Angular misalignment: early diagnosis saved Ultragaz USD 7,000

March 13, 2024

The use of Dynamox solution contributed to the diagnosis of an angular misalignment in an LPG pump, whose corrective maintenance cost is estimated at USD 7,000. Check out details of this case:

Seeking significant gains in operational reliability and efficiency, Ultragaz relied on the Dynamox solution for monitoring its assets. The selected assets were: Liquefied Petroleum Gas (LPG) pumps and compressors, as well as air compressors, critical equipment for the production process. A few months later, the solution contributed to the detection of an angular misalignment in the LPG pump.

The goal was to implement condition-based predictive maintenance (CBM) on critical assets. In them, the necessary interventions were based on the machine’s uptime, following the principles of preventive maintenance. The pilot project began in March 2023. In it, a total of 20 sensors and two gateways were installed at the São José dos Campos production base.

One of the sensorized assets was the KSB Multi-Tec 65/3 pump, with an estimated corrective maintenance value of USD 7,000. Furthermore, its shutdown leads to loss of production line availability, thus being a critical asset. In it, then, four HF+ sensors were installed: two on the drive motor and two on the pump itself. In both cases, one sensor was placed on the bearing on the coupled side (CS) and one sensor on the bearing on the opposite side to the coupled one (OCS). As illustrated:

KSB Multi-Tec 65/3 pump Sensorized

angular misalignment - LPG pump
Sensors installed on the motor and LPG pump set. Source: Ultragaz

In September 2023, six months after installation, the overall vibration levels of the pump reached levels that triggered the “alert A2”, pre-configured in the Web Platform according to the ideal operating characteristics of the asset. When analyzing the RMS velocity history, technicians found that the asset exhibited vibration in the horizontal axis exceeding the configured alert level A1 (yellow/caution) of 5 mm/s, surpassing at various times the level 2 of alert (red/critical) of 7 mm/s, as shown in the graph:

RMS Velocity

Angular misalignment: RMS velocity
Global vibration levels in RMS velocity (mm/s) on the coupled side of the LPG pump before intervention. Source: Ultragaz

Upon analyzing the vibration spectrum, a component in the axial direction and another in the horizontal direction with high amplitudes at 1x the equipment rotation were identified, followed by another component present at 2x the equipment rotation (second harmonic), and a third component close to 3x the equipment rotation (third harmonic). In the graph presented below, the motor rotation and its first harmonics are highlighted in gray:

Vibration spectrum pump

Angular misalignment - vibration spectrum
Vibration spectrum of the LPG pump motor, coupled side. Source: Ultragaz

The set of characteristics led to the conclusion that the failure was an angular misalignment in the coupling between the motor and the LPG pump, as we can observe in the illustration below:

Angular misalignment spectrum

Angular misalignment - representation
Typical spectrum of angular misalignment. Source: Dynamox

Following the diagnosis, the team performed the alignment of the asset, which was not perfect due to the limitations of the equipment’s mounting structure. Nevertheless, there was a significant improvement in vibration levels, causing the asset to operate below critical alert levels, as shown in the figure below:

Vibration levels before and after intervention

Global vibration levels on the coupled side of the LPG pump before and after alignment intervention. Source: Ultragaz

Early detection prevented the worsening of the problem and increased the equipment’s lifespan. It was the first step towards implementing predictive maintenance techniques where, until then, actions were almost exclusively preventive or corrective.

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