Professional Development: Reactive, Preventive, Or Predictive
By Steve Wallis
Published in the September 2012 issue of Today’s Facility Manager
While trying to become more efficient, facility managers (fms) may consider the choice of maintenance strategies as an important factor. For most organizations, having a property that is well maintained is crucial to cutting costs, saving time and energy, and most importantly, ensuring occupant comfort.
There are generally three different approaches to maintenance strategies—reactive, preventive, and predictive. Although each strategy has its positive points, the predictive method may be the preferable method for responsible fms.
The traditional method, also known as reactive method, is the most simple and possibly outdated maintenance approach. This strategy abides by the saying, “if it isn’t broke, don’t fix it.”
Systems run without surveillance and are only attended to when they break, at which point technicians repair and/or replace the broken equipment.
Although there is no upfront cost for this kind of program (unlike a preventive maintenance approach), there are many drawbacks inevitably encountered. These include exorbitant expenses for emergency repairs, lack of occupant comfort during unplanned equipment downtime, and shortened equipment life cycle.
In response to improving the traditional method of “running to failure,” many companies have adopted preventive maintenance (PM) approaches. This strategy is time based, where rebuilding and replacing parts is scheduled ahead of time and typically on a quarterly basis.
With a PM strategy, operators determine the life expectancy and the amount of time estimated for certain parts to fail or require modification based on the history of the equipment. For example, the equipment manufacturer may suggest that a piece of equipment could last six months before failing, so twice per year that piece of equipment would get attention.
Through the PM method, there is a reduced occurrence of equipment failure. This results in an estimated 12% to 18% cost savings when compared to a reactive maintenance program, according to the Federal Energy Management Program’s O&M Best Practices Guide. [Source: U.S Department of Energy, Energy Efficiency & Renewable Energy, Operations and Maintenance Best Practices Guide, Release 3.0, Chapter 5: Types of Maintenance Programs.)
While many facilities operate according to the PM strategy, it is still only partially effective. Alterations are made on schedule, so little attention is placed on the actual condition of the piece of equipment.
Due to technology advancements, a better method of maintaining equipment has evolved, called predictive maintenance (PdM). Instead of fms waiting for the system to fail or checking on the system from time to time, PdM uses technology to predict the failure while also fixing it in advance. Simply put, the fundamental difference is that PdM bases “maintenance need on the actual condition of the machine rather than on some preset schedule.” [Source: Operations and Maintenance Best Practices Guide.] Machines are checked at an early point before they become a problem, which reduces the likelihood of the equipment ever failing in the first place.
Many companies tend to shy away from this particular method because of the high upfront costs and the heavy investment in equipment (and employee training necessary to use the equipment properly), but in the long run, this method may pay for itself over time. Advantages include increased operational life of the equipment, decreased costs for parts and labor, better product quality, and improved comfort and safety. The PdM strategy can also result in energy savings (some estimates indicate as much as 8% to 12% of cost savings over the PM strategy. [Source: Operations and Maintenance Best Practices Guide.]
Fms may be wondering how PdM works. The standard technologies for predictive testing and inspections are vibration analysis, infrared thermography, oil (fluid) analysis, electrical analysis, and ultrasonic measurements. Each of these technologies helps detect early flaws in equipment. [Source: “Predictive Testing & Inspection (PT&I) Can Prevent Operational Interruptions,” by Donald Snapp, Whole Building Design Guide, National Institute of Building Sciences.]
Vibration measurements are used primarily to find problems such as rotor unbalance, coupling misalignment, mechanical looseness, and rolling element bearing defects. Through the frequency of vibration and/or frequency patterns, the specific type of defect is detected along with its severity. Fluid measurements accurately identify problems with surfaces in contact with fluids (such as hydraulic and lubricating oil). Ultrasonic measurements detect internal and external leaks in valves, traps, gaskets, and flanges as well as condition assessments of mechanical components; these can include rolling element bearings and reciprocating compressor valves.
In addition, thermography and thermal imaging detect early problems in equipment by taking pictures that represent temperature variations. Images are easy to interpret as cool areas are blue and purple, while hot areas are yellow and red. [Source: “Predictive Testing & Inspection.”]
When technology is constantly advancing, it is important for fms to learn about new methods that are available to help confirm the fact that they are using the most effective approaches. When maintenance “strategies” are unplanned, organizations can experience premature equipment failure, reduction in occupant satisfaction, and higher prices for repairs and equipment replacements.
Saving energy and money is a trend that will always be popular. There’s no better way of doing that than incorporating a winning strategy early in the operational chain of command.
Wallis is the regional director of operations at GSH Group based in Northern New Jersey.
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