Rieger, verbatim the need for flexible rotor balancing procedures emerged in the post world war 2 period, due largely to the rapid increase in the size of the rotating equipment used in the power generation. Application notes static and dynamic balancing of rigid. The user should evaluate his rotors, the balancing speeds, and the unbalance correction methods used to. With the machine in operation, locate and measure the point of highest vibration on a bearing. Balance quality requirements for rotors in a constant rigid state. The unique and ideal condition of a rotor when it has neither static nor dynamic unbalance. 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. 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. To perform a fourrun balancing procedure, one only needs a means to measure vibration amplitude and use polar graph paper. A rotor is said to be rigid when the flexure of the. Rotor balancing methods and instrumentation springerlink. Pdf several methods attempting rotor balancing without trial runs have been published in the past.
Advanced field balancing concepts kelm engineering. Everett presented a two plane balance procedurethat did not use the vibration phase. 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. We must establish balancing tolerances that are economically feasible and still low enough to provide satisfactory operation. Dynamic balancing of rotating machinery in the field. An improved procedure to handle errors of the balancing machine is described in connection with iso 19402. Thirty years ago it was primarily still part of the skilled trade and was often obscured. This document covers the balancing of rotors with rigid behaviour. Dynamic balancing of a blower impeller for a passenger ship a.
Also, rotors that have higher vibrations from wear will benefit from a lowspeed balance. In recent years, attempts have been made to combine the in. The diagram below shows masses on two rotors in planes b and c. Balance quality requirements of rigid rotors ird balancing. Pdf practical balancing of flexible rotors for power. Prior to joining edi he was an associate mechanical engineer for. Benefits without disassembling the rotor insitu many machines can be balanced which significantly improved vibration levels.
Koffler has the capability to dynamic balance rotating equipment such as armatures, rotors, and fans up to 20 tons. The article contains excerpts from the paper, rotor balancing tutorial by ray kelm, dustin pavelek and walter kelm of kelm engineering presented at the 2016 turbomachinery symposium. Stop the machine and firmly attach a small trial weight to the rotor. The farther apart these corrective planes are, the smaller, in general, may be the corrective weights. Flexible rotor balancing, in general, relies to a great extent on physical insight. Establishing balancing tolerances for rigid rotors it is neither practical nor possible to remove all unbalance of a rotor. The procedure to acquire the required data and balance the rotor is as follows. Rotor balancing crystal instruments leading innovation. This paper concludes with a discussion on generator rotor reliability and its life expectancywhich varies considerably based on the type and configuration of the generator rotor and the man. Piedmont chapter vibration institute training symposium 10.
Ensure that the trial weight is firmly attached to the rotor. Although it is productive to combine balancing tasks into concentrated areas where. Excessive unbalance can cause vibration and stress in the shaft or attached pieces. 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. The aim of rotor balancing is to achieve satisfactory running when installed on site. Ger4212 ge generator rotor design, operational issues. Introduction the international standards organization, iso, published standard 19401 balance quality requirements of rigid rotors, which has been.
Finally, a comparison of various balance quality grades is made with milstd1671 and api balance limits. The only way to know if something has changed is by comparing with prior runout and balance records. Grit blasting a rotor is known to affect rotor balance. Fist volume 22, field balancing large rotating machinery. The balancing force is 180o anticlockwise of this so the balancing mass must be placed at an angle of 208o. Additionally, btis unique ability to combine the aforementioned technologies into. However, these machines require a special calibration procedure for each rotor to be balanced. The technical definition of a rigid rotor is a rotor that operates 30% or more below its resonant speed. Rotor can fail due to excessive speed, causing catastrophic failure of centrifuge, injuring user. This part of iso 21940 presents typical configurations of rotors with flexible behaviour in accordance with their characteristics and balancing requirements, describes balancing procedures, specifies methods of assessment of the final state of balance, and establishes guidelines for balance.
This paper will eliminate this requirement and give both. Calculation enter the six values measured for the two planes into a. Pdf practical balancing of flexible rotors for power generation. Rotor balancing methods may be separated into two categories. 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. Theory of balancing unbalanced masses in the rotating parts create a centrifugal force that causes the unit to vibrate. Balancing is the process of aligning a principal inertia axis with the geometric.
Specification and verification of balance tolerances. Once a field balance has been completed on a machine or similar machine the response data from adding trial weights can be used to calculate future balance corrections using a one shot method no trial weights required. A procedure by which the mass distribution of a rotor is checked and, if necessary, adjusted in order to ensure. The basics of balancing 202 balance technology inc. The program card must be passed through the reader twice since the program. It means no more than an acceptable magnitude of vibration is caused by the unbalance remaining in the rotor. A new method for fieldbalancing of highspeed flexible rotors. Make a note of the fact that this is the speed to which our final results correct balancing weights will apply. Field balancing consists of determining the amplitude size and location around the shaft phase angle of the unbalance and placing weights on the rotor to counter the unbalance.
A rotor can be balanced either by static balancing or by dynamic balancing. Pdf balancing of an experimental rotor without trial runs. Dynamic balancing of a blower impeller for a passenger ship. 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. The easybalance software has a builtin balancing quality calculator for iso, mil, api and special standards, like 4wn and such. 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, in order to promote. Based on experimental data, the potential for damage is proportional to the balancing quality grade. The need to balance a large rotating machine should be evaluated on an individual basis. Several methods attempting rotor balancing without trial runs have been. The incremental rotor balancing procedure turbomachinery. Mechanical balance of impellers for fans section 1. Any cleaning of the rotor in this manner should be done before balancing. A procedure by which the mass distribution of a rotor is checked and, if necessary.
Koffler electrical mechanical located in san leandro, ca. Poor balancing is one of the main causes for premature machine failure. New vector plot 3 on chart shows fan balanced to 10 times below original 5 mils at start of balancing procedure. Balancing of an experimental rotor without trial runs downloads. This part of iso 1940 gives specifications for rotors in a constant. Single plane and multiplane rotor balancing using only. The results were then compared to a theoretical expectation in. The angles refer to the trial weight positions on the rotor relative to an arbitrary. That is, flexible rotor balancing procedures take into account rotor flexibility, while rigid rotor balancing procedures do not. With only a minor break in operation insitu balancing yields a. These generic titles refer to whether or not rotor flexibility is taken into account.
To improve the balance condition of most high speed flexible rotors, the following procedure is generally followed. Rotating machinery rotor balancing lifetime reliability. Lowspeed balancing is only appropriate for rigid rotors. Check for good tachometer reading and collect the balance data with trial.
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 the weight necessary to offset the net imbalance. Always balance the centrifuge tubes by weight, not just by eye, and put the balanced tubes in opposing positions in the rotor. The issue of balancing generator rotors after rework or modifications is also discussed. Dynamic balancing accommodates any cause for imbalance in the entire rotating system. Place trial weights in the locations recommended by balancing instrument. This paper provides a description of the process used for field balancing of a variety of rotors. Enter rotor mass, service speed and desired quality grade, and. Run the machine and record the initial rotor vibration and phase angle. However, all the methods other than 7 required the use of identical trial weights in the balancing procedures. Unit 6 introduction to balancing balancing structure 6. Calculation enter the six values measured for the two planes into a pocket calcula. 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.
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