The balancing disc is mounted on the rotor and corotates with the rotor. With the advancement in control strategies and active vibration control using magnetic bearings, a. Since turbinegenerator rotors are highly stressed struc. Place a trial weight at some location on the rotor, restart the machine, and record vibration amplitudet. 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. Figure 10 turbine generator balance measurement planes.
The thrust developed by the balance piston is small under normal operating conditions, but, under certain conditions of steam flow following valve closure, the piston compensates for loss of the thrust of one of the opposed flow turbine. Highspeed turbine rotor balancing lowers costs and. Rotating machinery rotor balancing lifetime reliability. This survey covers the computational algorithms as well as the physical concepts involved in balancing rotating equipment. A flexible rotor will require multiplane balancing. Facility highspeed rotor balance highspeed balance candidates certain circumstances dictate that a rotor should be highspeed balanced before going into service. The resulting blade assembly is verified on a full rotor static balancing apparatus.
Typical machines, which fit this category, include steam and gas turbines. A balancing report is issued and stored as a reference in our database, along with the serial number of the turbocharger. Shop balancing methods the methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor. The rotor dynamics laboratory at the university of. Plan view of an imbalanced rotor at the upper guide bearing. One of the most important applications of vibration analysis is the solution of balancing problems. A thrust balancing piston in the midshaft packing of an opposed flow reheat steam turbine is supplied by a pipe connected to a downstream turbine stage.
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. The only way to know if something has changed is by comparing with prior runout and balance records. Rotor balancing motor repair best practices duration. The diagram below shows masses on two rotors in planes b and c. By andy ruehs manager, dynamic analysis engineering there are numerous advantages to highspeed balancing of generator and turbine rotors. Background on analysis and balancing earlier 70 mw gas turbinegenerators figure 3 shows a crosssection of the 70 mw gas turbine showing the balance planes. That is, flexible rotor balancing procedures take into account rotor flexibility, while rigid rotor balancing procedures do not. Rotor unbalance is a common cause of synchronous rotor vibration that is detected. Study on online active balancing system of rotating. Finally, a comparison of various balance quality grades is made with milstd1671 and api balance limits. Highspeed turbine rotor balancing was once rare because of the costs and logistical challenges involved in doing it during an outage. Because the bearings restrict this movement, the centrifugal. Rao, first edition 1991, reprint 2005, new delhi, new age international publisher. Balancing a jet engine rotor if the rotor were entirely rigid, then its unbalance could be corrected by spinning the rotor, measuring the cg offset and product of inertia, and then adding a correction weight at each of two planes to compensate for the unbalance.
Static balancing of the cal poly wind turbine rotor citeseerx. Balancing large turbinegenerator rotors ieee xplore. 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. Rec offers rebalancing of your factory or aftermarket flywheel by itsself or with the clutch assembly. Excitations of the rotor train by imbalance forces are a common cause of increased vibrations of. Dynamic analysis and field balancing of 100 mw utility gas. Balance quality requirements of rigid rotors ird balancing. 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. In other words, rotor mass eccentricity limit is a function of speed.
Coupling and balance planes in gas turbinecompressor train. Rotor balancing article pdf available in shock and vibration 556. Pdf practical balancing of flexible rotors for power. As the machine operates, the balance condition of the rotor or components on the rotor can. Application notes static and dynamic balancing of rigid.
An unbalanced rotor, when rotating, wants to revolve around its mass centre axis. The balancing of a wind turbine rotor is a crucial step affecting the machines. Balancing a highspeed rotor on a balancing machine. Static balancing of the cal poly wind turbine rotor. I he balancing procedure tor flexible rotors is more complicated, because of the elastic deflections of the rotor. This measurement is not needed for balancing the rotor, but will be used later as a check on calculations. Should one fail to achieve the minimum residual unbalance of an individual rotor stage for whatever reason during static balancing, a cascade or domino effect in the form of unacceptable residual unbalance may plague the rotor module containing this 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. The correct application of this method ensures the operation of. Teeslots are machined circumferentially in the periphery of the rotor front and rear halfcoupling flanges to permit the weights to be positioned and retained. 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. 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 and walter kelm of kelm.
Thats begun to change as economic options emerge, and. Highspeed balancing hsb of generator and turbine rotors offers a number of advantages. At turbine efficiency, we use a schenck approved rotor balancing machine. Accuracy of balancing balancing to the achievable limit is uneconomical specific unbalance e. Smooth operation through the entire speed range up to overspeed. Insitu balancing is the process of balancing a rotor in its own bearings and. An unbalanced propeller, rotor or driveshaft will cause vibration and stress in. Any cleaning of the rotor in this manner should be done before balancing. The following table gives the balancing grade for various types of rotors. Responsible operators ship these rotors to elliott for highspeed balance and verification. 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. Large turbinegenerators have proven to be very difficult to field balance with the.
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. Turbine runners and pump impellers are usually twoplane balanced before. Abstract rotor balancing needs to be reexamined in the present days context. These generic titles refer to whether or not rotor flexibility is taken into account.
This limit is established in general by the capabilities of shop balance machines. Rotor balancing methods and instrumentation springerlink. Shaft vibration and unbalance limits too stringent for. Balancing the wind turbine blades takes some patience. I would like to explain some basic theory so you have an understanding of how the balancing works. To improve the balance condition of most high speed flexible rotors, the following. Fist volume 22, field balancing large rotating machinery. Before a turbine shaft is stopped to add correction masses or establish phase. The methods employed in shop balancing can have a profound impact on the resulting balance condition of the rotor.
To calculate the balancing tolerances, the following formula can be used. Ny nasa contractor report 2975 balancing techniques for highspeed flexible rotors a. The incremental rotor balancing procedure turbomachinery. Reduce vibration, minimise component fatigue and improve passenger comfort. Depending on the rotor features and your process needs, these lowercost balancing machines may be used for universal applications including armatures, precision spindles, shafts, pump impellers, blowers, fans. Pdf practical balancing of flexible rotors for power generation. A rigid rotor can be balanced at the two end planes and will stay in balance when in service. The impact of shop balance technique is most important when the rotor is relatively flexible andor long as is common with most turbomachinery. 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. This procedure is performed by balancing the flywheel clutch assembly on its own axis. Typical machines, which fit this category, include steam and gas turbines, multistage centrifugal pumps, compressors and paper.
Without a good understanding, it is difficult to correctly balance the blades. 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. 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. The rotor must be perfectly balanced or else vibration at high speeds can destroy the rotor. Problem rotors with persistent vibration issues repaired or rebladed rotors. 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. Grit blasting a rotor is known to affect rotor balance. Rotor balancing methods may be separated into two categories. A method for lowspeed stepbystep balancing is proposed and implemented by the rotor manufacturer. The ability to access optimal weight planes, which are not normally accessible during operation in the machine. Rotor balancing crystal instruments leading innovation. The problem of balancing a flexible highspeed rotor on a bmseries balancing machine is addressed. Latham, new york prepared for lewis research center under contract nas318520.
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