CXB English manual for Balancing 1plane-2Transducers
Contents
1. 23 21 mm s RMS 2 9 6 Uqr p 0 09 1000mm Measure ESC Exit Next step Edit weight Figure 7b Trial run 16 07 2014 09 40 100 0rmm 2971 CPM Rotor Trial runs Add remove Change Unit Figure 7c The correction mass proposed by the instrument The correction amount required is 60 2 g In this case is easy to see that the correction mass is enormous rotor mass being only 4 Kg In the field is very difficult to appreciate if a correction mass is large or small so it s easy to make mistakes with catastrophic effects Now let s perform a balancing with two transducers placed onto the bearings B1 and B2 The result obtained after the trial runs is shown in Figure 8 It is observed that the proposed correction is only 2 7 grams which is a reasonable value BalancinglP2T 16 07 2014 09 42 Balancing speed 2971 CPM Rotor Trial runs Add remove Change Unit Figure 8 CXBalancer By making the proposed correction the residual unbalance will be the one seen in Figure 9 BalancinglP2T 00 22 06 21 64 Rotor Trial runs Figure 9a Initial values 16 07 2014 09 51 BalancinglP2T 00 16 07 2014 09 51 wibi 64 00260 6 n A Balancing speed 2971 CPM Measure ESC Add remove Change Unit Rotor Trial runs Add remove Change Unit Figure 9b The values after balancing It is easy to observe that the vibrations have decreased significantly from 9 4 mm sec2. Because B1 is the closest bearing to the balancing plane we ll choose it as a mounting place for the transducer Normally when proceeding the traditional one plane balancing we ll take as transducer s direction horizontal or vertical the one with the higher vibration If we use the method with two transducers we ll place one in the horizontal direction and the other one in the vertical direction both of them on B1 bearing B1 1 Bearing B2 2 Bearing Figure 1 We will perform the balancing with two transducers in accordance with The User Manual and the value of the unbalance that should be compensated will appear on the screen as shown below Figure 2 e Onto the right side screen will appear two correction values one measured with VIB1 transducer and the other one measured with VIB2 transducer e Onto the left side screen will be displayed the proposal of the balancing instrument This may be the measurement of VIB1 VIB 2 or a combination of them The proposed correction amount will reduce the vibration if applied CXBalancer Initial run 12 16 07 2014 08 25 BalancingLP2T 16 07 2014 08 33 21 17 23 48 mms RMS mms RMS 9 4 96 7 Balancing speed 2972 CPM Balancing speed b Measure ESC Exit Next step Measure ESC Rotor Trial runs Add remove Change Unit Figure 2a The initial vibration Figure 2b The proposed correction In this simple case the advantage becomes obviou
3. is at your own risk CXBalancer Balancing with two Transducers in one Plane I Overview 1 Introduction Typical one plane balancing procedure uses a single transducer The measurements describe only the status of a single bearing of the rotor assembly In many situations this is not enough to appreciate properly the status of the assembly This procedure has been developed to provide to the operator necessary information about both bearings of the assembly in order to improve balancing results and to make balancing procedure safer This new procedure takes advantage of CX Balancer design it provides simultaneous measurement on 2 channels so the second measurement will not deteriorate response time All vibration measurements done during the procedure will be shown for 2 transducers similar with two plane balancing procedure Briefly the program calculates the results for both measurements VIB1 and VIB2 and plane selected using normal 1 plane balancing algorithm and assist the operator to select the best choice 2 When to use Before to start balancing a vibration measurement and analysis procedure should be carried out This must determine if the unbalance is the predominant cause for vibration Also the 1XRPM values should be analyzed in order to determine the bearing and directions where they are bigger Also the rotor configuration must be analyzed report between width and diameter and also distance between bearings in
4. speed 3 100 0rmm 1490 CPM 100 Measure ESC Rotor Trial runs Add remove Change Unit Measure ESC Rotor Trial runs Add remove Change Unit Figure 14a The proposed trial weight Figure 14 b The final unbalance It is also confirmed that vibrations were decreased onto both bearings Figure 15 BalancingiP2T 02 16 07 2014 10 24 0 50 Q 36 roms RMS mm s RMS 120 5 Balancing speed 100 0mm 100 1490 CPM Rotor Trial runs 4dd remove Change Unit Figure 15 CXBalancer 6 Conclusions This document tried to explain you in a few simple examples the advantages of using two transducers when performing one plane balancing Of course the arguments of the method listed above would have been much stronger if they had been mathematically proven did this not because the formulas are a deep secret to me but simply in order to offer you the pleasure of doing it by yourself Please also do not hesitate to share us any personal success related to the use of the instruments manufactured by US IMPORTANT NOTE Although MaintTech Sweden believes reasonable efforts have been made to ensure the accuracy of the information contained in this document it may include inaccuracies or typographical errors and may be changed or updated without notice It is intended for discussion and educational purposes only and is provided as is without warranty of any kind and reliance on any information presented
5. to 0 3 mm sec but only on the B2 bearing In the meantime the vibrations onto B1 to which we intended to drop the vibrations practically remained unchanged from 64 6 to 64 0 mm sec Furthermore a negligible correction of 0 1 grams is now required so there is nothing to be done However after balancing the overall level of vibration decreased with 17 fact that hasn t solved the issue of lowering the vibration for the plane VIB1 Notice that the balance has been made in terms of safety as there has been added an acceptable correction mass but the final result is not satisfactory yet The solution in this case is to dismantle the rotor and to balance it onto a balancing machine in the workshop impossible 5 A strange Case Without access to the balancing plane near B1 a better balance it s We intend now to perform a two plane balancing for the rotor in Figure 10 m 4 Kg P1 P2 J I l l l l l l l l l l l l B1 1 bearing 1 P1 P2 Balancing planes Figure 10 B2 2 bearing CXBalancer Balancing 00 16 07 2014 07 54 Balancing speed 100 0mm 1O00 0mm 1490 CPM if 4 Rotor Trial runs Add remove Change Unit Figure 11 In accordance with the indications on the screen it comes necessary to add abnormally large correction masses Figure 11 By splitting the VIB1 and VIB2 vibrations in STATIC and COUPLE components you can do this by pressing MENU and sele
6. CX Balancer 1 plane Balancing with 2 Transducers Rev 1 0 17 07 2014 MaintTech phone 46 707 732274 M al n tTe C a Norrkoping e mail mainttech live se Sweden website www mainttech se Note Instrument Screens design can be changed in the future software version and can be changed without any notice The screen shots at the present Manual are for reference only CXBalancer 1 Introduction It is generally known that a measurement made with two transducers is better than the same procedure using only one transducer Then why the one plane field balancing is not usually performed with both transducers available in the Toolbox The answer is probably most of the balancing instruments don t have such a software One plane balancing with two transducers is no longer a revolutionary method and it isn t even a novelty It is theoretically very well known for long time ago Then the logical conclusion is that this simple method was forgotten by most of the producers of balancing instruments as they often forgot the real needs of the end users The CXBalancer series have two standard vibration transducers and a software menu specially dedicated to the balancing purpose This paper will present you some examples of use whenever possible of this method particularly for field balancing 2 A simple case Let s assume that we have to perform one plane balancing for the rotor shown below in figure 1
7. I Description 1 Procedure From Balancing menu select New One plane 2 Tr Balancing Main menu 03 07 2014 15 00 Balancing menu Continue Balancing 2 New One Plane Balancing 3 New Two Plane Balancing The program will enter in Configure Balancing There are not differences compared with 1 plane balancing The user should press Continue after adjusted the settings Configure Balancing 09 07 2014 15 01 AVES SSE Disablec Show unit mm sS RMS gmn Kg gt 00 CPM CPM Continue CXBalancer The program will enter in main balancing screen Free run mode This is similar with 1 plane balancing except that on right panel it displays the vibration measurements of VIB2 transducer Balancing2T Free run 09 07 2014 15 04 0 00 0 00 mm s RMS mm s RMS 0 0 Balancing speed Rotor Trial runs 4dd remove Change Unit Please notice the title in window header which is Balancing2T Free run The rotor parameters are similar with 1 plane balancing The difference appears on Trial run Compared with one plane balancing there will be a right panel where the instrument displays the vibration measurements of VIB2 transducer This is the only difference Initial run 1 2 09 07 2014 15 14 21 07 5 06 mm s RMS mm s RMS Trial run 2 2 09 07 2014 15 14 26 13 8 95 mms RMS mms RMS 4 Balancing speed 2d gr a 1O0 0mm Measure Edit weight step There are the same 2 steps and the same h
8. andling After trial runs are done the user should press ESC as usual to enter in main balancing screen balancing mode When the units of unbalance are selected the screen will look like below CXBalancer Recommended unbalance correction BalancingLP2T 19 07 2014 15 23 Balancing speed 150 0mm 2969 CPM Rotor Trial runs 4dd remove Change Unit Unlike 1 plane balancing there are 2 new panels in the right Also the meaning on upper left panel is changed 1 Vib1 results panel contain the results of 1 plane balancing using the transducer VIB1 This is similar with the values of normal 1 plane balancing 2 Vib2 results panel contain the results of 1 plane balancing using the transducer VIB2 This is similar with the values of normal 1 plane balancing session if VIB1 transducer would be attached in actual position of VIB2 remember that 1 plane balancing uses only VIB1 3 Recommended unbalance correction Those are the values recommended to attach to rotor in order to do balancing CXBalancer 2 Data analysis How to use new data 1 If the values shown in VIB1 results and VIB1 results are similar then the rotor can be balanced in one plane In this situation the recommended value is an average of the two values VIB1 label AND VIB2 label should be shown with yellow color If the values shown in VIB1 results and VIB2 results are opposite as angle but the values are closer together then the rotor can
9. assess whether the total vibration of both bearings was reduced or not The scalar addition is incorrect So the total vibration V is not the sum of the two vibrations Vg and Vp i e 25 34 2 2 4 o Y lla Yaa mm sec but it is correctly calculated in accordance with the formula that means 22 42 mm sec Let s do a balancing using the two transducers method Obviously we will place them onto both bearings available B1 and B2 respectively In Figure 4 can be seen the initial vibrations measured on both bearings Initial run 1 2 16 07 2014 11 21 22 20 3 14 mm s RMS mm s RMS 5 13 2 Balancing speed e971 CPM El Figure 4 The initial vibrations The final result obtained after correction in VIB1 plane Figure 5 is similar to that shown in Figure 2 BalancinglP2T 03 16 07 2014 11 20 BalancinglP2T 05 16 07 2014 11 20 1 82 mms RMS mms RMS 2 31 0 Balancing speed 100 0rnm Balancing speed an age 99 2971 CPM 2971 CPM Measure ESC Exit Measure ESC Rotor Trial runs Add remove Change Unit Rotor Trial runs 4dd removel Change Unit Figure 5a The final amount of unbalance Figure 5b The final vibrations So after the correction in accordance with instrument recommendations the final vibrations were obtained CXBalancer Ve1 0 42 mm sec and Ve2 1 82 mm sec It is observed that both vibrations decreased comparing to the initial values Figure 4 Since the correc
10. cting Static Couple we ll get the next screen Figure 12 Balancing 00 16 07 2014 07 54 44 2 Static couple results Static unbalance PEN Couple unbalancel 42 5gr Couple unbalance 42 5gr 251 2 ESC Exit a LFI Cie 4o Rotor Trial runs Add remove Change Unit Figure 12 The static component is small but the couple one is very high What is the cause To get the answer we ll have to analyze the relative vibration obtained after performing all three trial runs Figure 13 Initial run 1 3 16 07 2014 07 49 4 18 9 07 mms RMS mm s RMS p 126 5 303 7 16 07 2014 10 10 5 38 1322 mm s RMS mm s RMS 284 9 Balancing speed 1490 CPM Eil Measure ESC E Balancing speed Fa 309 0 09 Measure ESC Exit Next step Edit weight Figure 13 a Initial run Figure 13b First trial run CXBalancer Trial run 3 16 07 7014 10 10 5 4 7 13 34 mm s RMS mm s RMS Eno a speed Eno a CPM Ei Edit weight Figure 13 c Second Trial run We can observe that both trial weights mounted in VIB1 and VIB2 planes produce roughly the same effect 5 38 5 43 respectively 13 34 13 22 The conclusion in this case is that a two plane balancing is neither required nor possible being recommended only one plane balancing with two transducers Here are the results BalancinglP2T 16 07 2014 10 20 BalancinglP T 02 16 07 2014 10 24 Balancing speed 1490 CPM Balancing
11. d will display this in recommended unbalance correction panel III Conclusion This feature provides new information to the operator during one plane balancing Those informations will help the operator to achieve better results
12. not be balanced in one plane Correct balancing must be done in 2 planes Just a small correction will be possible In this situation the recommended value is an average of the two values VIB1 label AND VIB2 label should be shown with yellow color If one of the values the values shown in VIB1 results and VIB1 is much bigger than the other this means that the vibration of the bearing with higher calculated correction mass is not influenced by unbalance in selected plane see figure above VIB2 In this situation the recommended value is the smaller one VIB1 above When attach weight to this position just vibrations in specific bearing will be reduced e g VIB1 above If the other bearing has bigger vibration the rotor cannot be balanced using selected plane thus selected plane is not suitable to reduce vibrations on the other bearing 3 How instrument recommend corrections The aim of in site balancing is to reduce the vibration level on both bearings The algorithm calculates the combined remaining vibrations VIB1 VIB2 for 3 solutions Attach of correction mass calculated for one plane balancing using the transducer VIB1 values shown in VIB1 results panel Attach of correction mass calculated for one plane balancing using the transducer VIB2 2 values shown in VIB2 results panel Attach of vector average correction mass between VIB1 and VIB2 The instrument will recommend the situation when remaining vibrations will be minimum an
13. order to decide if one plane balancing is suitable for it a Instead of regular 1 plane balancing This 1 plane balancing using 2 transducers procedure is recommended anytime when the rotor can be balanced in 1 plane Do not use it instead of two plane balancing procedure Typically you should attach the VIB1 transducer on the bearing where the vibration amplitude is higher Note that the balancing report will refer to the values computed using VIB1 values Normally the second transducer should be attached on the other bearing on the same direction This will provide a better control towards the rotor assembly However when for the same bearing the report between the amplitudes on different direction is high and or you are suspiciously about other mechanical problem as resonance or misalignment it is better to attach the transducer on the same bearing but on perpendicular direction versus VIB1 This will provide a better control towards the unbalance response b When there are not accessible 2 planes for balancing As noted above this procedure cannot be used instead of 2 plane balancing However in order to reduce the vibration throughout the rotor bearings when in site as this procedure will assist the operator to find a compromise solution Compared with normal 1 plane balancing this will provide a better control If the unbalance location is close to balancing plane the procedure can produce even good results CXBalancer I
14. s the correction value proposed by the instrument is the best choice in order to decrease vibrations in both directions Here you have a few tips when applying this balancing method Just notice the initial vibration the phase shift between the two vibrations will be around 90 i e the angle between the positions of the two transducers If it is not confirmed it means the machine has also a major misalignment problem The calculated correction amounts should be close values even if the vibrations are completely different Otherwise all the other major problems of the machine should be investigated and solved before balancing 3 Acommon case We have to perform a field balancing for the rotor P1 shown in Figure 3 Normally this rotor requires a two plane balancing which is difficult to be 22 2 mm s performed in situ Furthermore the vibrations measured on the two bearings are Ve1 22 2 mm sec and Ve2 3 14 mm sec B1 1 bearing B2 2 bearing In this situation we propose to do only a single plane balancing in P1 where we get a higher l vibration Figure 3 The VIB1 transducer will also be mounted onto B1 bearing CXBalancer If we re going to perform a traditional one plane balancing more than likely that VB1 vibration will decrease But what will happen with the vibration measured onto the B2 bearing From experience we just know that this value will usually change How can we
15. tion was done in VIB1 plan it s obvious that VIB2 vibration decreases less The total vibration becomes now v alive veg 1 87 mm fs which is significantly lower Even if VIB2 vibration would not be dropped the total value would have been v 10 4274 9 14415 9 L a is that is substantially less than the initial value of 22 42 mm sec So the balancing result is positive Remember Field balancing tries to reduce the level of vibrations but not necessarily to get a quality grade according to ISO 1940 1 4 A special case Let s suppose we have to balance the rotor shown Inaccessible P2 m 4kg in Figure 6 The initial measured vibrations onto the bearings are Vegi 22 23 mm sec and Ve2 9 4 mm sec Obviously we ll want to reduce vibrations onto B1 but P1 balancing plane is inaccessible B1 1 bearing 1 6 What can we do in this case B2 2 bearin Will we succeed to reduce the vibrations by performing a traditional one plane balancing Figure 6 mounting the transducer on B1 bearing or by using P2 as a balancing plane See below the result obtained after the trial run Figure 7 CXBalancer Initial run 16 07 7014 09 40 22 23 mms RMS 9 9 Balancing speed 2971 CPM Status Done Measure ESC Exit Next step Figure 7a Initial run Balancing Balancing speed Balancing speed 5 2971 CPM Trial run 16 07 7014 09 40
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