When discussing rotor equipment in general, such components can be classified by whether they are rigid or flexible. Knowing this is crucial as it will affect the general balancing of a system. Rigid rotors are capable of being balanced at lower speeds, relying on centrifugal force for determining if there is an uneven distribution of mass. Meanwhile,
flexible rotors are deflected outward from the assembly’s rotational axis, and increases in operational speed will cause the center of rotation to become more distant from the rotational axis. While a rigid rotor may be balanced while operating at slow speeds, flexible rotors should only be balanced in stages where adjustments are made during low speed operations with slow increases.
During unbalanced conditions in both flexible and rigid rotor assemblies, a number of detrimental effects can occur, ranging from minor inefficiencies to outright damage. With vibration, more energy may be expended by a system, and the forces and loads resulting from such issues will cause a more rapid increase of wear to rotor parts. As other components such as bearings and mountings may be affected as well, unbalance can quickly cause hazards.
If vibration becomes excessive, noise will greatly increase as the structural integrity of the assembly degrades. The structural housing,
bearings, and mounting components are often the hardest hit with stress, and premature wear can occur to such components. Once structural integrity is lost due to the loosening of fasteners, stability will drop. This can even begin to spread to various piping, cabling, and
electrical connections, eventually presenting hazards to surrounding individuals and systems.
Before one can address unbalance, it is crucial to understand that there are three forms of unbalance that may occur. Static unbalance is caused when the mass axis is displaced parallel to the shaft axis, and this type of unbalance is often combated in a single axial plane. Couple unbalance, meanwhile, is when the mass axis intersects the running axis. To remedy this issue, corrections are made in two axial planes. The last form of unbalance is dynamic unbalance, that of which results from a combination of static and couple unbalance issues as a result of the mass axis not intersecting with the rotational axis. Similar to couple unbalance issues, dynamic unbalance may be remedied by correcting balance across two axial planes.
When initiating rotor balancing procedures with a
rotor balancing kit, one should first begin with vibration and phase measurements. Once a vibration analysis is finalized, radial and axial vibration readings are taken. Then, the assembly should be fully cleaned and all loose items should be removed. With the use of trial weights, trial runs can be conducted while adding correction runs. Then, the trim run can be conducted with trim weight corrections as necessary. For single plane procedures, no more than two trim runs should have to be made for a correction. In such cases, the procedure should be repeated. This is the same for many two-plane procedures as well as two trim runs should be suitable for a balance job.
In the case that procedures are carried out and the rotor is still unbalanced, there are some issues that may be occurring. These include
thermal sensitivity, rotor erosion, material buildup, interfering resonances, speed changes, or loose rotor parts. When you are in need of a rotor balancing fan assembly, rotor balancing assembly components, rotor balancing parts, or other various items for your rotor assembly, there is no better alternative to ASAP AOG.
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