Today there is enough reference literature printed during the last 20 years alone on general balancing and balancing of flexible rotors, that could fill a. The balance quality requirements for rotors in a flexible state are covered by iso 142. Pdf practical balancing of flexible rotors for power. A rigid rotor can be balanced by making cor rections in any two arbitrarily selected i rnr u i a. Inspect the interlock system to ensure the cover cannot be opened while the rotor is spinning. Comparison of actual machine balancing speed with the desired balancing speed fed in. A rotor is said to be rigid when the flexure of the. Rotor unbalance may be caused by many factors, including material, manufacture and assembly, wear during.
If the rotor is not properly balanced, it vibrates as speed increases and may cause mechanical damages. If you need to spin only one tube, you must use another tube filled with fluid to balance the rotor. Rotor balancing is a fundamental requirement for the smooth operation of. Design and manual operation of balanc ing head, proc. Application notes static and dynamic balancing of rigid. Assuming that the balancing planes are located on the rotor, it is shown that reducing the vibration level of both rotor and stator requires a balancing procedure using target planes on the rotor. The easiest way to treat this problem is to break it down into a couple of parts. Over time various balancing methods were defined and developed 16. The following describes the procedure for performing single or two plane balancing. A balancing machine that provides for the support of a rigid rotor under nonrotating conditions and provides information on the amount and angle of the static unbalance. A rigid rotor is one whose service speed is less than 50% of its first critical speed. Twoplane field balancing of an overhung rigid rotor.
Rotor balancing crystal instruments leading innovation. I he balancing procedure tor flexible rotors is more complicated, because of the elastic deflections of the rotor. Balancing machines types, classification, and methods. Refer to chapter 62 for the complete field maintenance instructions for the main rotor. One common practice during shop balancing is to make static corrections near the center of a rotor using the low speed shop balance. The rotor is supported on the near bearing n close to the rotor and on the far bearing f far from the rotor, which are separated by a distance h. The results of balancing can be observed on time responses andor on the orbits. Vibration literature1 can be obtained for study in more technical detail. The incremental rotor balancing procedure turbomachinery. Maintenance procedures for these components will be found in the appropriate chapters. This part of iso 1940 does not cover rotors in a flexible state.
Loose balance weights rattling around inside a turbine for example can wreck the machine. Both analytic and graphical means of balancing using only 1. Reducing unbalance reduces vibration and increases efficiency and life of the rotor and bearings. The abovementioned problem is solved by the determination of critical frequencies and related mode shapes of rotors, as well as by conducting the previous virtual balancing procedure. Make a note of the fact that this is the speed to which our final results correct balancing weights will apply. However, all the methods other than 7 required the use of identical trial weights in the balancing procedures. Above this speed, the rotor is said to be flexible. Specification and verification of balance tolerances, gives specifications for rotors in a constant rigid state according to their. Unit 6 introduction to balancing introduction to balancing. I he balancing procedure for flexible rotors is more complicated, because of the elastic deflections of the rotor. Kroon, balancing of rotating apparatus ii, journal of applied mechanics, vol. Due to these reasons, the field balancing of rotors play an especially important role. To investigate unbalance on a rigid rotor, a laboratory test was done on an unbalanced rigid rotor and both static and dynamic balancing procedures were performed on the rotor. Thearle, dynamic balancing of rotating machinery in the field, translation of the asme, october 1934.
The balancing instrument can be configured to use customized reports in which the data collected by the balancing process automatically transfers to a customized template for reporting documentation or certifications. It is important that rotor balancing be performed by an experienced rotating machinery specialist. Introduction balancing a rotating machine is a vital step to ensure that the machine will operate reliably. In the case of a flexible rotor, it also means that not more than an acceptable magnitude of deflection occurs in the rotor at any speed up to the maximum service speed. Also, rotors that have higher vibrations from wear will benefit from a lowspeed balance. Balancing is a procedure by which the mass distribution of a rotor or part or module is checked and, if necessary, adjusted to ensure that balance tolerances are met. Spinning outofbalance loads may break tubes, and can cause damage to the. Balancing for balancing the unbalanced rotor shaft the user has to choose parameters of the rotating body on the panel balancing parameters. In the case of a flexible rotor, it also means that not more than an acceptable magnitude of deflection occurs in the. The objective of balancing is to reduce shaft vibration to a practical minimum. The device also includes a drive, and an angular position indicator. The article contains excerpts from the paper, rotor balancing tutorial by ray kelm, dustin pavelek and walter kelm of kelm. This ensures that balancing is done at the right speed.
Balancing machines and systems according to din iso 19401. A rigid rotor requires to be evenly positioned about its axis so that it may run true. Vary the motor speed, recording the unbalance at each speed. Both measurement procedures are supported perfectly by our measuring units, so that they always arrive at the optimum balancing result in these weight classes.
A rigid rotor can be balanced by making corrections in any two arbitrarily selected planes. The aim of rotor balancing is to achieve satisfactory running when installed on site. Everett presented a two plane balance procedurethat did not use the vibration phase. Koffler has the capability to dynamic balance rotating equipment such as armatures, rotors, and fans up to 20 tons. The only place, which stays accessible for balancing after assembly, is location of compressor impeller tch 2. Shop balancing methods the methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor. If a rotor is balanced on a low speed balancing machine assuming it is rigid and then in service becomes flexible, then unbalance and thus high vibration, will be the result. You can only balance 2, 3, 4, or 6 tubes at a time on a 6place rotor. The procedure to acquire the required data and balance the rotor is as follows.
The causes of unbalance can be varied with the actual causes depending on manufacturing methods and procedures, repair practices, as well as balance. The goal of rotor balancing is to reduce unbalance enough such that it can operate properly once installed on site. Factory balancing as part of the manufacturing process, most rotors are routinely balanced in a balancing machine. Advanced field balancing concepts kelm engineering. Both the weight and the density of the materials being centrifuged must be balanced.
Traditional methods of amplitude only balancing requirethe use of trial balanceweights of the same size. Thus, the paper is aimed at developing computational and. To improve the balance condition of most high speed flexible rotors, the following procedure is generally followed. Dynamic balancing should not be a substitute for poor machining or other compromise manufacturing practices. Fft at big end of rotor after balancing recorded at the small end and big end of the rotor. One requirement for proper balancing of the rotor is even distribution of rotor mass about the center line for minimal resultant vibration. A rigid rotor can be balanced at the two end planes and will stay in balance when in service. Balancing rigid rotors in the field reliable plant. Ger4212 ge generator rotor design, operational issues. The rotor balancing application is available in both operation modes of the coco. The center of gravity g of the rotor is farther away from the right correction plane r and closer to the left correction plane l, which is localized at a distance c from the near bearing n 1.
Make reference run or calibration run, measuring vibration and phase. Today there is enough reference literature printed during the last 20 years alone on general balancing and balancing of flexible rotors, that could fill a room, ref. Rotating machinery rotor balancing the aim of rotor balancing is to achieve satisfactory running when installed on site. Set up equipment on the rotor as outlined by the balance equipment manufacturer. For dated references, only the edition cited applies. An improved procedure to handle errors of the balancing machine is described in connection with iso 19402. When the rotor comes within tolerance, in tol indication is displayed. In general, long and slender rotors are the most wellsuited for a high speed balance, but any rotor that has the aforementioned repairs or problems can benefit from high speed balancing. Additional components of frequencies may intrude into the balancing procedure and may disturb the phase estimation. Possibility of recalling rotor data fedin previously by giving the rotor code number. Dynamic balancing international balancing standards industrial. A device for the execution of the procedure comprises a balancing machine with at least one tunable support for accommodation of a rotor to be investigated. Summary of rotating machinery rotor balancing lifetime. Mechanical vibration balancing guidance on the use and.
The impact of shop balance technique is most important when the rotor is relatively flexible andor long as is common with most turbomachinery. These balancing procedures usually involve commercial balancing machines based on either the soft hearing or the hard bearing support concept. Single plane and multiplane rotor balancing using only. Hp turbine final balancing after overspeed test at 120% balancing plane rpm balancing weight gr.
The article contains excerpts from the paper, rotor balancing tutorial by ray kelm, dustin pavelek. Thirty years ago it was primarily still part of the skilled trade and was often obscured. Correlation procedure and device for rotor balancing carl. In general, there are two categories of research on dynamic balance technology.
Using computer modeling and artificial neural networks for. Balance rotor and containers the most common cause of centrifuge accidents is user error, especially involving imbalanced rotors. It involves high demands in terms of measurement and systemtechnical requirements as the state of unbalance changes with these types of rotors with increasing speed. The technical definition of a rigid rotor is a rotor that operates 30% or more below its resonant speed. All centrifuge runs must have at least two samples and cannot have only one open space in the rotor. This limit is established in general by the capabilities of shop balance machines. Time wave at small end of rotor after balancing figure 9. Practically, rotors that operate above their first critical, but. In the manufacturing process, if proper care is taken to ensure that castings are sound and machining is concentric, then it follows that the two axis will coincide and the assembled rotor will be in a state of balance. Balancing standard provides generalized grades for which rotor application, mass, and speed can tailored for specific cases. Analysis of balancing of unbalanced rotors and long shafts. Dual plane is used, when the rotor shaft is long balance both sides or when also torque needs to be eliminated.
Rotor balancing is a procedure by which the mass distribution of a rotor or part or module is checked and, if necessary, adjusted to ensure the unbalance tolerance is met. May 28, 2017 the methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor. Lowspeed balancing is only appropriate for rigid rotors. Rotor balancing crystal instruments leading innovation in. A device that holds and spins the rotor while you balance it. This paper will eliminate this requirement and give both. A flexible rotor will require multiplane balancing. Jan 29, 1985 the procedure also includes the method of determining the corrections to be made in the correction planes. Purpose this bulletin is intended as a guide to aid plant maintenance personnel in balancing large rotating machinery.
Balancing of rotors, summary for new built rotors always use high speed balancing for existing rotors low speed balancing is technical and financial the bttbest to perform keeppp a close look to the complete balancing process follow the correct balancing procedure check always with the influence coefficients the residual. Zachwieja, dynamic balancing of rotors with manual balancers. Piedmont chapter vibration institute training symposium 10 may, 2012 field balancing of rotating machinery. In general, the larger the rotor mass, the greater the permissible residual unbalance. The objective was to apply the theory of rotor balancing, gain skills on rotor balancing and get to know how to operate the balancing machine. In most cases the rotor unbalance is the major problem of vibration, it is related to the first order rotational frequency. A balancing report is issued and stored as a reference in our database, along with the serial number of the turbocharger. Unit 6 introduction to balancing balancing structure 6.
Hence, vertical belt drive nearer to the bearing is mooted. If a rotor is balanced on a low speed balancing machine assuming it is rigid and then in service becomes flexible, then unbalance, and thus high vibration, will be the result. Pasio 5 series the perfect solution for small and miniature rotors. Rotating machinery rotor balancing lifetime reliability. A centrifugal balancing machine that furnishes information for performing twoplane balancing. Therefore, after working on rotor blades and in new wind turbines, the balancing grade should be checked and, if necessary, improved. Mechanical vibration methods and criteria for the mechanical balancing of flexible rotors see other formats disclosure to promote the right to information whereas the parliament of india has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities. The report can include itemssuch as company logos and relevant calculationsand the instrument will input the balancing. At present, the problem of balancing of rotor is broadly classified into.
Finally, a comparison of various balance quality grades is made with milstd1671 and api balance limits. The data is used in a balancing program for calculating the required balancing weight and position for attaching a balancing mass to the rotor. The balancing may involve individual balancing of all the components and a final balance of the assembly. Iso standards classifies rotor in accordance with their balancing requirements and establishes methods of assessment of residual unbalance. Introduction the international standards organization, iso, published standard 19401 balance quality requirements of rigid rotors, which has been. Turbine rotors that have had significant blade repairs. Fft at small end of rotor after balancing figure 7. Inspect the rotor for signs of corrosion or cracking before using. If found, do not use the rotor, and inform the employee responsible for the centrifuge of the problem.
A procedure by which the mass distribution of a rotor is checked and, if necessary, adjusted in order to ensure that the vibration of the journals andor forces on the bearings at a frequency corresponding to operating speed are within specified limits. Pdf static and dynamic balancing of helicopter tail rotor. The rotor is initially rotated without any trial mass t o measure the initial vibration x. Factory balancing the best start in life the balancing process itself is a skill that requires not only knowhow but a lot of experience as well. The international standards organisation iso publishes several standards which are the global benchmark for industrial balancing. Rotors that have had their journals, couplings or fits machined. This means the rotor balancing application runs as a standalone operation or as part of a routine maintenance program. Highspeed balancing balancing shaftelastic rotors is a specially demanding task. General centrifuge safety university of british columbia. The same procedure applies to second balancer disks. After balancing probe point amplitude mms phase deg. Such a rotor does not impart any vibratory force or motion to its bearings as a result of centrifugal forces. Installation first attach two accelerometers, one near each of the bearings of the rotor being balanced, to mea sure vibration.
Swinging bucket rotors need special attention to ensure that they are correctly mounted. The methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor. Determination of balancing quality limits page 4 of 7 ali m. Dynamic balancing of rotating machinery experiment technical. The unique and ideal condition of a rotor when it has neither static nor dynamic unbalance.
A procedure by which the mass distribution of a rotor is checked and, if necessary, adjusted in order to ensure. The trial mass procedure for a single plane balancing can be listed as below. Never operate the rotor unless it is symmetrically loaded and balanced. Unbalance will create high vibrations causing material defects and reducing lifetime of a material. The procedure of adding masses can be repeated several times for various arrangements push the recount button. Assure that any keyways are fitted with half keys in accordance with iso 8821 unless two keys are located at the same axial position and are 180. It means no more than an acceptable magnitude of vibration is caused by the unbalance remaining in the rotor. Single plane and multiplane rotor balancing using only amplitude. Proper balancing will improve sample separation and will extend the life of the centrifuge. The rotor weighs 1800 pounds and the weight can be added to the rotor at a radius of 6 inches. Balance quality requirements of rigid rotors ird balancing. Balancing balanced rotors are essential for most kinds of rotating machinery.
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