Field balancing of rotor blades applications maintworld. Unlike steam turbines, in which the casing is quite substantial, the w501 series of gas turbines have significant casing motion present in the operating speed range. Latham, new york prepared for lewis research center under contract nas318520 national aeronautics and space administration scientific and. However, rigid rotor balancing methods are, in general, not effective for balancing flexible rotors.
Dynamic balancing is an important way to solve these problems. The diagram below shows masses on two rotors in planes b and c. To learn a simple, practical method of dynamic balancing that can be used in the field and appreciate its. Portable field balancing instrumentation system for on site, inplace balancing of all types of rotors the instumentation is manufactured, supported and serviced in usa and covered by a 10 year limited warranty. Field balancing of rotors, machines and fans is common practice in machine and system engineering. For rotors operating above 3600 some suggest that a calculation yielding 5 % of the rotors weight should be used as an initial trial weight. Products and services adaptive alignment uses singlelaser technology and active situational intelligence to adapt to the asset, the situation, and the maintenance team. Teach special balancing techniques required on overhung rotors. A rotor is considered rigid if it shows no flexure throughout its operating speeds. Optimized field balancing using model based balancing mbb. Greater emphasis is presented in this tutorial on field balancing, which applies to balance correction in situ on rotating machinery and similarly applies to methods. Madyn 2000 for rotor dynamics by delta js 1,599 views. This process can easily prevent expensive repairs where rotors have to be removed and sent to a shop for shop balancing.
From the graph, the magnitude unbalance reduced linearly when the balancing mass was applied. Field balancing technicians have adapted their own guidelines or rules of thumb that apply when considering whether to perform single or two plane balancing. Vibration gennerations mechanismsld bal fie ancing of. In contrast, field balancing involves using vibration measurements on fully assembled machines that are usually in their final service location, and adding field corrections weights to improve the machine vibration at bearing housings or other locations. The technique of balancing in place is referred to as field balancing and it offers some distinct advantages including. Dynamic balancing of rotating machinery in the field. The best method of balancing tested by the authors in balance facility, which also gives the result of greatly minimizing, if not eliminating the need for subsequent balancing in the field after rotors are coupled, is based on the experimental method done by zorzi. Usually it suggests that if the diameter of the rotor is greater than 4 times the width, perform single plane balancing.
Field balancing most rotating components are balanced during the manufacturing process to include balance corrections of individual comp onents hubs, impellers, etc. A flexible rotor may be nearly perfectly balanced in the shop at low speeds in the balancing machine, but perform poorly when operated in the field environment. Benefits without disassembling the rotor insitu many machines can be balanced which significantly improved vibration levels. It means no more than an acceptable magnitude of vibration is caused by the unbalance remaining in the rotor. Zachwieja, dynamic balancing of rotors with manual balancers 61 balancing disks are maintained in a specific position by a selflocking gear and a stepper motors holding torque. However, the traditional balancing methods, using rotor displacement to estimate a rotors unbalance, requiring several trialruns, are neither precise nor efficient. Over time, various balancing methods have been defined and developed 16. A new method for fieldbalancing of highspeed flexible rotors without trial weights y. The balancing procedure to flexible rotors is more complicated, because of the elastic deflections of the rotor. In recent years, various field balancing methods have been developed. Rotating machinery rotor balancing the aim of rotor balancing is to achieve satisfactory running when installed on site. Precision balancing reduces maintenance costs and increases the life of rotating equipment. Rotating machinery rotor balancing lifetime reliability. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the ambrotor system.
Poor balancing is one of the main causes for premature machine failure. Fist volume 22, field balancing large rotating machinery. The process of reducing the vibration level of a rotating assembly after all the rotating components, such as an impeller or propeller, motor armature or rotor assembly, or bearings and pulleys, are assembled to their. Advantages of field balancing many balance problems can be corrected in the field by adding correction weights to the rotor. Before attempting to field balance a rotor, follow these basic steps. Each correction weight is located in one of the arbitrary chosen radial reference planes on the rotor. Field balancing and harmonic vibration suppression in.
Unfortunately, in practice, the use of rigid rotor balancing methods with flexible rotors is not unusual. Hot spot stability analysis with the rotor dynamics software madyn 2000 duration. Balancing techniques for highspeed flexible rotors a. They are the amount and position of the two correction weights required to balance the rotor. Field balancing of rotating machinery vibration institute. The resulting imbalance forces lead to a vibration of the rotor train with single rotational frequency. During planned or unplanned maintenance, turbomachinery rotors are typically balanced.
General familiarity with using todays data collectors or portable balancing instruments is also beneficial a variety of such instruments will be demonstrated during interactive class exercises. Precision field balancing minimizes vibration and its harmful affect on bearings, shafts and seals. Costly and timeconsuming disassembly to remove the rotor to a balancing machine is eliminated. Field balancing large rotating machinery fist 009 08022016 new release minor revisions approved 09162016. In the life time of a machine train, rotor balancing usually cannot be avoided to meet vibration criteria which ensure long term integrity of the different components including shafts and bearings typical site balancing. Field balancing made easy with high ease of operation, universal application and field proven accessories, the rotorbalancer.
In the case of a flexible rotor, it also means that not more than an acceptable magnitude of deflection occurs in the. Rotors of almost any size or weight can be balanced in one or two balancing planes, i. Balancing rigid rotors in the field reliable plant. The dynamics of the casing introduces rotorcasing modes which must be taken into.
It was discovered that when a rotor has acceptable eccentricities based on iso 1940, it becomes. Thus, field balancing is a onetime correction suitable for those rotors whose unbalance changes little during operation, such as energystoring flywheels and vacuum pumps. Research article a new method for fieldbalancing of high. Provide and clearly explain todays balancing tolerances. Previous field balancing experience is helpful but is not required prior to attending this seminar. A new method for fieldbalancing of highspeed flexible. According to iso standards, flexible rotors are classified into five groups with different balancing techniques for each, wherein rigid body balancing could be applied to a group of flexible rotors when some special requirements are met. Many flexible rotor balancing methods are suitable for balancing rigid rotors. Flexible rotor balancing is significantly more complex. Field balancing consists of determining the amplitude size and location around the shaft phase angle of the imbalance, then placing weight on the rotor to counter the imbalance. Field balancing measurement of overall vibration frequency analysis runup and rundown curves vibration versus time phase measurement. Piedmont chapter vibration institute training symposium 10.
A rigid rotor typically operates at a maximum running speed that is below 70% of what is called its first critical frequency, where it shows flexure in. Pryor iii senior technical director pdm solutions, inc. Vibxpert ii balancer is a proven balancer for the effective field balancing of rotors including standard vibration analysis functions. The bunker chamber operates under vacuum which allows balancing of fully bladed rotors under running conditions. On site, inplace field balancer portable field balancing. Thus there is a real need for a direct and scientific method of dynamic balancing in the fieldone simple of application and utilizing readily portable equipment. All rotors are carefully balanced during manufacturing and. There are four variables to be dealt with when balancing any rigid rotor.
The need to balance a large rotating machine should be evaluated on an individual basis. Section 9, improving field balancing of overhung rotors. Balancing procedure an overview sciencedirect topics. Due to these reasons, the field balancing of rotors plays an especially important role. Smartbalancer schenck usa your experts in balancing. Field balancing of magnetically levitated rotors without. Elliotts stateoftheart, highspeed rotor balance facility features computeraided balancing and one of the largest balancing chambers in the world, with an underground bunker and control room. Piedmont chapter vibration institute training symposium 10 may, 2012 field balancing of rotating machinery. The dummy rotors must reproduce the bearing span, weight, center of gravity and dynamic characteristics of the subassembly it replaces and be produced and maintained so that their own contribution to the measured unbalance is minimal. It is worth considering having the rotor blades of a wind turbine balanced, especially since there are wind turbines with relatively strong, low frequency vibrations and because rotor blades can be balanced using oneplane balancing. Rotor balancing methods and instrumentation springerlink. 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. The first assumption that is made in most field balancing work is that we are dealing with a rigid rotor.
These reference planes are usually placed near the support bearings. In dynamic balancing, imbalance on plane 1 was eliminated and virtually, residual unbalance v res. Balancing of flexible rotors with mbb presentation title november 10, 2017 3 why is site balancing needed. Such rotors must be balanced in their own bearings. Teach singleplane and twoplane field balancing techniques using a variety of todays data collectors. Field balancing is the process of balancing a rotor in its own bearings and supporting structure, rather than in a balancing machine. Balancing is performed after acquiring vibration and phase measurements. An algorithm to determine the unbalance vector is based on the influence coefficient matrix, which is determined immediately prior to balancing. Modular assembled engines demand different balancing methods that include the use of simulated engine rotors. Advanced field balancing concepts kelm engineering. Our ability to perform precision balancing in the field saves our clients the downtime, labor and cost of removing the rotor and shipping it to a. Balancing is performed on the complete assembled machine and compensates for the assembly tolerances discussed earlier. Pdf a new method for fieldbalancing of highspeed flexible.
Rigid rotors can be balanced in two planes, with twoplane balancing usually necessary when the length of the rotor exceeds three times its diameter. Over time various balancing methods were defined and developed 16. At present, the problem of balancing of rotor is broadly classified into two major divisions, viz. With only a minor break in operation insitu balancing yields a. Twoplane field balancing of an overhung rigid rotor. Bently nevada 3300xl, 8mm proximity probes at each bearing in xy configuration. The manufacturers tolerances bearing and vibration, the historical. Pdf flexible rotor balancing, in general, relies to a great extent on physical insight into the modal nature of the unbalance response. Unbalance in magnetically levitated rotor mlr can cause undesirable synchronous vibrations and lead to the saturation of the magnetic actuator. Unbalance improving field balancing of overhung rotors.
The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid ambrotor system. Plan view of an imbalanced rotor at the upper guide bearing. Typical of these is the simple diameter to width ratio rule. Most applications will utilize rollingelement bearings, where infinite stiffness is.
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