Abstract rotor balancing needs to be reexamined in the present days context. Automatic balancing of rotor bearing systems 217 er fluids are materials that respond to an applied magnetic or electric field with a dramatic change in rheological behavior. This is important since rotors can generally only be balanced using the rigid rotor method. A disk with a known mass unbalance is placed in the middle. Balancing techniques for highspeed flexible rotors ntrs nasa. Zheng explored a novel auto balancing method for a magnetically suspended rotor in a motor driveline system based on synchronous rotating. A rotor system is modeled as a massless, elastic shaft supported by two nonflexible bearings. Dynamic analysis and field balancing of 100 mw utility gas. A correction weight placed at the compressor balance plane would then in turn cause high turbine end vibrations. The incremental rotor balancing procedure turbomachinery. A threemass test rotor with a flattened shaft was designed to evaluate the feasibility and problems of. An exception to the rule, however, presents itself in variable speed machines, which will show increasing vibration with increasing speed. Apr 25, 2015 the problem of balancing a flexible highspeed rotor on a bmseries balancing machine is addressed.
The goal of rotor balancing is to reduce unbalance enough such that it can operate properly once installed on site. Next, through the supporting bearings and through the fluid encircling the rotor unless the rotor operates in vacuum, the rotor lateral vibrations are transmitted to the nonrotating parts of the machine. They are the amount and position of the two correction weights required to balance the rotor. By balancing the rotor assembly, the imbalance condition is either minimized or removed. The international standards organisation iso publishes several standards which are the global benchmark for industrial balancing. Our craftsmen are trained and equipped with modern equipment to complete vibration analysis and dynamic balance your equipment on site or in our shop. With the advancement in control strategies and active vibration control using magnetic bearings, a. Rotating machinery rotor balancing lifetime reliability. Active balancing and vibration control of rotating. Insitu balancing of highspeed rotors 3 experience show, that removal of material by drilling is not sufficiently accurate and that final balancing of rotor as a rigid body on schenck balancing machine is needed. After balancing, the rotor can reach the better class than it was in before balancing. A rotor is balanced if its vibration amplitude is lower than the threshod of 25 micrometers peak topeak n proximty of the first or second critical speed, as established by iso and api2, 3, 11.
An early flexible rotor balancing technique, was based on mode shapes modal method. The rotor system is rotating with a constant rotational speed, see figure 2 figure 2 a jeffcott. Accuracy of balancing balancing to the achievable limit is uneconomical specific unbalance e. Latham, new york prepared for lewis research center under contract nas318520. It is a serious safety risk if a balancing weight is not firmly attached and flies off while running the machine. Specification and verification of balance tolerances, gives specifications for rotors in a constant rigid state according to their. The rotor weighs 1800 pounds and the weight can be added to the rotor at a radius of 6 inches. Rotor balancing crystal instruments leading innovation. Nov 11, 2015 dynamic balancing tools and processes rotor imbalance is usually resolved at a machines startup.
Value of e is in inverse proportion to the maximum working revolution speed n min1 of the rotor, which means that en is a constant value. The aim of balancing is to reduce the amplitude of vibration to a tolerable level, which can be taken to be about 25 mi at the bearing pedestals. Balancing is a process of designing or modifying machinery so that the unbalance is reduced to an acceptable level and if possible eliminated entirely. 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. These include smooth operation, access to optimal weight planes, and verification of the mechanical integrity of the rotor and any assembled components rotors are typically run to 110% overspeed. Vibration literature1 can be obtained for study in more technical detail. 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. Place a trial weight at some location on the rotor, restart the machine, and record vibration amplitudet. Balancing of rotating parts such as rotor assemblies mce. The difference betwee baln stati c ance and dynamic balance is illus trated in fig 1. Nasa contractor report 2975 balancing techniques for 1.
Video training remains available while inperson conferences and training sessions have been suspended. Rotor unbalance is a basic concern in the design and operation of machinery because it is a major cause of excessive vibration. The controversy between modal and influence coefficient methods began. Rao, first edition 1991, reprint 2005, new delhi, new age international publisher. On the circumference of the circle, mark the trial weight positions. This balancing pro cess is often known as dynamic balancing because the unbalance only becomes apparent when the ob ject is rotating.
All rotors are carefully balanced during manufacturing and. Determination of phase and amount of removed material in three balancing planes is relatively complicated. 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. The easiest way to treat this problem is to break it down into a couple of parts. Rotor balancing is a type of analysis that compares the vibration profile with the rotation of a mechanical element to characterize inconsistent weight distribution around the diameter while calculating the amount and position of. That is, flexible rotor balancing procedures take into account rotor flexibility, while rigid rotor balancing procedures do not. Gas turbine balancing runs can be extremely timeconsuming. This allows for the rotor to run smoothly, without undue vibration, hence allows the system to work for extended periods increasing the mtbf mean time between failure. Rotating machinery rotor balancing the aim of rotor balancing is to achieve satisfactory running when installed on site.
There are four variables to be dealt with when balancing any rigid rotor. Dynamic balancing rotors with precision prime machine, inc. The problem of balancing a flexible highspeed rotor on a bmseries balancing machine is addressed. If it is so what is the acceptable speed limit for doing the dynamic balance of 3000 rpm rated motor rotor. Precautions and safeguards during insitu balancing balancing is the process by which the mass distribution of a rotor is checked and, if necessary, adjusted to ensure that the residual unbalance or the vibrations of the journalsbearing supports.
May 28, 2017 the methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor. Nov 14, 1989 in balancing the typical turbine rotor, it is rotated at some speed such as 900 rpm with balancing machines capable of detecting the angle and amount of the unbalance. A survey shiyu zhou and jianjun shi abstractvibration suppression of rotating machinery is an important engineering problem. As always, we can arrange videoconferencing for specific consulting. The paper introduces a dynamic balance method for drumshape gyroscope rotor. These reference planes are usually placed near the support bearings. A method for lowspeed stepbystep balancing is proposed and implemented by the rotor manufacturer. Balancing of rotating masses when a mass moves along a circular path, it experiences a centripetal acceleration and a force is required to produce it. Teeslots are machined circumferentially in the periphery of the rotor front and rear halfcoupling flanges to permit the weights to be positioned and retained. Adapting the operating frequency range the operating speed must be sufficiently away from the critical speed 3.
An equal mass, placed source of vibration in machines with by adding compensating masses to the at an angle of 180 to the unbalanced rotating parts. Dynamic balance analysis of drumshape rotor scientific. The program card must be passed through the reader twice since the. If an infinite gradation of counterweights were available and an infinite number of locations were available, it would be a simple matter to place the appropriate weight. This study introduced a novel liquid transfer active balancing system for the hollow rotors, and compensation mass was performed by balance. Rotating unbalance is the uneven distribution of mass around an axis of rotation. The farther apart these corrective planes are, the smaller, in general, may be the corrective weights. One common practice during shop balancing is to make static corrections near the center of a rotor using the low speed shop balance. A rotor is said to be rigid when the flexure of the rotor caused. Moore demonstrated the practical application of the method to heavy rotating equipment.
The aim of balancing is to reduce the amplitude of vibration to a tolerable level, which can be. Rotor balancing article pdf available in shock and vibration 556. Piedmont chapter vibration institute training symposium 10. Overhung configuration rotor wt 100lb 50lb 50lb rotor wt 100lb 80% 20%. Introduction the international standards organization, iso, published standard 19401 balance quality requirements of rigid rotors, which has been adopted by the american national standards institute, ansi, as s2. A rotor is balanced by placing a cor rection mass of a certain size in a posi tion where it counteracts the unbal ance in the rotor. Automatic balancing of rotorbearing systems 217 er fluids are materials that respond to an applied magnetic or electric field with a dramatic change in rheological behavior. The impact of shop balance technique is most important when the rotor is relatively flexible andor long as is common with most turbomachinery. Reducing unbalance reduces vibration and increases efficiency and life of the rotor and bearings. Formulation of a transfer function between rotor responses on. The correct application of this method ensures the operation of the rotor at a normal vibration level. Analysis of balancing of unbalanced rotors and long shafts. In balancing the typical turbine rotor, it is rotated at some speed such as 900 rpm with balancing machines capable of detecting the angle and amount of the unbalance. In the case of a flexible rotor, it also means that not more than an acceptable magnitude of deflection occurs in the.
Static balancing of the cal poly wind turbine rotor derek simon the balancing of a wind turbine rotor is a crucial step affecting the machines performance, reliability, and safety, as it directly impacts the dynamic loads on the entire structure. Purpose this bulletin is intended as a guide to aid plant maintenance personnel in balancing large rotating machinery. Balancing machines types, classification, and methods. Active balancing and vibration control of rotating machinery. Static balancing of the cal poly wind turbine rotor.
Application notes static and dynamic balancing of rigid. Dynamic balancing of rotating machinery in the field. A rigid rotor can be balanced at the two end planes and will stay in balance when in service. This document covers the balancing of rotors with rigid behaviour. As a minimum, the equipment really should be balanced at operating speed. On the polar graph paper, draw a circle with a radius of 10 mils. These generic titles refer to whether or not rotor flexibility is taken into account. Most often, they represent the lowest modes of the entire machine structure. Finally, a comparison of various balance quality grades is made with milstd1671 and api balance limits. A balancing report is issued and stored as a reference in our database, along with the serial number of the turbocharger.
The diagram below shows masses on two rotors in planes b and c. 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. It means no more than an acceptable magnitude of vibration is caused by the unbalance remaining in the rotor. When balancing such a rotor in a balancing machine, the rotor may be mounted elastically in such a way that it is pivoted to oscillate about some chosen radial axis. Highspeed balancing hsb of generator and turbine rotors offers a number of advantages. A rotating mass, or rotor, is said to be out of balance when its center of mass inertia axis is out of alignment with the center of rotation geometric axis. For rigid rotor that widely applied in gyroscopes, high precision dynamic balance is very important. The methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor. Each correction weight is located in one of the arbitrary chosen radial reference planes on the rotor. After installation on the helicopter, the dynamic balancing of the rotor blades is carried out to bring vibrations within a set limit.
Mechanical parameters here are the buttons to select mode of displaying graphs obtained as results of simulation of unbalanced and balanced rotating body. May 06, 2016 if it is so what is the acceptable speed limit for doing the dynamic balance of 3000 rpm rated motor rotor. The article contains excerpts from the paper, rotor balancing tutorial by ray kelm, dustin pavelek. Method of balancing rotors unitedtechnologies corporation. Rotor balancing methods may be separated into two categories. Internal damping includes hysteresis in the shaft and. Rotor balancing methods and instrumentation springerlink. Advanced field balancing concepts kelm engineering. A simplified method is shown for determining permissible residual unbalance for various rotor classifications. The acceptable capability limit of the facility performing dynamic balancing of a 3000 rpm machine should be roughly in the 45005000 rpm range. If technical conditions allow to stop the rotor for a short period, the disk can be balanced using manual balancers, with a significantly lower cost compared to the. Dynamic balancing of rotating machinery experiment technical. In general, the rotor blades are balanced on ground statically balanced as a set, usually, so as to reduce the deviations caused during manufacturing process.
Power generation high speed rotor balance toshiba america. Static and dynamic balancing using portable measuring equipment by john vaughan foreword 2 many people are needlessly appre hensive of performing their own dy namic balancing procedure. Dynamic balancing tools and processes rotor imbalance is usually resolved at a machines startup. Balancing a highspeed rotor on a balancing machine. Then according to geometrical relation of geometric.
The article contains excerpts from the paper, rotor balancing tutorial by ray kelm, dustin pavelek and walter kelm of kelm. However, in the field, he would place a balance weight on the turbine which in turn would cause high vibrations on the compressor side. A rotor can be balanced either statically or dynamically. Formulation of a transfer function between rotor responses. Unbalance causes a moment which gives the rotor a wobbling movement characteristic of vibration of rotating structures.
Balance quality requirements of rigid rotors ird balancing. The angles refer to the trial weight positions on the rotor relative to an arbitrary zero. Determine the masses to be added on the rotors in planes a and d at radius 40 mm which will produce static and dynamic balance. This measurement is not needed for balancing the rotor, but will be used later as a check on calculations. Ensure that the balancing weights are firmly attached to the rotor. Ny nasa contractor report 2975 balancing techniques for highspeed flexible rotors a. Introduction equations of motion structural analysis case studies references history and scientists history and scientists 7 27 1869 ankine r on the centrifugal force on rotating shafts.
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