Three Major Ways Your Manufactured Rotating Component Can Become Unbalanced
Unbalance in your rotating component is simply defined as the unequal distribution of weight along your rotor. It is a tricky problem that can sneak up on you unexpectedly. But with the proper knowledge, you can keep an eye out for the major causes of unbalance, and be prepared to address them quickly.
Distortion from Stress
Distortion can occur as a direct result of the manufacturing process and is often the result of a part “adjusting” to relieve stress. Manufacturing processes such as drawing, forging, pressing, etc. will yield internal stresses on parts. If stress relief is not built into the manufacturing process, the rotor will eventually distort to adjust to that residual, internal stress.
Change in temperature or uneven temperature distribution can also cause major distortions on a rotating part. Most metals have the capacity to expand when exposed to heat, so when components operate within environments with elevated temperatures, there is the inherent possibility of expansion. If the heat exposure doesn’t happen uniformly over the entire part, certain sections will expand and distortion will occur.
Thermal distortion is a common and natural occurrence with machines that are exposed to (or operate within) elevated temperatures, so components within machines like motors, compressors, turbines, etc should be regularly evaluated for unbalance.
Deposits & Oil Buildup
If a rotating component is involved in any sort of material handling, it is almost inevitable that buildups of deposits will occur. Minerals (like lime), dirt or dust will begin to build up on rotating parts, cause an initial uneven distribution of weight, and vibrations will begin to occur.
Rotating components that are exposed to oil (ie: lubricated compressors) are also highly susceptible to distortion. Oil has the ability to seep deep into components if left unchecked, and the liquid will accumulate until the buildup causes unbalance, vibrations, and sometimes part failure.
(In the case of deposits and build-up, distortion CAN be avoided before unbalance occurs, if there is a stringent maintenance routine and/or inspection process implemented.)