Augury specifies two types of Looseness in their fault cards: Structural Mechanical Looseness and Rotating Mechanical Looseness.
Whenever someone reads the word “Looseness” in a fault card, their mind usually immediately thinks about loose bolts on the machine. However, that kind of problem is actually covered under a different Augury fault type called Structural Mechanical Looseness and is highlighted in this article. It identifies Structural Looseness as excessive movement or play between Structural components, i.e. normally stationary parts.
Rotating Mechanical Looseness is specific to looseness on rotating parts of the machine, or an interaction between a rotating part and a stationary part. An easy example is looseness in the bearings. Rotating Mechanical Looseness can be caused by severe bearing wear (looseness inside the bearing), but it can also be caused by looseness between the shaft and bearing, or between the bearing and housing.
Above: Mobius Institute (https://www.youtube.com/watch?v=dUXtBfxcpn0)
Rotating Mechanical Looseness can be easily confused with severe Misalignment because they often present the same vibration signature. However, if you break down these two faults, you might find they can be more similar than you think. For an example of severe Misalignment, one of the causes can be coupling wear, either due to the misaligned shafts, or the worn coupling could be causing the shafts to be naturally out of alignment. This worn coupling is also an example of Rotating Mechanical Looseness, as there is excessive clearance in the rotating parts. This is why Rotating Mechanical Looseness and severe Misalignment caused by a loose/worn coupling both show vibration spectra with heavy harmonics of the shaft speed, because they are essentially the same fault.
Causes for Rotating Mechanical Looseness can be excessive clearances in internal parts, internal parts wear, or incorrect installation. Check the “play” in a component by doing a lift check and measuring displacement, both axially and radially, and see if it is in specification.
The root cause of mechanical looseness can widely vary, but conducting a thorough inspection may reveal where the issue originated. Look for cracks, broken parts, fractures, or evidence of overloaded/warped parts. Look for wear patterns. Listen to the machine to identify where in the machine the problems might exist. Other factors to consider are fatigue, stress, corrosion, erosion, temperature variations, or excessive forces or overloading.
Fixing Rotating Mechanical Looseness early is important to ensuring further damage does not result. Rotating Mechanical Looseness should be inspected as soon as possible, because delay can cause wear on more parts in the machine which would raise the parts and labor costs. Waiting to address Rotating Mechanical Looseness can also cause catastrophic failure, which could affect more machines and processes around the faulty component.
