Orbit analysis: ideal for vibrating screens

March 8, 2024

Orbit analysis (or orbital analysis) allows observing the trajectories of moving parts of machines during operation. Thus, contributing to the identification of operational deviations or problems in these components.

The use of orbit analysis is highlighted in vibrating screens, but it is applicable to other assets such as turbines, pumps, generators, compressors and others.

What is orbit analysis?

The orbit represents the trajectory of a component described in a 2D plane (X and Y). Thus, offering the possibility to consult the ‘shape’ of the displacement of the monitored point, facilitating the identification of deviations with respect to the expected movement.

Orbit analysis - is an expression of the relative movement between two axes.

Orbit analysis is built from the displacement signal of the monitored point. It is, therefore, an expression of the relative movement between two axes, which is why it is necessary for the acquisition to be done triaxially and simultaneously. If there is a delay in measurement between the axes, this analysis becomes unfeasible.

Orbit Analysis in Vibrating Screens

One of the assets where the use of orbital analysis stands out is vibrating screens. In general, this type of asset can be described by the constitution of three basic components: the sieving mesh (which controls the granularity of the separated material); suspension system (for vibration isolation); and the drive mechanism usually consisting of a motor-coupling-exciter (which induces vibratory motion in the structure).

Screens are essential in raw material classification processes, in addition to being a high-value asset. Therefore, their monitoring is indispensable to detect premature failures that directly impact production and consequently cause significant losses to companies.

Monitoring is primarily done by vibration measurement, which occurs with the aid of sensors and involves measuring the displacement of the springs. On the Dynamox platform, it is possible – based on triaxial and simultaneous data – to construct the orbit graph. This comparative analysis allows the identification of operational deviations between the components of the screen itself, allowing for the configuration of alerts between the right and left sides, as well as between loading and unloading. Do you want to know more about vibrating screen monitoring? Watch (available in Portuguese):

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Moreover, Dynamox has developed a Specialist Dashboard exclusively for vibrating screens due to the complexity of monitoring these assets. Get to know the complete solution!

Orbital Analysis – Failure Diagnosis

Thus, from the orbit, various fault principles that generate the amplification of vibratory signals can be visualized. Among the main faults that the analysis is capable of detecting are:

  • Unbalance: occurs when the rotor’s center of mass is not aligned with the rotation axis. This generates undesirable vibrations and, consequently, premature wear, damage, or machine failure.
  • Misalignment: characterized by the difference in the reference line between the primary machine axis and the load axis. The problem can occur due to linear or angular displacement.
  • Rubbing: occurs when the rotor comes into contact with stationary parts of the bearing. Generally, it arises as a secondary effect of other problems and alters the shape of the orbit.
  • Excessive looseness: caused by structural problems or wear, excessive clearance reduces the ability to absorb dynamic forces, amplifying the vibration from unbalance or misalignment.
  • Oil Whirl: caused by the excitation of the oil film, which slides at different speeds than the shaft rotation. The problem amplifies vibration and may arise due to wear, variations in oil viscosity, and pressure.

How to perform orbital analysis?

Orbit analysis is quite didactic. It allows the analyst to see a representation of movement in space. As in the example:

Orbit analysis - waveform

When there is unbalance or misalignment, for example, there is a deformation of the orbit, which can be lateral displacement, increased amplitude, jumps, discontinuities, flattening, or bulging. Take a look at the image:

orbital analysis - failure example

The orbital analysis is available on the Dynamox platform and the Specialist Dashboard (Dynadash) for vibrating screens, for example. Watch a data reading from Dynadash:

Case Analysis -Vibrating Screens

A very interesting case involving vibrating screens occurred after maintenance. When it returned to operation, analysts noticed a discrepancy in vibration amplitudes between the left and right sides. Through sensitive inspection and magnetic tests, it was found that the right side contained lead inserts, while the original material on the left side was steel.

The metal replacement justified the difference in amplitude, as the densities (and consequently the weights) of the metals are different. This discrepancy was causing an unbalance between the masses, and the screen lost synchronization.

In addition to this fault, others caused by problems in the springs and bearing bearings were also diagnosed on the Dynamox platform. The orbit analysis was a useful way to visualize the movement of the screens and identify each of these faults more accurately.

Are you curious to know more? Watch a summary of these cases told by Vibration Analyst Joel Nunes:

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