Precursor monitoring approach for reliability assessment of cooling fans

Abstract

Cooling fans are a critical part of the thermal management capability of commercial and military electronic equipment. Although accelerated testing by increasing operating temperatures has been commonly adopted in order to estimate the reliability of cooling fans in a short time frame, the testing time is usually more than 6 months due to the high reliability of ball bearings today. However, these fans are also prone to fail before 3 years. Prognostics and health management is a potential way to cost effectively and timely find low reliability fans. The first step for prognostics and health management is to identify precursor parameters. This article begins with the identification of precursor parameters. The health of cooling fans was estimated by monitoring three precursor parameters including acoustic noise emission, shaft rotational speed, and current consumption. Then the parameter value changes were compared to the failure criteria described in the IPC-9591 standard.

Failure mechanisms of ball bearings under lightly loaded, non-accelerated usage conditions

“…Considering the MTTF of 38.4 hours (tests no. [4][5][6][7][8][9], the maximum evaporation loss will not exceed 0.9%, and so the effect on bearing degradation is negligible. Another possible mechanism was oil leakage.…”

“…Another three tests (no. [4][5][6] were terminated at the moment of failure. The last three tests (no.…”

“…Examples of air cooled applications include power electronics, telecommunications equipment, and consumer electronics [2,3]. The key failure site in air moving devices is the bearings [4][5][6][7]. In small form-factor applications, such as cooling fans in computers, miniature ball bearings are used to provide a long life and low noise.…”

A root cause analysis and a risk evaluation of PV balance of system failures

“…For instance the IPC-9591 standard [36] specified six symptoms for cooling fans' failures in the field: shaft rotational speed reduction, current consumption increase, loud noise, incorrect or erratic operation of electronic interface, visible cracking of the structure, and visible leakage of lubricants. On the other side, the DC link capacitor symptoms of failures can be detected through RF noise during operation and dissipation factor tests during maintenances besides ESR monitoring during its operation.…”

Health Assessment of Cooling Fan Bearings Using Wavelet-Based Filtering

“…However, the literature on fan bearing health assessment is limited. The Center for Advanced Life Cycle Engineering (CALCE) at the University of Maryland, has conducted research on fan bearings, including fan bearing fault identification [3], a physics-of-failure approach for fan PHM [26], a precursor monitoring approach for cooling fans [27], and fan bearing degradation using acoustic emission [28]. This paper proposes a new health indicator for fan bearing degradation assessment.…”