Picking up on strange noises

Editor's note: Although the term "reliability-centered maintenance" (RCM) may be unfamiliar to some, chances are that many facilities managers are already using several asset-management tools integral to this concept and well on their way to a complete RCM strategy without yet realizing it. In this monthly three-part series, members of the American Society for Health Care Engineering will explore common tools used in health care facilities today and how they play a role in RCM.

Upon entry to any mechanical room or central plant, a well-trained ear can immediately pick up on unfamiliar sounds — the absence of noise as well as the presence of an alarming noise. These sounds may indicate there has either been a failure or one is very likely about to occur. To rapidly determine the source of the concern, the operator may place a hand on various equipment to sense the absence or presence of vibration. Assessing or monitoring equipment for vibration is an important form of condition-based monitoring (CBM) and also is one of the most well-known maintenance methodologies in which maintenance operations are performed to prevent failure.

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Reliability Asset Management series

As health care facilities professionals continue forward on the journey toward operational excellence, the CBM of noise and vibration is yet another important “tool” within the reliability asset management (RAM) toolbox. When qualified individuals begin to add vibration analysis to rotating or reciprocating devices (e.g., compressors, centrifugal pumps, motors), the maintenance team can reduce risk by first detecting and then preventing unscheduled down time. Vibration analysis, when partnered within an effective asset management strategy, can effectively provide insight into a full spectrum of equipment faults.

The main goal of any effective asset management program is to aid health care facilities professionals with the optimization of maintenance resources. By introducing CBM, the existing program is enhanced because maintenance work is performed only when needed. Similar to performing visual inspections, vibration analysis is described as a nondestructive testing (NDT) strategy. When NDT is combined with performance data, the sensory skills of the maintenance team are enhanced. By adding technologies, operators are taking a step beyond visual inspections and gaining a clear understanding of the equipment’s true operational health.

As equipment operates throughout its useful life, signs of failure will eventually begin to manifest. When warning signs and/or symptoms are detectable, the equipment’s lifecycle has reached the point of potential failure. Potential failure symptoms can vary and are detectable by different methods. Some of the symptoms include heat, vibration and/or cracking. Once equipment has reached potential failure, it is nearing end-of-life and will eventually be unable to perform a required function and, therefore, reach the point of functional failure.

For example, a moving piece will degrade and start to fall out of alignment, which will result in an increased amount of noise and/or vibration. When the amount of vibration crosses a set limit, action is required. However, if the symptom(s) of potential failure are not acknowledged and mitigated, the piece of equipment will continue to trend toward the point of functional failure. Ideally, the duration between the potential failure and functional failure is long enough to provide the maintenance team with enough time to plan and perform the appropriate maintenance task(s).

Whether starting up equipment for the first time and/or attempting to keep the existing equipment operational, creating a baseline is critical when applying CBM techniques to a maintenance program. Ideally, prior to normal operation, all rotating equipment is tested using vibration analysis to obtain a baseline. Even if the equipment is existing, the readings can be compared to the manufacturer’s criteria to determine if the equipment is operating within the published tolerance levels and/or specifications.

Accomplishing this can be achieved by using a portable handheld meter or installing a permanent sensor to measure the vibration of equipment. Whether the data is collected on a set cadence or continuously, the recorded readings will provide the needed baseline. Defining the baseline or “normal operation” creates a benchmark to begin measuring against. Thus, the meter or sensor can signal an “alarm” condition when there is a change of status and when the abnormal vibration crosses a set limit. By comparing the current performance with the baseline, repairs or replacement can be performed at a time of convenience. Thus, the operator can leverage this information to determine when intervention is required. CBM aids in making it straightforward to achieve this objective. Condition monitoring is the process of establishing the state (condition) of an asset by monitoring specific operating parameters of that equipment. It aims to identify significant changes or deviations that are typically indicative of a developing fault.

Even though vibration analysis sounds complicated, the fundamentals are rooted in the use of an accelerometer to measure vibration. In the same manner as a magnehelic reading is used to determine the pressure differential across an air handler’s filter bank, an accelerometer is held against or attached to a piece of equipment to determine the amount of vibration as well as the frequency the equipment is producing. When analyzed, the vibration analysis can be used to determine the overall health of the equipment as well as identify impending problems such as lubrication issues, misalignment, looseness, balance issues, etc.

Given the ever-accelerating speed of change and the numerous known factors impacting health care facility operations, the ability to make informed decisions is being tested now more than ever before. To meet these challenges, the American Society for Health Care Engineering’s Reliability Asset Management Task Force has committed to evolving the outdated “just-in-case” calendar-based maintenance strategy toward one focused on reducing risk and based on evidence of need. This means applying CBM to target failure modes and allowing early identification of defects.