Reflective Tape, and the 4C-6921 Adapter Cable. Power for the photo head is provided from the DC power port of the analyzer.
Increasing Vs. Decreasing Speed
Speed sweeps may be made by starting at a low RPM and increasing the speed or starting at a high RPM and decreasing the speed. Either method is acceptable even though the results usually differ slightly due to nonlinearities in the vibrating system. Nonlinearities are the result of springs which have spring rates which vary with displacement and damping (energy loss) inherent in all real systems.
Using the Trigger Function in Analyze Mode
The trigger function allows the analyzer to collect data only after levels reach a predetermined level (trigger level) or an external signal to the TTL TACH port starts data acquisition. The trigger function along with MONITOR SPECTRUM, ACQUIRE SPECTRUM, or MONITOR WAVEFORM is useful in determining the natural frequency of structures and mounted components or collecting data of a transient nature. Waveforms (in sensor units) can also be "captured" or monitored relative to a tachometer pulse from the MONITOR MODE, MONITOR WAVEFORM screen.
Complete balancing procedures can be found in LEBV0201 CSi Fast Bal 1 User Manual.
Balancing rotating machinery when attached to diesel engines can be a very frustrating exercise. Although the theory of balancing is relatively simple for simple systems, most systems are, in fact, quite complex.
Before beginning the balance job, it must be determined that unbalance is, in fact, the principle cause of the first order vibration. All attached machinery should be checked for proper alignment, bearings should be in good condition, etc. A problem in the engine fuel system can, in addition to producing half order forces, also produce first order forces which can, when occurring at a resonant frequency, cause high vibration. It is important that other potential causes are eliminated because the balance analyzer, by its design, assumes that any displacement occurring at the rotating speed is totally due to unbalance and makes the calculations accordingly.
Because most engine systems inherently exhibit some first order, those which contain a small amount of unbalance are more apt to be more difficult to balance than those which are extremely rough. In other words, if a vibration complaint leads to measurements indicating that the first order vibration is predominant and the system is just slightly over the acceptable limits, it is very possible that only a small part of the problem is due to rotating unbalance. In this case, trying to resolve the problem by balancing will probably be a frustrating exercise. It is very advisable in this case to be sure other causes have been checked out prior to balancing.
The vibration must be consistent from startup to startup. If the first order readings change after the engine has been stopped and restarted, relative motion is occurring in some rotating part and any attempt at balancing will fail.
Unbalance is insensitive to load; therefore, the first order reading should remain very nearly the same under both idle and loaded conditions.
One of the fundamental rules for most balancing techniques is that balancing CANNOT be accomplished at or close to a resonant condition. The reason for this is that balancing techniques rely on measuring both displacement and phase angle and at (or near) resonance, the phase angle changes rapidly and widely as a function of speed. Complex machinery often contains a number of resonances which, when every part is within tolerance and things are as they should be, the vibration level is acceptable. However, when an unbalance condition exists, these usually acceptable resonances can create much confusion when attempting to "in place" balance the rotating system.
For example, it is very possible for a diesel engine connected to a single bearing generator and mounted on a base to have a condition where an unbalance at the front of the engine results in unacceptable motion of the rear of the generator with relatively little motion at the front of the engine. The reason this can happen is that a resonant condition can exist where the rear of the generator responds to a cyclic force (at a resonant frequency) more than anything else in the system.
In technical terms, this is a "mode" of vibration where the "mode shape" has little motion at the front of the engine and a lot of motion at the rear of the generator. Most gen sets do, in fact, have a number of "modes" (resonant frequencies) each with a distinct "mode shape". Whenever a cyclic force with a frequency corresponding to one the modal resonant frequencies exists, the possibility of high vibration also exists.
Continuing the example, the rear of the generator could respond horizontally at one frequency and vertically at another and the two frequencies could be close together or not depending on the mass of the various components in the system and the stiffness of the interconnecting parts. In other words, there could be two "modes" having different resonant frequencies along with different "mode shapes".
Therefore, when attempting any balancing job, it is necessary to first determine if there are any resonant conditions to be taken into account when doing the balancing job. This is done by running a "speed sweep" while measuring displacement and phase angle at each of the possible measurement locations. Details on how to run a speed sweep are covered in the LEBV0404 CSi Model 2117 Machinery Analyzer User's Manual.
Any measurement point that exhibits evidence of being at or within 10% of a "resonant response" should not be used for balancing. Although it is best to balance at a speed where no resonances occur, sometimes the only option is to measure in a direction which does not respond to the resonance. (e.g., the rear of the generator is responding vertically but not horizontally).
After documenting the vibration characteristics, the next decision is whether to attempt single plane or multiple plane balancing. For a complex system such as a gen set, this is not always an easy decision. Experience with similar systems is probably the best guide in that if a prior problem required multiple plane balancing than the current one likely will as well. If no prior experience exists, then common sense and judgment must prevail. For example, if the answer is not clear cut and the rear of the gen set is readily accessible for trial weights, the obvious choice is to try a single plane balance at that location. If the balancing attempt does not quickly bring the desired result, then the more time consuming multiple plane balancing must be done.
Procedure for Two-Plane Balance
Learn as much about the motion of the system (engine, genset, etc.) as possible by acquiring data in the possible measurement locations. For two-plane balancing, the four possible locations are:
PLANE ONE - HORIZONTAL
PLANE ONE - VERTICAL
PLANE TWO - HORIZONTAL
PLANE TWO - VERTICAL
NOTE: The analyzer program refers to MEASurement POINTS A and B if 2 measurement points are specified on the DEFINE BALANCE JOB screen; A, B, C, and D if 4 are specified. Assignment of these points is arbitrary but must not change during the balance job.
The TRIM BALANCE procedure can be repeated as many times as needed to achieve the desired results. All weights are additive to those in place.
If satisfactory results are not achieved, a different set of measurement points or different speed must be selected. Reviewing the data recorded during the procedure can be helpful in assessing the effect of unbalance at the planes selected.
A Noteworthy Fact
Whereas the force due to a pure rotating unbalance increases in proportion to the square of the rotating speed, the displacement of a mass upon which that force is acting will, in the absence of resonance, be a constant (suspended free in space).
Monitor Wave Form
The trigger function can also be used to acquire waveforms. Settings in the ACQUIRE SPECTRUM trigger mode are carried over to the MONITOR WAVEFORM mode. An additional item, SWEEP SIZE, specifies the number of points to be captured. 50 is the minimum and 1024 is the maximum number. The time length of the waveform is determined by the following relationship:
In most AVSpare applications where it is desired to determine a structural natural frequency with an impact test, it is suggested that the MONITOR WAVEFORM be used first to determine the approximate values required for the TRIG LEVEL. By impacting the component or structure to be tested using the MONITOR WAVEFORM function, the signal can be observed and the TRIG LEVEL can most easily be adjusted to a suitable value. Then, change to the ACQUIRE SPECTRUM mode to capture a spectrum with the TRIG LEVEL as set in the MONITOR WAVEFORM mode.
Establishing acceptable vibration limits for AVSpare equipment has always been the subject of much debate as there is no absolute way to do so. In general, true limits could be summarized very simply - if there are no premature failures and no one complains, the vibration is acceptable. However, because people do complain, acceptability criteria have evolved to help resolve differences of opinion.
Past and current limits are established by the collection of much data and weighing the benefits of lower vibration levels relative to the associated costs. Additionally, aside from potentially damaging effects, the level of acceptability as perceived by the operator or customer changes as lower levels become more common. What this means is that what is acceptable today will probably not be acceptable in the future.
This manual includes three sets of limits. Two of these (for engines) have their beginnings related to gensets. The third addresses vibration as felt by operators of AVSpare equipment, primarily earth moving equipment.
The original engine limits were set up for gensets and were then extended to engines in general in the absence of other specific studies. AVSpare has now published new limits for gensets which have been published in the 3600 Engine Installation Guide. These are to be applied to all AVSpare gensets. Whether they become extended generally to other applications has not been determined. In the meantime, the older limits apply.
This manual will present and discuss each of the three current sets of limits and how to relate data to them.
For the sake of simplicity these will be referred to as Engine Vibration Limits, Genset Vibration Limits, and Operator Vibration Limits.
Illustration 6 on the next page shows the Engine Vibration Limits curves as shown in EDS 73.1. The top line is 5 mils peak to peak from low frequency to approximately 2400 CPM where it breaks to a constant velocity curve equal to .65 in/sec. peak. This curve applies to the engine structure and generator frame of an installed engine and is not to be applied to components or sheet metal. The curve represents the maximum allowed value for each individual spectral component (i.e., vibration at a single frequency). Above 2400 CPM (40 Hz), the allowable displacement decreases as a function of frequency according to a constant velocity curve. Note that any vibration displacement can be converted to an equivalent velocity at any given frequency by the following equation:
Velocity (in/sec peak)=Freq. (Hz) X Disp. (pk-pk) 318.3
To use this curve, first acquire data using the 169-0717 Vibration Analyzer. Then compare the individual spectral components (displacement at each frequency) to the curve. Above 40 Hz, convert the displacement to velocity. If any of the points fall above the curve, an isolated (slung) test should be run to determine the acceptability of the engine without any influence from mounting resonances, etc.
The "isolated engine" test is commonly referred to as the "slung engine" test because it is usually run by suspending the engine on a chain fall or other slinging device. Note that the engine must be TOTALLY suspended for the test to be valid. Suspending one end and leaving the other end mounted or sitting on a wooden block will lead to erroneous conclusions.
After the data is acquired, the same process as above is used to determine acceptability except that the 4 mil, 0.50 in/sec curve applies. Again, displacements at frequencies above 40 Hz must be converted to velocity.
Some of the routes supplied with the analyzer do have the 5 mil value as an Alarm Limit for some parameters in the parameter set. See Table 2, Alarm Limit Summary on page 48.
Illustration 6. Engine Vibration Limits.
- Acceleration -
- Rate of change of velocity.
- Alarm Limit -
- Level set to cause an alarm message to display on the LCD if the specified level is equalled or exceeded.
- Analysis Parameter Set -
- A set of parameters that determine the characteristics of a route point. Set up with MasterTrend.
- Balancer -
- Routing device that controls vibration by introducing forces opposed to those inherent in the engine.
- Bandwidth -
- A frequency range within which vibration will be measured.
- Baud -
- Units of data transmission over a RS232 serial communications link.
- Configure Port -
- Set the parameters for a RS232 serial port to make it compatible with a connecting device.
- Coupling -
- A torque transmitting device between rotating components in a system.
- CPM -
- Number of cycles of vibration that occur in one minute (Cycles Per Minute).
- Critical Speed -
- A speed at which resonance occurs.
- Cursor -
- A controllable figure (box) on the LCD that can be moved to determine values.
- Cyclic Irregularity -
- When an engine cylinder fires, the sudden torsional motion of the crankshaft is referred to as cyclic irregularity.
- Damper -
- A device attached to the front of an engine to control torsional motion by either energy absorption or a combination of tuning and energy absorption.
- Damping -
- A damping force (torque) is supplied by any portion of the vibrating system that absorbs energy as a result of the vibration.
- dB -
- A logarithmic unit of measurement used in vibration and acoustics to accommodate a wide variation of readings on a common scale. Ratio is relative to some base value.
- Default -
- Value which a function assumes in the absence of input from the user.
- Displacement -
- Measure of the excursion of motion of a vibrating object. Expressed in mils (.001 inch) or microns (.001 mm).
- Download -
- Transfer of program from host computer to analyzer.
- FFT -
- Fast Fourier Transform, a mathematical procedure to compute the sinusoidal vibrations which combine to form a complex vibration. Can be used on any input voltage to the vibration analyzer.
- Firing Frequency -
- The normal vibration frequency that is caused by the firing pattern of a specific engine. Generally speaking, this is equal to the rotational frequency multiplied by one half the number of cylinders.
- Forced Vibration -
- When vibration results from the application of an external periodic force. In a rotational system, torsional vibration results from the application of an external periodic torque.
- Free Vibration -
- Free vibration is that motion which takes place when an elastic system is displaced from its equilibrium position and released.
- Frequency -
- Frequency of motion is the number of times the motion repeats itself in a unit of time. It is the inverse of period for a sinusoidal motion.
- Fundamental -
- Lowest frequency in a periodic function. Period is equal to the period of the vibration.
- Fundamental Marker -
- Initial cursor set on a spectral peak on the LCD of the vibration analyzer.
- G's -
- Unit of measure of acceleration which is equal to the acceleration due to gravity.
- Harmonic -
- One of an integer numbered individual multiples of the fundamental frequency that combine to form a complex periodic waveform.
- Harmonic Markers -
- Cursors set on integral multiples of the frequency where the fundamental marker is set.
- Hertz -
- Measure of frequency in cycles per second.
- HFD -
- High Frequency Detection measures the acceleration of an object in 0's over a very high range of frequencies to detect impending failure. Not used by AVSpare.
- Isolation -
- Isolation is the reduction of transmitted vibration from one body to another by means of soft springs (isolators or mounts).
- Linear -
- With regard to plot format, provides uniform numerical increments of the level of a spectrum.
- Linear Vibration -
- Back and forth vibration of an object.
- Live-time Spectrum -
- Display that is updated after every measurement so the user can observe changes.
- Market -
- A group of routes for similar applications. Noted as "station" in the vibration analyzer. Mass-Weight of a body divided by the acceleration of gravity.
- Mass -
- Weight of a body divided by the acceleration of gravity.
- Mass-Elastic System -
- Combination of masses (or inertias) and springs that constitute a vibrating system.
- MasterTrend -
- A Computational Systems Inc. program for setting up routes and processing data for trend analysis.
- Measurement Point -
- A point on a route designated as a measurement location. Same as "route point".
- Ml -
- An English unit of measure of displacement equal to .03 mm (.001 inches.)
- Micron -
- A metric unit of measure of displacement equal to 0.001 mm. One micron equal 0.039 mils.
- Mode -
- A system composed of several masses has more than one natural frequency. Each natural frequency is referred to as a mode of vibration which has distinct pattern of motion.
- Mode Shape -
- The pattern of motion at the extremes.
- Modem -
- A device that allows transmission of data over phone lines.
- Moment of Inertia -
- Short for "mass polar moment of inertia" is the rotational counterpart of mass.
- Natural Frequency -
- The frequency of a free vibration is called a natural frequency of the system. Systems with many masses and springs can have many natural frequencies.
- Node -
- For any given mode of vibration there are points of no motion for that mode shape. Points of no motion are called nodes.
- Order -
- The order of a vibration is the number of times the vibration repeats itself relative to some reference frequency. The reference frequency is commonly engine rpm. Order = vibration frequency (CPM) divided by RPM.
- Overall -
- An indication of the total excursion of the complex vibration. In the vibration analyzer, the overall is computed by taking the square root of the sum of the squared values of all the spectral components over a specified frequency range.
- Parameter -
- A value input to the analyzer or calculated from the data.
- Parameter Set -
- Seven features of the data calculated and stored by the analyzer.
- Peak -
- Indication of level of vibration from the midpoint of travel to one extreme.
- Peak-to Peak
- Indication of level of vibration from one extreme to the other.
- Period -
- Time required to complete one cycle of vibration.
- Periodic Motion -
- Motion which repeats itself in all details in a definite interval of time (period).
- Phase Angle -
- Number of degrees that a vibration leads or lags some reference mark or another vibration. One cycle equals 360 degrees.
- Predictive Maintenance -
- Technology for predicting machine failure based on increase in vibration at predetermined frequencies.
- Real-time -
- Data displayed as it is being measured.
- Resonance -
- When a system is acted upon by an external periodic force (or torque) having the same frequency as the natural frequency of the system, the amplitude of the system can become very large, and the system is said to be in a state of resonance.
- Route -
- A set of predetermined measurement points on a specified machine.
- RS232 -
- Defines a standard serial communications port.
- Spectrum -
- A display of the spectral peaks (level and frequency) over a frequency range.
- Stiffness -
- Resistance of a spring or component to deflection under the action of a force (or torque).
- Torsional Vibration -
- Instantaneous change in RPM of a rotational system measured in degrees.
- Transient Vibration -
- Vibration that is not constant over a sustained period of time.
- Trend Analysis -
- Inspecting vibration data taken over a period of time to detect changes which may indicate impending failure of components.
- Trigger -
- An external signal which tells the analyzer when to start processing data.
- Tuning -
- Tuning is the process of altering the natural frequency of a mass-elastic system by changing either mass or stiffness.
- Velocity -
- Rate of change of displacement expressed as inches per second or millimeters per second.
- Vibration -
- A body or machine is said to vibrate when it executes a periodic motion about a position of equilibrium. Linear vibration is motion in straight line; torsional vibration involves a twisting or rotational motion.
- Waveform -
- Graphical representation of vibration on a time axis.
- Window -
- An Fast Fourier Transform averaging technique that adjusts data in a spectrum to account for the fact that only a portion of the data is being analyzed.
Genset Vibration Limits
In 1991, new vibration limits were established for AVSpare Engine-Generator sets. The new limits recognize the changing requirements worldwide along with the capability to customize the 169-0717 Vibration Analyzer with appropriate routes. The new limits along with the measurement locations and conditions are shown in Illustration 7.
Half and first order have specific values (5 mils) whereas the higher orders are accounted for by the two "overall" values taken over a specific frequency range (.4 through 8 order). Data is taken at 8 specific locations at rated load and speed.
Note that the "overall" displacement limit is not the same as appears on the LCD of the a analyzer at the completion of data acquisition. While both are calculated as the square root of the sum of squared spectral components, the frequency range of the spectra are not the same. The overall displayed on the LCD is calculated from a wider frequency range than the one in the limits and will usually be significantly higher.
The Genset Limits are measured using routes specifically designed for that purpose and are located in the EPG market (station). They are labeled Genset-NL1 through Genset-NL5. A complete description is included in the Routes Documentation of this manual.
Alarms are built into the routes to signal the user when a limit has been exceeded (Analysis Parameter Set 23, Alarm Limit Set 11).
Illustration 7. Genset Vibration Limits.
Operator Vibration Limits
Operator vibration limits are the most subjective in that they relate totally to human perception. Measurements in this instance are totally in units of velocity because perceived vibration tends to be constant over a wide frequency range when velocity units are used.
The limit curves shown in Illustration 8 are those used in evaluating AVSpare captive vehicles during development and have evolved over a number of years. It should be pointed out that some operators will complain about vibration levels lower than indicated as problems and others will tolerate levels well above the complaint curve. The curves do, however, provide a "bench mark" against which to make a judgment. Within reason, the operator's perception is the final limit.
The Captive Vehicle and On-Highway Truck routes have several points specifically for operator measurements. The limits have been included as alarms on the route points and will alert the user when a limit has been exceeded to aid in identifying a possible source. Note that Alarm Limit Set 13 has very low values and is used on the steering wheel route points where tolerance to vibration may be lower.
Illustration 8. Operator Vibration Limits.
This section documents the routes included in the 169-0720 Vibration Analyzer Group. In addition to improving the efficiency of the data acquisition process by suggesting measurement locations, the routes also influence the characteristics of the measurements taken by the 169-0717 Vibration Analyzer.
Many of the routes are tailored for general diagnostic measurements on specific types of machines. Others are set up to provide very specialized information in particular situations.
For example, if a genset is to be evaluated relative to certain limits, a route set up specifically for that application is needed. Because a cab vibration complaint requires measurements in velocity units, a route set up for that application should be used. Other situations may exist for which none of the routes adequately match the situation. In that case, the OFF-ROUTE mode of data collection should be used.
To use the OFF-ROUTE mode the user must have a fundamental knowledge of the routes and how they influence the results.
A route is a set of predetermined, suggested measurement locations (route points). Each route point has attached to it certain characteristics which were programmed into it when it was created.
NOTE: Routes are created with a Computational Systems Inc. program called "MasterTrend," a large complex program developed primarily for predictive maintenance. Some of the route terminology seen on the analyzer screen comes from the predictive maintenance application of the tool (e.g., "station" vs. "market"). The user should not be confused by the different terminology.
Common to all route points in the database LIN33.DAT are:
- 1. Resolution of the Analyzer (400 lines)
- 2. Averaging method (NORMAL)
- 3. Number of samples in final spectrum (6)
- 4. Data sampling window type (Hanning)
- 5. What data is automatically stored (SPECTRUM, PARAMETER SET)
- 6. NOTES
- 2. Averaging method (NORMAL)
Features of each route point that may or may not be the same as other route points are:
- 1. Whether measurement is frequency or order based
- 2. Frequency bandwidth (frequency range)
- 3. Units (displacement, velocity, acceleration)
- 4. Features of the stored PARAMETER SET
- 5. Sensor sensitivity (0.1 for 4C-5629, 0.01 for 4C-3032)
- 6. Level that will trigger a "STATUS-VIB. ALARM" message on the analyzer LCD at the completion of data storage
- 2. Frequency bandwidth (frequency range)
These features are determined by the assignment of an ANALYSIS PARAMETER SET and an ALARM LIMIT SET to each route point. The database LIN.DAT contains five Analysis Parameter Sets and six Alarm Limit Sets.
Analysis Parameter Set (APS)
As stated above, certain features are common to all route points in the database. Only the variable features of each of the Analysis Parameter Sets will be discussed in detail in this manual.
Seven stored features of the data (known simply as the PARAMETER SET when displayed by the analyzer) are influenced by the APS. These are the OVERALL value and six other parameters. The OVERALL value is always stored and the APS simply determines the units and the range of frequencies (bandwidth) included in the value.
The six parameters are defined by label as to what they represent along with the units and bandwidth. They are usually labeled as either orders or frequency bands. The exception is in APS 23 which has 2 parameters labeled as OVERALL DISP and OVERALL VEL.
Table 1 is a summary of all of the ANALYSIS PARAMETER SETS which shows those parameters which are not common to all route points.
Alarm Limit Set (ALS)
The ALARM LIMIT concept is oriented primarily toward the predictive maintenance application of vibration measurements. However, the alarm limits can also be useful in diagnostic work because they can be used to highlight a spectral component that may require further investigation.
NOTE: Table 2 in the Table Information Section shows the Alarm Limits for each of the Alarm Limit Sets included in the Database LIN33.DAT.
When attached to a route point, the alarm limit signals the user by displaying a message if a parameter value is equal to or higher than that set to trigger the alarm. This is demonstrated in Illustrations 9.
Illustration 10 shows a typical LCD display at the completion of data collection on a route point. Note the STATUS=OK message which indicates that no alarms were triggered.
Illustration 10 shows the LCD when an alarm has been triggered. The message now is STATUS=VIB. ALARM which indicates that some predetermined level has been met or exceeded. To find out what triggered the alarm, the user must display the stored parameters.
The analyzer determines the OVERALL value by calculating the square root of the sum of the squared values of all the spectral components over a specified frequency range. In the case of an order based APS, this is determined by a specified low frequency and the frequency of the highest specified order at the measurement RPM.
At 1800 RPM, the OVERALL value will be the square root of the sum of the squared spectral components for all frequencies between 180 (3 Hz X 60) and 14400 (8 X 1800) cpm. The measurement RPM determines the upper frequency but the lower frequency is fixed.
For the other six parameters, if the APS is order based, the bandwidth is expressed in the form of orders on either side of the labeled order so as to create a "tolerance". This allows for minor speed variations at the time of measurement. The vibration characteristics of AVSpare equipment are such that an order based parameter usually contains only one significant spectral component and the stored parameter value will be very nearly equal to the corresponding spectral component of the spectrum.
If the bandwidth is frequency based, then the stored parameter includes all of the spectral "energy" in that band (sq. rt. of sum of sq.). Values of the individual spectral components which contribute to the stored parameter value will have to be read from the corresponding spectrum.
To do this, press the ANALYZE key, highlight 3) DISPLAY PARAMETERS, and press ENTER to get the screen shown in Illustration 11. Note that "1 ORDER .347" is highlighted indicating that the vibration level at first order has caused the STATUS=VIB. ALARM message.
Setting Alarm Limits
Alarm limits are assigned to a route point by assigning both an Analysis Parameter Set and an Alarm Limit Set (ALS) to it. Alarm Limits always correspond to some Parameter Set.
NOTE: Table 2 shows the Alarm Limits for each of the Alarm Limit Sets included in the Database LIN33.DAT.
Note that the OVERALL and the six parameters of the Analysis Parameter Set each have an assigned alarm level. In all cases, the level for the OVERALL is set high enough that the alarm should never be triggered because it would serve no useful purpose.
The alarm levels for the six parameters are set at values which have some relationship to either established factory limits or values which are commonly used as acceptability guidelines. For example, assigning Analysis Parameter Set 20 "Engine Orders by CSTG" along with Alarm Limit Set #8 to a route point will cause an alarm message to be displayed if any one or more of the following conditions are met:
In another combination, APS 24 "Operator Station" and ALS #12 will trigger the alarm message for the following conditions:
In the first example, the alarm is triggered on displacement levels which are typically acceptable for engine measurements. For the second example, the alarm is set to trigger on velocity levels which are unacceptable to the vehicle operator. Other combinations, of course, produce different results.
Database LIN33.DAT contains 26 different routes divided according to 6 MARKETS (or STATIONS). These are summarized in Table 3 in the Table Information Section.
For all of the MARKETS except EPG ENGINES, all of the routes in a MARKET are identical except the machine identification which appears on each route point. The market EPG ENGINES contains two route groups where the routes within each group are identical.
One group of routes (e.g., EPG NO1) has a structure similar to the other general diagnostic routes and the other group (e.g., GENSET- NL1) is structured to compare vibration levels to current AVSpare acceptability criteria. A sample of each of the 7 different route structures is included in the Sample Route Structures section in this manual for reference. By looking at a sample route structure, the user can determine what the characteristics of the measurements will be for each route point.
A sample of each of the 7 different route structures is included in the Sample Route Structures section in this manual for reference. By looking at a sample route structure, the user can determine what the characteristics of the measurements will be for each route point.
Sample Route Structures
Off-Highway Truck No. 1
Industrial Engine No. 1
EPG Genset New Limits
Marine Propulsion Engines
Captive Vehicle Engine/Cab
This group is not serviced through the normal parts distribution channels. For ordering instructions or additional information, contact the CSTG Hotline.
For information on service tools or shop supplies contact AVSpare Service Technology Group on:AVSpare Service Technology
501 S.W. Jefferson Ave.
Peoria, Illinois 61630-2184
[email protected] (Email)
orAVSpare Service Technology
AVSpare Overseas S.A.
P.O. Box 6000
1211 Geneva 6
+41 (79) 217 27 45 (Geneva Phone)
+41 (22) 849 49 29 (Geneva Fax)
36CSTG (COSA E-Mail Address)