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Predictive Maintenance

Success in today’s highly competitive building management business depends upon high tenant occupancy, controlled expenses, and most importantly – uninterrupted and trouble free operation.  That means no unexpected shutdowns, no major equipment and service failures, and no high cost emergency repairs.

Contrasting most building management and engineering practices prior to 1990, today’s successful commercial property can no longer afford to follow the “run to failure” mode of operation for its mechanical equipment.  Computer centers, hospitals, financial interests, and internet related businesses all demand virtually uninterrupted power, cooling and other HVAC services.  Yet, industry wide reductions of maintenance manpower have reduced or greatly limited the ability to perform “preventative maintenance” anywhere other than at the most well recognized problem areas.

With the conflicting demand to provide more reliable building services at lower cost and with limited personnel, many property managers and plant engineers have turned to “predictive maintenance” programs as the answer.

• Preventative vs. Predictive

Unlike preventative maintenance, which sets a fixed and often arbitrary interval for performing regular maintenance and corrective tasks, necessary or not – predictive maintenance, utilizing a variety of nondestructive testing techniques (NDT), and can identify only those specific pieces of equipment in need of service.  In most cases, NDT can provide months and even years of advance notice that a corrosion problem exists, or is developing.

Nondestructive testing also serves as a valuable property evaluation tool for long term capitol planning and improvement, as well as for property acquisitions.  Such testing becomes invaluable when applied to older properties relying upon original electrical and piping services, and especially where the prior maintenance history is unknown, or is suspected to have been deficient.

With only a limited amount of engineering investigation typically performed prior to most purchases, it has become common for property owners and operators to learn of serious mechanical or electrical flaws only after the property has changed hands.

• Other Testing Mechanisms Flawed

Corrosion coupons, the primary method of corrosion monitoring employed today, are so inaccurate as to be virtually worthless in most applications.  Against evidence of rust deposits in pump strainers, cooling tower pans, and chiller heads, constricted pipe, thread leaks, and even piping failures, corrosion coupons are still blindly believed to report the rate of corrosion activity occurring within the piping system.  For a variety of reasons which we have well documented during our more than 30 years of experience in this field, a corrosion coupon produces a measurement representing only “the potential corrosivity of a fluid against new pipe steel.”  Nothing more.

This is, of course, not the understanding of those property managers and building engineers receiving regular corrosion coupon reports, and assuming that such typically low corrosion rates reflect the actual wall loss occurring within their piping system(s).  In fact, reported corrosion coupon rates frequently have almost nothing to do with the rate of wall loss occurring at the pipe, and are typically in error by at least 10 times or more.  Massive failures in accuracy, examples where corrosion coupons reported 0.3 MPY corrosion rates and where actual measured wall loss through ultrasound 100 times higher, helps illustrate the threat of relying upon a testing method so inherently inaccurate.

In many examples, the almost total trust and reliance on corrosion coupons to define corrosion activity has resulted in years of excessive corrosion losses resulting in near total and total piping failure.  Examples of such failures are prominently documented on this website.

• Pipe Life Often A Question

With the growing age of most established properties, often at 50-70 years or more, building owners and plant operators are also beginning to question the remaining service life of their main HVAC piping systems.  This concern surprisingly exists at many newer buildings and renovations which, for a variety of reasons, are finding themselves faced with advanced corrosion problems and premature piping failures rarely seen decades ago.

Unlike older properties, which were constructed typically using extra heavy or schedule 80 steel pipe, commercial properties built within the past 25-30 years have used much thinner materials.  During this same time, hours of service have increased, the use of lower quality foreign and domestic steel pipe is widespread, and government regulations and restrictions have reduced the effectiveness of both corrosion inhibitors and microbiological controls – all contributing to far less service expectation.

• Ultrasonic Testing Ideal

Considered more of a general evaluation method than a predictive maintenance tool, ultrasonic testing (UT) offers the ability to accurately measure pipe wall thickness with the system operating and without any service disruption.  Combined with thorough data analysis comparing original, current, and lowest permissible wall thickness, UT will provide the property owner or plant operator with a clear understanding of current corrosion conditions and the remaining service life of any piping system.

For a property manager concerned about a recent leak condition, ultrasound will show not only if it was an isolated event or the first occurrence of a system wide problem, but also provide the hard documentation to justify its repair if necessary.

Whether a general concern about a 45 year old condenser water system, suspicions about the quality of one’s water treatment program, a deficient maintenance history, or the more obvious indication of a problem shown by leaks, clogged pipes, and buckets of removed scale, properly performed ultrasonic testing will provide the answers.

• Infrared Testing Well Respected

By far, the most commonly recognized and employed nondestructive or predictive testing tool is the use of infrared thermography (IR) to detect hot spots at electrical panels and equipment.  IR testing not only replaces the older, time consuming preventative maintenance procedure of torquing down all electrical connections and taking amperage readings, but also identifies a variety of other potential electrical problems, previously unaddressed.

Any building operator who has performed IR testing has likely seen the direct benefits of such an annual inspection; most can cite examples of where infrared testing has prevented an imminent fire or electrical meltdown, along with the resulting repair costs and service interruption.

The benefits of IR are so well recognized that many insurance companies now require annual inspection as part of their terms of coverage.

• Vibration Analysis For Rotating Equipment

For rotating equipment, vibration analysis offers the ability to track equipment operation under real time conditions and detect the very slightest defect.  A bearing that has a small developing fault will produce a tell-tale change in the machine’s vibration signature – so will a weight imbalance, shaft misalignment, or literally hundreds of other causes.  Such an ability to identify mechanical problems at this early stage, and before they even reach the point of being able to be detected by infrared testing, defines vibration analysis as the ultimate predictive maintenance tool.

Overall, the benefits of nondestructive testing have been well documented in virtually every commercial and industrial setting.  Whether employed as an annual prediction maintenance tool, or as a means to investigate a specific equipment failure or area of concern, nondestructive testing offers major benefits in savings and increased operations reliability to all management professionals.

© Copyright 2023 – William P. Duncan, CorrView International, LLC