Field balancing in the real world
Contents
1. Scale os A m 15 19 16 Qo 16 19 10 Possible resonance at 543 onders 16 19 08 OVRALL 3777 V DG PK 3779 LOAD 400 0 318 ips Before Balancing RPM 1250 RPS 2083 3 a F p gt 16 19 02 16 42 24 0 2 4 68 12 16 Frequency in Order Labsi Cascade Piot with Reference o i 2 3 4 6 6 Frequency in Order Label Resonance Directional Fig 3 Initial spectrum Fig 4 Selected cascade spectra Decision to Balance The highest magnitude of our data set was the 1x in Fig 3 at 318 ips peak velocity This represented about 80 of the total with some subsynchronous energy lt 1x frequencies and the remainder mostly synchronous energy whole number multiples of 1x running speed frequencies The cascade spectra from the coastdown Fig 4 provided further assurance we could significantly decrease the vibration by balancing The only possible resonance was at 543x running speed or slightly greater than 675 rpm so it would have no adverse effects on our balancing Also although difficult to see the 1x peak continues to decrease in magnitude as the fan slows down This is a sure sign that field balancing can reduce vibration magnitude Sounds good huh Well the problem was that this fan did NOT have an access to the fan rotor or fan wheel if you prefer The consultant was confident that our diagnosis was correct and that we could reduce the vibration A cover was made a hole was cut in the fan hous2. OAK RIDGE NATIONAL LABORATORY ORNL CP 94697 C E a e FIELD BALANCING IN THE REAL WORLD PREPARED FOR RECEIVED CSI RELIABILITY WEEK ee OCTOBER 13 16 1997 OSTI OPRYLAND HOTEL NASHVILLE TN BY BOB BRACHER k NT IS UNLIMITED M AS TE R DISTRIBUTION OF THIS DOCUME iin DISCLAIMER Portions of this document may be illegible in electronic image products Images are produced from the best available original document ors DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government Neither the United States Government nor any agency thereof nor any of their employees make any warranty express or implied or assumes any legal liabili ty or responsibility for the accuracy completeness or usefulness of any information appa ratus product or process disclosed or represents that its use would not infringe privately owned rights Reference herein to any specific commercial product process or service by trade name trademark manufacturer or otherwise does not necessarily constitute or imply its endorsement recommendation or favoring by the United States Government or any agency thereof The views and opinions of authors expressed herein do not necessar ily state or reflect those of the United States Government or any agency thereof Plant amp Equipment Division ORNL Abstract Field Balancing in the Real World Field balancing can achieve sign
3. of these things are true the decision to field balance ought to be fairly easy to make from one set of data Other Factors The problem arises when the forcing functions causing excessive 1x peaks are examined Some such as 1 bent shaft 2 eccentricity and 3 unbalance center of gravity and center of rotation do not coincide will respond to field balancing Others such as 4 severe looseness 5 resonance near running speed and 6 cracked shaft will not respond successfully to field balancing To complicate matters misalignment can be mistaken for unbalance and unbalance can be mistaken for misalignment Misalignment can exhibit a 1x peak only An overhung rotor can exhibit a high 1x in the axial direction or the radial direction as well as a high 2x running speed peak Additional Tests to Confirm Unbalance There are several ways to confirm that a field balance correction would decrease the vibration in rotating machinery 1 On a single plane rotor phase data between the two bearings can help to confirm an unbalance condition If the vibration of the two bearings is in phase it is likely unbalance rather than misalignment If the vibration is 180 degrees out of phase the problem is likely misalignment 2 Bump tests can rule out resonance within 10 20 of running speed difficult or impossible to balance successfully 3 Waterfall or cascade plots of coastdown and runup data can also help All of the tests mentioned can
4. 100 0 RPM 3620 RPS 58 66 0 06 10 16 20 26 30 35 40 45 Frequency in Order WAVEFORM DISPLAY 27 SEP 26 14 18 RMS 0940 PK 2595 PK 2306 CRESTF 2 76 O 02 04 08 08 10 12 14 16 Time in Seconds 7803 Whirlex Exhaust Fan SF 2 7503 16580 FIH Fan inboard Horizontal ROUTE SPECTRUM O6 MAR ST 14 49 OVRALL 1517 V DG PK 1560 LOAD 100 0 RPM 1250 RPS 2083 3 4 WAVEFORM DISPLAY O6 MAR O87 14 49 RMS 0388 PK 0999 PK 4 1226 CRESTF 3 16 0 18 25 Time in Seconds Label Belts Faulty Beit 2649 Evaporator Exhaust Fan 48 ona 2649 4B Lo MOH Motor Outboard Horizontal See 0 12 29 JUL 86 13 13 PK 4578 0 10 LOAD 100 0 RPM 3660 008 RPS 59 33 006 PK Velocity in in Sec 004 0 os 18 Frequency in Order Label Bump Test Fan Not Running Fig 15 Bump test resonance at 1 1x Plant amp Equipment Division ORNL 3039 3039 00125 ORR CELLVENT STBY 3039 3039 00125 ORR CELLVENT STBY TS FOR Fan Outboard Horizontal TS FOH Fan Outboard Horizontal ROUTE SPECTRUM 26 MAR S7 12 41 OVRALL 4 54 V DG PK 152 LOAD 100 0 RPM 2997 RPS 49 96 PK invsec 15 26 36 Frequency in Order WAVEFORM DISPLAY 26 MARS7 12 41 RMS 14 17 PK 2 69 PKJ 2 03 CRESTF 2 29 Y eG u 3 lt Time in Seconds Label Turbine Fan Before Balancing Fig 16 Case History Three 11 PK ivsec k o Pr amp lt ery E 15 25 35 45 Freq
5. For a single plane balance SCREEN S should look like the one below when you finish 4 SCREEN T displays Select the rotation of the machine from your preferred point of view Set tach angle RPM deviation DELTA and RPM1 NOTE in most cases only 1 RPM is required TIP While in the FAST Bal If program the RESET key will always return you to the BALANCE FUNCTIONS screen SCREEN QO The routine routes are unavailable until you EXIT What to Do to EXIT FAST Bal II 1 Reminder See CARD 6 for more information Go to UTILITY FUNCTION menu SCREEN C and select Item 6 SPECIAL FUNCTIONS SCREEN O displays 2 Select Item 3 EXIT DWNLD PROG and exit the program The analyzer will return to a machine point on a route if loaded TIP The DELE key will always take you to the previous screen while you are in JOB DEFINITION BALANCE FUNCTIONS 11 J08 DEFINITION 1 3 CORRECTION WEIGHTS MACH ID 2660 B1109 4 TOLERANCE CHECK TRIM 1j MACH DESC TEST STAND BALy 3 OPTIONS STATION 2668 PRESS lt KEYPAD FOR HELP HAT W S SCREEN Q SCREEN R DEFINE BALANCE JOB HEIGHT PLANES MEASUREMENT PLANES tee POINTS JOB DEFINITION CLEAR JOB NO USER RKB JOBE il DEFINE TACH OPTIONS e ANGLE IEG TIO 9 ENTER BALANCE RPM VALUES MEASUREMEN ELTA T SPEEDS 8 zh DISCRETE MELGHT POSITIONS F ROTATION SCREEN S SCREEN T Bob Bracher Vibration amp Training 14 Plant amp Equipment Div
6. MAKE MEASUREMENT Part 2 What to Do continued from CARD 9 How to Do It 1 After completing measurements SCREEN Z displays PROCEED 2 Ifthere were no potential problems SCREEN Y displays Go to TRIAL RUN CARD 11 TIP The Reference Run data is analyzed and you will be alerted to conditions posing potential problems Read all the screens and make your best judgment whether or not to continue If preliminary checklist was completed balancing should proceed SEE EXAMPLE BELOW What to Do if you get a USER ALERT How to Do It 1 SCREEN A2 is one of many screens that may display Note the problem go to the HELP MESSAGE SCREEN A3 for more information 2 After assessing messages Go to TRIAL RUN CARD 11 TIP The DELE key will always take you to the previous screen while you are in JOB DEFINITION The RESET key returns you to BALANCE FUNCTIONS SELECT MEASUREMENT REMINDER MUX IS ENABLED SELECT MEAS POINT MPT CH SPEED MAG PHASE 1772 A Tei 34l 1771 185 re 2 TRIAL RUN J SCREEN Z SCREEN Y USER ALERT tt REFERENCE DATA 1X EE IS lt S02 OF TOTAL VIBRATORY ERGY AT PLANE i IBH IBU PLANE 2 OBH OBU HELP 1X RPM US OVERALL RE r AN DE Be DP AERES LANTIS ETERMINE WHAT OTHER NT SENTER gt KEY TO RETURN SCREEN A3 SCREEN A2 Bob Bracher Vibration amp Training 20 Plant amp Equipment Division SCREEN INFORMATION Card 10 SCREEN Y SELE
7. Outboard Horizontal g Route Spectrum ZE MAR ST 12 41 3039 3039 00125 ORR CELLVENT STBY TS _ FOH Fan Outboard Horizontal Route Spectrum GI MAY87 12 07 OVRALL 2907 V DG PK 3224 RPM 2997 RPS 43 96 S 2 x x 39 60 Frequency In Order Label Turbine Fan Before Balancing 62 Frequency In Order Label Turbine Fan After Balancing Fig 8 Initial baselining the hard way Fig 9 Final spectrum Decision to Balance The fan was exhibiting a 1x peak with a magnitude gt 85 of the overall vibration and it was very high Misalignment was not immediately suspected because the turbine was just rebuilt Fan operation was improved but excessive vibration was noticeable Other Problems This fan was difficult to balance because of the underlying misalignment and we wound up with three weights in each plane Using the Add Weights feature in the FAST Bal II software we calculated a single correction weight for each of two weight planes and the weights were welded in place After balancing the misalignment was evident Fig 9 However the customer was happy the operators on the job said this fan had never run this smoothly and the vibration was reduced by gt 5 times a significant improvement The machine awaits alignment when time permits If pressed into service now however it would run much longer than before it was balanced Bob Bracher Vibration and Training 8 Plant amp Equipment Di
8. of other vibration problems A demonstration will explain by example the cases presented here ORNL Journeyman Millwright Doug Edwards has agreed to assist me with this demonstration I am grateful to him for his enthusiasm skill and dedication to predictive and proactive maintenance technologies I enjoy working with him and I think you will too Overview List of CSI Equipment Used Field Balancing Basics Decision to Field Balance Field Balancing Guidelines Case History One The Underbalanced Overfire Blower Case History Two The Confident Consultant Case History Three The Doubtful Backup Demonstration of Multiple Halas Summary Recommendations References Appendices A amp B VVVVVVVVVVVY List of CSI Equipment Used CSI 2115 Machinery Analyzer a single channel analyzer CSI 404 Infrared Phototach CSI 440 Strobe Package CSI FAST Bal II Downloadable Program CSI Cascade Downloadable Program gt gt gt gt gt Bob Bracher Vibration and Training 2 Plant amp Equipment Division ORNL Field Balancing Basics Decision to Field Balance Appearance of Unbalance Signature The 1x magnitude is always increased with an unbalanced condition in rotating machinery and it is usually highest in the radial direction A single peak of excessive vibration at 1x running speed or 1 order is the classic unbalance signature An accompanying waveform with a nearly perfect sine wave all but confirms it right If all
9. of this balance job If it is a full balance job the last reading will be compared to the REFERNCE RUN If it is a Trim only balance job it will be compared to the first reading of the Trim only SPEC This compares the last reading to the balance specification as defined for this job Technical Training Department 10 96 27 Technical Training Department
10. you will get better results if you do CARD 13 describes how to record the actual applied weight and location What to Do to alternatives to STEP 2 above 2 After completing STEP 1 above SCREEN A6 displays To Add weight with trial weights removed 2 After completing STEP 1 above SCREEN A6 displays To R ight with trial weights removed lt PAGE gt ADD REMOVE 2 After completing STEP 1 above SCREEN A6 displays To Remove weight with trial weights left on lt PAGE gt _and toggle TIP It is not possible to show all of the incident display screens for the various setups in FAST BAL H so READ EACH SCREEN CAREFULLY and complete information accurately ae PALACE PONG TIONS CORRECTION HEIGHTS HACH ID 2668 81185 1 JOR DEFINITION X 3 CORRECTION HEIGHTS O 3 OPTIONS PRESS lt KEVPAD gt FOR HELF SCREEN Q ar LANCE FUNCT TOMS HACH ID 2665 81105 1 JOB DEFINITION X a atk EE X Pii WEIGHT 0 17 LOCATION 49 HEIGHT 0 03 ror LOCATION alg FAGE ADT REMOVE TH IS ON lt t 43 0FF SCREEN A6 TOLERANCE CHECK TRIM REMINDER MUS IS ENABLED 1 APPLIED HELGHT URE 4 TOLERANCE CHECK TRIM 3 TRIM CORRECTION FRESS KEYPAD FOR HELF SCREEN Q SCREEN A7 Bob Bracher Vibration amp Training 24 Plant amp Equipment Division SCREEN INFORMATION Card 12 SCREEN Q see CARD 7 SCREEN A6 Vector s show the location relative to the tach position T of th
11. 15 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 8 Field Balancing with FAST Bal Il JOB DEFINITION Part 2 What to Do continued fromCARD7 ss Howto Dott hee a a ae ee ae ae 1 Complete DEFINE BALANCE SENSOR screen SCREEN U accurately NOTE See SCREEN U below for usual setup 2 SCREEN V displays Define rotation sensor point identification by channel and sensor location from TDC for MEASUREMENT PLANE 1 3 SCREEN W displays Define rotation sensor point identification by channel and sensor location from TDC for MEASUREMENT PLANE 2 TIP The displayed screen setups may be used as they are if appropriate or you may reset according to your personal preference and point of view Setup reference accuracy is a must 4 SCREEN X displays Confirm rotation and select number of weight positions numbering with reference to rotation and duplicate plane option If option is NO and gt 1 plane to define go to Item 11 below 5 Complete the screen DEFINE WEIGHT PLANE 2 not shown TIP The DELE key will always take you to the previous screen while you are in aJ OB DEFINITION The RESET key returns you to BALANCE FUNCTIONS DEFINE MEASUREMENT PLANE 1 Toc NUMBER OF POINTS 2 i ANGLE CH RADY SYN Tt ag FE r oe D SCREEN V DEFINE BALANCE SENSOR SENSOR TYPE ACCEL SENSITIVITY 8 1000 CONVERT TO VELOCITY DATA UNITS STANDARD a POUR iji SCREEN U DEFINE MEASU
12. AREFULLY and complete information accurately APPLIED WEIGHTS PAGE RESIDUAL VI TOLERANCE CHECK TRIM REMINDER MUK IS ENABLED Pi CHECK RUN 01 WEIGHT 5 LOCATION MIGHT 0 08 s r LOCATION ag SCREEN A8 SCREEN A7 TOLERANCE cE pi a ATIQH PT IPT ky r G MUN Ste olb 0 00690 87 9 HELP TOLERANCE CHECK S_THE RESULTS OF THE LAST TRIM RUN THE PER CENT OF REDUCTION COMPARED INITIAL RUN AND THE PER CENT OF AL_VALUES COMPARED TO THE TOLERANCE CATION H D aU A N E I F MPT Tife D_OF LINE COMING FROM SYMBO CATION OF CACHOnE TER REFERENCE ARROS CHANGE SCALING o BY A 8549 A 69 FRESS ZENTER KEY TO RETURN ROT SCREEN A3 SCREEN A9 Y G N I S L T N Bob Bracher Vibration amp Training 26 Plant amp Equipment Division SCREEN INFORMATION Card 13 SCREEN A8 APPLIED WEIGHTS PAGE RESIDUAL VIBRATION This is a reminder to let you know you may view a prediction of the residual vibration before actually performing the vibration check This is especially useful if you applied weight differing from the correction weight recommendation i Vector s show the location relative to the tach position T of the trial weights for this weight plane P1 D Identifies PLANE 1 with Discrete Weight Positions selected in a previous setup screen P1 C NOT SHOWN Identifies PLANE 1 with Continuous Weight Positions selected P2 D P2 C NOT SHOWN Same as above b
13. CT MEASUREMENT NOTE The display for SCREEN Y on the other side is for a single plane balance with no correction for runout Normally correction for runout is not necessary unless you are using a displacement probe 1 REFERENCE RUN Data is collected with no weights added When the reference run is complete an X appears next to it on the screen However you may retake any data necessary 2 TRIAL RUN 1 After collecting reference run data a trial run is performed with weights added in the weight plane If two plane balancing is performed a TRIAL RUN 2 will display also In that case the second trial run will be made by adding weights to the second weight plane and removing normally the weights from weight plane 1 SCREEN Z SELECT MEAS POINT CAUTION Be sure to check that your measurement sensor location matches the description for the channel collecting data Data will be invalid otherwise SCREEN A2 USER ALERTI NOTE This is just one of many USER ALERT screens which may display to help you determine whether or not balancing will correct the vibration problem This particular screen is alerting to the fact that lt 50 of the total vibration energy is due to 1x rpm but this exists only at one point OBH in plane 2 Use this information along with the HELP screen information to determine whether or not to continue balancing Normally you would continue especially if the balancing checklist was completed and unbalance
14. REEN Y displays with TRIAL RUN 1 X and TRIAL RUN 2 will be bee to run To complete follow the steps above again N NOTE Sc ill be slig fully TIP a possible to show all of the incident display screens for the various setups in BAL II so READ EACH SCREEN CAREFULLY and complete information accurately TRIAL RUN 1 WEIGHTS P10 HEIGHT 9 14 LOCATION a HEIGHT LOCATION SCREEN A4 SCREEN Al SELECT MEAS POINT MPT CH SPEED MAG PHASE IBH 1 1780 0 6363 337 IBU 2 1778 0 136 134 OBH 3 1773 0 0474 338 i l PROCEED T NEXT STEP SCREEN Z SCREEN A5 Bob Bracher Vibration amp Training 22 PRESS ENTER TO REMINDER REMOVE TRIAL WEIGHTS OR INCLUDE THEM IN NEXT TRIAL DEFINITION Plant amp Equipment Division SCREEN INFORMATION Card 11 SCREEN A4 TRIAL RUN 1 WEIGHTS Vector s show the location relative to the tach position T of the trial weights for this weight plane P1 D Identifies PLANE 1 with Discrete Weight Positions selected in a previous setup screen P1 C NOT SHOWN Identifies PLANE 1 with Continuous Weight Positions selected P2 D P2 C NOT SHOWN Same as above but for the second weight plane CAUTION Perform trial runs by adding trial weights to only one weight plane at atime you may remove the trial weights from the first run or leave them on but be sure the program knows what you did WEIGHT 0 14 This tells the quantity of weight whether ounce
15. REMENT PLANE 2 moc NUMBER OF POINTS 2 og a CH RADY SYN TIC AIAL FE 0 RAD o RAD o SCREEN W gt ROTATION DEFINE WEIGHT PLANE 1 WEIGHT POSITIONS lt 1 z 1ST POSITION ANGLE POSITIONS NUMBERED AGAINST ROTATION YES aaa DUPLICATE THE PLANE NO SCREEN X gt ROTATION Bob Bracher Vibration amp Training 16 Plant amp Equipment Division SCREEN INFORMATION Card 8 SCREEN U DEFINE BALANCE SENSOR 1 SENSOR TYPE Toggle among accelerometer displacement velocity and non standard 2 SENSITIVITY Enter the sensitivity in volts per engineering unit Check sensor or chart 3 CONVERT TO Toggle among choices to select sensor output Normally set to VELOCITY 4 DATA UNITS The default is STANDARD Rarely will this require changing 5 SENSOR POWER Toggle between ON and OFF Most of our sensors require this to be set to ON 6 MUX ENABLED Toggle among ON OFF and AUTO If using the CS7 MODEL 642 Multiplexer this must be set to ON or AUTO In AUTO the analyzer will read all channels consecutively and accept data automatically If you want data accepted in AUTO before the analyzer accepts it you can force acceptance by pressing ENTER SCREEN V amp SCREEN W DEFINE MEASUREMENT PLANE 1 and PLANE 2 NOTE Each measurement plane can have up to 3 sensors defined with not more than one axial per plane Accuracy with regard to TDC and TACH reference are necessary for correct calculati
16. ault is YES 5 DUPLICATE THE PLANE Toggle YES NO A YES will cause all other weight planes to be duplicates of PLANE 1 SCREEN not shown DEFINE WEIGHT PLANE 2 NOTE It is possible to have two weight planes one with discrete weight positions and one without as in a fan rotor with a backing plate and blades attached to it normally a single plane balance situation but it could be two plane balanced if necessary In cases such as this define the additional planes as above P amp E Technical Training Department 10 96 17 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 9 Field Balancing with FAST Bal Il MAKE MEASUREMENT Part 1 What to Do continued fromCARD8 Mow to Dott 1 After defining the job SCREEN Q displays Go to MAKE MEASUREMENT 2 SCREEN Y displays select REFERENCE RUN 3 SCREEN Z displays take measurements at the accelerometer points listed In AUTO mode see MUX CARD 8 the analyzer will take all the readings and accept them when Data Stability is in GOOD range TIP You can override analyzer by pressing the ENTER key during measurement to accept data What to Do if you must take a measurement again How to Do It 1 Go back to SCREEN Z highlight the identity of the measurement to be repeated take the measurement again 2 SCREEN A1 displays wait until data for MAG amplitude and PHASE are stable then ACCEPT the data TIP DELE key takes
17. be performed with a single channel analyzer such as CSI s 2115 and a tach trigger A Note on the CSI Cascade Downloadable Program When properly set up and operated this program and the cascade plots produced can provide a wealth of reliable information quickly CSP s Cascade Downloadable Program can reveal a resonant frequency too close to running speed some transient events and magnitude in relation to varying running speeds Balancing Standards The decision to balance must take into consideration some standard that can be met Currently the primary standard used on commercial fans and pumps at ORNL is customer satisfaction Objective standards for assessing field balancing results can be stated in maximum ounce or pound inches of residual unbalance remaining or they can be stated in terms of a vibration magnitude limit at a certain location at 1x turning speed Balancing standards will vary greatly with application consequences of a machine failure and customer requirements The balancing of rigid rotors is covered in ANSI Standard S2 19 1989 3 Technical Training Department Field Balancing in the Real World Field Balancing Guidelines L Preliminary Checks 1 H Complete Safety Work Permit according to YOUR COMPANY S procedure 2 Lockout tagout equipment according to YOUR COMPANY S procedure 3 OI Inspect machine to be balanced even ifit has already been inspected for any of the following problems that could preclud
18. e a satisfactory balance of the machine Cracks in foundation grouting welds mounting hardware rotor etc Loose mounting bolts debris hardware bearings or couplings Missing parts keys set screws balance weights etc Damaged or broken parts coupling belts bearings etc Deformed parts bent blade misshapen belts etc Discoloration of moving parts Excessive wear of visible moving parts Too much too little or burnt lubrication Dirt or debris on rotor If any of the above items were checked and not corrected report findings Clean the rotor of the machine to be balanced if it is dirty OO Beano wp cogau 4 5 IL Typical Machinery Vibration Analyzer Equipment Setup 1 2 3 4 5 6 CAUTION From this point on permits and lockout tagouts may need to be suspended temporarily and then reinstated until the field balancing job is complete Follow YOUR COMPANY S procedures Mount two vibration transducers radially at each bearing Install reflector tape for PhotoTach reference on shaft connected to rotor Mount PhotoTach to read reflector tape on center and perpendicular to rotor shaft axis Connect Phototach multiplexer and cabling to machinery analyzer and accelerometers Set up the job in the machinery analyzer Ensure that cords accelerometers and equipment will not interfere with shaft rotation OO00O 0 applicable to this job Actual step by step of balance job will vary H Typical Ste
19. e trial weights for this weight plane P1 D Identifies PLANE 1 with Discrete Weight Positions selected in a previous setup screen P1 C NOT SHOWN Identifies PLANE 1 with Continuous Weight Positions selected P2 D P2 C NOT SHOWN Same as above but for the second weight plane DESCRIPTION OF CAPTION AND SCREEN APPEARANCE FOR THE FOUR ALTERNATIVE WEIGHT CORRECTIONS 1 lt PAGE gt ADD REMOVE TWisON lt 1 J gt OFF Default with no minus sign before weight number You are planning to ADD weight with the trial weights left in place lt PAGE gt ADD REMOVE TWisOFF lt J gt ON No minus sign before weight number You are planning to ADD weight with the trial weights removed lt PAGE gt ADD REMOVE TWisON lt 4 gt OFF A minus sign appears before weight number You are planning to REMOVE weight with the trial weights left in place lt PAGE gt ADD REMOVE TWisOFF lt 7 J gt ON A minus sign appears before weight number You are planning to REMOVE weight with the trial weights removed SCREEN A7 TOLERANCE CHECK TRIM REMINDER MUX IS ENABLED This means you must be using the CS7 MODEL 642 Multiplexer to collect your data CHECK RUN 1 This will tell you which correction run your are on You should not need more than two correction runs 1 APPLIED WEIGHT When blank it signifies you have not entered the actual weight you will be applying When an X appears the correction weight has been applied added or remov
20. ed whichever is the case 2 CHECK RESULT This lets you see a graphical representation of the correction results after your correction run The correction run steps appear on the next card CARD 13 3 TRIM CORRECTION After your correction run you may want to trim machine in by leaving the correction weights on This will let you do that P amp E Technical Training Department 10 96 25 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 13 Field Balancing with FAST Bal Il TOLERANCE TRIM CHECK 1 After completing the correction weight setup SCREEN A8 displays Enter the exact weight and location of the weight applied 2 SCREEN Z displays The same sequence as for reference and trial runs ensues SCREENS A1 Z and possibly A3 display 3 After the correction run SCREEN A7 displays Check the result TIP Trim runs are OPTIONAL depending on your acquired results If the phase vector fluctuates greatly SCREEN Al CARD 9 you will not improve the balance by continuing What to Do to get HELP 1 Go to the help screen it is available from many screens in the program TIP IF all of the SCREEN A9 s looks like the one below the balance job is within the tolerance you set IF there are some points outside the circle the vibration magnitude is out of tolerance TIP It is not possible to show all of the incident display screens for the various setups in FAST BAL I so READ EACH SCREEN C
21. ificant results when other problems are present in the frequency spectrum and multiple vibrations are evident in the waveform Many references suggest eliminating other problems before attempting to balance That s great if you can do it There are valid reasons for this approach and it would be much easier to balance machinery when other problems have been corrected It is the theoretical ideal in field balancing However in the real world of machinery maintained for years by reacting to immediate problems the classic vibration signature for unbalance is rarely seen We make most of our decisions with limited information The decision to balance or not to balance is usually made the same way This paper will demonstrate significant results of field balancing in the presence of multiple problems By examining the data available and analyzing the probabilities a reasonable chance for success can be assured Bob Bracher Vibration and Training Specialist Oak Ridge National Laboratory managed by Lockheed Martin Energy Research Corporation Post Office Box 2008 Oak Ridge Tennessee 37831 6411 September 5 1997 Notice The submitted manuscript has been authored by a contractor of the U S Government under Contract Number DE AC05 960R22464 Accordingly the U S Government retains a non exclusive royalty free license to publish or reproduce the published form of this contribution or allow others to do so for U S Government p
22. ing and field balancing was the next step We had help from our Central Engineer Blake Van Hoy by telephone but 7 was sweating this one out Bob Bracher Vibration and Training 6 Plant amp Equipment Division ORNL Spectrum After Balance 7503 Whirlex Exhaust Fan SF 2 7803 18580 FIH Fan Inboard Horizontal os Route Spectrum O7 MAR S7 10 47 7503 Whiriex Exhaust Fan SF 2 7503 16580 FIH Fan Inboard Horizontal cd Route Spectrum 06 MAR 97 14 49 bie OVRALL 0432 VDG PK 0479 LOAD 100 0 RPM 1250 RPS 2083 OVRALL 1517 V DG PK 1660 LOAD 100 0 RPM 1250 RPS 2083 02 2 s 2 D2 ips a gt x z A z gt 0 1 2 3 4 5 6 Frequency in Order Label After Fixing Loose Base Bolts 0 4 2 3 4 5 6 Frequency in Order Label After Balancing Still too high Fig 5 Second spectrum Fig 6 Final spectrum The vibration for this fan was significantly reduced but to my way of thinking it was still too high see Fig 5 It was running at only 1250 rpm and it was headed for a speedup We were fortunate to have two millwrights observing during this balance job Good thing too because one of them J J Vivyan discovered the source of the remaining 1x vibration During our trial weight run she noticed that a base bolt was loose After all of the base bolts were tightened the vibration was reduced even further and this fan continues to operate smoothl
23. irectional to some extent with the horizontal reading gt 4x the vertical reading Relevant Spectrum Spectrum After Balance 2619 Overfire Blower Bolier 2 20 2519 0BB 2 MOH Motor Outbowa Horizontal x Route Spectrum 27 SEP 96 08 39 2519 Overfire Blower Boiler 2 20 2 19 OBB 2 MOH Motor Outboard Horizontal Route Spectrum 27 SEP 96 14 18 OVRALL 1240 V DG PK 1268 LOAD 100 0 RPMa 3572 RPS 6953 1 681 ips OVRALL 1 66 V DG PK 1 66 LOAD 100 0 RPM 3672 RPS 59 53 PK Veloctty in In Sec PK Velocity in nvSec 10 Frequency in Order Label Before Balancing New Bearings 3 0 30 _ Frequency in Order Label After Field Balancing Fig 1 Initial spectrum Fig 2 Final spectrum Decision to Balance The decision to balance was made on the basis of work already performed major 1x vibration and the comparatively low magnitude of the 2x 4x harmonics During the balance job the software help message CSI FAST Bal II advised that the vibration was directional at one measurement location out of four We continued to balance and the spectrum above shows the pleasing result Incidentally the weight had to be placed at the same phase location as the original weight hence the name for this case history Other Fan Problems After field balancing the 2x 4x fan harmonics are now 20 of overall vib
24. ision SCREEN INFORMATION Card 7 SCREEN Q BALANCE FUNCTIONS Default screen for FAST Bal Il Main Menu JOB DEFINTION Complete specific details defining the balancing job are entered in the succeeding screens MAKE MEASUREMENT Reference and trial runs can be setup and executed from succeeding screens CORRECTION WEIGHTS Calculates correction weights and locations after reference and trial runs TOLERANCE CHECK TRIM Allows actual weight and location inputs tolerance check and trim weight calc OPTIONS Not strictly a part of the program the options listed allow data storage recall editing review loading dumping special data calculations selection of balance mode and default sensor setup See CARD OPTIONS for more information a ee a SCREEN R JOB DEFINITION 1 CLEAR JOB Toggle to YES or No using any Alpha Numeric key A YES selection allows you to clear the entire job or parts of it If you want to save it you must go to OPTIONS and STORE JOB before clearing it USER Insert 1 3 characters here to identify yourself as the user of the program JOB Identify job by number as desired This number will be used to identify the job and for storage and recall MACH ID Please use the P amp E Programmed Maintenance ID Number here if possible STATION Usually the Building Number location of the equipment SHAFT The default is 1 If the machine has more than one shaft enter the number of the shaft being balanced SPEC E
25. nter your balance specification for this job The units will match your sensor CONVERT TO setup For example if you are converting to VELOCITY this figure will be in inches per second CIPS If you are unsure of the balance specification begin with lips SEO gn ee ie SCREEN S DEFINE BALANCE JOB 1 WEIGHT PLANES Enter the number of weight planes to be balanced 1 4 2 MEAS PLANES Up to 8 measurement planes may be input Balancing may be with 2 but 4is recommended 3 MEAS SPEEDS Up to 6 speeds may be entered however speeds x points cannot exceed 24 4 DISCRETE WEIGHT YES NO Use an ALPHANUMERIC key to toggle YES NO If any plane is restricted to a certain number of segments for adding or subtracting weight toggle to YES You can select CONTINUOUS for individual planes later Si SUBTRACT RUNOUT YES NO Use an ALPHANUMERIC key to toggle YES NO Toggling to YES allows runout data to be subtracted when using displacement probes Normally it is not used when using accelerometers SCREEN T DEFINE TACH OPTIONS ROTATION Allows selection of Clockwise or Counterclockwise rotation according to user point of view ANGLE DEG TDC Allows selection of Tach pickup relative to the Top Dead Center TDC position DELTA By inputting a number of 1 500 user specifies acceptable valid data limits above and below RPM RPMI RPM2 efc 1 20 000 for each RPM may be input l 2 3 4 PEE Technical Training Department 10 96
26. ons Review the graphic screens after setup to ensure accuracy 1 ROTATION Toggle left and right arrows to clockwise or counterclockwise as appropriate 2 NUMBER OF POINTS Enter 1 3 Normally there will be two measurement sensors per measurement plane 3 MPT ID The default setup for 4 sensors is IBH Inboard Horizontal Channel 1 IBV Inboard Vertical Channel 2 for MEASUREMENT PLANE 1 OBH Outboard Horizontal Channel 3 OBV Outboard Vertical Channel 4 for MEASUREMENT PLANE 2 You may change it as appropriate for your job and preference 4 ANGLE TDC Input in degrees against rotation for default setup sensor position relative to TDC 5 CH Enter a number 1 8 to reference the CHANNEL This must be completed even if you are not using a mux so the identity of the sensor matches the channel every time a reading is taken 6 RAD AXIAL Toggle between radial and axial depending on sensor orientation Normally all will be radial 7 SYM Shows the graphical symbol representing this sensor and it cannot be changed It is for reference only SCREEN X DEFINE WEIGHT PLANE 1 1 ROTATION Confirm rotation for this display Toggle with Left right arrows 2 WEIGHT POSITIONS Input 1 100 for total number of available weight positions equally spaced for this weight plane 3 157 POSITION ANGLE Enter number in degrees from rotor reference of choice tach position or TDC 4 POSITIONS NUMBERED AGAINST ROTATION Toggle YES NO The def
27. ps for Single Plane Balancing Acquire reference data Add one or more trial weights Acquire trial run data with trial weights in place Remove trial weights Determine whether to add or remove weight to balance A Calculate correction weight and location required to balance machine add or remove B Ifadding weight permanently affix correction weight if removing calculate area needed for removal and remove weight Check results and trim balance as necessary Repeat trim runs as necessary until within tolerance or acceptable to customer If trim balance calls for too much weight gt 50 of correction re evaluate job Return machine to customer according to YOUR COMPANY S procedure PAE ey hee eo La 6 T 8 9 Bob Bracher Vibration and Training 4 Plant amp Equipment Division ORNL Case History One The Underbalanced Overfire Blower Nature of Involvement No vibration readings had been taken on this fan before September 27 1996 The resident _ millwright Eddie Baird had known of our program and some of our equipment and he recommended our services to the relief supervisor Known Facts New bearings had been installed in the motor and the fan rotor was cleaned The fan shook the entire second floor of the steam plant when the operators tried to run it This fan had motor bearings only A set of vibration data was taken to verify that the fan was out of balance The vibration was d
28. ration Additional data reveal that the vibration magnitudes are no longer directional This suggests excitation vibration due to original high magnitude Tracking and trending is the order of the day for this machine Technical Training Department Field Balancing in the Real World Case History Two The Confident Consultant Nature of Involvement An outside consultant was hired by the ORNL Environmental Restoration Division to determine the upgradeability of two exhaust fans for one of our old reactor facilities the Molten Salt Reactor Experiment MSRE nicknamed ole salty Our resident millwright Bob Hileman for that area advised his supervisor and the consultant of our services We had already recommended a data collection route be started there Known Facts Previous readings had been taken on this belt driven centrifugal fan and the sheaves were realigned with a matched set of belts installed New bearings were installed previously The vibration readings were still too high The data did not show a clearly unbalanced condition However in the face of increased speed we recommended a coastdown test to determine the need to balance in order to reduce the vibration Relevant Spectrum 7503 Whirlex Exhaust Fan SF 2 7803 16580 FIH_ Fan inboard Horizontal Route Spectrum Z2 NOV 96 16 34 7503 Whiriex Exhaust Fan SF 2 7503 19500 FIH_Fan inboard Horizontapcember 96 Max Amp 2 ii meee a8 Plot 18 19 24
29. s or grams you are adding to the weight plane LOCATION The symbol always precedes the location number for discrete weight positions and the numbering is against rotation from the 0 reference unless the default setup was changed You may add up to two different weights at up to two different locations per weight plane One is usually enough ROT The gt or above the abbreviation for rotation reveals the rotation direction selected SCREEN A1 SCREEN Z see CARD 9 SCREEN A5 REMINDER self explanatory TRIAL RUN NOTES Up to four weight planes may be ddefined and multiple speeds may be defined Generally you would proceed as follows 1 Add trial weight to WEIGHT PLANE 1 2 Input weight and location 3 Acquire data for all measurement points 4 If multiple speeds acquire data for each specified speed 5 Repeat for each defined weight plane If you need more information see CSI FAST Bal II User s Manual Chapter 4 P amp E Technical Training Department 10 96 23 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 12 Field Balancing with FAST Bal Il CORRECTION WEIGHTS What to Do continued from CARD 11 Howto Dott _ 1 After completing all trial rans SCREEN Q displays Go to SCREEN A6 CORRECTION WEIGHTS 2 SCREEN A6 displays To accept Add weight with trial weights left in place toggle TW Off On TIP You do not have to add the exact weight required but
30. splays the 3 digit identification of current sensor 2 RPM Displays the instantaneous rpm from phototach or other rpm sensing device 3 MAG Displays the averaged amplitude in units of output Normally it is inches per second IPS velocity 4 RMS PK PK PK Displays unit of measurement according to set up Normally PK IPS for velocity 5 PHASE Displays the averaged phase of the high spot from the tach location measured in degrees against rotation normally but may be reset by the user 6 DATA STABILITY Live time display of phase and amplitude stability The vertical bar separating the GOOD side from the POOR side marks where the average magnitude is varying or 5 and the average phase is varying or 2 5 7 Graphic Display e O This box displays at the end of the instantaneous vector showing the phase and relative amplitude This symbol indicates the average ve tor endpoint T This displays position of the tach reference ROT Shows current rotation direction selected NOTE When the MUX ENABELED is set to AUTO see CARD 8 the analyzer will automatically enter data when it is in the GOOD stability range for both magnitude and phase The user may override the analyzer AUTO mode by pressing the ENTER key to accept data i PEE Technical Training Department 10 96 19 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 10 Field Balancing with FAST Bal Il
31. uency in Order Time in Seconds ROUTE SPECTRUM O1 MAYS7 12 07 QVRALL 2907 V DG PK 3224 LOAD 100 0 RPM 2997 RPS 49 95 WAVEFORM DISPLAY O1 MAY 87 12 07 RMS 2447 PK 4442 PK 3772 CRESTF 1 82 Fig 17 Case History Three final Technical Training Department Field Balancing in the Real World This Page Left Blank Bob Bracher Vibration and Training 12 Plant amp Equipment Division ORNL Appendix B On the Job Assistance The remaining pages contain copies of job aid cards for performing a single plane field balance using CSI FAST Bal II They were developed and field tested by the ORNL Plant amp Equipment Division Technical Training Department ORNL is managed by Lockheed Martin Energy Research Corporation for the United States Department of Energy The CSI FAST Bal IT User s Manual and our CSI 2115 Machinery Analyzer were used to develop these Accuracy of information contained cannot be guaranteed CSI does not necessarily endorse the information and CSI is not responsible for content 13 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 7 Field Balancing with FAST Bal Il JOB DEFINITION Part 1 What to Do Cd owto Dott O T a See Le ee ghted go to SCREEN R 2 Fill in the job definition fields fre PM numbers for MACH ID Change the SPEC field as needed go to SCREEN S 3 Complete SCREEN S according to the job NOTE
32. urposes Oak Ridge National Laboratory is managed by Lockheed Martin Energy Research Corporation for the U S Department of Energy Technical Training Department Field Balancing in the Real World Acknowledgements In a large multifunctional company such as ORNL it takes the efforts and contributions of several groups and individuals to bring about the change necessary to implement new techniques and ideas Field balancing is not new The idea of doing it on our own is new Without the efforts of Eddie Baird Wayne Castleberry Doug Edwards Bob Hileman Blake Van Hoy and J J Vivyan we would not have been able to perform the jobs mentioned in the case histories Their efforts were made possible by the cooperation and support of managers administrators field maintenance and operations staff and consultants of ORNL Plant amp Equipment Division ORNL Waste Management Remedial Action Division and ORNL Environmental Restoration Division Their continued efforts and support is appreciated CSI deserves some credit too for the many times they helped me resolve problems by telephone in class or in person I particularly want to express my appreciation to the training information desk sales software hardware and technical support groups and specially to Darla Adcock Introduction This paper will discuss case histories of field balancing jobs successfully accomplished at Oak Ridge National Laboratory ORNL in the presence
33. ut for the second weight plane WEIGHT This tells the quantity of weight whether ounces or grams you are adding to the weight plane LOCATION The symbol always precedes the location number for discrete weight positions and the numbering is against rotation from the 0 reference unless the default setup was changed You may add up to two different weights at up to two different locations per weight plane One is usually enough ROT The gt or above the abbreviation for rotation reveals the rotation direction selected TRIAL WEIGHTS LEFT ON YES This is a statement If the trial weights need to be removed you must back up in the program to do so SCREEN A7 See CARD 12 SCREEN A3 HELP this particular help screen is for TOLERANCE CHECK SCREEN A9 TOLERANCE CHECK SPECIFICATION 0 080 This is the tolerance you entered in setup If your line from the points on the graph extend into the circle your 1X vibration is within the tolerance you entered see CARD 7 IN SEC PEAK This indicates you are reading out in velocity inches per second peak averaged PLANE 1 SPEED 1770 This identifies the weight plane of interest and the speed of interest MPT ID The symbols and letters directly below identify the measurement points of the measurement plane MPT MAG The numbers below display the magnitude or amplitude of the last reading for the corresponding MPT DOWN This is a comparison of the last reading to the first reading
34. vision ORNL Demonstration of Multiple Problems The machine used for the demonstration is the Baseline Trainer available from CD International For more information on this machine contact Mr Zane Dreja at CD International Lewiston New York 1 800 388 7972 Summary As demonstrated field balancing can achieve significant results when other problems are present in the frequency spectrum and multiple vibrations are evident in the waveform see Appendix A for waveform data CAUTION Always correct other known problems if able to correct them before field balancing Never attempt to field balance a machine if you are not reasonably certain it will significantly reduce the vibration Recommendations Adopt a troubleshooting strategy such as the one mentioned earlier Decision to Field Balance or develop your own Follow a checklist or guideline plan to avoid the frustration that comes from futile field balancing effort Maintain records of balance jobs If you have no record of where you have been no one will really know how far you have come except you Use the reference materials listed to improve knowledge and skills Vv Y WV Y References The following publications are highly recommended for increasing your knowledge and skills in field balancing Most also cover other vibration topics The Simplified Handbook of Vibration Analysis Vols I amp 2 Crawford CSI 1992 Machinery Vibration Balancing Wo
35. was suspected SCREEN A3 HELP 1X RPM VS OVERALL The HELP screen if available is accessed by pressing the KEYPAD key on the analyzer Read it completely to help you make a decision on what to do next Most of the time you would continue with the balancing job If it does not reduce the vibration significantly there are other problems causing the vibration P amp E Technical Training Department 10 96 21 Technical Training Department Field Balancing in the Real World 2115 Analyzer Card 11 Field Balancing with FAST Bal Il MAKE MEASUREMENT Part 3 What to Do to perform TRIAL RUN continued from CARD 10 How to Dolt SCREEN A4 displays Enter weights and location for the trial run for discrete wt planes by position number otherwise degrees against rot A vector displays on graph showing position relative to tach position T SCREEN Z displays take measurements at the accelerometer points listed In AUTO mode see MUX CARD 8 the analyzer will take all the readings and accept them when Data Stability is in GOOD range SCREEN Z displays again as shown below Advance to SCREEN A5 with the REMINDER to remove trial weights or include them in the next trial definition TIP If using two weight planes run one plane for Trial Run 1 and the other weight plane for Trial Run 2 see below See other side for additional information What to Do to perform TRIAL RUN on WT PLANE 2 if necessary 4 SC
36. wk McGraw Hill 1995 Shock and Vibration Handbook Fourth Edition Harris Industrial Press Inc 1996 Reliability Magazine Industrial Communications P PM Magazine Second Childhood Inc Vibrations VI Press Inc A Vibration Institute publication 9 Technical Training Department i Field Balancing in the Real World Appendix A Spectra and Waveforms for All Case Histories Bump Test Example 2519 Overfire Blower Boller 2 2519 0BB 2 MOH_ Motor Outboard Horizontal PK in Sec WAVEFORM DISPLAY 27 SEP 96 08 39 RMS 1 18 PK 2 34 PKI 2 02 CRESTF 1 95 Acc in Ga Sab bad ane 7503 Whirlex Exhaust Fan SF 2 7503 18580 FIH Fan inboard Horizontal ROUTE SPECTRUM 22 NOV 96 16 34 OVRALL 3777 V DG PK 3779 LOAD 100 0 RPM 1250 RPS 2083 3 4 WAVEFORM DISPLAY Z2 NOV 96 16 34 RMS 1026 PK 2157 PK 4 2213 CRESTF 2 16 0 06 10 18 20 25 30 35 Time in Seconds Label Resonance Directional 7503 Whirlex Exhaust Fan SF 2 7503 185680 FIH Fan inboard Horizontal ROUTE SPECTRUM O7 MAR ST 10 47 PK infSec LOAD 100 0 RPM 1250 RPS 2083 WAVEFORM DISPLAY OT MARBT 10 47 RMS 0165 PK 0486 PK 3 0622 CRESTF 3 17 Ace in G s Fig 14 Case History Two final Bob Bracher Vibration and Training 2519 Overfire Blower Boller 2 2819 OBB 2 MOH Motor Outboard Horizontal 16 ROUTE SPECTRUM 27 SEP 96 14 18 12 OVRALL 1240 V DG as PK 4266 oa LOAD
37. y The happy customer ORNL Environmental Restoration Division placed this fan and its mate on periodic vibration data collection Other Fan Problems There is some nonsynchronous energy mixed number multiples of running speed present in the last spectrum Fig 6 Tracking and trending with realistic baselines fault frequencies of bearings belts blade pass and parameter banding will help us correct the problem at the customer s convenience before a breakdown Fig 7 Fan discussed in Case History Two Technical Training Department Field Balancing in the Real World Case History Three The Doubtful Backup Nature of Involvement This particular fan was placed on routine periodic vibration monitoring along with several others thanks in large part to our resident millwright in the area Doug Edwards who will assist me with the demonstration today The first reading taken to establish baseline data showed serious problems Known Facts The turbine driven direct drive fan had recently been serviced The turbine was rebuilt and it was aligned low to allow for thermal growth No history was provided except the memory of the craft people working on this and similar jobs This overhung fan served as a backup exhaust fan to an electric motor driven primary and it was operated once a week for about 30 minutes to verify that it was usable Relevant Spectrum Spectrum After Balance 3039 3039 00125 ORR CELLVENT STBY 18 TS _ FOH Fan
38. you back one screen RESET returns you to BALANCE FUNCTIONS SELECT MEASUREMENT REMTIHDER MUR IS ENAELET 1 REFERENCE RIN weil FUNCTIONS MACH ID 2e amp 6e 1193 me k 2 ma HEAS UKENEN SCREEN Y PRESS ENT ER To Bob Bracher Vibration amp Training 18 Plant amp Equipment Division SCREEN INFORMATION Card 9 SCREEN Q See CARD 7 SCREEN Y SELECT MEASUREMENT NOTE The display for SCREEN Y on the other side is for a single plane balance with no correction for runout Normally correction for runout is not necessary unless you are using a displacement probe 1 REFERENCE RUN Data is collected with no weights added 2 TRIAL RUN 1 After collecting reference run data a trial run is performed with weights added in the weight plane If two plane balancing is performed a TRIAL RUN 2 will display also In that case the second trial run will be made by adding weights to the second weight plane and removing normally the weights from weight plane 1 SCREEN Z SELECT MEAS POINT CAUTION Be sure to check that your measurement sensor location matches the description for the channel collecting data Data will be invalid otherwise When ready to collect data and the channel one sensor is placed at the MPT listed usually IBH Inboard Horizontal and data collection has begun the Al SCREEN displays see below SCREEN A1 no title shows graphic display in vectors 1 MEAS POINT Di
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